1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
23 * Copyright (c) 2019, Joyent, Inc.
24 * Copyright (c) 2011, 2018 by Delphix. All rights reserved.
25 * Copyright (c) 2014 by Saso Kiselkov. All rights reserved.
26 * Copyright 2017 Nexenta Systems, Inc. All rights reserved.
27 * Copyright (c) 2011, 2019, Delphix. All rights reserved.
28 * Copyright (c) 2020, George Amanakis. All rights reserved.
29 * Copyright (c) 2020, The FreeBSD Foundation [1]
30 * Copyright 2024 Bill Sommerfeld <sommerfeld@hamachi.org>
31 *
32 * [1] Portions of this software were developed by Allan Jude
33 * under sponsorship from the FreeBSD Foundation.
34 */
35
36 /*
37 * DVA-based Adjustable Replacement Cache
38 *
39 * While much of the theory of operation used here is
40 * based on the self-tuning, low overhead replacement cache
41 * presented by Megiddo and Modha at FAST 2003, there are some
42 * significant differences:
43 *
44 * 1. The Megiddo and Modha model assumes any page is evictable.
45 * Pages in its cache cannot be "locked" into memory. This makes
46 * the eviction algorithm simple: evict the last page in the list.
47 * This also make the performance characteristics easy to reason
48 * about. Our cache is not so simple. At any given moment, some
49 * subset of the blocks in the cache are un-evictable because we
50 * have handed out a reference to them. Blocks are only evictable
51 * when there are no external references active. This makes
52 * eviction far more problematic: we choose to evict the evictable
53 * blocks that are the "lowest" in the list.
54 *
55 * There are times when it is not possible to evict the requested
56 * space. In these circumstances we are unable to adjust the cache
57 * size. To prevent the cache growing unbounded at these times we
58 * implement a "cache throttle" that slows the flow of new data
59 * into the cache until we can make space available.
60 *
61 * 2. The Megiddo and Modha model assumes a fixed cache size.
62 * Pages are evicted when the cache is full and there is a cache
63 * miss. Our model has a variable sized cache. It grows with
64 * high use, but also tries to react to memory pressure from the
65 * operating system: decreasing its size when system memory is
66 * tight.
67 *
68 * 3. The Megiddo and Modha model assumes a fixed page size. All
69 * elements of the cache are therefore exactly the same size. So
70 * when adjusting the cache size following a cache miss, its simply
71 * a matter of choosing a single page to evict. In our model, we
72 * have variable sized cache blocks (rangeing from 512 bytes to
73 * 128K bytes). We therefore choose a set of blocks to evict to make
74 * space for a cache miss that approximates as closely as possible
75 * the space used by the new block.
76 *
77 * See also: "ARC: A Self-Tuning, Low Overhead Replacement Cache"
78 * by N. Megiddo & D. Modha, FAST 2003
79 */
80
81 /*
82 * The locking model:
83 *
84 * A new reference to a cache buffer can be obtained in two
85 * ways: 1) via a hash table lookup using the DVA as a key,
86 * or 2) via one of the ARC lists. The arc_read() interface
87 * uses method 1, while the internal ARC algorithms for
88 * adjusting the cache use method 2. We therefore provide two
89 * types of locks: 1) the hash table lock array, and 2) the
90 * ARC list locks.
91 *
92 * Buffers do not have their own mutexes, rather they rely on the
93 * hash table mutexes for the bulk of their protection (i.e. most
94 * fields in the arc_buf_hdr_t are protected by these mutexes).
95 *
96 * buf_hash_find() returns the appropriate mutex (held) when it
97 * locates the requested buffer in the hash table. It returns
98 * NULL for the mutex if the buffer was not in the table.
99 *
100 * buf_hash_remove() expects the appropriate hash mutex to be
101 * already held before it is invoked.
102 *
103 * Each ARC state also has a mutex which is used to protect the
104 * buffer list associated with the state. When attempting to
105 * obtain a hash table lock while holding an ARC list lock you
106 * must use: mutex_tryenter() to avoid deadlock. Also note that
107 * the active state mutex must be held before the ghost state mutex.
108 *
109 * Note that the majority of the performance stats are manipulated
110 * with atomic operations.
111 *
112 * The L2ARC uses the l2ad_mtx on each vdev for the following:
113 *
114 * - L2ARC buflist creation
115 * - L2ARC buflist eviction
116 * - L2ARC write completion, which walks L2ARC buflists
117 * - ARC header destruction, as it removes from L2ARC buflists
118 * - ARC header release, as it removes from L2ARC buflists
119 */
120
121 /*
122 * ARC operation:
123 *
124 * Every block that is in the ARC is tracked by an arc_buf_hdr_t structure.
125 * This structure can point either to a block that is still in the cache or to
126 * one that is only accessible in an L2 ARC device, or it can provide
127 * information about a block that was recently evicted. If a block is
128 * only accessible in the L2ARC, then the arc_buf_hdr_t only has enough
129 * information to retrieve it from the L2ARC device. This information is
130 * stored in the l2arc_buf_hdr_t sub-structure of the arc_buf_hdr_t. A block
131 * that is in this state cannot access the data directly.
132 *
133 * Blocks that are actively being referenced or have not been evicted
134 * are cached in the L1ARC. The L1ARC (l1arc_buf_hdr_t) is a structure within
135 * the arc_buf_hdr_t that will point to the data block in memory. A block can
136 * only be read by a consumer if it has an l1arc_buf_hdr_t. The L1ARC
137 * caches data in two ways -- in a list of ARC buffers (arc_buf_t) and
138 * also in the arc_buf_hdr_t's private physical data block pointer (b_pabd).
139 *
140 * The L1ARC's data pointer may or may not be uncompressed. The ARC has the
141 * ability to store the physical data (b_pabd) associated with the DVA of the
142 * arc_buf_hdr_t. Since the b_pabd is a copy of the on-disk physical block,
143 * it will match its on-disk compression characteristics. This behavior can be
144 * disabled by setting 'zfs_compressed_arc_enabled' to B_FALSE. When the
145 * compressed ARC functionality is disabled, the b_pabd will point to an
146 * uncompressed version of the on-disk data.
147 *
148 * Data in the L1ARC is not accessed by consumers of the ARC directly. Each
149 * arc_buf_hdr_t can have multiple ARC buffers (arc_buf_t) which reference it.
150 * Each ARC buffer (arc_buf_t) is being actively accessed by a specific ARC
151 * consumer. The ARC will provide references to this data and will keep it
152 * cached until it is no longer in use. The ARC caches only the L1ARC's physical
153 * data block and will evict any arc_buf_t that is no longer referenced. The
154 * amount of memory consumed by the arc_buf_ts' data buffers can be seen via the
155 * "overhead_size" kstat.
156 *
157 * Depending on the consumer, an arc_buf_t can be requested in uncompressed or
158 * compressed form. The typical case is that consumers will want uncompressed
159 * data, and when that happens a new data buffer is allocated where the data is
160 * decompressed for them to use. Currently the only consumer who wants
161 * compressed arc_buf_t's is "zfs send", when it streams data exactly as it
162 * exists on disk. When this happens, the arc_buf_t's data buffer is shared
163 * with the arc_buf_hdr_t.
164 *
165 * Here is a diagram showing an arc_buf_hdr_t referenced by two arc_buf_t's. The
166 * first one is owned by a compressed send consumer (and therefore references
167 * the same compressed data buffer as the arc_buf_hdr_t) and the second could be
168 * used by any other consumer (and has its own uncompressed copy of the data
169 * buffer).
170 *
171 * arc_buf_hdr_t
172 * +-----------+
173 * | fields |
174 * | common to |
175 * | L1- and |
176 * | L2ARC |
177 * +-----------+
178 * | l2arc_buf_hdr_t
179 * | |
180 * +-----------+
181 * | l1arc_buf_hdr_t
182 * | | arc_buf_t
183 * | b_buf +------------>+-----------+ arc_buf_t
184 * | b_pabd +-+ |b_next +---->+-----------+
185 * +-----------+ | |-----------| |b_next +-->NULL
186 * | |b_comp = T | +-----------+
187 * | |b_data +-+ |b_comp = F |
188 * | +-----------+ | |b_data +-+
189 * +->+------+ | +-----------+ |
190 * compressed | | | |
191 * data | |<--------------+ | uncompressed
192 * +------+ compressed, | data
193 * shared +-->+------+
194 * data | |
195 * | |
196 * +------+
197 *
198 * When a consumer reads a block, the ARC must first look to see if the
199 * arc_buf_hdr_t is cached. If the hdr is cached then the ARC allocates a new
200 * arc_buf_t and either copies uncompressed data into a new data buffer from an
201 * existing uncompressed arc_buf_t, decompresses the hdr's b_pabd buffer into a
202 * new data buffer, or shares the hdr's b_pabd buffer, depending on whether the
203 * hdr is compressed and the desired compression characteristics of the
204 * arc_buf_t consumer. If the arc_buf_t ends up sharing data with the
205 * arc_buf_hdr_t and both of them are uncompressed then the arc_buf_t must be
206 * the last buffer in the hdr's b_buf list, however a shared compressed buf can
207 * be anywhere in the hdr's list.
208 *
209 * The diagram below shows an example of an uncompressed ARC hdr that is
210 * sharing its data with an arc_buf_t (note that the shared uncompressed buf is
211 * the last element in the buf list):
212 *
213 * arc_buf_hdr_t
214 * +-----------+
215 * | |
216 * | |
217 * | |
218 * +-----------+
219 * l2arc_buf_hdr_t| |
220 * | |
221 * +-----------+
222 * l1arc_buf_hdr_t| |
223 * | | arc_buf_t (shared)
224 * | b_buf +------------>+---------+ arc_buf_t
225 * | | |b_next +---->+---------+
226 * | b_pabd +-+ |---------| |b_next +-->NULL
227 * +-----------+ | | | +---------+
228 * | |b_data +-+ | |
229 * | +---------+ | |b_data +-+
230 * +->+------+ | +---------+ |
231 * | | | |
232 * uncompressed | | | |
233 * data +------+ | |
234 * ^ +->+------+ |
235 * | uncompressed | | |
236 * | data | | |
237 * | +------+ |
238 * +---------------------------------+
239 *
240 * Writing to the ARC requires that the ARC first discard the hdr's b_pabd
241 * since the physical block is about to be rewritten. The new data contents
242 * will be contained in the arc_buf_t. As the I/O pipeline performs the write,
243 * it may compress the data before writing it to disk. The ARC will be called
244 * with the transformed data and will bcopy the transformed on-disk block into
245 * a newly allocated b_pabd. Writes are always done into buffers which have
246 * either been loaned (and hence are new and don't have other readers) or
247 * buffers which have been released (and hence have their own hdr, if there
248 * were originally other readers of the buf's original hdr). This ensures that
249 * the ARC only needs to update a single buf and its hdr after a write occurs.
250 *
251 * When the L2ARC is in use, it will also take advantage of the b_pabd. The
252 * L2ARC will always write the contents of b_pabd to the L2ARC. This means
253 * that when compressed ARC is enabled that the L2ARC blocks are identical
254 * to the on-disk block in the main data pool. This provides a significant
255 * advantage since the ARC can leverage the bp's checksum when reading from the
256 * L2ARC to determine if the contents are valid. However, if the compressed
257 * ARC is disabled, then the L2ARC's block must be transformed to look
258 * like the physical block in the main data pool before comparing the
259 * checksum and determining its validity.
260 *
261 * The L1ARC has a slightly different system for storing encrypted data.
262 * Raw (encrypted + possibly compressed) data has a few subtle differences from
263 * data that is just compressed. The biggest difference is that it is not
264 * possible to decrypt encrypted data (or visa versa) if the keys aren't loaded.
265 * The other difference is that encryption cannot be treated as a suggestion.
266 * If a caller would prefer compressed data, but they actually wind up with
267 * uncompressed data the worst thing that could happen is there might be a
268 * performance hit. If the caller requests encrypted data, however, we must be
269 * sure they actually get it or else secret information could be leaked. Raw
270 * data is stored in hdr->b_crypt_hdr.b_rabd. An encrypted header, therefore,
271 * may have both an encrypted version and a decrypted version of its data at
272 * once. When a caller needs a raw arc_buf_t, it is allocated and the data is
273 * copied out of this header. To avoid complications with b_pabd, raw buffers
274 * cannot be shared.
275 */
276
277 #include <sys/spa.h>
278 #include <sys/zio.h>
279 #include <sys/spa_impl.h>
280 #include <sys/zio_compress.h>
281 #include <sys/zio_checksum.h>
282 #include <sys/zfs_context.h>
283 #include <sys/arc.h>
284 #include <sys/refcount.h>
285 #include <sys/vdev.h>
286 #include <sys/vdev_impl.h>
287 #include <sys/dsl_pool.h>
288 #include <sys/zio_checksum.h>
289 #include <sys/multilist.h>
290 #include <sys/abd.h>
291 #include <sys/zil.h>
292 #include <sys/fm/fs/zfs.h>
293 #ifdef _KERNEL
294 #include <sys/vmsystm.h>
295 #include <vm/anon.h>
296 #include <sys/fs/swapnode.h>
297 #include <sys/dnlc.h>
298 #endif
299 #include <sys/callb.h>
300 #include <sys/kstat.h>
301 #include <sys/zthr.h>
302 #include <zfs_fletcher.h>
303 #include <sys/arc_impl.h>
304 #include <sys/aggsum.h>
305 #include <sys/cityhash.h>
306 #include <sys/param.h>
307
308 #ifndef _KERNEL
309 /* set with ZFS_DEBUG=watch, to enable watchpoints on frozen buffers */
310 boolean_t arc_watch = B_FALSE;
311 int arc_procfd;
312 #endif
313
314 /*
315 * This thread's job is to keep enough free memory in the system, by
316 * calling arc_kmem_reap_now() plus arc_shrink(), which improves
317 * arc_available_memory().
318 */
319 static zthr_t *arc_reap_zthr;
320
321 /*
322 * This thread's job is to keep arc_size under arc_c, by calling
323 * arc_adjust(), which improves arc_is_overflowing().
324 */
325 static zthr_t *arc_adjust_zthr;
326
327 static kmutex_t arc_adjust_lock;
328 static kcondvar_t arc_adjust_waiters_cv;
329 static boolean_t arc_adjust_needed = B_FALSE;
330
331 uint_t arc_reduce_dnlc_percent = 3;
332
333 /*
334 * The number of headers to evict in arc_evict_state_impl() before
335 * dropping the sublist lock and evicting from another sublist. A lower
336 * value means we're more likely to evict the "correct" header (i.e. the
337 * oldest header in the arc state), but comes with higher overhead
338 * (i.e. more invocations of arc_evict_state_impl()).
339 */
340 int zfs_arc_evict_batch_limit = 10;
341
342 /* number of seconds before growing cache again */
343 int arc_grow_retry = 60;
344
345 /*
346 * Minimum time between calls to arc_kmem_reap_soon(). Note that this will
347 * be converted to ticks, so with the default hz=100, a setting of 15 ms
348 * will actually wait 2 ticks, or 20ms.
349 */
350 int arc_kmem_cache_reap_retry_ms = 1000;
351
352 /* shift of arc_c for calculating overflow limit in arc_get_data_impl */
353 int zfs_arc_overflow_shift = 8;
354
355 /* shift of arc_c for calculating both min and max arc_p */
356 int arc_p_min_shift = 4;
357
358 /* log2(fraction of arc to reclaim) */
359 int arc_shrink_shift = 7;
360
361 /*
362 * log2(fraction of ARC which must be free to allow growing).
363 * I.e. If there is less than arc_c >> arc_no_grow_shift free memory,
364 * when reading a new block into the ARC, we will evict an equal-sized block
365 * from the ARC.
366 *
367 * This must be less than arc_shrink_shift, so that when we shrink the ARC,
368 * we will still not allow it to grow.
369 */
370 int arc_no_grow_shift = 5;
371
372
373 /*
374 * minimum lifespan of a prefetch block in clock ticks
375 * (initialized in arc_init())
376 */
377 static int zfs_arc_min_prefetch_ms = 1;
378 static int zfs_arc_min_prescient_prefetch_ms = 6;
379
380 /*
381 * If this percent of memory is free, don't throttle.
382 */
383 int arc_lotsfree_percent = 10;
384
385 static boolean_t arc_initialized;
386
387 /*
388 * The arc has filled available memory and has now warmed up.
389 */
390 static boolean_t arc_warm;
391
392 /*
393 * log2 fraction of the zio arena to keep free.
394 */
395 int arc_zio_arena_free_shift = 2;
396
397 /*
398 * These tunables are for performance analysis.
399 */
400 uint64_t zfs_arc_max;
401 uint64_t zfs_arc_min;
402 uint64_t zfs_arc_meta_limit = 0;
403 uint64_t zfs_arc_meta_min = 0;
404 int zfs_arc_grow_retry = 0;
405 int zfs_arc_shrink_shift = 0;
406 int zfs_arc_p_min_shift = 0;
407 int zfs_arc_average_blocksize = 8 * 1024; /* 8KB */
408
409 /*
410 * ARC dirty data constraints for arc_tempreserve_space() throttle
411 */
412 uint_t zfs_arc_dirty_limit_percent = 50; /* total dirty data limit */
413 uint_t zfs_arc_anon_limit_percent = 25; /* anon block dirty limit */
414 uint_t zfs_arc_pool_dirty_percent = 20; /* each pool's anon allowance */
415
416 boolean_t zfs_compressed_arc_enabled = B_TRUE;
417
418 /* The 6 states: */
419 static arc_state_t ARC_anon;
420 static arc_state_t ARC_mru;
421 static arc_state_t ARC_mru_ghost;
422 static arc_state_t ARC_mfu;
423 static arc_state_t ARC_mfu_ghost;
424 static arc_state_t ARC_l2c_only;
425
426 arc_stats_t arc_stats = {
427 { "hits", KSTAT_DATA_UINT64 },
428 { "misses", KSTAT_DATA_UINT64 },
429 { "demand_data_hits", KSTAT_DATA_UINT64 },
430 { "demand_data_misses", KSTAT_DATA_UINT64 },
431 { "demand_metadata_hits", KSTAT_DATA_UINT64 },
432 { "demand_metadata_misses", KSTAT_DATA_UINT64 },
433 { "prefetch_data_hits", KSTAT_DATA_UINT64 },
434 { "prefetch_data_misses", KSTAT_DATA_UINT64 },
435 { "prefetch_metadata_hits", KSTAT_DATA_UINT64 },
436 { "prefetch_metadata_misses", KSTAT_DATA_UINT64 },
437 { "mru_hits", KSTAT_DATA_UINT64 },
438 { "mru_ghost_hits", KSTAT_DATA_UINT64 },
439 { "mfu_hits", KSTAT_DATA_UINT64 },
440 { "mfu_ghost_hits", KSTAT_DATA_UINT64 },
441 { "deleted", KSTAT_DATA_UINT64 },
442 { "mutex_miss", KSTAT_DATA_UINT64 },
443 { "access_skip", KSTAT_DATA_UINT64 },
444 { "evict_skip", KSTAT_DATA_UINT64 },
445 { "evict_not_enough", KSTAT_DATA_UINT64 },
446 { "evict_l2_cached", KSTAT_DATA_UINT64 },
447 { "evict_l2_eligible", KSTAT_DATA_UINT64 },
448 { "evict_l2_eligible_mfu", KSTAT_DATA_UINT64 },
449 { "evict_l2_eligible_mru", KSTAT_DATA_UINT64 },
450 { "evict_l2_ineligible", KSTAT_DATA_UINT64 },
451 { "evict_l2_skip", KSTAT_DATA_UINT64 },
452 { "hash_elements", KSTAT_DATA_UINT64 },
453 { "hash_elements_max", KSTAT_DATA_UINT64 },
454 { "hash_collisions", KSTAT_DATA_UINT64 },
455 { "hash_chains", KSTAT_DATA_UINT64 },
456 { "hash_chain_max", KSTAT_DATA_UINT64 },
457 { "p", KSTAT_DATA_UINT64 },
458 { "c", KSTAT_DATA_UINT64 },
459 { "c_min", KSTAT_DATA_UINT64 },
460 { "c_max", KSTAT_DATA_UINT64 },
461 { "size", KSTAT_DATA_UINT64 },
462 { "compressed_size", KSTAT_DATA_UINT64 },
463 { "uncompressed_size", KSTAT_DATA_UINT64 },
464 { "overhead_size", KSTAT_DATA_UINT64 },
465 { "hdr_size", KSTAT_DATA_UINT64 },
466 { "data_size", KSTAT_DATA_UINT64 },
467 { "metadata_size", KSTAT_DATA_UINT64 },
468 { "other_size", KSTAT_DATA_UINT64 },
469 { "anon_size", KSTAT_DATA_UINT64 },
470 { "anon_evictable_data", KSTAT_DATA_UINT64 },
471 { "anon_evictable_metadata", KSTAT_DATA_UINT64 },
472 { "mru_size", KSTAT_DATA_UINT64 },
473 { "mru_evictable_data", KSTAT_DATA_UINT64 },
474 { "mru_evictable_metadata", KSTAT_DATA_UINT64 },
475 { "mru_ghost_size", KSTAT_DATA_UINT64 },
476 { "mru_ghost_evictable_data", KSTAT_DATA_UINT64 },
477 { "mru_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
478 { "mfu_size", KSTAT_DATA_UINT64 },
479 { "mfu_evictable_data", KSTAT_DATA_UINT64 },
480 { "mfu_evictable_metadata", KSTAT_DATA_UINT64 },
481 { "mfu_ghost_size", KSTAT_DATA_UINT64 },
482 { "mfu_ghost_evictable_data", KSTAT_DATA_UINT64 },
483 { "mfu_ghost_evictable_metadata", KSTAT_DATA_UINT64 },
484 { "l2_hits", KSTAT_DATA_UINT64 },
485 { "l2_misses", KSTAT_DATA_UINT64 },
486 { "l2_prefetch_asize", KSTAT_DATA_UINT64 },
487 { "l2_mru_asize", KSTAT_DATA_UINT64 },
488 { "l2_mfu_asize", KSTAT_DATA_UINT64 },
489 { "l2_bufc_data_asize", KSTAT_DATA_UINT64 },
490 { "l2_bufc_metadata_asize", KSTAT_DATA_UINT64 },
491 { "l2_feeds", KSTAT_DATA_UINT64 },
492 { "l2_rw_clash", KSTAT_DATA_UINT64 },
493 { "l2_read_bytes", KSTAT_DATA_UINT64 },
494 { "l2_write_bytes", KSTAT_DATA_UINT64 },
495 { "l2_writes_sent", KSTAT_DATA_UINT64 },
496 { "l2_writes_done", KSTAT_DATA_UINT64 },
497 { "l2_writes_error", KSTAT_DATA_UINT64 },
498 { "l2_writes_lock_retry", KSTAT_DATA_UINT64 },
499 { "l2_evict_lock_retry", KSTAT_DATA_UINT64 },
500 { "l2_evict_reading", KSTAT_DATA_UINT64 },
501 { "l2_evict_l1cached", KSTAT_DATA_UINT64 },
502 { "l2_free_on_write", KSTAT_DATA_UINT64 },
503 { "l2_abort_lowmem", KSTAT_DATA_UINT64 },
504 { "l2_cksum_bad", KSTAT_DATA_UINT64 },
505 { "l2_io_error", KSTAT_DATA_UINT64 },
506 { "l2_size", KSTAT_DATA_UINT64 },
507 { "l2_asize", KSTAT_DATA_UINT64 },
508 { "l2_hdr_size", KSTAT_DATA_UINT64 },
509 { "l2_log_blk_writes", KSTAT_DATA_UINT64 },
510 { "l2_log_blk_avg_asize", KSTAT_DATA_UINT64 },
511 { "l2_log_blk_asize", KSTAT_DATA_UINT64 },
512 { "l2_log_blk_count", KSTAT_DATA_UINT64 },
513 { "l2_data_to_meta_ratio", KSTAT_DATA_UINT64 },
514 { "l2_rebuild_success", KSTAT_DATA_UINT64 },
515 { "l2_rebuild_unsupported", KSTAT_DATA_UINT64 },
516 { "l2_rebuild_io_errors", KSTAT_DATA_UINT64 },
517 { "l2_rebuild_dh_errors", KSTAT_DATA_UINT64 },
518 { "l2_rebuild_cksum_lb_errors", KSTAT_DATA_UINT64 },
519 { "l2_rebuild_lowmem", KSTAT_DATA_UINT64 },
520 { "l2_rebuild_size", KSTAT_DATA_UINT64 },
521 { "l2_rebuild_asize", KSTAT_DATA_UINT64 },
522 { "l2_rebuild_bufs", KSTAT_DATA_UINT64 },
523 { "l2_rebuild_bufs_precached", KSTAT_DATA_UINT64 },
524 { "l2_rebuild_log_blks", KSTAT_DATA_UINT64 },
525 { "memory_throttle_count", KSTAT_DATA_UINT64 },
526 { "arc_meta_used", KSTAT_DATA_UINT64 },
527 { "arc_meta_limit", KSTAT_DATA_UINT64 },
528 { "arc_meta_max", KSTAT_DATA_UINT64 },
529 { "arc_meta_min", KSTAT_DATA_UINT64 },
530 { "async_upgrade_sync", KSTAT_DATA_UINT64 },
531 { "demand_hit_predictive_prefetch", KSTAT_DATA_UINT64 },
532 { "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 },
533 };
534
535 #define ARCSTAT_MAX(stat, val) { \
536 uint64_t m; \
537 while ((val) > (m = arc_stats.stat.value.ui64) && \
538 (m != atomic_cas_64(&arc_stats.stat.value.ui64, m, (val)))) \
539 continue; \
540 }
541
542 #define ARCSTAT_MAXSTAT(stat) \
543 ARCSTAT_MAX(stat##_max, arc_stats.stat.value.ui64)
544
545 /*
546 * We define a macro to allow ARC hits/misses to be easily broken down by
547 * two separate conditions, giving a total of four different subtypes for
548 * each of hits and misses (so eight statistics total).
549 */
550 #define ARCSTAT_CONDSTAT(cond1, stat1, notstat1, cond2, stat2, notstat2, stat) \
551 if (cond1) { \
552 if (cond2) { \
553 ARCSTAT_BUMP(arcstat_##stat1##_##stat2##_##stat); \
554 } else { \
555 ARCSTAT_BUMP(arcstat_##stat1##_##notstat2##_##stat); \
556 } \
557 } else { \
558 if (cond2) { \
559 ARCSTAT_BUMP(arcstat_##notstat1##_##stat2##_##stat); \
560 } else { \
561 ARCSTAT_BUMP(arcstat_##notstat1##_##notstat2##_##stat);\
562 } \
563 }
564
565 /*
566 * This macro allows us to use kstats as floating averages. Each time we
567 * update this kstat, we first factor it and the update value by
568 * ARCSTAT_AVG_FACTOR to shrink the new value's contribution to the overall
569 * average. This macro assumes that integer loads and stores are atomic, but
570 * is not safe for multiple writers updating the kstat in parallel (only the
571 * last writer's update will remain).
572 */
573 #define ARCSTAT_F_AVG_FACTOR 3
574 #define ARCSTAT_F_AVG(stat, value) \
575 do { \
576 uint64_t x = ARCSTAT(stat); \
577 x = x - x / ARCSTAT_F_AVG_FACTOR + \
578 (value) / ARCSTAT_F_AVG_FACTOR; \
579 ARCSTAT(stat) = x; \
580 _NOTE(CONSTCOND) \
581 } while (0)
582
583 kstat_t *arc_ksp;
584 static arc_state_t *arc_anon;
585 static arc_state_t *arc_mru;
586 static arc_state_t *arc_mru_ghost;
587 static arc_state_t *arc_mfu;
588 static arc_state_t *arc_mfu_ghost;
589 static arc_state_t *arc_l2c_only;
590
591 /*
592 * There are also some ARC variables that we want to export, but that are
593 * updated so often that having the canonical representation be the statistic
594 * variable causes a performance bottleneck. We want to use aggsum_t's for these
595 * instead, but still be able to export the kstat in the same way as before.
596 * The solution is to always use the aggsum version, except in the kstat update
597 * callback.
598 */
599 aggsum_t arc_size;
600 aggsum_t arc_meta_used;
601 aggsum_t astat_data_size;
602 aggsum_t astat_metadata_size;
603 aggsum_t astat_hdr_size;
604 aggsum_t astat_other_size;
605 aggsum_t astat_l2_hdr_size;
606
607 static int arc_no_grow; /* Don't try to grow cache size */
608 static hrtime_t arc_growtime;
609 static uint64_t arc_tempreserve;
610 static uint64_t arc_loaned_bytes;
611
612 #define GHOST_STATE(state) \
613 ((state) == arc_mru_ghost || (state) == arc_mfu_ghost || \
614 (state) == arc_l2c_only)
615
616 #define HDR_IN_HASH_TABLE(hdr) ((hdr)->b_flags & ARC_FLAG_IN_HASH_TABLE)
617 #define HDR_IO_IN_PROGRESS(hdr) ((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS)
618 #define HDR_IO_ERROR(hdr) ((hdr)->b_flags & ARC_FLAG_IO_ERROR)
619 #define HDR_PREFETCH(hdr) ((hdr)->b_flags & ARC_FLAG_PREFETCH)
620 #define HDR_PRESCIENT_PREFETCH(hdr) \
621 ((hdr)->b_flags & ARC_FLAG_PRESCIENT_PREFETCH)
622 #define HDR_COMPRESSION_ENABLED(hdr) \
623 ((hdr)->b_flags & ARC_FLAG_COMPRESSED_ARC)
624
625 #define HDR_L2CACHE(hdr) ((hdr)->b_flags & ARC_FLAG_L2CACHE)
626 #define HDR_L2_READING(hdr) \
627 (((hdr)->b_flags & ARC_FLAG_IO_IN_PROGRESS) && \
628 ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR))
629 #define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
630 #define HDR_L2_EVICTED(hdr) ((hdr)->b_flags & ARC_FLAG_L2_EVICTED)
631 #define HDR_L2_WRITE_HEAD(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITE_HEAD)
632 #define HDR_PROTECTED(hdr) ((hdr)->b_flags & ARC_FLAG_PROTECTED)
633 #define HDR_NOAUTH(hdr) ((hdr)->b_flags & ARC_FLAG_NOAUTH)
634 #define HDR_SHARED_DATA(hdr) ((hdr)->b_flags & ARC_FLAG_SHARED_DATA)
635
636 #define HDR_ISTYPE_METADATA(hdr) \
637 ((hdr)->b_flags & ARC_FLAG_BUFC_METADATA)
638 #define HDR_ISTYPE_DATA(hdr) (!HDR_ISTYPE_METADATA(hdr))
639
640 #define HDR_HAS_L1HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L1HDR)
641 #define HDR_HAS_L2HDR(hdr) ((hdr)->b_flags & ARC_FLAG_HAS_L2HDR)
642 #define HDR_HAS_RABD(hdr) \
643 (HDR_HAS_L1HDR(hdr) && HDR_PROTECTED(hdr) && \
644 (hdr)->b_crypt_hdr.b_rabd != NULL)
645 #define HDR_ENCRYPTED(hdr) \
646 (HDR_PROTECTED(hdr) && DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
647 #define HDR_AUTHENTICATED(hdr) \
648 (HDR_PROTECTED(hdr) && !DMU_OT_IS_ENCRYPTED((hdr)->b_crypt_hdr.b_ot))
649
650 /* For storing compression mode in b_flags */
651 #define HDR_COMPRESS_OFFSET (highbit64(ARC_FLAG_COMPRESS_0) - 1)
652
653 #define HDR_GET_COMPRESS(hdr) ((enum zio_compress)BF32_GET((hdr)->b_flags, \
654 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS))
655 #define HDR_SET_COMPRESS(hdr, cmp) BF32_SET((hdr)->b_flags, \
656 HDR_COMPRESS_OFFSET, SPA_COMPRESSBITS, (cmp));
657
658 #define ARC_BUF_LAST(buf) ((buf)->b_next == NULL)
659 #define ARC_BUF_SHARED(buf) ((buf)->b_flags & ARC_BUF_FLAG_SHARED)
660 #define ARC_BUF_COMPRESSED(buf) ((buf)->b_flags & ARC_BUF_FLAG_COMPRESSED)
661 #define ARC_BUF_ENCRYPTED(buf) ((buf)->b_flags & ARC_BUF_FLAG_ENCRYPTED)
662
663 /*
664 * Other sizes
665 */
666
667 #define HDR_FULL_CRYPT_SIZE ((int64_t)sizeof (arc_buf_hdr_t))
668 #define HDR_FULL_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_crypt_hdr))
669 #define HDR_L2ONLY_SIZE ((int64_t)offsetof(arc_buf_hdr_t, b_l1hdr))
670
671 /*
672 * Hash table routines
673 */
674
675 #define HT_LOCK_PAD 64
676
677 struct ht_lock {
678 kmutex_t ht_lock;
679 #ifdef _KERNEL
680 unsigned char pad[(HT_LOCK_PAD - sizeof (kmutex_t))];
681 #endif
682 };
683
684 #define BUF_LOCKS 256
685 typedef struct buf_hash_table {
686 uint64_t ht_mask;
687 arc_buf_hdr_t **ht_table;
688 struct ht_lock ht_locks[BUF_LOCKS];
689 } buf_hash_table_t;
690
691 static buf_hash_table_t buf_hash_table;
692
693 #define BUF_HASH_INDEX(spa, dva, birth) \
694 (buf_hash(spa, dva, birth) & buf_hash_table.ht_mask)
695 #define BUF_HASH_LOCK_NTRY(idx) (buf_hash_table.ht_locks[idx & (BUF_LOCKS-1)])
696 #define BUF_HASH_LOCK(idx) (&(BUF_HASH_LOCK_NTRY(idx).ht_lock))
697 #define HDR_LOCK(hdr) \
698 (BUF_HASH_LOCK(BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth)))
699
700 uint64_t zfs_crc64_table[256];
701
702 /*
703 * Level 2 ARC
704 */
705
706 #define L2ARC_WRITE_SIZE (8 * 1024 * 1024) /* initial write max */
707 #define L2ARC_HEADROOM 2 /* num of writes */
708 /*
709 * If we discover during ARC scan any buffers to be compressed, we boost
710 * our headroom for the next scanning cycle by this percentage multiple.
711 */
712 #define L2ARC_HEADROOM_BOOST 200
713 #define L2ARC_FEED_SECS 1 /* caching interval secs */
714 #define L2ARC_FEED_MIN_MS 200 /* min caching interval ms */
715
716 /*
717 * We can feed L2ARC from two states of ARC buffers, mru and mfu,
718 * and each of the state has two types: data and metadata.
719 */
720 #define L2ARC_FEED_TYPES 4
721
722
723 #define l2arc_writes_sent ARCSTAT(arcstat_l2_writes_sent)
724 #define l2arc_writes_done ARCSTAT(arcstat_l2_writes_done)
725
726 /* L2ARC Performance Tunables */
727 uint64_t l2arc_write_max = L2ARC_WRITE_SIZE; /* default max write size */
728 uint64_t l2arc_write_boost = L2ARC_WRITE_SIZE; /* extra write during warmup */
729 uint64_t l2arc_headroom = L2ARC_HEADROOM; /* number of dev writes */
730 uint64_t l2arc_headroom_boost = L2ARC_HEADROOM_BOOST;
731 uint64_t l2arc_feed_secs = L2ARC_FEED_SECS; /* interval seconds */
732 uint64_t l2arc_feed_min_ms = L2ARC_FEED_MIN_MS; /* min interval milliseconds */
733 boolean_t l2arc_noprefetch = B_TRUE; /* don't cache prefetch bufs */
734 boolean_t l2arc_feed_again = B_TRUE; /* turbo warmup */
735 boolean_t l2arc_norw = B_TRUE; /* no reads during writes */
736 int l2arc_meta_percent = 33; /* limit on headers size */
737
738 /*
739 * L2ARC Internals
740 */
741 static list_t L2ARC_dev_list; /* device list */
742 static list_t *l2arc_dev_list; /* device list pointer */
743 static kmutex_t l2arc_dev_mtx; /* device list mutex */
744 static l2arc_dev_t *l2arc_dev_last; /* last device used */
745 static list_t L2ARC_free_on_write; /* free after write buf list */
746 static list_t *l2arc_free_on_write; /* free after write list ptr */
747 static kmutex_t l2arc_free_on_write_mtx; /* mutex for list */
748 static uint64_t l2arc_ndev; /* number of devices */
749
750 typedef struct l2arc_read_callback {
751 arc_buf_hdr_t *l2rcb_hdr; /* read header */
752 blkptr_t l2rcb_bp; /* original blkptr */
753 zbookmark_phys_t l2rcb_zb; /* original bookmark */
754 int l2rcb_flags; /* original flags */
755 abd_t *l2rcb_abd; /* temporary buffer */
756 } l2arc_read_callback_t;
757
758 typedef struct l2arc_data_free {
759 /* protected by l2arc_free_on_write_mtx */
760 abd_t *l2df_abd;
761 size_t l2df_size;
762 arc_buf_contents_t l2df_type;
763 list_node_t l2df_list_node;
764 } l2arc_data_free_t;
765
766 static kmutex_t l2arc_feed_thr_lock;
767 static kcondvar_t l2arc_feed_thr_cv;
768 static uint8_t l2arc_thread_exit;
769
770 static kmutex_t l2arc_rebuild_thr_lock;
771 static kcondvar_t l2arc_rebuild_thr_cv;
772
773 enum arc_hdr_alloc_flags {
774 ARC_HDR_ALLOC_RDATA = 0x1,
775 ARC_HDR_DO_ADAPT = 0x2,
776 };
777
778
779 static abd_t *arc_get_data_abd(arc_buf_hdr_t *, uint64_t, void *, boolean_t);
780 typedef enum arc_fill_flags {
781 ARC_FILL_LOCKED = 1 << 0, /* hdr lock is held */
782 ARC_FILL_COMPRESSED = 1 << 1, /* fill with compressed data */
783 ARC_FILL_ENCRYPTED = 1 << 2, /* fill with encrypted data */
784 ARC_FILL_NOAUTH = 1 << 3, /* don't attempt to authenticate */
785 ARC_FILL_IN_PLACE = 1 << 4 /* fill in place (special case) */
786 } arc_fill_flags_t;
787
788 static void *arc_get_data_buf(arc_buf_hdr_t *, uint64_t, void *);
789 static void arc_get_data_impl(arc_buf_hdr_t *, uint64_t, void *, boolean_t);
790 static void arc_free_data_abd(arc_buf_hdr_t *, abd_t *, uint64_t, void *);
791 static void arc_free_data_buf(arc_buf_hdr_t *, void *, uint64_t, void *);
792 static void arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag);
793 static void arc_hdr_free_pabd(arc_buf_hdr_t *, boolean_t);
794 static void arc_hdr_alloc_pabd(arc_buf_hdr_t *, int);
795 static void arc_access(arc_buf_hdr_t *, kmutex_t *);
796 static boolean_t arc_is_overflowing();
797 static void arc_buf_watch(arc_buf_t *);
798 static l2arc_dev_t *l2arc_vdev_get(vdev_t *vd);
799
800 static arc_buf_contents_t arc_buf_type(arc_buf_hdr_t *);
801 static uint32_t arc_bufc_to_flags(arc_buf_contents_t);
802 static inline void arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
803 static inline void arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags);
804
805 static boolean_t l2arc_write_eligible(uint64_t, arc_buf_hdr_t *);
806 static void l2arc_read_done(zio_t *);
807 static void l2arc_do_free_on_write(void);
808 static void l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
809 boolean_t state_only);
810
811 #define l2arc_hdr_arcstats_increment(hdr) \
812 l2arc_hdr_arcstats_update((hdr), B_TRUE, B_FALSE)
813 #define l2arc_hdr_arcstats_decrement(hdr) \
814 l2arc_hdr_arcstats_update((hdr), B_FALSE, B_FALSE)
815 #define l2arc_hdr_arcstats_increment_state(hdr) \
816 l2arc_hdr_arcstats_update((hdr), B_TRUE, B_TRUE)
817 #define l2arc_hdr_arcstats_decrement_state(hdr) \
818 l2arc_hdr_arcstats_update((hdr), B_FALSE, B_TRUE)
819
820 /*
821 * The arc_all_memory function is a ZoL enhancement that lives in their OSL
822 * code. In user-space code, which is used primarily for testing, we return
823 * half of all memory.
824 */
825 uint64_t
arc_all_memory(void)826 arc_all_memory(void)
827 {
828 #ifdef _KERNEL
829 return (ptob(physmem));
830 #else
831 return ((sysconf(_SC_PAGESIZE) * sysconf(_SC_PHYS_PAGES)) / 2);
832 #endif
833 }
834
835 /*
836 * We use Cityhash for this. It's fast, and has good hash properties without
837 * requiring any large static buffers.
838 */
839 static uint64_t
buf_hash(uint64_t spa,const dva_t * dva,uint64_t birth)840 buf_hash(uint64_t spa, const dva_t *dva, uint64_t birth)
841 {
842 return (cityhash4(spa, dva->dva_word[0], dva->dva_word[1], birth));
843 }
844
845 #define HDR_EMPTY(hdr) \
846 ((hdr)->b_dva.dva_word[0] == 0 && \
847 (hdr)->b_dva.dva_word[1] == 0)
848
849 #define HDR_EMPTY_OR_LOCKED(hdr) \
850 (HDR_EMPTY(hdr) || MUTEX_HELD(HDR_LOCK(hdr)))
851
852 #define HDR_EQUAL(spa, dva, birth, hdr) \
853 ((hdr)->b_dva.dva_word[0] == (dva)->dva_word[0]) && \
854 ((hdr)->b_dva.dva_word[1] == (dva)->dva_word[1]) && \
855 ((hdr)->b_birth == birth) && ((hdr)->b_spa == spa)
856
857 static void
buf_discard_identity(arc_buf_hdr_t * hdr)858 buf_discard_identity(arc_buf_hdr_t *hdr)
859 {
860 hdr->b_dva.dva_word[0] = 0;
861 hdr->b_dva.dva_word[1] = 0;
862 hdr->b_birth = 0;
863 }
864
865 static arc_buf_hdr_t *
buf_hash_find(uint64_t spa,const blkptr_t * bp,kmutex_t ** lockp)866 buf_hash_find(uint64_t spa, const blkptr_t *bp, kmutex_t **lockp)
867 {
868 const dva_t *dva = BP_IDENTITY(bp);
869 uint64_t birth = BP_PHYSICAL_BIRTH(bp);
870 uint64_t idx = BUF_HASH_INDEX(spa, dva, birth);
871 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
872 arc_buf_hdr_t *hdr;
873
874 mutex_enter(hash_lock);
875 for (hdr = buf_hash_table.ht_table[idx]; hdr != NULL;
876 hdr = hdr->b_hash_next) {
877 if (HDR_EQUAL(spa, dva, birth, hdr)) {
878 *lockp = hash_lock;
879 return (hdr);
880 }
881 }
882 mutex_exit(hash_lock);
883 *lockp = NULL;
884 return (NULL);
885 }
886
887 /*
888 * Insert an entry into the hash table. If there is already an element
889 * equal to elem in the hash table, then the already existing element
890 * will be returned and the new element will not be inserted.
891 * Otherwise returns NULL.
892 * If lockp == NULL, the caller is assumed to already hold the hash lock.
893 */
894 static arc_buf_hdr_t *
buf_hash_insert(arc_buf_hdr_t * hdr,kmutex_t ** lockp)895 buf_hash_insert(arc_buf_hdr_t *hdr, kmutex_t **lockp)
896 {
897 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
898 kmutex_t *hash_lock = BUF_HASH_LOCK(idx);
899 arc_buf_hdr_t *fhdr;
900 uint32_t i;
901
902 ASSERT(!DVA_IS_EMPTY(&hdr->b_dva));
903 ASSERT(hdr->b_birth != 0);
904 ASSERT(!HDR_IN_HASH_TABLE(hdr));
905
906 if (lockp != NULL) {
907 *lockp = hash_lock;
908 mutex_enter(hash_lock);
909 } else {
910 ASSERT(MUTEX_HELD(hash_lock));
911 }
912
913 for (fhdr = buf_hash_table.ht_table[idx], i = 0; fhdr != NULL;
914 fhdr = fhdr->b_hash_next, i++) {
915 if (HDR_EQUAL(hdr->b_spa, &hdr->b_dva, hdr->b_birth, fhdr))
916 return (fhdr);
917 }
918
919 hdr->b_hash_next = buf_hash_table.ht_table[idx];
920 buf_hash_table.ht_table[idx] = hdr;
921 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
922
923 /* collect some hash table performance data */
924 if (i > 0) {
925 ARCSTAT_BUMP(arcstat_hash_collisions);
926 if (i == 1)
927 ARCSTAT_BUMP(arcstat_hash_chains);
928
929 ARCSTAT_MAX(arcstat_hash_chain_max, i);
930 }
931
932 ARCSTAT_BUMP(arcstat_hash_elements);
933 ARCSTAT_MAXSTAT(arcstat_hash_elements);
934
935 return (NULL);
936 }
937
938 static void
buf_hash_remove(arc_buf_hdr_t * hdr)939 buf_hash_remove(arc_buf_hdr_t *hdr)
940 {
941 arc_buf_hdr_t *fhdr, **hdrp;
942 uint64_t idx = BUF_HASH_INDEX(hdr->b_spa, &hdr->b_dva, hdr->b_birth);
943
944 ASSERT(MUTEX_HELD(BUF_HASH_LOCK(idx)));
945 ASSERT(HDR_IN_HASH_TABLE(hdr));
946
947 hdrp = &buf_hash_table.ht_table[idx];
948 while ((fhdr = *hdrp) != hdr) {
949 ASSERT3P(fhdr, !=, NULL);
950 hdrp = &fhdr->b_hash_next;
951 }
952 *hdrp = hdr->b_hash_next;
953 hdr->b_hash_next = NULL;
954 arc_hdr_clear_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
955
956 /* collect some hash table performance data */
957 ARCSTAT_BUMPDOWN(arcstat_hash_elements);
958
959 if (buf_hash_table.ht_table[idx] &&
960 buf_hash_table.ht_table[idx]->b_hash_next == NULL)
961 ARCSTAT_BUMPDOWN(arcstat_hash_chains);
962 }
963
964 /*
965 * l2arc_mfuonly : A ZFS module parameter that controls whether only MFU
966 * metadata and data are cached from ARC into L2ARC.
967 */
968 int l2arc_mfuonly = 0;
969
970 /*
971 * Global data structures and functions for the buf kmem cache.
972 */
973
974 static kmem_cache_t *hdr_full_cache;
975 static kmem_cache_t *hdr_full_crypt_cache;
976 static kmem_cache_t *hdr_l2only_cache;
977 static kmem_cache_t *buf_cache;
978
979 static void
buf_fini(void)980 buf_fini(void)
981 {
982 int i;
983
984 kmem_free(buf_hash_table.ht_table,
985 (buf_hash_table.ht_mask + 1) * sizeof (void *));
986 for (i = 0; i < BUF_LOCKS; i++)
987 mutex_destroy(&buf_hash_table.ht_locks[i].ht_lock);
988 kmem_cache_destroy(hdr_full_cache);
989 kmem_cache_destroy(hdr_full_crypt_cache);
990 kmem_cache_destroy(hdr_l2only_cache);
991 kmem_cache_destroy(buf_cache);
992 }
993
994 /*
995 * Constructor callback - called when the cache is empty
996 * and a new buf is requested.
997 */
998 /* ARGSUSED */
999 static int
hdr_full_cons(void * vbuf,void * unused,int kmflag)1000 hdr_full_cons(void *vbuf, void *unused, int kmflag)
1001 {
1002 arc_buf_hdr_t *hdr = vbuf;
1003
1004 bzero(hdr, HDR_FULL_SIZE);
1005 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
1006 cv_init(&hdr->b_l1hdr.b_cv, NULL, CV_DEFAULT, NULL);
1007 zfs_refcount_create(&hdr->b_l1hdr.b_refcnt);
1008 mutex_init(&hdr->b_l1hdr.b_freeze_lock, NULL, MUTEX_DEFAULT, NULL);
1009 multilist_link_init(&hdr->b_l1hdr.b_arc_node);
1010 arc_space_consume(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1011
1012 return (0);
1013 }
1014
1015 /* ARGSUSED */
1016 static int
hdr_full_crypt_cons(void * vbuf,void * unused,int kmflag)1017 hdr_full_crypt_cons(void *vbuf, void *unused, int kmflag)
1018 {
1019 arc_buf_hdr_t *hdr = vbuf;
1020
1021 (void) hdr_full_cons(vbuf, unused, kmflag);
1022 bzero(&hdr->b_crypt_hdr, sizeof (hdr->b_crypt_hdr));
1023 arc_space_consume(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS);
1024
1025 return (0);
1026 }
1027
1028 /* ARGSUSED */
1029 static int
hdr_l2only_cons(void * vbuf,void * unused,int kmflag)1030 hdr_l2only_cons(void *vbuf, void *unused, int kmflag)
1031 {
1032 arc_buf_hdr_t *hdr = vbuf;
1033
1034 bzero(hdr, HDR_L2ONLY_SIZE);
1035 arc_space_consume(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1036
1037 return (0);
1038 }
1039
1040 /* ARGSUSED */
1041 static int
buf_cons(void * vbuf,void * unused,int kmflag)1042 buf_cons(void *vbuf, void *unused, int kmflag)
1043 {
1044 arc_buf_t *buf = vbuf;
1045
1046 bzero(buf, sizeof (arc_buf_t));
1047 mutex_init(&buf->b_evict_lock, NULL, MUTEX_DEFAULT, NULL);
1048 arc_space_consume(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1049
1050 return (0);
1051 }
1052
1053 /*
1054 * Destructor callback - called when a cached buf is
1055 * no longer required.
1056 */
1057 /* ARGSUSED */
1058 static void
hdr_full_dest(void * vbuf,void * unused)1059 hdr_full_dest(void *vbuf, void *unused)
1060 {
1061 arc_buf_hdr_t *hdr = vbuf;
1062
1063 ASSERT(HDR_EMPTY(hdr));
1064 cv_destroy(&hdr->b_l1hdr.b_cv);
1065 zfs_refcount_destroy(&hdr->b_l1hdr.b_refcnt);
1066 mutex_destroy(&hdr->b_l1hdr.b_freeze_lock);
1067 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
1068 arc_space_return(HDR_FULL_SIZE, ARC_SPACE_HDRS);
1069 }
1070
1071 /* ARGSUSED */
1072 static void
hdr_full_crypt_dest(void * vbuf,void * unused)1073 hdr_full_crypt_dest(void *vbuf, void *unused)
1074 {
1075 arc_buf_hdr_t *hdr = vbuf;
1076
1077 hdr_full_dest(hdr, unused);
1078 arc_space_return(sizeof (hdr->b_crypt_hdr), ARC_SPACE_HDRS);
1079 }
1080
1081 /* ARGSUSED */
1082 static void
hdr_l2only_dest(void * vbuf,void * unused)1083 hdr_l2only_dest(void *vbuf, void *unused)
1084 {
1085 arc_buf_hdr_t *hdr = vbuf;
1086
1087 ASSERT(HDR_EMPTY(hdr));
1088 arc_space_return(HDR_L2ONLY_SIZE, ARC_SPACE_L2HDRS);
1089 }
1090
1091 /* ARGSUSED */
1092 static void
buf_dest(void * vbuf,void * unused)1093 buf_dest(void *vbuf, void *unused)
1094 {
1095 arc_buf_t *buf = vbuf;
1096
1097 mutex_destroy(&buf->b_evict_lock);
1098 arc_space_return(sizeof (arc_buf_t), ARC_SPACE_HDRS);
1099 }
1100
1101 /*
1102 * Reclaim callback -- invoked when memory is low.
1103 */
1104 /* ARGSUSED */
1105 static void
hdr_recl(void * unused)1106 hdr_recl(void *unused)
1107 {
1108 dprintf("hdr_recl called\n");
1109 /*
1110 * umem calls the reclaim func when we destroy the buf cache,
1111 * which is after we do arc_fini().
1112 */
1113 if (arc_initialized)
1114 zthr_wakeup(arc_reap_zthr);
1115 }
1116
1117 static void
buf_init(void)1118 buf_init(void)
1119 {
1120 uint64_t *ct;
1121 uint64_t hsize = 1ULL << 12;
1122 int i, j;
1123
1124 /*
1125 * The hash table is big enough to fill all of physical memory
1126 * with an average block size of zfs_arc_average_blocksize (default 8K).
1127 * By default, the table will take up
1128 * totalmem * sizeof(void*) / 8K (1MB per GB with 8-byte pointers).
1129 */
1130 while (hsize * zfs_arc_average_blocksize < physmem * PAGESIZE)
1131 hsize <<= 1;
1132 retry:
1133 buf_hash_table.ht_mask = hsize - 1;
1134 buf_hash_table.ht_table =
1135 kmem_zalloc(hsize * sizeof (void*), KM_NOSLEEP);
1136 if (buf_hash_table.ht_table == NULL) {
1137 ASSERT(hsize > (1ULL << 8));
1138 hsize >>= 1;
1139 goto retry;
1140 }
1141
1142 hdr_full_cache = kmem_cache_create("arc_buf_hdr_t_full", HDR_FULL_SIZE,
1143 0, hdr_full_cons, hdr_full_dest, hdr_recl, NULL, NULL, 0);
1144 hdr_full_crypt_cache = kmem_cache_create("arc_buf_hdr_t_full_crypt",
1145 HDR_FULL_CRYPT_SIZE, 0, hdr_full_crypt_cons, hdr_full_crypt_dest,
1146 hdr_recl, NULL, NULL, 0);
1147 hdr_l2only_cache = kmem_cache_create("arc_buf_hdr_t_l2only",
1148 HDR_L2ONLY_SIZE, 0, hdr_l2only_cons, hdr_l2only_dest, hdr_recl,
1149 NULL, NULL, 0);
1150 buf_cache = kmem_cache_create("arc_buf_t", sizeof (arc_buf_t),
1151 0, buf_cons, buf_dest, NULL, NULL, NULL, 0);
1152
1153 for (i = 0; i < 256; i++)
1154 for (ct = zfs_crc64_table + i, *ct = i, j = 8; j > 0; j--)
1155 *ct = (*ct >> 1) ^ (-(*ct & 1) & ZFS_CRC64_POLY);
1156
1157 for (i = 0; i < BUF_LOCKS; i++) {
1158 mutex_init(&buf_hash_table.ht_locks[i].ht_lock,
1159 NULL, MUTEX_DEFAULT, NULL);
1160 }
1161 }
1162
1163 /*
1164 * This is the size that the buf occupies in memory. If the buf is compressed,
1165 * it will correspond to the compressed size. You should use this method of
1166 * getting the buf size unless you explicitly need the logical size.
1167 */
1168 int32_t
arc_buf_size(arc_buf_t * buf)1169 arc_buf_size(arc_buf_t *buf)
1170 {
1171 return (ARC_BUF_COMPRESSED(buf) ?
1172 HDR_GET_PSIZE(buf->b_hdr) : HDR_GET_LSIZE(buf->b_hdr));
1173 }
1174
1175 int32_t
arc_buf_lsize(arc_buf_t * buf)1176 arc_buf_lsize(arc_buf_t *buf)
1177 {
1178 return (HDR_GET_LSIZE(buf->b_hdr));
1179 }
1180
1181 /*
1182 * This function will return B_TRUE if the buffer is encrypted in memory.
1183 * This buffer can be decrypted by calling arc_untransform().
1184 */
1185 boolean_t
arc_is_encrypted(arc_buf_t * buf)1186 arc_is_encrypted(arc_buf_t *buf)
1187 {
1188 return (ARC_BUF_ENCRYPTED(buf) != 0);
1189 }
1190
1191 /*
1192 * Returns B_TRUE if the buffer represents data that has not had its MAC
1193 * verified yet.
1194 */
1195 boolean_t
arc_is_unauthenticated(arc_buf_t * buf)1196 arc_is_unauthenticated(arc_buf_t *buf)
1197 {
1198 return (HDR_NOAUTH(buf->b_hdr) != 0);
1199 }
1200
1201 void
arc_get_raw_params(arc_buf_t * buf,boolean_t * byteorder,uint8_t * salt,uint8_t * iv,uint8_t * mac)1202 arc_get_raw_params(arc_buf_t *buf, boolean_t *byteorder, uint8_t *salt,
1203 uint8_t *iv, uint8_t *mac)
1204 {
1205 arc_buf_hdr_t *hdr = buf->b_hdr;
1206
1207 ASSERT(HDR_PROTECTED(hdr));
1208
1209 bcopy(hdr->b_crypt_hdr.b_salt, salt, ZIO_DATA_SALT_LEN);
1210 bcopy(hdr->b_crypt_hdr.b_iv, iv, ZIO_DATA_IV_LEN);
1211 bcopy(hdr->b_crypt_hdr.b_mac, mac, ZIO_DATA_MAC_LEN);
1212 *byteorder = (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
1213 /* CONSTCOND */
1214 ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
1215 }
1216
1217 /*
1218 * Indicates how this buffer is compressed in memory. If it is not compressed
1219 * the value will be ZIO_COMPRESS_OFF. It can be made normally readable with
1220 * arc_untransform() as long as it is also unencrypted.
1221 */
1222 enum zio_compress
arc_get_compression(arc_buf_t * buf)1223 arc_get_compression(arc_buf_t *buf)
1224 {
1225 return (ARC_BUF_COMPRESSED(buf) ?
1226 HDR_GET_COMPRESS(buf->b_hdr) : ZIO_COMPRESS_OFF);
1227 }
1228
1229 #define ARC_MINTIME (hz>>4) /* 62 ms */
1230
1231 /*
1232 * Return the compression algorithm used to store this data in the ARC. If ARC
1233 * compression is enabled or this is an encrypted block, this will be the same
1234 * as what's used to store it on-disk. Otherwise, this will be ZIO_COMPRESS_OFF.
1235 */
1236 static inline enum zio_compress
arc_hdr_get_compress(arc_buf_hdr_t * hdr)1237 arc_hdr_get_compress(arc_buf_hdr_t *hdr)
1238 {
1239 return (HDR_COMPRESSION_ENABLED(hdr) ?
1240 HDR_GET_COMPRESS(hdr) : ZIO_COMPRESS_OFF);
1241 }
1242
1243 static inline boolean_t
arc_buf_is_shared(arc_buf_t * buf)1244 arc_buf_is_shared(arc_buf_t *buf)
1245 {
1246 boolean_t shared = (buf->b_data != NULL &&
1247 buf->b_hdr->b_l1hdr.b_pabd != NULL &&
1248 abd_is_linear(buf->b_hdr->b_l1hdr.b_pabd) &&
1249 buf->b_data == abd_to_buf(buf->b_hdr->b_l1hdr.b_pabd));
1250 IMPLY(shared, HDR_SHARED_DATA(buf->b_hdr));
1251 IMPLY(shared, ARC_BUF_SHARED(buf));
1252 IMPLY(shared, ARC_BUF_COMPRESSED(buf) || ARC_BUF_LAST(buf));
1253
1254 /*
1255 * It would be nice to assert arc_can_share() too, but the "hdr isn't
1256 * already being shared" requirement prevents us from doing that.
1257 */
1258
1259 return (shared);
1260 }
1261
1262 /*
1263 * Free the checksum associated with this header. If there is no checksum, this
1264 * is a no-op.
1265 */
1266 static inline void
arc_cksum_free(arc_buf_hdr_t * hdr)1267 arc_cksum_free(arc_buf_hdr_t *hdr)
1268 {
1269 ASSERT(HDR_HAS_L1HDR(hdr));
1270
1271 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1272 if (hdr->b_l1hdr.b_freeze_cksum != NULL) {
1273 kmem_free(hdr->b_l1hdr.b_freeze_cksum, sizeof (zio_cksum_t));
1274 hdr->b_l1hdr.b_freeze_cksum = NULL;
1275 }
1276 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1277 }
1278
1279 /*
1280 * Return true iff at least one of the bufs on hdr is not compressed.
1281 * Encrypted buffers count as compressed.
1282 */
1283 static boolean_t
arc_hdr_has_uncompressed_buf(arc_buf_hdr_t * hdr)1284 arc_hdr_has_uncompressed_buf(arc_buf_hdr_t *hdr)
1285 {
1286 ASSERT(hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY_OR_LOCKED(hdr));
1287
1288 for (arc_buf_t *b = hdr->b_l1hdr.b_buf; b != NULL; b = b->b_next) {
1289 if (!ARC_BUF_COMPRESSED(b)) {
1290 return (B_TRUE);
1291 }
1292 }
1293 return (B_FALSE);
1294 }
1295
1296 /*
1297 * If we've turned on the ZFS_DEBUG_MODIFY flag, verify that the buf's data
1298 * matches the checksum that is stored in the hdr. If there is no checksum,
1299 * or if the buf is compressed, this is a no-op.
1300 */
1301 static void
arc_cksum_verify(arc_buf_t * buf)1302 arc_cksum_verify(arc_buf_t *buf)
1303 {
1304 arc_buf_hdr_t *hdr = buf->b_hdr;
1305 zio_cksum_t zc;
1306
1307 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1308 return;
1309
1310 if (ARC_BUF_COMPRESSED(buf))
1311 return;
1312
1313 ASSERT(HDR_HAS_L1HDR(hdr));
1314
1315 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1316
1317 if (hdr->b_l1hdr.b_freeze_cksum == NULL || HDR_IO_ERROR(hdr)) {
1318 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1319 return;
1320 }
1321
1322 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL, &zc);
1323 if (!ZIO_CHECKSUM_EQUAL(*hdr->b_l1hdr.b_freeze_cksum, zc))
1324 panic("buffer modified while frozen!");
1325 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1326 }
1327
1328 /*
1329 * This function makes the assumption that data stored in the L2ARC
1330 * will be transformed exactly as it is in the main pool. Because of
1331 * this we can verify the checksum against the reading process's bp.
1332 */
1333 static boolean_t
arc_cksum_is_equal(arc_buf_hdr_t * hdr,zio_t * zio)1334 arc_cksum_is_equal(arc_buf_hdr_t *hdr, zio_t *zio)
1335 {
1336 ASSERT(!BP_IS_EMBEDDED(zio->io_bp));
1337 VERIFY3U(BP_GET_PSIZE(zio->io_bp), ==, HDR_GET_PSIZE(hdr));
1338
1339 /*
1340 * Block pointers always store the checksum for the logical data.
1341 * If the block pointer has the gang bit set, then the checksum
1342 * it represents is for the reconstituted data and not for an
1343 * individual gang member. The zio pipeline, however, must be able to
1344 * determine the checksum of each of the gang constituents so it
1345 * treats the checksum comparison differently than what we need
1346 * for l2arc blocks. This prevents us from using the
1347 * zio_checksum_error() interface directly. Instead we must call the
1348 * zio_checksum_error_impl() so that we can ensure the checksum is
1349 * generated using the correct checksum algorithm and accounts for the
1350 * logical I/O size and not just a gang fragment.
1351 */
1352 return (zio_checksum_error_impl(zio->io_spa, zio->io_bp,
1353 BP_GET_CHECKSUM(zio->io_bp), zio->io_abd, zio->io_size,
1354 zio->io_offset, NULL) == 0);
1355 }
1356
1357 /*
1358 * Given a buf full of data, if ZFS_DEBUG_MODIFY is enabled this computes a
1359 * checksum and attaches it to the buf's hdr so that we can ensure that the buf
1360 * isn't modified later on. If buf is compressed or there is already a checksum
1361 * on the hdr, this is a no-op (we only checksum uncompressed bufs).
1362 */
1363 static void
arc_cksum_compute(arc_buf_t * buf)1364 arc_cksum_compute(arc_buf_t *buf)
1365 {
1366 arc_buf_hdr_t *hdr = buf->b_hdr;
1367
1368 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1369 return;
1370
1371 ASSERT(HDR_HAS_L1HDR(hdr));
1372
1373 mutex_enter(&buf->b_hdr->b_l1hdr.b_freeze_lock);
1374 if (hdr->b_l1hdr.b_freeze_cksum != NULL || ARC_BUF_COMPRESSED(buf)) {
1375 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1376 return;
1377 }
1378
1379 ASSERT(!ARC_BUF_ENCRYPTED(buf));
1380 ASSERT(!ARC_BUF_COMPRESSED(buf));
1381 hdr->b_l1hdr.b_freeze_cksum = kmem_alloc(sizeof (zio_cksum_t),
1382 KM_SLEEP);
1383 fletcher_2_native(buf->b_data, arc_buf_size(buf), NULL,
1384 hdr->b_l1hdr.b_freeze_cksum);
1385 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1386 arc_buf_watch(buf);
1387 }
1388
1389 #ifndef _KERNEL
1390 typedef struct procctl {
1391 long cmd;
1392 prwatch_t prwatch;
1393 } procctl_t;
1394 #endif
1395
1396 /* ARGSUSED */
1397 static void
arc_buf_unwatch(arc_buf_t * buf)1398 arc_buf_unwatch(arc_buf_t *buf)
1399 {
1400 #ifndef _KERNEL
1401 if (arc_watch) {
1402 int result;
1403 procctl_t ctl;
1404 ctl.cmd = PCWATCH;
1405 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1406 ctl.prwatch.pr_size = 0;
1407 ctl.prwatch.pr_wflags = 0;
1408 result = write(arc_procfd, &ctl, sizeof (ctl));
1409 ASSERT3U(result, ==, sizeof (ctl));
1410 }
1411 #endif
1412 }
1413
1414 /* ARGSUSED */
1415 static void
arc_buf_watch(arc_buf_t * buf)1416 arc_buf_watch(arc_buf_t *buf)
1417 {
1418 #ifndef _KERNEL
1419 if (arc_watch) {
1420 int result;
1421 procctl_t ctl;
1422 ctl.cmd = PCWATCH;
1423 ctl.prwatch.pr_vaddr = (uintptr_t)buf->b_data;
1424 ctl.prwatch.pr_size = arc_buf_size(buf);
1425 ctl.prwatch.pr_wflags = WA_WRITE;
1426 result = write(arc_procfd, &ctl, sizeof (ctl));
1427 ASSERT3U(result, ==, sizeof (ctl));
1428 }
1429 #endif
1430 }
1431
1432 static arc_buf_contents_t
arc_buf_type(arc_buf_hdr_t * hdr)1433 arc_buf_type(arc_buf_hdr_t *hdr)
1434 {
1435 arc_buf_contents_t type;
1436 if (HDR_ISTYPE_METADATA(hdr)) {
1437 type = ARC_BUFC_METADATA;
1438 } else {
1439 type = ARC_BUFC_DATA;
1440 }
1441 VERIFY3U(hdr->b_type, ==, type);
1442 return (type);
1443 }
1444
1445 boolean_t
arc_is_metadata(arc_buf_t * buf)1446 arc_is_metadata(arc_buf_t *buf)
1447 {
1448 return (HDR_ISTYPE_METADATA(buf->b_hdr) != 0);
1449 }
1450
1451 static uint32_t
arc_bufc_to_flags(arc_buf_contents_t type)1452 arc_bufc_to_flags(arc_buf_contents_t type)
1453 {
1454 switch (type) {
1455 case ARC_BUFC_DATA:
1456 /* metadata field is 0 if buffer contains normal data */
1457 return (0);
1458 case ARC_BUFC_METADATA:
1459 return (ARC_FLAG_BUFC_METADATA);
1460 default:
1461 break;
1462 }
1463 panic("undefined ARC buffer type!");
1464 return ((uint32_t)-1);
1465 }
1466
1467 void
arc_buf_thaw(arc_buf_t * buf)1468 arc_buf_thaw(arc_buf_t *buf)
1469 {
1470 arc_buf_hdr_t *hdr = buf->b_hdr;
1471
1472 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
1473 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
1474
1475 arc_cksum_verify(buf);
1476
1477 /*
1478 * Compressed buffers do not manipulate the b_freeze_cksum.
1479 */
1480 if (ARC_BUF_COMPRESSED(buf))
1481 return;
1482
1483 ASSERT(HDR_HAS_L1HDR(hdr));
1484 arc_cksum_free(hdr);
1485
1486 mutex_enter(&hdr->b_l1hdr.b_freeze_lock);
1487 #ifdef ZFS_DEBUG
1488 if (zfs_flags & ZFS_DEBUG_MODIFY) {
1489 if (hdr->b_l1hdr.b_thawed != NULL)
1490 kmem_free(hdr->b_l1hdr.b_thawed, 1);
1491 hdr->b_l1hdr.b_thawed = kmem_alloc(1, KM_SLEEP);
1492 }
1493 #endif
1494
1495 mutex_exit(&hdr->b_l1hdr.b_freeze_lock);
1496
1497 arc_buf_unwatch(buf);
1498 }
1499
1500 void
arc_buf_freeze(arc_buf_t * buf)1501 arc_buf_freeze(arc_buf_t *buf)
1502 {
1503 if (!(zfs_flags & ZFS_DEBUG_MODIFY))
1504 return;
1505
1506 if (ARC_BUF_COMPRESSED(buf))
1507 return;
1508
1509 ASSERT(HDR_HAS_L1HDR(buf->b_hdr));
1510 arc_cksum_compute(buf);
1511 }
1512
1513 /*
1514 * The arc_buf_hdr_t's b_flags should never be modified directly. Instead,
1515 * the following functions should be used to ensure that the flags are
1516 * updated in a thread-safe way. When manipulating the flags either
1517 * the hash_lock must be held or the hdr must be undiscoverable. This
1518 * ensures that we're not racing with any other threads when updating
1519 * the flags.
1520 */
1521 static inline void
arc_hdr_set_flags(arc_buf_hdr_t * hdr,arc_flags_t flags)1522 arc_hdr_set_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1523 {
1524 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1525 hdr->b_flags |= flags;
1526 }
1527
1528 static inline void
arc_hdr_clear_flags(arc_buf_hdr_t * hdr,arc_flags_t flags)1529 arc_hdr_clear_flags(arc_buf_hdr_t *hdr, arc_flags_t flags)
1530 {
1531 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1532 hdr->b_flags &= ~flags;
1533 }
1534
1535 /*
1536 * Setting the compression bits in the arc_buf_hdr_t's b_flags is
1537 * done in a special way since we have to clear and set bits
1538 * at the same time. Consumers that wish to set the compression bits
1539 * must use this function to ensure that the flags are updated in
1540 * thread-safe manner.
1541 */
1542 static void
arc_hdr_set_compress(arc_buf_hdr_t * hdr,enum zio_compress cmp)1543 arc_hdr_set_compress(arc_buf_hdr_t *hdr, enum zio_compress cmp)
1544 {
1545 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1546
1547 /*
1548 * Holes and embedded blocks will always have a psize = 0 so
1549 * we ignore the compression of the blkptr and set the
1550 * arc_buf_hdr_t's compression to ZIO_COMPRESS_OFF.
1551 * Holes and embedded blocks remain anonymous so we don't
1552 * want to uncompress them. Mark them as uncompressed.
1553 */
1554 if (!zfs_compressed_arc_enabled || HDR_GET_PSIZE(hdr) == 0) {
1555 arc_hdr_clear_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1556 ASSERT(!HDR_COMPRESSION_ENABLED(hdr));
1557 } else {
1558 arc_hdr_set_flags(hdr, ARC_FLAG_COMPRESSED_ARC);
1559 ASSERT(HDR_COMPRESSION_ENABLED(hdr));
1560 }
1561
1562 HDR_SET_COMPRESS(hdr, cmp);
1563 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, cmp);
1564 }
1565
1566 /*
1567 * Looks for another buf on the same hdr which has the data decompressed, copies
1568 * from it, and returns true. If no such buf exists, returns false.
1569 */
1570 static boolean_t
arc_buf_try_copy_decompressed_data(arc_buf_t * buf)1571 arc_buf_try_copy_decompressed_data(arc_buf_t *buf)
1572 {
1573 arc_buf_hdr_t *hdr = buf->b_hdr;
1574 boolean_t copied = B_FALSE;
1575
1576 ASSERT(HDR_HAS_L1HDR(hdr));
1577 ASSERT3P(buf->b_data, !=, NULL);
1578 ASSERT(!ARC_BUF_COMPRESSED(buf));
1579
1580 for (arc_buf_t *from = hdr->b_l1hdr.b_buf; from != NULL;
1581 from = from->b_next) {
1582 /* can't use our own data buffer */
1583 if (from == buf) {
1584 continue;
1585 }
1586
1587 if (!ARC_BUF_COMPRESSED(from)) {
1588 bcopy(from->b_data, buf->b_data, arc_buf_size(buf));
1589 copied = B_TRUE;
1590 break;
1591 }
1592 }
1593
1594 /*
1595 * Note: With encryption support, the following assertion is no longer
1596 * necessarily valid. If we receive two back to back raw snapshots
1597 * (send -w), the second receive can use a hdr with a cksum already
1598 * calculated. This happens via:
1599 * dmu_recv_stream() -> receive_read_record() -> arc_loan_raw_buf()
1600 * The rsend/send_mixed_raw test case exercises this code path.
1601 *
1602 * There were no decompressed bufs, so there should not be a
1603 * checksum on the hdr either.
1604 * EQUIV(!copied, hdr->b_l1hdr.b_freeze_cksum == NULL);
1605 */
1606
1607 return (copied);
1608 }
1609
1610 /*
1611 * Return the size of the block, b_pabd, that is stored in the arc_buf_hdr_t.
1612 */
1613 static uint64_t
arc_hdr_size(arc_buf_hdr_t * hdr)1614 arc_hdr_size(arc_buf_hdr_t *hdr)
1615 {
1616 uint64_t size;
1617
1618 if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
1619 HDR_GET_PSIZE(hdr) > 0) {
1620 size = HDR_GET_PSIZE(hdr);
1621 } else {
1622 ASSERT3U(HDR_GET_LSIZE(hdr), !=, 0);
1623 size = HDR_GET_LSIZE(hdr);
1624 }
1625 return (size);
1626 }
1627
1628 static int
arc_hdr_authenticate(arc_buf_hdr_t * hdr,spa_t * spa,uint64_t dsobj)1629 arc_hdr_authenticate(arc_buf_hdr_t *hdr, spa_t *spa, uint64_t dsobj)
1630 {
1631 int ret;
1632 uint64_t csize;
1633 uint64_t lsize = HDR_GET_LSIZE(hdr);
1634 uint64_t psize = HDR_GET_PSIZE(hdr);
1635 void *tmpbuf = NULL;
1636 abd_t *abd = hdr->b_l1hdr.b_pabd;
1637
1638 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1639 ASSERT(HDR_AUTHENTICATED(hdr));
1640 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1641
1642 /*
1643 * The MAC is calculated on the compressed data that is stored on disk.
1644 * However, if compressed arc is disabled we will only have the
1645 * decompressed data available to us now. Compress it into a temporary
1646 * abd so we can verify the MAC. The performance overhead of this will
1647 * be relatively low, since most objects in an encrypted objset will
1648 * be encrypted (instead of authenticated) anyway.
1649 */
1650 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1651 !HDR_COMPRESSION_ENABLED(hdr)) {
1652 tmpbuf = zio_buf_alloc(lsize);
1653 abd = abd_get_from_buf(tmpbuf, lsize);
1654 abd_take_ownership_of_buf(abd, B_TRUE);
1655
1656 csize = zio_compress_data(HDR_GET_COMPRESS(hdr),
1657 hdr->b_l1hdr.b_pabd, tmpbuf, lsize);
1658 ASSERT3U(csize, <=, psize);
1659 abd_zero_off(abd, csize, psize - csize);
1660 }
1661
1662 /*
1663 * Authentication is best effort. We authenticate whenever the key is
1664 * available. If we succeed we clear ARC_FLAG_NOAUTH.
1665 */
1666 if (hdr->b_crypt_hdr.b_ot == DMU_OT_OBJSET) {
1667 ASSERT3U(HDR_GET_COMPRESS(hdr), ==, ZIO_COMPRESS_OFF);
1668 ASSERT3U(lsize, ==, psize);
1669 ret = spa_do_crypt_objset_mac_abd(B_FALSE, spa, dsobj, abd,
1670 psize, hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
1671 } else {
1672 ret = spa_do_crypt_mac_abd(B_FALSE, spa, dsobj, abd, psize,
1673 hdr->b_crypt_hdr.b_mac);
1674 }
1675
1676 if (ret == 0)
1677 arc_hdr_clear_flags(hdr, ARC_FLAG_NOAUTH);
1678 else if (ret != ENOENT)
1679 goto error;
1680
1681 if (tmpbuf != NULL)
1682 abd_free(abd);
1683
1684 return (0);
1685
1686 error:
1687 if (tmpbuf != NULL)
1688 abd_free(abd);
1689
1690 return (ret);
1691 }
1692
1693 /*
1694 * This function will take a header that only has raw encrypted data in
1695 * b_crypt_hdr.b_rabd and decrypt it into a new buffer which is stored in
1696 * b_l1hdr.b_pabd. If designated in the header flags, this function will
1697 * also decompress the data.
1698 */
1699 static int
arc_hdr_decrypt(arc_buf_hdr_t * hdr,spa_t * spa,const zbookmark_phys_t * zb)1700 arc_hdr_decrypt(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb)
1701 {
1702 int ret;
1703 abd_t *cabd = NULL;
1704 void *tmp = NULL;
1705 boolean_t no_crypt = B_FALSE;
1706 boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
1707
1708 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1709 ASSERT(HDR_ENCRYPTED(hdr));
1710
1711 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
1712
1713 ret = spa_do_crypt_abd(B_FALSE, spa, zb, hdr->b_crypt_hdr.b_ot,
1714 B_FALSE, bswap, hdr->b_crypt_hdr.b_salt, hdr->b_crypt_hdr.b_iv,
1715 hdr->b_crypt_hdr.b_mac, HDR_GET_PSIZE(hdr), hdr->b_l1hdr.b_pabd,
1716 hdr->b_crypt_hdr.b_rabd, &no_crypt);
1717 if (ret != 0)
1718 goto error;
1719
1720 if (no_crypt) {
1721 abd_copy(hdr->b_l1hdr.b_pabd, hdr->b_crypt_hdr.b_rabd,
1722 HDR_GET_PSIZE(hdr));
1723 }
1724
1725 /*
1726 * If this header has disabled arc compression but the b_pabd is
1727 * compressed after decrypting it, we need to decompress the newly
1728 * decrypted data.
1729 */
1730 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
1731 !HDR_COMPRESSION_ENABLED(hdr)) {
1732 /*
1733 * We want to make sure that we are correctly honoring the
1734 * zfs_abd_scatter_enabled setting, so we allocate an abd here
1735 * and then loan a buffer from it, rather than allocating a
1736 * linear buffer and wrapping it in an abd later.
1737 */
1738 cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr, B_TRUE);
1739 tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
1740
1741 ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
1742 hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
1743 HDR_GET_LSIZE(hdr));
1744 if (ret != 0) {
1745 abd_return_buf(cabd, tmp, arc_hdr_size(hdr));
1746 goto error;
1747 }
1748
1749 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
1750 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
1751 arc_hdr_size(hdr), hdr);
1752 hdr->b_l1hdr.b_pabd = cabd;
1753 }
1754
1755 return (0);
1756
1757 error:
1758 arc_hdr_free_pabd(hdr, B_FALSE);
1759 if (cabd != NULL)
1760 arc_free_data_buf(hdr, cabd, arc_hdr_size(hdr), hdr);
1761
1762 return (ret);
1763 }
1764
1765 /*
1766 * This function is called during arc_buf_fill() to prepare the header's
1767 * abd plaintext pointer for use. This involves authenticated protected
1768 * data and decrypting encrypted data into the plaintext abd.
1769 */
1770 static int
arc_fill_hdr_crypt(arc_buf_hdr_t * hdr,kmutex_t * hash_lock,spa_t * spa,const zbookmark_phys_t * zb,boolean_t noauth)1771 arc_fill_hdr_crypt(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, spa_t *spa,
1772 const zbookmark_phys_t *zb, boolean_t noauth)
1773 {
1774 int ret;
1775
1776 ASSERT(HDR_PROTECTED(hdr));
1777
1778 if (hash_lock != NULL)
1779 mutex_enter(hash_lock);
1780
1781 if (HDR_NOAUTH(hdr) && !noauth) {
1782 /*
1783 * The caller requested authenticated data but our data has
1784 * not been authenticated yet. Verify the MAC now if we can.
1785 */
1786 ret = arc_hdr_authenticate(hdr, spa, zb->zb_objset);
1787 if (ret != 0)
1788 goto error;
1789 } else if (HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd == NULL) {
1790 /*
1791 * If we only have the encrypted version of the data, but the
1792 * unencrypted version was requested we take this opportunity
1793 * to store the decrypted version in the header for future use.
1794 */
1795 ret = arc_hdr_decrypt(hdr, spa, zb);
1796 if (ret != 0)
1797 goto error;
1798 }
1799
1800 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1801
1802 if (hash_lock != NULL)
1803 mutex_exit(hash_lock);
1804
1805 return (0);
1806
1807 error:
1808 if (hash_lock != NULL)
1809 mutex_exit(hash_lock);
1810
1811 return (ret);
1812 }
1813
1814 /*
1815 * This function is used by the dbuf code to decrypt bonus buffers in place.
1816 * The dbuf code itself doesn't have any locking for decrypting a shared dnode
1817 * block, so we use the hash lock here to protect against concurrent calls to
1818 * arc_buf_fill().
1819 */
1820 /* ARGSUSED */
1821 static void
arc_buf_untransform_in_place(arc_buf_t * buf,kmutex_t * hash_lock)1822 arc_buf_untransform_in_place(arc_buf_t *buf, kmutex_t *hash_lock)
1823 {
1824 arc_buf_hdr_t *hdr = buf->b_hdr;
1825
1826 ASSERT(HDR_ENCRYPTED(hdr));
1827 ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
1828 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
1829 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
1830
1831 zio_crypt_copy_dnode_bonus(hdr->b_l1hdr.b_pabd, buf->b_data,
1832 arc_buf_size(buf));
1833 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
1834 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
1835 hdr->b_crypt_hdr.b_ebufcnt -= 1;
1836 }
1837
1838 /*
1839 * Given a buf that has a data buffer attached to it, this function will
1840 * efficiently fill the buf with data of the specified compression setting from
1841 * the hdr and update the hdr's b_freeze_cksum if necessary. If the buf and hdr
1842 * are already sharing a data buf, no copy is performed.
1843 *
1844 * If the buf is marked as compressed but uncompressed data was requested, this
1845 * will allocate a new data buffer for the buf, remove that flag, and fill the
1846 * buf with uncompressed data. You can't request a compressed buf on a hdr with
1847 * uncompressed data, and (since we haven't added support for it yet) if you
1848 * want compressed data your buf must already be marked as compressed and have
1849 * the correct-sized data buffer.
1850 */
1851 static int
arc_buf_fill(arc_buf_t * buf,spa_t * spa,const zbookmark_phys_t * zb,arc_fill_flags_t flags)1852 arc_buf_fill(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
1853 arc_fill_flags_t flags)
1854 {
1855 int error = 0;
1856 arc_buf_hdr_t *hdr = buf->b_hdr;
1857 boolean_t hdr_compressed =
1858 (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
1859 boolean_t compressed = (flags & ARC_FILL_COMPRESSED) != 0;
1860 boolean_t encrypted = (flags & ARC_FILL_ENCRYPTED) != 0;
1861 dmu_object_byteswap_t bswap = hdr->b_l1hdr.b_byteswap;
1862 kmutex_t *hash_lock = (flags & ARC_FILL_LOCKED) ? NULL : HDR_LOCK(hdr);
1863
1864 ASSERT3P(buf->b_data, !=, NULL);
1865 IMPLY(compressed, hdr_compressed || ARC_BUF_ENCRYPTED(buf));
1866 IMPLY(compressed, ARC_BUF_COMPRESSED(buf));
1867 IMPLY(encrypted, HDR_ENCRYPTED(hdr));
1868 IMPLY(encrypted, ARC_BUF_ENCRYPTED(buf));
1869 IMPLY(encrypted, ARC_BUF_COMPRESSED(buf));
1870 IMPLY(encrypted, !ARC_BUF_SHARED(buf));
1871
1872 /*
1873 * If the caller wanted encrypted data we just need to copy it from
1874 * b_rabd and potentially byteswap it. We won't be able to do any
1875 * further transforms on it.
1876 */
1877 if (encrypted) {
1878 ASSERT(HDR_HAS_RABD(hdr));
1879 abd_copy_to_buf(buf->b_data, hdr->b_crypt_hdr.b_rabd,
1880 HDR_GET_PSIZE(hdr));
1881 goto byteswap;
1882 }
1883
1884 /*
1885 * Adjust encrypted and authenticated headers to accomodate
1886 * the request if needed. Dnode blocks (ARC_FILL_IN_PLACE) are
1887 * allowed to fail decryption due to keys not being loaded
1888 * without being marked as an IO error.
1889 */
1890 if (HDR_PROTECTED(hdr)) {
1891 error = arc_fill_hdr_crypt(hdr, hash_lock, spa,
1892 zb, !!(flags & ARC_FILL_NOAUTH));
1893 if (error == EACCES && (flags & ARC_FILL_IN_PLACE) != 0) {
1894 return (error);
1895 } else if (error != 0) {
1896 if (hash_lock != NULL)
1897 mutex_enter(hash_lock);
1898 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
1899 if (hash_lock != NULL)
1900 mutex_exit(hash_lock);
1901 return (error);
1902 }
1903 }
1904
1905 /*
1906 * There is a special case here for dnode blocks which are
1907 * decrypting their bonus buffers. These blocks may request to
1908 * be decrypted in-place. This is necessary because there may
1909 * be many dnodes pointing into this buffer and there is
1910 * currently no method to synchronize replacing the backing
1911 * b_data buffer and updating all of the pointers. Here we use
1912 * the hash lock to ensure there are no races. If the need
1913 * arises for other types to be decrypted in-place, they must
1914 * add handling here as well.
1915 */
1916 if ((flags & ARC_FILL_IN_PLACE) != 0) {
1917 ASSERT(!hdr_compressed);
1918 ASSERT(!compressed);
1919 ASSERT(!encrypted);
1920
1921 if (HDR_ENCRYPTED(hdr) && ARC_BUF_ENCRYPTED(buf)) {
1922 ASSERT3U(hdr->b_crypt_hdr.b_ot, ==, DMU_OT_DNODE);
1923
1924 if (hash_lock != NULL)
1925 mutex_enter(hash_lock);
1926 arc_buf_untransform_in_place(buf, hash_lock);
1927 if (hash_lock != NULL)
1928 mutex_exit(hash_lock);
1929
1930 /* Compute the hdr's checksum if necessary */
1931 arc_cksum_compute(buf);
1932 }
1933
1934 return (0);
1935 }
1936
1937 if (hdr_compressed == compressed) {
1938 if (!arc_buf_is_shared(buf)) {
1939 abd_copy_to_buf(buf->b_data, hdr->b_l1hdr.b_pabd,
1940 arc_buf_size(buf));
1941 }
1942 } else {
1943 ASSERT(hdr_compressed);
1944 ASSERT(!compressed);
1945 ASSERT3U(HDR_GET_LSIZE(hdr), !=, HDR_GET_PSIZE(hdr));
1946
1947 /*
1948 * If the buf is sharing its data with the hdr, unlink it and
1949 * allocate a new data buffer for the buf.
1950 */
1951 if (arc_buf_is_shared(buf)) {
1952 ASSERT(ARC_BUF_COMPRESSED(buf));
1953
1954 /* We need to give the buf its own b_data */
1955 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
1956 buf->b_data =
1957 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
1958 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
1959
1960 /* Previously overhead was 0; just add new overhead */
1961 ARCSTAT_INCR(arcstat_overhead_size, HDR_GET_LSIZE(hdr));
1962 } else if (ARC_BUF_COMPRESSED(buf)) {
1963 /* We need to reallocate the buf's b_data */
1964 arc_free_data_buf(hdr, buf->b_data, HDR_GET_PSIZE(hdr),
1965 buf);
1966 buf->b_data =
1967 arc_get_data_buf(hdr, HDR_GET_LSIZE(hdr), buf);
1968
1969 /* We increased the size of b_data; update overhead */
1970 ARCSTAT_INCR(arcstat_overhead_size,
1971 HDR_GET_LSIZE(hdr) - HDR_GET_PSIZE(hdr));
1972 }
1973
1974 /*
1975 * Regardless of the buf's previous compression settings, it
1976 * should not be compressed at the end of this function.
1977 */
1978 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
1979
1980 /*
1981 * Try copying the data from another buf which already has a
1982 * decompressed version. If that's not possible, it's time to
1983 * bite the bullet and decompress the data from the hdr.
1984 */
1985 if (arc_buf_try_copy_decompressed_data(buf)) {
1986 /* Skip byteswapping and checksumming (already done) */
1987 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, !=, NULL);
1988 return (0);
1989 } else {
1990 error = zio_decompress_data(HDR_GET_COMPRESS(hdr),
1991 hdr->b_l1hdr.b_pabd, buf->b_data,
1992 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
1993
1994 /*
1995 * Absent hardware errors or software bugs, this should
1996 * be impossible, but log it anyway so we can debug it.
1997 */
1998 if (error != 0) {
1999 zfs_dbgmsg(
2000 "hdr %p, compress %d, psize %d, lsize %d",
2001 hdr, arc_hdr_get_compress(hdr),
2002 HDR_GET_PSIZE(hdr), HDR_GET_LSIZE(hdr));
2003 if (hash_lock != NULL)
2004 mutex_enter(hash_lock);
2005 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
2006 if (hash_lock != NULL)
2007 mutex_exit(hash_lock);
2008 return (SET_ERROR(EIO));
2009 }
2010 }
2011 }
2012
2013 byteswap:
2014 /* Byteswap the buf's data if necessary */
2015 if (bswap != DMU_BSWAP_NUMFUNCS) {
2016 ASSERT(!HDR_SHARED_DATA(hdr));
2017 ASSERT3U(bswap, <, DMU_BSWAP_NUMFUNCS);
2018 dmu_ot_byteswap[bswap].ob_func(buf->b_data, HDR_GET_LSIZE(hdr));
2019 }
2020
2021 /* Compute the hdr's checksum if necessary */
2022 arc_cksum_compute(buf);
2023
2024 return (0);
2025 }
2026
2027 /*
2028 * If this function is being called to decrypt an encrypted buffer or verify an
2029 * authenticated one, the key must be loaded and a mapping must be made
2030 * available in the keystore via spa_keystore_create_mapping() or one of its
2031 * callers.
2032 */
2033 int
arc_untransform(arc_buf_t * buf,spa_t * spa,const zbookmark_phys_t * zb,boolean_t in_place)2034 arc_untransform(arc_buf_t *buf, spa_t *spa, const zbookmark_phys_t *zb,
2035 boolean_t in_place)
2036 {
2037 int ret;
2038 arc_fill_flags_t flags = 0;
2039
2040 if (in_place)
2041 flags |= ARC_FILL_IN_PLACE;
2042
2043 ret = arc_buf_fill(buf, spa, zb, flags);
2044 if (ret == ECKSUM) {
2045 /*
2046 * Convert authentication and decryption errors to EIO
2047 * (and generate an ereport) before leaving the ARC.
2048 */
2049 ret = SET_ERROR(EIO);
2050 spa_log_error(spa, zb);
2051 (void) zfs_ereport_post(FM_EREPORT_ZFS_AUTHENTICATION,
2052 spa, NULL, zb, NULL, 0, 0);
2053 }
2054
2055 return (ret);
2056 }
2057
2058 /*
2059 * Increment the amount of evictable space in the arc_state_t's refcount.
2060 * We account for the space used by the hdr and the arc buf individually
2061 * so that we can add and remove them from the refcount individually.
2062 */
2063 static void
arc_evictable_space_increment(arc_buf_hdr_t * hdr,arc_state_t * state)2064 arc_evictable_space_increment(arc_buf_hdr_t *hdr, arc_state_t *state)
2065 {
2066 arc_buf_contents_t type = arc_buf_type(hdr);
2067
2068 ASSERT(HDR_HAS_L1HDR(hdr));
2069
2070 if (GHOST_STATE(state)) {
2071 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2072 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2073 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2074 ASSERT(!HDR_HAS_RABD(hdr));
2075 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2076 HDR_GET_LSIZE(hdr), hdr);
2077 return;
2078 }
2079
2080 ASSERT(!GHOST_STATE(state));
2081 if (hdr->b_l1hdr.b_pabd != NULL) {
2082 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2083 arc_hdr_size(hdr), hdr);
2084 }
2085 if (HDR_HAS_RABD(hdr)) {
2086 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2087 HDR_GET_PSIZE(hdr), hdr);
2088 }
2089 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2090 buf = buf->b_next) {
2091 if (arc_buf_is_shared(buf))
2092 continue;
2093 (void) zfs_refcount_add_many(&state->arcs_esize[type],
2094 arc_buf_size(buf), buf);
2095 }
2096 }
2097
2098 /*
2099 * Decrement the amount of evictable space in the arc_state_t's refcount.
2100 * We account for the space used by the hdr and the arc buf individually
2101 * so that we can add and remove them from the refcount individually.
2102 */
2103 static void
arc_evictable_space_decrement(arc_buf_hdr_t * hdr,arc_state_t * state)2104 arc_evictable_space_decrement(arc_buf_hdr_t *hdr, arc_state_t *state)
2105 {
2106 arc_buf_contents_t type = arc_buf_type(hdr);
2107
2108 ASSERT(HDR_HAS_L1HDR(hdr));
2109
2110 if (GHOST_STATE(state)) {
2111 ASSERT0(hdr->b_l1hdr.b_bufcnt);
2112 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2113 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2114 ASSERT(!HDR_HAS_RABD(hdr));
2115 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2116 HDR_GET_LSIZE(hdr), hdr);
2117 return;
2118 }
2119
2120 ASSERT(!GHOST_STATE(state));
2121 if (hdr->b_l1hdr.b_pabd != NULL) {
2122 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2123 arc_hdr_size(hdr), hdr);
2124 }
2125 if (HDR_HAS_RABD(hdr)) {
2126 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2127 HDR_GET_PSIZE(hdr), hdr);
2128 }
2129 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2130 buf = buf->b_next) {
2131 if (arc_buf_is_shared(buf))
2132 continue;
2133 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2134 arc_buf_size(buf), buf);
2135 }
2136 }
2137
2138 /*
2139 * Add a reference to this hdr indicating that someone is actively
2140 * referencing that memory. When the refcount transitions from 0 to 1,
2141 * we remove it from the respective arc_state_t list to indicate that
2142 * it is not evictable.
2143 */
2144 static void
add_reference(arc_buf_hdr_t * hdr,void * tag)2145 add_reference(arc_buf_hdr_t *hdr, void *tag)
2146 {
2147 ASSERT(HDR_HAS_L1HDR(hdr));
2148 if (!HDR_EMPTY(hdr) && !MUTEX_HELD(HDR_LOCK(hdr))) {
2149 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
2150 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2151 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2152 }
2153
2154 arc_state_t *state = hdr->b_l1hdr.b_state;
2155
2156 if ((zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag) == 1) &&
2157 (state != arc_anon)) {
2158 /* We don't use the L2-only state list. */
2159 if (state != arc_l2c_only) {
2160 multilist_remove(state->arcs_list[arc_buf_type(hdr)],
2161 hdr);
2162 arc_evictable_space_decrement(hdr, state);
2163 }
2164 /* remove the prefetch flag if we get a reference */
2165 if (HDR_HAS_L2HDR(hdr))
2166 l2arc_hdr_arcstats_decrement_state(hdr);
2167 arc_hdr_clear_flags(hdr, ARC_FLAG_PREFETCH);
2168 if (HDR_HAS_L2HDR(hdr))
2169 l2arc_hdr_arcstats_increment_state(hdr);
2170 }
2171 }
2172
2173 /*
2174 * Remove a reference from this hdr. When the reference transitions from
2175 * 1 to 0 and we're not anonymous, then we add this hdr to the arc_state_t's
2176 * list making it eligible for eviction.
2177 */
2178 static int
remove_reference(arc_buf_hdr_t * hdr,kmutex_t * hash_lock,void * tag)2179 remove_reference(arc_buf_hdr_t *hdr, kmutex_t *hash_lock, void *tag)
2180 {
2181 int cnt;
2182 arc_state_t *state = hdr->b_l1hdr.b_state;
2183
2184 ASSERT(HDR_HAS_L1HDR(hdr));
2185 ASSERT(state == arc_anon || MUTEX_HELD(hash_lock));
2186 ASSERT(!GHOST_STATE(state));
2187
2188 /*
2189 * arc_l2c_only counts as a ghost state so we don't need to explicitly
2190 * check to prevent usage of the arc_l2c_only list.
2191 */
2192 if (((cnt = zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag)) == 0) &&
2193 (state != arc_anon)) {
2194 multilist_insert(state->arcs_list[arc_buf_type(hdr)], hdr);
2195 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
2196 arc_evictable_space_increment(hdr, state);
2197 }
2198 return (cnt);
2199 }
2200
2201 /*
2202 * Move the supplied buffer to the indicated state. The hash lock
2203 * for the buffer must be held by the caller.
2204 */
2205 static void
arc_change_state(arc_state_t * new_state,arc_buf_hdr_t * hdr,kmutex_t * hash_lock)2206 arc_change_state(arc_state_t *new_state, arc_buf_hdr_t *hdr,
2207 kmutex_t *hash_lock)
2208 {
2209 arc_state_t *old_state;
2210 int64_t refcnt;
2211 uint32_t bufcnt;
2212 boolean_t update_old, update_new;
2213 arc_buf_contents_t buftype = arc_buf_type(hdr);
2214
2215 /*
2216 * We almost always have an L1 hdr here, since we call arc_hdr_realloc()
2217 * in arc_read() when bringing a buffer out of the L2ARC. However, the
2218 * L1 hdr doesn't always exist when we change state to arc_anon before
2219 * destroying a header, in which case reallocating to add the L1 hdr is
2220 * pointless.
2221 */
2222 if (HDR_HAS_L1HDR(hdr)) {
2223 old_state = hdr->b_l1hdr.b_state;
2224 refcnt = zfs_refcount_count(&hdr->b_l1hdr.b_refcnt);
2225 bufcnt = hdr->b_l1hdr.b_bufcnt;
2226
2227 update_old = (bufcnt > 0 || hdr->b_l1hdr.b_pabd != NULL ||
2228 HDR_HAS_RABD(hdr));
2229 } else {
2230 old_state = arc_l2c_only;
2231 refcnt = 0;
2232 bufcnt = 0;
2233 update_old = B_FALSE;
2234 }
2235 update_new = update_old;
2236
2237 ASSERT(MUTEX_HELD(hash_lock));
2238 ASSERT3P(new_state, !=, old_state);
2239 ASSERT(!GHOST_STATE(new_state) || bufcnt == 0);
2240 ASSERT(old_state != arc_anon || bufcnt <= 1);
2241
2242 /*
2243 * If this buffer is evictable, transfer it from the
2244 * old state list to the new state list.
2245 */
2246 if (refcnt == 0) {
2247 if (old_state != arc_anon && old_state != arc_l2c_only) {
2248 ASSERT(HDR_HAS_L1HDR(hdr));
2249 multilist_remove(old_state->arcs_list[buftype], hdr);
2250
2251 if (GHOST_STATE(old_state)) {
2252 ASSERT0(bufcnt);
2253 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2254 update_old = B_TRUE;
2255 }
2256 arc_evictable_space_decrement(hdr, old_state);
2257 }
2258 if (new_state != arc_anon && new_state != arc_l2c_only) {
2259
2260 /*
2261 * An L1 header always exists here, since if we're
2262 * moving to some L1-cached state (i.e. not l2c_only or
2263 * anonymous), we realloc the header to add an L1hdr
2264 * beforehand.
2265 */
2266 ASSERT(HDR_HAS_L1HDR(hdr));
2267 multilist_insert(new_state->arcs_list[buftype], hdr);
2268
2269 if (GHOST_STATE(new_state)) {
2270 ASSERT0(bufcnt);
2271 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
2272 update_new = B_TRUE;
2273 }
2274 arc_evictable_space_increment(hdr, new_state);
2275 }
2276 }
2277
2278 ASSERT(!HDR_EMPTY(hdr));
2279 if (new_state == arc_anon && HDR_IN_HASH_TABLE(hdr))
2280 buf_hash_remove(hdr);
2281
2282 /* adjust state sizes (ignore arc_l2c_only) */
2283
2284 if (update_new && new_state != arc_l2c_only) {
2285 ASSERT(HDR_HAS_L1HDR(hdr));
2286 if (GHOST_STATE(new_state)) {
2287 ASSERT0(bufcnt);
2288
2289 /*
2290 * When moving a header to a ghost state, we first
2291 * remove all arc buffers. Thus, we'll have a
2292 * bufcnt of zero, and no arc buffer to use for
2293 * the reference. As a result, we use the arc
2294 * header pointer for the reference.
2295 */
2296 (void) zfs_refcount_add_many(&new_state->arcs_size,
2297 HDR_GET_LSIZE(hdr), hdr);
2298 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2299 ASSERT(!HDR_HAS_RABD(hdr));
2300 } else {
2301 uint32_t buffers = 0;
2302
2303 /*
2304 * Each individual buffer holds a unique reference,
2305 * thus we must remove each of these references one
2306 * at a time.
2307 */
2308 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2309 buf = buf->b_next) {
2310 ASSERT3U(bufcnt, !=, 0);
2311 buffers++;
2312
2313 /*
2314 * When the arc_buf_t is sharing the data
2315 * block with the hdr, the owner of the
2316 * reference belongs to the hdr. Only
2317 * add to the refcount if the arc_buf_t is
2318 * not shared.
2319 */
2320 if (arc_buf_is_shared(buf))
2321 continue;
2322
2323 (void) zfs_refcount_add_many(
2324 &new_state->arcs_size,
2325 arc_buf_size(buf), buf);
2326 }
2327 ASSERT3U(bufcnt, ==, buffers);
2328
2329 if (hdr->b_l1hdr.b_pabd != NULL) {
2330 (void) zfs_refcount_add_many(
2331 &new_state->arcs_size,
2332 arc_hdr_size(hdr), hdr);
2333 }
2334
2335 if (HDR_HAS_RABD(hdr)) {
2336 (void) zfs_refcount_add_many(
2337 &new_state->arcs_size,
2338 HDR_GET_PSIZE(hdr), hdr);
2339 }
2340 }
2341 }
2342
2343 if (update_old && old_state != arc_l2c_only) {
2344 ASSERT(HDR_HAS_L1HDR(hdr));
2345 if (GHOST_STATE(old_state)) {
2346 ASSERT0(bufcnt);
2347 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2348 ASSERT(!HDR_HAS_RABD(hdr));
2349
2350 /*
2351 * When moving a header off of a ghost state,
2352 * the header will not contain any arc buffers.
2353 * We use the arc header pointer for the reference
2354 * which is exactly what we did when we put the
2355 * header on the ghost state.
2356 */
2357
2358 (void) zfs_refcount_remove_many(&old_state->arcs_size,
2359 HDR_GET_LSIZE(hdr), hdr);
2360 } else {
2361 uint32_t buffers = 0;
2362
2363 /*
2364 * Each individual buffer holds a unique reference,
2365 * thus we must remove each of these references one
2366 * at a time.
2367 */
2368 for (arc_buf_t *buf = hdr->b_l1hdr.b_buf; buf != NULL;
2369 buf = buf->b_next) {
2370 ASSERT3U(bufcnt, !=, 0);
2371 buffers++;
2372
2373 /*
2374 * When the arc_buf_t is sharing the data
2375 * block with the hdr, the owner of the
2376 * reference belongs to the hdr. Only
2377 * add to the refcount if the arc_buf_t is
2378 * not shared.
2379 */
2380 if (arc_buf_is_shared(buf))
2381 continue;
2382
2383 (void) zfs_refcount_remove_many(
2384 &old_state->arcs_size, arc_buf_size(buf),
2385 buf);
2386 }
2387 ASSERT3U(bufcnt, ==, buffers);
2388 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
2389 HDR_HAS_RABD(hdr));
2390
2391 if (hdr->b_l1hdr.b_pabd != NULL) {
2392 (void) zfs_refcount_remove_many(
2393 &old_state->arcs_size, arc_hdr_size(hdr),
2394 hdr);
2395 }
2396
2397 if (HDR_HAS_RABD(hdr)) {
2398 (void) zfs_refcount_remove_many(
2399 &old_state->arcs_size, HDR_GET_PSIZE(hdr),
2400 hdr);
2401 }
2402 }
2403 }
2404
2405 if (HDR_HAS_L1HDR(hdr)) {
2406 hdr->b_l1hdr.b_state = new_state;
2407
2408 if (HDR_HAS_L2HDR(hdr) && new_state != arc_l2c_only) {
2409 l2arc_hdr_arcstats_decrement_state(hdr);
2410 hdr->b_l2hdr.b_arcs_state = new_state->arcs_state;
2411 l2arc_hdr_arcstats_increment_state(hdr);
2412 }
2413 }
2414
2415 /*
2416 * L2 headers should never be on the L2 state list since they don't
2417 * have L1 headers allocated.
2418 */
2419 ASSERT(multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_DATA]) &&
2420 multilist_is_empty(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]));
2421 }
2422
2423 void
arc_space_consume(uint64_t space,arc_space_type_t type)2424 arc_space_consume(uint64_t space, arc_space_type_t type)
2425 {
2426 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2427
2428 switch (type) {
2429 case ARC_SPACE_DATA:
2430 aggsum_add(&astat_data_size, space);
2431 break;
2432 case ARC_SPACE_META:
2433 aggsum_add(&astat_metadata_size, space);
2434 break;
2435 case ARC_SPACE_OTHER:
2436 aggsum_add(&astat_other_size, space);
2437 break;
2438 case ARC_SPACE_HDRS:
2439 aggsum_add(&astat_hdr_size, space);
2440 break;
2441 case ARC_SPACE_L2HDRS:
2442 aggsum_add(&astat_l2_hdr_size, space);
2443 break;
2444 }
2445
2446 if (type != ARC_SPACE_DATA)
2447 aggsum_add(&arc_meta_used, space);
2448
2449 aggsum_add(&arc_size, space);
2450 }
2451
2452 void
arc_space_return(uint64_t space,arc_space_type_t type)2453 arc_space_return(uint64_t space, arc_space_type_t type)
2454 {
2455 ASSERT(type >= 0 && type < ARC_SPACE_NUMTYPES);
2456
2457 switch (type) {
2458 case ARC_SPACE_DATA:
2459 aggsum_add(&astat_data_size, -space);
2460 break;
2461 case ARC_SPACE_META:
2462 aggsum_add(&astat_metadata_size, -space);
2463 break;
2464 case ARC_SPACE_OTHER:
2465 aggsum_add(&astat_other_size, -space);
2466 break;
2467 case ARC_SPACE_HDRS:
2468 aggsum_add(&astat_hdr_size, -space);
2469 break;
2470 case ARC_SPACE_L2HDRS:
2471 aggsum_add(&astat_l2_hdr_size, -space);
2472 break;
2473 }
2474
2475 if (type != ARC_SPACE_DATA) {
2476 ASSERT(aggsum_compare(&arc_meta_used, space) >= 0);
2477 /*
2478 * We use the upper bound here rather than the precise value
2479 * because the arc_meta_max value doesn't need to be
2480 * precise. It's only consumed by humans via arcstats.
2481 */
2482 if (arc_meta_max < aggsum_upper_bound(&arc_meta_used))
2483 arc_meta_max = aggsum_upper_bound(&arc_meta_used);
2484 aggsum_add(&arc_meta_used, -space);
2485 }
2486
2487 ASSERT(aggsum_compare(&arc_size, space) >= 0);
2488 aggsum_add(&arc_size, -space);
2489 }
2490
2491 /*
2492 * Given a hdr and a buf, returns whether that buf can share its b_data buffer
2493 * with the hdr's b_pabd.
2494 */
2495 static boolean_t
arc_can_share(arc_buf_hdr_t * hdr,arc_buf_t * buf)2496 arc_can_share(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2497 {
2498 /*
2499 * The criteria for sharing a hdr's data are:
2500 * 1. the buffer is not encrypted
2501 * 2. the hdr's compression matches the buf's compression
2502 * 3. the hdr doesn't need to be byteswapped
2503 * 4. the hdr isn't already being shared
2504 * 5. the buf is either compressed or it is the last buf in the hdr list
2505 *
2506 * Criterion #5 maintains the invariant that shared uncompressed
2507 * bufs must be the final buf in the hdr's b_buf list. Reading this, you
2508 * might ask, "if a compressed buf is allocated first, won't that be the
2509 * last thing in the list?", but in that case it's impossible to create
2510 * a shared uncompressed buf anyway (because the hdr must be compressed
2511 * to have the compressed buf). You might also think that #3 is
2512 * sufficient to make this guarantee, however it's possible
2513 * (specifically in the rare L2ARC write race mentioned in
2514 * arc_buf_alloc_impl()) there will be an existing uncompressed buf that
2515 * is sharable, but wasn't at the time of its allocation. Rather than
2516 * allow a new shared uncompressed buf to be created and then shuffle
2517 * the list around to make it the last element, this simply disallows
2518 * sharing if the new buf isn't the first to be added.
2519 */
2520 ASSERT3P(buf->b_hdr, ==, hdr);
2521 boolean_t hdr_compressed = arc_hdr_get_compress(hdr) !=
2522 ZIO_COMPRESS_OFF;
2523 boolean_t buf_compressed = ARC_BUF_COMPRESSED(buf) != 0;
2524 return (!ARC_BUF_ENCRYPTED(buf) &&
2525 buf_compressed == hdr_compressed &&
2526 hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS &&
2527 !HDR_SHARED_DATA(hdr) &&
2528 (ARC_BUF_LAST(buf) || ARC_BUF_COMPRESSED(buf)));
2529 }
2530
2531 /*
2532 * Allocate a buf for this hdr. If you care about the data that's in the hdr,
2533 * or if you want a compressed buffer, pass those flags in. Returns 0 if the
2534 * copy was made successfully, or an error code otherwise.
2535 */
2536 static int
arc_buf_alloc_impl(arc_buf_hdr_t * hdr,spa_t * spa,const zbookmark_phys_t * zb,void * tag,boolean_t encrypted,boolean_t compressed,boolean_t noauth,boolean_t fill,arc_buf_t ** ret)2537 arc_buf_alloc_impl(arc_buf_hdr_t *hdr, spa_t *spa, const zbookmark_phys_t *zb,
2538 void *tag, boolean_t encrypted, boolean_t compressed, boolean_t noauth,
2539 boolean_t fill, arc_buf_t **ret)
2540 {
2541 arc_buf_t *buf;
2542 arc_fill_flags_t flags = ARC_FILL_LOCKED;
2543
2544 ASSERT(HDR_HAS_L1HDR(hdr));
2545 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
2546 VERIFY(hdr->b_type == ARC_BUFC_DATA ||
2547 hdr->b_type == ARC_BUFC_METADATA);
2548 ASSERT3P(ret, !=, NULL);
2549 ASSERT3P(*ret, ==, NULL);
2550 IMPLY(encrypted, compressed);
2551
2552 buf = *ret = kmem_cache_alloc(buf_cache, KM_PUSHPAGE);
2553 buf->b_hdr = hdr;
2554 buf->b_data = NULL;
2555 buf->b_next = hdr->b_l1hdr.b_buf;
2556 buf->b_flags = 0;
2557
2558 add_reference(hdr, tag);
2559
2560 /*
2561 * We're about to change the hdr's b_flags. We must either
2562 * hold the hash_lock or be undiscoverable.
2563 */
2564 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2565
2566 /*
2567 * Only honor requests for compressed bufs if the hdr is actually
2568 * compressed. This must be overriden if the buffer is encrypted since
2569 * encrypted buffers cannot be decompressed.
2570 */
2571 if (encrypted) {
2572 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2573 buf->b_flags |= ARC_BUF_FLAG_ENCRYPTED;
2574 flags |= ARC_FILL_COMPRESSED | ARC_FILL_ENCRYPTED;
2575 } else if (compressed &&
2576 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
2577 buf->b_flags |= ARC_BUF_FLAG_COMPRESSED;
2578 flags |= ARC_FILL_COMPRESSED;
2579 }
2580
2581 if (noauth) {
2582 ASSERT0(encrypted);
2583 flags |= ARC_FILL_NOAUTH;
2584 }
2585
2586 /*
2587 * If the hdr's data can be shared then we share the data buffer and
2588 * set the appropriate bit in the hdr's b_flags to indicate the hdr is
2589 * allocate a new buffer to store the buf's data.
2590 *
2591 * There are two additional restrictions here because we're sharing
2592 * hdr -> buf instead of the usual buf -> hdr. First, the hdr can't be
2593 * actively involved in an L2ARC write, because if this buf is used by
2594 * an arc_write() then the hdr's data buffer will be released when the
2595 * write completes, even though the L2ARC write might still be using it.
2596 * Second, the hdr's ABD must be linear so that the buf's user doesn't
2597 * need to be ABD-aware.
2598 */
2599 boolean_t can_share = arc_can_share(hdr, buf) && !HDR_L2_WRITING(hdr) &&
2600 hdr->b_l1hdr.b_pabd != NULL && abd_is_linear(hdr->b_l1hdr.b_pabd);
2601
2602 /* Set up b_data and sharing */
2603 if (can_share) {
2604 buf->b_data = abd_to_buf(hdr->b_l1hdr.b_pabd);
2605 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2606 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2607 } else {
2608 buf->b_data =
2609 arc_get_data_buf(hdr, arc_buf_size(buf), buf);
2610 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2611 }
2612 VERIFY3P(buf->b_data, !=, NULL);
2613
2614 hdr->b_l1hdr.b_buf = buf;
2615 hdr->b_l1hdr.b_bufcnt += 1;
2616 if (encrypted)
2617 hdr->b_crypt_hdr.b_ebufcnt += 1;
2618
2619 /*
2620 * If the user wants the data from the hdr, we need to either copy or
2621 * decompress the data.
2622 */
2623 if (fill) {
2624 ASSERT3P(zb, !=, NULL);
2625 return (arc_buf_fill(buf, spa, zb, flags));
2626 }
2627
2628 return (0);
2629 }
2630
2631 static char *arc_onloan_tag = "onloan";
2632
2633 static inline void
arc_loaned_bytes_update(int64_t delta)2634 arc_loaned_bytes_update(int64_t delta)
2635 {
2636 atomic_add_64(&arc_loaned_bytes, delta);
2637
2638 /* assert that it did not wrap around */
2639 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
2640 }
2641
2642 /*
2643 * Loan out an anonymous arc buffer. Loaned buffers are not counted as in
2644 * flight data by arc_tempreserve_space() until they are "returned". Loaned
2645 * buffers must be returned to the arc before they can be used by the DMU or
2646 * freed.
2647 */
2648 arc_buf_t *
arc_loan_buf(spa_t * spa,boolean_t is_metadata,int size)2649 arc_loan_buf(spa_t *spa, boolean_t is_metadata, int size)
2650 {
2651 arc_buf_t *buf = arc_alloc_buf(spa, arc_onloan_tag,
2652 is_metadata ? ARC_BUFC_METADATA : ARC_BUFC_DATA, size);
2653
2654 arc_loaned_bytes_update(arc_buf_size(buf));
2655
2656 return (buf);
2657 }
2658
2659 arc_buf_t *
arc_loan_compressed_buf(spa_t * spa,uint64_t psize,uint64_t lsize,enum zio_compress compression_type)2660 arc_loan_compressed_buf(spa_t *spa, uint64_t psize, uint64_t lsize,
2661 enum zio_compress compression_type)
2662 {
2663 arc_buf_t *buf = arc_alloc_compressed_buf(spa, arc_onloan_tag,
2664 psize, lsize, compression_type);
2665
2666 arc_loaned_bytes_update(arc_buf_size(buf));
2667
2668 return (buf);
2669 }
2670
2671 arc_buf_t *
arc_loan_raw_buf(spa_t * spa,uint64_t dsobj,boolean_t byteorder,const uint8_t * salt,const uint8_t * iv,const uint8_t * mac,dmu_object_type_t ot,uint64_t psize,uint64_t lsize,enum zio_compress compression_type)2672 arc_loan_raw_buf(spa_t *spa, uint64_t dsobj, boolean_t byteorder,
2673 const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
2674 dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
2675 enum zio_compress compression_type)
2676 {
2677 arc_buf_t *buf = arc_alloc_raw_buf(spa, arc_onloan_tag, dsobj,
2678 byteorder, salt, iv, mac, ot, psize, lsize, compression_type);
2679
2680 atomic_add_64(&arc_loaned_bytes, psize);
2681 return (buf);
2682 }
2683
2684 /*
2685 * Performance tuning of L2ARC persistence:
2686 *
2687 * l2arc_rebuild_enabled : A ZFS module parameter that controls whether adding
2688 * an L2ARC device (either at pool import or later) will attempt
2689 * to rebuild L2ARC buffer contents.
2690 * l2arc_rebuild_blocks_min_l2size : A ZFS module parameter that controls
2691 * whether log blocks are written to the L2ARC device. If the L2ARC
2692 * device is less than 1GB, the amount of data l2arc_evict()
2693 * evicts is significant compared to the amount of restored L2ARC
2694 * data. In this case do not write log blocks in L2ARC in order
2695 * not to waste space.
2696 */
2697 int l2arc_rebuild_enabled = B_TRUE;
2698 unsigned long l2arc_rebuild_blocks_min_l2size = 1024 * 1024 * 1024;
2699
2700 /* L2ARC persistence rebuild control routines. */
2701 void l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen);
2702 static void l2arc_dev_rebuild_start(l2arc_dev_t *dev);
2703 static int l2arc_rebuild(l2arc_dev_t *dev);
2704
2705 /* L2ARC persistence read I/O routines. */
2706 static int l2arc_dev_hdr_read(l2arc_dev_t *dev);
2707 static int l2arc_log_blk_read(l2arc_dev_t *dev,
2708 const l2arc_log_blkptr_t *this_lp, const l2arc_log_blkptr_t *next_lp,
2709 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
2710 zio_t *this_io, zio_t **next_io);
2711 static zio_t *l2arc_log_blk_fetch(vdev_t *vd,
2712 const l2arc_log_blkptr_t *lp, l2arc_log_blk_phys_t *lb);
2713 static void l2arc_log_blk_fetch_abort(zio_t *zio);
2714
2715 /* L2ARC persistence block restoration routines. */
2716 static void l2arc_log_blk_restore(l2arc_dev_t *dev,
2717 const l2arc_log_blk_phys_t *lb, uint64_t lb_asize);
2718 static void l2arc_hdr_restore(const l2arc_log_ent_phys_t *le,
2719 l2arc_dev_t *dev);
2720
2721 /* L2ARC persistence write I/O routines. */
2722 static void l2arc_dev_hdr_update(l2arc_dev_t *dev);
2723 static void l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio,
2724 l2arc_write_callback_t *cb);
2725
2726 /* L2ARC persistence auxilliary routines. */
2727 boolean_t l2arc_log_blkptr_valid(l2arc_dev_t *dev,
2728 const l2arc_log_blkptr_t *lbp);
2729 static boolean_t l2arc_log_blk_insert(l2arc_dev_t *dev,
2730 const arc_buf_hdr_t *ab);
2731 boolean_t l2arc_range_check_overlap(uint64_t bottom,
2732 uint64_t top, uint64_t check);
2733 static void l2arc_blk_fetch_done(zio_t *zio);
2734 static inline uint64_t
2735 l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev);
2736
2737 /*
2738 * Return a loaned arc buffer to the arc.
2739 */
2740 void
arc_return_buf(arc_buf_t * buf,void * tag)2741 arc_return_buf(arc_buf_t *buf, void *tag)
2742 {
2743 arc_buf_hdr_t *hdr = buf->b_hdr;
2744
2745 ASSERT3P(buf->b_data, !=, NULL);
2746 ASSERT(HDR_HAS_L1HDR(hdr));
2747 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, tag);
2748 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2749
2750 arc_loaned_bytes_update(-arc_buf_size(buf));
2751 }
2752
2753 /* Detach an arc_buf from a dbuf (tag) */
2754 void
arc_loan_inuse_buf(arc_buf_t * buf,void * tag)2755 arc_loan_inuse_buf(arc_buf_t *buf, void *tag)
2756 {
2757 arc_buf_hdr_t *hdr = buf->b_hdr;
2758
2759 ASSERT3P(buf->b_data, !=, NULL);
2760 ASSERT(HDR_HAS_L1HDR(hdr));
2761 (void) zfs_refcount_add(&hdr->b_l1hdr.b_refcnt, arc_onloan_tag);
2762 (void) zfs_refcount_remove(&hdr->b_l1hdr.b_refcnt, tag);
2763
2764 arc_loaned_bytes_update(arc_buf_size(buf));
2765 }
2766
2767 static void
l2arc_free_abd_on_write(abd_t * abd,size_t size,arc_buf_contents_t type)2768 l2arc_free_abd_on_write(abd_t *abd, size_t size, arc_buf_contents_t type)
2769 {
2770 l2arc_data_free_t *df = kmem_alloc(sizeof (*df), KM_SLEEP);
2771
2772 df->l2df_abd = abd;
2773 df->l2df_size = size;
2774 df->l2df_type = type;
2775 mutex_enter(&l2arc_free_on_write_mtx);
2776 list_insert_head(l2arc_free_on_write, df);
2777 mutex_exit(&l2arc_free_on_write_mtx);
2778 }
2779
2780 static void
arc_hdr_free_on_write(arc_buf_hdr_t * hdr,boolean_t free_rdata)2781 arc_hdr_free_on_write(arc_buf_hdr_t *hdr, boolean_t free_rdata)
2782 {
2783 arc_state_t *state = hdr->b_l1hdr.b_state;
2784 arc_buf_contents_t type = arc_buf_type(hdr);
2785 uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
2786
2787 /* protected by hash lock, if in the hash table */
2788 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
2789 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
2790 ASSERT(state != arc_anon && state != arc_l2c_only);
2791
2792 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
2793 size, hdr);
2794 }
2795 (void) zfs_refcount_remove_many(&state->arcs_size, size, hdr);
2796 if (type == ARC_BUFC_METADATA) {
2797 arc_space_return(size, ARC_SPACE_META);
2798 } else {
2799 ASSERT(type == ARC_BUFC_DATA);
2800 arc_space_return(size, ARC_SPACE_DATA);
2801 }
2802
2803 if (free_rdata) {
2804 l2arc_free_abd_on_write(hdr->b_crypt_hdr.b_rabd, size, type);
2805 } else {
2806 l2arc_free_abd_on_write(hdr->b_l1hdr.b_pabd, size, type);
2807 }
2808 }
2809
2810 /*
2811 * Share the arc_buf_t's data with the hdr. Whenever we are sharing the
2812 * data buffer, we transfer the refcount ownership to the hdr and update
2813 * the appropriate kstats.
2814 */
2815 static void
arc_share_buf(arc_buf_hdr_t * hdr,arc_buf_t * buf)2816 arc_share_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2817 {
2818 /* LINTED */
2819 arc_state_t *state = hdr->b_l1hdr.b_state;
2820
2821 ASSERT(arc_can_share(hdr, buf));
2822 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
2823 ASSERT(!ARC_BUF_ENCRYPTED(buf));
2824 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2825
2826 /*
2827 * Start sharing the data buffer. We transfer the
2828 * refcount ownership to the hdr since it always owns
2829 * the refcount whenever an arc_buf_t is shared.
2830 */
2831 zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size,
2832 arc_hdr_size(hdr), buf, hdr);
2833 hdr->b_l1hdr.b_pabd = abd_get_from_buf(buf->b_data, arc_buf_size(buf));
2834 abd_take_ownership_of_buf(hdr->b_l1hdr.b_pabd,
2835 HDR_ISTYPE_METADATA(hdr));
2836 arc_hdr_set_flags(hdr, ARC_FLAG_SHARED_DATA);
2837 buf->b_flags |= ARC_BUF_FLAG_SHARED;
2838
2839 /*
2840 * Since we've transferred ownership to the hdr we need
2841 * to increment its compressed and uncompressed kstats and
2842 * decrement the overhead size.
2843 */
2844 ARCSTAT_INCR(arcstat_compressed_size, arc_hdr_size(hdr));
2845 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
2846 ARCSTAT_INCR(arcstat_overhead_size, -arc_buf_size(buf));
2847 }
2848
2849 static void
arc_unshare_buf(arc_buf_hdr_t * hdr,arc_buf_t * buf)2850 arc_unshare_buf(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2851 {
2852 /* LINTED */
2853 arc_state_t *state = hdr->b_l1hdr.b_state;
2854
2855 ASSERT(arc_buf_is_shared(buf));
2856 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2857 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2858
2859 /*
2860 * We are no longer sharing this buffer so we need
2861 * to transfer its ownership to the rightful owner.
2862 */
2863 zfs_refcount_transfer_ownership_many(&hdr->b_l1hdr.b_state->arcs_size,
2864 arc_hdr_size(hdr), hdr, buf);
2865 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2866 abd_release_ownership_of_buf(hdr->b_l1hdr.b_pabd);
2867 abd_put(hdr->b_l1hdr.b_pabd);
2868 hdr->b_l1hdr.b_pabd = NULL;
2869 buf->b_flags &= ~ARC_BUF_FLAG_SHARED;
2870
2871 /*
2872 * Since the buffer is no longer shared between
2873 * the arc buf and the hdr, count it as overhead.
2874 */
2875 ARCSTAT_INCR(arcstat_compressed_size, -arc_hdr_size(hdr));
2876 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
2877 ARCSTAT_INCR(arcstat_overhead_size, arc_buf_size(buf));
2878 }
2879
2880 /*
2881 * Remove an arc_buf_t from the hdr's buf list and return the last
2882 * arc_buf_t on the list. If no buffers remain on the list then return
2883 * NULL.
2884 */
2885 static arc_buf_t *
arc_buf_remove(arc_buf_hdr_t * hdr,arc_buf_t * buf)2886 arc_buf_remove(arc_buf_hdr_t *hdr, arc_buf_t *buf)
2887 {
2888 arc_buf_t **bufp = &hdr->b_l1hdr.b_buf;
2889 arc_buf_t *lastbuf = NULL;
2890
2891 ASSERT(HDR_HAS_L1HDR(hdr));
2892 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2893
2894 /*
2895 * Remove the buf from the hdr list and locate the last
2896 * remaining buffer on the list.
2897 */
2898 while (*bufp != NULL) {
2899 if (*bufp == buf)
2900 *bufp = buf->b_next;
2901
2902 /*
2903 * If we've removed a buffer in the middle of
2904 * the list then update the lastbuf and update
2905 * bufp.
2906 */
2907 if (*bufp != NULL) {
2908 lastbuf = *bufp;
2909 bufp = &(*bufp)->b_next;
2910 }
2911 }
2912 buf->b_next = NULL;
2913 ASSERT3P(lastbuf, !=, buf);
2914 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, lastbuf != NULL);
2915 IMPLY(hdr->b_l1hdr.b_bufcnt > 0, hdr->b_l1hdr.b_buf != NULL);
2916 IMPLY(lastbuf != NULL, ARC_BUF_LAST(lastbuf));
2917
2918 return (lastbuf);
2919 }
2920
2921 /*
2922 * Free up buf->b_data and pull the arc_buf_t off of the the arc_buf_hdr_t's
2923 * list and free it.
2924 */
2925 static void
arc_buf_destroy_impl(arc_buf_t * buf)2926 arc_buf_destroy_impl(arc_buf_t *buf)
2927 {
2928 arc_buf_hdr_t *hdr = buf->b_hdr;
2929
2930 /*
2931 * Free up the data associated with the buf but only if we're not
2932 * sharing this with the hdr. If we are sharing it with the hdr, the
2933 * hdr is responsible for doing the free.
2934 */
2935 if (buf->b_data != NULL) {
2936 /*
2937 * We're about to change the hdr's b_flags. We must either
2938 * hold the hash_lock or be undiscoverable.
2939 */
2940 ASSERT(HDR_EMPTY_OR_LOCKED(hdr));
2941
2942 arc_cksum_verify(buf);
2943 arc_buf_unwatch(buf);
2944
2945 if (arc_buf_is_shared(buf)) {
2946 arc_hdr_clear_flags(hdr, ARC_FLAG_SHARED_DATA);
2947 } else {
2948 uint64_t size = arc_buf_size(buf);
2949 arc_free_data_buf(hdr, buf->b_data, size, buf);
2950 ARCSTAT_INCR(arcstat_overhead_size, -size);
2951 }
2952 buf->b_data = NULL;
2953
2954 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
2955 hdr->b_l1hdr.b_bufcnt -= 1;
2956
2957 if (ARC_BUF_ENCRYPTED(buf)) {
2958 hdr->b_crypt_hdr.b_ebufcnt -= 1;
2959
2960 /*
2961 * If we have no more encrypted buffers and we've
2962 * already gotten a copy of the decrypted data we can
2963 * free b_rabd to save some space.
2964 */
2965 if (hdr->b_crypt_hdr.b_ebufcnt == 0 &&
2966 HDR_HAS_RABD(hdr) && hdr->b_l1hdr.b_pabd != NULL &&
2967 !HDR_IO_IN_PROGRESS(hdr)) {
2968 arc_hdr_free_pabd(hdr, B_TRUE);
2969 }
2970 }
2971 }
2972
2973 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
2974
2975 if (ARC_BUF_SHARED(buf) && !ARC_BUF_COMPRESSED(buf)) {
2976 /*
2977 * If the current arc_buf_t is sharing its data buffer with the
2978 * hdr, then reassign the hdr's b_pabd to share it with the new
2979 * buffer at the end of the list. The shared buffer is always
2980 * the last one on the hdr's buffer list.
2981 *
2982 * There is an equivalent case for compressed bufs, but since
2983 * they aren't guaranteed to be the last buf in the list and
2984 * that is an exceedingly rare case, we just allow that space be
2985 * wasted temporarily. We must also be careful not to share
2986 * encrypted buffers, since they cannot be shared.
2987 */
2988 if (lastbuf != NULL && !ARC_BUF_ENCRYPTED(lastbuf)) {
2989 /* Only one buf can be shared at once */
2990 VERIFY(!arc_buf_is_shared(lastbuf));
2991 /* hdr is uncompressed so can't have compressed buf */
2992 VERIFY(!ARC_BUF_COMPRESSED(lastbuf));
2993
2994 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
2995 arc_hdr_free_pabd(hdr, B_FALSE);
2996
2997 /*
2998 * We must setup a new shared block between the
2999 * last buffer and the hdr. The data would have
3000 * been allocated by the arc buf so we need to transfer
3001 * ownership to the hdr since it's now being shared.
3002 */
3003 arc_share_buf(hdr, lastbuf);
3004 }
3005 } else if (HDR_SHARED_DATA(hdr)) {
3006 /*
3007 * Uncompressed shared buffers are always at the end
3008 * of the list. Compressed buffers don't have the
3009 * same requirements. This makes it hard to
3010 * simply assert that the lastbuf is shared so
3011 * we rely on the hdr's compression flags to determine
3012 * if we have a compressed, shared buffer.
3013 */
3014 ASSERT3P(lastbuf, !=, NULL);
3015 ASSERT(arc_buf_is_shared(lastbuf) ||
3016 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
3017 }
3018
3019 /*
3020 * Free the checksum if we're removing the last uncompressed buf from
3021 * this hdr.
3022 */
3023 if (!arc_hdr_has_uncompressed_buf(hdr)) {
3024 arc_cksum_free(hdr);
3025 }
3026
3027 /* clean up the buf */
3028 buf->b_hdr = NULL;
3029 kmem_cache_free(buf_cache, buf);
3030 }
3031
3032 static void
arc_hdr_alloc_pabd(arc_buf_hdr_t * hdr,int alloc_flags)3033 arc_hdr_alloc_pabd(arc_buf_hdr_t *hdr, int alloc_flags)
3034 {
3035 uint64_t size;
3036 boolean_t alloc_rdata = ((alloc_flags & ARC_HDR_ALLOC_RDATA) != 0);
3037 boolean_t do_adapt = ((alloc_flags & ARC_HDR_DO_ADAPT) != 0);
3038
3039 ASSERT3U(HDR_GET_LSIZE(hdr), >, 0);
3040 ASSERT(HDR_HAS_L1HDR(hdr));
3041 ASSERT(!HDR_SHARED_DATA(hdr) || alloc_rdata);
3042 IMPLY(alloc_rdata, HDR_PROTECTED(hdr));
3043
3044 if (alloc_rdata) {
3045 size = HDR_GET_PSIZE(hdr);
3046 ASSERT3P(hdr->b_crypt_hdr.b_rabd, ==, NULL);
3047 hdr->b_crypt_hdr.b_rabd = arc_get_data_abd(hdr, size, hdr,
3048 do_adapt);
3049 ASSERT3P(hdr->b_crypt_hdr.b_rabd, !=, NULL);
3050 } else {
3051 size = arc_hdr_size(hdr);
3052 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3053 hdr->b_l1hdr.b_pabd = arc_get_data_abd(hdr, size, hdr,
3054 do_adapt);
3055 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
3056 }
3057
3058 ARCSTAT_INCR(arcstat_compressed_size, size);
3059 ARCSTAT_INCR(arcstat_uncompressed_size, HDR_GET_LSIZE(hdr));
3060 }
3061
3062 static void
arc_hdr_free_pabd(arc_buf_hdr_t * hdr,boolean_t free_rdata)3063 arc_hdr_free_pabd(arc_buf_hdr_t *hdr, boolean_t free_rdata)
3064 {
3065 uint64_t size = (free_rdata) ? HDR_GET_PSIZE(hdr) : arc_hdr_size(hdr);
3066
3067 ASSERT(HDR_HAS_L1HDR(hdr));
3068 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
3069 IMPLY(free_rdata, HDR_HAS_RABD(hdr));
3070
3071
3072 /*
3073 * If the hdr is currently being written to the l2arc then
3074 * we defer freeing the data by adding it to the l2arc_free_on_write
3075 * list. The l2arc will free the data once it's finished
3076 * writing it to the l2arc device.
3077 */
3078 if (HDR_L2_WRITING(hdr)) {
3079 arc_hdr_free_on_write(hdr, free_rdata);
3080 ARCSTAT_BUMP(arcstat_l2_free_on_write);
3081 } else if (free_rdata) {
3082 arc_free_data_abd(hdr, hdr->b_crypt_hdr.b_rabd, size, hdr);
3083 } else {
3084 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
3085 size, hdr);
3086 }
3087
3088 if (free_rdata) {
3089 hdr->b_crypt_hdr.b_rabd = NULL;
3090 } else {
3091 hdr->b_l1hdr.b_pabd = NULL;
3092 }
3093
3094 if (hdr->b_l1hdr.b_pabd == NULL && !HDR_HAS_RABD(hdr))
3095 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
3096
3097 ARCSTAT_INCR(arcstat_compressed_size, -size);
3098 ARCSTAT_INCR(arcstat_uncompressed_size, -HDR_GET_LSIZE(hdr));
3099 }
3100
3101 static arc_buf_hdr_t *
arc_hdr_alloc(uint64_t spa,int32_t psize,int32_t lsize,boolean_t protected,enum zio_compress compression_type,arc_buf_contents_t type,boolean_t alloc_rdata)3102 arc_hdr_alloc(uint64_t spa, int32_t psize, int32_t lsize,
3103 boolean_t protected, enum zio_compress compression_type,
3104 arc_buf_contents_t type, boolean_t alloc_rdata)
3105 {
3106 arc_buf_hdr_t *hdr;
3107 int flags = ARC_HDR_DO_ADAPT;
3108
3109 VERIFY(type == ARC_BUFC_DATA || type == ARC_BUFC_METADATA);
3110 if (protected) {
3111 hdr = kmem_cache_alloc(hdr_full_crypt_cache, KM_PUSHPAGE);
3112 } else {
3113 hdr = kmem_cache_alloc(hdr_full_cache, KM_PUSHPAGE);
3114 }
3115 flags |= alloc_rdata ? ARC_HDR_ALLOC_RDATA : 0;
3116 ASSERT(HDR_EMPTY(hdr));
3117 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3118 ASSERT3P(hdr->b_l1hdr.b_thawed, ==, NULL);
3119 HDR_SET_PSIZE(hdr, psize);
3120 HDR_SET_LSIZE(hdr, lsize);
3121 hdr->b_spa = spa;
3122 hdr->b_type = type;
3123 hdr->b_flags = 0;
3124 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L1HDR);
3125 arc_hdr_set_compress(hdr, compression_type);
3126 if (protected)
3127 arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
3128
3129 hdr->b_l1hdr.b_state = arc_anon;
3130 hdr->b_l1hdr.b_arc_access = 0;
3131 hdr->b_l1hdr.b_bufcnt = 0;
3132 hdr->b_l1hdr.b_buf = NULL;
3133
3134 /*
3135 * Allocate the hdr's buffer. This will contain either
3136 * the compressed or uncompressed data depending on the block
3137 * it references and compressed arc enablement.
3138 */
3139 arc_hdr_alloc_pabd(hdr, flags);
3140 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3141
3142 return (hdr);
3143 }
3144
3145 /*
3146 * Transition between the two allocation states for the arc_buf_hdr struct.
3147 * The arc_buf_hdr struct can be allocated with (hdr_full_cache) or without
3148 * (hdr_l2only_cache) the fields necessary for the L1 cache - the smaller
3149 * version is used when a cache buffer is only in the L2ARC in order to reduce
3150 * memory usage.
3151 */
3152 static arc_buf_hdr_t *
arc_hdr_realloc(arc_buf_hdr_t * hdr,kmem_cache_t * old,kmem_cache_t * new)3153 arc_hdr_realloc(arc_buf_hdr_t *hdr, kmem_cache_t *old, kmem_cache_t *new)
3154 {
3155 ASSERT(HDR_HAS_L2HDR(hdr));
3156
3157 arc_buf_hdr_t *nhdr;
3158 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3159
3160 ASSERT((old == hdr_full_cache && new == hdr_l2only_cache) ||
3161 (old == hdr_l2only_cache && new == hdr_full_cache));
3162
3163 /*
3164 * if the caller wanted a new full header and the header is to be
3165 * encrypted we will actually allocate the header from the full crypt
3166 * cache instead. The same applies to freeing from the old cache.
3167 */
3168 if (HDR_PROTECTED(hdr) && new == hdr_full_cache)
3169 new = hdr_full_crypt_cache;
3170 if (HDR_PROTECTED(hdr) && old == hdr_full_cache)
3171 old = hdr_full_crypt_cache;
3172
3173 nhdr = kmem_cache_alloc(new, KM_PUSHPAGE);
3174
3175 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
3176 buf_hash_remove(hdr);
3177
3178 bcopy(hdr, nhdr, HDR_L2ONLY_SIZE);
3179
3180 if (new == hdr_full_cache || new == hdr_full_crypt_cache) {
3181 arc_hdr_set_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3182 /*
3183 * arc_access and arc_change_state need to be aware that a
3184 * header has just come out of L2ARC, so we set its state to
3185 * l2c_only even though it's about to change.
3186 */
3187 nhdr->b_l1hdr.b_state = arc_l2c_only;
3188
3189 /* Verify previous threads set to NULL before freeing */
3190 ASSERT3P(nhdr->b_l1hdr.b_pabd, ==, NULL);
3191 ASSERT(!HDR_HAS_RABD(hdr));
3192 } else {
3193 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3194 ASSERT0(hdr->b_l1hdr.b_bufcnt);
3195 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3196
3197 /*
3198 * If we've reached here, We must have been called from
3199 * arc_evict_hdr(), as such we should have already been
3200 * removed from any ghost list we were previously on
3201 * (which protects us from racing with arc_evict_state),
3202 * thus no locking is needed during this check.
3203 */
3204 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3205
3206 /*
3207 * A buffer must not be moved into the arc_l2c_only
3208 * state if it's not finished being written out to the
3209 * l2arc device. Otherwise, the b_l1hdr.b_pabd field
3210 * might try to be accessed, even though it was removed.
3211 */
3212 VERIFY(!HDR_L2_WRITING(hdr));
3213 VERIFY3P(hdr->b_l1hdr.b_pabd, ==, NULL);
3214 ASSERT(!HDR_HAS_RABD(hdr));
3215
3216 #ifdef ZFS_DEBUG
3217 if (hdr->b_l1hdr.b_thawed != NULL) {
3218 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3219 hdr->b_l1hdr.b_thawed = NULL;
3220 }
3221 #endif
3222
3223 arc_hdr_clear_flags(nhdr, ARC_FLAG_HAS_L1HDR);
3224 }
3225 /*
3226 * The header has been reallocated so we need to re-insert it into any
3227 * lists it was on.
3228 */
3229 (void) buf_hash_insert(nhdr, NULL);
3230
3231 ASSERT(list_link_active(&hdr->b_l2hdr.b_l2node));
3232
3233 mutex_enter(&dev->l2ad_mtx);
3234
3235 /*
3236 * We must place the realloc'ed header back into the list at
3237 * the same spot. Otherwise, if it's placed earlier in the list,
3238 * l2arc_write_buffers() could find it during the function's
3239 * write phase, and try to write it out to the l2arc.
3240 */
3241 list_insert_after(&dev->l2ad_buflist, hdr, nhdr);
3242 list_remove(&dev->l2ad_buflist, hdr);
3243
3244 mutex_exit(&dev->l2ad_mtx);
3245
3246 /*
3247 * Since we're using the pointer address as the tag when
3248 * incrementing and decrementing the l2ad_alloc refcount, we
3249 * must remove the old pointer (that we're about to destroy) and
3250 * add the new pointer to the refcount. Otherwise we'd remove
3251 * the wrong pointer address when calling arc_hdr_destroy() later.
3252 */
3253
3254 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr),
3255 hdr);
3256 (void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(nhdr),
3257 nhdr);
3258
3259 buf_discard_identity(hdr);
3260 kmem_cache_free(old, hdr);
3261
3262 return (nhdr);
3263 }
3264
3265 /*
3266 * This function allows an L1 header to be reallocated as a crypt
3267 * header and vice versa. If we are going to a crypt header, the
3268 * new fields will be zeroed out.
3269 */
3270 static arc_buf_hdr_t *
arc_hdr_realloc_crypt(arc_buf_hdr_t * hdr,boolean_t need_crypt)3271 arc_hdr_realloc_crypt(arc_buf_hdr_t *hdr, boolean_t need_crypt)
3272 {
3273 arc_buf_hdr_t *nhdr;
3274 arc_buf_t *buf;
3275 kmem_cache_t *ncache, *ocache;
3276
3277 ASSERT(HDR_HAS_L1HDR(hdr));
3278 ASSERT3U(!!HDR_PROTECTED(hdr), !=, need_crypt);
3279 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3280 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3281 ASSERT(!list_link_active(&hdr->b_l2hdr.b_l2node));
3282 ASSERT3P(hdr->b_hash_next, ==, NULL);
3283
3284 if (need_crypt) {
3285 ncache = hdr_full_crypt_cache;
3286 ocache = hdr_full_cache;
3287 } else {
3288 ncache = hdr_full_cache;
3289 ocache = hdr_full_crypt_cache;
3290 }
3291
3292 nhdr = kmem_cache_alloc(ncache, KM_PUSHPAGE);
3293
3294 /*
3295 * Copy all members that aren't locks or condvars to the new header.
3296 * No lists are pointing to us (as we asserted above), so we don't
3297 * need to worry about the list nodes.
3298 */
3299 nhdr->b_dva = hdr->b_dva;
3300 nhdr->b_birth = hdr->b_birth;
3301 nhdr->b_type = hdr->b_type;
3302 nhdr->b_flags = hdr->b_flags;
3303 nhdr->b_psize = hdr->b_psize;
3304 nhdr->b_lsize = hdr->b_lsize;
3305 nhdr->b_spa = hdr->b_spa;
3306 nhdr->b_l2hdr.b_dev = hdr->b_l2hdr.b_dev;
3307 nhdr->b_l2hdr.b_daddr = hdr->b_l2hdr.b_daddr;
3308 nhdr->b_l1hdr.b_freeze_cksum = hdr->b_l1hdr.b_freeze_cksum;
3309 nhdr->b_l1hdr.b_bufcnt = hdr->b_l1hdr.b_bufcnt;
3310 nhdr->b_l1hdr.b_byteswap = hdr->b_l1hdr.b_byteswap;
3311 nhdr->b_l1hdr.b_state = hdr->b_l1hdr.b_state;
3312 nhdr->b_l1hdr.b_arc_access = hdr->b_l1hdr.b_arc_access;
3313 nhdr->b_l1hdr.b_acb = hdr->b_l1hdr.b_acb;
3314 nhdr->b_l1hdr.b_pabd = hdr->b_l1hdr.b_pabd;
3315 #ifdef ZFS_DEBUG
3316 if (hdr->b_l1hdr.b_thawed != NULL) {
3317 nhdr->b_l1hdr.b_thawed = hdr->b_l1hdr.b_thawed;
3318 hdr->b_l1hdr.b_thawed = NULL;
3319 }
3320 #endif
3321
3322 /*
3323 * This refcount_add() exists only to ensure that the individual
3324 * arc buffers always point to a header that is referenced, avoiding
3325 * a small race condition that could trigger ASSERTs.
3326 */
3327 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, FTAG);
3328 nhdr->b_l1hdr.b_buf = hdr->b_l1hdr.b_buf;
3329 for (buf = nhdr->b_l1hdr.b_buf; buf != NULL; buf = buf->b_next) {
3330 mutex_enter(&buf->b_evict_lock);
3331 buf->b_hdr = nhdr;
3332 mutex_exit(&buf->b_evict_lock);
3333 }
3334 zfs_refcount_transfer(&nhdr->b_l1hdr.b_refcnt, &hdr->b_l1hdr.b_refcnt);
3335 (void) zfs_refcount_remove(&nhdr->b_l1hdr.b_refcnt, FTAG);
3336 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
3337
3338 if (need_crypt) {
3339 arc_hdr_set_flags(nhdr, ARC_FLAG_PROTECTED);
3340 } else {
3341 arc_hdr_clear_flags(nhdr, ARC_FLAG_PROTECTED);
3342 }
3343
3344 /* unset all members of the original hdr */
3345 bzero(&hdr->b_dva, sizeof (dva_t));
3346 hdr->b_birth = 0;
3347 hdr->b_type = ARC_BUFC_INVALID;
3348 hdr->b_flags = 0;
3349 hdr->b_psize = 0;
3350 hdr->b_lsize = 0;
3351 hdr->b_spa = 0;
3352 hdr->b_l2hdr.b_dev = NULL;
3353 hdr->b_l2hdr.b_daddr = 0;
3354 hdr->b_l1hdr.b_freeze_cksum = NULL;
3355 hdr->b_l1hdr.b_buf = NULL;
3356 hdr->b_l1hdr.b_bufcnt = 0;
3357 hdr->b_l1hdr.b_byteswap = 0;
3358 hdr->b_l1hdr.b_state = NULL;
3359 hdr->b_l1hdr.b_arc_access = 0;
3360 hdr->b_l1hdr.b_acb = NULL;
3361 hdr->b_l1hdr.b_pabd = NULL;
3362
3363 if (ocache == hdr_full_crypt_cache) {
3364 ASSERT(!HDR_HAS_RABD(hdr));
3365 hdr->b_crypt_hdr.b_ot = DMU_OT_NONE;
3366 hdr->b_crypt_hdr.b_ebufcnt = 0;
3367 hdr->b_crypt_hdr.b_dsobj = 0;
3368 bzero(hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3369 bzero(hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3370 bzero(hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3371 }
3372
3373 buf_discard_identity(hdr);
3374 kmem_cache_free(ocache, hdr);
3375
3376 return (nhdr);
3377 }
3378
3379 /*
3380 * This function is used by the send / receive code to convert a newly
3381 * allocated arc_buf_t to one that is suitable for a raw encrypted write. It
3382 * is also used to allow the root objset block to be uupdated without altering
3383 * its embedded MACs. Both block types will always be uncompressed so we do not
3384 * have to worry about compression type or psize.
3385 */
3386 void
arc_convert_to_raw(arc_buf_t * buf,uint64_t dsobj,boolean_t byteorder,dmu_object_type_t ot,const uint8_t * salt,const uint8_t * iv,const uint8_t * mac)3387 arc_convert_to_raw(arc_buf_t *buf, uint64_t dsobj, boolean_t byteorder,
3388 dmu_object_type_t ot, const uint8_t *salt, const uint8_t *iv,
3389 const uint8_t *mac)
3390 {
3391 arc_buf_hdr_t *hdr = buf->b_hdr;
3392
3393 ASSERT(ot == DMU_OT_DNODE || ot == DMU_OT_OBJSET);
3394 ASSERT(HDR_HAS_L1HDR(hdr));
3395 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3396
3397 buf->b_flags |= (ARC_BUF_FLAG_COMPRESSED | ARC_BUF_FLAG_ENCRYPTED);
3398 if (!HDR_PROTECTED(hdr))
3399 hdr = arc_hdr_realloc_crypt(hdr, B_TRUE);
3400 hdr->b_crypt_hdr.b_dsobj = dsobj;
3401 hdr->b_crypt_hdr.b_ot = ot;
3402 hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
3403 DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
3404 if (!arc_hdr_has_uncompressed_buf(hdr))
3405 arc_cksum_free(hdr);
3406
3407 if (salt != NULL)
3408 bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3409 if (iv != NULL)
3410 bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3411 if (mac != NULL)
3412 bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3413 }
3414
3415 /*
3416 * Allocate a new arc_buf_hdr_t and arc_buf_t and return the buf to the caller.
3417 * The buf is returned thawed since we expect the consumer to modify it.
3418 */
3419 arc_buf_t *
arc_alloc_buf(spa_t * spa,void * tag,arc_buf_contents_t type,int32_t size)3420 arc_alloc_buf(spa_t *spa, void *tag, arc_buf_contents_t type, int32_t size)
3421 {
3422 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), size, size,
3423 B_FALSE, ZIO_COMPRESS_OFF, type, B_FALSE);
3424
3425 arc_buf_t *buf = NULL;
3426 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE, B_FALSE,
3427 B_FALSE, B_FALSE, &buf));
3428 arc_buf_thaw(buf);
3429
3430 return (buf);
3431 }
3432
3433 /*
3434 * Allocates an ARC buf header that's in an evicted & L2-cached state.
3435 * This is used during l2arc reconstruction to make empty ARC buffers
3436 * which circumvent the regular disk->arc->l2arc path and instead come
3437 * into being in the reverse order, i.e. l2arc->arc.
3438 */
3439 arc_buf_hdr_t *
arc_buf_alloc_l2only(size_t size,arc_buf_contents_t type,l2arc_dev_t * dev,dva_t dva,uint64_t daddr,int32_t psize,uint64_t birth,enum zio_compress compress,boolean_t protected,boolean_t prefetch,arc_state_type_t arcs_state)3440 arc_buf_alloc_l2only(size_t size, arc_buf_contents_t type, l2arc_dev_t *dev,
3441 dva_t dva, uint64_t daddr, int32_t psize, uint64_t birth,
3442 enum zio_compress compress, boolean_t protected,
3443 boolean_t prefetch, arc_state_type_t arcs_state)
3444 {
3445 arc_buf_hdr_t *hdr;
3446
3447 ASSERT(size != 0);
3448 hdr = kmem_cache_alloc(hdr_l2only_cache, KM_SLEEP);
3449 hdr->b_birth = birth;
3450 hdr->b_type = type;
3451 hdr->b_flags = 0;
3452 arc_hdr_set_flags(hdr, arc_bufc_to_flags(type) | ARC_FLAG_HAS_L2HDR);
3453 HDR_SET_LSIZE(hdr, size);
3454 HDR_SET_PSIZE(hdr, psize);
3455 arc_hdr_set_compress(hdr, compress);
3456 if (protected)
3457 arc_hdr_set_flags(hdr, ARC_FLAG_PROTECTED);
3458 if (prefetch)
3459 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
3460 hdr->b_spa = spa_load_guid(dev->l2ad_vdev->vdev_spa);
3461
3462 hdr->b_dva = dva;
3463
3464 hdr->b_l2hdr.b_dev = dev;
3465 hdr->b_l2hdr.b_daddr = daddr;
3466 hdr->b_l2hdr.b_arcs_state = arcs_state;
3467
3468 return (hdr);
3469 }
3470
3471 /*
3472 * Allocate a compressed buf in the same manner as arc_alloc_buf. Don't use this
3473 * for bufs containing metadata.
3474 */
3475 arc_buf_t *
arc_alloc_compressed_buf(spa_t * spa,void * tag,uint64_t psize,uint64_t lsize,enum zio_compress compression_type)3476 arc_alloc_compressed_buf(spa_t *spa, void *tag, uint64_t psize, uint64_t lsize,
3477 enum zio_compress compression_type)
3478 {
3479 ASSERT3U(lsize, >, 0);
3480 ASSERT3U(lsize, >=, psize);
3481 ASSERT3U(compression_type, >, ZIO_COMPRESS_OFF);
3482 ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
3483
3484 arc_buf_hdr_t *hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
3485 B_FALSE, compression_type, ARC_BUFC_DATA, B_FALSE);
3486
3487 arc_buf_t *buf = NULL;
3488 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_FALSE,
3489 B_TRUE, B_FALSE, B_FALSE, &buf));
3490 arc_buf_thaw(buf);
3491 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3492
3493 if (!arc_buf_is_shared(buf)) {
3494 /*
3495 * To ensure that the hdr has the correct data in it if we call
3496 * arc_untransform() on this buf before it's been written to
3497 * disk, it's easiest if we just set up sharing between the
3498 * buf and the hdr.
3499 */
3500 ASSERT(!abd_is_linear(hdr->b_l1hdr.b_pabd));
3501 arc_hdr_free_pabd(hdr, B_FALSE);
3502 arc_share_buf(hdr, buf);
3503 }
3504
3505 return (buf);
3506 }
3507
3508 arc_buf_t *
arc_alloc_raw_buf(spa_t * spa,void * tag,uint64_t dsobj,boolean_t byteorder,const uint8_t * salt,const uint8_t * iv,const uint8_t * mac,dmu_object_type_t ot,uint64_t psize,uint64_t lsize,enum zio_compress compression_type)3509 arc_alloc_raw_buf(spa_t *spa, void *tag, uint64_t dsobj, boolean_t byteorder,
3510 const uint8_t *salt, const uint8_t *iv, const uint8_t *mac,
3511 dmu_object_type_t ot, uint64_t psize, uint64_t lsize,
3512 enum zio_compress compression_type)
3513 {
3514 arc_buf_hdr_t *hdr;
3515 arc_buf_t *buf;
3516 arc_buf_contents_t type = DMU_OT_IS_METADATA(ot) ?
3517 ARC_BUFC_METADATA : ARC_BUFC_DATA;
3518
3519 ASSERT3U(lsize, >, 0);
3520 ASSERT3U(lsize, >=, psize);
3521 ASSERT3U(compression_type, >=, ZIO_COMPRESS_OFF);
3522 ASSERT3U(compression_type, <, ZIO_COMPRESS_FUNCTIONS);
3523
3524 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize, B_TRUE,
3525 compression_type, type, B_TRUE);
3526
3527 hdr->b_crypt_hdr.b_dsobj = dsobj;
3528 hdr->b_crypt_hdr.b_ot = ot;
3529 hdr->b_l1hdr.b_byteswap = (byteorder == ZFS_HOST_BYTEORDER) ?
3530 DMU_BSWAP_NUMFUNCS : DMU_OT_BYTESWAP(ot);
3531 bcopy(salt, hdr->b_crypt_hdr.b_salt, ZIO_DATA_SALT_LEN);
3532 bcopy(iv, hdr->b_crypt_hdr.b_iv, ZIO_DATA_IV_LEN);
3533 bcopy(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN);
3534
3535 /*
3536 * This buffer will be considered encrypted even if the ot is not an
3537 * encrypted type. It will become authenticated instead in
3538 * arc_write_ready().
3539 */
3540 buf = NULL;
3541 VERIFY0(arc_buf_alloc_impl(hdr, spa, NULL, tag, B_TRUE, B_TRUE,
3542 B_FALSE, B_FALSE, &buf));
3543 arc_buf_thaw(buf);
3544 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
3545
3546 return (buf);
3547 }
3548
3549 static void
l2arc_hdr_arcstats_update(arc_buf_hdr_t * hdr,boolean_t incr,boolean_t state_only)3550 l2arc_hdr_arcstats_update(arc_buf_hdr_t *hdr, boolean_t incr,
3551 boolean_t state_only)
3552 {
3553 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3554 l2arc_dev_t *dev = l2hdr->b_dev;
3555 uint64_t lsize = HDR_GET_LSIZE(hdr);
3556 uint64_t psize = HDR_GET_PSIZE(hdr);
3557 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
3558 arc_buf_contents_t type = hdr->b_type;
3559 int64_t lsize_s;
3560 int64_t psize_s;
3561 int64_t asize_s;
3562
3563 if (incr) {
3564 lsize_s = lsize;
3565 psize_s = psize;
3566 asize_s = asize;
3567 } else {
3568 lsize_s = -lsize;
3569 psize_s = -psize;
3570 asize_s = -asize;
3571 }
3572
3573 /* If the buffer is a prefetch, count it as such. */
3574 if (HDR_PREFETCH(hdr)) {
3575 ARCSTAT_INCR(arcstat_l2_prefetch_asize, asize_s);
3576 } else {
3577 /*
3578 * We use the value stored in the L2 header upon initial
3579 * caching in L2ARC. This value will be updated in case
3580 * an MRU/MRU_ghost buffer transitions to MFU but the L2ARC
3581 * metadata (log entry) cannot currently be updated. Having
3582 * the ARC state in the L2 header solves the problem of a
3583 * possibly absent L1 header (apparent in buffers restored
3584 * from persistent L2ARC).
3585 */
3586 switch (hdr->b_l2hdr.b_arcs_state) {
3587 case ARC_STATE_MRU_GHOST:
3588 case ARC_STATE_MRU:
3589 ARCSTAT_INCR(arcstat_l2_mru_asize, asize_s);
3590 break;
3591 case ARC_STATE_MFU_GHOST:
3592 case ARC_STATE_MFU:
3593 ARCSTAT_INCR(arcstat_l2_mfu_asize, asize_s);
3594 break;
3595 default:
3596 break;
3597 }
3598 }
3599
3600 if (state_only)
3601 return;
3602
3603 ARCSTAT_INCR(arcstat_l2_psize, psize_s);
3604 ARCSTAT_INCR(arcstat_l2_lsize, lsize_s);
3605
3606 switch (type) {
3607 case ARC_BUFC_DATA:
3608 ARCSTAT_INCR(arcstat_l2_bufc_data_asize, asize_s);
3609 break;
3610 case ARC_BUFC_METADATA:
3611 ARCSTAT_INCR(arcstat_l2_bufc_metadata_asize, asize_s);
3612 break;
3613 default:
3614 break;
3615 }
3616 }
3617
3618
3619 static void
arc_hdr_l2hdr_destroy(arc_buf_hdr_t * hdr)3620 arc_hdr_l2hdr_destroy(arc_buf_hdr_t *hdr)
3621 {
3622 l2arc_buf_hdr_t *l2hdr = &hdr->b_l2hdr;
3623 l2arc_dev_t *dev = l2hdr->b_dev;
3624 uint64_t psize = HDR_GET_PSIZE(hdr);
3625 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
3626
3627 ASSERT(MUTEX_HELD(&dev->l2ad_mtx));
3628 ASSERT(HDR_HAS_L2HDR(hdr));
3629
3630 list_remove(&dev->l2ad_buflist, hdr);
3631
3632 l2arc_hdr_arcstats_decrement(hdr);
3633 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
3634
3635 (void) zfs_refcount_remove_many(&dev->l2ad_alloc, arc_hdr_size(hdr),
3636 hdr);
3637 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
3638 }
3639
3640 static void
arc_hdr_destroy(arc_buf_hdr_t * hdr)3641 arc_hdr_destroy(arc_buf_hdr_t *hdr)
3642 {
3643 if (HDR_HAS_L1HDR(hdr)) {
3644 ASSERT(hdr->b_l1hdr.b_buf == NULL ||
3645 hdr->b_l1hdr.b_bufcnt > 0);
3646 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
3647 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
3648 }
3649 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3650 ASSERT(!HDR_IN_HASH_TABLE(hdr));
3651
3652 if (HDR_HAS_L2HDR(hdr)) {
3653 l2arc_dev_t *dev = hdr->b_l2hdr.b_dev;
3654 boolean_t buflist_held = MUTEX_HELD(&dev->l2ad_mtx);
3655
3656 if (!buflist_held)
3657 mutex_enter(&dev->l2ad_mtx);
3658
3659 /*
3660 * Even though we checked this conditional above, we
3661 * need to check this again now that we have the
3662 * l2ad_mtx. This is because we could be racing with
3663 * another thread calling l2arc_evict() which might have
3664 * destroyed this header's L2 portion as we were waiting
3665 * to acquire the l2ad_mtx. If that happens, we don't
3666 * want to re-destroy the header's L2 portion.
3667 */
3668 if (HDR_HAS_L2HDR(hdr))
3669 arc_hdr_l2hdr_destroy(hdr);
3670
3671 if (!buflist_held)
3672 mutex_exit(&dev->l2ad_mtx);
3673 }
3674
3675 /*
3676 * The header's identity can only be safely discarded once it is no
3677 * longer discoverable. This requires removing it from the hash table
3678 * and the l2arc header list. After this point the hash lock can not
3679 * be used to protect the header.
3680 */
3681 if (!HDR_EMPTY(hdr))
3682 buf_discard_identity(hdr);
3683
3684 if (HDR_HAS_L1HDR(hdr)) {
3685 arc_cksum_free(hdr);
3686
3687 while (hdr->b_l1hdr.b_buf != NULL)
3688 arc_buf_destroy_impl(hdr->b_l1hdr.b_buf);
3689
3690 #ifdef ZFS_DEBUG
3691 if (hdr->b_l1hdr.b_thawed != NULL) {
3692 kmem_free(hdr->b_l1hdr.b_thawed, 1);
3693 hdr->b_l1hdr.b_thawed = NULL;
3694 }
3695 #endif
3696
3697 if (hdr->b_l1hdr.b_pabd != NULL)
3698 arc_hdr_free_pabd(hdr, B_FALSE);
3699
3700 if (HDR_HAS_RABD(hdr))
3701 arc_hdr_free_pabd(hdr, B_TRUE);
3702 }
3703
3704 ASSERT3P(hdr->b_hash_next, ==, NULL);
3705 if (HDR_HAS_L1HDR(hdr)) {
3706 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
3707 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
3708
3709 if (!HDR_PROTECTED(hdr)) {
3710 kmem_cache_free(hdr_full_cache, hdr);
3711 } else {
3712 kmem_cache_free(hdr_full_crypt_cache, hdr);
3713 }
3714 } else {
3715 kmem_cache_free(hdr_l2only_cache, hdr);
3716 }
3717 }
3718
3719 void
arc_buf_destroy(arc_buf_t * buf,void * tag)3720 arc_buf_destroy(arc_buf_t *buf, void* tag)
3721 {
3722 arc_buf_hdr_t *hdr = buf->b_hdr;
3723
3724 if (hdr->b_l1hdr.b_state == arc_anon) {
3725 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
3726 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3727 VERIFY0(remove_reference(hdr, NULL, tag));
3728 arc_hdr_destroy(hdr);
3729 return;
3730 }
3731
3732 kmutex_t *hash_lock = HDR_LOCK(hdr);
3733 mutex_enter(hash_lock);
3734
3735 ASSERT3P(hdr, ==, buf->b_hdr);
3736 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
3737 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
3738 ASSERT3P(hdr->b_l1hdr.b_state, !=, arc_anon);
3739 ASSERT3P(buf->b_data, !=, NULL);
3740
3741 (void) remove_reference(hdr, hash_lock, tag);
3742 arc_buf_destroy_impl(buf);
3743 mutex_exit(hash_lock);
3744 }
3745
3746 /*
3747 * Evict the arc_buf_hdr that is provided as a parameter. The resultant
3748 * state of the header is dependent on its state prior to entering this
3749 * function. The following transitions are possible:
3750 *
3751 * - arc_mru -> arc_mru_ghost
3752 * - arc_mfu -> arc_mfu_ghost
3753 * - arc_mru_ghost -> arc_l2c_only
3754 * - arc_mru_ghost -> deleted
3755 * - arc_mfu_ghost -> arc_l2c_only
3756 * - arc_mfu_ghost -> deleted
3757 */
3758 static int64_t
arc_evict_hdr(arc_buf_hdr_t * hdr,kmutex_t * hash_lock)3759 arc_evict_hdr(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
3760 {
3761 arc_state_t *evicted_state, *state;
3762 int64_t bytes_evicted = 0;
3763 int min_lifetime = HDR_PRESCIENT_PREFETCH(hdr) ?
3764 zfs_arc_min_prescient_prefetch_ms : zfs_arc_min_prefetch_ms;
3765
3766 ASSERT(MUTEX_HELD(hash_lock));
3767 ASSERT(HDR_HAS_L1HDR(hdr));
3768
3769 state = hdr->b_l1hdr.b_state;
3770 if (GHOST_STATE(state)) {
3771 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
3772 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
3773
3774 /*
3775 * l2arc_write_buffers() relies on a header's L1 portion
3776 * (i.e. its b_pabd field) during its write phase.
3777 * Thus, we cannot push a header onto the arc_l2c_only
3778 * state (removing its L1 piece) until the header is
3779 * done being written to the l2arc.
3780 */
3781 if (HDR_HAS_L2HDR(hdr) && HDR_L2_WRITING(hdr)) {
3782 ARCSTAT_BUMP(arcstat_evict_l2_skip);
3783 return (bytes_evicted);
3784 }
3785
3786 ARCSTAT_BUMP(arcstat_deleted);
3787 bytes_evicted += HDR_GET_LSIZE(hdr);
3788
3789 DTRACE_PROBE1(arc__delete, arc_buf_hdr_t *, hdr);
3790
3791 if (HDR_HAS_L2HDR(hdr)) {
3792 ASSERT(hdr->b_l1hdr.b_pabd == NULL);
3793 ASSERT(!HDR_HAS_RABD(hdr));
3794 /*
3795 * This buffer is cached on the 2nd Level ARC;
3796 * don't destroy the header.
3797 */
3798 arc_change_state(arc_l2c_only, hdr, hash_lock);
3799 /*
3800 * dropping from L1+L2 cached to L2-only,
3801 * realloc to remove the L1 header.
3802 */
3803 hdr = arc_hdr_realloc(hdr, hdr_full_cache,
3804 hdr_l2only_cache);
3805 } else {
3806 arc_change_state(arc_anon, hdr, hash_lock);
3807 arc_hdr_destroy(hdr);
3808 }
3809 return (bytes_evicted);
3810 }
3811
3812 ASSERT(state == arc_mru || state == arc_mfu);
3813 evicted_state = (state == arc_mru) ? arc_mru_ghost : arc_mfu_ghost;
3814
3815 /* prefetch buffers have a minimum lifespan */
3816 if (HDR_IO_IN_PROGRESS(hdr) ||
3817 ((hdr->b_flags & (ARC_FLAG_PREFETCH | ARC_FLAG_INDIRECT)) &&
3818 ddi_get_lbolt() - hdr->b_l1hdr.b_arc_access < min_lifetime * hz)) {
3819 ARCSTAT_BUMP(arcstat_evict_skip);
3820 return (bytes_evicted);
3821 }
3822
3823 ASSERT0(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt));
3824 while (hdr->b_l1hdr.b_buf) {
3825 arc_buf_t *buf = hdr->b_l1hdr.b_buf;
3826 if (!mutex_tryenter(&buf->b_evict_lock)) {
3827 ARCSTAT_BUMP(arcstat_mutex_miss);
3828 break;
3829 }
3830 if (buf->b_data != NULL)
3831 bytes_evicted += HDR_GET_LSIZE(hdr);
3832 mutex_exit(&buf->b_evict_lock);
3833 arc_buf_destroy_impl(buf);
3834 }
3835
3836 if (HDR_HAS_L2HDR(hdr)) {
3837 ARCSTAT_INCR(arcstat_evict_l2_cached, HDR_GET_LSIZE(hdr));
3838 } else {
3839 if (l2arc_write_eligible(hdr->b_spa, hdr)) {
3840 ARCSTAT_INCR(arcstat_evict_l2_eligible,
3841 HDR_GET_LSIZE(hdr));
3842
3843 switch (state->arcs_state) {
3844 case ARC_STATE_MRU:
3845 ARCSTAT_INCR(
3846 arcstat_evict_l2_eligible_mru,
3847 HDR_GET_LSIZE(hdr));
3848 break;
3849 case ARC_STATE_MFU:
3850 ARCSTAT_INCR(
3851 arcstat_evict_l2_eligible_mfu,
3852 HDR_GET_LSIZE(hdr));
3853 break;
3854 default:
3855 break;
3856 }
3857 } else {
3858 ARCSTAT_INCR(arcstat_evict_l2_ineligible,
3859 HDR_GET_LSIZE(hdr));
3860 }
3861 }
3862
3863 if (hdr->b_l1hdr.b_bufcnt == 0) {
3864 arc_cksum_free(hdr);
3865
3866 bytes_evicted += arc_hdr_size(hdr);
3867
3868 /*
3869 * If this hdr is being evicted and has a compressed
3870 * buffer then we discard it here before we change states.
3871 * This ensures that the accounting is updated correctly
3872 * in arc_free_data_impl().
3873 */
3874 if (hdr->b_l1hdr.b_pabd != NULL)
3875 arc_hdr_free_pabd(hdr, B_FALSE);
3876
3877 if (HDR_HAS_RABD(hdr))
3878 arc_hdr_free_pabd(hdr, B_TRUE);
3879
3880 arc_change_state(evicted_state, hdr, hash_lock);
3881 ASSERT(HDR_IN_HASH_TABLE(hdr));
3882 arc_hdr_set_flags(hdr, ARC_FLAG_IN_HASH_TABLE);
3883 DTRACE_PROBE1(arc__evict, arc_buf_hdr_t *, hdr);
3884 }
3885
3886 return (bytes_evicted);
3887 }
3888
3889 static uint64_t
arc_evict_state_impl(multilist_t * ml,int idx,arc_buf_hdr_t * marker,uint64_t spa,int64_t bytes)3890 arc_evict_state_impl(multilist_t *ml, int idx, arc_buf_hdr_t *marker,
3891 uint64_t spa, int64_t bytes)
3892 {
3893 multilist_sublist_t *mls;
3894 uint64_t bytes_evicted = 0;
3895 arc_buf_hdr_t *hdr;
3896 kmutex_t *hash_lock;
3897 int evict_count = 0;
3898
3899 ASSERT3P(marker, !=, NULL);
3900 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
3901
3902 mls = multilist_sublist_lock(ml, idx);
3903
3904 for (hdr = multilist_sublist_prev(mls, marker); hdr != NULL;
3905 hdr = multilist_sublist_prev(mls, marker)) {
3906 if ((bytes != ARC_EVICT_ALL && bytes_evicted >= bytes) ||
3907 (evict_count >= zfs_arc_evict_batch_limit))
3908 break;
3909
3910 /*
3911 * To keep our iteration location, move the marker
3912 * forward. Since we're not holding hdr's hash lock, we
3913 * must be very careful and not remove 'hdr' from the
3914 * sublist. Otherwise, other consumers might mistake the
3915 * 'hdr' as not being on a sublist when they call the
3916 * multilist_link_active() function (they all rely on
3917 * the hash lock protecting concurrent insertions and
3918 * removals). multilist_sublist_move_forward() was
3919 * specifically implemented to ensure this is the case
3920 * (only 'marker' will be removed and re-inserted).
3921 */
3922 multilist_sublist_move_forward(mls, marker);
3923
3924 /*
3925 * The only case where the b_spa field should ever be
3926 * zero, is the marker headers inserted by
3927 * arc_evict_state(). It's possible for multiple threads
3928 * to be calling arc_evict_state() concurrently (e.g.
3929 * dsl_pool_close() and zio_inject_fault()), so we must
3930 * skip any markers we see from these other threads.
3931 */
3932 if (hdr->b_spa == 0)
3933 continue;
3934
3935 /* we're only interested in evicting buffers of a certain spa */
3936 if (spa != 0 && hdr->b_spa != spa) {
3937 ARCSTAT_BUMP(arcstat_evict_skip);
3938 continue;
3939 }
3940
3941 hash_lock = HDR_LOCK(hdr);
3942
3943 /*
3944 * We aren't calling this function from any code path
3945 * that would already be holding a hash lock, so we're
3946 * asserting on this assumption to be defensive in case
3947 * this ever changes. Without this check, it would be
3948 * possible to incorrectly increment arcstat_mutex_miss
3949 * below (e.g. if the code changed such that we called
3950 * this function with a hash lock held).
3951 */
3952 ASSERT(!MUTEX_HELD(hash_lock));
3953
3954 if (mutex_tryenter(hash_lock)) {
3955 uint64_t evicted = arc_evict_hdr(hdr, hash_lock);
3956 mutex_exit(hash_lock);
3957
3958 bytes_evicted += evicted;
3959
3960 /*
3961 * If evicted is zero, arc_evict_hdr() must have
3962 * decided to skip this header, don't increment
3963 * evict_count in this case.
3964 */
3965 if (evicted != 0)
3966 evict_count++;
3967
3968 /*
3969 * If arc_size isn't overflowing, signal any
3970 * threads that might happen to be waiting.
3971 *
3972 * For each header evicted, we wake up a single
3973 * thread. If we used cv_broadcast, we could
3974 * wake up "too many" threads causing arc_size
3975 * to significantly overflow arc_c; since
3976 * arc_get_data_impl() doesn't check for overflow
3977 * when it's woken up (it doesn't because it's
3978 * possible for the ARC to be overflowing while
3979 * full of un-evictable buffers, and the
3980 * function should proceed in this case).
3981 *
3982 * If threads are left sleeping, due to not
3983 * using cv_broadcast here, they will be woken
3984 * up via cv_broadcast in arc_adjust_cb() just
3985 * before arc_adjust_zthr sleeps.
3986 */
3987 mutex_enter(&arc_adjust_lock);
3988 if (!arc_is_overflowing())
3989 cv_signal(&arc_adjust_waiters_cv);
3990 mutex_exit(&arc_adjust_lock);
3991 } else {
3992 ARCSTAT_BUMP(arcstat_mutex_miss);
3993 }
3994 }
3995
3996 multilist_sublist_unlock(mls);
3997
3998 return (bytes_evicted);
3999 }
4000
4001 /*
4002 * Evict buffers from the given arc state, until we've removed the
4003 * specified number of bytes. Move the removed buffers to the
4004 * appropriate evict state.
4005 *
4006 * This function makes a "best effort". It skips over any buffers
4007 * it can't get a hash_lock on, and so, may not catch all candidates.
4008 * It may also return without evicting as much space as requested.
4009 *
4010 * If bytes is specified using the special value ARC_EVICT_ALL, this
4011 * will evict all available (i.e. unlocked and evictable) buffers from
4012 * the given arc state; which is used by arc_flush().
4013 */
4014 static uint64_t
arc_evict_state(arc_state_t * state,uint64_t spa,int64_t bytes,arc_buf_contents_t type)4015 arc_evict_state(arc_state_t *state, uint64_t spa, int64_t bytes,
4016 arc_buf_contents_t type)
4017 {
4018 uint64_t total_evicted = 0;
4019 multilist_t *ml = state->arcs_list[type];
4020 int num_sublists;
4021 arc_buf_hdr_t **markers;
4022
4023 IMPLY(bytes < 0, bytes == ARC_EVICT_ALL);
4024
4025 num_sublists = multilist_get_num_sublists(ml);
4026
4027 /*
4028 * If we've tried to evict from each sublist, made some
4029 * progress, but still have not hit the target number of bytes
4030 * to evict, we want to keep trying. The markers allow us to
4031 * pick up where we left off for each individual sublist, rather
4032 * than starting from the tail each time.
4033 */
4034 markers = kmem_zalloc(sizeof (*markers) * num_sublists, KM_SLEEP);
4035 for (int i = 0; i < num_sublists; i++) {
4036 markers[i] = kmem_cache_alloc(hdr_full_cache, KM_SLEEP);
4037
4038 /*
4039 * A b_spa of 0 is used to indicate that this header is
4040 * a marker. This fact is used in arc_adjust_type() and
4041 * arc_evict_state_impl().
4042 */
4043 markers[i]->b_spa = 0;
4044
4045 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4046 multilist_sublist_insert_tail(mls, markers[i]);
4047 multilist_sublist_unlock(mls);
4048 }
4049
4050 /*
4051 * While we haven't hit our target number of bytes to evict, or
4052 * we're evicting all available buffers.
4053 */
4054 while (total_evicted < bytes || bytes == ARC_EVICT_ALL) {
4055 /*
4056 * Start eviction using a randomly selected sublist,
4057 * this is to try and evenly balance eviction across all
4058 * sublists. Always starting at the same sublist
4059 * (e.g. index 0) would cause evictions to favor certain
4060 * sublists over others.
4061 */
4062 int sublist_idx = multilist_get_random_index(ml);
4063 uint64_t scan_evicted = 0;
4064
4065 for (int i = 0; i < num_sublists; i++) {
4066 uint64_t bytes_remaining;
4067 uint64_t bytes_evicted;
4068
4069 if (bytes == ARC_EVICT_ALL)
4070 bytes_remaining = ARC_EVICT_ALL;
4071 else if (total_evicted < bytes)
4072 bytes_remaining = bytes - total_evicted;
4073 else
4074 break;
4075
4076 bytes_evicted = arc_evict_state_impl(ml, sublist_idx,
4077 markers[sublist_idx], spa, bytes_remaining);
4078
4079 scan_evicted += bytes_evicted;
4080 total_evicted += bytes_evicted;
4081
4082 /* we've reached the end, wrap to the beginning */
4083 if (++sublist_idx >= num_sublists)
4084 sublist_idx = 0;
4085 }
4086
4087 /*
4088 * If we didn't evict anything during this scan, we have
4089 * no reason to believe we'll evict more during another
4090 * scan, so break the loop.
4091 */
4092 if (scan_evicted == 0) {
4093 /* This isn't possible, let's make that obvious */
4094 ASSERT3S(bytes, !=, 0);
4095
4096 /*
4097 * When bytes is ARC_EVICT_ALL, the only way to
4098 * break the loop is when scan_evicted is zero.
4099 * In that case, we actually have evicted enough,
4100 * so we don't want to increment the kstat.
4101 */
4102 if (bytes != ARC_EVICT_ALL) {
4103 ASSERT3S(total_evicted, <, bytes);
4104 ARCSTAT_BUMP(arcstat_evict_not_enough);
4105 }
4106
4107 break;
4108 }
4109 }
4110
4111 for (int i = 0; i < num_sublists; i++) {
4112 multilist_sublist_t *mls = multilist_sublist_lock(ml, i);
4113 multilist_sublist_remove(mls, markers[i]);
4114 multilist_sublist_unlock(mls);
4115
4116 kmem_cache_free(hdr_full_cache, markers[i]);
4117 }
4118 kmem_free(markers, sizeof (*markers) * num_sublists);
4119
4120 return (total_evicted);
4121 }
4122
4123 /*
4124 * Flush all "evictable" data of the given type from the arc state
4125 * specified. This will not evict any "active" buffers (i.e. referenced).
4126 *
4127 * When 'retry' is set to B_FALSE, the function will make a single pass
4128 * over the state and evict any buffers that it can. Since it doesn't
4129 * continually retry the eviction, it might end up leaving some buffers
4130 * in the ARC due to lock misses.
4131 *
4132 * When 'retry' is set to B_TRUE, the function will continually retry the
4133 * eviction until *all* evictable buffers have been removed from the
4134 * state. As a result, if concurrent insertions into the state are
4135 * allowed (e.g. if the ARC isn't shutting down), this function might
4136 * wind up in an infinite loop, continually trying to evict buffers.
4137 */
4138 static uint64_t
arc_flush_state(arc_state_t * state,uint64_t spa,arc_buf_contents_t type,boolean_t retry)4139 arc_flush_state(arc_state_t *state, uint64_t spa, arc_buf_contents_t type,
4140 boolean_t retry)
4141 {
4142 uint64_t evicted = 0;
4143
4144 while (zfs_refcount_count(&state->arcs_esize[type]) != 0) {
4145 evicted += arc_evict_state(state, spa, ARC_EVICT_ALL, type);
4146
4147 if (!retry)
4148 break;
4149 }
4150
4151 return (evicted);
4152 }
4153
4154 /*
4155 * Evict the specified number of bytes from the state specified,
4156 * restricting eviction to the spa and type given. This function
4157 * prevents us from trying to evict more from a state's list than
4158 * is "evictable", and to skip evicting altogether when passed a
4159 * negative value for "bytes". In contrast, arc_evict_state() will
4160 * evict everything it can, when passed a negative value for "bytes".
4161 */
4162 static uint64_t
arc_adjust_impl(arc_state_t * state,uint64_t spa,int64_t bytes,arc_buf_contents_t type)4163 arc_adjust_impl(arc_state_t *state, uint64_t spa, int64_t bytes,
4164 arc_buf_contents_t type)
4165 {
4166 int64_t delta;
4167
4168 if (bytes > 0 && zfs_refcount_count(&state->arcs_esize[type]) > 0) {
4169 delta = MIN(zfs_refcount_count(&state->arcs_esize[type]),
4170 bytes);
4171 return (arc_evict_state(state, spa, delta, type));
4172 }
4173
4174 return (0);
4175 }
4176
4177 /*
4178 * Evict metadata buffers from the cache, such that arc_meta_used is
4179 * capped by the arc_meta_limit tunable.
4180 */
4181 static uint64_t
arc_adjust_meta(uint64_t meta_used)4182 arc_adjust_meta(uint64_t meta_used)
4183 {
4184 uint64_t total_evicted = 0;
4185 int64_t target;
4186
4187 /*
4188 * If we're over the meta limit, we want to evict enough
4189 * metadata to get back under the meta limit. We don't want to
4190 * evict so much that we drop the MRU below arc_p, though. If
4191 * we're over the meta limit more than we're over arc_p, we
4192 * evict some from the MRU here, and some from the MFU below.
4193 */
4194 target = MIN((int64_t)(meta_used - arc_meta_limit),
4195 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) +
4196 zfs_refcount_count(&arc_mru->arcs_size) - arc_p));
4197
4198 total_evicted += arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4199
4200 /*
4201 * Similar to the above, we want to evict enough bytes to get us
4202 * below the meta limit, but not so much as to drop us below the
4203 * space allotted to the MFU (which is defined as arc_c - arc_p).
4204 */
4205 target = MIN((int64_t)(meta_used - arc_meta_limit),
4206 (int64_t)(zfs_refcount_count(&arc_mfu->arcs_size) -
4207 (arc_c - arc_p)));
4208
4209 total_evicted += arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4210
4211 return (total_evicted);
4212 }
4213
4214 /*
4215 * Return the type of the oldest buffer in the given arc state
4216 *
4217 * This function will select a random sublist of type ARC_BUFC_DATA and
4218 * a random sublist of type ARC_BUFC_METADATA. The tail of each sublist
4219 * is compared, and the type which contains the "older" buffer will be
4220 * returned.
4221 */
4222 static arc_buf_contents_t
arc_adjust_type(arc_state_t * state)4223 arc_adjust_type(arc_state_t *state)
4224 {
4225 multilist_t *data_ml = state->arcs_list[ARC_BUFC_DATA];
4226 multilist_t *meta_ml = state->arcs_list[ARC_BUFC_METADATA];
4227 int data_idx = multilist_get_random_index(data_ml);
4228 int meta_idx = multilist_get_random_index(meta_ml);
4229 multilist_sublist_t *data_mls;
4230 multilist_sublist_t *meta_mls;
4231 arc_buf_contents_t type;
4232 arc_buf_hdr_t *data_hdr;
4233 arc_buf_hdr_t *meta_hdr;
4234
4235 /*
4236 * We keep the sublist lock until we're finished, to prevent
4237 * the headers from being destroyed via arc_evict_state().
4238 */
4239 data_mls = multilist_sublist_lock(data_ml, data_idx);
4240 meta_mls = multilist_sublist_lock(meta_ml, meta_idx);
4241
4242 /*
4243 * These two loops are to ensure we skip any markers that
4244 * might be at the tail of the lists due to arc_evict_state().
4245 */
4246
4247 for (data_hdr = multilist_sublist_tail(data_mls); data_hdr != NULL;
4248 data_hdr = multilist_sublist_prev(data_mls, data_hdr)) {
4249 if (data_hdr->b_spa != 0)
4250 break;
4251 }
4252
4253 for (meta_hdr = multilist_sublist_tail(meta_mls); meta_hdr != NULL;
4254 meta_hdr = multilist_sublist_prev(meta_mls, meta_hdr)) {
4255 if (meta_hdr->b_spa != 0)
4256 break;
4257 }
4258
4259 if (data_hdr == NULL && meta_hdr == NULL) {
4260 type = ARC_BUFC_DATA;
4261 } else if (data_hdr == NULL) {
4262 ASSERT3P(meta_hdr, !=, NULL);
4263 type = ARC_BUFC_METADATA;
4264 } else if (meta_hdr == NULL) {
4265 ASSERT3P(data_hdr, !=, NULL);
4266 type = ARC_BUFC_DATA;
4267 } else {
4268 ASSERT3P(data_hdr, !=, NULL);
4269 ASSERT3P(meta_hdr, !=, NULL);
4270
4271 /* The headers can't be on the sublist without an L1 header */
4272 ASSERT(HDR_HAS_L1HDR(data_hdr));
4273 ASSERT(HDR_HAS_L1HDR(meta_hdr));
4274
4275 if (data_hdr->b_l1hdr.b_arc_access <
4276 meta_hdr->b_l1hdr.b_arc_access) {
4277 type = ARC_BUFC_DATA;
4278 } else {
4279 type = ARC_BUFC_METADATA;
4280 }
4281 }
4282
4283 multilist_sublist_unlock(meta_mls);
4284 multilist_sublist_unlock(data_mls);
4285
4286 return (type);
4287 }
4288
4289 /*
4290 * Evict buffers from the cache, such that arc_size is capped by arc_c.
4291 */
4292 static uint64_t
arc_adjust(void)4293 arc_adjust(void)
4294 {
4295 uint64_t total_evicted = 0;
4296 uint64_t bytes;
4297 int64_t target;
4298 uint64_t asize = aggsum_value(&arc_size);
4299 uint64_t ameta = aggsum_value(&arc_meta_used);
4300
4301 /*
4302 * If we're over arc_meta_limit, we want to correct that before
4303 * potentially evicting data buffers below.
4304 */
4305 total_evicted += arc_adjust_meta(ameta);
4306
4307 /*
4308 * Adjust MRU size
4309 *
4310 * If we're over the target cache size, we want to evict enough
4311 * from the list to get back to our target size. We don't want
4312 * to evict too much from the MRU, such that it drops below
4313 * arc_p. So, if we're over our target cache size more than
4314 * the MRU is over arc_p, we'll evict enough to get back to
4315 * arc_p here, and then evict more from the MFU below.
4316 */
4317 target = MIN((int64_t)(asize - arc_c),
4318 (int64_t)(zfs_refcount_count(&arc_anon->arcs_size) +
4319 zfs_refcount_count(&arc_mru->arcs_size) + ameta - arc_p));
4320
4321 /*
4322 * If we're below arc_meta_min, always prefer to evict data.
4323 * Otherwise, try to satisfy the requested number of bytes to
4324 * evict from the type which contains older buffers; in an
4325 * effort to keep newer buffers in the cache regardless of their
4326 * type. If we cannot satisfy the number of bytes from this
4327 * type, spill over into the next type.
4328 */
4329 if (arc_adjust_type(arc_mru) == ARC_BUFC_METADATA &&
4330 ameta > arc_meta_min) {
4331 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4332 total_evicted += bytes;
4333
4334 /*
4335 * If we couldn't evict our target number of bytes from
4336 * metadata, we try to get the rest from data.
4337 */
4338 target -= bytes;
4339
4340 total_evicted +=
4341 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4342 } else {
4343 bytes = arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_DATA);
4344 total_evicted += bytes;
4345
4346 /*
4347 * If we couldn't evict our target number of bytes from
4348 * data, we try to get the rest from metadata.
4349 */
4350 target -= bytes;
4351
4352 total_evicted +=
4353 arc_adjust_impl(arc_mru, 0, target, ARC_BUFC_METADATA);
4354 }
4355
4356 /*
4357 * Adjust MFU size
4358 *
4359 * Now that we've tried to evict enough from the MRU to get its
4360 * size back to arc_p, if we're still above the target cache
4361 * size, we evict the rest from the MFU.
4362 */
4363 target = asize - arc_c;
4364
4365 if (arc_adjust_type(arc_mfu) == ARC_BUFC_METADATA &&
4366 ameta > arc_meta_min) {
4367 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4368 total_evicted += bytes;
4369
4370 /*
4371 * If we couldn't evict our target number of bytes from
4372 * metadata, we try to get the rest from data.
4373 */
4374 target -= bytes;
4375
4376 total_evicted +=
4377 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4378 } else {
4379 bytes = arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_DATA);
4380 total_evicted += bytes;
4381
4382 /*
4383 * If we couldn't evict our target number of bytes from
4384 * data, we try to get the rest from data.
4385 */
4386 target -= bytes;
4387
4388 total_evicted +=
4389 arc_adjust_impl(arc_mfu, 0, target, ARC_BUFC_METADATA);
4390 }
4391
4392 /*
4393 * Adjust ghost lists
4394 *
4395 * In addition to the above, the ARC also defines target values
4396 * for the ghost lists. The sum of the mru list and mru ghost
4397 * list should never exceed the target size of the cache, and
4398 * the sum of the mru list, mfu list, mru ghost list, and mfu
4399 * ghost list should never exceed twice the target size of the
4400 * cache. The following logic enforces these limits on the ghost
4401 * caches, and evicts from them as needed.
4402 */
4403 target = zfs_refcount_count(&arc_mru->arcs_size) +
4404 zfs_refcount_count(&arc_mru_ghost->arcs_size) - arc_c;
4405
4406 bytes = arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_DATA);
4407 total_evicted += bytes;
4408
4409 target -= bytes;
4410
4411 total_evicted +=
4412 arc_adjust_impl(arc_mru_ghost, 0, target, ARC_BUFC_METADATA);
4413
4414 /*
4415 * We assume the sum of the mru list and mfu list is less than
4416 * or equal to arc_c (we enforced this above), which means we
4417 * can use the simpler of the two equations below:
4418 *
4419 * mru + mfu + mru ghost + mfu ghost <= 2 * arc_c
4420 * mru ghost + mfu ghost <= arc_c
4421 */
4422 target = zfs_refcount_count(&arc_mru_ghost->arcs_size) +
4423 zfs_refcount_count(&arc_mfu_ghost->arcs_size) - arc_c;
4424
4425 bytes = arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_DATA);
4426 total_evicted += bytes;
4427
4428 target -= bytes;
4429
4430 total_evicted +=
4431 arc_adjust_impl(arc_mfu_ghost, 0, target, ARC_BUFC_METADATA);
4432
4433 return (total_evicted);
4434 }
4435
4436 void
arc_flush(spa_t * spa,boolean_t retry)4437 arc_flush(spa_t *spa, boolean_t retry)
4438 {
4439 uint64_t guid = 0;
4440
4441 /*
4442 * If retry is B_TRUE, a spa must not be specified since we have
4443 * no good way to determine if all of a spa's buffers have been
4444 * evicted from an arc state.
4445 */
4446 ASSERT(!retry || spa == 0);
4447
4448 if (spa != NULL)
4449 guid = spa_load_guid(spa);
4450
4451 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_DATA, retry);
4452 (void) arc_flush_state(arc_mru, guid, ARC_BUFC_METADATA, retry);
4453
4454 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_DATA, retry);
4455 (void) arc_flush_state(arc_mfu, guid, ARC_BUFC_METADATA, retry);
4456
4457 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_DATA, retry);
4458 (void) arc_flush_state(arc_mru_ghost, guid, ARC_BUFC_METADATA, retry);
4459
4460 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_DATA, retry);
4461 (void) arc_flush_state(arc_mfu_ghost, guid, ARC_BUFC_METADATA, retry);
4462 }
4463
4464 static void
arc_reduce_target_size(int64_t to_free)4465 arc_reduce_target_size(int64_t to_free)
4466 {
4467 uint64_t asize = aggsum_value(&arc_size);
4468 if (arc_c > arc_c_min) {
4469
4470 if (arc_c > arc_c_min + to_free)
4471 atomic_add_64(&arc_c, -to_free);
4472 else
4473 arc_c = arc_c_min;
4474
4475 atomic_add_64(&arc_p, -(arc_p >> arc_shrink_shift));
4476 if (asize < arc_c)
4477 arc_c = MAX(asize, arc_c_min);
4478 if (arc_p > arc_c)
4479 arc_p = (arc_c >> 1);
4480 ASSERT(arc_c >= arc_c_min);
4481 ASSERT((int64_t)arc_p >= 0);
4482 }
4483
4484 if (asize > arc_c) {
4485 /* See comment in arc_adjust_cb_check() on why lock+flag */
4486 mutex_enter(&arc_adjust_lock);
4487 arc_adjust_needed = B_TRUE;
4488 mutex_exit(&arc_adjust_lock);
4489 zthr_wakeup(arc_adjust_zthr);
4490 }
4491 }
4492
4493 typedef enum free_memory_reason_t {
4494 FMR_UNKNOWN,
4495 FMR_NEEDFREE,
4496 FMR_LOTSFREE,
4497 FMR_SWAPFS_MINFREE,
4498 FMR_PAGES_PP_MAXIMUM,
4499 FMR_HEAP_ARENA,
4500 FMR_ZIO_ARENA,
4501 } free_memory_reason_t;
4502
4503 int64_t last_free_memory;
4504 free_memory_reason_t last_free_reason;
4505
4506 /*
4507 * Additional reserve of pages for pp_reserve.
4508 */
4509 int64_t arc_pages_pp_reserve = 64;
4510
4511 /*
4512 * Additional reserve of pages for swapfs.
4513 */
4514 int64_t arc_swapfs_reserve = 64;
4515
4516 /*
4517 * Return the amount of memory that can be consumed before reclaim will be
4518 * needed. Positive if there is sufficient free memory, negative indicates
4519 * the amount of memory that needs to be freed up.
4520 */
4521 static int64_t
arc_available_memory(void)4522 arc_available_memory(void)
4523 {
4524 int64_t lowest = INT64_MAX;
4525 int64_t n;
4526 free_memory_reason_t r = FMR_UNKNOWN;
4527
4528 #ifdef _KERNEL
4529 if (needfree > 0) {
4530 n = PAGESIZE * (-needfree);
4531 if (n < lowest) {
4532 lowest = n;
4533 r = FMR_NEEDFREE;
4534 }
4535 }
4536
4537 /*
4538 * check that we're out of range of the pageout scanner. It starts to
4539 * schedule paging if freemem is less than lotsfree and needfree.
4540 * lotsfree is the high-water mark for pageout, and needfree is the
4541 * number of needed free pages. We add extra pages here to make sure
4542 * the scanner doesn't start up while we're freeing memory.
4543 */
4544 n = PAGESIZE * (freemem - lotsfree - needfree - desfree);
4545 if (n < lowest) {
4546 lowest = n;
4547 r = FMR_LOTSFREE;
4548 }
4549
4550 /*
4551 * check to make sure that swapfs has enough space so that anon
4552 * reservations can still succeed. anon_resvmem() checks that the
4553 * availrmem is greater than swapfs_minfree, and the number of reserved
4554 * swap pages. We also add a bit of extra here just to prevent
4555 * circumstances from getting really dire.
4556 */
4557 n = PAGESIZE * (availrmem - swapfs_minfree - swapfs_reserve -
4558 desfree - arc_swapfs_reserve);
4559 if (n < lowest) {
4560 lowest = n;
4561 r = FMR_SWAPFS_MINFREE;
4562 }
4563
4564
4565 /*
4566 * Check that we have enough availrmem that memory locking (e.g., via
4567 * mlock(3C) or memcntl(2)) can still succeed. (pages_pp_maximum
4568 * stores the number of pages that cannot be locked; when availrmem
4569 * drops below pages_pp_maximum, page locking mechanisms such as
4570 * page_pp_lock() will fail.)
4571 */
4572 n = PAGESIZE * (availrmem - pages_pp_maximum -
4573 arc_pages_pp_reserve);
4574 if (n < lowest) {
4575 lowest = n;
4576 r = FMR_PAGES_PP_MAXIMUM;
4577 }
4578
4579
4580 /*
4581 * If zio data pages are being allocated out of a separate heap segment,
4582 * then enforce that the size of available vmem for this arena remains
4583 * above about 1/4th (1/(2^arc_zio_arena_free_shift)) free.
4584 *
4585 * Note that reducing the arc_zio_arena_free_shift keeps more virtual
4586 * memory (in the zio_arena) free, which can avoid memory
4587 * fragmentation issues.
4588 */
4589 if (zio_arena != NULL) {
4590 n = (int64_t)vmem_size(zio_arena, VMEM_FREE) -
4591 (vmem_size(zio_arena, VMEM_ALLOC) >>
4592 arc_zio_arena_free_shift);
4593 if (n < lowest) {
4594 lowest = n;
4595 r = FMR_ZIO_ARENA;
4596 }
4597 }
4598 #else
4599 /* Every 100 calls, free a small amount */
4600 if (spa_get_random(100) == 0)
4601 lowest = -1024;
4602 #endif
4603
4604 last_free_memory = lowest;
4605 last_free_reason = r;
4606
4607 return (lowest);
4608 }
4609
4610
4611 /*
4612 * Determine if the system is under memory pressure and is asking
4613 * to reclaim memory. A return value of B_TRUE indicates that the system
4614 * is under memory pressure and that the arc should adjust accordingly.
4615 */
4616 static boolean_t
arc_reclaim_needed(void)4617 arc_reclaim_needed(void)
4618 {
4619 return (arc_available_memory() < 0);
4620 }
4621
4622 static void
arc_kmem_reap_soon(void)4623 arc_kmem_reap_soon(void)
4624 {
4625 size_t i;
4626 kmem_cache_t *prev_cache = NULL;
4627 kmem_cache_t *prev_data_cache = NULL;
4628 extern kmem_cache_t *zio_buf_cache[];
4629 extern kmem_cache_t *zio_data_buf_cache[];
4630 extern kmem_cache_t *zfs_btree_leaf_cache;
4631 extern kmem_cache_t *abd_chunk_cache;
4632
4633 #ifdef _KERNEL
4634 if (aggsum_compare(&arc_meta_used, arc_meta_limit) >= 0) {
4635 /*
4636 * We are exceeding our meta-data cache limit.
4637 * Purge some DNLC entries to release holds on meta-data.
4638 */
4639 dnlc_reduce_cache((void *)(uintptr_t)arc_reduce_dnlc_percent);
4640 }
4641 #endif
4642
4643 for (i = 0; i < SPA_MAXBLOCKSIZE >> SPA_MINBLOCKSHIFT; i++) {
4644 if (zio_buf_cache[i] != prev_cache) {
4645 prev_cache = zio_buf_cache[i];
4646 kmem_cache_reap_soon(zio_buf_cache[i]);
4647 }
4648 if (zio_data_buf_cache[i] != prev_data_cache) {
4649 prev_data_cache = zio_data_buf_cache[i];
4650 kmem_cache_reap_soon(zio_data_buf_cache[i]);
4651 }
4652 }
4653 kmem_cache_reap_soon(abd_chunk_cache);
4654 kmem_cache_reap_soon(buf_cache);
4655 kmem_cache_reap_soon(hdr_full_cache);
4656 kmem_cache_reap_soon(hdr_l2only_cache);
4657 kmem_cache_reap_soon(zfs_btree_leaf_cache);
4658
4659 if (zio_arena != NULL) {
4660 /*
4661 * Ask the vmem arena to reclaim unused memory from its
4662 * quantum caches.
4663 */
4664 vmem_qcache_reap(zio_arena);
4665 }
4666 }
4667
4668 /* ARGSUSED */
4669 static boolean_t
arc_adjust_cb_check(void * arg,zthr_t * zthr)4670 arc_adjust_cb_check(void *arg, zthr_t *zthr)
4671 {
4672 /*
4673 * This is necessary in order for the mdb ::arc dcmd to
4674 * show up to date information. Since the ::arc command
4675 * does not call the kstat's update function, without
4676 * this call, the command may show stale stats for the
4677 * anon, mru, mru_ghost, mfu, and mfu_ghost lists. Even
4678 * with this change, the data might be up to 1 second
4679 * out of date(the arc_adjust_zthr has a maximum sleep
4680 * time of 1 second); but that should suffice. The
4681 * arc_state_t structures can be queried directly if more
4682 * accurate information is needed.
4683 */
4684 if (arc_ksp != NULL)
4685 arc_ksp->ks_update(arc_ksp, KSTAT_READ);
4686
4687 /*
4688 * We have to rely on arc_get_data_impl() to tell us when to adjust,
4689 * rather than checking if we are overflowing here, so that we are
4690 * sure to not leave arc_get_data_impl() waiting on
4691 * arc_adjust_waiters_cv. If we have become "not overflowing" since
4692 * arc_get_data_impl() checked, we need to wake it up. We could
4693 * broadcast the CV here, but arc_get_data_impl() may have not yet
4694 * gone to sleep. We would need to use a mutex to ensure that this
4695 * function doesn't broadcast until arc_get_data_impl() has gone to
4696 * sleep (e.g. the arc_adjust_lock). However, the lock ordering of
4697 * such a lock would necessarily be incorrect with respect to the
4698 * zthr_lock, which is held before this function is called, and is
4699 * held by arc_get_data_impl() when it calls zthr_wakeup().
4700 */
4701 return (arc_adjust_needed);
4702 }
4703
4704 /*
4705 * Keep arc_size under arc_c by running arc_adjust which evicts data
4706 * from the ARC.
4707 */
4708 /* ARGSUSED */
4709 static void
arc_adjust_cb(void * arg,zthr_t * zthr)4710 arc_adjust_cb(void *arg, zthr_t *zthr)
4711 {
4712 uint64_t evicted = 0;
4713
4714 /* Evict from cache */
4715 evicted = arc_adjust();
4716
4717 /*
4718 * If evicted is zero, we couldn't evict anything
4719 * via arc_adjust(). This could be due to hash lock
4720 * collisions, but more likely due to the majority of
4721 * arc buffers being unevictable. Therefore, even if
4722 * arc_size is above arc_c, another pass is unlikely to
4723 * be helpful and could potentially cause us to enter an
4724 * infinite loop. Additionally, zthr_iscancelled() is
4725 * checked here so that if the arc is shutting down, the
4726 * broadcast will wake any remaining arc adjust waiters.
4727 */
4728 mutex_enter(&arc_adjust_lock);
4729 arc_adjust_needed = !zthr_iscancelled(arc_adjust_zthr) &&
4730 evicted > 0 && aggsum_compare(&arc_size, arc_c) > 0;
4731 if (!arc_adjust_needed) {
4732 /*
4733 * We're either no longer overflowing, or we
4734 * can't evict anything more, so we should wake
4735 * up any waiters.
4736 */
4737 cv_broadcast(&arc_adjust_waiters_cv);
4738 }
4739 mutex_exit(&arc_adjust_lock);
4740 }
4741
4742 /* ARGSUSED */
4743 static boolean_t
arc_reap_cb_check(void * arg,zthr_t * zthr)4744 arc_reap_cb_check(void *arg, zthr_t *zthr)
4745 {
4746 int64_t free_memory = arc_available_memory();
4747
4748 /*
4749 * If a kmem reap is already active, don't schedule more. We must
4750 * check for this because kmem_cache_reap_soon() won't actually
4751 * block on the cache being reaped (this is to prevent callers from
4752 * becoming implicitly blocked by a system-wide kmem reap -- which,
4753 * on a system with many, many full magazines, can take minutes).
4754 */
4755 if (!kmem_cache_reap_active() &&
4756 free_memory < 0) {
4757 arc_no_grow = B_TRUE;
4758 arc_warm = B_TRUE;
4759 /*
4760 * Wait at least zfs_grow_retry (default 60) seconds
4761 * before considering growing.
4762 */
4763 arc_growtime = gethrtime() + SEC2NSEC(arc_grow_retry);
4764 return (B_TRUE);
4765 } else if (free_memory < arc_c >> arc_no_grow_shift) {
4766 arc_no_grow = B_TRUE;
4767 } else if (gethrtime() >= arc_growtime) {
4768 arc_no_grow = B_FALSE;
4769 }
4770
4771 return (B_FALSE);
4772 }
4773
4774 /*
4775 * Keep enough free memory in the system by reaping the ARC's kmem
4776 * caches. To cause more slabs to be reapable, we may reduce the
4777 * target size of the cache (arc_c), causing the arc_adjust_cb()
4778 * to free more buffers.
4779 */
4780 /* ARGSUSED */
4781 static void
arc_reap_cb(void * arg,zthr_t * zthr)4782 arc_reap_cb(void *arg, zthr_t *zthr)
4783 {
4784 int64_t free_memory;
4785
4786 /*
4787 * Kick off asynchronous kmem_reap()'s of all our caches.
4788 */
4789 arc_kmem_reap_soon();
4790
4791 /*
4792 * Wait at least arc_kmem_cache_reap_retry_ms between
4793 * arc_kmem_reap_soon() calls. Without this check it is possible to
4794 * end up in a situation where we spend lots of time reaping
4795 * caches, while we're near arc_c_min. Waiting here also gives the
4796 * subsequent free memory check a chance of finding that the
4797 * asynchronous reap has already freed enough memory, and we don't
4798 * need to call arc_reduce_target_size().
4799 */
4800 delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000);
4801
4802 /*
4803 * Reduce the target size as needed to maintain the amount of free
4804 * memory in the system at a fraction of the arc_size (1/128th by
4805 * default). If oversubscribed (free_memory < 0) then reduce the
4806 * target arc_size by the deficit amount plus the fractional
4807 * amount. If free memory is positive but less then the fractional
4808 * amount, reduce by what is needed to hit the fractional amount.
4809 */
4810 free_memory = arc_available_memory();
4811
4812 int64_t to_free =
4813 (arc_c >> arc_shrink_shift) - free_memory;
4814 if (to_free > 0) {
4815 #ifdef _KERNEL
4816 to_free = MAX(to_free, ptob(needfree));
4817 #endif
4818 arc_reduce_target_size(to_free);
4819 }
4820 }
4821
4822 /*
4823 * Adapt arc info given the number of bytes we are trying to add and
4824 * the state that we are coming from. This function is only called
4825 * when we are adding new content to the cache.
4826 */
4827 static void
arc_adapt(int bytes,arc_state_t * state)4828 arc_adapt(int bytes, arc_state_t *state)
4829 {
4830 int mult;
4831 uint64_t arc_p_min = (arc_c >> arc_p_min_shift);
4832 int64_t mrug_size = zfs_refcount_count(&arc_mru_ghost->arcs_size);
4833 int64_t mfug_size = zfs_refcount_count(&arc_mfu_ghost->arcs_size);
4834
4835 ASSERT(bytes > 0);
4836 /*
4837 * Adapt the target size of the MRU list:
4838 * - if we just hit in the MRU ghost list, then increase
4839 * the target size of the MRU list.
4840 * - if we just hit in the MFU ghost list, then increase
4841 * the target size of the MFU list by decreasing the
4842 * target size of the MRU list.
4843 */
4844 if (state == arc_mru_ghost) {
4845 mult = (mrug_size >= mfug_size) ? 1 : (mfug_size / mrug_size);
4846 mult = MIN(mult, 10); /* avoid wild arc_p adjustment */
4847
4848 arc_p = MIN(arc_c - arc_p_min, arc_p + bytes * mult);
4849 } else if (state == arc_mfu_ghost) {
4850 uint64_t delta;
4851
4852 mult = (mfug_size >= mrug_size) ? 1 : (mrug_size / mfug_size);
4853 mult = MIN(mult, 10);
4854
4855 delta = MIN(bytes * mult, arc_p);
4856 arc_p = MAX(arc_p_min, arc_p - delta);
4857 }
4858 ASSERT((int64_t)arc_p >= 0);
4859
4860 /*
4861 * Wake reap thread if we do not have any available memory
4862 */
4863 if (arc_reclaim_needed()) {
4864 zthr_wakeup(arc_reap_zthr);
4865 return;
4866 }
4867
4868
4869 if (arc_no_grow)
4870 return;
4871
4872 if (arc_c >= arc_c_max)
4873 return;
4874
4875 /*
4876 * If we're within (2 * maxblocksize) bytes of the target
4877 * cache size, increment the target cache size
4878 */
4879 if (aggsum_compare(&arc_size, arc_c - (2ULL << SPA_MAXBLOCKSHIFT)) >
4880 0) {
4881 atomic_add_64(&arc_c, (int64_t)bytes);
4882 if (arc_c > arc_c_max)
4883 arc_c = arc_c_max;
4884 else if (state == arc_anon)
4885 atomic_add_64(&arc_p, (int64_t)bytes);
4886 if (arc_p > arc_c)
4887 arc_p = arc_c;
4888 }
4889 ASSERT((int64_t)arc_p >= 0);
4890 }
4891
4892 /*
4893 * Check if arc_size has grown past our upper threshold, determined by
4894 * zfs_arc_overflow_shift.
4895 */
4896 static boolean_t
arc_is_overflowing(void)4897 arc_is_overflowing(void)
4898 {
4899 /* Always allow at least one block of overflow */
4900 uint64_t overflow = MAX(SPA_MAXBLOCKSIZE,
4901 arc_c >> zfs_arc_overflow_shift);
4902
4903 /*
4904 * We just compare the lower bound here for performance reasons. Our
4905 * primary goals are to make sure that the arc never grows without
4906 * bound, and that it can reach its maximum size. This check
4907 * accomplishes both goals. The maximum amount we could run over by is
4908 * 2 * aggsum_borrow_multiplier * NUM_CPUS * the average size of a block
4909 * in the ARC. In practice, that's in the tens of MB, which is low
4910 * enough to be safe.
4911 */
4912 return (aggsum_lower_bound(&arc_size) >= arc_c + overflow);
4913 }
4914
4915 static abd_t *
arc_get_data_abd(arc_buf_hdr_t * hdr,uint64_t size,void * tag,boolean_t do_adapt)4916 arc_get_data_abd(arc_buf_hdr_t *hdr, uint64_t size, void *tag,
4917 boolean_t do_adapt)
4918 {
4919 arc_buf_contents_t type = arc_buf_type(hdr);
4920
4921 arc_get_data_impl(hdr, size, tag, do_adapt);
4922 if (type == ARC_BUFC_METADATA) {
4923 return (abd_alloc(size, B_TRUE));
4924 } else {
4925 ASSERT(type == ARC_BUFC_DATA);
4926 return (abd_alloc(size, B_FALSE));
4927 }
4928 }
4929
4930 static void *
arc_get_data_buf(arc_buf_hdr_t * hdr,uint64_t size,void * tag)4931 arc_get_data_buf(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
4932 {
4933 arc_buf_contents_t type = arc_buf_type(hdr);
4934
4935 arc_get_data_impl(hdr, size, tag, B_TRUE);
4936 if (type == ARC_BUFC_METADATA) {
4937 return (zio_buf_alloc(size));
4938 } else {
4939 ASSERT(type == ARC_BUFC_DATA);
4940 return (zio_data_buf_alloc(size));
4941 }
4942 }
4943
4944 /*
4945 * Allocate a block and return it to the caller. If we are hitting the
4946 * hard limit for the cache size, we must sleep, waiting for the eviction
4947 * thread to catch up. If we're past the target size but below the hard
4948 * limit, we'll only signal the reclaim thread and continue on.
4949 */
4950 static void
arc_get_data_impl(arc_buf_hdr_t * hdr,uint64_t size,void * tag,boolean_t do_adapt)4951 arc_get_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag,
4952 boolean_t do_adapt)
4953 {
4954 arc_state_t *state = hdr->b_l1hdr.b_state;
4955 arc_buf_contents_t type = arc_buf_type(hdr);
4956
4957 if (do_adapt)
4958 arc_adapt(size, state);
4959
4960 /*
4961 * If arc_size is currently overflowing, and has grown past our
4962 * upper limit, we must be adding data faster than the evict
4963 * thread can evict. Thus, to ensure we don't compound the
4964 * problem by adding more data and forcing arc_size to grow even
4965 * further past its target size, we halt and wait for the
4966 * eviction thread to catch up.
4967 *
4968 * It's also possible that the reclaim thread is unable to evict
4969 * enough buffers to get arc_size below the overflow limit (e.g.
4970 * due to buffers being un-evictable, or hash lock collisions).
4971 * In this case, we want to proceed regardless if we're
4972 * overflowing; thus we don't use a while loop here.
4973 */
4974 if (arc_is_overflowing()) {
4975 mutex_enter(&arc_adjust_lock);
4976
4977 /*
4978 * Now that we've acquired the lock, we may no longer be
4979 * over the overflow limit, lets check.
4980 *
4981 * We're ignoring the case of spurious wake ups. If that
4982 * were to happen, it'd let this thread consume an ARC
4983 * buffer before it should have (i.e. before we're under
4984 * the overflow limit and were signalled by the reclaim
4985 * thread). As long as that is a rare occurrence, it
4986 * shouldn't cause any harm.
4987 */
4988 if (arc_is_overflowing()) {
4989 arc_adjust_needed = B_TRUE;
4990 zthr_wakeup(arc_adjust_zthr);
4991 (void) cv_wait(&arc_adjust_waiters_cv,
4992 &arc_adjust_lock);
4993 }
4994 mutex_exit(&arc_adjust_lock);
4995 }
4996
4997 VERIFY3U(hdr->b_type, ==, type);
4998 if (type == ARC_BUFC_METADATA) {
4999 arc_space_consume(size, ARC_SPACE_META);
5000 } else {
5001 arc_space_consume(size, ARC_SPACE_DATA);
5002 }
5003
5004 /*
5005 * Update the state size. Note that ghost states have a
5006 * "ghost size" and so don't need to be updated.
5007 */
5008 if (!GHOST_STATE(state)) {
5009
5010 (void) zfs_refcount_add_many(&state->arcs_size, size, tag);
5011
5012 /*
5013 * If this is reached via arc_read, the link is
5014 * protected by the hash lock. If reached via
5015 * arc_buf_alloc, the header should not be accessed by
5016 * any other thread. And, if reached via arc_read_done,
5017 * the hash lock will protect it if it's found in the
5018 * hash table; otherwise no other thread should be
5019 * trying to [add|remove]_reference it.
5020 */
5021 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5022 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5023 (void) zfs_refcount_add_many(&state->arcs_esize[type],
5024 size, tag);
5025 }
5026
5027 /*
5028 * If we are growing the cache, and we are adding anonymous
5029 * data, and we have outgrown arc_p, update arc_p
5030 */
5031 if (aggsum_compare(&arc_size, arc_c) < 0 &&
5032 hdr->b_l1hdr.b_state == arc_anon &&
5033 (zfs_refcount_count(&arc_anon->arcs_size) +
5034 zfs_refcount_count(&arc_mru->arcs_size) > arc_p))
5035 arc_p = MIN(arc_c, arc_p + size);
5036 }
5037 }
5038
5039 static void
arc_free_data_abd(arc_buf_hdr_t * hdr,abd_t * abd,uint64_t size,void * tag)5040 arc_free_data_abd(arc_buf_hdr_t *hdr, abd_t *abd, uint64_t size, void *tag)
5041 {
5042 arc_free_data_impl(hdr, size, tag);
5043 abd_free(abd);
5044 }
5045
5046 static void
arc_free_data_buf(arc_buf_hdr_t * hdr,void * buf,uint64_t size,void * tag)5047 arc_free_data_buf(arc_buf_hdr_t *hdr, void *buf, uint64_t size, void *tag)
5048 {
5049 arc_buf_contents_t type = arc_buf_type(hdr);
5050
5051 arc_free_data_impl(hdr, size, tag);
5052 if (type == ARC_BUFC_METADATA) {
5053 zio_buf_free(buf, size);
5054 } else {
5055 ASSERT(type == ARC_BUFC_DATA);
5056 zio_data_buf_free(buf, size);
5057 }
5058 }
5059
5060 /*
5061 * Free the arc data buffer.
5062 */
5063 static void
arc_free_data_impl(arc_buf_hdr_t * hdr,uint64_t size,void * tag)5064 arc_free_data_impl(arc_buf_hdr_t *hdr, uint64_t size, void *tag)
5065 {
5066 arc_state_t *state = hdr->b_l1hdr.b_state;
5067 arc_buf_contents_t type = arc_buf_type(hdr);
5068
5069 /* protected by hash lock, if in the hash table */
5070 if (multilist_link_active(&hdr->b_l1hdr.b_arc_node)) {
5071 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
5072 ASSERT(state != arc_anon && state != arc_l2c_only);
5073
5074 (void) zfs_refcount_remove_many(&state->arcs_esize[type],
5075 size, tag);
5076 }
5077 (void) zfs_refcount_remove_many(&state->arcs_size, size, tag);
5078
5079 VERIFY3U(hdr->b_type, ==, type);
5080 if (type == ARC_BUFC_METADATA) {
5081 arc_space_return(size, ARC_SPACE_META);
5082 } else {
5083 ASSERT(type == ARC_BUFC_DATA);
5084 arc_space_return(size, ARC_SPACE_DATA);
5085 }
5086 }
5087
5088 /*
5089 * This routine is called whenever a buffer is accessed.
5090 * NOTE: the hash lock is dropped in this function.
5091 */
5092 static void
arc_access(arc_buf_hdr_t * hdr,kmutex_t * hash_lock)5093 arc_access(arc_buf_hdr_t *hdr, kmutex_t *hash_lock)
5094 {
5095 clock_t now;
5096
5097 ASSERT(MUTEX_HELD(hash_lock));
5098 ASSERT(HDR_HAS_L1HDR(hdr));
5099
5100 if (hdr->b_l1hdr.b_state == arc_anon) {
5101 /*
5102 * This buffer is not in the cache, and does not
5103 * appear in our "ghost" list. Add the new buffer
5104 * to the MRU state.
5105 */
5106
5107 ASSERT0(hdr->b_l1hdr.b_arc_access);
5108 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5109 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5110 arc_change_state(arc_mru, hdr, hash_lock);
5111
5112 } else if (hdr->b_l1hdr.b_state == arc_mru) {
5113 now = ddi_get_lbolt();
5114
5115 /*
5116 * If this buffer is here because of a prefetch, then either:
5117 * - clear the flag if this is a "referencing" read
5118 * (any subsequent access will bump this into the MFU state).
5119 * or
5120 * - move the buffer to the head of the list if this is
5121 * another prefetch (to make it less likely to be evicted).
5122 */
5123 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5124 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 0) {
5125 /* link protected by hash lock */
5126 ASSERT(multilist_link_active(
5127 &hdr->b_l1hdr.b_arc_node));
5128 } else {
5129 if (HDR_HAS_L2HDR(hdr))
5130 l2arc_hdr_arcstats_decrement_state(hdr);
5131 arc_hdr_clear_flags(hdr,
5132 ARC_FLAG_PREFETCH |
5133 ARC_FLAG_PRESCIENT_PREFETCH);
5134 ARCSTAT_BUMP(arcstat_mru_hits);
5135 if (HDR_HAS_L2HDR(hdr))
5136 l2arc_hdr_arcstats_increment_state(hdr);
5137 }
5138 hdr->b_l1hdr.b_arc_access = now;
5139 return;
5140 }
5141
5142 /*
5143 * This buffer has been "accessed" only once so far,
5144 * but it is still in the cache. Move it to the MFU
5145 * state.
5146 */
5147 if (now > hdr->b_l1hdr.b_arc_access + ARC_MINTIME) {
5148 /*
5149 * More than 125ms have passed since we
5150 * instantiated this buffer. Move it to the
5151 * most frequently used state.
5152 */
5153 hdr->b_l1hdr.b_arc_access = now;
5154 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5155 arc_change_state(arc_mfu, hdr, hash_lock);
5156 }
5157 ARCSTAT_BUMP(arcstat_mru_hits);
5158 } else if (hdr->b_l1hdr.b_state == arc_mru_ghost) {
5159 arc_state_t *new_state;
5160 /*
5161 * This buffer has been "accessed" recently, but
5162 * was evicted from the cache. Move it to the
5163 * MFU state.
5164 */
5165 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5166 new_state = arc_mru;
5167 if (zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) > 0) {
5168 if (HDR_HAS_L2HDR(hdr))
5169 l2arc_hdr_arcstats_decrement_state(hdr);
5170 arc_hdr_clear_flags(hdr,
5171 ARC_FLAG_PREFETCH |
5172 ARC_FLAG_PRESCIENT_PREFETCH);
5173 if (HDR_HAS_L2HDR(hdr))
5174 l2arc_hdr_arcstats_increment_state(hdr);
5175 }
5176 DTRACE_PROBE1(new_state__mru, arc_buf_hdr_t *, hdr);
5177 } else {
5178 new_state = arc_mfu;
5179 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5180 }
5181
5182 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5183 arc_change_state(new_state, hdr, hash_lock);
5184
5185 ARCSTAT_BUMP(arcstat_mru_ghost_hits);
5186 } else if (hdr->b_l1hdr.b_state == arc_mfu) {
5187 /*
5188 * This buffer has been accessed more than once and is
5189 * still in the cache. Keep it in the MFU state.
5190 *
5191 * NOTE: an add_reference() that occurred when we did
5192 * the arc_read() will have kicked this off the list.
5193 * If it was a prefetch, we will explicitly move it to
5194 * the head of the list now.
5195 */
5196 ARCSTAT_BUMP(arcstat_mfu_hits);
5197 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5198 } else if (hdr->b_l1hdr.b_state == arc_mfu_ghost) {
5199 arc_state_t *new_state = arc_mfu;
5200 /*
5201 * This buffer has been accessed more than once but has
5202 * been evicted from the cache. Move it back to the
5203 * MFU state.
5204 */
5205
5206 if (HDR_PREFETCH(hdr) || HDR_PRESCIENT_PREFETCH(hdr)) {
5207 /*
5208 * This is a prefetch access...
5209 * move this block back to the MRU state.
5210 */
5211 new_state = arc_mru;
5212 }
5213
5214 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5215 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5216 arc_change_state(new_state, hdr, hash_lock);
5217
5218 ARCSTAT_BUMP(arcstat_mfu_ghost_hits);
5219 } else if (hdr->b_l1hdr.b_state == arc_l2c_only) {
5220 /*
5221 * This buffer is on the 2nd Level ARC.
5222 */
5223
5224 hdr->b_l1hdr.b_arc_access = ddi_get_lbolt();
5225 DTRACE_PROBE1(new_state__mfu, arc_buf_hdr_t *, hdr);
5226 arc_change_state(arc_mfu, hdr, hash_lock);
5227 } else {
5228 ASSERT(!"invalid arc state");
5229 }
5230 }
5231
5232 /*
5233 * This routine is called by dbuf_hold() to update the arc_access() state
5234 * which otherwise would be skipped for entries in the dbuf cache.
5235 */
5236 void
arc_buf_access(arc_buf_t * buf)5237 arc_buf_access(arc_buf_t *buf)
5238 {
5239 mutex_enter(&buf->b_evict_lock);
5240 arc_buf_hdr_t *hdr = buf->b_hdr;
5241
5242 /*
5243 * Avoid taking the hash_lock when possible as an optimization.
5244 * The header must be checked again under the hash_lock in order
5245 * to handle the case where it is concurrently being released.
5246 */
5247 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5248 mutex_exit(&buf->b_evict_lock);
5249 return;
5250 }
5251
5252 kmutex_t *hash_lock = HDR_LOCK(hdr);
5253 mutex_enter(hash_lock);
5254
5255 if (hdr->b_l1hdr.b_state == arc_anon || HDR_EMPTY(hdr)) {
5256 mutex_exit(hash_lock);
5257 mutex_exit(&buf->b_evict_lock);
5258 ARCSTAT_BUMP(arcstat_access_skip);
5259 return;
5260 }
5261
5262 mutex_exit(&buf->b_evict_lock);
5263
5264 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5265 hdr->b_l1hdr.b_state == arc_mfu);
5266
5267 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5268 arc_access(hdr, hash_lock);
5269 mutex_exit(hash_lock);
5270
5271 ARCSTAT_BUMP(arcstat_hits);
5272 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5273 demand, prefetch, !HDR_ISTYPE_METADATA(hdr), data, metadata, hits);
5274 }
5275
5276 /* a generic arc_read_done_func_t which you can use */
5277 /* ARGSUSED */
5278 void
arc_bcopy_func(zio_t * zio,const zbookmark_phys_t * zb,const blkptr_t * bp,arc_buf_t * buf,void * arg)5279 arc_bcopy_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5280 arc_buf_t *buf, void *arg)
5281 {
5282 if (buf == NULL)
5283 return;
5284
5285 bcopy(buf->b_data, arg, arc_buf_size(buf));
5286 arc_buf_destroy(buf, arg);
5287 }
5288
5289 /* a generic arc_read_done_func_t */
5290 void
arc_getbuf_func(zio_t * zio,const zbookmark_phys_t * zb,const blkptr_t * bp,arc_buf_t * buf,void * arg)5291 arc_getbuf_func(zio_t *zio, const zbookmark_phys_t *zb, const blkptr_t *bp,
5292 arc_buf_t *buf, void *arg)
5293 {
5294 arc_buf_t **bufp = arg;
5295
5296 if (buf == NULL) {
5297 ASSERT(zio == NULL || zio->io_error != 0);
5298 *bufp = NULL;
5299 } else {
5300 ASSERT(zio == NULL || zio->io_error == 0);
5301 *bufp = buf;
5302 ASSERT(buf->b_data != NULL);
5303 }
5304 }
5305
5306 static void
arc_hdr_verify(arc_buf_hdr_t * hdr,const blkptr_t * bp)5307 arc_hdr_verify(arc_buf_hdr_t *hdr, const blkptr_t *bp)
5308 {
5309 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
5310 ASSERT3U(HDR_GET_PSIZE(hdr), ==, 0);
5311 ASSERT3U(arc_hdr_get_compress(hdr), ==, ZIO_COMPRESS_OFF);
5312 } else {
5313 if (HDR_COMPRESSION_ENABLED(hdr)) {
5314 ASSERT3U(arc_hdr_get_compress(hdr), ==,
5315 BP_GET_COMPRESS(bp));
5316 }
5317 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
5318 ASSERT3U(HDR_GET_PSIZE(hdr), ==, BP_GET_PSIZE(bp));
5319 ASSERT3U(!!HDR_PROTECTED(hdr), ==, BP_IS_PROTECTED(bp));
5320 }
5321 }
5322
5323 /*
5324 * XXX this should be changed to return an error, and callers
5325 * re-read from disk on failure (on nondebug bits).
5326 */
5327 static void
arc_hdr_verify_checksum(spa_t * spa,arc_buf_hdr_t * hdr,const blkptr_t * bp)5328 arc_hdr_verify_checksum(spa_t *spa, arc_buf_hdr_t *hdr, const blkptr_t *bp)
5329 {
5330 arc_hdr_verify(hdr, bp);
5331 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp))
5332 return;
5333 int err = 0;
5334 abd_t *abd = NULL;
5335 if (BP_IS_ENCRYPTED(bp)) {
5336 if (HDR_HAS_RABD(hdr)) {
5337 abd = hdr->b_crypt_hdr.b_rabd;
5338 }
5339 } else if (HDR_COMPRESSION_ENABLED(hdr)) {
5340 abd = hdr->b_l1hdr.b_pabd;
5341 }
5342 if (abd != NULL) {
5343 /*
5344 * The offset is only used for labels, which are not
5345 * cached in the ARC, so it doesn't matter what we
5346 * pass for the offset parameter.
5347 */
5348 int psize = HDR_GET_PSIZE(hdr);
5349 err = zio_checksum_error_impl(spa, bp,
5350 BP_GET_CHECKSUM(bp), abd, psize, 0, NULL);
5351 if (err != 0) {
5352 /*
5353 * Use abd_copy_to_buf() rather than
5354 * abd_borrow_buf_copy() so that we are sure to
5355 * include the buf in crash dumps.
5356 */
5357 void *buf = kmem_alloc(psize, KM_SLEEP);
5358 abd_copy_to_buf(buf, abd, psize);
5359 panic("checksum of cached data doesn't match BP "
5360 "err=%u hdr=%p bp=%p abd=%p buf=%p",
5361 err, (void *)hdr, (void *)bp, (void *)abd, buf);
5362 }
5363 }
5364 }
5365
5366 static void
arc_read_done(zio_t * zio)5367 arc_read_done(zio_t *zio)
5368 {
5369 blkptr_t *bp = zio->io_bp;
5370 arc_buf_hdr_t *hdr = zio->io_private;
5371 kmutex_t *hash_lock = NULL;
5372 arc_callback_t *callback_list;
5373 arc_callback_t *acb;
5374 boolean_t freeable = B_FALSE;
5375
5376 /*
5377 * The hdr was inserted into hash-table and removed from lists
5378 * prior to starting I/O. We should find this header, since
5379 * it's in the hash table, and it should be legit since it's
5380 * not possible to evict it during the I/O. The only possible
5381 * reason for it not to be found is if we were freed during the
5382 * read.
5383 */
5384 if (HDR_IN_HASH_TABLE(hdr)) {
5385 ASSERT3U(hdr->b_birth, ==, BP_PHYSICAL_BIRTH(zio->io_bp));
5386 ASSERT3U(hdr->b_dva.dva_word[0], ==,
5387 BP_IDENTITY(zio->io_bp)->dva_word[0]);
5388 ASSERT3U(hdr->b_dva.dva_word[1], ==,
5389 BP_IDENTITY(zio->io_bp)->dva_word[1]);
5390
5391 arc_buf_hdr_t *found = buf_hash_find(hdr->b_spa, zio->io_bp,
5392 &hash_lock);
5393
5394 ASSERT((found == hdr &&
5395 DVA_EQUAL(&hdr->b_dva, BP_IDENTITY(zio->io_bp))) ||
5396 (found == hdr && HDR_L2_READING(hdr)));
5397 ASSERT3P(hash_lock, !=, NULL);
5398 }
5399
5400 if (BP_IS_PROTECTED(bp)) {
5401 hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
5402 hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
5403 zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
5404 hdr->b_crypt_hdr.b_iv);
5405
5406 if (BP_GET_TYPE(bp) == DMU_OT_INTENT_LOG) {
5407 void *tmpbuf;
5408
5409 tmpbuf = abd_borrow_buf_copy(zio->io_abd,
5410 sizeof (zil_chain_t));
5411 zio_crypt_decode_mac_zil(tmpbuf,
5412 hdr->b_crypt_hdr.b_mac);
5413 abd_return_buf(zio->io_abd, tmpbuf,
5414 sizeof (zil_chain_t));
5415 } else {
5416 zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
5417 }
5418 }
5419
5420 if (zio->io_error == 0) {
5421 /* byteswap if necessary */
5422 if (BP_SHOULD_BYTESWAP(zio->io_bp)) {
5423 if (BP_GET_LEVEL(zio->io_bp) > 0) {
5424 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
5425 } else {
5426 hdr->b_l1hdr.b_byteswap =
5427 DMU_OT_BYTESWAP(BP_GET_TYPE(zio->io_bp));
5428 }
5429 } else {
5430 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
5431 }
5432 }
5433
5434 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_EVICTED);
5435
5436 callback_list = hdr->b_l1hdr.b_acb;
5437 ASSERT3P(callback_list, !=, NULL);
5438
5439 if (hash_lock && zio->io_error == 0 &&
5440 hdr->b_l1hdr.b_state == arc_anon) {
5441 /*
5442 * Only call arc_access on anonymous buffers. This is because
5443 * if we've issued an I/O for an evicted buffer, we've already
5444 * called arc_access (to prevent any simultaneous readers from
5445 * getting confused).
5446 */
5447 arc_access(hdr, hash_lock);
5448 }
5449
5450 /*
5451 * If a read request has a callback (i.e. acb_done is not NULL), then we
5452 * make a buf containing the data according to the parameters which were
5453 * passed in. The implementation of arc_buf_alloc_impl() ensures that we
5454 * aren't needlessly decompressing the data multiple times.
5455 */
5456 int callback_cnt = 0;
5457 for (acb = callback_list; acb != NULL; acb = acb->acb_next) {
5458 if (!acb->acb_done)
5459 continue;
5460
5461 callback_cnt++;
5462
5463 if (zio->io_error != 0)
5464 continue;
5465
5466 int error = arc_buf_alloc_impl(hdr, zio->io_spa,
5467 &acb->acb_zb, acb->acb_private, acb->acb_encrypted,
5468 acb->acb_compressed, acb->acb_noauth, B_TRUE,
5469 &acb->acb_buf);
5470
5471 /*
5472 * Assert non-speculative zios didn't fail because an
5473 * encryption key wasn't loaded
5474 */
5475 ASSERT((zio->io_flags & ZIO_FLAG_SPECULATIVE) ||
5476 error != EACCES);
5477
5478 /*
5479 * If we failed to decrypt, report an error now (as the zio
5480 * layer would have done if it had done the transforms).
5481 */
5482 if (error == ECKSUM) {
5483 ASSERT(BP_IS_PROTECTED(bp));
5484 error = SET_ERROR(EIO);
5485 if ((zio->io_flags & ZIO_FLAG_SPECULATIVE) == 0) {
5486 spa_log_error(zio->io_spa, &acb->acb_zb);
5487 (void) zfs_ereport_post(
5488 FM_EREPORT_ZFS_AUTHENTICATION,
5489 zio->io_spa, NULL, &acb->acb_zb, zio, 0, 0);
5490 }
5491 }
5492
5493 if (error != 0) {
5494 /*
5495 * Decompression failed. Set io_error
5496 * so that when we call acb_done (below),
5497 * we will indicate that the read failed.
5498 * Note that in the unusual case where one
5499 * callback is compressed and another
5500 * uncompressed, we will mark all of them
5501 * as failed, even though the uncompressed
5502 * one can't actually fail. In this case,
5503 * the hdr will not be anonymous, because
5504 * if there are multiple callbacks, it's
5505 * because multiple threads found the same
5506 * arc buf in the hash table.
5507 */
5508 zio->io_error = error;
5509 }
5510 }
5511
5512 /*
5513 * If there are multiple callbacks, we must have the hash lock,
5514 * because the only way for multiple threads to find this hdr is
5515 * in the hash table. This ensures that if there are multiple
5516 * callbacks, the hdr is not anonymous. If it were anonymous,
5517 * we couldn't use arc_buf_destroy() in the error case below.
5518 */
5519 ASSERT(callback_cnt < 2 || hash_lock != NULL);
5520
5521 hdr->b_l1hdr.b_acb = NULL;
5522 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5523 if (callback_cnt == 0)
5524 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
5525
5526 ASSERT(zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt) ||
5527 callback_list != NULL);
5528
5529 if (zio->io_error == 0) {
5530 arc_hdr_verify(hdr, zio->io_bp);
5531 } else {
5532 arc_hdr_set_flags(hdr, ARC_FLAG_IO_ERROR);
5533 if (hdr->b_l1hdr.b_state != arc_anon)
5534 arc_change_state(arc_anon, hdr, hash_lock);
5535 if (HDR_IN_HASH_TABLE(hdr))
5536 buf_hash_remove(hdr);
5537 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5538 }
5539
5540 /*
5541 * Broadcast before we drop the hash_lock to avoid the possibility
5542 * that the hdr (and hence the cv) might be freed before we get to
5543 * the cv_broadcast().
5544 */
5545 cv_broadcast(&hdr->b_l1hdr.b_cv);
5546
5547 if (hash_lock != NULL) {
5548 mutex_exit(hash_lock);
5549 } else {
5550 /*
5551 * This block was freed while we waited for the read to
5552 * complete. It has been removed from the hash table and
5553 * moved to the anonymous state (so that it won't show up
5554 * in the cache).
5555 */
5556 ASSERT3P(hdr->b_l1hdr.b_state, ==, arc_anon);
5557 freeable = zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt);
5558 }
5559
5560 /* execute each callback and free its structure */
5561 while ((acb = callback_list) != NULL) {
5562
5563 if (acb->acb_done != NULL) {
5564 if (zio->io_error != 0 && acb->acb_buf != NULL) {
5565 /*
5566 * If arc_buf_alloc_impl() fails during
5567 * decompression, the buf will still be
5568 * allocated, and needs to be freed here.
5569 */
5570 arc_buf_destroy(acb->acb_buf, acb->acb_private);
5571 acb->acb_buf = NULL;
5572 }
5573 acb->acb_done(zio, &zio->io_bookmark, zio->io_bp,
5574 acb->acb_buf, acb->acb_private);
5575 }
5576
5577 if (acb->acb_zio_dummy != NULL) {
5578 acb->acb_zio_dummy->io_error = zio->io_error;
5579 zio_nowait(acb->acb_zio_dummy);
5580 }
5581
5582 callback_list = acb->acb_next;
5583 kmem_free(acb, sizeof (arc_callback_t));
5584 }
5585
5586 if (freeable)
5587 arc_hdr_destroy(hdr);
5588 }
5589
5590 /*
5591 * "Read" the block at the specified DVA (in bp) via the
5592 * cache. If the block is found in the cache, invoke the provided
5593 * callback immediately and return. Note that the `zio' parameter
5594 * in the callback will be NULL in this case, since no IO was
5595 * required. If the block is not in the cache pass the read request
5596 * on to the spa with a substitute callback function, so that the
5597 * requested block will be added to the cache.
5598 *
5599 * If a read request arrives for a block that has a read in-progress,
5600 * either wait for the in-progress read to complete (and return the
5601 * results); or, if this is a read with a "done" func, add a record
5602 * to the read to invoke the "done" func when the read completes,
5603 * and return; or just return.
5604 *
5605 * arc_read_done() will invoke all the requested "done" functions
5606 * for readers of this block.
5607 */
5608 int
arc_read(zio_t * pio,spa_t * spa,const blkptr_t * bp,arc_read_done_func_t * done,void * private,zio_priority_t priority,int zio_flags,arc_flags_t * arc_flags,const zbookmark_phys_t * zb)5609 arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp, arc_read_done_func_t *done,
5610 void *private, zio_priority_t priority, int zio_flags,
5611 arc_flags_t *arc_flags, const zbookmark_phys_t *zb)
5612 {
5613 arc_buf_hdr_t *hdr = NULL;
5614 kmutex_t *hash_lock = NULL;
5615 zio_t *rzio;
5616 uint64_t guid = spa_load_guid(spa);
5617 boolean_t compressed_read = (zio_flags & ZIO_FLAG_RAW_COMPRESS) != 0;
5618 boolean_t encrypted_read = BP_IS_ENCRYPTED(bp) &&
5619 (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
5620 boolean_t noauth_read = BP_IS_AUTHENTICATED(bp) &&
5621 (zio_flags & ZIO_FLAG_RAW_ENCRYPT) != 0;
5622 int rc = 0;
5623
5624 ASSERT(!BP_IS_EMBEDDED(bp) ||
5625 BPE_GET_ETYPE(bp) == BP_EMBEDDED_TYPE_DATA);
5626
5627 top:
5628 if (!BP_IS_EMBEDDED(bp)) {
5629 /*
5630 * Embedded BP's have no DVA and require no I/O to "read".
5631 * Create an anonymous arc buf to back it.
5632 */
5633 hdr = buf_hash_find(guid, bp, &hash_lock);
5634 }
5635
5636 /*
5637 * Determine if we have an L1 cache hit or a cache miss. For simplicity
5638 * we maintain encrypted data seperately from compressed / uncompressed
5639 * data. If the user is requesting raw encrypted data and we don't have
5640 * that in the header we will read from disk to guarantee that we can
5641 * get it even if the encryption keys aren't loaded.
5642 */
5643 if (hdr != NULL && HDR_HAS_L1HDR(hdr) && (HDR_HAS_RABD(hdr) ||
5644 (hdr->b_l1hdr.b_pabd != NULL && !encrypted_read))) {
5645 arc_buf_t *buf = NULL;
5646 *arc_flags |= ARC_FLAG_CACHED;
5647
5648 if (HDR_IO_IN_PROGRESS(hdr)) {
5649 zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head;
5650
5651 ASSERT3P(head_zio, !=, NULL);
5652 if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
5653 priority == ZIO_PRIORITY_SYNC_READ) {
5654 /*
5655 * This is a sync read that needs to wait for
5656 * an in-flight async read. Request that the
5657 * zio have its priority upgraded.
5658 */
5659 zio_change_priority(head_zio, priority);
5660 DTRACE_PROBE1(arc__async__upgrade__sync,
5661 arc_buf_hdr_t *, hdr);
5662 ARCSTAT_BUMP(arcstat_async_upgrade_sync);
5663 }
5664 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5665 arc_hdr_clear_flags(hdr,
5666 ARC_FLAG_PREDICTIVE_PREFETCH);
5667 }
5668
5669 if (*arc_flags & ARC_FLAG_WAIT) {
5670 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5671 mutex_exit(hash_lock);
5672 goto top;
5673 }
5674 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
5675
5676 if (done) {
5677 arc_callback_t *acb = NULL;
5678
5679 acb = kmem_zalloc(sizeof (arc_callback_t),
5680 KM_SLEEP);
5681 acb->acb_done = done;
5682 acb->acb_private = private;
5683 acb->acb_compressed = compressed_read;
5684 acb->acb_encrypted = encrypted_read;
5685 acb->acb_noauth = noauth_read;
5686 acb->acb_zb = *zb;
5687 if (pio != NULL)
5688 acb->acb_zio_dummy = zio_null(pio,
5689 spa, NULL, NULL, NULL, zio_flags);
5690
5691 ASSERT3P(acb->acb_done, !=, NULL);
5692 acb->acb_zio_head = head_zio;
5693 acb->acb_next = hdr->b_l1hdr.b_acb;
5694 hdr->b_l1hdr.b_acb = acb;
5695 mutex_exit(hash_lock);
5696 return (0);
5697 }
5698 mutex_exit(hash_lock);
5699 return (0);
5700 }
5701
5702 ASSERT(hdr->b_l1hdr.b_state == arc_mru ||
5703 hdr->b_l1hdr.b_state == arc_mfu);
5704
5705 if (done) {
5706 if (hdr->b_flags & ARC_FLAG_PREDICTIVE_PREFETCH) {
5707 /*
5708 * This is a demand read which does not have to
5709 * wait for i/o because we did a predictive
5710 * prefetch i/o for it, which has completed.
5711 */
5712 DTRACE_PROBE1(
5713 arc__demand__hit__predictive__prefetch,
5714 arc_buf_hdr_t *, hdr);
5715 ARCSTAT_BUMP(
5716 arcstat_demand_hit_predictive_prefetch);
5717 arc_hdr_clear_flags(hdr,
5718 ARC_FLAG_PREDICTIVE_PREFETCH);
5719 }
5720
5721 if (hdr->b_flags & ARC_FLAG_PRESCIENT_PREFETCH) {
5722 ARCSTAT_BUMP(
5723 arcstat_demand_hit_prescient_prefetch);
5724 arc_hdr_clear_flags(hdr,
5725 ARC_FLAG_PRESCIENT_PREFETCH);
5726 }
5727
5728 ASSERT(!BP_IS_EMBEDDED(bp) || !BP_IS_HOLE(bp));
5729
5730 arc_hdr_verify_checksum(spa, hdr, bp);
5731
5732 /* Get a buf with the desired data in it. */
5733 rc = arc_buf_alloc_impl(hdr, spa, zb, private,
5734 encrypted_read, compressed_read, noauth_read,
5735 B_TRUE, &buf);
5736 if (rc == ECKSUM) {
5737 /*
5738 * Convert authentication and decryption errors
5739 * to EIO (and generate an ereport if needed)
5740 * before leaving the ARC.
5741 */
5742 rc = SET_ERROR(EIO);
5743 if ((zio_flags & ZIO_FLAG_SPECULATIVE) == 0) {
5744 spa_log_error(spa, zb);
5745 (void) zfs_ereport_post(
5746 FM_EREPORT_ZFS_AUTHENTICATION,
5747 spa, NULL, zb, NULL, 0, 0);
5748 }
5749 }
5750 if (rc != 0) {
5751 (void) remove_reference(hdr, hash_lock,
5752 private);
5753 arc_buf_destroy_impl(buf);
5754 buf = NULL;
5755 }
5756 /* assert any errors weren't due to unloaded keys */
5757 ASSERT((zio_flags & ZIO_FLAG_SPECULATIVE) ||
5758 rc != EACCES);
5759 } else if (*arc_flags & ARC_FLAG_PREFETCH &&
5760 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5761 if (HDR_HAS_L2HDR(hdr))
5762 l2arc_hdr_arcstats_decrement_state(hdr);
5763 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5764 if (HDR_HAS_L2HDR(hdr))
5765 l2arc_hdr_arcstats_increment_state(hdr);
5766 }
5767 DTRACE_PROBE1(arc__hit, arc_buf_hdr_t *, hdr);
5768 arc_access(hdr, hash_lock);
5769 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
5770 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
5771 if (*arc_flags & ARC_FLAG_L2CACHE)
5772 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5773 mutex_exit(hash_lock);
5774 ARCSTAT_BUMP(arcstat_hits);
5775 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5776 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5777 data, metadata, hits);
5778
5779 if (done)
5780 done(NULL, zb, bp, buf, private);
5781 } else {
5782 uint64_t lsize = BP_GET_LSIZE(bp);
5783 uint64_t psize = BP_GET_PSIZE(bp);
5784 arc_callback_t *acb;
5785 vdev_t *vd = NULL;
5786 uint64_t addr = 0;
5787 boolean_t devw = B_FALSE;
5788 uint64_t size;
5789 abd_t *hdr_abd;
5790 int alloc_flags = encrypted_read ? ARC_HDR_ALLOC_RDATA : 0;
5791
5792 if (hdr == NULL) {
5793 /* this block is not in the cache */
5794 arc_buf_hdr_t *exists = NULL;
5795 arc_buf_contents_t type = BP_GET_BUFC_TYPE(bp);
5796 hdr = arc_hdr_alloc(spa_load_guid(spa), psize, lsize,
5797 BP_IS_PROTECTED(bp), BP_GET_COMPRESS(bp), type,
5798 encrypted_read);
5799
5800 if (!BP_IS_EMBEDDED(bp)) {
5801 hdr->b_dva = *BP_IDENTITY(bp);
5802 hdr->b_birth = BP_PHYSICAL_BIRTH(bp);
5803 exists = buf_hash_insert(hdr, &hash_lock);
5804 }
5805 if (exists != NULL) {
5806 /* somebody beat us to the hash insert */
5807 mutex_exit(hash_lock);
5808 buf_discard_identity(hdr);
5809 arc_hdr_destroy(hdr);
5810 goto top; /* restart the IO request */
5811 }
5812 } else {
5813 /*
5814 * This block is in the ghost cache or encrypted data
5815 * was requested and we didn't have it. If it was
5816 * L2-only (and thus didn't have an L1 hdr),
5817 * we realloc the header to add an L1 hdr.
5818 */
5819 if (!HDR_HAS_L1HDR(hdr)) {
5820 hdr = arc_hdr_realloc(hdr, hdr_l2only_cache,
5821 hdr_full_cache);
5822 }
5823
5824 if (GHOST_STATE(hdr->b_l1hdr.b_state)) {
5825 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
5826 ASSERT(!HDR_HAS_RABD(hdr));
5827 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
5828 ASSERT0(zfs_refcount_count(
5829 &hdr->b_l1hdr.b_refcnt));
5830 ASSERT3P(hdr->b_l1hdr.b_buf, ==, NULL);
5831 ASSERT3P(hdr->b_l1hdr.b_freeze_cksum, ==, NULL);
5832 } else if (HDR_IO_IN_PROGRESS(hdr)) {
5833 /*
5834 * If this header already had an IO in progress
5835 * and we are performing another IO to fetch
5836 * encrypted data we must wait until the first
5837 * IO completes so as not to confuse
5838 * arc_read_done(). This should be very rare
5839 * and so the performance impact shouldn't
5840 * matter.
5841 */
5842 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
5843 mutex_exit(hash_lock);
5844 goto top;
5845 }
5846
5847 /*
5848 * This is a delicate dance that we play here.
5849 * This hdr might be in the ghost list so we access
5850 * it to move it out of the ghost list before we
5851 * initiate the read. If it's a prefetch then
5852 * it won't have a callback so we'll remove the
5853 * reference that arc_buf_alloc_impl() created. We
5854 * do this after we've called arc_access() to
5855 * avoid hitting an assert in remove_reference().
5856 */
5857 arc_adapt(arc_hdr_size(hdr), hdr->b_l1hdr.b_state);
5858 arc_access(hdr, hash_lock);
5859 arc_hdr_alloc_pabd(hdr, alloc_flags);
5860 }
5861
5862 if (encrypted_read) {
5863 ASSERT(HDR_HAS_RABD(hdr));
5864 size = HDR_GET_PSIZE(hdr);
5865 hdr_abd = hdr->b_crypt_hdr.b_rabd;
5866 zio_flags |= ZIO_FLAG_RAW;
5867 } else {
5868 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
5869 size = arc_hdr_size(hdr);
5870 hdr_abd = hdr->b_l1hdr.b_pabd;
5871
5872 if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF) {
5873 zio_flags |= ZIO_FLAG_RAW_COMPRESS;
5874 }
5875
5876 /*
5877 * For authenticated bp's, we do not ask the ZIO layer
5878 * to authenticate them since this will cause the entire
5879 * IO to fail if the key isn't loaded. Instead, we
5880 * defer authentication until arc_buf_fill(), which will
5881 * verify the data when the key is available.
5882 */
5883 if (BP_IS_AUTHENTICATED(bp))
5884 zio_flags |= ZIO_FLAG_RAW_ENCRYPT;
5885 }
5886
5887 if (*arc_flags & ARC_FLAG_PREFETCH &&
5888 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
5889 if (HDR_HAS_L2HDR(hdr))
5890 l2arc_hdr_arcstats_decrement_state(hdr);
5891 arc_hdr_set_flags(hdr, ARC_FLAG_PREFETCH);
5892 if (HDR_HAS_L2HDR(hdr))
5893 l2arc_hdr_arcstats_increment_state(hdr);
5894 }
5895 if (*arc_flags & ARC_FLAG_PRESCIENT_PREFETCH)
5896 arc_hdr_set_flags(hdr, ARC_FLAG_PRESCIENT_PREFETCH);
5897
5898 if (*arc_flags & ARC_FLAG_L2CACHE)
5899 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
5900 if (BP_IS_AUTHENTICATED(bp))
5901 arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
5902 if (BP_GET_LEVEL(bp) > 0)
5903 arc_hdr_set_flags(hdr, ARC_FLAG_INDIRECT);
5904 if (*arc_flags & ARC_FLAG_PREDICTIVE_PREFETCH)
5905 arc_hdr_set_flags(hdr, ARC_FLAG_PREDICTIVE_PREFETCH);
5906 ASSERT(!GHOST_STATE(hdr->b_l1hdr.b_state));
5907
5908 acb = kmem_zalloc(sizeof (arc_callback_t), KM_SLEEP);
5909 acb->acb_done = done;
5910 acb->acb_private = private;
5911 acb->acb_compressed = compressed_read;
5912 acb->acb_encrypted = encrypted_read;
5913 acb->acb_noauth = noauth_read;
5914 acb->acb_zb = *zb;
5915
5916 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
5917 hdr->b_l1hdr.b_acb = acb;
5918 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
5919
5920 if (HDR_HAS_L2HDR(hdr) &&
5921 (vd = hdr->b_l2hdr.b_dev->l2ad_vdev) != NULL) {
5922 devw = hdr->b_l2hdr.b_dev->l2ad_writing;
5923 addr = hdr->b_l2hdr.b_daddr;
5924 /*
5925 * Lock out L2ARC device removal.
5926 */
5927 if (vdev_is_dead(vd) ||
5928 !spa_config_tryenter(spa, SCL_L2ARC, vd, RW_READER))
5929 vd = NULL;
5930 }
5931
5932 /*
5933 * We count both async reads and scrub IOs as asynchronous so
5934 * that both can be upgraded in the event of a cache hit while
5935 * the read IO is still in-flight.
5936 */
5937 if (priority == ZIO_PRIORITY_ASYNC_READ ||
5938 priority == ZIO_PRIORITY_SCRUB)
5939 arc_hdr_set_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5940 else
5941 arc_hdr_clear_flags(hdr, ARC_FLAG_PRIO_ASYNC_READ);
5942
5943 /*
5944 * At this point, we have a level 1 cache miss. Try again in
5945 * L2ARC if possible.
5946 */
5947 ASSERT3U(HDR_GET_LSIZE(hdr), ==, lsize);
5948
5949 DTRACE_PROBE4(arc__miss, arc_buf_hdr_t *, hdr, blkptr_t *, bp,
5950 uint64_t, lsize, zbookmark_phys_t *, zb);
5951 ARCSTAT_BUMP(arcstat_misses);
5952 ARCSTAT_CONDSTAT(!HDR_PREFETCH(hdr),
5953 demand, prefetch, !HDR_ISTYPE_METADATA(hdr),
5954 data, metadata, misses);
5955
5956 if (vd != NULL && l2arc_ndev != 0 && !(l2arc_norw && devw)) {
5957 /*
5958 * Read from the L2ARC if the following are true:
5959 * 1. The L2ARC vdev was previously cached.
5960 * 2. This buffer still has L2ARC metadata.
5961 * 3. This buffer isn't currently writing to the L2ARC.
5962 * 4. The L2ARC entry wasn't evicted, which may
5963 * also have invalidated the vdev.
5964 * 5. This isn't prefetch or l2arc_noprefetch is 0.
5965 */
5966 if (HDR_HAS_L2HDR(hdr) &&
5967 !HDR_L2_WRITING(hdr) && !HDR_L2_EVICTED(hdr) &&
5968 !(l2arc_noprefetch && HDR_PREFETCH(hdr))) {
5969 l2arc_read_callback_t *cb;
5970 abd_t *abd;
5971 uint64_t asize;
5972
5973 DTRACE_PROBE1(l2arc__hit, arc_buf_hdr_t *, hdr);
5974 ARCSTAT_BUMP(arcstat_l2_hits);
5975
5976 cb = kmem_zalloc(sizeof (l2arc_read_callback_t),
5977 KM_SLEEP);
5978 cb->l2rcb_hdr = hdr;
5979 cb->l2rcb_bp = *bp;
5980 cb->l2rcb_zb = *zb;
5981 cb->l2rcb_flags = zio_flags;
5982
5983 /*
5984 * When Compressed ARC is disabled, but the
5985 * L2ARC block is compressed, arc_hdr_size()
5986 * will have returned LSIZE rather than PSIZE.
5987 */
5988 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
5989 !HDR_COMPRESSION_ENABLED(hdr) &&
5990 HDR_GET_PSIZE(hdr) != 0) {
5991 size = HDR_GET_PSIZE(hdr);
5992 }
5993
5994 asize = vdev_psize_to_asize(vd, size);
5995 if (asize != size) {
5996 abd = abd_alloc_for_io(asize,
5997 HDR_ISTYPE_METADATA(hdr));
5998 cb->l2rcb_abd = abd;
5999 } else {
6000 abd = hdr_abd;
6001 }
6002
6003 ASSERT(addr >= VDEV_LABEL_START_SIZE &&
6004 addr + asize <= vd->vdev_psize -
6005 VDEV_LABEL_END_SIZE);
6006
6007 /*
6008 * l2arc read. The SCL_L2ARC lock will be
6009 * released by l2arc_read_done().
6010 * Issue a null zio if the underlying buffer
6011 * was squashed to zero size by compression.
6012 */
6013 ASSERT3U(arc_hdr_get_compress(hdr), !=,
6014 ZIO_COMPRESS_EMPTY);
6015 rzio = zio_read_phys(pio, vd, addr,
6016 asize, abd,
6017 ZIO_CHECKSUM_OFF,
6018 l2arc_read_done, cb, priority,
6019 zio_flags | ZIO_FLAG_DONT_CACHE |
6020 ZIO_FLAG_CANFAIL |
6021 ZIO_FLAG_DONT_PROPAGATE |
6022 ZIO_FLAG_DONT_RETRY, B_FALSE);
6023 acb->acb_zio_head = rzio;
6024
6025 if (hash_lock != NULL)
6026 mutex_exit(hash_lock);
6027
6028 DTRACE_PROBE2(l2arc__read, vdev_t *, vd,
6029 zio_t *, rzio);
6030 ARCSTAT_INCR(arcstat_l2_read_bytes,
6031 HDR_GET_PSIZE(hdr));
6032
6033 if (*arc_flags & ARC_FLAG_NOWAIT) {
6034 zio_nowait(rzio);
6035 return (0);
6036 }
6037
6038 ASSERT(*arc_flags & ARC_FLAG_WAIT);
6039 if (zio_wait(rzio) == 0)
6040 return (0);
6041
6042 /* l2arc read error; goto zio_read() */
6043 if (hash_lock != NULL)
6044 mutex_enter(hash_lock);
6045 } else {
6046 DTRACE_PROBE1(l2arc__miss,
6047 arc_buf_hdr_t *, hdr);
6048 ARCSTAT_BUMP(arcstat_l2_misses);
6049 if (HDR_L2_WRITING(hdr))
6050 ARCSTAT_BUMP(arcstat_l2_rw_clash);
6051 spa_config_exit(spa, SCL_L2ARC, vd);
6052 }
6053 } else {
6054 if (vd != NULL)
6055 spa_config_exit(spa, SCL_L2ARC, vd);
6056 if (l2arc_ndev != 0) {
6057 DTRACE_PROBE1(l2arc__miss,
6058 arc_buf_hdr_t *, hdr);
6059 ARCSTAT_BUMP(arcstat_l2_misses);
6060 }
6061 }
6062
6063 rzio = zio_read(pio, spa, bp, hdr_abd, size,
6064 arc_read_done, hdr, priority, zio_flags, zb);
6065 acb->acb_zio_head = rzio;
6066
6067 if (hash_lock != NULL)
6068 mutex_exit(hash_lock);
6069
6070 if (*arc_flags & ARC_FLAG_WAIT)
6071 return (zio_wait(rzio));
6072
6073 ASSERT(*arc_flags & ARC_FLAG_NOWAIT);
6074 zio_nowait(rzio);
6075 }
6076 return (rc);
6077 }
6078
6079 /*
6080 * Notify the arc that a block was freed, and thus will never be used again.
6081 */
6082 void
arc_freed(spa_t * spa,const blkptr_t * bp)6083 arc_freed(spa_t *spa, const blkptr_t *bp)
6084 {
6085 arc_buf_hdr_t *hdr;
6086 kmutex_t *hash_lock;
6087 uint64_t guid = spa_load_guid(spa);
6088
6089 ASSERT(!BP_IS_EMBEDDED(bp));
6090
6091 hdr = buf_hash_find(guid, bp, &hash_lock);
6092 if (hdr == NULL)
6093 return;
6094
6095 /*
6096 * We might be trying to free a block that is still doing I/O
6097 * (i.e. prefetch) or has a reference (i.e. a dedup-ed,
6098 * dmu_sync-ed block). If this block is being prefetched, then it
6099 * would still have the ARC_FLAG_IO_IN_PROGRESS flag set on the hdr
6100 * until the I/O completes. A block may also have a reference if it is
6101 * part of a dedup-ed, dmu_synced write. The dmu_sync() function would
6102 * have written the new block to its final resting place on disk but
6103 * without the dedup flag set. This would have left the hdr in the MRU
6104 * state and discoverable. When the txg finally syncs it detects that
6105 * the block was overridden in open context and issues an override I/O.
6106 * Since this is a dedup block, the override I/O will determine if the
6107 * block is already in the DDT. If so, then it will replace the io_bp
6108 * with the bp from the DDT and allow the I/O to finish. When the I/O
6109 * reaches the done callback, dbuf_write_override_done, it will
6110 * check to see if the io_bp and io_bp_override are identical.
6111 * If they are not, then it indicates that the bp was replaced with
6112 * the bp in the DDT and the override bp is freed. This allows
6113 * us to arrive here with a reference on a block that is being
6114 * freed. So if we have an I/O in progress, or a reference to
6115 * this hdr, then we don't destroy the hdr.
6116 */
6117 if (!HDR_HAS_L1HDR(hdr) || (!HDR_IO_IN_PROGRESS(hdr) &&
6118 zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt))) {
6119 arc_change_state(arc_anon, hdr, hash_lock);
6120 arc_hdr_destroy(hdr);
6121 mutex_exit(hash_lock);
6122 } else {
6123 mutex_exit(hash_lock);
6124 }
6125
6126 }
6127
6128 /*
6129 * Release this buffer from the cache, making it an anonymous buffer. This
6130 * must be done after a read and prior to modifying the buffer contents.
6131 * If the buffer has more than one reference, we must make
6132 * a new hdr for the buffer.
6133 */
6134 void
arc_release(arc_buf_t * buf,void * tag)6135 arc_release(arc_buf_t *buf, void *tag)
6136 {
6137 /*
6138 * It would be nice to assert that if its DMU metadata (level >
6139 * 0 || it's the dnode file), then it must be syncing context.
6140 * But we don't know that information at this level.
6141 */
6142
6143 mutex_enter(&buf->b_evict_lock);
6144
6145 arc_buf_hdr_t *hdr = buf->b_hdr;
6146
6147 ASSERT(HDR_HAS_L1HDR(hdr));
6148
6149 /*
6150 * We don't grab the hash lock prior to this check, because if
6151 * the buffer's header is in the arc_anon state, it won't be
6152 * linked into the hash table.
6153 */
6154 if (hdr->b_l1hdr.b_state == arc_anon) {
6155 mutex_exit(&buf->b_evict_lock);
6156 /*
6157 * If we are called from dmu_convert_mdn_block_to_raw(),
6158 * a write might be in progress. This is OK because
6159 * the caller won't change the content of this buffer,
6160 * only the flags (via arc_convert_to_raw()).
6161 */
6162 /* ASSERT(!HDR_IO_IN_PROGRESS(hdr)); */
6163 ASSERT(!HDR_IN_HASH_TABLE(hdr));
6164 ASSERT(!HDR_HAS_L2HDR(hdr));
6165 ASSERT(HDR_EMPTY(hdr));
6166
6167 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6168 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), ==, 1);
6169 ASSERT(!list_link_active(&hdr->b_l1hdr.b_arc_node));
6170
6171 hdr->b_l1hdr.b_arc_access = 0;
6172
6173 /*
6174 * If the buf is being overridden then it may already
6175 * have a hdr that is not empty.
6176 */
6177 buf_discard_identity(hdr);
6178 arc_buf_thaw(buf);
6179
6180 return;
6181 }
6182
6183 kmutex_t *hash_lock = HDR_LOCK(hdr);
6184 mutex_enter(hash_lock);
6185
6186 /*
6187 * Wait for any other IO for this hdr, as additional
6188 * buf(s) could be about to appear, in which case
6189 * we would not want to transition hdr to arc_anon.
6190 */
6191 while (HDR_IO_IN_PROGRESS(hdr)) {
6192 DTRACE_PROBE1(arc_release__io, arc_buf_hdr_t *, hdr);
6193 cv_wait(&hdr->b_l1hdr.b_cv, hash_lock);
6194 }
6195
6196 /*
6197 * This assignment is only valid as long as the hash_lock is
6198 * held, we must be careful not to reference state or the
6199 * b_state field after dropping the lock.
6200 */
6201 arc_state_t *state = hdr->b_l1hdr.b_state;
6202 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
6203 ASSERT3P(state, !=, arc_anon);
6204
6205 /* this buffer is not on any list */
6206 ASSERT3S(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt), >, 0);
6207
6208 if (HDR_HAS_L2HDR(hdr)) {
6209 mutex_enter(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6210
6211 /*
6212 * We have to recheck this conditional again now that
6213 * we're holding the l2ad_mtx to prevent a race with
6214 * another thread which might be concurrently calling
6215 * l2arc_evict(). In that case, l2arc_evict() might have
6216 * destroyed the header's L2 portion as we were waiting
6217 * to acquire the l2ad_mtx.
6218 */
6219 if (HDR_HAS_L2HDR(hdr))
6220 arc_hdr_l2hdr_destroy(hdr);
6221
6222 mutex_exit(&hdr->b_l2hdr.b_dev->l2ad_mtx);
6223 }
6224
6225 /*
6226 * Do we have more than one buf?
6227 */
6228 if (hdr->b_l1hdr.b_bufcnt > 1) {
6229 arc_buf_hdr_t *nhdr;
6230 uint64_t spa = hdr->b_spa;
6231 uint64_t psize = HDR_GET_PSIZE(hdr);
6232 uint64_t lsize = HDR_GET_LSIZE(hdr);
6233 boolean_t protected = HDR_PROTECTED(hdr);
6234 enum zio_compress compress = arc_hdr_get_compress(hdr);
6235 arc_buf_contents_t type = arc_buf_type(hdr);
6236 VERIFY3U(hdr->b_type, ==, type);
6237
6238 ASSERT(hdr->b_l1hdr.b_buf != buf || buf->b_next != NULL);
6239 (void) remove_reference(hdr, hash_lock, tag);
6240
6241 if (arc_buf_is_shared(buf) && !ARC_BUF_COMPRESSED(buf)) {
6242 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6243 ASSERT(ARC_BUF_LAST(buf));
6244 }
6245
6246 /*
6247 * Pull the data off of this hdr and attach it to
6248 * a new anonymous hdr. Also find the last buffer
6249 * in the hdr's buffer list.
6250 */
6251 arc_buf_t *lastbuf = arc_buf_remove(hdr, buf);
6252 ASSERT3P(lastbuf, !=, NULL);
6253
6254 /*
6255 * If the current arc_buf_t and the hdr are sharing their data
6256 * buffer, then we must stop sharing that block.
6257 */
6258 if (arc_buf_is_shared(buf)) {
6259 ASSERT3P(hdr->b_l1hdr.b_buf, !=, buf);
6260 VERIFY(!arc_buf_is_shared(lastbuf));
6261
6262 /*
6263 * First, sever the block sharing relationship between
6264 * buf and the arc_buf_hdr_t.
6265 */
6266 arc_unshare_buf(hdr, buf);
6267
6268 /*
6269 * Now we need to recreate the hdr's b_pabd. Since we
6270 * have lastbuf handy, we try to share with it, but if
6271 * we can't then we allocate a new b_pabd and copy the
6272 * data from buf into it.
6273 */
6274 if (arc_can_share(hdr, lastbuf)) {
6275 arc_share_buf(hdr, lastbuf);
6276 } else {
6277 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
6278 abd_copy_from_buf(hdr->b_l1hdr.b_pabd,
6279 buf->b_data, psize);
6280 }
6281 VERIFY3P(lastbuf->b_data, !=, NULL);
6282 } else if (HDR_SHARED_DATA(hdr)) {
6283 /*
6284 * Uncompressed shared buffers are always at the end
6285 * of the list. Compressed buffers don't have the
6286 * same requirements. This makes it hard to
6287 * simply assert that the lastbuf is shared so
6288 * we rely on the hdr's compression flags to determine
6289 * if we have a compressed, shared buffer.
6290 */
6291 ASSERT(arc_buf_is_shared(lastbuf) ||
6292 arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF);
6293 ASSERT(!ARC_BUF_SHARED(buf));
6294 }
6295 ASSERT(hdr->b_l1hdr.b_pabd != NULL || HDR_HAS_RABD(hdr));
6296 ASSERT3P(state, !=, arc_l2c_only);
6297
6298 (void) zfs_refcount_remove_many(&state->arcs_size,
6299 arc_buf_size(buf), buf);
6300
6301 if (zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt)) {
6302 ASSERT3P(state, !=, arc_l2c_only);
6303 (void) zfs_refcount_remove_many(
6304 &state->arcs_esize[type],
6305 arc_buf_size(buf), buf);
6306 }
6307
6308 hdr->b_l1hdr.b_bufcnt -= 1;
6309 if (ARC_BUF_ENCRYPTED(buf))
6310 hdr->b_crypt_hdr.b_ebufcnt -= 1;
6311
6312 arc_cksum_verify(buf);
6313 arc_buf_unwatch(buf);
6314
6315 /* if this is the last uncompressed buf free the checksum */
6316 if (!arc_hdr_has_uncompressed_buf(hdr))
6317 arc_cksum_free(hdr);
6318
6319 mutex_exit(hash_lock);
6320
6321 /*
6322 * Allocate a new hdr. The new hdr will contain a b_pabd
6323 * buffer which will be freed in arc_write().
6324 */
6325 nhdr = arc_hdr_alloc(spa, psize, lsize, protected,
6326 compress, type, HDR_HAS_RABD(hdr));
6327 ASSERT3P(nhdr->b_l1hdr.b_buf, ==, NULL);
6328 ASSERT0(nhdr->b_l1hdr.b_bufcnt);
6329 ASSERT0(zfs_refcount_count(&nhdr->b_l1hdr.b_refcnt));
6330 VERIFY3U(nhdr->b_type, ==, type);
6331 ASSERT(!HDR_SHARED_DATA(nhdr));
6332
6333 nhdr->b_l1hdr.b_buf = buf;
6334 nhdr->b_l1hdr.b_bufcnt = 1;
6335 if (ARC_BUF_ENCRYPTED(buf))
6336 nhdr->b_crypt_hdr.b_ebufcnt = 1;
6337 (void) zfs_refcount_add(&nhdr->b_l1hdr.b_refcnt, tag);
6338 buf->b_hdr = nhdr;
6339
6340 mutex_exit(&buf->b_evict_lock);
6341 (void) zfs_refcount_add_many(&arc_anon->arcs_size,
6342 arc_buf_size(buf), buf);
6343 } else {
6344 mutex_exit(&buf->b_evict_lock);
6345 ASSERT(zfs_refcount_count(&hdr->b_l1hdr.b_refcnt) == 1);
6346 /* protected by hash lock, or hdr is on arc_anon */
6347 ASSERT(!multilist_link_active(&hdr->b_l1hdr.b_arc_node));
6348 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6349 arc_change_state(arc_anon, hdr, hash_lock);
6350 hdr->b_l1hdr.b_arc_access = 0;
6351
6352 mutex_exit(hash_lock);
6353 buf_discard_identity(hdr);
6354 arc_buf_thaw(buf);
6355 }
6356 }
6357
6358 int
arc_released(arc_buf_t * buf)6359 arc_released(arc_buf_t *buf)
6360 {
6361 int released;
6362
6363 mutex_enter(&buf->b_evict_lock);
6364 released = (buf->b_data != NULL &&
6365 buf->b_hdr->b_l1hdr.b_state == arc_anon);
6366 mutex_exit(&buf->b_evict_lock);
6367 return (released);
6368 }
6369
6370 #ifdef ZFS_DEBUG
6371 int
arc_referenced(arc_buf_t * buf)6372 arc_referenced(arc_buf_t *buf)
6373 {
6374 int referenced;
6375
6376 mutex_enter(&buf->b_evict_lock);
6377 referenced = (zfs_refcount_count(&buf->b_hdr->b_l1hdr.b_refcnt));
6378 mutex_exit(&buf->b_evict_lock);
6379 return (referenced);
6380 }
6381 #endif
6382
6383 static void
arc_write_ready(zio_t * zio)6384 arc_write_ready(zio_t *zio)
6385 {
6386 arc_write_callback_t *callback = zio->io_private;
6387 arc_buf_t *buf = callback->awcb_buf;
6388 arc_buf_hdr_t *hdr = buf->b_hdr;
6389 blkptr_t *bp = zio->io_bp;
6390 uint64_t psize = BP_IS_HOLE(bp) ? 0 : BP_GET_PSIZE(bp);
6391
6392 ASSERT(HDR_HAS_L1HDR(hdr));
6393 ASSERT(!zfs_refcount_is_zero(&buf->b_hdr->b_l1hdr.b_refcnt));
6394 ASSERT(hdr->b_l1hdr.b_bufcnt > 0);
6395
6396 /*
6397 * If we're reexecuting this zio because the pool suspended, then
6398 * cleanup any state that was previously set the first time the
6399 * callback was invoked.
6400 */
6401 if (zio->io_flags & ZIO_FLAG_REEXECUTED) {
6402 arc_cksum_free(hdr);
6403 arc_buf_unwatch(buf);
6404 if (hdr->b_l1hdr.b_pabd != NULL) {
6405 if (arc_buf_is_shared(buf)) {
6406 arc_unshare_buf(hdr, buf);
6407 } else {
6408 arc_hdr_free_pabd(hdr, B_FALSE);
6409 }
6410 }
6411
6412 if (HDR_HAS_RABD(hdr))
6413 arc_hdr_free_pabd(hdr, B_TRUE);
6414 }
6415 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6416 ASSERT(!HDR_HAS_RABD(hdr));
6417 ASSERT(!HDR_SHARED_DATA(hdr));
6418 ASSERT(!arc_buf_is_shared(buf));
6419
6420 callback->awcb_ready(zio, buf, callback->awcb_private);
6421
6422 if (HDR_IO_IN_PROGRESS(hdr))
6423 ASSERT(zio->io_flags & ZIO_FLAG_REEXECUTED);
6424
6425 arc_hdr_set_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6426
6427 if (BP_IS_PROTECTED(bp) != !!HDR_PROTECTED(hdr))
6428 hdr = arc_hdr_realloc_crypt(hdr, BP_IS_PROTECTED(bp));
6429
6430 if (BP_IS_PROTECTED(bp)) {
6431 /* ZIL blocks are written through zio_rewrite */
6432 ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
6433 ASSERT(HDR_PROTECTED(hdr));
6434
6435 if (BP_SHOULD_BYTESWAP(bp)) {
6436 if (BP_GET_LEVEL(bp) > 0) {
6437 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_UINT64;
6438 } else {
6439 hdr->b_l1hdr.b_byteswap =
6440 DMU_OT_BYTESWAP(BP_GET_TYPE(bp));
6441 }
6442 } else {
6443 hdr->b_l1hdr.b_byteswap = DMU_BSWAP_NUMFUNCS;
6444 }
6445
6446 hdr->b_crypt_hdr.b_ot = BP_GET_TYPE(bp);
6447 hdr->b_crypt_hdr.b_dsobj = zio->io_bookmark.zb_objset;
6448 zio_crypt_decode_params_bp(bp, hdr->b_crypt_hdr.b_salt,
6449 hdr->b_crypt_hdr.b_iv);
6450 zio_crypt_decode_mac_bp(bp, hdr->b_crypt_hdr.b_mac);
6451 }
6452
6453 /*
6454 * If this block was written for raw encryption but the zio layer
6455 * ended up only authenticating it, adjust the buffer flags now.
6456 */
6457 if (BP_IS_AUTHENTICATED(bp) && ARC_BUF_ENCRYPTED(buf)) {
6458 arc_hdr_set_flags(hdr, ARC_FLAG_NOAUTH);
6459 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
6460 if (BP_GET_COMPRESS(bp) == ZIO_COMPRESS_OFF)
6461 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
6462 } else if (BP_IS_HOLE(bp) && ARC_BUF_ENCRYPTED(buf)) {
6463 buf->b_flags &= ~ARC_BUF_FLAG_ENCRYPTED;
6464 buf->b_flags &= ~ARC_BUF_FLAG_COMPRESSED;
6465 }
6466
6467 /* this must be done after the buffer flags are adjusted */
6468 arc_cksum_compute(buf);
6469
6470 enum zio_compress compress;
6471 if (BP_IS_HOLE(bp) || BP_IS_EMBEDDED(bp)) {
6472 compress = ZIO_COMPRESS_OFF;
6473 } else {
6474 ASSERT3U(HDR_GET_LSIZE(hdr), ==, BP_GET_LSIZE(bp));
6475 compress = BP_GET_COMPRESS(bp);
6476 }
6477 HDR_SET_PSIZE(hdr, psize);
6478 arc_hdr_set_compress(hdr, compress);
6479
6480 if (zio->io_error != 0 || psize == 0)
6481 goto out;
6482
6483 /*
6484 * Fill the hdr with data. If the buffer is encrypted we have no choice
6485 * but to copy the data into b_rabd. If the hdr is compressed, the data
6486 * we want is available from the zio, otherwise we can take it from
6487 * the buf.
6488 *
6489 * We might be able to share the buf's data with the hdr here. However,
6490 * doing so would cause the ARC to be full of linear ABDs if we write a
6491 * lot of shareable data. As a compromise, we check whether scattered
6492 * ABDs are allowed, and assume that if they are then the user wants
6493 * the ARC to be primarily filled with them regardless of the data being
6494 * written. Therefore, if they're allowed then we allocate one and copy
6495 * the data into it; otherwise, we share the data directly if we can.
6496 */
6497 if (ARC_BUF_ENCRYPTED(buf)) {
6498 ASSERT3U(psize, >, 0);
6499 ASSERT(ARC_BUF_COMPRESSED(buf));
6500 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT|ARC_HDR_ALLOC_RDATA);
6501 abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
6502 } else if (zfs_abd_scatter_enabled || !arc_can_share(hdr, buf)) {
6503 /*
6504 * Ideally, we would always copy the io_abd into b_pabd, but the
6505 * user may have disabled compressed ARC, thus we must check the
6506 * hdr's compression setting rather than the io_bp's.
6507 */
6508 if (BP_IS_ENCRYPTED(bp)) {
6509 ASSERT3U(psize, >, 0);
6510 arc_hdr_alloc_pabd(hdr,
6511 ARC_HDR_DO_ADAPT|ARC_HDR_ALLOC_RDATA);
6512 abd_copy(hdr->b_crypt_hdr.b_rabd, zio->io_abd, psize);
6513 } else if (arc_hdr_get_compress(hdr) != ZIO_COMPRESS_OFF &&
6514 !ARC_BUF_COMPRESSED(buf)) {
6515 ASSERT3U(psize, >, 0);
6516 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
6517 abd_copy(hdr->b_l1hdr.b_pabd, zio->io_abd, psize);
6518 } else {
6519 ASSERT3U(zio->io_orig_size, ==, arc_hdr_size(hdr));
6520 arc_hdr_alloc_pabd(hdr, ARC_HDR_DO_ADAPT);
6521 abd_copy_from_buf(hdr->b_l1hdr.b_pabd, buf->b_data,
6522 arc_buf_size(buf));
6523 }
6524 } else {
6525 ASSERT3P(buf->b_data, ==, abd_to_buf(zio->io_orig_abd));
6526 ASSERT3U(zio->io_orig_size, ==, arc_buf_size(buf));
6527 ASSERT3U(hdr->b_l1hdr.b_bufcnt, ==, 1);
6528 arc_share_buf(hdr, buf);
6529 }
6530
6531 out:
6532 arc_hdr_verify(hdr, bp);
6533 }
6534
6535 static void
arc_write_children_ready(zio_t * zio)6536 arc_write_children_ready(zio_t *zio)
6537 {
6538 arc_write_callback_t *callback = zio->io_private;
6539 arc_buf_t *buf = callback->awcb_buf;
6540
6541 callback->awcb_children_ready(zio, buf, callback->awcb_private);
6542 }
6543
6544 /*
6545 * The SPA calls this callback for each physical write that happens on behalf
6546 * of a logical write. See the comment in dbuf_write_physdone() for details.
6547 */
6548 static void
arc_write_physdone(zio_t * zio)6549 arc_write_physdone(zio_t *zio)
6550 {
6551 arc_write_callback_t *cb = zio->io_private;
6552 if (cb->awcb_physdone != NULL)
6553 cb->awcb_physdone(zio, cb->awcb_buf, cb->awcb_private);
6554 }
6555
6556 static void
arc_write_done(zio_t * zio)6557 arc_write_done(zio_t *zio)
6558 {
6559 arc_write_callback_t *callback = zio->io_private;
6560 arc_buf_t *buf = callback->awcb_buf;
6561 arc_buf_hdr_t *hdr = buf->b_hdr;
6562
6563 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6564
6565 if (zio->io_error == 0) {
6566 arc_hdr_verify(hdr, zio->io_bp);
6567
6568 if (BP_IS_HOLE(zio->io_bp) || BP_IS_EMBEDDED(zio->io_bp)) {
6569 buf_discard_identity(hdr);
6570 } else {
6571 hdr->b_dva = *BP_IDENTITY(zio->io_bp);
6572 hdr->b_birth = BP_PHYSICAL_BIRTH(zio->io_bp);
6573 }
6574 } else {
6575 ASSERT(HDR_EMPTY(hdr));
6576 }
6577
6578 /*
6579 * If the block to be written was all-zero or compressed enough to be
6580 * embedded in the BP, no write was performed so there will be no
6581 * dva/birth/checksum. The buffer must therefore remain anonymous
6582 * (and uncached).
6583 */
6584 if (!HDR_EMPTY(hdr)) {
6585 arc_buf_hdr_t *exists;
6586 kmutex_t *hash_lock;
6587
6588 ASSERT3U(zio->io_error, ==, 0);
6589
6590 arc_cksum_verify(buf);
6591
6592 exists = buf_hash_insert(hdr, &hash_lock);
6593 if (exists != NULL) {
6594 /*
6595 * This can only happen if we overwrite for
6596 * sync-to-convergence, because we remove
6597 * buffers from the hash table when we arc_free().
6598 */
6599 if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
6600 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6601 panic("bad overwrite, hdr=%p exists=%p",
6602 (void *)hdr, (void *)exists);
6603 ASSERT(zfs_refcount_is_zero(
6604 &exists->b_l1hdr.b_refcnt));
6605 arc_change_state(arc_anon, exists, hash_lock);
6606 arc_hdr_destroy(exists);
6607 mutex_exit(hash_lock);
6608 exists = buf_hash_insert(hdr, &hash_lock);
6609 ASSERT3P(exists, ==, NULL);
6610 } else if (zio->io_flags & ZIO_FLAG_NOPWRITE) {
6611 /* nopwrite */
6612 ASSERT(zio->io_prop.zp_nopwrite);
6613 if (!BP_EQUAL(&zio->io_bp_orig, zio->io_bp))
6614 panic("bad nopwrite, hdr=%p exists=%p",
6615 (void *)hdr, (void *)exists);
6616 } else {
6617 /* Dedup */
6618 ASSERT(hdr->b_l1hdr.b_bufcnt == 1);
6619 ASSERT(hdr->b_l1hdr.b_state == arc_anon);
6620 ASSERT(BP_GET_DEDUP(zio->io_bp));
6621 ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
6622 }
6623 }
6624 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6625 /* if it's not anon, we are doing a scrub */
6626 if (exists == NULL && hdr->b_l1hdr.b_state == arc_anon)
6627 arc_access(hdr, hash_lock);
6628 mutex_exit(hash_lock);
6629 } else {
6630 arc_hdr_clear_flags(hdr, ARC_FLAG_IO_IN_PROGRESS);
6631 }
6632
6633 ASSERT(!zfs_refcount_is_zero(&hdr->b_l1hdr.b_refcnt));
6634 callback->awcb_done(zio, buf, callback->awcb_private);
6635
6636 abd_put(zio->io_abd);
6637 kmem_free(callback, sizeof (arc_write_callback_t));
6638 }
6639
6640 zio_t *
arc_write(zio_t * pio,spa_t * spa,uint64_t txg,blkptr_t * bp,arc_buf_t * buf,boolean_t l2arc,const zio_prop_t * zp,arc_write_done_func_t * ready,arc_write_done_func_t * children_ready,arc_write_done_func_t * physdone,arc_write_done_func_t * done,void * private,zio_priority_t priority,int zio_flags,const zbookmark_phys_t * zb)6641 arc_write(zio_t *pio, spa_t *spa, uint64_t txg, blkptr_t *bp, arc_buf_t *buf,
6642 boolean_t l2arc, const zio_prop_t *zp, arc_write_done_func_t *ready,
6643 arc_write_done_func_t *children_ready, arc_write_done_func_t *physdone,
6644 arc_write_done_func_t *done, void *private, zio_priority_t priority,
6645 int zio_flags, const zbookmark_phys_t *zb)
6646 {
6647 arc_buf_hdr_t *hdr = buf->b_hdr;
6648 arc_write_callback_t *callback;
6649 zio_t *zio;
6650 zio_prop_t localprop = *zp;
6651
6652 ASSERT3P(ready, !=, NULL);
6653 ASSERT3P(done, !=, NULL);
6654 ASSERT(!HDR_IO_ERROR(hdr));
6655 ASSERT(!HDR_IO_IN_PROGRESS(hdr));
6656 ASSERT3P(hdr->b_l1hdr.b_acb, ==, NULL);
6657 ASSERT3U(hdr->b_l1hdr.b_bufcnt, >, 0);
6658 if (l2arc)
6659 arc_hdr_set_flags(hdr, ARC_FLAG_L2CACHE);
6660
6661 if (ARC_BUF_ENCRYPTED(buf)) {
6662 ASSERT(ARC_BUF_COMPRESSED(buf));
6663 localprop.zp_encrypt = B_TRUE;
6664 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6665 /* CONSTCOND */
6666 localprop.zp_byteorder =
6667 (hdr->b_l1hdr.b_byteswap == DMU_BSWAP_NUMFUNCS) ?
6668 ZFS_HOST_BYTEORDER : !ZFS_HOST_BYTEORDER;
6669 bcopy(hdr->b_crypt_hdr.b_salt, localprop.zp_salt,
6670 ZIO_DATA_SALT_LEN);
6671 bcopy(hdr->b_crypt_hdr.b_iv, localprop.zp_iv,
6672 ZIO_DATA_IV_LEN);
6673 bcopy(hdr->b_crypt_hdr.b_mac, localprop.zp_mac,
6674 ZIO_DATA_MAC_LEN);
6675 if (DMU_OT_IS_ENCRYPTED(localprop.zp_type)) {
6676 localprop.zp_nopwrite = B_FALSE;
6677 localprop.zp_copies =
6678 MIN(localprop.zp_copies, SPA_DVAS_PER_BP - 1);
6679 }
6680 zio_flags |= ZIO_FLAG_RAW;
6681 } else if (ARC_BUF_COMPRESSED(buf)) {
6682 ASSERT3U(HDR_GET_LSIZE(hdr), !=, arc_buf_size(buf));
6683 localprop.zp_compress = HDR_GET_COMPRESS(hdr);
6684 zio_flags |= ZIO_FLAG_RAW_COMPRESS;
6685 }
6686
6687 callback = kmem_zalloc(sizeof (arc_write_callback_t), KM_SLEEP);
6688 callback->awcb_ready = ready;
6689 callback->awcb_children_ready = children_ready;
6690 callback->awcb_physdone = physdone;
6691 callback->awcb_done = done;
6692 callback->awcb_private = private;
6693 callback->awcb_buf = buf;
6694
6695 /*
6696 * The hdr's b_pabd is now stale, free it now. A new data block
6697 * will be allocated when the zio pipeline calls arc_write_ready().
6698 */
6699 if (hdr->b_l1hdr.b_pabd != NULL) {
6700 /*
6701 * If the buf is currently sharing the data block with
6702 * the hdr then we need to break that relationship here.
6703 * The hdr will remain with a NULL data pointer and the
6704 * buf will take sole ownership of the block.
6705 */
6706 if (arc_buf_is_shared(buf)) {
6707 arc_unshare_buf(hdr, buf);
6708 } else {
6709 arc_hdr_free_pabd(hdr, B_FALSE);
6710 }
6711 VERIFY3P(buf->b_data, !=, NULL);
6712 }
6713
6714 if (HDR_HAS_RABD(hdr))
6715 arc_hdr_free_pabd(hdr, B_TRUE);
6716
6717 if (!(zio_flags & ZIO_FLAG_RAW))
6718 arc_hdr_set_compress(hdr, ZIO_COMPRESS_OFF);
6719
6720 ASSERT(!arc_buf_is_shared(buf));
6721 ASSERT3P(hdr->b_l1hdr.b_pabd, ==, NULL);
6722
6723 zio = zio_write(pio, spa, txg, bp,
6724 abd_get_from_buf(buf->b_data, HDR_GET_LSIZE(hdr)),
6725 HDR_GET_LSIZE(hdr), arc_buf_size(buf), &localprop, arc_write_ready,
6726 (children_ready != NULL) ? arc_write_children_ready : NULL,
6727 arc_write_physdone, arc_write_done, callback,
6728 priority, zio_flags, zb);
6729
6730 return (zio);
6731 }
6732
6733 static int
arc_memory_throttle(spa_t * spa,uint64_t reserve,uint64_t txg)6734 arc_memory_throttle(spa_t *spa, uint64_t reserve, uint64_t txg)
6735 {
6736 #ifdef _KERNEL
6737 uint64_t available_memory = ptob(freemem);
6738
6739
6740 if (freemem > physmem * arc_lotsfree_percent / 100)
6741 return (0);
6742
6743 if (txg > spa->spa_lowmem_last_txg) {
6744 spa->spa_lowmem_last_txg = txg;
6745 spa->spa_lowmem_page_load = 0;
6746 }
6747 /*
6748 * If we are in pageout, we know that memory is already tight,
6749 * the arc is already going to be evicting, so we just want to
6750 * continue to let page writes occur as quickly as possible.
6751 */
6752 if (curproc == proc_pageout) {
6753 if (spa->spa_lowmem_page_load >
6754 MAX(ptob(minfree), available_memory) / 4)
6755 return (SET_ERROR(ERESTART));
6756 /* Note: reserve is inflated, so we deflate */
6757 atomic_add_64(&spa->spa_lowmem_page_load, reserve / 8);
6758 return (0);
6759 } else if (spa->spa_lowmem_page_load > 0 && arc_reclaim_needed()) {
6760 /* memory is low, delay before restarting */
6761 ARCSTAT_INCR(arcstat_memory_throttle_count, 1);
6762 return (SET_ERROR(EAGAIN));
6763 }
6764 spa->spa_lowmem_page_load = 0;
6765 #endif /* _KERNEL */
6766 return (0);
6767 }
6768
6769 /*
6770 * In more extreme cases, return B_TRUE if system memory is tight enough
6771 * that ZFS should defer work requiring new allocations.
6772 */
6773 boolean_t
arc_memory_is_low(void)6774 arc_memory_is_low(void)
6775 {
6776 #ifdef _KERNEL
6777 if (freemem < minfree + needfree)
6778 return (B_TRUE);
6779 #endif /* _KERNEL */
6780 return (B_FALSE);
6781 }
6782
6783 void
arc_tempreserve_clear(uint64_t reserve)6784 arc_tempreserve_clear(uint64_t reserve)
6785 {
6786 atomic_add_64(&arc_tempreserve, -reserve);
6787 ASSERT((int64_t)arc_tempreserve >= 0);
6788 }
6789
6790 int
arc_tempreserve_space(spa_t * spa,uint64_t reserve,uint64_t txg)6791 arc_tempreserve_space(spa_t *spa, uint64_t reserve, uint64_t txg)
6792 {
6793 int error;
6794 uint64_t anon_size;
6795
6796 if (reserve > arc_c/4 && !arc_no_grow)
6797 arc_c = MIN(arc_c_max, reserve * 4);
6798 if (reserve > arc_c)
6799 return (SET_ERROR(ENOMEM));
6800
6801 /*
6802 * Don't count loaned bufs as in flight dirty data to prevent long
6803 * network delays from blocking transactions that are ready to be
6804 * assigned to a txg.
6805 */
6806
6807 /* assert that it has not wrapped around */
6808 ASSERT3S(atomic_add_64_nv(&arc_loaned_bytes, 0), >=, 0);
6809
6810 anon_size = MAX((int64_t)(zfs_refcount_count(&arc_anon->arcs_size) -
6811 arc_loaned_bytes), 0);
6812
6813 /*
6814 * Writes will, almost always, require additional memory allocations
6815 * in order to compress/encrypt/etc the data. We therefore need to
6816 * make sure that there is sufficient available memory for this.
6817 */
6818 error = arc_memory_throttle(spa, reserve, txg);
6819 if (error != 0)
6820 return (error);
6821
6822 /*
6823 * Throttle writes when the amount of dirty data in the cache
6824 * gets too large. We try to keep the cache less than half full
6825 * of dirty blocks so that our sync times don't grow too large.
6826 *
6827 * In the case of one pool being built on another pool, we want
6828 * to make sure we don't end up throttling the lower (backing)
6829 * pool when the upper pool is the majority contributor to dirty
6830 * data. To insure we make forward progress during throttling, we
6831 * also check the current pool's net dirty data and only throttle
6832 * if it exceeds zfs_arc_pool_dirty_percent of the anonymous dirty
6833 * data in the cache.
6834 *
6835 * Note: if two requests come in concurrently, we might let them
6836 * both succeed, when one of them should fail. Not a huge deal.
6837 */
6838 uint64_t total_dirty = reserve + arc_tempreserve + anon_size;
6839 uint64_t spa_dirty_anon = spa_dirty_data(spa);
6840
6841 if (total_dirty > arc_c * zfs_arc_dirty_limit_percent / 100 &&
6842 anon_size > arc_c * zfs_arc_anon_limit_percent / 100 &&
6843 spa_dirty_anon > anon_size * zfs_arc_pool_dirty_percent / 100) {
6844 uint64_t meta_esize =
6845 zfs_refcount_count(
6846 &arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6847 uint64_t data_esize =
6848 zfs_refcount_count(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
6849 dprintf("failing, arc_tempreserve=%lluK anon_meta=%lluK "
6850 "anon_data=%lluK tempreserve=%lluK arc_c=%lluK\n",
6851 arc_tempreserve >> 10, meta_esize >> 10,
6852 data_esize >> 10, reserve >> 10, arc_c >> 10);
6853 return (SET_ERROR(ERESTART));
6854 }
6855 atomic_add_64(&arc_tempreserve, reserve);
6856 return (0);
6857 }
6858
6859 static void
arc_kstat_update_state(arc_state_t * state,kstat_named_t * size,kstat_named_t * evict_data,kstat_named_t * evict_metadata)6860 arc_kstat_update_state(arc_state_t *state, kstat_named_t *size,
6861 kstat_named_t *evict_data, kstat_named_t *evict_metadata)
6862 {
6863 size->value.ui64 = zfs_refcount_count(&state->arcs_size);
6864 evict_data->value.ui64 =
6865 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_DATA]);
6866 evict_metadata->value.ui64 =
6867 zfs_refcount_count(&state->arcs_esize[ARC_BUFC_METADATA]);
6868 }
6869
6870 static int
arc_kstat_update(kstat_t * ksp,int rw)6871 arc_kstat_update(kstat_t *ksp, int rw)
6872 {
6873 arc_stats_t *as = ksp->ks_data;
6874
6875 if (rw == KSTAT_WRITE) {
6876 return (EACCES);
6877 } else {
6878 arc_kstat_update_state(arc_anon,
6879 &as->arcstat_anon_size,
6880 &as->arcstat_anon_evictable_data,
6881 &as->arcstat_anon_evictable_metadata);
6882 arc_kstat_update_state(arc_mru,
6883 &as->arcstat_mru_size,
6884 &as->arcstat_mru_evictable_data,
6885 &as->arcstat_mru_evictable_metadata);
6886 arc_kstat_update_state(arc_mru_ghost,
6887 &as->arcstat_mru_ghost_size,
6888 &as->arcstat_mru_ghost_evictable_data,
6889 &as->arcstat_mru_ghost_evictable_metadata);
6890 arc_kstat_update_state(arc_mfu,
6891 &as->arcstat_mfu_size,
6892 &as->arcstat_mfu_evictable_data,
6893 &as->arcstat_mfu_evictable_metadata);
6894 arc_kstat_update_state(arc_mfu_ghost,
6895 &as->arcstat_mfu_ghost_size,
6896 &as->arcstat_mfu_ghost_evictable_data,
6897 &as->arcstat_mfu_ghost_evictable_metadata);
6898
6899 ARCSTAT(arcstat_size) = aggsum_value(&arc_size);
6900 ARCSTAT(arcstat_meta_used) = aggsum_value(&arc_meta_used);
6901 ARCSTAT(arcstat_data_size) = aggsum_value(&astat_data_size);
6902 ARCSTAT(arcstat_metadata_size) =
6903 aggsum_value(&astat_metadata_size);
6904 ARCSTAT(arcstat_hdr_size) = aggsum_value(&astat_hdr_size);
6905 ARCSTAT(arcstat_other_size) = aggsum_value(&astat_other_size);
6906 ARCSTAT(arcstat_l2_hdr_size) = aggsum_value(&astat_l2_hdr_size);
6907 }
6908
6909 return (0);
6910 }
6911
6912 /*
6913 * This function *must* return indices evenly distributed between all
6914 * sublists of the multilist. This is needed due to how the ARC eviction
6915 * code is laid out; arc_evict_state() assumes ARC buffers are evenly
6916 * distributed between all sublists and uses this assumption when
6917 * deciding which sublist to evict from and how much to evict from it.
6918 */
6919 unsigned int
arc_state_multilist_index_func(multilist_t * ml,void * obj)6920 arc_state_multilist_index_func(multilist_t *ml, void *obj)
6921 {
6922 arc_buf_hdr_t *hdr = obj;
6923
6924 /*
6925 * We rely on b_dva to generate evenly distributed index
6926 * numbers using buf_hash below. So, as an added precaution,
6927 * let's make sure we never add empty buffers to the arc lists.
6928 */
6929 ASSERT(!HDR_EMPTY(hdr));
6930
6931 /*
6932 * The assumption here, is the hash value for a given
6933 * arc_buf_hdr_t will remain constant throughout its lifetime
6934 * (i.e. its b_spa, b_dva, and b_birth fields don't change).
6935 * Thus, we don't need to store the header's sublist index
6936 * on insertion, as this index can be recalculated on removal.
6937 *
6938 * Also, the low order bits of the hash value are thought to be
6939 * distributed evenly. Otherwise, in the case that the multilist
6940 * has a power of two number of sublists, each sublists' usage
6941 * would not be evenly distributed.
6942 */
6943 return (buf_hash(hdr->b_spa, &hdr->b_dva, hdr->b_birth) %
6944 multilist_get_num_sublists(ml));
6945 }
6946
6947 static void
arc_state_init(void)6948 arc_state_init(void)
6949 {
6950 arc_anon = &ARC_anon;
6951 arc_mru = &ARC_mru;
6952 arc_mru_ghost = &ARC_mru_ghost;
6953 arc_mfu = &ARC_mfu;
6954 arc_mfu_ghost = &ARC_mfu_ghost;
6955 arc_l2c_only = &ARC_l2c_only;
6956
6957 arc_mru->arcs_list[ARC_BUFC_METADATA] =
6958 multilist_create(sizeof (arc_buf_hdr_t),
6959 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6960 arc_state_multilist_index_func);
6961 arc_mru->arcs_list[ARC_BUFC_DATA] =
6962 multilist_create(sizeof (arc_buf_hdr_t),
6963 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6964 arc_state_multilist_index_func);
6965 arc_mru_ghost->arcs_list[ARC_BUFC_METADATA] =
6966 multilist_create(sizeof (arc_buf_hdr_t),
6967 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6968 arc_state_multilist_index_func);
6969 arc_mru_ghost->arcs_list[ARC_BUFC_DATA] =
6970 multilist_create(sizeof (arc_buf_hdr_t),
6971 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6972 arc_state_multilist_index_func);
6973 arc_mfu->arcs_list[ARC_BUFC_METADATA] =
6974 multilist_create(sizeof (arc_buf_hdr_t),
6975 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6976 arc_state_multilist_index_func);
6977 arc_mfu->arcs_list[ARC_BUFC_DATA] =
6978 multilist_create(sizeof (arc_buf_hdr_t),
6979 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6980 arc_state_multilist_index_func);
6981 arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA] =
6982 multilist_create(sizeof (arc_buf_hdr_t),
6983 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6984 arc_state_multilist_index_func);
6985 arc_mfu_ghost->arcs_list[ARC_BUFC_DATA] =
6986 multilist_create(sizeof (arc_buf_hdr_t),
6987 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6988 arc_state_multilist_index_func);
6989 arc_l2c_only->arcs_list[ARC_BUFC_METADATA] =
6990 multilist_create(sizeof (arc_buf_hdr_t),
6991 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6992 arc_state_multilist_index_func);
6993 arc_l2c_only->arcs_list[ARC_BUFC_DATA] =
6994 multilist_create(sizeof (arc_buf_hdr_t),
6995 offsetof(arc_buf_hdr_t, b_l1hdr.b_arc_node),
6996 arc_state_multilist_index_func);
6997
6998 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
6999 zfs_refcount_create(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7000 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
7001 zfs_refcount_create(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
7002 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
7003 zfs_refcount_create(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
7004 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
7005 zfs_refcount_create(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
7006 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
7007 zfs_refcount_create(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
7008 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
7009 zfs_refcount_create(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
7010
7011 zfs_refcount_create(&arc_anon->arcs_size);
7012 zfs_refcount_create(&arc_mru->arcs_size);
7013 zfs_refcount_create(&arc_mru_ghost->arcs_size);
7014 zfs_refcount_create(&arc_mfu->arcs_size);
7015 zfs_refcount_create(&arc_mfu_ghost->arcs_size);
7016 zfs_refcount_create(&arc_l2c_only->arcs_size);
7017
7018 aggsum_init(&arc_meta_used, 0);
7019 aggsum_init(&arc_size, 0);
7020 aggsum_init(&astat_data_size, 0);
7021 aggsum_init(&astat_metadata_size, 0);
7022 aggsum_init(&astat_hdr_size, 0);
7023 aggsum_init(&astat_other_size, 0);
7024 aggsum_init(&astat_l2_hdr_size, 0);
7025
7026 arc_anon->arcs_state = ARC_STATE_ANON;
7027 arc_mru->arcs_state = ARC_STATE_MRU;
7028 arc_mru_ghost->arcs_state = ARC_STATE_MRU_GHOST;
7029 arc_mfu->arcs_state = ARC_STATE_MFU;
7030 arc_mfu_ghost->arcs_state = ARC_STATE_MFU_GHOST;
7031 arc_l2c_only->arcs_state = ARC_STATE_L2C_ONLY;
7032 }
7033
7034 static void
arc_state_fini(void)7035 arc_state_fini(void)
7036 {
7037 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_METADATA]);
7038 zfs_refcount_destroy(&arc_anon->arcs_esize[ARC_BUFC_DATA]);
7039 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_METADATA]);
7040 zfs_refcount_destroy(&arc_mru->arcs_esize[ARC_BUFC_DATA]);
7041 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_METADATA]);
7042 zfs_refcount_destroy(&arc_mru_ghost->arcs_esize[ARC_BUFC_DATA]);
7043 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_METADATA]);
7044 zfs_refcount_destroy(&arc_mfu->arcs_esize[ARC_BUFC_DATA]);
7045 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_METADATA]);
7046 zfs_refcount_destroy(&arc_mfu_ghost->arcs_esize[ARC_BUFC_DATA]);
7047 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_METADATA]);
7048 zfs_refcount_destroy(&arc_l2c_only->arcs_esize[ARC_BUFC_DATA]);
7049
7050 zfs_refcount_destroy(&arc_anon->arcs_size);
7051 zfs_refcount_destroy(&arc_mru->arcs_size);
7052 zfs_refcount_destroy(&arc_mru_ghost->arcs_size);
7053 zfs_refcount_destroy(&arc_mfu->arcs_size);
7054 zfs_refcount_destroy(&arc_mfu_ghost->arcs_size);
7055 zfs_refcount_destroy(&arc_l2c_only->arcs_size);
7056
7057 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_METADATA]);
7058 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_METADATA]);
7059 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_METADATA]);
7060 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_METADATA]);
7061 multilist_destroy(arc_mru->arcs_list[ARC_BUFC_DATA]);
7062 multilist_destroy(arc_mru_ghost->arcs_list[ARC_BUFC_DATA]);
7063 multilist_destroy(arc_mfu->arcs_list[ARC_BUFC_DATA]);
7064 multilist_destroy(arc_mfu_ghost->arcs_list[ARC_BUFC_DATA]);
7065 multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_METADATA]);
7066 multilist_destroy(arc_l2c_only->arcs_list[ARC_BUFC_DATA]);
7067
7068 aggsum_fini(&arc_meta_used);
7069 aggsum_fini(&arc_size);
7070 aggsum_fini(&astat_data_size);
7071 aggsum_fini(&astat_metadata_size);
7072 aggsum_fini(&astat_hdr_size);
7073 aggsum_fini(&astat_other_size);
7074 aggsum_fini(&astat_l2_hdr_size);
7075
7076 }
7077
7078 uint64_t
arc_max_bytes(void)7079 arc_max_bytes(void)
7080 {
7081 return (arc_c_max);
7082 }
7083
7084 void
arc_init(void)7085 arc_init(void)
7086 {
7087 /*
7088 * allmem is "all memory that we could possibly use".
7089 */
7090 #ifdef _KERNEL
7091 uint64_t allmem = ptob(physmem - swapfs_minfree);
7092 #else
7093 uint64_t allmem = (physmem * PAGESIZE) / 2;
7094 #endif
7095 mutex_init(&arc_adjust_lock, NULL, MUTEX_DEFAULT, NULL);
7096 cv_init(&arc_adjust_waiters_cv, NULL, CV_DEFAULT, NULL);
7097
7098 /*
7099 * Set the minimum cache size to 1/64 of all memory, with a hard
7100 * minimum of 64MB.
7101 */
7102 arc_c_min = MAX(allmem / 64, 64 << 20);
7103 /*
7104 * In a system with a lot of physical memory this will still result in
7105 * an ARC size floor that is quite large in absolute terms. Cap the
7106 * growth of the value at 1GB.
7107 */
7108 arc_c_min = MIN(arc_c_min, 1 << 30);
7109
7110 /* set max to 3/4 of all memory, or all but 1GB, whichever is more */
7111 if (allmem >= 1 << 30)
7112 arc_c_max = allmem - (1 << 30);
7113 else
7114 arc_c_max = arc_c_min;
7115 arc_c_max = MAX(allmem * 3 / 4, arc_c_max);
7116
7117 /*
7118 * In userland, there's only the memory pressure that we artificially
7119 * create (see arc_available_memory()). Don't let arc_c get too
7120 * small, because it can cause transactions to be larger than
7121 * arc_c, causing arc_tempreserve_space() to fail.
7122 */
7123 #ifndef _KERNEL
7124 arc_c_min = arc_c_max / 2;
7125 #endif
7126
7127 /*
7128 * Allow the tunables to override our calculations if they are
7129 * reasonable (ie. over 64MB)
7130 */
7131 if (zfs_arc_max > 64 << 20 && zfs_arc_max < allmem) {
7132 arc_c_max = zfs_arc_max;
7133 arc_c_min = MIN(arc_c_min, arc_c_max);
7134 }
7135 if (zfs_arc_min > 64 << 20 && zfs_arc_min <= arc_c_max)
7136 arc_c_min = zfs_arc_min;
7137
7138 arc_c = arc_c_max;
7139 arc_p = (arc_c >> 1);
7140
7141 /* limit meta-data to 1/4 of the arc capacity */
7142 arc_meta_limit = arc_c_max / 4;
7143
7144 #ifdef _KERNEL
7145 /*
7146 * Metadata is stored in the kernel's heap. Don't let us
7147 * use more than half the heap for the ARC.
7148 */
7149 arc_meta_limit = MIN(arc_meta_limit,
7150 vmem_size(heap_arena, VMEM_ALLOC | VMEM_FREE) / 2);
7151 #endif
7152
7153 /* Allow the tunable to override if it is reasonable */
7154 if (zfs_arc_meta_limit > 0 && zfs_arc_meta_limit <= arc_c_max)
7155 arc_meta_limit = zfs_arc_meta_limit;
7156
7157 if (zfs_arc_meta_min > 0) {
7158 arc_meta_min = zfs_arc_meta_min;
7159 } else {
7160 arc_meta_min = arc_c_min / 2;
7161 }
7162
7163 if (zfs_arc_grow_retry > 0)
7164 arc_grow_retry = zfs_arc_grow_retry;
7165
7166 if (zfs_arc_shrink_shift > 0)
7167 arc_shrink_shift = zfs_arc_shrink_shift;
7168
7169 /*
7170 * Ensure that arc_no_grow_shift is less than arc_shrink_shift.
7171 */
7172 if (arc_no_grow_shift >= arc_shrink_shift)
7173 arc_no_grow_shift = arc_shrink_shift - 1;
7174
7175 if (zfs_arc_p_min_shift > 0)
7176 arc_p_min_shift = zfs_arc_p_min_shift;
7177
7178 /* if kmem_flags are set, lets try to use less memory */
7179 if (kmem_debugging())
7180 arc_c = arc_c / 2;
7181 if (arc_c < arc_c_min)
7182 arc_c = arc_c_min;
7183
7184 arc_state_init();
7185
7186 /*
7187 * The arc must be "uninitialized", so that hdr_recl() (which is
7188 * registered by buf_init()) will not access arc_reap_zthr before
7189 * it is created.
7190 */
7191 ASSERT(!arc_initialized);
7192 buf_init();
7193
7194 arc_ksp = kstat_create("zfs", 0, "arcstats", "misc", KSTAT_TYPE_NAMED,
7195 sizeof (arc_stats) / sizeof (kstat_named_t), KSTAT_FLAG_VIRTUAL);
7196
7197 if (arc_ksp != NULL) {
7198 arc_ksp->ks_data = &arc_stats;
7199 arc_ksp->ks_update = arc_kstat_update;
7200 kstat_install(arc_ksp);
7201 }
7202
7203 arc_adjust_zthr = zthr_create(arc_adjust_cb_check,
7204 arc_adjust_cb, NULL);
7205 arc_reap_zthr = zthr_create_timer(arc_reap_cb_check,
7206 arc_reap_cb, NULL, SEC2NSEC(1));
7207
7208 arc_initialized = B_TRUE;
7209 arc_warm = B_FALSE;
7210
7211 /*
7212 * Calculate maximum amount of dirty data per pool.
7213 *
7214 * If it has been set by /etc/system, take that.
7215 * Otherwise, use a percentage of physical memory defined by
7216 * zfs_dirty_data_max_percent (default 10%) with a cap at
7217 * zfs_dirty_data_max_max (default 4GB).
7218 */
7219 if (zfs_dirty_data_max == 0) {
7220 zfs_dirty_data_max = physmem * PAGESIZE *
7221 zfs_dirty_data_max_percent / 100;
7222 zfs_dirty_data_max = MIN(zfs_dirty_data_max,
7223 zfs_dirty_data_max_max);
7224 }
7225 }
7226
7227 void
arc_fini(void)7228 arc_fini(void)
7229 {
7230 /* Use B_TRUE to ensure *all* buffers are evicted */
7231 arc_flush(NULL, B_TRUE);
7232
7233 arc_initialized = B_FALSE;
7234
7235 if (arc_ksp != NULL) {
7236 kstat_delete(arc_ksp);
7237 arc_ksp = NULL;
7238 }
7239
7240 (void) zthr_cancel(arc_adjust_zthr);
7241 zthr_destroy(arc_adjust_zthr);
7242
7243 (void) zthr_cancel(arc_reap_zthr);
7244 zthr_destroy(arc_reap_zthr);
7245
7246 mutex_destroy(&arc_adjust_lock);
7247 cv_destroy(&arc_adjust_waiters_cv);
7248
7249 /*
7250 * buf_fini() must proceed arc_state_fini() because buf_fin() may
7251 * trigger the release of kmem magazines, which can callback to
7252 * arc_space_return() which accesses aggsums freed in act_state_fini().
7253 */
7254 buf_fini();
7255 arc_state_fini();
7256
7257 ASSERT0(arc_loaned_bytes);
7258 }
7259
7260 /*
7261 * Level 2 ARC
7262 *
7263 * The level 2 ARC (L2ARC) is a cache layer in-between main memory and disk.
7264 * It uses dedicated storage devices to hold cached data, which are populated
7265 * using large infrequent writes. The main role of this cache is to boost
7266 * the performance of random read workloads. The intended L2ARC devices
7267 * include short-stroked disks, solid state disks, and other media with
7268 * substantially faster read latency than disk.
7269 *
7270 * +-----------------------+
7271 * | ARC |
7272 * +-----------------------+
7273 * | ^ ^
7274 * | | |
7275 * l2arc_feed_thread() arc_read()
7276 * | | |
7277 * | l2arc read |
7278 * V | |
7279 * +---------------+ |
7280 * | L2ARC | |
7281 * +---------------+ |
7282 * | ^ |
7283 * l2arc_write() | |
7284 * | | |
7285 * V | |
7286 * +-------+ +-------+
7287 * | vdev | | vdev |
7288 * | cache | | cache |
7289 * +-------+ +-------+
7290 * +=========+ .-----.
7291 * : L2ARC : |-_____-|
7292 * : devices : | Disks |
7293 * +=========+ `-_____-'
7294 *
7295 * Read requests are satisfied from the following sources, in order:
7296 *
7297 * 1) ARC
7298 * 2) vdev cache of L2ARC devices
7299 * 3) L2ARC devices
7300 * 4) vdev cache of disks
7301 * 5) disks
7302 *
7303 * Some L2ARC device types exhibit extremely slow write performance.
7304 * To accommodate for this there are some significant differences between
7305 * the L2ARC and traditional cache design:
7306 *
7307 * 1. There is no eviction path from the ARC to the L2ARC. Evictions from
7308 * the ARC behave as usual, freeing buffers and placing headers on ghost
7309 * lists. The ARC does not send buffers to the L2ARC during eviction as
7310 * this would add inflated write latencies for all ARC memory pressure.
7311 *
7312 * 2. The L2ARC attempts to cache data from the ARC before it is evicted.
7313 * It does this by periodically scanning buffers from the eviction-end of
7314 * the MFU and MRU ARC lists, copying them to the L2ARC devices if they are
7315 * not already there. It scans until a headroom of buffers is satisfied,
7316 * which itself is a buffer for ARC eviction. If a compressible buffer is
7317 * found during scanning and selected for writing to an L2ARC device, we
7318 * temporarily boost scanning headroom during the next scan cycle to make
7319 * sure we adapt to compression effects (which might significantly reduce
7320 * the data volume we write to L2ARC). The thread that does this is
7321 * l2arc_feed_thread(), illustrated below; example sizes are included to
7322 * provide a better sense of ratio than this diagram:
7323 *
7324 * head --> tail
7325 * +---------------------+----------+
7326 * ARC_mfu |:::::#:::::::::::::::|o#o###o###|-->. # already on L2ARC
7327 * +---------------------+----------+ | o L2ARC eligible
7328 * ARC_mru |:#:::::::::::::::::::|#o#ooo####|-->| : ARC buffer
7329 * +---------------------+----------+ |
7330 * 15.9 Gbytes ^ 32 Mbytes |
7331 * headroom |
7332 * l2arc_feed_thread()
7333 * |
7334 * l2arc write hand <--[oooo]--'
7335 * | 8 Mbyte
7336 * | write max
7337 * V
7338 * +==============================+
7339 * L2ARC dev |####|#|###|###| |####| ... |
7340 * +==============================+
7341 * 32 Gbytes
7342 *
7343 * 3. If an ARC buffer is copied to the L2ARC but then hit instead of
7344 * evicted, then the L2ARC has cached a buffer much sooner than it probably
7345 * needed to, potentially wasting L2ARC device bandwidth and storage. It is
7346 * safe to say that this is an uncommon case, since buffers at the end of
7347 * the ARC lists have moved there due to inactivity.
7348 *
7349 * 4. If the ARC evicts faster than the L2ARC can maintain a headroom,
7350 * then the L2ARC simply misses copying some buffers. This serves as a
7351 * pressure valve to prevent heavy read workloads from both stalling the ARC
7352 * with waits and clogging the L2ARC with writes. This also helps prevent
7353 * the potential for the L2ARC to churn if it attempts to cache content too
7354 * quickly, such as during backups of the entire pool.
7355 *
7356 * 5. After system boot and before the ARC has filled main memory, there are
7357 * no evictions from the ARC and so the tails of the ARC_mfu and ARC_mru
7358 * lists can remain mostly static. Instead of searching from tail of these
7359 * lists as pictured, the l2arc_feed_thread() will search from the list heads
7360 * for eligible buffers, greatly increasing its chance of finding them.
7361 *
7362 * The L2ARC device write speed is also boosted during this time so that
7363 * the L2ARC warms up faster. Since there have been no ARC evictions yet,
7364 * there are no L2ARC reads, and no fear of degrading read performance
7365 * through increased writes.
7366 *
7367 * 6. Writes to the L2ARC devices are grouped and sent in-sequence, so that
7368 * the vdev queue can aggregate them into larger and fewer writes. Each
7369 * device is written to in a rotor fashion, sweeping writes through
7370 * available space then repeating.
7371 *
7372 * 7. The L2ARC does not store dirty content. It never needs to flush
7373 * write buffers back to disk based storage.
7374 *
7375 * 8. If an ARC buffer is written (and dirtied) which also exists in the
7376 * L2ARC, the now stale L2ARC buffer is immediately dropped.
7377 *
7378 * The performance of the L2ARC can be tweaked by a number of tunables, which
7379 * may be necessary for different workloads:
7380 *
7381 * l2arc_write_max max write bytes per interval
7382 * l2arc_write_boost extra write bytes during device warmup
7383 * l2arc_noprefetch skip caching prefetched buffers
7384 * l2arc_headroom number of max device writes to precache
7385 * l2arc_headroom_boost when we find compressed buffers during ARC
7386 * scanning, we multiply headroom by this
7387 * percentage factor for the next scan cycle,
7388 * since more compressed buffers are likely to
7389 * be present
7390 * l2arc_feed_secs seconds between L2ARC writing
7391 *
7392 * Tunables may be removed or added as future performance improvements are
7393 * integrated, and also may become zpool properties.
7394 *
7395 * There are three key functions that control how the L2ARC warms up:
7396 *
7397 * l2arc_write_eligible() check if a buffer is eligible to cache
7398 * l2arc_write_size() calculate how much to write
7399 * l2arc_write_interval() calculate sleep delay between writes
7400 *
7401 * These three functions determine what to write, how much, and how quickly
7402 * to send writes.
7403 *
7404 * L2ARC persistence:
7405 *
7406 * When writing buffers to L2ARC, we periodically add some metadata to
7407 * make sure we can pick them up after reboot, thus dramatically reducing
7408 * the impact that any downtime has on the performance of storage systems
7409 * with large caches.
7410 *
7411 * The implementation works fairly simply by integrating the following two
7412 * modifications:
7413 *
7414 * *) When writing to the L2ARC, we occasionally write a "l2arc log block",
7415 * which is an additional piece of metadata which describes what's been
7416 * written. This allows us to rebuild the arc_buf_hdr_t structures of the
7417 * main ARC buffers. There are 2 linked-lists of log blocks headed by
7418 * dh_start_lbps[2]. We alternate which chain we append to, so they are
7419 * time-wise and offset-wise interleaved, but that is an optimization rather
7420 * than for correctness. The log block also includes a pointer to the
7421 * previous block in its chain.
7422 *
7423 * *) We reserve SPA_MINBLOCKSIZE of space at the start of each L2ARC device
7424 * for our header bookkeeping purposes. This contains a device header,
7425 * which contains our top-level reference structures. We update it each
7426 * time we write a new log block, so that we're able to locate it in the
7427 * L2ARC device. If this write results in an inconsistent device header
7428 * (e.g. due to power failure), we detect this by verifying the header's
7429 * checksum and simply fail to reconstruct the L2ARC after reboot.
7430 *
7431 * Implementation diagram:
7432 *
7433 * +=== L2ARC device (not to scale) ======================================+
7434 * | ___two newest log block pointers__.__________ |
7435 * | / \dh_start_lbps[1] |
7436 * | / \ \dh_start_lbps[0]|
7437 * |.___/__. V V |
7438 * ||L2 dev|....|lb |bufs |lb |bufs |lb |bufs |lb |bufs |lb |---(empty)---|
7439 * || hdr| ^ /^ /^ / / |
7440 * |+------+ ...--\-------/ \-----/--\------/ / |
7441 * | \--------------/ \--------------/ |
7442 * +======================================================================+
7443 *
7444 * As can be seen on the diagram, rather than using a simple linked list,
7445 * we use a pair of linked lists with alternating elements. This is a
7446 * performance enhancement due to the fact that we only find out the
7447 * address of the next log block access once the current block has been
7448 * completely read in. Obviously, this hurts performance, because we'd be
7449 * keeping the device's I/O queue at only a 1 operation deep, thus
7450 * incurring a large amount of I/O round-trip latency. Having two lists
7451 * allows us to fetch two log blocks ahead of where we are currently
7452 * rebuilding L2ARC buffers.
7453 *
7454 * On-device data structures:
7455 *
7456 * L2ARC device header: l2arc_dev_hdr_phys_t
7457 * L2ARC log block: l2arc_log_blk_phys_t
7458 *
7459 * L2ARC reconstruction:
7460 *
7461 * When writing data, we simply write in the standard rotary fashion,
7462 * evicting buffers as we go and simply writing new data over them (writing
7463 * a new log block every now and then). This obviously means that once we
7464 * loop around the end of the device, we will start cutting into an already
7465 * committed log block (and its referenced data buffers), like so:
7466 *
7467 * current write head__ __old tail
7468 * \ /
7469 * V V
7470 * <--|bufs |lb |bufs |lb | |bufs |lb |bufs |lb |-->
7471 * ^ ^^^^^^^^^___________________________________
7472 * | \
7473 * <<nextwrite>> may overwrite this blk and/or its bufs --'
7474 *
7475 * When importing the pool, we detect this situation and use it to stop
7476 * our scanning process (see l2arc_rebuild).
7477 *
7478 * There is one significant caveat to consider when rebuilding ARC contents
7479 * from an L2ARC device: what about invalidated buffers? Given the above
7480 * construction, we cannot update blocks which we've already written to amend
7481 * them to remove buffers which were invalidated. Thus, during reconstruction,
7482 * we might be populating the cache with buffers for data that's not on the
7483 * main pool anymore, or may have been overwritten!
7484 *
7485 * As it turns out, this isn't a problem. Every arc_read request includes
7486 * both the DVA and, crucially, the birth TXG of the BP the caller is
7487 * looking for. So even if the cache were populated by completely rotten
7488 * blocks for data that had been long deleted and/or overwritten, we'll
7489 * never actually return bad data from the cache, since the DVA with the
7490 * birth TXG uniquely identify a block in space and time - once created,
7491 * a block is immutable on disk. The worst thing we have done is wasted
7492 * some time and memory at l2arc rebuild to reconstruct outdated ARC
7493 * entries that will get dropped from the l2arc as it is being updated
7494 * with new blocks.
7495 *
7496 * L2ARC buffers that have been evicted by l2arc_evict() ahead of the write
7497 * hand are not restored. This is done by saving the offset (in bytes)
7498 * l2arc_evict() has evicted to in the L2ARC device header and taking it
7499 * into account when restoring buffers.
7500 */
7501
7502 static boolean_t
l2arc_write_eligible(uint64_t spa_guid,arc_buf_hdr_t * hdr)7503 l2arc_write_eligible(uint64_t spa_guid, arc_buf_hdr_t *hdr)
7504 {
7505 /*
7506 * A buffer is *not* eligible for the L2ARC if it:
7507 * 1. belongs to a different spa.
7508 * 2. is already cached on the L2ARC.
7509 * 3. has an I/O in progress (it may be an incomplete read).
7510 * 4. is flagged not eligible (zfs property).
7511 * 5. is a prefetch and l2arc_noprefetch is set.
7512 */
7513 if (hdr->b_spa != spa_guid || HDR_HAS_L2HDR(hdr) ||
7514 HDR_IO_IN_PROGRESS(hdr) || !HDR_L2CACHE(hdr) ||
7515 (l2arc_noprefetch && HDR_PREFETCH(hdr)))
7516 return (B_FALSE);
7517
7518 return (B_TRUE);
7519 }
7520
7521 static uint64_t
l2arc_write_size(l2arc_dev_t * dev)7522 l2arc_write_size(l2arc_dev_t *dev)
7523 {
7524 uint64_t size, dev_size;
7525
7526 /*
7527 * Make sure our globals have meaningful values in case the user
7528 * altered them.
7529 */
7530 size = l2arc_write_max;
7531 if (size == 0) {
7532 cmn_err(CE_NOTE, "Bad value for l2arc_write_max, value must "
7533 "be greater than zero, resetting it to the default (%d)",
7534 L2ARC_WRITE_SIZE);
7535 size = l2arc_write_max = L2ARC_WRITE_SIZE;
7536 }
7537
7538 if (arc_warm == B_FALSE)
7539 size += l2arc_write_boost;
7540
7541 /*
7542 * Make sure the write size does not exceed the size of the cache
7543 * device. This is important in l2arc_evict(), otherwise infinite
7544 * iteration can occur.
7545 */
7546 dev_size = dev->l2ad_end - dev->l2ad_start;
7547 if ((size + l2arc_log_blk_overhead(size, dev)) >= dev_size) {
7548 cmn_err(CE_NOTE, "l2arc_write_max or l2arc_write_boost "
7549 "plus the overhead of log blocks (persistent L2ARC, "
7550 "%" PRIu64 " bytes) exceeds the size of the cache device "
7551 "(guid %" PRIu64 "), resetting them to the default (%d)",
7552 l2arc_log_blk_overhead(size, dev),
7553 dev->l2ad_vdev->vdev_guid, L2ARC_WRITE_SIZE);
7554 size = l2arc_write_max = l2arc_write_boost = L2ARC_WRITE_SIZE;
7555
7556 if (arc_warm == B_FALSE)
7557 size += l2arc_write_boost;
7558 }
7559
7560 return (size);
7561
7562 }
7563
7564 static clock_t
l2arc_write_interval(clock_t began,uint64_t wanted,uint64_t wrote)7565 l2arc_write_interval(clock_t began, uint64_t wanted, uint64_t wrote)
7566 {
7567 clock_t interval, next, now;
7568
7569 /*
7570 * If the ARC lists are busy, increase our write rate; if the
7571 * lists are stale, idle back. This is achieved by checking
7572 * how much we previously wrote - if it was more than half of
7573 * what we wanted, schedule the next write much sooner.
7574 */
7575 if (l2arc_feed_again && wrote > (wanted / 2))
7576 interval = (hz * l2arc_feed_min_ms) / 1000;
7577 else
7578 interval = hz * l2arc_feed_secs;
7579
7580 now = ddi_get_lbolt();
7581 next = MAX(now, MIN(now + interval, began + interval));
7582
7583 return (next);
7584 }
7585
7586 /*
7587 * Cycle through L2ARC devices. This is how L2ARC load balances.
7588 * If a device is returned, this also returns holding the spa config lock.
7589 */
7590 static l2arc_dev_t *
l2arc_dev_get_next(void)7591 l2arc_dev_get_next(void)
7592 {
7593 l2arc_dev_t *first, *next = NULL;
7594
7595 /*
7596 * Lock out the removal of spas (spa_namespace_lock), then removal
7597 * of cache devices (l2arc_dev_mtx). Once a device has been selected,
7598 * both locks will be dropped and a spa config lock held instead.
7599 */
7600 mutex_enter(&spa_namespace_lock);
7601 mutex_enter(&l2arc_dev_mtx);
7602
7603 /* if there are no vdevs, there is nothing to do */
7604 if (l2arc_ndev == 0)
7605 goto out;
7606
7607 first = NULL;
7608 next = l2arc_dev_last;
7609 do {
7610 /* loop around the list looking for a non-faulted vdev */
7611 if (next == NULL) {
7612 next = list_head(l2arc_dev_list);
7613 } else {
7614 next = list_next(l2arc_dev_list, next);
7615 if (next == NULL)
7616 next = list_head(l2arc_dev_list);
7617 }
7618
7619 /* if we have come back to the start, bail out */
7620 if (first == NULL)
7621 first = next;
7622 else if (next == first)
7623 break;
7624
7625 } while (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild);
7626
7627 /* if we were unable to find any usable vdevs, return NULL */
7628 if (vdev_is_dead(next->l2ad_vdev) || next->l2ad_rebuild)
7629 next = NULL;
7630
7631 l2arc_dev_last = next;
7632
7633 out:
7634 mutex_exit(&l2arc_dev_mtx);
7635
7636 /*
7637 * Grab the config lock to prevent the 'next' device from being
7638 * removed while we are writing to it.
7639 */
7640 if (next != NULL)
7641 spa_config_enter(next->l2ad_spa, SCL_L2ARC, next, RW_READER);
7642 mutex_exit(&spa_namespace_lock);
7643
7644 return (next);
7645 }
7646
7647 /*
7648 * Free buffers that were tagged for destruction.
7649 */
7650 static void
l2arc_do_free_on_write()7651 l2arc_do_free_on_write()
7652 {
7653 list_t *buflist;
7654 l2arc_data_free_t *df, *df_prev;
7655
7656 mutex_enter(&l2arc_free_on_write_mtx);
7657 buflist = l2arc_free_on_write;
7658
7659 for (df = list_tail(buflist); df; df = df_prev) {
7660 df_prev = list_prev(buflist, df);
7661 ASSERT3P(df->l2df_abd, !=, NULL);
7662 abd_free(df->l2df_abd);
7663 list_remove(buflist, df);
7664 kmem_free(df, sizeof (l2arc_data_free_t));
7665 }
7666
7667 mutex_exit(&l2arc_free_on_write_mtx);
7668 }
7669
7670 /*
7671 * A write to a cache device has completed. Update all headers to allow
7672 * reads from these buffers to begin.
7673 */
7674 static void
l2arc_write_done(zio_t * zio)7675 l2arc_write_done(zio_t *zio)
7676 {
7677 l2arc_write_callback_t *cb;
7678 l2arc_lb_abd_buf_t *abd_buf;
7679 l2arc_lb_ptr_buf_t *lb_ptr_buf;
7680 l2arc_dev_t *dev;
7681 l2arc_dev_hdr_phys_t *l2dhdr;
7682 list_t *buflist;
7683 arc_buf_hdr_t *head, *hdr, *hdr_prev;
7684 kmutex_t *hash_lock;
7685 int64_t bytes_dropped = 0;
7686
7687 cb = zio->io_private;
7688 ASSERT3P(cb, !=, NULL);
7689 dev = cb->l2wcb_dev;
7690 l2dhdr = dev->l2ad_dev_hdr;
7691 ASSERT3P(dev, !=, NULL);
7692 head = cb->l2wcb_head;
7693 ASSERT3P(head, !=, NULL);
7694 buflist = &dev->l2ad_buflist;
7695 ASSERT3P(buflist, !=, NULL);
7696 DTRACE_PROBE2(l2arc__iodone, zio_t *, zio,
7697 l2arc_write_callback_t *, cb);
7698
7699 /*
7700 * All writes completed, or an error was hit.
7701 */
7702 top:
7703 mutex_enter(&dev->l2ad_mtx);
7704 for (hdr = list_prev(buflist, head); hdr; hdr = hdr_prev) {
7705 hdr_prev = list_prev(buflist, hdr);
7706
7707 hash_lock = HDR_LOCK(hdr);
7708
7709 /*
7710 * We cannot use mutex_enter or else we can deadlock
7711 * with l2arc_write_buffers (due to swapping the order
7712 * the hash lock and l2ad_mtx are taken).
7713 */
7714 if (!mutex_tryenter(hash_lock)) {
7715 /*
7716 * Missed the hash lock. We must retry so we
7717 * don't leave the ARC_FLAG_L2_WRITING bit set.
7718 */
7719 ARCSTAT_BUMP(arcstat_l2_writes_lock_retry);
7720
7721 /*
7722 * We don't want to rescan the headers we've
7723 * already marked as having been written out, so
7724 * we reinsert the head node so we can pick up
7725 * where we left off.
7726 */
7727 list_remove(buflist, head);
7728 list_insert_after(buflist, hdr, head);
7729
7730 mutex_exit(&dev->l2ad_mtx);
7731
7732 /*
7733 * We wait for the hash lock to become available
7734 * to try and prevent busy waiting, and increase
7735 * the chance we'll be able to acquire the lock
7736 * the next time around.
7737 */
7738 mutex_enter(hash_lock);
7739 mutex_exit(hash_lock);
7740 goto top;
7741 }
7742
7743 /*
7744 * We could not have been moved into the arc_l2c_only
7745 * state while in-flight due to our ARC_FLAG_L2_WRITING
7746 * bit being set. Let's just ensure that's being enforced.
7747 */
7748 ASSERT(HDR_HAS_L1HDR(hdr));
7749
7750 if (zio->io_error != 0) {
7751 /*
7752 * Error - drop L2ARC entry.
7753 */
7754 list_remove(buflist, hdr);
7755 arc_hdr_clear_flags(hdr, ARC_FLAG_HAS_L2HDR);
7756
7757 uint64_t psize = HDR_GET_PSIZE(hdr);
7758 l2arc_hdr_arcstats_decrement(hdr);
7759
7760 bytes_dropped +=
7761 vdev_psize_to_asize(dev->l2ad_vdev, psize);
7762 (void) zfs_refcount_remove_many(&dev->l2ad_alloc,
7763 arc_hdr_size(hdr), hdr);
7764 }
7765
7766 /*
7767 * Allow ARC to begin reads and ghost list evictions to
7768 * this L2ARC entry.
7769 */
7770 arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
7771
7772 mutex_exit(hash_lock);
7773 }
7774
7775 /*
7776 * Free the allocated abd buffers for writing the log blocks.
7777 * If the zio failed reclaim the allocated space and remove the
7778 * pointers to these log blocks from the log block pointer list
7779 * of the L2ARC device.
7780 */
7781 while ((abd_buf = list_remove_tail(&cb->l2wcb_abd_list)) != NULL) {
7782 abd_free(abd_buf->abd);
7783 zio_buf_free(abd_buf, sizeof (*abd_buf));
7784 if (zio->io_error != 0) {
7785 lb_ptr_buf = list_remove_head(&dev->l2ad_lbptr_list);
7786 /*
7787 * L2BLK_GET_PSIZE returns aligned size for log
7788 * blocks.
7789 */
7790 uint64_t asize =
7791 L2BLK_GET_PSIZE((lb_ptr_buf->lb_ptr)->lbp_prop);
7792 bytes_dropped += asize;
7793 ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize);
7794 ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count);
7795 zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize,
7796 lb_ptr_buf);
7797 zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf);
7798 kmem_free(lb_ptr_buf->lb_ptr,
7799 sizeof (l2arc_log_blkptr_t));
7800 kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t));
7801 }
7802 }
7803 list_destroy(&cb->l2wcb_abd_list);
7804
7805 if (zio->io_error != 0) {
7806 ARCSTAT_BUMP(arcstat_l2_writes_error);
7807
7808 /*
7809 * Restore the lbps array in the header to its previous state.
7810 * If the list of log block pointers is empty, zero out the
7811 * log block pointers in the device header.
7812 */
7813 lb_ptr_buf = list_head(&dev->l2ad_lbptr_list);
7814 for (int i = 0; i < 2; i++) {
7815 if (lb_ptr_buf == NULL) {
7816 /*
7817 * If the list is empty zero out the device
7818 * header. Otherwise zero out the second log
7819 * block pointer in the header.
7820 */
7821 if (i == 0) {
7822 bzero(l2dhdr, dev->l2ad_dev_hdr_asize);
7823 } else {
7824 bzero(&l2dhdr->dh_start_lbps[i],
7825 sizeof (l2arc_log_blkptr_t));
7826 }
7827 break;
7828 }
7829 bcopy(lb_ptr_buf->lb_ptr, &l2dhdr->dh_start_lbps[i],
7830 sizeof (l2arc_log_blkptr_t));
7831 lb_ptr_buf = list_next(&dev->l2ad_lbptr_list,
7832 lb_ptr_buf);
7833 }
7834 }
7835
7836 atomic_inc_64(&l2arc_writes_done);
7837 list_remove(buflist, head);
7838 ASSERT(!HDR_HAS_L1HDR(head));
7839 kmem_cache_free(hdr_l2only_cache, head);
7840 mutex_exit(&dev->l2ad_mtx);
7841
7842 ASSERT(dev->l2ad_vdev != NULL);
7843 vdev_space_update(dev->l2ad_vdev, -bytes_dropped, 0, 0);
7844
7845 l2arc_do_free_on_write();
7846
7847 kmem_free(cb, sizeof (l2arc_write_callback_t));
7848 }
7849
7850 static int
l2arc_untransform(zio_t * zio,l2arc_read_callback_t * cb)7851 l2arc_untransform(zio_t *zio, l2arc_read_callback_t *cb)
7852 {
7853 int ret;
7854 spa_t *spa = zio->io_spa;
7855 arc_buf_hdr_t *hdr = cb->l2rcb_hdr;
7856 blkptr_t *bp = zio->io_bp;
7857 uint8_t salt[ZIO_DATA_SALT_LEN];
7858 uint8_t iv[ZIO_DATA_IV_LEN];
7859 uint8_t mac[ZIO_DATA_MAC_LEN];
7860 boolean_t no_crypt = B_FALSE;
7861
7862 /*
7863 * ZIL data is never be written to the L2ARC, so we don't need
7864 * special handling for its unique MAC storage.
7865 */
7866 ASSERT3U(BP_GET_TYPE(bp), !=, DMU_OT_INTENT_LOG);
7867 ASSERT(MUTEX_HELD(HDR_LOCK(hdr)));
7868 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
7869
7870 /*
7871 * If the data was encrypted, decrypt it now. Note that
7872 * we must check the bp here and not the hdr, since the
7873 * hdr does not have its encryption parameters updated
7874 * until arc_read_done().
7875 */
7876 if (BP_IS_ENCRYPTED(bp)) {
7877 abd_t *eabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr,
7878 B_TRUE);
7879
7880 zio_crypt_decode_params_bp(bp, salt, iv);
7881 zio_crypt_decode_mac_bp(bp, mac);
7882
7883 ret = spa_do_crypt_abd(B_FALSE, spa, &cb->l2rcb_zb,
7884 BP_GET_TYPE(bp), BP_GET_DEDUP(bp), BP_SHOULD_BYTESWAP(bp),
7885 salt, iv, mac, HDR_GET_PSIZE(hdr), eabd,
7886 hdr->b_l1hdr.b_pabd, &no_crypt);
7887 if (ret != 0) {
7888 arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
7889 goto error;
7890 }
7891
7892 /*
7893 * If we actually performed decryption, replace b_pabd
7894 * with the decrypted data. Otherwise we can just throw
7895 * our decryption buffer away.
7896 */
7897 if (!no_crypt) {
7898 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
7899 arc_hdr_size(hdr), hdr);
7900 hdr->b_l1hdr.b_pabd = eabd;
7901 zio->io_abd = eabd;
7902 } else {
7903 arc_free_data_abd(hdr, eabd, arc_hdr_size(hdr), hdr);
7904 }
7905 }
7906
7907 /*
7908 * If the L2ARC block was compressed, but ARC compression
7909 * is disabled we decompress the data into a new buffer and
7910 * replace the existing data.
7911 */
7912 if (HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
7913 !HDR_COMPRESSION_ENABLED(hdr)) {
7914 abd_t *cabd = arc_get_data_abd(hdr, arc_hdr_size(hdr), hdr,
7915 B_TRUE);
7916 void *tmp = abd_borrow_buf(cabd, arc_hdr_size(hdr));
7917
7918 ret = zio_decompress_data(HDR_GET_COMPRESS(hdr),
7919 hdr->b_l1hdr.b_pabd, tmp, HDR_GET_PSIZE(hdr),
7920 HDR_GET_LSIZE(hdr));
7921 if (ret != 0) {
7922 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
7923 arc_free_data_abd(hdr, cabd, arc_hdr_size(hdr), hdr);
7924 goto error;
7925 }
7926
7927 abd_return_buf_copy(cabd, tmp, arc_hdr_size(hdr));
7928 arc_free_data_abd(hdr, hdr->b_l1hdr.b_pabd,
7929 arc_hdr_size(hdr), hdr);
7930 hdr->b_l1hdr.b_pabd = cabd;
7931 zio->io_abd = cabd;
7932 zio->io_size = HDR_GET_LSIZE(hdr);
7933 }
7934
7935 return (0);
7936
7937 error:
7938 return (ret);
7939 }
7940
7941
7942 /*
7943 * A read to a cache device completed. Validate buffer contents before
7944 * handing over to the regular ARC routines.
7945 */
7946 static void
l2arc_read_done(zio_t * zio)7947 l2arc_read_done(zio_t *zio)
7948 {
7949 int tfm_error = 0;
7950 l2arc_read_callback_t *cb = zio->io_private;
7951 arc_buf_hdr_t *hdr;
7952 kmutex_t *hash_lock;
7953 boolean_t valid_cksum;
7954 boolean_t using_rdata = (BP_IS_ENCRYPTED(&cb->l2rcb_bp) &&
7955 (cb->l2rcb_flags & ZIO_FLAG_RAW_ENCRYPT));
7956
7957 ASSERT3P(zio->io_vd, !=, NULL);
7958 ASSERT(zio->io_flags & ZIO_FLAG_DONT_PROPAGATE);
7959
7960 spa_config_exit(zio->io_spa, SCL_L2ARC, zio->io_vd);
7961
7962 ASSERT3P(cb, !=, NULL);
7963 hdr = cb->l2rcb_hdr;
7964 ASSERT3P(hdr, !=, NULL);
7965
7966 hash_lock = HDR_LOCK(hdr);
7967 mutex_enter(hash_lock);
7968 ASSERT3P(hash_lock, ==, HDR_LOCK(hdr));
7969
7970 /*
7971 * If the data was read into a temporary buffer,
7972 * move it and free the buffer.
7973 */
7974 if (cb->l2rcb_abd != NULL) {
7975 ASSERT3U(arc_hdr_size(hdr), <, zio->io_size);
7976 if (zio->io_error == 0) {
7977 if (using_rdata) {
7978 abd_copy(hdr->b_crypt_hdr.b_rabd,
7979 cb->l2rcb_abd, arc_hdr_size(hdr));
7980 } else {
7981 abd_copy(hdr->b_l1hdr.b_pabd,
7982 cb->l2rcb_abd, arc_hdr_size(hdr));
7983 }
7984 }
7985
7986 /*
7987 * The following must be done regardless of whether
7988 * there was an error:
7989 * - free the temporary buffer
7990 * - point zio to the real ARC buffer
7991 * - set zio size accordingly
7992 * These are required because zio is either re-used for
7993 * an I/O of the block in the case of the error
7994 * or the zio is passed to arc_read_done() and it
7995 * needs real data.
7996 */
7997 abd_free(cb->l2rcb_abd);
7998 zio->io_size = zio->io_orig_size = arc_hdr_size(hdr);
7999
8000 if (using_rdata) {
8001 ASSERT(HDR_HAS_RABD(hdr));
8002 zio->io_abd = zio->io_orig_abd =
8003 hdr->b_crypt_hdr.b_rabd;
8004 } else {
8005 ASSERT3P(hdr->b_l1hdr.b_pabd, !=, NULL);
8006 zio->io_abd = zio->io_orig_abd = hdr->b_l1hdr.b_pabd;
8007 }
8008 }
8009
8010 ASSERT3P(zio->io_abd, !=, NULL);
8011
8012 /*
8013 * Check this survived the L2ARC journey.
8014 */
8015 ASSERT(zio->io_abd == hdr->b_l1hdr.b_pabd ||
8016 (HDR_HAS_RABD(hdr) && zio->io_abd == hdr->b_crypt_hdr.b_rabd));
8017 zio->io_bp_copy = cb->l2rcb_bp; /* XXX fix in L2ARC 2.0 */
8018 zio->io_bp = &zio->io_bp_copy; /* XXX fix in L2ARC 2.0 */
8019
8020 valid_cksum = arc_cksum_is_equal(hdr, zio);
8021
8022 /*
8023 * b_rabd will always match the data as it exists on disk if it is
8024 * being used. Therefore if we are reading into b_rabd we do not
8025 * attempt to untransform the data.
8026 */
8027 if (valid_cksum && !using_rdata)
8028 tfm_error = l2arc_untransform(zio, cb);
8029
8030 if (valid_cksum && tfm_error == 0 && zio->io_error == 0 &&
8031 !HDR_L2_EVICTED(hdr)) {
8032 mutex_exit(hash_lock);
8033 zio->io_private = hdr;
8034 arc_read_done(zio);
8035 } else {
8036 /*
8037 * Buffer didn't survive caching. Increment stats and
8038 * reissue to the original storage device.
8039 */
8040 if (zio->io_error != 0) {
8041 ARCSTAT_BUMP(arcstat_l2_io_error);
8042 } else {
8043 zio->io_error = SET_ERROR(EIO);
8044 }
8045 if (!valid_cksum || tfm_error != 0)
8046 ARCSTAT_BUMP(arcstat_l2_cksum_bad);
8047
8048 /*
8049 * If there's no waiter, issue an async i/o to the primary
8050 * storage now. If there *is* a waiter, the caller must
8051 * issue the i/o in a context where it's OK to block.
8052 */
8053 if (zio->io_waiter == NULL) {
8054 zio_t *pio = zio_unique_parent(zio);
8055 void *abd = (using_rdata) ?
8056 hdr->b_crypt_hdr.b_rabd : hdr->b_l1hdr.b_pabd;
8057
8058 ASSERT(!pio || pio->io_child_type == ZIO_CHILD_LOGICAL);
8059
8060 zio = zio_read(pio, zio->io_spa, zio->io_bp,
8061 abd, zio->io_size, arc_read_done,
8062 hdr, zio->io_priority, cb->l2rcb_flags,
8063 &cb->l2rcb_zb);
8064
8065 /*
8066 * Original ZIO will be freed, so we need to update
8067 * ARC header with the new ZIO pointer to be used
8068 * by zio_change_priority() in arc_read().
8069 */
8070 for (struct arc_callback *acb = hdr->b_l1hdr.b_acb;
8071 acb != NULL; acb = acb->acb_next)
8072 acb->acb_zio_head = zio;
8073
8074 mutex_exit(hash_lock);
8075 zio_nowait(zio);
8076 } else {
8077 mutex_exit(hash_lock);
8078 }
8079 }
8080
8081 kmem_free(cb, sizeof (l2arc_read_callback_t));
8082 }
8083
8084 /*
8085 * This is the list priority from which the L2ARC will search for pages to
8086 * cache. This is used within loops (0..3) to cycle through lists in the
8087 * desired order. This order can have a significant effect on cache
8088 * performance.
8089 *
8090 * Currently the metadata lists are hit first, MFU then MRU, followed by
8091 * the data lists. This function returns a locked list, and also returns
8092 * the lock pointer.
8093 */
8094 static multilist_sublist_t *
l2arc_sublist_lock(int list_num)8095 l2arc_sublist_lock(int list_num)
8096 {
8097 multilist_t *ml = NULL;
8098 unsigned int idx;
8099
8100 ASSERT(list_num >= 0 && list_num < L2ARC_FEED_TYPES);
8101
8102 switch (list_num) {
8103 case 0:
8104 ml = arc_mfu->arcs_list[ARC_BUFC_METADATA];
8105 break;
8106 case 1:
8107 ml = arc_mru->arcs_list[ARC_BUFC_METADATA];
8108 break;
8109 case 2:
8110 ml = arc_mfu->arcs_list[ARC_BUFC_DATA];
8111 break;
8112 case 3:
8113 ml = arc_mru->arcs_list[ARC_BUFC_DATA];
8114 break;
8115 default:
8116 return (NULL);
8117 }
8118
8119 /*
8120 * Return a randomly-selected sublist. This is acceptable
8121 * because the caller feeds only a little bit of data for each
8122 * call (8MB). Subsequent calls will result in different
8123 * sublists being selected.
8124 */
8125 idx = multilist_get_random_index(ml);
8126 return (multilist_sublist_lock(ml, idx));
8127 }
8128
8129 /*
8130 * Calculates the maximum overhead of L2ARC metadata log blocks for a given
8131 * L2ARC write size. l2arc_evict and l2arc_write_size need to include this
8132 * overhead in processing to make sure there is enough headroom available
8133 * when writing buffers.
8134 */
8135 static inline uint64_t
l2arc_log_blk_overhead(uint64_t write_sz,l2arc_dev_t * dev)8136 l2arc_log_blk_overhead(uint64_t write_sz, l2arc_dev_t *dev)
8137 {
8138 if (dev->l2ad_log_entries == 0) {
8139 return (0);
8140 } else {
8141 uint64_t log_entries = write_sz >> SPA_MINBLOCKSHIFT;
8142
8143 uint64_t log_blocks = (log_entries +
8144 dev->l2ad_log_entries - 1) /
8145 dev->l2ad_log_entries;
8146
8147 return (vdev_psize_to_asize(dev->l2ad_vdev,
8148 sizeof (l2arc_log_blk_phys_t)) * log_blocks);
8149 }
8150 }
8151
8152 /*
8153 * Evict buffers from the device write hand to the distance specified in
8154 * bytes. This distance may span populated buffers, it may span nothing.
8155 * This is clearing a region on the L2ARC device ready for writing.
8156 * If the 'all' boolean is set, every buffer is evicted.
8157 */
8158 static void
l2arc_evict(l2arc_dev_t * dev,uint64_t distance,boolean_t all)8159 l2arc_evict(l2arc_dev_t *dev, uint64_t distance, boolean_t all)
8160 {
8161 list_t *buflist;
8162 arc_buf_hdr_t *hdr, *hdr_prev;
8163 kmutex_t *hash_lock;
8164 uint64_t taddr;
8165 l2arc_lb_ptr_buf_t *lb_ptr_buf, *lb_ptr_buf_prev;
8166 boolean_t rerun;
8167
8168 buflist = &dev->l2ad_buflist;
8169
8170 /*
8171 * We need to add in the worst case scenario of log block overhead.
8172 */
8173 distance += l2arc_log_blk_overhead(distance, dev);
8174
8175 top:
8176 rerun = B_FALSE;
8177 if (dev->l2ad_hand >= (dev->l2ad_end - distance)) {
8178 /*
8179 * When there is no space to accommodate upcoming writes,
8180 * evict to the end. Then bump the write and evict hands
8181 * to the start and iterate. This iteration does not
8182 * happen indefinitely as we make sure in
8183 * l2arc_write_size() that when the write hand is reset,
8184 * the write size does not exceed the end of the device.
8185 */
8186 rerun = B_TRUE;
8187 taddr = dev->l2ad_end;
8188 } else {
8189 taddr = dev->l2ad_hand + distance;
8190 }
8191 DTRACE_PROBE4(l2arc__evict, l2arc_dev_t *, dev, list_t *, buflist,
8192 uint64_t, taddr, boolean_t, all);
8193
8194 /*
8195 * This check has to be placed after deciding whether to iterate
8196 * (rerun).
8197 */
8198 if (!all && dev->l2ad_first) {
8199 /*
8200 * This is the first sweep through the device. There is
8201 * nothing to evict.
8202 */
8203 goto out;
8204 }
8205
8206 /*
8207 * When rebuilding L2ARC we retrieve the evict hand from the header of
8208 * the device. Of note, l2arc_evict() does not actually delete buffers
8209 * from the cache device, but keeping track of the evict hand will be
8210 * useful when TRIM is implemented.
8211 */
8212 dev->l2ad_evict = MAX(dev->l2ad_evict, taddr);
8213
8214 retry:
8215 mutex_enter(&dev->l2ad_mtx);
8216 /*
8217 * We have to account for evicted log blocks. Run vdev_space_update()
8218 * on log blocks whose offset (in bytes) is before the evicted offset
8219 * (in bytes) by searching in the list of pointers to log blocks
8220 * present in the L2ARC device.
8221 */
8222 for (lb_ptr_buf = list_tail(&dev->l2ad_lbptr_list); lb_ptr_buf;
8223 lb_ptr_buf = lb_ptr_buf_prev) {
8224
8225 lb_ptr_buf_prev = list_prev(&dev->l2ad_lbptr_list, lb_ptr_buf);
8226
8227 /* L2BLK_GET_PSIZE returns aligned size for log blocks */
8228 uint64_t asize = L2BLK_GET_PSIZE(
8229 (lb_ptr_buf->lb_ptr)->lbp_prop);
8230
8231 /*
8232 * We don't worry about log blocks left behind (ie
8233 * lbp_payload_start < l2ad_hand) because l2arc_write_buffers()
8234 * will never write more than l2arc_evict() evicts.
8235 */
8236 if (!all && l2arc_log_blkptr_valid(dev, lb_ptr_buf->lb_ptr)) {
8237 break;
8238 } else {
8239 vdev_space_update(dev->l2ad_vdev, -asize, 0, 0);
8240 ARCSTAT_INCR(arcstat_l2_log_blk_asize, -asize);
8241 ARCSTAT_BUMPDOWN(arcstat_l2_log_blk_count);
8242 zfs_refcount_remove_many(&dev->l2ad_lb_asize, asize,
8243 lb_ptr_buf);
8244 zfs_refcount_remove(&dev->l2ad_lb_count, lb_ptr_buf);
8245 list_remove(&dev->l2ad_lbptr_list, lb_ptr_buf);
8246 kmem_free(lb_ptr_buf->lb_ptr,
8247 sizeof (l2arc_log_blkptr_t));
8248 kmem_free(lb_ptr_buf, sizeof (l2arc_lb_ptr_buf_t));
8249 }
8250 }
8251
8252 for (hdr = list_tail(buflist); hdr; hdr = hdr_prev) {
8253 hdr_prev = list_prev(buflist, hdr);
8254
8255 ASSERT(!HDR_EMPTY(hdr));
8256 hash_lock = HDR_LOCK(hdr);
8257
8258 /*
8259 * We cannot use mutex_enter or else we can deadlock
8260 * with l2arc_write_buffers (due to swapping the order
8261 * the hash lock and l2ad_mtx are taken).
8262 */
8263 if (!mutex_tryenter(hash_lock)) {
8264 /*
8265 * Missed the hash lock. Retry.
8266 */
8267 ARCSTAT_BUMP(arcstat_l2_evict_lock_retry);
8268 mutex_exit(&dev->l2ad_mtx);
8269 mutex_enter(hash_lock);
8270 mutex_exit(hash_lock);
8271 goto retry;
8272 }
8273
8274 /*
8275 * A header can't be on this list if it doesn't have L2 header.
8276 */
8277 ASSERT(HDR_HAS_L2HDR(hdr));
8278
8279 /* Ensure this header has finished being written. */
8280 ASSERT(!HDR_L2_WRITING(hdr));
8281 ASSERT(!HDR_L2_WRITE_HEAD(hdr));
8282
8283 if (!all && (hdr->b_l2hdr.b_daddr >= dev->l2ad_evict ||
8284 hdr->b_l2hdr.b_daddr < dev->l2ad_hand)) {
8285 /*
8286 * We've evicted to the target address,
8287 * or the end of the device.
8288 */
8289 mutex_exit(hash_lock);
8290 break;
8291 }
8292
8293 if (!HDR_HAS_L1HDR(hdr)) {
8294 ASSERT(!HDR_L2_READING(hdr));
8295 /*
8296 * This doesn't exist in the ARC. Destroy.
8297 * arc_hdr_destroy() will call list_remove()
8298 * and decrement arcstat_l2_lsize.
8299 */
8300 arc_change_state(arc_anon, hdr, hash_lock);
8301 arc_hdr_destroy(hdr);
8302 } else {
8303 ASSERT(hdr->b_l1hdr.b_state != arc_l2c_only);
8304 ARCSTAT_BUMP(arcstat_l2_evict_l1cached);
8305 /*
8306 * Invalidate issued or about to be issued
8307 * reads, since we may be about to write
8308 * over this location.
8309 */
8310 if (HDR_L2_READING(hdr)) {
8311 ARCSTAT_BUMP(arcstat_l2_evict_reading);
8312 arc_hdr_set_flags(hdr, ARC_FLAG_L2_EVICTED);
8313 }
8314
8315 arc_hdr_l2hdr_destroy(hdr);
8316 }
8317 mutex_exit(hash_lock);
8318 }
8319 mutex_exit(&dev->l2ad_mtx);
8320
8321 out:
8322 /*
8323 * We need to check if we evict all buffers, otherwise we may iterate
8324 * unnecessarily.
8325 */
8326 if (!all && rerun) {
8327 /*
8328 * Bump device hand to the device start if it is approaching the
8329 * end. l2arc_evict() has already evicted ahead for this case.
8330 */
8331 dev->l2ad_hand = dev->l2ad_start;
8332 dev->l2ad_evict = dev->l2ad_start;
8333 dev->l2ad_first = B_FALSE;
8334 goto top;
8335 }
8336
8337 ASSERT3U(dev->l2ad_hand + distance, <, dev->l2ad_end);
8338 if (!dev->l2ad_first)
8339 ASSERT3U(dev->l2ad_hand, <, dev->l2ad_evict);
8340 }
8341
8342 /*
8343 * Handle any abd transforms that might be required for writing to the L2ARC.
8344 * If successful, this function will always return an abd with the data
8345 * transformed as it is on disk in a new abd of asize bytes.
8346 */
8347 static int
l2arc_apply_transforms(spa_t * spa,arc_buf_hdr_t * hdr,uint64_t asize,abd_t ** abd_out)8348 l2arc_apply_transforms(spa_t *spa, arc_buf_hdr_t *hdr, uint64_t asize,
8349 abd_t **abd_out)
8350 {
8351 int ret;
8352 void *tmp = NULL;
8353 abd_t *cabd = NULL, *eabd = NULL, *to_write = hdr->b_l1hdr.b_pabd;
8354 enum zio_compress compress = HDR_GET_COMPRESS(hdr);
8355 uint64_t psize = HDR_GET_PSIZE(hdr);
8356 uint64_t size = arc_hdr_size(hdr);
8357 boolean_t ismd = HDR_ISTYPE_METADATA(hdr);
8358 boolean_t bswap = (hdr->b_l1hdr.b_byteswap != DMU_BSWAP_NUMFUNCS);
8359 dsl_crypto_key_t *dck = NULL;
8360 uint8_t mac[ZIO_DATA_MAC_LEN] = { 0 };
8361 boolean_t no_crypt = B_FALSE;
8362
8363 ASSERT((HDR_GET_COMPRESS(hdr) != ZIO_COMPRESS_OFF &&
8364 !HDR_COMPRESSION_ENABLED(hdr)) ||
8365 HDR_ENCRYPTED(hdr) || HDR_SHARED_DATA(hdr) || psize != asize);
8366 ASSERT3U(psize, <=, asize);
8367
8368 /*
8369 * If this data simply needs its own buffer, we simply allocate it
8370 * and copy the data. This may be done to eliminate a dependency on a
8371 * shared buffer or to reallocate the buffer to match asize.
8372 */
8373 if (HDR_HAS_RABD(hdr) && asize != psize) {
8374 ASSERT3U(asize, >=, psize);
8375 to_write = abd_alloc_for_io(asize, ismd);
8376 abd_copy(to_write, hdr->b_crypt_hdr.b_rabd, psize);
8377 if (psize != asize)
8378 abd_zero_off(to_write, psize, asize - psize);
8379 goto out;
8380 }
8381
8382 if ((compress == ZIO_COMPRESS_OFF || HDR_COMPRESSION_ENABLED(hdr)) &&
8383 !HDR_ENCRYPTED(hdr)) {
8384 ASSERT3U(size, ==, psize);
8385 to_write = abd_alloc_for_io(asize, ismd);
8386 abd_copy(to_write, hdr->b_l1hdr.b_pabd, size);
8387 if (size != asize)
8388 abd_zero_off(to_write, size, asize - size);
8389 goto out;
8390 }
8391
8392 if (compress != ZIO_COMPRESS_OFF && !HDR_COMPRESSION_ENABLED(hdr)) {
8393 cabd = abd_alloc_for_io(asize, ismd);
8394 tmp = abd_borrow_buf(cabd, asize);
8395
8396 psize = zio_compress_data(compress, to_write, tmp, size);
8397 ASSERT3U(psize, <=, HDR_GET_PSIZE(hdr));
8398 if (psize < asize)
8399 bzero((char *)tmp + psize, asize - psize);
8400 psize = HDR_GET_PSIZE(hdr);
8401 abd_return_buf_copy(cabd, tmp, asize);
8402 to_write = cabd;
8403 }
8404
8405 if (HDR_ENCRYPTED(hdr)) {
8406 eabd = abd_alloc_for_io(asize, ismd);
8407
8408 /*
8409 * If the dataset was disowned before the buffer
8410 * made it to this point, the key to re-encrypt
8411 * it won't be available. In this case we simply
8412 * won't write the buffer to the L2ARC.
8413 */
8414 ret = spa_keystore_lookup_key(spa, hdr->b_crypt_hdr.b_dsobj,
8415 FTAG, &dck);
8416 if (ret != 0)
8417 goto error;
8418
8419 ret = zio_do_crypt_abd(B_TRUE, &dck->dck_key,
8420 hdr->b_crypt_hdr.b_ot, bswap, hdr->b_crypt_hdr.b_salt,
8421 hdr->b_crypt_hdr.b_iv, mac, psize, to_write, eabd,
8422 &no_crypt);
8423 if (ret != 0)
8424 goto error;
8425
8426 if (no_crypt)
8427 abd_copy(eabd, to_write, psize);
8428
8429 if (psize != asize)
8430 abd_zero_off(eabd, psize, asize - psize);
8431
8432 /* assert that the MAC we got here matches the one we saved */
8433 ASSERT0(bcmp(mac, hdr->b_crypt_hdr.b_mac, ZIO_DATA_MAC_LEN));
8434 spa_keystore_dsl_key_rele(spa, dck, FTAG);
8435
8436 if (to_write == cabd)
8437 abd_free(cabd);
8438
8439 to_write = eabd;
8440 }
8441
8442 out:
8443 ASSERT3P(to_write, !=, hdr->b_l1hdr.b_pabd);
8444 *abd_out = to_write;
8445 return (0);
8446
8447 error:
8448 if (dck != NULL)
8449 spa_keystore_dsl_key_rele(spa, dck, FTAG);
8450 if (cabd != NULL)
8451 abd_free(cabd);
8452 if (eabd != NULL)
8453 abd_free(eabd);
8454
8455 *abd_out = NULL;
8456 return (ret);
8457 }
8458
8459 static void
l2arc_blk_fetch_done(zio_t * zio)8460 l2arc_blk_fetch_done(zio_t *zio)
8461 {
8462 l2arc_read_callback_t *cb;
8463
8464 cb = zio->io_private;
8465 if (cb->l2rcb_abd != NULL)
8466 abd_put(cb->l2rcb_abd);
8467 kmem_free(cb, sizeof (l2arc_read_callback_t));
8468 }
8469
8470 /*
8471 * Find and write ARC buffers to the L2ARC device.
8472 *
8473 * An ARC_FLAG_L2_WRITING flag is set so that the L2ARC buffers are not valid
8474 * for reading until they have completed writing.
8475 * The headroom_boost is an in-out parameter used to maintain headroom boost
8476 * state between calls to this function.
8477 *
8478 * Returns the number of bytes actually written (which may be smaller than
8479 * the delta by which the device hand has changed due to alignment and the
8480 * writing of log blocks).
8481 */
8482 static uint64_t
l2arc_write_buffers(spa_t * spa,l2arc_dev_t * dev,uint64_t target_sz)8483 l2arc_write_buffers(spa_t *spa, l2arc_dev_t *dev, uint64_t target_sz)
8484 {
8485 arc_buf_hdr_t *hdr, *hdr_prev, *head;
8486 uint64_t write_asize, write_psize, write_lsize, headroom;
8487 boolean_t full;
8488 l2arc_write_callback_t *cb = NULL;
8489 zio_t *pio, *wzio;
8490 uint64_t guid = spa_load_guid(spa);
8491 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
8492
8493 ASSERT3P(dev->l2ad_vdev, !=, NULL);
8494
8495 pio = NULL;
8496 write_lsize = write_asize = write_psize = 0;
8497 full = B_FALSE;
8498 head = kmem_cache_alloc(hdr_l2only_cache, KM_PUSHPAGE);
8499 arc_hdr_set_flags(head, ARC_FLAG_L2_WRITE_HEAD | ARC_FLAG_HAS_L2HDR);
8500
8501 /*
8502 * Copy buffers for L2ARC writing.
8503 */
8504 for (int try = 0; try < L2ARC_FEED_TYPES; try++) {
8505 /*
8506 * If try == 1 or 3, we cache MRU metadata and data
8507 * respectively.
8508 */
8509 if (l2arc_mfuonly) {
8510 if (try == 1 || try == 3)
8511 continue;
8512 }
8513
8514 multilist_sublist_t *mls = l2arc_sublist_lock(try);
8515 uint64_t passed_sz = 0;
8516
8517 VERIFY3P(mls, !=, NULL);
8518
8519 /*
8520 * L2ARC fast warmup.
8521 *
8522 * Until the ARC is warm and starts to evict, read from the
8523 * head of the ARC lists rather than the tail.
8524 */
8525 if (arc_warm == B_FALSE)
8526 hdr = multilist_sublist_head(mls);
8527 else
8528 hdr = multilist_sublist_tail(mls);
8529
8530 headroom = target_sz * l2arc_headroom;
8531 if (zfs_compressed_arc_enabled)
8532 headroom = (headroom * l2arc_headroom_boost) / 100;
8533
8534 for (; hdr; hdr = hdr_prev) {
8535 kmutex_t *hash_lock;
8536 abd_t *to_write = NULL;
8537
8538 if (arc_warm == B_FALSE)
8539 hdr_prev = multilist_sublist_next(mls, hdr);
8540 else
8541 hdr_prev = multilist_sublist_prev(mls, hdr);
8542
8543 hash_lock = HDR_LOCK(hdr);
8544 if (!mutex_tryenter(hash_lock)) {
8545 /*
8546 * Skip this buffer rather than waiting.
8547 */
8548 continue;
8549 }
8550
8551 passed_sz += HDR_GET_LSIZE(hdr);
8552 if (l2arc_headroom != 0 && passed_sz > headroom) {
8553 /*
8554 * Searched too far.
8555 */
8556 mutex_exit(hash_lock);
8557 break;
8558 }
8559
8560 if (!l2arc_write_eligible(guid, hdr)) {
8561 mutex_exit(hash_lock);
8562 continue;
8563 }
8564
8565 ASSERT(HDR_HAS_L1HDR(hdr));
8566
8567 ASSERT3U(HDR_GET_PSIZE(hdr), >, 0);
8568 ASSERT3U(arc_hdr_size(hdr), >, 0);
8569 ASSERT(hdr->b_l1hdr.b_pabd != NULL ||
8570 HDR_HAS_RABD(hdr));
8571 uint64_t psize = HDR_GET_PSIZE(hdr);
8572 uint64_t asize = vdev_psize_to_asize(dev->l2ad_vdev,
8573 psize);
8574
8575 if ((write_asize + asize) > target_sz) {
8576 full = B_TRUE;
8577 mutex_exit(hash_lock);
8578 break;
8579 }
8580
8581 /*
8582 * We rely on the L1 portion of the header below, so
8583 * it's invalid for this header to have been evicted out
8584 * of the ghost cache, prior to being written out. The
8585 * ARC_FLAG_L2_WRITING bit ensures this won't happen.
8586 */
8587 arc_hdr_set_flags(hdr, ARC_FLAG_L2_WRITING);
8588
8589 /*
8590 * If this header has b_rabd, we can use this since it
8591 * must always match the data exactly as it exists on
8592 * disk. Otherwise, the L2ARC can normally use the
8593 * hdr's data, but if we're sharing data between the
8594 * hdr and one of its bufs, L2ARC needs its own copy of
8595 * the data so that the ZIO below can't race with the
8596 * buf consumer. To ensure that this copy will be
8597 * available for the lifetime of the ZIO and be cleaned
8598 * up afterwards, we add it to the l2arc_free_on_write
8599 * queue. If we need to apply any transforms to the
8600 * data (compression, encryption) we will also need the
8601 * extra buffer.
8602 */
8603 if (HDR_HAS_RABD(hdr) && psize == asize) {
8604 to_write = hdr->b_crypt_hdr.b_rabd;
8605 } else if ((HDR_COMPRESSION_ENABLED(hdr) ||
8606 HDR_GET_COMPRESS(hdr) == ZIO_COMPRESS_OFF) &&
8607 !HDR_ENCRYPTED(hdr) && !HDR_SHARED_DATA(hdr) &&
8608 psize == asize) {
8609 to_write = hdr->b_l1hdr.b_pabd;
8610 } else {
8611 int ret;
8612 arc_buf_contents_t type = arc_buf_type(hdr);
8613
8614 ret = l2arc_apply_transforms(spa, hdr, asize,
8615 &to_write);
8616 if (ret != 0) {
8617 arc_hdr_clear_flags(hdr,
8618 ARC_FLAG_L2_WRITING);
8619 mutex_exit(hash_lock);
8620 continue;
8621 }
8622
8623 l2arc_free_abd_on_write(to_write, asize, type);
8624 }
8625
8626 if (pio == NULL) {
8627 /*
8628 * Insert a dummy header on the buflist so
8629 * l2arc_write_done() can find where the
8630 * write buffers begin without searching.
8631 */
8632 mutex_enter(&dev->l2ad_mtx);
8633 list_insert_head(&dev->l2ad_buflist, head);
8634 mutex_exit(&dev->l2ad_mtx);
8635
8636 cb = kmem_alloc(
8637 sizeof (l2arc_write_callback_t), KM_SLEEP);
8638 cb->l2wcb_dev = dev;
8639 cb->l2wcb_head = head;
8640 /*
8641 * Create a list to save allocated abd buffers
8642 * for l2arc_log_blk_commit().
8643 */
8644 list_create(&cb->l2wcb_abd_list,
8645 sizeof (l2arc_lb_abd_buf_t),
8646 offsetof(l2arc_lb_abd_buf_t, node));
8647 pio = zio_root(spa, l2arc_write_done, cb,
8648 ZIO_FLAG_CANFAIL);
8649 }
8650
8651 hdr->b_l2hdr.b_dev = dev;
8652 hdr->b_l2hdr.b_daddr = dev->l2ad_hand;
8653 hdr->b_l2hdr.b_arcs_state =
8654 hdr->b_l1hdr.b_state->arcs_state;
8655 arc_hdr_set_flags(hdr,
8656 ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);
8657
8658 mutex_enter(&dev->l2ad_mtx);
8659 list_insert_head(&dev->l2ad_buflist, hdr);
8660 mutex_exit(&dev->l2ad_mtx);
8661
8662 (void) zfs_refcount_add_many(&dev->l2ad_alloc,
8663 arc_hdr_size(hdr), hdr);
8664
8665 wzio = zio_write_phys(pio, dev->l2ad_vdev,
8666 hdr->b_l2hdr.b_daddr, asize, to_write,
8667 ZIO_CHECKSUM_OFF, NULL, hdr,
8668 ZIO_PRIORITY_ASYNC_WRITE,
8669 ZIO_FLAG_CANFAIL, B_FALSE);
8670
8671 write_lsize += HDR_GET_LSIZE(hdr);
8672 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev,
8673 zio_t *, wzio);
8674
8675 write_psize += psize;
8676 write_asize += asize;
8677 dev->l2ad_hand += asize;
8678 l2arc_hdr_arcstats_increment(hdr);
8679 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
8680
8681 mutex_exit(hash_lock);
8682
8683 /*
8684 * Append buf info to current log and commit if full.
8685 * arcstat_l2_{size,asize} kstats are updated
8686 * internally.
8687 */
8688 if (l2arc_log_blk_insert(dev, hdr))
8689 l2arc_log_blk_commit(dev, pio, cb);
8690
8691 (void) zio_nowait(wzio);
8692 }
8693
8694 multilist_sublist_unlock(mls);
8695
8696 if (full == B_TRUE)
8697 break;
8698 }
8699
8700 /* No buffers selected for writing? */
8701 if (pio == NULL) {
8702 ASSERT0(write_lsize);
8703 ASSERT(!HDR_HAS_L1HDR(head));
8704 kmem_cache_free(hdr_l2only_cache, head);
8705
8706 /*
8707 * Although we did not write any buffers l2ad_evict may
8708 * have advanced.
8709 */
8710 if (dev->l2ad_evict != l2dhdr->dh_evict)
8711 l2arc_dev_hdr_update(dev);
8712
8713 return (0);
8714 }
8715
8716 if (!dev->l2ad_first)
8717 ASSERT3U(dev->l2ad_hand, <=, dev->l2ad_evict);
8718
8719 ASSERT3U(write_asize, <=, target_sz);
8720 ARCSTAT_BUMP(arcstat_l2_writes_sent);
8721 ARCSTAT_INCR(arcstat_l2_write_bytes, write_psize);
8722
8723 dev->l2ad_writing = B_TRUE;
8724 (void) zio_wait(pio);
8725 dev->l2ad_writing = B_FALSE;
8726
8727 /*
8728 * Update the device header after the zio completes as
8729 * l2arc_write_done() may have updated the memory holding the log block
8730 * pointers in the device header.
8731 */
8732 l2arc_dev_hdr_update(dev);
8733
8734 return (write_asize);
8735 }
8736
8737 static boolean_t
l2arc_hdr_limit_reached(void)8738 l2arc_hdr_limit_reached(void)
8739 {
8740 int64_t s = aggsum_upper_bound(&astat_l2_hdr_size);
8741
8742 return (arc_reclaim_needed() || (s > arc_meta_limit * 3 / 4) ||
8743 (s > (arc_warm ? arc_c : arc_c_max) * l2arc_meta_percent / 100));
8744 }
8745
8746 /*
8747 * This thread feeds the L2ARC at regular intervals. This is the beating
8748 * heart of the L2ARC.
8749 */
8750 /* ARGSUSED */
8751 static void
l2arc_feed_thread(void * unused)8752 l2arc_feed_thread(void *unused)
8753 {
8754 callb_cpr_t cpr;
8755 l2arc_dev_t *dev;
8756 spa_t *spa;
8757 uint64_t size, wrote;
8758 clock_t begin, next = ddi_get_lbolt();
8759
8760 CALLB_CPR_INIT(&cpr, &l2arc_feed_thr_lock, callb_generic_cpr, FTAG);
8761
8762 mutex_enter(&l2arc_feed_thr_lock);
8763
8764 while (l2arc_thread_exit == 0) {
8765 CALLB_CPR_SAFE_BEGIN(&cpr);
8766 (void) cv_timedwait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock,
8767 next);
8768 CALLB_CPR_SAFE_END(&cpr, &l2arc_feed_thr_lock);
8769 next = ddi_get_lbolt() + hz;
8770
8771 /*
8772 * Quick check for L2ARC devices.
8773 */
8774 mutex_enter(&l2arc_dev_mtx);
8775 if (l2arc_ndev == 0) {
8776 mutex_exit(&l2arc_dev_mtx);
8777 continue;
8778 }
8779 mutex_exit(&l2arc_dev_mtx);
8780 begin = ddi_get_lbolt();
8781
8782 /*
8783 * This selects the next l2arc device to write to, and in
8784 * doing so the next spa to feed from: dev->l2ad_spa. This
8785 * will return NULL if there are now no l2arc devices or if
8786 * they are all faulted.
8787 *
8788 * If a device is returned, its spa's config lock is also
8789 * held to prevent device removal. l2arc_dev_get_next()
8790 * will grab and release l2arc_dev_mtx.
8791 */
8792 if ((dev = l2arc_dev_get_next()) == NULL)
8793 continue;
8794
8795 spa = dev->l2ad_spa;
8796 ASSERT3P(spa, !=, NULL);
8797
8798 /*
8799 * If the pool is read-only then force the feed thread to
8800 * sleep a little longer.
8801 */
8802 if (!spa_writeable(spa)) {
8803 next = ddi_get_lbolt() + 5 * l2arc_feed_secs * hz;
8804 spa_config_exit(spa, SCL_L2ARC, dev);
8805 continue;
8806 }
8807
8808 /*
8809 * Avoid contributing to memory pressure.
8810 */
8811 if (l2arc_hdr_limit_reached()) {
8812 ARCSTAT_BUMP(arcstat_l2_abort_lowmem);
8813 spa_config_exit(spa, SCL_L2ARC, dev);
8814 continue;
8815 }
8816
8817 ARCSTAT_BUMP(arcstat_l2_feeds);
8818
8819 size = l2arc_write_size(dev);
8820
8821 /*
8822 * Evict L2ARC buffers that will be overwritten.
8823 */
8824 l2arc_evict(dev, size, B_FALSE);
8825
8826 /*
8827 * Write ARC buffers.
8828 */
8829 wrote = l2arc_write_buffers(spa, dev, size);
8830
8831 /*
8832 * Calculate interval between writes.
8833 */
8834 next = l2arc_write_interval(begin, size, wrote);
8835 spa_config_exit(spa, SCL_L2ARC, dev);
8836 }
8837
8838 l2arc_thread_exit = 0;
8839 cv_broadcast(&l2arc_feed_thr_cv);
8840 CALLB_CPR_EXIT(&cpr); /* drops l2arc_feed_thr_lock */
8841 thread_exit();
8842 }
8843
8844 boolean_t
l2arc_vdev_present(vdev_t * vd)8845 l2arc_vdev_present(vdev_t *vd)
8846 {
8847 return (l2arc_vdev_get(vd) != NULL);
8848 }
8849
8850 /*
8851 * Returns the l2arc_dev_t associated with a particular vdev_t or NULL if
8852 * the vdev_t isn't an L2ARC device.
8853 */
8854 static l2arc_dev_t *
l2arc_vdev_get(vdev_t * vd)8855 l2arc_vdev_get(vdev_t *vd)
8856 {
8857 l2arc_dev_t *dev;
8858
8859 mutex_enter(&l2arc_dev_mtx);
8860 for (dev = list_head(l2arc_dev_list); dev != NULL;
8861 dev = list_next(l2arc_dev_list, dev)) {
8862 if (dev->l2ad_vdev == vd)
8863 break;
8864 }
8865 mutex_exit(&l2arc_dev_mtx);
8866
8867 return (dev);
8868 }
8869
8870 /*
8871 * Add a vdev for use by the L2ARC. By this point the spa has already
8872 * validated the vdev and opened it.
8873 */
8874 void
l2arc_add_vdev(spa_t * spa,vdev_t * vd)8875 l2arc_add_vdev(spa_t *spa, vdev_t *vd)
8876 {
8877 l2arc_dev_t *adddev;
8878 uint64_t l2dhdr_asize;
8879
8880 ASSERT(!l2arc_vdev_present(vd));
8881
8882 /*
8883 * Create a new l2arc device entry.
8884 */
8885 adddev = kmem_zalloc(sizeof (l2arc_dev_t), KM_SLEEP);
8886 adddev->l2ad_spa = spa;
8887 adddev->l2ad_vdev = vd;
8888 /* leave extra size for an l2arc device header */
8889 l2dhdr_asize = adddev->l2ad_dev_hdr_asize =
8890 MAX(sizeof (*adddev->l2ad_dev_hdr), 1 << vd->vdev_ashift);
8891 adddev->l2ad_start = VDEV_LABEL_START_SIZE + l2dhdr_asize;
8892 adddev->l2ad_end = VDEV_LABEL_START_SIZE + vdev_get_min_asize(vd);
8893 ASSERT3U(adddev->l2ad_start, <, adddev->l2ad_end);
8894 adddev->l2ad_hand = adddev->l2ad_start;
8895 adddev->l2ad_evict = adddev->l2ad_start;
8896 adddev->l2ad_first = B_TRUE;
8897 adddev->l2ad_writing = B_FALSE;
8898 adddev->l2ad_dev_hdr = kmem_zalloc(l2dhdr_asize, KM_SLEEP);
8899
8900 mutex_init(&adddev->l2ad_mtx, NULL, MUTEX_DEFAULT, NULL);
8901 /*
8902 * This is a list of all ARC buffers that are still valid on the
8903 * device.
8904 */
8905 list_create(&adddev->l2ad_buflist, sizeof (arc_buf_hdr_t),
8906 offsetof(arc_buf_hdr_t, b_l2hdr.b_l2node));
8907
8908 /*
8909 * This is a list of pointers to log blocks that are still present
8910 * on the device.
8911 */
8912 list_create(&adddev->l2ad_lbptr_list, sizeof (l2arc_lb_ptr_buf_t),
8913 offsetof(l2arc_lb_ptr_buf_t, node));
8914
8915 vdev_space_update(vd, 0, 0, adddev->l2ad_end - adddev->l2ad_hand);
8916 zfs_refcount_create(&adddev->l2ad_alloc);
8917 zfs_refcount_create(&adddev->l2ad_lb_asize);
8918 zfs_refcount_create(&adddev->l2ad_lb_count);
8919
8920 /*
8921 * Add device to global list
8922 */
8923 mutex_enter(&l2arc_dev_mtx);
8924 list_insert_head(l2arc_dev_list, adddev);
8925 atomic_inc_64(&l2arc_ndev);
8926 mutex_exit(&l2arc_dev_mtx);
8927
8928 /*
8929 * Decide if vdev is eligible for L2ARC rebuild
8930 */
8931 l2arc_rebuild_vdev(adddev->l2ad_vdev, B_FALSE);
8932 }
8933
8934 void
l2arc_rebuild_vdev(vdev_t * vd,boolean_t reopen)8935 l2arc_rebuild_vdev(vdev_t *vd, boolean_t reopen)
8936 {
8937 l2arc_dev_t *dev = NULL;
8938 l2arc_dev_hdr_phys_t *l2dhdr;
8939 uint64_t l2dhdr_asize;
8940 spa_t *spa;
8941
8942 dev = l2arc_vdev_get(vd);
8943 ASSERT3P(dev, !=, NULL);
8944 spa = dev->l2ad_spa;
8945 l2dhdr = dev->l2ad_dev_hdr;
8946 l2dhdr_asize = dev->l2ad_dev_hdr_asize;
8947
8948 /*
8949 * The L2ARC has to hold at least the payload of one log block for
8950 * them to be restored (persistent L2ARC). The payload of a log block
8951 * depends on the amount of its log entries. We always write log blocks
8952 * with 1022 entries. How many of them are committed or restored depends
8953 * on the size of the L2ARC device. Thus the maximum payload of
8954 * one log block is 1022 * SPA_MAXBLOCKSIZE = 16GB. If the L2ARC device
8955 * is less than that, we reduce the amount of committed and restored
8956 * log entries per block so as to enable persistence.
8957 */
8958 if (dev->l2ad_end < l2arc_rebuild_blocks_min_l2size) {
8959 dev->l2ad_log_entries = 0;
8960 } else {
8961 dev->l2ad_log_entries = MIN((dev->l2ad_end -
8962 dev->l2ad_start) >> SPA_MAXBLOCKSHIFT,
8963 L2ARC_LOG_BLK_MAX_ENTRIES);
8964 }
8965
8966 /*
8967 * Read the device header, if an error is returned do not rebuild L2ARC.
8968 */
8969 if (l2arc_dev_hdr_read(dev) == 0 && dev->l2ad_log_entries > 0) {
8970 /*
8971 * If we are onlining a cache device (vdev_reopen) that was
8972 * still present (l2arc_vdev_present()) and rebuild is enabled,
8973 * we should evict all ARC buffers and pointers to log blocks
8974 * and reclaim their space before restoring its contents to
8975 * L2ARC.
8976 */
8977 if (reopen) {
8978 if (!l2arc_rebuild_enabled) {
8979 return;
8980 } else {
8981 l2arc_evict(dev, 0, B_TRUE);
8982 /* start a new log block */
8983 dev->l2ad_log_ent_idx = 0;
8984 dev->l2ad_log_blk_payload_asize = 0;
8985 dev->l2ad_log_blk_payload_start = 0;
8986 }
8987 }
8988 /*
8989 * Just mark the device as pending for a rebuild. We won't
8990 * be starting a rebuild in line here as it would block pool
8991 * import. Instead spa_load_impl will hand that off to an
8992 * async task which will call l2arc_spa_rebuild_start.
8993 */
8994 dev->l2ad_rebuild = B_TRUE;
8995 } else if (spa_writeable(spa)) {
8996 /*
8997 * In this case create a new header. We zero out the memory
8998 * holding the header to reset dh_start_lbps.
8999 */
9000 bzero(l2dhdr, l2dhdr_asize);
9001 l2arc_dev_hdr_update(dev);
9002 }
9003 }
9004
9005 /*
9006 * Remove a vdev from the L2ARC.
9007 */
9008 void
l2arc_remove_vdev(vdev_t * vd)9009 l2arc_remove_vdev(vdev_t *vd)
9010 {
9011 l2arc_dev_t *remdev = NULL;
9012
9013 /*
9014 * Find the device by vdev
9015 */
9016 remdev = l2arc_vdev_get(vd);
9017 ASSERT3P(remdev, !=, NULL);
9018
9019 /*
9020 * Cancel any ongoing or scheduled rebuild.
9021 */
9022 mutex_enter(&l2arc_rebuild_thr_lock);
9023 if (remdev->l2ad_rebuild_began == B_TRUE) {
9024 remdev->l2ad_rebuild_cancel = B_TRUE;
9025 while (remdev->l2ad_rebuild == B_TRUE)
9026 cv_wait(&l2arc_rebuild_thr_cv, &l2arc_rebuild_thr_lock);
9027 }
9028 mutex_exit(&l2arc_rebuild_thr_lock);
9029
9030 /*
9031 * Remove device from global list
9032 */
9033 mutex_enter(&l2arc_dev_mtx);
9034 list_remove(l2arc_dev_list, remdev);
9035 l2arc_dev_last = NULL; /* may have been invalidated */
9036 atomic_dec_64(&l2arc_ndev);
9037 mutex_exit(&l2arc_dev_mtx);
9038
9039 /*
9040 * Clear all buflists and ARC references. L2ARC device flush.
9041 */
9042 l2arc_evict(remdev, 0, B_TRUE);
9043 list_destroy(&remdev->l2ad_buflist);
9044 ASSERT(list_is_empty(&remdev->l2ad_lbptr_list));
9045 list_destroy(&remdev->l2ad_lbptr_list);
9046 mutex_destroy(&remdev->l2ad_mtx);
9047 zfs_refcount_destroy(&remdev->l2ad_alloc);
9048 zfs_refcount_destroy(&remdev->l2ad_lb_asize);
9049 zfs_refcount_destroy(&remdev->l2ad_lb_count);
9050 kmem_free(remdev->l2ad_dev_hdr, remdev->l2ad_dev_hdr_asize);
9051 kmem_free(remdev, sizeof (l2arc_dev_t));
9052 }
9053
9054 void
l2arc_init(void)9055 l2arc_init(void)
9056 {
9057 l2arc_thread_exit = 0;
9058 l2arc_ndev = 0;
9059 l2arc_writes_sent = 0;
9060 l2arc_writes_done = 0;
9061
9062 mutex_init(&l2arc_feed_thr_lock, NULL, MUTEX_DEFAULT, NULL);
9063 cv_init(&l2arc_feed_thr_cv, NULL, CV_DEFAULT, NULL);
9064 mutex_init(&l2arc_rebuild_thr_lock, NULL, MUTEX_DEFAULT, NULL);
9065 cv_init(&l2arc_rebuild_thr_cv, NULL, CV_DEFAULT, NULL);
9066 mutex_init(&l2arc_dev_mtx, NULL, MUTEX_DEFAULT, NULL);
9067 mutex_init(&l2arc_free_on_write_mtx, NULL, MUTEX_DEFAULT, NULL);
9068
9069 l2arc_dev_list = &L2ARC_dev_list;
9070 l2arc_free_on_write = &L2ARC_free_on_write;
9071 list_create(l2arc_dev_list, sizeof (l2arc_dev_t),
9072 offsetof(l2arc_dev_t, l2ad_node));
9073 list_create(l2arc_free_on_write, sizeof (l2arc_data_free_t),
9074 offsetof(l2arc_data_free_t, l2df_list_node));
9075 }
9076
9077 void
l2arc_fini(void)9078 l2arc_fini(void)
9079 {
9080 /*
9081 * This is called from dmu_fini(), which is called from spa_fini();
9082 * Because of this, we can assume that all l2arc devices have
9083 * already been removed when the pools themselves were removed.
9084 */
9085
9086 l2arc_do_free_on_write();
9087
9088 mutex_destroy(&l2arc_feed_thr_lock);
9089 cv_destroy(&l2arc_feed_thr_cv);
9090 mutex_destroy(&l2arc_rebuild_thr_lock);
9091 cv_destroy(&l2arc_rebuild_thr_cv);
9092 mutex_destroy(&l2arc_dev_mtx);
9093 mutex_destroy(&l2arc_free_on_write_mtx);
9094
9095 list_destroy(l2arc_dev_list);
9096 list_destroy(l2arc_free_on_write);
9097 }
9098
9099 void
l2arc_start(void)9100 l2arc_start(void)
9101 {
9102 if (!(spa_mode_global & FWRITE))
9103 return;
9104
9105 (void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
9106 TS_RUN, minclsyspri);
9107 }
9108
9109 void
l2arc_stop(void)9110 l2arc_stop(void)
9111 {
9112 if (!(spa_mode_global & FWRITE))
9113 return;
9114
9115 mutex_enter(&l2arc_feed_thr_lock);
9116 cv_signal(&l2arc_feed_thr_cv); /* kick thread out of startup */
9117 l2arc_thread_exit = 1;
9118 while (l2arc_thread_exit != 0)
9119 cv_wait(&l2arc_feed_thr_cv, &l2arc_feed_thr_lock);
9120 mutex_exit(&l2arc_feed_thr_lock);
9121 }
9122
9123 /*
9124 * Punches out rebuild threads for the L2ARC devices in a spa. This should
9125 * be called after pool import from the spa async thread, since starting
9126 * these threads directly from spa_import() will make them part of the
9127 * "zpool import" context and delay process exit (and thus pool import).
9128 */
9129 void
l2arc_spa_rebuild_start(spa_t * spa)9130 l2arc_spa_rebuild_start(spa_t *spa)
9131 {
9132 ASSERT(MUTEX_HELD(&spa_namespace_lock));
9133
9134 /*
9135 * Locate the spa's l2arc devices and kick off rebuild threads.
9136 */
9137 for (int i = 0; i < spa->spa_l2cache.sav_count; i++) {
9138 l2arc_dev_t *dev =
9139 l2arc_vdev_get(spa->spa_l2cache.sav_vdevs[i]);
9140 if (dev == NULL) {
9141 /* Don't attempt a rebuild if the vdev is UNAVAIL */
9142 continue;
9143 }
9144 mutex_enter(&l2arc_rebuild_thr_lock);
9145 if (dev->l2ad_rebuild && !dev->l2ad_rebuild_cancel) {
9146 dev->l2ad_rebuild_began = B_TRUE;
9147 (void) thread_create(NULL, 0,
9148 (void (*)(void *))l2arc_dev_rebuild_start,
9149 dev, 0, &p0, TS_RUN, minclsyspri);
9150 }
9151 mutex_exit(&l2arc_rebuild_thr_lock);
9152 }
9153 }
9154
9155 /*
9156 * Main entry point for L2ARC rebuilding.
9157 */
9158 static void
l2arc_dev_rebuild_start(l2arc_dev_t * dev)9159 l2arc_dev_rebuild_start(l2arc_dev_t *dev)
9160 {
9161 VERIFY(!dev->l2ad_rebuild_cancel);
9162 VERIFY(dev->l2ad_rebuild);
9163 (void) l2arc_rebuild(dev);
9164 mutex_enter(&l2arc_rebuild_thr_lock);
9165 dev->l2ad_rebuild_began = B_FALSE;
9166 dev->l2ad_rebuild = B_FALSE;
9167 mutex_exit(&l2arc_rebuild_thr_lock);
9168
9169 thread_exit();
9170 }
9171
9172 /*
9173 * This function implements the actual L2ARC metadata rebuild. It:
9174 * starts reading the log block chain and restores each block's contents
9175 * to memory (reconstructing arc_buf_hdr_t's).
9176 *
9177 * Operation stops under any of the following conditions:
9178 *
9179 * 1) We reach the end of the log block chain.
9180 * 2) We encounter *any* error condition (cksum errors, io errors)
9181 */
9182 static int
l2arc_rebuild(l2arc_dev_t * dev)9183 l2arc_rebuild(l2arc_dev_t *dev)
9184 {
9185 vdev_t *vd = dev->l2ad_vdev;
9186 spa_t *spa = vd->vdev_spa;
9187 int err = 0;
9188 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9189 l2arc_log_blk_phys_t *this_lb, *next_lb;
9190 zio_t *this_io = NULL, *next_io = NULL;
9191 l2arc_log_blkptr_t lbps[2];
9192 l2arc_lb_ptr_buf_t *lb_ptr_buf;
9193 boolean_t lock_held;
9194
9195 this_lb = kmem_zalloc(sizeof (*this_lb), KM_SLEEP);
9196 next_lb = kmem_zalloc(sizeof (*next_lb), KM_SLEEP);
9197
9198 /*
9199 * We prevent device removal while issuing reads to the device,
9200 * then during the rebuilding phases we drop this lock again so
9201 * that a spa_unload or device remove can be initiated - this is
9202 * safe, because the spa will signal us to stop before removing
9203 * our device and wait for us to stop.
9204 */
9205 spa_config_enter(spa, SCL_L2ARC, vd, RW_READER);
9206 lock_held = B_TRUE;
9207
9208 /*
9209 * Retrieve the persistent L2ARC device state.
9210 * L2BLK_GET_PSIZE returns aligned size for log blocks.
9211 */
9212 dev->l2ad_evict = MAX(l2dhdr->dh_evict, dev->l2ad_start);
9213 dev->l2ad_hand = MAX(l2dhdr->dh_start_lbps[0].lbp_daddr +
9214 L2BLK_GET_PSIZE((&l2dhdr->dh_start_lbps[0])->lbp_prop),
9215 dev->l2ad_start);
9216 dev->l2ad_first = !!(l2dhdr->dh_flags & L2ARC_DEV_HDR_EVICT_FIRST);
9217
9218 /*
9219 * In case the zfs module parameter l2arc_rebuild_enabled is false
9220 * we do not start the rebuild process.
9221 */
9222 if (!l2arc_rebuild_enabled)
9223 goto out;
9224
9225 /* Prepare the rebuild process */
9226 bcopy(l2dhdr->dh_start_lbps, lbps, sizeof (lbps));
9227
9228 /* Start the rebuild process */
9229 for (;;) {
9230 if (!l2arc_log_blkptr_valid(dev, &lbps[0]))
9231 break;
9232
9233 if ((err = l2arc_log_blk_read(dev, &lbps[0], &lbps[1],
9234 this_lb, next_lb, this_io, &next_io)) != 0)
9235 goto out;
9236
9237 /*
9238 * Our memory pressure valve. If the system is running low
9239 * on memory, rather than swamping memory with new ARC buf
9240 * hdrs, we opt not to rebuild the L2ARC. At this point,
9241 * however, we have already set up our L2ARC dev to chain in
9242 * new metadata log blocks, so the user may choose to offline/
9243 * online the L2ARC dev at a later time (or re-import the pool)
9244 * to reconstruct it (when there's less memory pressure).
9245 */
9246 if (l2arc_hdr_limit_reached()) {
9247 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_lowmem);
9248 cmn_err(CE_NOTE, "System running low on memory, "
9249 "aborting L2ARC rebuild.");
9250 err = SET_ERROR(ENOMEM);
9251 goto out;
9252 }
9253
9254 spa_config_exit(spa, SCL_L2ARC, vd);
9255 lock_held = B_FALSE;
9256
9257 /*
9258 * Now that we know that the next_lb checks out alright, we
9259 * can start reconstruction from this log block.
9260 * L2BLK_GET_PSIZE returns aligned size for log blocks.
9261 */
9262 uint64_t asize = L2BLK_GET_PSIZE((&lbps[0])->lbp_prop);
9263 l2arc_log_blk_restore(dev, this_lb, asize);
9264
9265 /*
9266 * log block restored, include its pointer in the list of
9267 * pointers to log blocks present in the L2ARC device.
9268 */
9269 lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP);
9270 lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t),
9271 KM_SLEEP);
9272 bcopy(&lbps[0], lb_ptr_buf->lb_ptr,
9273 sizeof (l2arc_log_blkptr_t));
9274 mutex_enter(&dev->l2ad_mtx);
9275 list_insert_tail(&dev->l2ad_lbptr_list, lb_ptr_buf);
9276 ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize);
9277 ARCSTAT_BUMP(arcstat_l2_log_blk_count);
9278 zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf);
9279 zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf);
9280 mutex_exit(&dev->l2ad_mtx);
9281 vdev_space_update(vd, asize, 0, 0);
9282
9283 /* BEGIN CSTYLED */
9284 /*
9285 * Protection against loops of log blocks:
9286 *
9287 * l2ad_hand l2ad_evict
9288 * V V
9289 * l2ad_start |=======================================| l2ad_end
9290 * -----|||----|||---|||----|||
9291 * (3) (2) (1) (0)
9292 * ---|||---|||----|||---|||
9293 * (7) (6) (5) (4)
9294 *
9295 * In this situation the pointer of log block (4) passes
9296 * l2arc_log_blkptr_valid() but the log block should not be
9297 * restored as it is overwritten by the payload of log block
9298 * (0). Only log blocks (0)-(3) should be restored. We check
9299 * whether l2ad_evict lies in between the payload starting
9300 * offset of the next log block (lbps[1].lbp_payload_start)
9301 * and the payload starting offset of the present log block
9302 * (lbps[0].lbp_payload_start). If true and this isn't the
9303 * first pass, we are looping from the beginning and we should
9304 * stop.
9305 */
9306 /* END CSTYLED */
9307 if (l2arc_range_check_overlap(lbps[1].lbp_payload_start,
9308 lbps[0].lbp_payload_start, dev->l2ad_evict) &&
9309 !dev->l2ad_first)
9310 goto out;
9311
9312 for (;;) {
9313 mutex_enter(&l2arc_rebuild_thr_lock);
9314 if (dev->l2ad_rebuild_cancel) {
9315 dev->l2ad_rebuild = B_FALSE;
9316 cv_signal(&l2arc_rebuild_thr_cv);
9317 mutex_exit(&l2arc_rebuild_thr_lock);
9318 err = SET_ERROR(ECANCELED);
9319 goto out;
9320 }
9321 mutex_exit(&l2arc_rebuild_thr_lock);
9322 if (spa_config_tryenter(spa, SCL_L2ARC, vd,
9323 RW_READER)) {
9324 lock_held = B_TRUE;
9325 break;
9326 }
9327 /*
9328 * L2ARC config lock held by somebody in writer,
9329 * possibly due to them trying to remove us. They'll
9330 * likely to want us to shut down, so after a little
9331 * delay, we check l2ad_rebuild_cancel and retry
9332 * the lock again.
9333 */
9334 delay(1);
9335 }
9336
9337 /*
9338 * Continue with the next log block.
9339 */
9340 lbps[0] = lbps[1];
9341 lbps[1] = this_lb->lb_prev_lbp;
9342 PTR_SWAP(this_lb, next_lb);
9343 this_io = next_io;
9344 next_io = NULL;
9345 }
9346
9347 if (this_io != NULL)
9348 l2arc_log_blk_fetch_abort(this_io);
9349 out:
9350 if (next_io != NULL)
9351 l2arc_log_blk_fetch_abort(next_io);
9352 kmem_free(this_lb, sizeof (*this_lb));
9353 kmem_free(next_lb, sizeof (*next_lb));
9354
9355 if (!l2arc_rebuild_enabled) {
9356 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9357 "disabled");
9358 } else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) > 0) {
9359 ARCSTAT_BUMP(arcstat_l2_rebuild_success);
9360 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9361 "successful, restored %llu blocks",
9362 (u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
9363 } else if (err == 0 && zfs_refcount_count(&dev->l2ad_lb_count) == 0) {
9364 /*
9365 * No error but also nothing restored, meaning the lbps array
9366 * in the device header points to invalid/non-present log
9367 * blocks. Reset the header.
9368 */
9369 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9370 "no valid log blocks");
9371 bzero(l2dhdr, dev->l2ad_dev_hdr_asize);
9372 l2arc_dev_hdr_update(dev);
9373 } else if (err == ECANCELED) {
9374 /*
9375 * In case the rebuild was canceled do not log to spa history
9376 * log as the pool may be in the process of being removed.
9377 */
9378 zfs_dbgmsg("L2ARC rebuild aborted, restored %llu blocks",
9379 zfs_refcount_count(&dev->l2ad_lb_count));
9380 } else if (err != 0) {
9381 spa_history_log_internal(spa, "L2ARC rebuild", NULL,
9382 "aborted, restored %llu blocks",
9383 (u_longlong_t)zfs_refcount_count(&dev->l2ad_lb_count));
9384 }
9385
9386 if (lock_held)
9387 spa_config_exit(spa, SCL_L2ARC, vd);
9388
9389 return (err);
9390 }
9391
9392 /*
9393 * Attempts to read the device header on the provided L2ARC device and writes
9394 * it to `hdr'. On success, this function returns 0, otherwise the appropriate
9395 * error code is returned.
9396 */
9397 static int
l2arc_dev_hdr_read(l2arc_dev_t * dev)9398 l2arc_dev_hdr_read(l2arc_dev_t *dev)
9399 {
9400 int err;
9401 uint64_t guid;
9402 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9403 const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
9404 abd_t *abd;
9405
9406 guid = spa_guid(dev->l2ad_vdev->vdev_spa);
9407
9408 abd = abd_get_from_buf(l2dhdr, l2dhdr_asize);
9409
9410 err = zio_wait(zio_read_phys(NULL, dev->l2ad_vdev,
9411 VDEV_LABEL_START_SIZE, l2dhdr_asize, abd,
9412 ZIO_CHECKSUM_LABEL, NULL, NULL, ZIO_PRIORITY_SYNC_READ,
9413 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
9414 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY |
9415 ZIO_FLAG_SPECULATIVE, B_FALSE));
9416
9417 abd_put(abd);
9418
9419 if (err != 0) {
9420 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_dh_errors);
9421 zfs_dbgmsg("L2ARC IO error (%d) while reading device header, "
9422 "vdev guid: %llu", err, dev->l2ad_vdev->vdev_guid);
9423 return (err);
9424 }
9425
9426 if (l2dhdr->dh_magic == BSWAP_64(L2ARC_DEV_HDR_MAGIC))
9427 byteswap_uint64_array(l2dhdr, sizeof (*l2dhdr));
9428
9429 if (l2dhdr->dh_magic != L2ARC_DEV_HDR_MAGIC ||
9430 l2dhdr->dh_spa_guid != guid ||
9431 l2dhdr->dh_vdev_guid != dev->l2ad_vdev->vdev_guid ||
9432 l2dhdr->dh_version != L2ARC_PERSISTENT_VERSION ||
9433 l2dhdr->dh_log_entries != dev->l2ad_log_entries ||
9434 l2dhdr->dh_end != dev->l2ad_end ||
9435 !l2arc_range_check_overlap(dev->l2ad_start, dev->l2ad_end,
9436 l2dhdr->dh_evict)) {
9437 /*
9438 * Attempt to rebuild a device containing no actual dev hdr
9439 * or containing a header from some other pool or from another
9440 * version of persistent L2ARC.
9441 */
9442 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_unsupported);
9443 return (SET_ERROR(ENOTSUP));
9444 }
9445
9446 return (0);
9447 }
9448
9449 /*
9450 * Reads L2ARC log blocks from storage and validates their contents.
9451 *
9452 * This function implements a simple fetcher to make sure that while
9453 * we're processing one buffer the L2ARC is already fetching the next
9454 * one in the chain.
9455 *
9456 * The arguments this_lp and next_lp point to the current and next log block
9457 * address in the block chain. Similarly, this_lb and next_lb hold the
9458 * l2arc_log_blk_phys_t's of the current and next L2ARC blk.
9459 *
9460 * The `this_io' and `next_io' arguments are used for block fetching.
9461 * When issuing the first blk IO during rebuild, you should pass NULL for
9462 * `this_io'. This function will then issue a sync IO to read the block and
9463 * also issue an async IO to fetch the next block in the block chain. The
9464 * fetched IO is returned in `next_io'. On subsequent calls to this
9465 * function, pass the value returned in `next_io' from the previous call
9466 * as `this_io' and a fresh `next_io' pointer to hold the next fetch IO.
9467 * Prior to the call, you should initialize your `next_io' pointer to be
9468 * NULL. If no fetch IO was issued, the pointer is left set at NULL.
9469 *
9470 * On success, this function returns 0, otherwise it returns an appropriate
9471 * error code. On error the fetching IO is aborted and cleared before
9472 * returning from this function. Therefore, if we return `success', the
9473 * caller can assume that we have taken care of cleanup of fetch IOs.
9474 */
9475 static int
l2arc_log_blk_read(l2arc_dev_t * dev,const l2arc_log_blkptr_t * this_lbp,const l2arc_log_blkptr_t * next_lbp,l2arc_log_blk_phys_t * this_lb,l2arc_log_blk_phys_t * next_lb,zio_t * this_io,zio_t ** next_io)9476 l2arc_log_blk_read(l2arc_dev_t *dev,
9477 const l2arc_log_blkptr_t *this_lbp, const l2arc_log_blkptr_t *next_lbp,
9478 l2arc_log_blk_phys_t *this_lb, l2arc_log_blk_phys_t *next_lb,
9479 zio_t *this_io, zio_t **next_io)
9480 {
9481 int err = 0;
9482 zio_cksum_t cksum;
9483 abd_t *abd = NULL;
9484 uint64_t asize;
9485
9486 ASSERT(this_lbp != NULL && next_lbp != NULL);
9487 ASSERT(this_lb != NULL && next_lb != NULL);
9488 ASSERT(next_io != NULL && *next_io == NULL);
9489 ASSERT(l2arc_log_blkptr_valid(dev, this_lbp));
9490
9491 /*
9492 * Check to see if we have issued the IO for this log block in a
9493 * previous run. If not, this is the first call, so issue it now.
9494 */
9495 if (this_io == NULL) {
9496 this_io = l2arc_log_blk_fetch(dev->l2ad_vdev, this_lbp,
9497 this_lb);
9498 }
9499
9500 /*
9501 * Peek to see if we can start issuing the next IO immediately.
9502 */
9503 if (l2arc_log_blkptr_valid(dev, next_lbp)) {
9504 /*
9505 * Start issuing IO for the next log block early - this
9506 * should help keep the L2ARC device busy while we
9507 * decompress and restore this log block.
9508 */
9509 *next_io = l2arc_log_blk_fetch(dev->l2ad_vdev, next_lbp,
9510 next_lb);
9511 }
9512
9513 /* Wait for the IO to read this log block to complete */
9514 if ((err = zio_wait(this_io)) != 0) {
9515 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_io_errors);
9516 zfs_dbgmsg("L2ARC IO error (%d) while reading log block, "
9517 "offset: %llu, vdev guid: %llu", err, this_lbp->lbp_daddr,
9518 dev->l2ad_vdev->vdev_guid);
9519 goto cleanup;
9520 }
9521
9522 /*
9523 * Make sure the buffer checks out.
9524 * L2BLK_GET_PSIZE returns aligned size for log blocks.
9525 */
9526 asize = L2BLK_GET_PSIZE((this_lbp)->lbp_prop);
9527 fletcher_4_native(this_lb, asize, NULL, &cksum);
9528 if (!ZIO_CHECKSUM_EQUAL(cksum, this_lbp->lbp_cksum)) {
9529 ARCSTAT_BUMP(arcstat_l2_rebuild_abort_cksum_lb_errors);
9530 zfs_dbgmsg("L2ARC log block cksum failed, offset: %llu, "
9531 "vdev guid: %llu, l2ad_hand: %llu, l2ad_evict: %llu",
9532 this_lbp->lbp_daddr, dev->l2ad_vdev->vdev_guid,
9533 dev->l2ad_hand, dev->l2ad_evict);
9534 err = SET_ERROR(ECKSUM);
9535 goto cleanup;
9536 }
9537
9538 /* Now we can take our time decoding this buffer */
9539 switch (L2BLK_GET_COMPRESS((this_lbp)->lbp_prop)) {
9540 case ZIO_COMPRESS_OFF:
9541 break;
9542 case ZIO_COMPRESS_LZ4:
9543 abd = abd_alloc_for_io(asize, B_TRUE);
9544 abd_copy_from_buf_off(abd, this_lb, 0, asize);
9545 if ((err = zio_decompress_data(
9546 L2BLK_GET_COMPRESS((this_lbp)->lbp_prop),
9547 abd, this_lb, asize, sizeof (*this_lb))) != 0) {
9548 err = SET_ERROR(EINVAL);
9549 goto cleanup;
9550 }
9551 break;
9552 default:
9553 err = SET_ERROR(EINVAL);
9554 goto cleanup;
9555 }
9556 if (this_lb->lb_magic == BSWAP_64(L2ARC_LOG_BLK_MAGIC))
9557 byteswap_uint64_array(this_lb, sizeof (*this_lb));
9558 if (this_lb->lb_magic != L2ARC_LOG_BLK_MAGIC) {
9559 err = SET_ERROR(EINVAL);
9560 goto cleanup;
9561 }
9562 cleanup:
9563 /* Abort an in-flight fetch I/O in case of error */
9564 if (err != 0 && *next_io != NULL) {
9565 l2arc_log_blk_fetch_abort(*next_io);
9566 *next_io = NULL;
9567 }
9568 if (abd != NULL)
9569 abd_free(abd);
9570 return (err);
9571 }
9572
9573 /*
9574 * Restores the payload of a log block to ARC. This creates empty ARC hdr
9575 * entries which only contain an l2arc hdr, essentially restoring the
9576 * buffers to their L2ARC evicted state. This function also updates space
9577 * usage on the L2ARC vdev to make sure it tracks restored buffers.
9578 */
9579 static void
l2arc_log_blk_restore(l2arc_dev_t * dev,const l2arc_log_blk_phys_t * lb,uint64_t lb_asize)9580 l2arc_log_blk_restore(l2arc_dev_t *dev, const l2arc_log_blk_phys_t *lb,
9581 uint64_t lb_asize)
9582 {
9583 uint64_t size = 0, asize = 0;
9584 uint64_t log_entries = dev->l2ad_log_entries;
9585
9586 /*
9587 * Usually arc_adapt() is called only for data, not headers, but
9588 * since we may allocate significant amount of memory here, let ARC
9589 * grow its arc_c.
9590 */
9591 arc_adapt(log_entries * HDR_L2ONLY_SIZE, arc_l2c_only);
9592
9593 for (int i = log_entries - 1; i >= 0; i--) {
9594 /*
9595 * Restore goes in the reverse temporal direction to preserve
9596 * correct temporal ordering of buffers in the l2ad_buflist.
9597 * l2arc_hdr_restore also does a list_insert_tail instead of
9598 * list_insert_head on the l2ad_buflist:
9599 *
9600 * LIST l2ad_buflist LIST
9601 * HEAD <------ (time) ------ TAIL
9602 * direction +-----+-----+-----+-----+-----+ direction
9603 * of l2arc <== | buf | buf | buf | buf | buf | ===> of rebuild
9604 * fill +-----+-----+-----+-----+-----+
9605 * ^ ^
9606 * | |
9607 * | |
9608 * l2arc_feed_thread l2arc_rebuild
9609 * will place new bufs here restores bufs here
9610 *
9611 * During l2arc_rebuild() the device is not used by
9612 * l2arc_feed_thread() as dev->l2ad_rebuild is set to true.
9613 */
9614 size += L2BLK_GET_LSIZE((&lb->lb_entries[i])->le_prop);
9615 asize += vdev_psize_to_asize(dev->l2ad_vdev,
9616 L2BLK_GET_PSIZE((&lb->lb_entries[i])->le_prop));
9617 l2arc_hdr_restore(&lb->lb_entries[i], dev);
9618 }
9619
9620 /*
9621 * Record rebuild stats:
9622 * size Logical size of restored buffers in the L2ARC
9623 * asize Aligned size of restored buffers in the L2ARC
9624 */
9625 ARCSTAT_INCR(arcstat_l2_rebuild_size, size);
9626 ARCSTAT_INCR(arcstat_l2_rebuild_asize, asize);
9627 ARCSTAT_INCR(arcstat_l2_rebuild_bufs, log_entries);
9628 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, lb_asize);
9629 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio, asize / lb_asize);
9630 ARCSTAT_BUMP(arcstat_l2_rebuild_log_blks);
9631 }
9632
9633 /*
9634 * Restores a single ARC buf hdr from a log entry. The ARC buffer is put
9635 * into a state indicating that it has been evicted to L2ARC.
9636 */
9637 static void
l2arc_hdr_restore(const l2arc_log_ent_phys_t * le,l2arc_dev_t * dev)9638 l2arc_hdr_restore(const l2arc_log_ent_phys_t *le, l2arc_dev_t *dev)
9639 {
9640 arc_buf_hdr_t *hdr, *exists;
9641 kmutex_t *hash_lock;
9642 arc_buf_contents_t type = L2BLK_GET_TYPE((le)->le_prop);
9643 uint64_t asize;
9644
9645 /*
9646 * Do all the allocation before grabbing any locks, this lets us
9647 * sleep if memory is full and we don't have to deal with failed
9648 * allocations.
9649 */
9650 hdr = arc_buf_alloc_l2only(L2BLK_GET_LSIZE((le)->le_prop), type,
9651 dev, le->le_dva, le->le_daddr,
9652 L2BLK_GET_PSIZE((le)->le_prop), le->le_birth,
9653 L2BLK_GET_COMPRESS((le)->le_prop),
9654 L2BLK_GET_PROTECTED((le)->le_prop),
9655 L2BLK_GET_PREFETCH((le)->le_prop),
9656 L2BLK_GET_STATE((le)->le_prop));
9657 asize = vdev_psize_to_asize(dev->l2ad_vdev,
9658 L2BLK_GET_PSIZE((le)->le_prop));
9659
9660 /*
9661 * vdev_space_update() has to be called before arc_hdr_destroy() to
9662 * avoid underflow since the latter also calls vdev_space_update().
9663 */
9664 l2arc_hdr_arcstats_increment(hdr);
9665 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9666
9667 mutex_enter(&dev->l2ad_mtx);
9668 list_insert_tail(&dev->l2ad_buflist, hdr);
9669 (void) zfs_refcount_add_many(&dev->l2ad_alloc, arc_hdr_size(hdr), hdr);
9670 mutex_exit(&dev->l2ad_mtx);
9671
9672 exists = buf_hash_insert(hdr, &hash_lock);
9673 if (exists) {
9674 /* Buffer was already cached, no need to restore it. */
9675 arc_hdr_destroy(hdr);
9676 /*
9677 * If the buffer is already cached, check whether it has
9678 * L2ARC metadata. If not, enter them and update the flag.
9679 * This is important is case of onlining a cache device, since
9680 * we previously evicted all L2ARC metadata from ARC.
9681 */
9682 if (!HDR_HAS_L2HDR(exists)) {
9683 arc_hdr_set_flags(exists, ARC_FLAG_HAS_L2HDR);
9684 exists->b_l2hdr.b_dev = dev;
9685 exists->b_l2hdr.b_daddr = le->le_daddr;
9686 exists->b_l2hdr.b_arcs_state =
9687 L2BLK_GET_STATE((le)->le_prop);
9688 mutex_enter(&dev->l2ad_mtx);
9689 list_insert_tail(&dev->l2ad_buflist, exists);
9690 (void) zfs_refcount_add_many(&dev->l2ad_alloc,
9691 arc_hdr_size(exists), exists);
9692 mutex_exit(&dev->l2ad_mtx);
9693 l2arc_hdr_arcstats_increment(exists);
9694 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9695 }
9696 ARCSTAT_BUMP(arcstat_l2_rebuild_bufs_precached);
9697 }
9698
9699 mutex_exit(hash_lock);
9700 }
9701
9702 /*
9703 * Starts an asynchronous read IO to read a log block. This is used in log
9704 * block reconstruction to start reading the next block before we are done
9705 * decoding and reconstructing the current block, to keep the l2arc device
9706 * nice and hot with read IO to process.
9707 * The returned zio will contain newly allocated memory buffers for the IO
9708 * data which should then be freed by the caller once the zio is no longer
9709 * needed (i.e. due to it having completed). If you wish to abort this
9710 * zio, you should do so using l2arc_log_blk_fetch_abort, which takes
9711 * care of disposing of the allocated buffers correctly.
9712 */
9713 static zio_t *
l2arc_log_blk_fetch(vdev_t * vd,const l2arc_log_blkptr_t * lbp,l2arc_log_blk_phys_t * lb)9714 l2arc_log_blk_fetch(vdev_t *vd, const l2arc_log_blkptr_t *lbp,
9715 l2arc_log_blk_phys_t *lb)
9716 {
9717 uint32_t asize;
9718 zio_t *pio;
9719 l2arc_read_callback_t *cb;
9720
9721 /* L2BLK_GET_PSIZE returns aligned size for log blocks */
9722 asize = L2BLK_GET_PSIZE((lbp)->lbp_prop);
9723 ASSERT(asize <= sizeof (l2arc_log_blk_phys_t));
9724
9725 cb = kmem_zalloc(sizeof (l2arc_read_callback_t), KM_SLEEP);
9726 cb->l2rcb_abd = abd_get_from_buf(lb, asize);
9727 pio = zio_root(vd->vdev_spa, l2arc_blk_fetch_done, cb,
9728 ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE |
9729 ZIO_FLAG_DONT_RETRY);
9730 (void) zio_nowait(zio_read_phys(pio, vd, lbp->lbp_daddr, asize,
9731 cb->l2rcb_abd, ZIO_CHECKSUM_OFF, NULL, NULL,
9732 ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_DONT_CACHE | ZIO_FLAG_CANFAIL |
9733 ZIO_FLAG_DONT_PROPAGATE | ZIO_FLAG_DONT_RETRY, B_FALSE));
9734
9735 return (pio);
9736 }
9737
9738 /*
9739 * Aborts a zio returned from l2arc_log_blk_fetch and frees the data
9740 * buffers allocated for it.
9741 */
9742 static void
l2arc_log_blk_fetch_abort(zio_t * zio)9743 l2arc_log_blk_fetch_abort(zio_t *zio)
9744 {
9745 (void) zio_wait(zio);
9746 }
9747
9748 /*
9749 * Creates a zio to update the device header on an l2arc device.
9750 */
9751 static void
l2arc_dev_hdr_update(l2arc_dev_t * dev)9752 l2arc_dev_hdr_update(l2arc_dev_t *dev)
9753 {
9754 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9755 const uint64_t l2dhdr_asize = dev->l2ad_dev_hdr_asize;
9756 abd_t *abd;
9757 int err;
9758
9759 VERIFY(spa_config_held(dev->l2ad_spa, SCL_STATE_ALL, RW_READER));
9760
9761 l2dhdr->dh_magic = L2ARC_DEV_HDR_MAGIC;
9762 l2dhdr->dh_version = L2ARC_PERSISTENT_VERSION;
9763 l2dhdr->dh_spa_guid = spa_guid(dev->l2ad_vdev->vdev_spa);
9764 l2dhdr->dh_vdev_guid = dev->l2ad_vdev->vdev_guid;
9765 l2dhdr->dh_log_entries = dev->l2ad_log_entries;
9766 l2dhdr->dh_evict = dev->l2ad_evict;
9767 l2dhdr->dh_start = dev->l2ad_start;
9768 l2dhdr->dh_end = dev->l2ad_end;
9769 l2dhdr->dh_lb_asize = zfs_refcount_count(&dev->l2ad_lb_asize);
9770 l2dhdr->dh_lb_count = zfs_refcount_count(&dev->l2ad_lb_count);
9771 l2dhdr->dh_flags = 0;
9772 if (dev->l2ad_first)
9773 l2dhdr->dh_flags |= L2ARC_DEV_HDR_EVICT_FIRST;
9774
9775 abd = abd_get_from_buf(l2dhdr, l2dhdr_asize);
9776
9777 err = zio_wait(zio_write_phys(NULL, dev->l2ad_vdev,
9778 VDEV_LABEL_START_SIZE, l2dhdr_asize, abd, ZIO_CHECKSUM_LABEL, NULL,
9779 NULL, ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE));
9780
9781 abd_put(abd);
9782
9783 if (err != 0) {
9784 zfs_dbgmsg("L2ARC IO error (%d) while writing device header, "
9785 "vdev guid: %llu", err, dev->l2ad_vdev->vdev_guid);
9786 }
9787 }
9788
9789 /*
9790 * Commits a log block to the L2ARC device. This routine is invoked from
9791 * l2arc_write_buffers when the log block fills up.
9792 * This function allocates some memory to temporarily hold the serialized
9793 * buffer to be written. This is then released in l2arc_write_done.
9794 */
9795 static void
l2arc_log_blk_commit(l2arc_dev_t * dev,zio_t * pio,l2arc_write_callback_t * cb)9796 l2arc_log_blk_commit(l2arc_dev_t *dev, zio_t *pio, l2arc_write_callback_t *cb)
9797 {
9798 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
9799 l2arc_dev_hdr_phys_t *l2dhdr = dev->l2ad_dev_hdr;
9800 uint64_t psize, asize;
9801 zio_t *wzio;
9802 l2arc_lb_abd_buf_t *abd_buf;
9803 uint8_t *tmpbuf;
9804 l2arc_lb_ptr_buf_t *lb_ptr_buf;
9805
9806 VERIFY3S(dev->l2ad_log_ent_idx, ==, dev->l2ad_log_entries);
9807
9808 tmpbuf = zio_buf_alloc(sizeof (*lb));
9809 abd_buf = zio_buf_alloc(sizeof (*abd_buf));
9810 abd_buf->abd = abd_get_from_buf(lb, sizeof (*lb));
9811 lb_ptr_buf = kmem_zalloc(sizeof (l2arc_lb_ptr_buf_t), KM_SLEEP);
9812 lb_ptr_buf->lb_ptr = kmem_zalloc(sizeof (l2arc_log_blkptr_t), KM_SLEEP);
9813
9814 /* link the buffer into the block chain */
9815 lb->lb_prev_lbp = l2dhdr->dh_start_lbps[1];
9816 lb->lb_magic = L2ARC_LOG_BLK_MAGIC;
9817
9818 /*
9819 * l2arc_log_blk_commit() may be called multiple times during a single
9820 * l2arc_write_buffers() call. Save the allocated abd buffers in a list
9821 * so we can free them in l2arc_write_done() later on.
9822 */
9823 list_insert_tail(&cb->l2wcb_abd_list, abd_buf);
9824
9825 /* try to compress the buffer */
9826 psize = zio_compress_data(ZIO_COMPRESS_LZ4,
9827 abd_buf->abd, tmpbuf, sizeof (*lb));
9828
9829 /* a log block is never entirely zero */
9830 ASSERT(psize != 0);
9831 asize = vdev_psize_to_asize(dev->l2ad_vdev, psize);
9832 ASSERT(asize <= sizeof (*lb));
9833
9834 /*
9835 * Update the start log block pointer in the device header to point
9836 * to the log block we're about to write.
9837 */
9838 l2dhdr->dh_start_lbps[1] = l2dhdr->dh_start_lbps[0];
9839 l2dhdr->dh_start_lbps[0].lbp_daddr = dev->l2ad_hand;
9840 l2dhdr->dh_start_lbps[0].lbp_payload_asize =
9841 dev->l2ad_log_blk_payload_asize;
9842 l2dhdr->dh_start_lbps[0].lbp_payload_start =
9843 dev->l2ad_log_blk_payload_start;
9844 _NOTE(CONSTCOND)
9845 L2BLK_SET_LSIZE(
9846 (&l2dhdr->dh_start_lbps[0])->lbp_prop, sizeof (*lb));
9847 L2BLK_SET_PSIZE(
9848 (&l2dhdr->dh_start_lbps[0])->lbp_prop, asize);
9849 L2BLK_SET_CHECKSUM(
9850 (&l2dhdr->dh_start_lbps[0])->lbp_prop,
9851 ZIO_CHECKSUM_FLETCHER_4);
9852 if (asize < sizeof (*lb)) {
9853 /* compression succeeded */
9854 bzero(tmpbuf + psize, asize - psize);
9855 L2BLK_SET_COMPRESS(
9856 (&l2dhdr->dh_start_lbps[0])->lbp_prop,
9857 ZIO_COMPRESS_LZ4);
9858 } else {
9859 /* compression failed */
9860 bcopy(lb, tmpbuf, sizeof (*lb));
9861 L2BLK_SET_COMPRESS(
9862 (&l2dhdr->dh_start_lbps[0])->lbp_prop,
9863 ZIO_COMPRESS_OFF);
9864 }
9865
9866 /* checksum what we're about to write */
9867 fletcher_4_native(tmpbuf, asize, NULL,
9868 &l2dhdr->dh_start_lbps[0].lbp_cksum);
9869
9870 abd_put(abd_buf->abd);
9871
9872 /* perform the write itself */
9873 abd_buf->abd = abd_get_from_buf(tmpbuf, sizeof (*lb));
9874 abd_take_ownership_of_buf(abd_buf->abd, B_TRUE);
9875 wzio = zio_write_phys(pio, dev->l2ad_vdev, dev->l2ad_hand,
9876 asize, abd_buf->abd, ZIO_CHECKSUM_OFF, NULL, NULL,
9877 ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_CANFAIL, B_FALSE);
9878 DTRACE_PROBE2(l2arc__write, vdev_t *, dev->l2ad_vdev, zio_t *, wzio);
9879 (void) zio_nowait(wzio);
9880
9881 dev->l2ad_hand += asize;
9882 /*
9883 * Include the committed log block's pointer in the list of pointers
9884 * to log blocks present in the L2ARC device.
9885 */
9886 bcopy(&l2dhdr->dh_start_lbps[0], lb_ptr_buf->lb_ptr,
9887 sizeof (l2arc_log_blkptr_t));
9888 mutex_enter(&dev->l2ad_mtx);
9889 list_insert_head(&dev->l2ad_lbptr_list, lb_ptr_buf);
9890 ARCSTAT_INCR(arcstat_l2_log_blk_asize, asize);
9891 ARCSTAT_BUMP(arcstat_l2_log_blk_count);
9892 zfs_refcount_add_many(&dev->l2ad_lb_asize, asize, lb_ptr_buf);
9893 zfs_refcount_add(&dev->l2ad_lb_count, lb_ptr_buf);
9894 mutex_exit(&dev->l2ad_mtx);
9895 vdev_space_update(dev->l2ad_vdev, asize, 0, 0);
9896
9897 /* bump the kstats */
9898 ARCSTAT_INCR(arcstat_l2_write_bytes, asize);
9899 ARCSTAT_BUMP(arcstat_l2_log_blk_writes);
9900 ARCSTAT_F_AVG(arcstat_l2_log_blk_avg_asize, asize);
9901 ARCSTAT_F_AVG(arcstat_l2_data_to_meta_ratio,
9902 dev->l2ad_log_blk_payload_asize / asize);
9903
9904 /* start a new log block */
9905 dev->l2ad_log_ent_idx = 0;
9906 dev->l2ad_log_blk_payload_asize = 0;
9907 dev->l2ad_log_blk_payload_start = 0;
9908 }
9909
9910 /*
9911 * Validates an L2ARC log block address to make sure that it can be read
9912 * from the provided L2ARC device.
9913 */
9914 boolean_t
l2arc_log_blkptr_valid(l2arc_dev_t * dev,const l2arc_log_blkptr_t * lbp)9915 l2arc_log_blkptr_valid(l2arc_dev_t *dev, const l2arc_log_blkptr_t *lbp)
9916 {
9917 /* L2BLK_GET_PSIZE returns aligned size for log blocks */
9918 uint64_t asize = L2BLK_GET_PSIZE((lbp)->lbp_prop);
9919 uint64_t end = lbp->lbp_daddr + asize - 1;
9920 uint64_t start = lbp->lbp_payload_start;
9921 boolean_t evicted = B_FALSE;
9922
9923 /* BEGIN CSTYLED */
9924 /*
9925 * A log block is valid if all of the following conditions are true:
9926 * - it fits entirely (including its payload) between l2ad_start and
9927 * l2ad_end
9928 * - it has a valid size
9929 * - neither the log block itself nor part of its payload was evicted
9930 * by l2arc_evict():
9931 *
9932 * l2ad_hand l2ad_evict
9933 * | | lbp_daddr
9934 * | start | | end
9935 * | | | | |
9936 * V V V V V
9937 * l2ad_start ============================================ l2ad_end
9938 * --------------------------||||
9939 * ^ ^
9940 * | log block
9941 * payload
9942 */
9943 /* END CSTYLED */
9944 evicted =
9945 l2arc_range_check_overlap(start, end, dev->l2ad_hand) ||
9946 l2arc_range_check_overlap(start, end, dev->l2ad_evict) ||
9947 l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, start) ||
9948 l2arc_range_check_overlap(dev->l2ad_hand, dev->l2ad_evict, end);
9949
9950 return (start >= dev->l2ad_start && end <= dev->l2ad_end &&
9951 asize > 0 && asize <= sizeof (l2arc_log_blk_phys_t) &&
9952 (!evicted || dev->l2ad_first));
9953 }
9954
9955 /*
9956 * Inserts ARC buffer header `hdr' into the current L2ARC log block on
9957 * the device. The buffer being inserted must be present in L2ARC.
9958 * Returns B_TRUE if the L2ARC log block is full and needs to be committed
9959 * to L2ARC, or B_FALSE if it still has room for more ARC buffers.
9960 */
9961 static boolean_t
l2arc_log_blk_insert(l2arc_dev_t * dev,const arc_buf_hdr_t * hdr)9962 l2arc_log_blk_insert(l2arc_dev_t *dev, const arc_buf_hdr_t *hdr)
9963 {
9964 l2arc_log_blk_phys_t *lb = &dev->l2ad_log_blk;
9965 l2arc_log_ent_phys_t *le;
9966
9967 if (dev->l2ad_log_entries == 0)
9968 return (B_FALSE);
9969
9970 int index = dev->l2ad_log_ent_idx++;
9971
9972 ASSERT3S(index, <, dev->l2ad_log_entries);
9973 ASSERT(HDR_HAS_L2HDR(hdr));
9974
9975 le = &lb->lb_entries[index];
9976 bzero(le, sizeof (*le));
9977 le->le_dva = hdr->b_dva;
9978 le->le_birth = hdr->b_birth;
9979 le->le_daddr = hdr->b_l2hdr.b_daddr;
9980 if (index == 0)
9981 dev->l2ad_log_blk_payload_start = le->le_daddr;
9982 L2BLK_SET_LSIZE((le)->le_prop, HDR_GET_LSIZE(hdr));
9983 L2BLK_SET_PSIZE((le)->le_prop, HDR_GET_PSIZE(hdr));
9984 L2BLK_SET_COMPRESS((le)->le_prop, HDR_GET_COMPRESS(hdr));
9985 L2BLK_SET_TYPE((le)->le_prop, hdr->b_type);
9986 L2BLK_SET_PROTECTED((le)->le_prop, !!(HDR_PROTECTED(hdr)));
9987 L2BLK_SET_PREFETCH((le)->le_prop, !!(HDR_PREFETCH(hdr)));
9988 L2BLK_SET_STATE((le)->le_prop, hdr->b_l1hdr.b_state->arcs_state);
9989
9990 dev->l2ad_log_blk_payload_asize += vdev_psize_to_asize(dev->l2ad_vdev,
9991 HDR_GET_PSIZE(hdr));
9992
9993 return (dev->l2ad_log_ent_idx == dev->l2ad_log_entries);
9994 }
9995
9996 /*
9997 * Checks whether a given L2ARC device address sits in a time-sequential
9998 * range. The trick here is that the L2ARC is a rotary buffer, so we can't
9999 * just do a range comparison, we need to handle the situation in which the
10000 * range wraps around the end of the L2ARC device. Arguments:
10001 * bottom -- Lower end of the range to check (written to earlier).
10002 * top -- Upper end of the range to check (written to later).
10003 * check -- The address for which we want to determine if it sits in
10004 * between the top and bottom.
10005 *
10006 * The 3-way conditional below represents the following cases:
10007 *
10008 * bottom < top : Sequentially ordered case:
10009 * <check>--------+-------------------+
10010 * | (overlap here?) |
10011 * L2ARC dev V V
10012 * |---------------<bottom>============<top>--------------|
10013 *
10014 * bottom > top: Looped-around case:
10015 * <check>--------+------------------+
10016 * | (overlap here?) |
10017 * L2ARC dev V V
10018 * |===============<top>---------------<bottom>===========|
10019 * ^ ^
10020 * | (or here?) |
10021 * +---------------+---------<check>
10022 *
10023 * top == bottom : Just a single address comparison.
10024 */
10025 boolean_t
l2arc_range_check_overlap(uint64_t bottom,uint64_t top,uint64_t check)10026 l2arc_range_check_overlap(uint64_t bottom, uint64_t top, uint64_t check)
10027 {
10028 if (bottom < top)
10029 return (bottom <= check && check <= top);
10030 else if (bottom > top)
10031 return (check <= top || bottom <= check);
10032 else
10033 return (check == top);
10034 }
10035