xref: /illumos-gate/usr/src/uts/common/fs/zfs/zil.c (revision 4d7988d6)
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) 2011, 2018 by Delphix. All rights reserved.
24  * Copyright (c) 2014 Integros [integros.com]
25  */
26 
27 /* Portions Copyright 2010 Robert Milkowski */
28 
29 #include <sys/zfs_context.h>
30 #include <sys/spa.h>
31 #include <sys/spa_impl.h>
32 #include <sys/dmu.h>
33 #include <sys/zap.h>
34 #include <sys/arc.h>
35 #include <sys/stat.h>
36 #include <sys/resource.h>
37 #include <sys/zil.h>
38 #include <sys/zil_impl.h>
39 #include <sys/dsl_dataset.h>
40 #include <sys/vdev_impl.h>
41 #include <sys/dmu_tx.h>
42 #include <sys/dsl_pool.h>
43 #include <sys/abd.h>
44 
45 /*
46  * The ZFS Intent Log (ZIL) saves "transaction records" (itxs) of system
47  * calls that change the file system. Each itx has enough information to
48  * be able to replay them after a system crash, power loss, or
49  * equivalent failure mode. These are stored in memory until either:
50  *
51  *   1. they are committed to the pool by the DMU transaction group
52  *      (txg), at which point they can be discarded; or
53  *   2. they are committed to the on-disk ZIL for the dataset being
54  *      modified (e.g. due to an fsync, O_DSYNC, or other synchronous
55  *      requirement).
56  *
57  * In the event of a crash or power loss, the itxs contained by each
58  * dataset's on-disk ZIL will be replayed when that dataset is first
59  * instantianted (e.g. if the dataset is a normal fileystem, when it is
60  * first mounted).
61  *
62  * As hinted at above, there is one ZIL per dataset (both the in-memory
63  * representation, and the on-disk representation). The on-disk format
64  * consists of 3 parts:
65  *
66  *	- a single, per-dataset, ZIL header; which points to a chain of
67  *	- zero or more ZIL blocks; each of which contains
68  *	- zero or more ZIL records
69  *
70  * A ZIL record holds the information necessary to replay a single
71  * system call transaction. A ZIL block can hold many ZIL records, and
72  * the blocks are chained together, similarly to a singly linked list.
73  *
74  * Each ZIL block contains a block pointer (blkptr_t) to the next ZIL
75  * block in the chain, and the ZIL header points to the first block in
76  * the chain.
77  *
78  * Note, there is not a fixed place in the pool to hold these ZIL
79  * blocks; they are dynamically allocated and freed as needed from the
80  * blocks available on the pool, though they can be preferentially
81  * allocated from a dedicated "log" vdev.
82  */
83 
84 /*
85  * This controls the amount of time that a ZIL block (lwb) will remain
86  * "open" when it isn't "full", and it has a thread waiting for it to be
87  * committed to stable storage. Please refer to the zil_commit_waiter()
88  * function (and the comments within it) for more details.
89  */
90 int zfs_commit_timeout_pct = 5;
91 
92 /*
93  * Disable intent logging replay.  This global ZIL switch affects all pools.
94  */
95 int zil_replay_disable = 0;
96 
97 /*
98  * Disable the DKIOCFLUSHWRITECACHE commands that are normally sent to
99  * the disk(s) by the ZIL after an LWB write has completed. Setting this
100  * will cause ZIL corruption on power loss if a volatile out-of-order
101  * write cache is enabled.
102  */
103 boolean_t zil_nocacheflush = B_FALSE;
104 
105 /*
106  * Limit SLOG write size per commit executed with synchronous priority.
107  * Any writes above that will be executed with lower (asynchronous) priority
108  * to limit potential SLOG device abuse by single active ZIL writer.
109  */
110 uint64_t zil_slog_bulk = 768 * 1024;
111 
112 static kmem_cache_t *zil_lwb_cache;
113 static kmem_cache_t *zil_zcw_cache;
114 
115 static void zil_async_to_sync(zilog_t *zilog, uint64_t foid);
116 
117 #define	LWB_EMPTY(lwb) ((BP_GET_LSIZE(&lwb->lwb_blk) - \
118     sizeof (zil_chain_t)) == (lwb->lwb_sz - lwb->lwb_nused))
119 
120 static int
zil_bp_compare(const void * x1,const void * x2)121 zil_bp_compare(const void *x1, const void *x2)
122 {
123 	const dva_t *dva1 = &((zil_bp_node_t *)x1)->zn_dva;
124 	const dva_t *dva2 = &((zil_bp_node_t *)x2)->zn_dva;
125 
126 	int cmp = TREE_CMP(DVA_GET_VDEV(dva1), DVA_GET_VDEV(dva2));
127 	if (likely(cmp))
128 		return (cmp);
129 
130 	return (TREE_CMP(DVA_GET_OFFSET(dva1), DVA_GET_OFFSET(dva2)));
131 }
132 
133 static void
zil_bp_tree_init(zilog_t * zilog)134 zil_bp_tree_init(zilog_t *zilog)
135 {
136 	avl_create(&zilog->zl_bp_tree, zil_bp_compare,
137 	    sizeof (zil_bp_node_t), offsetof(zil_bp_node_t, zn_node));
138 }
139 
140 static void
zil_bp_tree_fini(zilog_t * zilog)141 zil_bp_tree_fini(zilog_t *zilog)
142 {
143 	avl_tree_t *t = &zilog->zl_bp_tree;
144 	zil_bp_node_t *zn;
145 	void *cookie = NULL;
146 
147 	while ((zn = avl_destroy_nodes(t, &cookie)) != NULL)
148 		kmem_free(zn, sizeof (zil_bp_node_t));
149 
150 	avl_destroy(t);
151 }
152 
153 int
zil_bp_tree_add(zilog_t * zilog,const blkptr_t * bp)154 zil_bp_tree_add(zilog_t *zilog, const blkptr_t *bp)
155 {
156 	avl_tree_t *t = &zilog->zl_bp_tree;
157 	const dva_t *dva;
158 	zil_bp_node_t *zn;
159 	avl_index_t where;
160 
161 	if (BP_IS_EMBEDDED(bp))
162 		return (0);
163 
164 	dva = BP_IDENTITY(bp);
165 
166 	if (avl_find(t, dva, &where) != NULL)
167 		return (SET_ERROR(EEXIST));
168 
169 	zn = kmem_alloc(sizeof (zil_bp_node_t), KM_SLEEP);
170 	zn->zn_dva = *dva;
171 	avl_insert(t, zn, where);
172 
173 	return (0);
174 }
175 
176 static zil_header_t *
zil_header_in_syncing_context(zilog_t * zilog)177 zil_header_in_syncing_context(zilog_t *zilog)
178 {
179 	return ((zil_header_t *)zilog->zl_header);
180 }
181 
182 static void
zil_init_log_chain(zilog_t * zilog,blkptr_t * bp)183 zil_init_log_chain(zilog_t *zilog, blkptr_t *bp)
184 {
185 	zio_cksum_t *zc = &bp->blk_cksum;
186 
187 	zc->zc_word[ZIL_ZC_GUID_0] = spa_get_random(-1ULL);
188 	zc->zc_word[ZIL_ZC_GUID_1] = spa_get_random(-1ULL);
189 	zc->zc_word[ZIL_ZC_OBJSET] = dmu_objset_id(zilog->zl_os);
190 	zc->zc_word[ZIL_ZC_SEQ] = 1ULL;
191 }
192 
193 /*
194  * Read a log block and make sure it's valid.
195  */
196 static int
zil_read_log_block(zilog_t * zilog,boolean_t decrypt,const blkptr_t * bp,blkptr_t * nbp,void * dst,char ** end)197 zil_read_log_block(zilog_t *zilog, boolean_t decrypt, const blkptr_t *bp,
198     blkptr_t *nbp, void *dst, char **end)
199 {
200 	enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
201 	arc_flags_t aflags = ARC_FLAG_WAIT;
202 	arc_buf_t *abuf = NULL;
203 	zbookmark_phys_t zb;
204 	int error;
205 
206 	if (zilog->zl_header->zh_claim_txg == 0)
207 		zio_flags |= ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB;
208 
209 	if (!(zilog->zl_header->zh_flags & ZIL_CLAIM_LR_SEQ_VALID))
210 		zio_flags |= ZIO_FLAG_SPECULATIVE;
211 
212 	if (!decrypt)
213 		zio_flags |= ZIO_FLAG_RAW;
214 
215 	SET_BOOKMARK(&zb, bp->blk_cksum.zc_word[ZIL_ZC_OBJSET],
216 	    ZB_ZIL_OBJECT, ZB_ZIL_LEVEL, bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
217 
218 	error = arc_read(NULL, zilog->zl_spa, bp, arc_getbuf_func,
219 	    &abuf, ZIO_PRIORITY_SYNC_READ, zio_flags, &aflags, &zb);
220 
221 	if (error == 0) {
222 		zio_cksum_t cksum = bp->blk_cksum;
223 
224 		/*
225 		 * Validate the checksummed log block.
226 		 *
227 		 * Sequence numbers should be... sequential.  The checksum
228 		 * verifier for the next block should be bp's checksum plus 1.
229 		 *
230 		 * Also check the log chain linkage and size used.
231 		 */
232 		cksum.zc_word[ZIL_ZC_SEQ]++;
233 
234 		if (BP_GET_CHECKSUM(bp) == ZIO_CHECKSUM_ZILOG2) {
235 			zil_chain_t *zilc = abuf->b_data;
236 			char *lr = (char *)(zilc + 1);
237 			uint64_t len = zilc->zc_nused - sizeof (zil_chain_t);
238 
239 			if (bcmp(&cksum, &zilc->zc_next_blk.blk_cksum,
240 			    sizeof (cksum)) || BP_IS_HOLE(&zilc->zc_next_blk)) {
241 				error = SET_ERROR(ECKSUM);
242 			} else {
243 				ASSERT3U(len, <=, SPA_OLD_MAXBLOCKSIZE);
244 				bcopy(lr, dst, len);
245 				*end = (char *)dst + len;
246 				*nbp = zilc->zc_next_blk;
247 			}
248 		} else {
249 			char *lr = abuf->b_data;
250 			uint64_t size = BP_GET_LSIZE(bp);
251 			zil_chain_t *zilc = (zil_chain_t *)(lr + size) - 1;
252 
253 			if (bcmp(&cksum, &zilc->zc_next_blk.blk_cksum,
254 			    sizeof (cksum)) || BP_IS_HOLE(&zilc->zc_next_blk) ||
255 			    (zilc->zc_nused > (size - sizeof (*zilc)))) {
256 				error = SET_ERROR(ECKSUM);
257 			} else {
258 				ASSERT3U(zilc->zc_nused, <=,
259 				    SPA_OLD_MAXBLOCKSIZE);
260 				bcopy(lr, dst, zilc->zc_nused);
261 				*end = (char *)dst + zilc->zc_nused;
262 				*nbp = zilc->zc_next_blk;
263 			}
264 		}
265 
266 		arc_buf_destroy(abuf, &abuf);
267 	}
268 
269 	return (error);
270 }
271 
272 /*
273  * Read a TX_WRITE log data block.
274  */
275 static int
zil_read_log_data(zilog_t * zilog,const lr_write_t * lr,void * wbuf)276 zil_read_log_data(zilog_t *zilog, const lr_write_t *lr, void *wbuf)
277 {
278 	enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
279 	const blkptr_t *bp = &lr->lr_blkptr;
280 	arc_flags_t aflags = ARC_FLAG_WAIT;
281 	arc_buf_t *abuf = NULL;
282 	zbookmark_phys_t zb;
283 	int error;
284 
285 	if (BP_IS_HOLE(bp)) {
286 		if (wbuf != NULL)
287 			bzero(wbuf, MAX(BP_GET_LSIZE(bp), lr->lr_length));
288 		return (0);
289 	}
290 
291 	if (zilog->zl_header->zh_claim_txg == 0)
292 		zio_flags |= ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB;
293 
294 	/*
295 	 * If we are not using the resulting data, we are just checking that
296 	 * it hasn't been corrupted so we don't need to waste CPU time
297 	 * decompressing and decrypting it.
298 	 */
299 	if (wbuf == NULL)
300 		zio_flags |= ZIO_FLAG_RAW;
301 
302 	SET_BOOKMARK(&zb, dmu_objset_id(zilog->zl_os), lr->lr_foid,
303 	    ZB_ZIL_LEVEL, lr->lr_offset / BP_GET_LSIZE(bp));
304 
305 	error = arc_read(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
306 	    ZIO_PRIORITY_SYNC_READ, zio_flags, &aflags, &zb);
307 
308 	if (error == 0) {
309 		if (wbuf != NULL)
310 			bcopy(abuf->b_data, wbuf, arc_buf_size(abuf));
311 		arc_buf_destroy(abuf, &abuf);
312 	}
313 
314 	return (error);
315 }
316 
317 /*
318  * Parse the intent log, and call parse_func for each valid record within.
319  */
320 int
zil_parse(zilog_t * zilog,zil_parse_blk_func_t * parse_blk_func,zil_parse_lr_func_t * parse_lr_func,void * arg,uint64_t txg,boolean_t decrypt)321 zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
322     zil_parse_lr_func_t *parse_lr_func, void *arg, uint64_t txg,
323     boolean_t decrypt)
324 {
325 	const zil_header_t *zh = zilog->zl_header;
326 	boolean_t claimed = !!zh->zh_claim_txg;
327 	uint64_t claim_blk_seq = claimed ? zh->zh_claim_blk_seq : UINT64_MAX;
328 	uint64_t claim_lr_seq = claimed ? zh->zh_claim_lr_seq : UINT64_MAX;
329 	uint64_t max_blk_seq = 0;
330 	uint64_t max_lr_seq = 0;
331 	uint64_t blk_count = 0;
332 	uint64_t lr_count = 0;
333 	blkptr_t blk, next_blk;
334 	char *lrbuf, *lrp;
335 	int error = 0;
336 
337 	/*
338 	 * Old logs didn't record the maximum zh_claim_lr_seq.
339 	 */
340 	if (!(zh->zh_flags & ZIL_CLAIM_LR_SEQ_VALID))
341 		claim_lr_seq = UINT64_MAX;
342 
343 	/*
344 	 * Starting at the block pointed to by zh_log we read the log chain.
345 	 * For each block in the chain we strongly check that block to
346 	 * ensure its validity.  We stop when an invalid block is found.
347 	 * For each block pointer in the chain we call parse_blk_func().
348 	 * For each record in each valid block we call parse_lr_func().
349 	 * If the log has been claimed, stop if we encounter a sequence
350 	 * number greater than the highest claimed sequence number.
351 	 */
352 	lrbuf = zio_buf_alloc(SPA_OLD_MAXBLOCKSIZE);
353 	zil_bp_tree_init(zilog);
354 
355 	for (blk = zh->zh_log; !BP_IS_HOLE(&blk); blk = next_blk) {
356 		uint64_t blk_seq = blk.blk_cksum.zc_word[ZIL_ZC_SEQ];
357 		int reclen;
358 		char *end;
359 
360 		if (blk_seq > claim_blk_seq)
361 			break;
362 
363 		error = parse_blk_func(zilog, &blk, arg, txg);
364 		if (error != 0)
365 			break;
366 		ASSERT3U(max_blk_seq, <, blk_seq);
367 		max_blk_seq = blk_seq;
368 		blk_count++;
369 
370 		if (max_lr_seq == claim_lr_seq && max_blk_seq == claim_blk_seq)
371 			break;
372 
373 		error = zil_read_log_block(zilog, decrypt, &blk, &next_blk,
374 		    lrbuf, &end);
375 		if (error != 0)
376 			break;
377 
378 		for (lrp = lrbuf; lrp < end; lrp += reclen) {
379 			lr_t *lr = (lr_t *)lrp;
380 			reclen = lr->lrc_reclen;
381 			ASSERT3U(reclen, >=, sizeof (lr_t));
382 			if (lr->lrc_seq > claim_lr_seq)
383 				goto done;
384 
385 			error = parse_lr_func(zilog, lr, arg, txg);
386 			if (error != 0)
387 				goto done;
388 			ASSERT3U(max_lr_seq, <, lr->lrc_seq);
389 			max_lr_seq = lr->lrc_seq;
390 			lr_count++;
391 		}
392 	}
393 done:
394 	zilog->zl_parse_error = error;
395 	zilog->zl_parse_blk_seq = max_blk_seq;
396 	zilog->zl_parse_lr_seq = max_lr_seq;
397 	zilog->zl_parse_blk_count = blk_count;
398 	zilog->zl_parse_lr_count = lr_count;
399 
400 	ASSERT(!claimed || !(zh->zh_flags & ZIL_CLAIM_LR_SEQ_VALID) ||
401 	    (max_blk_seq == claim_blk_seq && max_lr_seq == claim_lr_seq) ||
402 	    (decrypt && error == EIO));
403 
404 	zil_bp_tree_fini(zilog);
405 	zio_buf_free(lrbuf, SPA_OLD_MAXBLOCKSIZE);
406 
407 	return (error);
408 }
409 
410 /* ARGSUSED */
411 static int
zil_clear_log_block(zilog_t * zilog,blkptr_t * bp,void * tx,uint64_t first_txg)412 zil_clear_log_block(zilog_t *zilog, blkptr_t *bp, void *tx, uint64_t first_txg)
413 {
414 	ASSERT(!BP_IS_HOLE(bp));
415 
416 	/*
417 	 * As we call this function from the context of a rewind to a
418 	 * checkpoint, each ZIL block whose txg is later than the txg
419 	 * that we rewind to is invalid. Thus, we return -1 so
420 	 * zil_parse() doesn't attempt to read it.
421 	 */
422 	if (bp->blk_birth >= first_txg)
423 		return (-1);
424 
425 	if (zil_bp_tree_add(zilog, bp) != 0)
426 		return (0);
427 
428 	zio_free(zilog->zl_spa, first_txg, bp);
429 	return (0);
430 }
431 
432 /* ARGSUSED */
433 static int
zil_noop_log_record(zilog_t * zilog,lr_t * lrc,void * tx,uint64_t first_txg)434 zil_noop_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t first_txg)
435 {
436 	return (0);
437 }
438 
439 static int
zil_claim_log_block(zilog_t * zilog,blkptr_t * bp,void * tx,uint64_t first_txg)440 zil_claim_log_block(zilog_t *zilog, blkptr_t *bp, void *tx, uint64_t first_txg)
441 {
442 	/*
443 	 * Claim log block if not already committed and not already claimed.
444 	 * If tx == NULL, just verify that the block is claimable.
445 	 */
446 	if (BP_IS_HOLE(bp) || bp->blk_birth < first_txg ||
447 	    zil_bp_tree_add(zilog, bp) != 0)
448 		return (0);
449 
450 	return (zio_wait(zio_claim(NULL, zilog->zl_spa,
451 	    tx == NULL ? 0 : first_txg, bp, spa_claim_notify, NULL,
452 	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB)));
453 }
454 
455 static int
zil_claim_log_record(zilog_t * zilog,lr_t * lrc,void * tx,uint64_t first_txg)456 zil_claim_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t first_txg)
457 {
458 	lr_write_t *lr = (lr_write_t *)lrc;
459 	int error;
460 
461 	if (lrc->lrc_txtype != TX_WRITE)
462 		return (0);
463 
464 	/*
465 	 * If the block is not readable, don't claim it.  This can happen
466 	 * in normal operation when a log block is written to disk before
467 	 * some of the dmu_sync() blocks it points to.  In this case, the
468 	 * transaction cannot have been committed to anyone (we would have
469 	 * waited for all writes to be stable first), so it is semantically
470 	 * correct to declare this the end of the log.
471 	 */
472 	if (lr->lr_blkptr.blk_birth >= first_txg) {
473 		error = zil_read_log_data(zilog, lr, NULL);
474 		if (error != 0)
475 			return (error);
476 	}
477 
478 	return (zil_claim_log_block(zilog, &lr->lr_blkptr, tx, first_txg));
479 }
480 
481 /* ARGSUSED */
482 static int
zil_free_log_block(zilog_t * zilog,blkptr_t * bp,void * tx,uint64_t claim_txg)483 zil_free_log_block(zilog_t *zilog, blkptr_t *bp, void *tx, uint64_t claim_txg)
484 {
485 	zio_free(zilog->zl_spa, dmu_tx_get_txg(tx), bp);
486 
487 	return (0);
488 }
489 
490 static int
zil_free_log_record(zilog_t * zilog,lr_t * lrc,void * tx,uint64_t claim_txg)491 zil_free_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t claim_txg)
492 {
493 	lr_write_t *lr = (lr_write_t *)lrc;
494 	blkptr_t *bp = &lr->lr_blkptr;
495 
496 	/*
497 	 * If we previously claimed it, we need to free it.
498 	 */
499 	if (claim_txg != 0 && lrc->lrc_txtype == TX_WRITE &&
500 	    bp->blk_birth >= claim_txg && zil_bp_tree_add(zilog, bp) == 0 &&
501 	    !BP_IS_HOLE(bp))
502 		zio_free(zilog->zl_spa, dmu_tx_get_txg(tx), bp);
503 
504 	return (0);
505 }
506 
507 static int
zil_lwb_vdev_compare(const void * x1,const void * x2)508 zil_lwb_vdev_compare(const void *x1, const void *x2)
509 {
510 	const uint64_t v1 = ((zil_vdev_node_t *)x1)->zv_vdev;
511 	const uint64_t v2 = ((zil_vdev_node_t *)x2)->zv_vdev;
512 
513 	return (TREE_CMP(v1, v2));
514 }
515 
516 static lwb_t *
zil_alloc_lwb(zilog_t * zilog,blkptr_t * bp,boolean_t slog,uint64_t txg)517 zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, boolean_t slog, uint64_t txg)
518 {
519 	lwb_t *lwb;
520 
521 	lwb = kmem_cache_alloc(zil_lwb_cache, KM_SLEEP);
522 	lwb->lwb_zilog = zilog;
523 	lwb->lwb_blk = *bp;
524 	lwb->lwb_slog = slog;
525 	lwb->lwb_state = LWB_STATE_CLOSED;
526 	lwb->lwb_buf = zio_buf_alloc(BP_GET_LSIZE(bp));
527 	lwb->lwb_max_txg = txg;
528 	lwb->lwb_write_zio = NULL;
529 	lwb->lwb_root_zio = NULL;
530 	lwb->lwb_tx = NULL;
531 	lwb->lwb_issued_timestamp = 0;
532 	if (BP_GET_CHECKSUM(bp) == ZIO_CHECKSUM_ZILOG2) {
533 		lwb->lwb_nused = sizeof (zil_chain_t);
534 		lwb->lwb_sz = BP_GET_LSIZE(bp);
535 	} else {
536 		lwb->lwb_nused = 0;
537 		lwb->lwb_sz = BP_GET_LSIZE(bp) - sizeof (zil_chain_t);
538 	}
539 
540 	mutex_enter(&zilog->zl_lock);
541 	list_insert_tail(&zilog->zl_lwb_list, lwb);
542 	mutex_exit(&zilog->zl_lock);
543 
544 	ASSERT(!MUTEX_HELD(&lwb->lwb_vdev_lock));
545 	ASSERT(avl_is_empty(&lwb->lwb_vdev_tree));
546 	VERIFY(list_is_empty(&lwb->lwb_waiters));
547 
548 	return (lwb);
549 }
550 
551 static void
zil_free_lwb(zilog_t * zilog,lwb_t * lwb)552 zil_free_lwb(zilog_t *zilog, lwb_t *lwb)
553 {
554 	ASSERT(MUTEX_HELD(&zilog->zl_lock));
555 	ASSERT(!MUTEX_HELD(&lwb->lwb_vdev_lock));
556 	VERIFY(list_is_empty(&lwb->lwb_waiters));
557 	ASSERT(avl_is_empty(&lwb->lwb_vdev_tree));
558 	ASSERT3P(lwb->lwb_write_zio, ==, NULL);
559 	ASSERT3P(lwb->lwb_root_zio, ==, NULL);
560 	ASSERT3U(lwb->lwb_max_txg, <=, spa_syncing_txg(zilog->zl_spa));
561 	ASSERT(lwb->lwb_state == LWB_STATE_CLOSED ||
562 	    lwb->lwb_state == LWB_STATE_FLUSH_DONE);
563 
564 	/*
565 	 * Clear the zilog's field to indicate this lwb is no longer
566 	 * valid, and prevent use-after-free errors.
567 	 */
568 	if (zilog->zl_last_lwb_opened == lwb)
569 		zilog->zl_last_lwb_opened = NULL;
570 
571 	kmem_cache_free(zil_lwb_cache, lwb);
572 }
573 
574 /*
575  * Called when we create in-memory log transactions so that we know
576  * to cleanup the itxs at the end of spa_sync().
577  */
578 void
zilog_dirty(zilog_t * zilog,uint64_t txg)579 zilog_dirty(zilog_t *zilog, uint64_t txg)
580 {
581 	dsl_pool_t *dp = zilog->zl_dmu_pool;
582 	dsl_dataset_t *ds = dmu_objset_ds(zilog->zl_os);
583 
584 	ASSERT(spa_writeable(zilog->zl_spa));
585 
586 	if (ds->ds_is_snapshot)
587 		panic("dirtying snapshot!");
588 
589 	if (txg_list_add(&dp->dp_dirty_zilogs, zilog, txg)) {
590 		/* up the hold count until we can be written out */
591 		dmu_buf_add_ref(ds->ds_dbuf, zilog);
592 
593 		zilog->zl_dirty_max_txg = MAX(txg, zilog->zl_dirty_max_txg);
594 	}
595 }
596 
597 /*
598  * Determine if the zil is dirty in the specified txg. Callers wanting to
599  * ensure that the dirty state does not change must hold the itxg_lock for
600  * the specified txg. Holding the lock will ensure that the zil cannot be
601  * dirtied (zil_itx_assign) or cleaned (zil_clean) while we check its current
602  * state.
603  */
604 boolean_t
zilog_is_dirty_in_txg(zilog_t * zilog,uint64_t txg)605 zilog_is_dirty_in_txg(zilog_t *zilog, uint64_t txg)
606 {
607 	dsl_pool_t *dp = zilog->zl_dmu_pool;
608 
609 	if (txg_list_member(&dp->dp_dirty_zilogs, zilog, txg & TXG_MASK))
610 		return (B_TRUE);
611 	return (B_FALSE);
612 }
613 
614 /*
615  * Determine if the zil is dirty. The zil is considered dirty if it has
616  * any pending itx records that have not been cleaned by zil_clean().
617  */
618 boolean_t
zilog_is_dirty(zilog_t * zilog)619 zilog_is_dirty(zilog_t *zilog)
620 {
621 	dsl_pool_t *dp = zilog->zl_dmu_pool;
622 
623 	for (int t = 0; t < TXG_SIZE; t++) {
624 		if (txg_list_member(&dp->dp_dirty_zilogs, zilog, t))
625 			return (B_TRUE);
626 	}
627 	return (B_FALSE);
628 }
629 
630 /*
631  * Create an on-disk intent log.
632  */
633 static lwb_t *
zil_create(zilog_t * zilog)634 zil_create(zilog_t *zilog)
635 {
636 	const zil_header_t *zh = zilog->zl_header;
637 	lwb_t *lwb = NULL;
638 	uint64_t txg = 0;
639 	dmu_tx_t *tx = NULL;
640 	blkptr_t blk;
641 	int error = 0;
642 	boolean_t slog = FALSE;
643 
644 	/*
645 	 * Wait for any previous destroy to complete.
646 	 */
647 	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
648 
649 	ASSERT(zh->zh_claim_txg == 0);
650 	ASSERT(zh->zh_replay_seq == 0);
651 
652 	blk = zh->zh_log;
653 
654 	/*
655 	 * Allocate an initial log block if:
656 	 *    - there isn't one already
657 	 *    - the existing block is the wrong endianess
658 	 */
659 	if (BP_IS_HOLE(&blk) || BP_SHOULD_BYTESWAP(&blk)) {
660 		tx = dmu_tx_create(zilog->zl_os);
661 		VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
662 		dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
663 		txg = dmu_tx_get_txg(tx);
664 
665 		if (!BP_IS_HOLE(&blk)) {
666 			zio_free(zilog->zl_spa, txg, &blk);
667 			BP_ZERO(&blk);
668 		}
669 
670 		error = zio_alloc_zil(zilog->zl_spa, zilog->zl_os, txg, &blk,
671 		    NULL, ZIL_MIN_BLKSZ, &slog);
672 
673 		if (error == 0)
674 			zil_init_log_chain(zilog, &blk);
675 	}
676 
677 	/*
678 	 * Allocate a log write block (lwb) for the first log block.
679 	 */
680 	if (error == 0)
681 		lwb = zil_alloc_lwb(zilog, &blk, slog, txg);
682 
683 	/*
684 	 * If we just allocated the first log block, commit our transaction
685 	 * and wait for zil_sync() to stuff the block poiner into zh_log.
686 	 * (zh is part of the MOS, so we cannot modify it in open context.)
687 	 */
688 	if (tx != NULL) {
689 		dmu_tx_commit(tx);
690 		txg_wait_synced(zilog->zl_dmu_pool, txg);
691 	}
692 
693 	ASSERT(bcmp(&blk, &zh->zh_log, sizeof (blk)) == 0);
694 
695 	return (lwb);
696 }
697 
698 /*
699  * In one tx, free all log blocks and clear the log header. If keep_first
700  * is set, then we're replaying a log with no content. We want to keep the
701  * first block, however, so that the first synchronous transaction doesn't
702  * require a txg_wait_synced() in zil_create(). We don't need to
703  * txg_wait_synced() here either when keep_first is set, because both
704  * zil_create() and zil_destroy() will wait for any in-progress destroys
705  * to complete.
706  */
707 void
zil_destroy(zilog_t * zilog,boolean_t keep_first)708 zil_destroy(zilog_t *zilog, boolean_t keep_first)
709 {
710 	const zil_header_t *zh = zilog->zl_header;
711 	lwb_t *lwb;
712 	dmu_tx_t *tx;
713 	uint64_t txg;
714 
715 	/*
716 	 * Wait for any previous destroy to complete.
717 	 */
718 	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
719 
720 	zilog->zl_old_header = *zh;		/* debugging aid */
721 
722 	if (BP_IS_HOLE(&zh->zh_log))
723 		return;
724 
725 	tx = dmu_tx_create(zilog->zl_os);
726 	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
727 	dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
728 	txg = dmu_tx_get_txg(tx);
729 
730 	mutex_enter(&zilog->zl_lock);
731 
732 	ASSERT3U(zilog->zl_destroy_txg, <, txg);
733 	zilog->zl_destroy_txg = txg;
734 	zilog->zl_keep_first = keep_first;
735 
736 	if (!list_is_empty(&zilog->zl_lwb_list)) {
737 		ASSERT(zh->zh_claim_txg == 0);
738 		VERIFY(!keep_first);
739 		while ((lwb = list_head(&zilog->zl_lwb_list)) != NULL) {
740 			list_remove(&zilog->zl_lwb_list, lwb);
741 			if (lwb->lwb_buf != NULL)
742 				zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
743 			zio_free(zilog->zl_spa, txg, &lwb->lwb_blk);
744 			zil_free_lwb(zilog, lwb);
745 		}
746 	} else if (!keep_first) {
747 		zil_destroy_sync(zilog, tx);
748 	}
749 	mutex_exit(&zilog->zl_lock);
750 
751 	dmu_tx_commit(tx);
752 }
753 
754 void
zil_destroy_sync(zilog_t * zilog,dmu_tx_t * tx)755 zil_destroy_sync(zilog_t *zilog, dmu_tx_t *tx)
756 {
757 	ASSERT(list_is_empty(&zilog->zl_lwb_list));
758 	(void) zil_parse(zilog, zil_free_log_block,
759 	    zil_free_log_record, tx, zilog->zl_header->zh_claim_txg, B_FALSE);
760 }
761 
762 int
zil_claim(dsl_pool_t * dp,dsl_dataset_t * ds,void * txarg)763 zil_claim(dsl_pool_t *dp, dsl_dataset_t *ds, void *txarg)
764 {
765 	dmu_tx_t *tx = txarg;
766 	zilog_t *zilog;
767 	uint64_t first_txg;
768 	zil_header_t *zh;
769 	objset_t *os;
770 	int error;
771 
772 	error = dmu_objset_own_obj(dp, ds->ds_object,
773 	    DMU_OST_ANY, B_FALSE, B_FALSE, FTAG, &os);
774 	if (error != 0) {
775 		/*
776 		 * EBUSY indicates that the objset is inconsistent, in which
777 		 * case it can not have a ZIL.
778 		 */
779 		if (error != EBUSY) {
780 			cmn_err(CE_WARN, "can't open objset for %llu, error %u",
781 			    (unsigned long long)ds->ds_object, error);
782 		}
783 		return (0);
784 	}
785 
786 	zilog = dmu_objset_zil(os);
787 	zh = zil_header_in_syncing_context(zilog);
788 	ASSERT3U(tx->tx_txg, ==, spa_first_txg(zilog->zl_spa));
789 	first_txg = spa_min_claim_txg(zilog->zl_spa);
790 
791 	/*
792 	 * If the spa_log_state is not set to be cleared, check whether
793 	 * the current uberblock is a checkpoint one and if the current
794 	 * header has been claimed before moving on.
795 	 *
796 	 * If the current uberblock is a checkpointed uberblock then
797 	 * one of the following scenarios took place:
798 	 *
799 	 * 1] We are currently rewinding to the checkpoint of the pool.
800 	 * 2] We crashed in the middle of a checkpoint rewind but we
801 	 *    did manage to write the checkpointed uberblock to the
802 	 *    vdev labels, so when we tried to import the pool again
803 	 *    the checkpointed uberblock was selected from the import
804 	 *    procedure.
805 	 *
806 	 * In both cases we want to zero out all the ZIL blocks, except
807 	 * the ones that have been claimed at the time of the checkpoint
808 	 * (their zh_claim_txg != 0). The reason is that these blocks
809 	 * may be corrupted since we may have reused their locations on
810 	 * disk after we took the checkpoint.
811 	 *
812 	 * We could try to set spa_log_state to SPA_LOG_CLEAR earlier
813 	 * when we first figure out whether the current uberblock is
814 	 * checkpointed or not. Unfortunately, that would discard all
815 	 * the logs, including the ones that are claimed, and we would
816 	 * leak space.
817 	 */
818 	if (spa_get_log_state(zilog->zl_spa) == SPA_LOG_CLEAR ||
819 	    (zilog->zl_spa->spa_uberblock.ub_checkpoint_txg != 0 &&
820 	    zh->zh_claim_txg == 0)) {
821 		if (!BP_IS_HOLE(&zh->zh_log)) {
822 			(void) zil_parse(zilog, zil_clear_log_block,
823 			    zil_noop_log_record, tx, first_txg, B_FALSE);
824 		}
825 		BP_ZERO(&zh->zh_log);
826 		if (os->os_encrypted)
827 			os->os_next_write_raw[tx->tx_txg & TXG_MASK] = B_TRUE;
828 		dsl_dataset_dirty(dmu_objset_ds(os), tx);
829 		dmu_objset_disown(os, B_FALSE, FTAG);
830 		return (0);
831 	}
832 
833 	/*
834 	 * If we are not rewinding and opening the pool normally, then
835 	 * the min_claim_txg should be equal to the first txg of the pool.
836 	 */
837 	ASSERT3U(first_txg, ==, spa_first_txg(zilog->zl_spa));
838 
839 	/*
840 	 * Claim all log blocks if we haven't already done so, and remember
841 	 * the highest claimed sequence number.  This ensures that if we can
842 	 * read only part of the log now (e.g. due to a missing device),
843 	 * but we can read the entire log later, we will not try to replay
844 	 * or destroy beyond the last block we successfully claimed.
845 	 */
846 	ASSERT3U(zh->zh_claim_txg, <=, first_txg);
847 	if (zh->zh_claim_txg == 0 && !BP_IS_HOLE(&zh->zh_log)) {
848 		(void) zil_parse(zilog, zil_claim_log_block,
849 		    zil_claim_log_record, tx, first_txg, B_FALSE);
850 		zh->zh_claim_txg = first_txg;
851 		zh->zh_claim_blk_seq = zilog->zl_parse_blk_seq;
852 		zh->zh_claim_lr_seq = zilog->zl_parse_lr_seq;
853 		if (zilog->zl_parse_lr_count || zilog->zl_parse_blk_count > 1)
854 			zh->zh_flags |= ZIL_REPLAY_NEEDED;
855 		zh->zh_flags |= ZIL_CLAIM_LR_SEQ_VALID;
856 		if (os->os_encrypted)
857 			os->os_next_write_raw[tx->tx_txg & TXG_MASK] = B_TRUE;
858 		dsl_dataset_dirty(dmu_objset_ds(os), tx);
859 	}
860 
861 	ASSERT3U(first_txg, ==, (spa_last_synced_txg(zilog->zl_spa) + 1));
862 	dmu_objset_disown(os, B_FALSE, FTAG);
863 	return (0);
864 }
865 
866 /*
867  * Check the log by walking the log chain.
868  * Checksum errors are ok as they indicate the end of the chain.
869  * Any other error (no device or read failure) returns an error.
870  */
871 /* ARGSUSED */
872 int
zil_check_log_chain(dsl_pool_t * dp,dsl_dataset_t * ds,void * tx)873 zil_check_log_chain(dsl_pool_t *dp, dsl_dataset_t *ds, void *tx)
874 {
875 	zilog_t *zilog;
876 	objset_t *os;
877 	blkptr_t *bp;
878 	int error;
879 
880 	ASSERT(tx == NULL);
881 
882 	error = dmu_objset_from_ds(ds, &os);
883 	if (error != 0) {
884 		cmn_err(CE_WARN, "can't open objset %llu, error %d",
885 		    (unsigned long long)ds->ds_object, error);
886 		return (0);
887 	}
888 
889 	zilog = dmu_objset_zil(os);
890 	bp = (blkptr_t *)&zilog->zl_header->zh_log;
891 
892 	if (!BP_IS_HOLE(bp)) {
893 		vdev_t *vd;
894 		boolean_t valid = B_TRUE;
895 
896 		/*
897 		 * Check the first block and determine if it's on a log device
898 		 * which may have been removed or faulted prior to loading this
899 		 * pool.  If so, there's no point in checking the rest of the
900 		 * log as its content should have already been synced to the
901 		 * pool.
902 		 */
903 		spa_config_enter(os->os_spa, SCL_STATE, FTAG, RW_READER);
904 		vd = vdev_lookup_top(os->os_spa, DVA_GET_VDEV(&bp->blk_dva[0]));
905 		if (vd->vdev_islog && vdev_is_dead(vd))
906 			valid = vdev_log_state_valid(vd);
907 		spa_config_exit(os->os_spa, SCL_STATE, FTAG);
908 
909 		if (!valid)
910 			return (0);
911 
912 		/*
913 		 * Check whether the current uberblock is checkpointed (e.g.
914 		 * we are rewinding) and whether the current header has been
915 		 * claimed or not. If it hasn't then skip verifying it. We
916 		 * do this because its ZIL blocks may be part of the pool's
917 		 * state before the rewind, which is no longer valid.
918 		 */
919 		zil_header_t *zh = zil_header_in_syncing_context(zilog);
920 		if (zilog->zl_spa->spa_uberblock.ub_checkpoint_txg != 0 &&
921 		    zh->zh_claim_txg == 0)
922 			return (0);
923 	}
924 
925 	/*
926 	 * Because tx == NULL, zil_claim_log_block() will not actually claim
927 	 * any blocks, but just determine whether it is possible to do so.
928 	 * In addition to checking the log chain, zil_claim_log_block()
929 	 * will invoke zio_claim() with a done func of spa_claim_notify(),
930 	 * which will update spa_max_claim_txg.  See spa_load() for details.
931 	 */
932 	error = zil_parse(zilog, zil_claim_log_block, zil_claim_log_record, tx,
933 	    zilog->zl_header->zh_claim_txg ? -1ULL :
934 	    spa_min_claim_txg(os->os_spa), B_FALSE);
935 
936 	return ((error == ECKSUM || error == ENOENT) ? 0 : error);
937 }
938 
939 /*
940  * When an itx is "skipped", this function is used to properly mark the
941  * waiter as "done, and signal any thread(s) waiting on it. An itx can
942  * be skipped (and not committed to an lwb) for a variety of reasons,
943  * one of them being that the itx was committed via spa_sync(), prior to
944  * it being committed to an lwb; this can happen if a thread calling
945  * zil_commit() is racing with spa_sync().
946  */
947 static void
zil_commit_waiter_skip(zil_commit_waiter_t * zcw)948 zil_commit_waiter_skip(zil_commit_waiter_t *zcw)
949 {
950 	mutex_enter(&zcw->zcw_lock);
951 	ASSERT3B(zcw->zcw_done, ==, B_FALSE);
952 	zcw->zcw_done = B_TRUE;
953 	cv_broadcast(&zcw->zcw_cv);
954 	mutex_exit(&zcw->zcw_lock);
955 }
956 
957 /*
958  * This function is used when the given waiter is to be linked into an
959  * lwb's "lwb_waiter" list; i.e. when the itx is committed to the lwb.
960  * At this point, the waiter will no longer be referenced by the itx,
961  * and instead, will be referenced by the lwb.
962  */
963 static void
zil_commit_waiter_link_lwb(zil_commit_waiter_t * zcw,lwb_t * lwb)964 zil_commit_waiter_link_lwb(zil_commit_waiter_t *zcw, lwb_t *lwb)
965 {
966 	/*
967 	 * The lwb_waiters field of the lwb is protected by the zilog's
968 	 * zl_lock, thus it must be held when calling this function.
969 	 */
970 	ASSERT(MUTEX_HELD(&lwb->lwb_zilog->zl_lock));
971 
972 	mutex_enter(&zcw->zcw_lock);
973 	ASSERT(!list_link_active(&zcw->zcw_node));
974 	ASSERT3P(zcw->zcw_lwb, ==, NULL);
975 	ASSERT3P(lwb, !=, NULL);
976 	ASSERT(lwb->lwb_state == LWB_STATE_OPENED ||
977 	    lwb->lwb_state == LWB_STATE_ISSUED ||
978 	    lwb->lwb_state == LWB_STATE_WRITE_DONE);
979 
980 	list_insert_tail(&lwb->lwb_waiters, zcw);
981 	zcw->zcw_lwb = lwb;
982 	mutex_exit(&zcw->zcw_lock);
983 }
984 
985 /*
986  * This function is used when zio_alloc_zil() fails to allocate a ZIL
987  * block, and the given waiter must be linked to the "nolwb waiters"
988  * list inside of zil_process_commit_list().
989  */
990 static void
zil_commit_waiter_link_nolwb(zil_commit_waiter_t * zcw,list_t * nolwb)991 zil_commit_waiter_link_nolwb(zil_commit_waiter_t *zcw, list_t *nolwb)
992 {
993 	mutex_enter(&zcw->zcw_lock);
994 	ASSERT(!list_link_active(&zcw->zcw_node));
995 	ASSERT3P(zcw->zcw_lwb, ==, NULL);
996 	list_insert_tail(nolwb, zcw);
997 	mutex_exit(&zcw->zcw_lock);
998 }
999 
1000 void
zil_lwb_add_block(lwb_t * lwb,const blkptr_t * bp)1001 zil_lwb_add_block(lwb_t *lwb, const blkptr_t *bp)
1002 {
1003 	avl_tree_t *t = &lwb->lwb_vdev_tree;
1004 	avl_index_t where;
1005 	zil_vdev_node_t *zv, zvsearch;
1006 	int ndvas = BP_GET_NDVAS(bp);
1007 	int i;
1008 
1009 	if (zil_nocacheflush)
1010 		return;
1011 
1012 	mutex_enter(&lwb->lwb_vdev_lock);
1013 	for (i = 0; i < ndvas; i++) {
1014 		zvsearch.zv_vdev = DVA_GET_VDEV(&bp->blk_dva[i]);
1015 		if (avl_find(t, &zvsearch, &where) == NULL) {
1016 			zv = kmem_alloc(sizeof (*zv), KM_SLEEP);
1017 			zv->zv_vdev = zvsearch.zv_vdev;
1018 			avl_insert(t, zv, where);
1019 		}
1020 	}
1021 	mutex_exit(&lwb->lwb_vdev_lock);
1022 }
1023 
1024 static void
zil_lwb_flush_defer(lwb_t * lwb,lwb_t * nlwb)1025 zil_lwb_flush_defer(lwb_t *lwb, lwb_t *nlwb)
1026 {
1027 	avl_tree_t *src = &lwb->lwb_vdev_tree;
1028 	avl_tree_t *dst = &nlwb->lwb_vdev_tree;
1029 	void *cookie = NULL;
1030 	zil_vdev_node_t *zv;
1031 
1032 	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_WRITE_DONE);
1033 	ASSERT3S(nlwb->lwb_state, !=, LWB_STATE_WRITE_DONE);
1034 	ASSERT3S(nlwb->lwb_state, !=, LWB_STATE_FLUSH_DONE);
1035 
1036 	/*
1037 	 * While 'lwb' is at a point in its lifetime where lwb_vdev_tree does
1038 	 * not need the protection of lwb_vdev_lock (it will only be modified
1039 	 * while holding zilog->zl_lock) as its writes and those of its
1040 	 * children have all completed.  The younger 'nlwb' may be waiting on
1041 	 * future writes to additional vdevs.
1042 	 */
1043 	mutex_enter(&nlwb->lwb_vdev_lock);
1044 	/*
1045 	 * Tear down the 'lwb' vdev tree, ensuring that entries which do not
1046 	 * exist in 'nlwb' are moved to it, freeing any would-be duplicates.
1047 	 */
1048 	while ((zv = avl_destroy_nodes(src, &cookie)) != NULL) {
1049 		avl_index_t where;
1050 
1051 		if (avl_find(dst, zv, &where) == NULL) {
1052 			avl_insert(dst, zv, where);
1053 		} else {
1054 			kmem_free(zv, sizeof (*zv));
1055 		}
1056 	}
1057 	mutex_exit(&nlwb->lwb_vdev_lock);
1058 }
1059 
1060 void
zil_lwb_add_txg(lwb_t * lwb,uint64_t txg)1061 zil_lwb_add_txg(lwb_t *lwb, uint64_t txg)
1062 {
1063 	lwb->lwb_max_txg = MAX(lwb->lwb_max_txg, txg);
1064 }
1065 
1066 /*
1067  * This function is a called after all vdevs associated with a given lwb
1068  * write have completed their DKIOCFLUSHWRITECACHE command; or as soon
1069  * as the lwb write completes, if "zil_nocacheflush" is set. Further,
1070  * all "previous" lwb's will have completed before this function is
1071  * called; i.e. this function is called for all previous lwbs before
1072  * it's called for "this" lwb (enforced via zio the dependencies
1073  * configured in zil_lwb_set_zio_dependency()).
1074  *
1075  * The intention is for this function to be called as soon as the
1076  * contents of an lwb are considered "stable" on disk, and will survive
1077  * any sudden loss of power. At this point, any threads waiting for the
1078  * lwb to reach this state are signalled, and the "waiter" structures
1079  * are marked "done".
1080  */
1081 static void
zil_lwb_flush_vdevs_done(zio_t * zio)1082 zil_lwb_flush_vdevs_done(zio_t *zio)
1083 {
1084 	lwb_t *lwb = zio->io_private;
1085 	zilog_t *zilog = lwb->lwb_zilog;
1086 	dmu_tx_t *tx = lwb->lwb_tx;
1087 	zil_commit_waiter_t *zcw;
1088 
1089 	spa_config_exit(zilog->zl_spa, SCL_STATE, lwb);
1090 
1091 	zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
1092 
1093 	mutex_enter(&zilog->zl_lock);
1094 
1095 	/*
1096 	 * Ensure the lwb buffer pointer is cleared before releasing the
1097 	 * txg. If we have had an allocation failure and the txg is
1098 	 * waiting to sync then we want zil_sync() to remove the lwb so
1099 	 * that it's not picked up as the next new one in
1100 	 * zil_process_commit_list(). zil_sync() will only remove the
1101 	 * lwb if lwb_buf is null.
1102 	 */
1103 	lwb->lwb_buf = NULL;
1104 	lwb->lwb_tx = NULL;
1105 
1106 	ASSERT3U(lwb->lwb_issued_timestamp, >, 0);
1107 	zilog->zl_last_lwb_latency = gethrtime() - lwb->lwb_issued_timestamp;
1108 
1109 	lwb->lwb_root_zio = NULL;
1110 
1111 	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_WRITE_DONE);
1112 	lwb->lwb_state = LWB_STATE_FLUSH_DONE;
1113 
1114 	if (zilog->zl_last_lwb_opened == lwb) {
1115 		/*
1116 		 * Remember the highest committed log sequence number
1117 		 * for ztest. We only update this value when all the log
1118 		 * writes succeeded, because ztest wants to ASSERT that
1119 		 * it got the whole log chain.
1120 		 */
1121 		zilog->zl_commit_lr_seq = zilog->zl_lr_seq;
1122 	}
1123 
1124 	while ((zcw = list_head(&lwb->lwb_waiters)) != NULL) {
1125 		mutex_enter(&zcw->zcw_lock);
1126 
1127 		ASSERT(list_link_active(&zcw->zcw_node));
1128 		list_remove(&lwb->lwb_waiters, zcw);
1129 
1130 		ASSERT3P(zcw->zcw_lwb, ==, lwb);
1131 		zcw->zcw_lwb = NULL;
1132 
1133 		zcw->zcw_zio_error = zio->io_error;
1134 
1135 		ASSERT3B(zcw->zcw_done, ==, B_FALSE);
1136 		zcw->zcw_done = B_TRUE;
1137 		cv_broadcast(&zcw->zcw_cv);
1138 
1139 		mutex_exit(&zcw->zcw_lock);
1140 	}
1141 
1142 	mutex_exit(&zilog->zl_lock);
1143 
1144 	/*
1145 	 * Now that we've written this log block, we have a stable pointer
1146 	 * to the next block in the chain, so it's OK to let the txg in
1147 	 * which we allocated the next block sync.
1148 	 */
1149 	dmu_tx_commit(tx);
1150 }
1151 
1152 /*
1153  * This is called when an lwb's write zio completes. The callback's
1154  * purpose is to issue the DKIOCFLUSHWRITECACHE commands for the vdevs
1155  * in the lwb's lwb_vdev_tree. The tree will contain the vdevs involved
1156  * in writing out this specific lwb's data, and in the case that cache
1157  * flushes have been deferred, vdevs involved in writing the data for
1158  * previous lwbs. The writes corresponding to all the vdevs in the
1159  * lwb_vdev_tree will have completed by the time this is called, due to
1160  * the zio dependencies configured in zil_lwb_set_zio_dependency(),
1161  * which takes deferred flushes into account. The lwb will be "done"
1162  * once zil_lwb_flush_vdevs_done() is called, which occurs in the zio
1163  * completion callback for the lwb's root zio.
1164  */
1165 static void
zil_lwb_write_done(zio_t * zio)1166 zil_lwb_write_done(zio_t *zio)
1167 {
1168 	lwb_t *lwb = zio->io_private;
1169 	spa_t *spa = zio->io_spa;
1170 	zilog_t *zilog = lwb->lwb_zilog;
1171 	avl_tree_t *t = &lwb->lwb_vdev_tree;
1172 	void *cookie = NULL;
1173 	zil_vdev_node_t *zv;
1174 	lwb_t *nlwb;
1175 
1176 	ASSERT3S(spa_config_held(spa, SCL_STATE, RW_READER), !=, 0);
1177 
1178 	ASSERT(BP_GET_COMPRESS(zio->io_bp) == ZIO_COMPRESS_OFF);
1179 	ASSERT(BP_GET_TYPE(zio->io_bp) == DMU_OT_INTENT_LOG);
1180 	ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
1181 	ASSERT(BP_GET_BYTEORDER(zio->io_bp) == ZFS_HOST_BYTEORDER);
1182 	ASSERT(!BP_IS_GANG(zio->io_bp));
1183 	ASSERT(!BP_IS_HOLE(zio->io_bp));
1184 	ASSERT(BP_GET_FILL(zio->io_bp) == 0);
1185 
1186 	abd_put(zio->io_abd);
1187 
1188 	mutex_enter(&zilog->zl_lock);
1189 	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_ISSUED);
1190 	lwb->lwb_state = LWB_STATE_WRITE_DONE;
1191 	lwb->lwb_write_zio = NULL;
1192 	nlwb = list_next(&zilog->zl_lwb_list, lwb);
1193 	mutex_exit(&zilog->zl_lock);
1194 
1195 	if (avl_numnodes(t) == 0)
1196 		return;
1197 
1198 	/*
1199 	 * If there was an IO error, we're not going to call zio_flush()
1200 	 * on these vdevs, so we simply empty the tree and free the
1201 	 * nodes. We avoid calling zio_flush() since there isn't any
1202 	 * good reason for doing so, after the lwb block failed to be
1203 	 * written out.
1204 	 */
1205 	if (zio->io_error != 0) {
1206 		while ((zv = avl_destroy_nodes(t, &cookie)) != NULL)
1207 			kmem_free(zv, sizeof (*zv));
1208 		return;
1209 	}
1210 
1211 	/*
1212 	 * If this lwb does not have any threads waiting for it to
1213 	 * complete, we want to defer issuing the DKIOCFLUSHWRITECACHE
1214 	 * command to the vdevs written to by "this" lwb, and instead
1215 	 * rely on the "next" lwb to handle the DKIOCFLUSHWRITECACHE
1216 	 * command for those vdevs. Thus, we merge the vdev tree of
1217 	 * "this" lwb with the vdev tree of the "next" lwb in the list,
1218 	 * and assume the "next" lwb will handle flushing the vdevs (or
1219 	 * deferring the flush(s) again).
1220 	 *
1221 	 * This is a useful performance optimization, especially for
1222 	 * workloads with lots of async write activity and few sync
1223 	 * write and/or fsync activity, as it has the potential to
1224 	 * coalesce multiple flush commands to a vdev into one.
1225 	 */
1226 	if (list_head(&lwb->lwb_waiters) == NULL && nlwb != NULL) {
1227 		zil_lwb_flush_defer(lwb, nlwb);
1228 		ASSERT(avl_is_empty(&lwb->lwb_vdev_tree));
1229 		return;
1230 	}
1231 
1232 	while ((zv = avl_destroy_nodes(t, &cookie)) != NULL) {
1233 		vdev_t *vd = vdev_lookup_top(spa, zv->zv_vdev);
1234 		if (vd != NULL)
1235 			zio_flush(lwb->lwb_root_zio, vd);
1236 		kmem_free(zv, sizeof (*zv));
1237 	}
1238 }
1239 
1240 static void
zil_lwb_set_zio_dependency(zilog_t * zilog,lwb_t * lwb)1241 zil_lwb_set_zio_dependency(zilog_t *zilog, lwb_t *lwb)
1242 {
1243 	lwb_t *last_lwb_opened = zilog->zl_last_lwb_opened;
1244 
1245 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
1246 	ASSERT(MUTEX_HELD(&zilog->zl_lock));
1247 
1248 	/*
1249 	 * The zilog's "zl_last_lwb_opened" field is used to build the
1250 	 * lwb/zio dependency chain, which is used to preserve the
1251 	 * ordering of lwb completions that is required by the semantics
1252 	 * of the ZIL. Each new lwb zio becomes a parent of the
1253 	 * "previous" lwb zio, such that the new lwb's zio cannot
1254 	 * complete until the "previous" lwb's zio completes.
1255 	 *
1256 	 * This is required by the semantics of zil_commit(); the commit
1257 	 * waiters attached to the lwbs will be woken in the lwb zio's
1258 	 * completion callback, so this zio dependency graph ensures the
1259 	 * waiters are woken in the correct order (the same order the
1260 	 * lwbs were created).
1261 	 */
1262 	if (last_lwb_opened != NULL &&
1263 	    last_lwb_opened->lwb_state != LWB_STATE_FLUSH_DONE) {
1264 		ASSERT(last_lwb_opened->lwb_state == LWB_STATE_OPENED ||
1265 		    last_lwb_opened->lwb_state == LWB_STATE_ISSUED ||
1266 		    last_lwb_opened->lwb_state == LWB_STATE_WRITE_DONE);
1267 
1268 		ASSERT3P(last_lwb_opened->lwb_root_zio, !=, NULL);
1269 		zio_add_child(lwb->lwb_root_zio,
1270 		    last_lwb_opened->lwb_root_zio);
1271 
1272 		/*
1273 		 * If the previous lwb's write hasn't already completed,
1274 		 * we also want to order the completion of the lwb write
1275 		 * zios (above, we only order the completion of the lwb
1276 		 * root zios). This is required because of how we can
1277 		 * defer the DKIOCFLUSHWRITECACHE commands for each lwb.
1278 		 *
1279 		 * When the DKIOCFLUSHWRITECACHE commands are deferred,
1280 		 * the previous lwb will rely on this lwb to flush the
1281 		 * vdevs written to by that previous lwb. Thus, we need
1282 		 * to ensure this lwb doesn't issue the flush until
1283 		 * after the previous lwb's write completes. We ensure
1284 		 * this ordering by setting the zio parent/child
1285 		 * relationship here.
1286 		 *
1287 		 * Without this relationship on the lwb's write zio,
1288 		 * it's possible for this lwb's write to complete prior
1289 		 * to the previous lwb's write completing; and thus, the
1290 		 * vdevs for the previous lwb would be flushed prior to
1291 		 * that lwb's data being written to those vdevs (the
1292 		 * vdevs are flushed in the lwb write zio's completion
1293 		 * handler, zil_lwb_write_done()).
1294 		 */
1295 		if (last_lwb_opened->lwb_state != LWB_STATE_WRITE_DONE) {
1296 			ASSERT(last_lwb_opened->lwb_state == LWB_STATE_OPENED ||
1297 			    last_lwb_opened->lwb_state == LWB_STATE_ISSUED);
1298 
1299 			ASSERT3P(last_lwb_opened->lwb_write_zio, !=, NULL);
1300 			zio_add_child(lwb->lwb_write_zio,
1301 			    last_lwb_opened->lwb_write_zio);
1302 		}
1303 	}
1304 }
1305 
1306 
1307 /*
1308  * This function's purpose is to "open" an lwb such that it is ready to
1309  * accept new itxs being committed to it. To do this, the lwb's zio
1310  * structures are created, and linked to the lwb. This function is
1311  * idempotent; if the passed in lwb has already been opened, this
1312  * function is essentially a no-op.
1313  */
1314 static void
zil_lwb_write_open(zilog_t * zilog,lwb_t * lwb)1315 zil_lwb_write_open(zilog_t *zilog, lwb_t *lwb)
1316 {
1317 	zbookmark_phys_t zb;
1318 	zio_priority_t prio;
1319 
1320 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
1321 	ASSERT3P(lwb, !=, NULL);
1322 	EQUIV(lwb->lwb_root_zio == NULL, lwb->lwb_state == LWB_STATE_CLOSED);
1323 	EQUIV(lwb->lwb_root_zio != NULL, lwb->lwb_state == LWB_STATE_OPENED);
1324 
1325 	SET_BOOKMARK(&zb, lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_OBJSET],
1326 	    ZB_ZIL_OBJECT, ZB_ZIL_LEVEL,
1327 	    lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_SEQ]);
1328 
1329 	if (lwb->lwb_root_zio == NULL) {
1330 		abd_t *lwb_abd = abd_get_from_buf(lwb->lwb_buf,
1331 		    BP_GET_LSIZE(&lwb->lwb_blk));
1332 
1333 		if (!lwb->lwb_slog || zilog->zl_cur_used <= zil_slog_bulk)
1334 			prio = ZIO_PRIORITY_SYNC_WRITE;
1335 		else
1336 			prio = ZIO_PRIORITY_ASYNC_WRITE;
1337 
1338 		lwb->lwb_root_zio = zio_root(zilog->zl_spa,
1339 		    zil_lwb_flush_vdevs_done, lwb, ZIO_FLAG_CANFAIL);
1340 		ASSERT3P(lwb->lwb_root_zio, !=, NULL);
1341 
1342 		lwb->lwb_write_zio = zio_rewrite(lwb->lwb_root_zio,
1343 		    zilog->zl_spa, 0, &lwb->lwb_blk, lwb_abd,
1344 		    BP_GET_LSIZE(&lwb->lwb_blk), zil_lwb_write_done, lwb,
1345 		    prio, ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE, &zb);
1346 		ASSERT3P(lwb->lwb_write_zio, !=, NULL);
1347 
1348 		lwb->lwb_state = LWB_STATE_OPENED;
1349 
1350 		mutex_enter(&zilog->zl_lock);
1351 		zil_lwb_set_zio_dependency(zilog, lwb);
1352 		zilog->zl_last_lwb_opened = lwb;
1353 		mutex_exit(&zilog->zl_lock);
1354 	}
1355 
1356 	ASSERT3P(lwb->lwb_root_zio, !=, NULL);
1357 	ASSERT3P(lwb->lwb_write_zio, !=, NULL);
1358 	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED);
1359 }
1360 
1361 /*
1362  * Define a limited set of intent log block sizes.
1363  *
1364  * These must be a multiple of 4KB. Note only the amount used (again
1365  * aligned to 4KB) actually gets written. However, we can't always just
1366  * allocate SPA_OLD_MAXBLOCKSIZE as the slog space could be exhausted.
1367  */
1368 uint64_t zil_block_buckets[] = {
1369     4096,		/* non TX_WRITE */
1370     8192+4096,		/* data base */
1371     32*1024 + 4096,	/* NFS writes */
1372     UINT64_MAX
1373 };
1374 
1375 /*
1376  * Start a log block write and advance to the next log block.
1377  * Calls are serialized.
1378  */
1379 static lwb_t *
zil_lwb_write_issue(zilog_t * zilog,lwb_t * lwb)1380 zil_lwb_write_issue(zilog_t *zilog, lwb_t *lwb)
1381 {
1382 	lwb_t *nlwb = NULL;
1383 	zil_chain_t *zilc;
1384 	spa_t *spa = zilog->zl_spa;
1385 	blkptr_t *bp;
1386 	dmu_tx_t *tx;
1387 	uint64_t txg;
1388 	uint64_t zil_blksz, wsz;
1389 	int i, error;
1390 	boolean_t slog;
1391 
1392 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
1393 	ASSERT3P(lwb->lwb_root_zio, !=, NULL);
1394 	ASSERT3P(lwb->lwb_write_zio, !=, NULL);
1395 	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED);
1396 
1397 	if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) {
1398 		zilc = (zil_chain_t *)lwb->lwb_buf;
1399 		bp = &zilc->zc_next_blk;
1400 	} else {
1401 		zilc = (zil_chain_t *)(lwb->lwb_buf + lwb->lwb_sz);
1402 		bp = &zilc->zc_next_blk;
1403 	}
1404 
1405 	ASSERT(lwb->lwb_nused <= lwb->lwb_sz);
1406 
1407 	/*
1408 	 * Allocate the next block and save its address in this block
1409 	 * before writing it in order to establish the log chain.
1410 	 * Note that if the allocation of nlwb synced before we wrote
1411 	 * the block that points at it (lwb), we'd leak it if we crashed.
1412 	 * Therefore, we don't do dmu_tx_commit() until zil_lwb_write_done().
1413 	 * We dirty the dataset to ensure that zil_sync() will be called
1414 	 * to clean up in the event of allocation failure or I/O failure.
1415 	 */
1416 
1417 	tx = dmu_tx_create(zilog->zl_os);
1418 
1419 	/*
1420 	 * Since we are not going to create any new dirty data, and we
1421 	 * can even help with clearing the existing dirty data, we
1422 	 * should not be subject to the dirty data based delays. We
1423 	 * use TXG_NOTHROTTLE to bypass the delay mechanism.
1424 	 */
1425 	VERIFY0(dmu_tx_assign(tx, TXG_WAIT | TXG_NOTHROTTLE));
1426 
1427 	dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
1428 	txg = dmu_tx_get_txg(tx);
1429 
1430 	lwb->lwb_tx = tx;
1431 
1432 	/*
1433 	 * Log blocks are pre-allocated. Here we select the size of the next
1434 	 * block, based on size used in the last block.
1435 	 * - first find the smallest bucket that will fit the block from a
1436 	 *   limited set of block sizes. This is because it's faster to write
1437 	 *   blocks allocated from the same metaslab as they are adjacent or
1438 	 *   close.
1439 	 * - next find the maximum from the new suggested size and an array of
1440 	 *   previous sizes. This lessens a picket fence effect of wrongly
1441 	 *   guesssing the size if we have a stream of say 2k, 64k, 2k, 64k
1442 	 *   requests.
1443 	 *
1444 	 * Note we only write what is used, but we can't just allocate
1445 	 * the maximum block size because we can exhaust the available
1446 	 * pool log space.
1447 	 */
1448 	zil_blksz = zilog->zl_cur_used + sizeof (zil_chain_t);
1449 	for (i = 0; zil_blksz > zil_block_buckets[i]; i++)
1450 		continue;
1451 	zil_blksz = zil_block_buckets[i];
1452 	if (zil_blksz == UINT64_MAX)
1453 		zil_blksz = SPA_OLD_MAXBLOCKSIZE;
1454 	zilog->zl_prev_blks[zilog->zl_prev_rotor] = zil_blksz;
1455 	for (i = 0; i < ZIL_PREV_BLKS; i++)
1456 		zil_blksz = MAX(zil_blksz, zilog->zl_prev_blks[i]);
1457 	zilog->zl_prev_rotor = (zilog->zl_prev_rotor + 1) & (ZIL_PREV_BLKS - 1);
1458 
1459 	BP_ZERO(bp);
1460 
1461 	/* pass the old blkptr in order to spread log blocks across devs */
1462 	error = zio_alloc_zil(spa, zilog->zl_os, txg, bp, &lwb->lwb_blk,
1463 	    zil_blksz, &slog);
1464 
1465 	if (error == 0) {
1466 		ASSERT3U(bp->blk_birth, ==, txg);
1467 		bp->blk_cksum = lwb->lwb_blk.blk_cksum;
1468 		bp->blk_cksum.zc_word[ZIL_ZC_SEQ]++;
1469 
1470 		/*
1471 		 * Allocate a new log write block (lwb).
1472 		 */
1473 		nlwb = zil_alloc_lwb(zilog, bp, slog, txg);
1474 	}
1475 
1476 	if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) {
1477 		/* For Slim ZIL only write what is used. */
1478 		wsz = P2ROUNDUP_TYPED(lwb->lwb_nused, ZIL_MIN_BLKSZ, uint64_t);
1479 		ASSERT3U(wsz, <=, lwb->lwb_sz);
1480 		zio_shrink(lwb->lwb_write_zio, wsz);
1481 
1482 	} else {
1483 		wsz = lwb->lwb_sz;
1484 	}
1485 
1486 	zilc->zc_pad = 0;
1487 	zilc->zc_nused = lwb->lwb_nused;
1488 	zilc->zc_eck.zec_cksum = lwb->lwb_blk.blk_cksum;
1489 
1490 	/*
1491 	 * clear unused data for security
1492 	 */
1493 	bzero(lwb->lwb_buf + lwb->lwb_nused, wsz - lwb->lwb_nused);
1494 
1495 	spa_config_enter(zilog->zl_spa, SCL_STATE, lwb, RW_READER);
1496 
1497 	zil_lwb_add_block(lwb, &lwb->lwb_blk);
1498 	lwb->lwb_issued_timestamp = gethrtime();
1499 	lwb->lwb_state = LWB_STATE_ISSUED;
1500 
1501 	zio_nowait(lwb->lwb_root_zio);
1502 	zio_nowait(lwb->lwb_write_zio);
1503 
1504 	/*
1505 	 * If there was an allocation failure then nlwb will be null which
1506 	 * forces a txg_wait_synced().
1507 	 */
1508 	return (nlwb);
1509 }
1510 
1511 static lwb_t *
zil_lwb_commit(zilog_t * zilog,itx_t * itx,lwb_t * lwb)1512 zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
1513 {
1514 	lr_t *lrcb, *lrc;
1515 	lr_write_t *lrwb, *lrw;
1516 	char *lr_buf;
1517 	uint64_t dlen, dnow, lwb_sp, reclen, txg;
1518 
1519 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
1520 	ASSERT3P(lwb, !=, NULL);
1521 	ASSERT3P(lwb->lwb_buf, !=, NULL);
1522 
1523 	zil_lwb_write_open(zilog, lwb);
1524 
1525 	lrc = &itx->itx_lr;
1526 	lrw = (lr_write_t *)lrc;
1527 
1528 	/*
1529 	 * A commit itx doesn't represent any on-disk state; instead
1530 	 * it's simply used as a place holder on the commit list, and
1531 	 * provides a mechanism for attaching a "commit waiter" onto the
1532 	 * correct lwb (such that the waiter can be signalled upon
1533 	 * completion of that lwb). Thus, we don't process this itx's
1534 	 * log record if it's a commit itx (these itx's don't have log
1535 	 * records), and instead link the itx's waiter onto the lwb's
1536 	 * list of waiters.
1537 	 *
1538 	 * For more details, see the comment above zil_commit().
1539 	 */
1540 	if (lrc->lrc_txtype == TX_COMMIT) {
1541 		mutex_enter(&zilog->zl_lock);
1542 		zil_commit_waiter_link_lwb(itx->itx_private, lwb);
1543 		itx->itx_private = NULL;
1544 		mutex_exit(&zilog->zl_lock);
1545 		return (lwb);
1546 	}
1547 
1548 	if (lrc->lrc_txtype == TX_WRITE && itx->itx_wr_state == WR_NEED_COPY) {
1549 		dlen = P2ROUNDUP_TYPED(
1550 		    lrw->lr_length, sizeof (uint64_t), uint64_t);
1551 	} else {
1552 		dlen = 0;
1553 	}
1554 	reclen = lrc->lrc_reclen;
1555 	zilog->zl_cur_used += (reclen + dlen);
1556 	txg = lrc->lrc_txg;
1557 
1558 	ASSERT3U(zilog->zl_cur_used, <, UINT64_MAX - (reclen + dlen));
1559 
1560 cont:
1561 	/*
1562 	 * If this record won't fit in the current log block, start a new one.
1563 	 * For WR_NEED_COPY optimize layout for minimal number of chunks.
1564 	 */
1565 	lwb_sp = lwb->lwb_sz - lwb->lwb_nused;
1566 	if (reclen > lwb_sp || (reclen + dlen > lwb_sp &&
1567 	    lwb_sp < ZIL_MAX_WASTE_SPACE && (dlen % ZIL_MAX_LOG_DATA == 0 ||
1568 	    lwb_sp < reclen + dlen % ZIL_MAX_LOG_DATA))) {
1569 		lwb = zil_lwb_write_issue(zilog, lwb);
1570 		if (lwb == NULL)
1571 			return (NULL);
1572 		zil_lwb_write_open(zilog, lwb);
1573 		ASSERT(LWB_EMPTY(lwb));
1574 		lwb_sp = lwb->lwb_sz - lwb->lwb_nused;
1575 		ASSERT3U(reclen + MIN(dlen, sizeof (uint64_t)), <=, lwb_sp);
1576 	}
1577 
1578 	dnow = MIN(dlen, lwb_sp - reclen);
1579 	lr_buf = lwb->lwb_buf + lwb->lwb_nused;
1580 	bcopy(lrc, lr_buf, reclen);
1581 	lrcb = (lr_t *)lr_buf;		/* Like lrc, but inside lwb. */
1582 	lrwb = (lr_write_t *)lrcb;	/* Like lrw, but inside lwb. */
1583 
1584 	/*
1585 	 * If it's a write, fetch the data or get its blkptr as appropriate.
1586 	 */
1587 	if (lrc->lrc_txtype == TX_WRITE) {
1588 		if (txg > spa_freeze_txg(zilog->zl_spa))
1589 			txg_wait_synced(zilog->zl_dmu_pool, txg);
1590 		if (itx->itx_wr_state != WR_COPIED) {
1591 			char *dbuf;
1592 			int error;
1593 
1594 			if (itx->itx_wr_state == WR_NEED_COPY) {
1595 				dbuf = lr_buf + reclen;
1596 				lrcb->lrc_reclen += dnow;
1597 				if (lrwb->lr_length > dnow)
1598 					lrwb->lr_length = dnow;
1599 				lrw->lr_offset += dnow;
1600 				lrw->lr_length -= dnow;
1601 			} else {
1602 				ASSERT(itx->itx_wr_state == WR_INDIRECT);
1603 				dbuf = NULL;
1604 			}
1605 
1606 			/*
1607 			 * We pass in the "lwb_write_zio" rather than
1608 			 * "lwb_root_zio" so that the "lwb_write_zio"
1609 			 * becomes the parent of any zio's created by
1610 			 * the "zl_get_data" callback. The vdevs are
1611 			 * flushed after the "lwb_write_zio" completes,
1612 			 * so we want to make sure that completion
1613 			 * callback waits for these additional zio's,
1614 			 * such that the vdevs used by those zio's will
1615 			 * be included in the lwb's vdev tree, and those
1616 			 * vdevs will be properly flushed. If we passed
1617 			 * in "lwb_root_zio" here, then these additional
1618 			 * vdevs may not be flushed; e.g. if these zio's
1619 			 * completed after "lwb_write_zio" completed.
1620 			 */
1621 			error = zilog->zl_get_data(itx->itx_private,
1622 			    lrwb, dbuf, lwb, lwb->lwb_write_zio);
1623 
1624 			if (error == EIO) {
1625 				txg_wait_synced(zilog->zl_dmu_pool, txg);
1626 				return (lwb);
1627 			}
1628 			if (error != 0) {
1629 				ASSERT(error == ENOENT || error == EEXIST ||
1630 				    error == EALREADY);
1631 				return (lwb);
1632 			}
1633 		}
1634 	}
1635 
1636 	/*
1637 	 * We're actually making an entry, so update lrc_seq to be the
1638 	 * log record sequence number.  Note that this is generally not
1639 	 * equal to the itx sequence number because not all transactions
1640 	 * are synchronous, and sometimes spa_sync() gets there first.
1641 	 */
1642 	lrcb->lrc_seq = ++zilog->zl_lr_seq;
1643 	lwb->lwb_nused += reclen + dnow;
1644 
1645 	zil_lwb_add_txg(lwb, txg);
1646 
1647 	ASSERT3U(lwb->lwb_nused, <=, lwb->lwb_sz);
1648 	ASSERT0(P2PHASE(lwb->lwb_nused, sizeof (uint64_t)));
1649 
1650 	dlen -= dnow;
1651 	if (dlen > 0) {
1652 		zilog->zl_cur_used += reclen;
1653 		goto cont;
1654 	}
1655 
1656 	return (lwb);
1657 }
1658 
1659 itx_t *
zil_itx_create(uint64_t txtype,size_t lrsize)1660 zil_itx_create(uint64_t txtype, size_t lrsize)
1661 {
1662 	itx_t *itx;
1663 
1664 	lrsize = P2ROUNDUP_TYPED(lrsize, sizeof (uint64_t), size_t);
1665 
1666 	itx = kmem_alloc(offsetof(itx_t, itx_lr) + lrsize, KM_SLEEP);
1667 	itx->itx_lr.lrc_txtype = txtype;
1668 	itx->itx_lr.lrc_reclen = lrsize;
1669 	itx->itx_lr.lrc_seq = 0;	/* defensive */
1670 	itx->itx_sync = B_TRUE;		/* default is synchronous */
1671 
1672 	return (itx);
1673 }
1674 
1675 void
zil_itx_destroy(itx_t * itx)1676 zil_itx_destroy(itx_t *itx)
1677 {
1678 	kmem_free(itx, offsetof(itx_t, itx_lr) + itx->itx_lr.lrc_reclen);
1679 }
1680 
1681 /*
1682  * Free up the sync and async itxs. The itxs_t has already been detached
1683  * so no locks are needed.
1684  */
1685 static void
zil_itxg_clean(itxs_t * itxs)1686 zil_itxg_clean(itxs_t *itxs)
1687 {
1688 	itx_t *itx;
1689 	list_t *list;
1690 	avl_tree_t *t;
1691 	void *cookie;
1692 	itx_async_node_t *ian;
1693 
1694 	list = &itxs->i_sync_list;
1695 	while ((itx = list_head(list)) != NULL) {
1696 		/*
1697 		 * In the general case, commit itxs will not be found
1698 		 * here, as they'll be committed to an lwb via
1699 		 * zil_lwb_commit(), and free'd in that function. Having
1700 		 * said that, it is still possible for commit itxs to be
1701 		 * found here, due to the following race:
1702 		 *
1703 		 *	- a thread calls zil_commit() which assigns the
1704 		 *	  commit itx to a per-txg i_sync_list
1705 		 *	- zil_itxg_clean() is called (e.g. via spa_sync())
1706 		 *	  while the waiter is still on the i_sync_list
1707 		 *
1708 		 * There's nothing to prevent syncing the txg while the
1709 		 * waiter is on the i_sync_list. This normally doesn't
1710 		 * happen because spa_sync() is slower than zil_commit(),
1711 		 * but if zil_commit() calls txg_wait_synced() (e.g.
1712 		 * because zil_create() or zil_commit_writer_stall() is
1713 		 * called) we will hit this case.
1714 		 */
1715 		if (itx->itx_lr.lrc_txtype == TX_COMMIT)
1716 			zil_commit_waiter_skip(itx->itx_private);
1717 
1718 		list_remove(list, itx);
1719 		zil_itx_destroy(itx);
1720 	}
1721 
1722 	cookie = NULL;
1723 	t = &itxs->i_async_tree;
1724 	while ((ian = avl_destroy_nodes(t, &cookie)) != NULL) {
1725 		list = &ian->ia_list;
1726 		while ((itx = list_head(list)) != NULL) {
1727 			list_remove(list, itx);
1728 			/* commit itxs should never be on the async lists. */
1729 			ASSERT3U(itx->itx_lr.lrc_txtype, !=, TX_COMMIT);
1730 			zil_itx_destroy(itx);
1731 		}
1732 		list_destroy(list);
1733 		kmem_free(ian, sizeof (itx_async_node_t));
1734 	}
1735 	avl_destroy(t);
1736 
1737 	kmem_free(itxs, sizeof (itxs_t));
1738 }
1739 
1740 static int
zil_aitx_compare(const void * x1,const void * x2)1741 zil_aitx_compare(const void *x1, const void *x2)
1742 {
1743 	const uint64_t o1 = ((itx_async_node_t *)x1)->ia_foid;
1744 	const uint64_t o2 = ((itx_async_node_t *)x2)->ia_foid;
1745 
1746 	return (TREE_CMP(o1, o2));
1747 }
1748 
1749 /*
1750  * Remove all async itx with the given oid.
1751  */
1752 void
zil_remove_async(zilog_t * zilog,uint64_t oid)1753 zil_remove_async(zilog_t *zilog, uint64_t oid)
1754 {
1755 	uint64_t otxg, txg;
1756 	itx_async_node_t *ian;
1757 	avl_tree_t *t;
1758 	avl_index_t where;
1759 	list_t clean_list;
1760 	itx_t *itx;
1761 
1762 	ASSERT(oid != 0);
1763 	list_create(&clean_list, sizeof (itx_t), offsetof(itx_t, itx_node));
1764 
1765 	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */
1766 		otxg = ZILTEST_TXG;
1767 	else
1768 		otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
1769 
1770 	for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
1771 		itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
1772 
1773 		mutex_enter(&itxg->itxg_lock);
1774 		if (itxg->itxg_txg != txg) {
1775 			mutex_exit(&itxg->itxg_lock);
1776 			continue;
1777 		}
1778 
1779 		/*
1780 		 * Locate the object node and append its list.
1781 		 */
1782 		t = &itxg->itxg_itxs->i_async_tree;
1783 		ian = avl_find(t, &oid, &where);
1784 		if (ian != NULL)
1785 			list_move_tail(&clean_list, &ian->ia_list);
1786 		mutex_exit(&itxg->itxg_lock);
1787 	}
1788 	while ((itx = list_head(&clean_list)) != NULL) {
1789 		list_remove(&clean_list, itx);
1790 		/* commit itxs should never be on the async lists. */
1791 		ASSERT3U(itx->itx_lr.lrc_txtype, !=, TX_COMMIT);
1792 		zil_itx_destroy(itx);
1793 	}
1794 	list_destroy(&clean_list);
1795 }
1796 
1797 void
zil_itx_assign(zilog_t * zilog,itx_t * itx,dmu_tx_t * tx)1798 zil_itx_assign(zilog_t *zilog, itx_t *itx, dmu_tx_t *tx)
1799 {
1800 	uint64_t txg;
1801 	itxg_t *itxg;
1802 	itxs_t *itxs, *clean = NULL;
1803 
1804 	/*
1805 	 * Ensure the data of a renamed file is committed before the rename.
1806 	 */
1807 	if ((itx->itx_lr.lrc_txtype & ~TX_CI) == TX_RENAME)
1808 		zil_async_to_sync(zilog, itx->itx_oid);
1809 
1810 	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX)
1811 		txg = ZILTEST_TXG;
1812 	else
1813 		txg = dmu_tx_get_txg(tx);
1814 
1815 	itxg = &zilog->zl_itxg[txg & TXG_MASK];
1816 	mutex_enter(&itxg->itxg_lock);
1817 	itxs = itxg->itxg_itxs;
1818 	if (itxg->itxg_txg != txg) {
1819 		if (itxs != NULL) {
1820 			/*
1821 			 * The zil_clean callback hasn't got around to cleaning
1822 			 * this itxg. Save the itxs for release below.
1823 			 * This should be rare.
1824 			 */
1825 			zfs_dbgmsg("zil_itx_assign: missed itx cleanup for "
1826 			    "txg %llu", itxg->itxg_txg);
1827 			clean = itxg->itxg_itxs;
1828 		}
1829 		itxg->itxg_txg = txg;
1830 		itxs = itxg->itxg_itxs = kmem_zalloc(sizeof (itxs_t), KM_SLEEP);
1831 
1832 		list_create(&itxs->i_sync_list, sizeof (itx_t),
1833 		    offsetof(itx_t, itx_node));
1834 		avl_create(&itxs->i_async_tree, zil_aitx_compare,
1835 		    sizeof (itx_async_node_t),
1836 		    offsetof(itx_async_node_t, ia_node));
1837 	}
1838 	if (itx->itx_sync) {
1839 		list_insert_tail(&itxs->i_sync_list, itx);
1840 	} else {
1841 		avl_tree_t *t = &itxs->i_async_tree;
1842 		uint64_t foid =
1843 		    LR_FOID_GET_OBJ(((lr_ooo_t *)&itx->itx_lr)->lr_foid);
1844 		itx_async_node_t *ian;
1845 		avl_index_t where;
1846 
1847 		ian = avl_find(t, &foid, &where);
1848 		if (ian == NULL) {
1849 			ian = kmem_alloc(sizeof (itx_async_node_t), KM_SLEEP);
1850 			list_create(&ian->ia_list, sizeof (itx_t),
1851 			    offsetof(itx_t, itx_node));
1852 			ian->ia_foid = foid;
1853 			avl_insert(t, ian, where);
1854 		}
1855 		list_insert_tail(&ian->ia_list, itx);
1856 	}
1857 
1858 	itx->itx_lr.lrc_txg = dmu_tx_get_txg(tx);
1859 
1860 	/*
1861 	 * We don't want to dirty the ZIL using ZILTEST_TXG, because
1862 	 * zil_clean() will never be called using ZILTEST_TXG. Thus, we
1863 	 * need to be careful to always dirty the ZIL using the "real"
1864 	 * TXG (not itxg_txg) even when the SPA is frozen.
1865 	 */
1866 	zilog_dirty(zilog, dmu_tx_get_txg(tx));
1867 	mutex_exit(&itxg->itxg_lock);
1868 
1869 	/* Release the old itxs now we've dropped the lock */
1870 	if (clean != NULL)
1871 		zil_itxg_clean(clean);
1872 }
1873 
1874 /*
1875  * If there are any in-memory intent log transactions which have now been
1876  * synced then start up a taskq to free them. We should only do this after we
1877  * have written out the uberblocks (i.e. txg has been comitted) so that
1878  * don't inadvertently clean out in-memory log records that would be required
1879  * by zil_commit().
1880  */
1881 void
zil_clean(zilog_t * zilog,uint64_t synced_txg)1882 zil_clean(zilog_t *zilog, uint64_t synced_txg)
1883 {
1884 	itxg_t *itxg = &zilog->zl_itxg[synced_txg & TXG_MASK];
1885 	itxs_t *clean_me;
1886 
1887 	ASSERT3U(synced_txg, <, ZILTEST_TXG);
1888 
1889 	mutex_enter(&itxg->itxg_lock);
1890 	if (itxg->itxg_itxs == NULL || itxg->itxg_txg == ZILTEST_TXG) {
1891 		mutex_exit(&itxg->itxg_lock);
1892 		return;
1893 	}
1894 	ASSERT3U(itxg->itxg_txg, <=, synced_txg);
1895 	ASSERT3U(itxg->itxg_txg, !=, 0);
1896 	clean_me = itxg->itxg_itxs;
1897 	itxg->itxg_itxs = NULL;
1898 	itxg->itxg_txg = 0;
1899 	mutex_exit(&itxg->itxg_lock);
1900 	/*
1901 	 * Preferably start a task queue to free up the old itxs but
1902 	 * if taskq_dispatch can't allocate resources to do that then
1903 	 * free it in-line. This should be rare. Note, using TQ_SLEEP
1904 	 * created a bad performance problem.
1905 	 */
1906 	ASSERT3P(zilog->zl_dmu_pool, !=, NULL);
1907 	ASSERT3P(zilog->zl_dmu_pool->dp_zil_clean_taskq, !=, NULL);
1908 	if (taskq_dispatch(zilog->zl_dmu_pool->dp_zil_clean_taskq,
1909 	    (void (*)(void *))zil_itxg_clean, clean_me, TQ_NOSLEEP) ==
1910 	    TASKQID_INVALID)
1911 		zil_itxg_clean(clean_me);
1912 }
1913 
1914 /*
1915  * This function will traverse the queue of itxs that need to be
1916  * committed, and move them onto the ZIL's zl_itx_commit_list.
1917  */
1918 static void
zil_get_commit_list(zilog_t * zilog)1919 zil_get_commit_list(zilog_t *zilog)
1920 {
1921 	uint64_t otxg, txg;
1922 	list_t *commit_list = &zilog->zl_itx_commit_list;
1923 
1924 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
1925 
1926 	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */
1927 		otxg = ZILTEST_TXG;
1928 	else
1929 		otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
1930 
1931 	/*
1932 	 * This is inherently racy, since there is nothing to prevent
1933 	 * the last synced txg from changing. That's okay since we'll
1934 	 * only commit things in the future.
1935 	 */
1936 	for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
1937 		itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
1938 
1939 		mutex_enter(&itxg->itxg_lock);
1940 		if (itxg->itxg_txg != txg) {
1941 			mutex_exit(&itxg->itxg_lock);
1942 			continue;
1943 		}
1944 
1945 		/*
1946 		 * If we're adding itx records to the zl_itx_commit_list,
1947 		 * then the zil better be dirty in this "txg". We can assert
1948 		 * that here since we're holding the itxg_lock which will
1949 		 * prevent spa_sync from cleaning it. Once we add the itxs
1950 		 * to the zl_itx_commit_list we must commit it to disk even
1951 		 * if it's unnecessary (i.e. the txg was synced).
1952 		 */
1953 		ASSERT(zilog_is_dirty_in_txg(zilog, txg) ||
1954 		    spa_freeze_txg(zilog->zl_spa) != UINT64_MAX);
1955 		list_move_tail(commit_list, &itxg->itxg_itxs->i_sync_list);
1956 
1957 		mutex_exit(&itxg->itxg_lock);
1958 	}
1959 }
1960 
1961 /*
1962  * Move the async itxs for a specified object to commit into sync lists.
1963  */
1964 static void
zil_async_to_sync(zilog_t * zilog,uint64_t foid)1965 zil_async_to_sync(zilog_t *zilog, uint64_t foid)
1966 {
1967 	uint64_t otxg, txg;
1968 	itx_async_node_t *ian;
1969 	avl_tree_t *t;
1970 	avl_index_t where;
1971 
1972 	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */
1973 		otxg = ZILTEST_TXG;
1974 	else
1975 		otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
1976 
1977 	/*
1978 	 * This is inherently racy, since there is nothing to prevent
1979 	 * the last synced txg from changing.
1980 	 */
1981 	for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
1982 		itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
1983 
1984 		mutex_enter(&itxg->itxg_lock);
1985 		if (itxg->itxg_txg != txg) {
1986 			mutex_exit(&itxg->itxg_lock);
1987 			continue;
1988 		}
1989 
1990 		/*
1991 		 * If a foid is specified then find that node and append its
1992 		 * list. Otherwise walk the tree appending all the lists
1993 		 * to the sync list. We add to the end rather than the
1994 		 * beginning to ensure the create has happened.
1995 		 */
1996 		t = &itxg->itxg_itxs->i_async_tree;
1997 		if (foid != 0) {
1998 			ian = avl_find(t, &foid, &where);
1999 			if (ian != NULL) {
2000 				list_move_tail(&itxg->itxg_itxs->i_sync_list,
2001 				    &ian->ia_list);
2002 			}
2003 		} else {
2004 			void *cookie = NULL;
2005 
2006 			while ((ian = avl_destroy_nodes(t, &cookie)) != NULL) {
2007 				list_move_tail(&itxg->itxg_itxs->i_sync_list,
2008 				    &ian->ia_list);
2009 				list_destroy(&ian->ia_list);
2010 				kmem_free(ian, sizeof (itx_async_node_t));
2011 			}
2012 		}
2013 		mutex_exit(&itxg->itxg_lock);
2014 	}
2015 }
2016 
2017 /*
2018  * This function will prune commit itxs that are at the head of the
2019  * commit list (it won't prune past the first non-commit itx), and
2020  * either: a) attach them to the last lwb that's still pending
2021  * completion, or b) skip them altogether.
2022  *
2023  * This is used as a performance optimization to prevent commit itxs
2024  * from generating new lwbs when it's unnecessary to do so.
2025  */
2026 static void
zil_prune_commit_list(zilog_t * zilog)2027 zil_prune_commit_list(zilog_t *zilog)
2028 {
2029 	itx_t *itx;
2030 
2031 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
2032 
2033 	while (itx = list_head(&zilog->zl_itx_commit_list)) {
2034 		lr_t *lrc = &itx->itx_lr;
2035 		if (lrc->lrc_txtype != TX_COMMIT)
2036 			break;
2037 
2038 		mutex_enter(&zilog->zl_lock);
2039 
2040 		lwb_t *last_lwb = zilog->zl_last_lwb_opened;
2041 		if (last_lwb == NULL ||
2042 		    last_lwb->lwb_state == LWB_STATE_FLUSH_DONE) {
2043 			/*
2044 			 * All of the itxs this waiter was waiting on
2045 			 * must have already completed (or there were
2046 			 * never any itx's for it to wait on), so it's
2047 			 * safe to skip this waiter and mark it done.
2048 			 */
2049 			zil_commit_waiter_skip(itx->itx_private);
2050 		} else {
2051 			zil_commit_waiter_link_lwb(itx->itx_private, last_lwb);
2052 			itx->itx_private = NULL;
2053 		}
2054 
2055 		mutex_exit(&zilog->zl_lock);
2056 
2057 		list_remove(&zilog->zl_itx_commit_list, itx);
2058 		zil_itx_destroy(itx);
2059 	}
2060 
2061 	IMPLY(itx != NULL, itx->itx_lr.lrc_txtype != TX_COMMIT);
2062 }
2063 
2064 static void
zil_commit_writer_stall(zilog_t * zilog)2065 zil_commit_writer_stall(zilog_t *zilog)
2066 {
2067 	/*
2068 	 * When zio_alloc_zil() fails to allocate the next lwb block on
2069 	 * disk, we must call txg_wait_synced() to ensure all of the
2070 	 * lwbs in the zilog's zl_lwb_list are synced and then freed (in
2071 	 * zil_sync()), such that any subsequent ZIL writer (i.e. a call
2072 	 * to zil_process_commit_list()) will have to call zil_create(),
2073 	 * and start a new ZIL chain.
2074 	 *
2075 	 * Since zil_alloc_zil() failed, the lwb that was previously
2076 	 * issued does not have a pointer to the "next" lwb on disk.
2077 	 * Thus, if another ZIL writer thread was to allocate the "next"
2078 	 * on-disk lwb, that block could be leaked in the event of a
2079 	 * crash (because the previous lwb on-disk would not point to
2080 	 * it).
2081 	 *
2082 	 * We must hold the zilog's zl_issuer_lock while we do this, to
2083 	 * ensure no new threads enter zil_process_commit_list() until
2084 	 * all lwb's in the zl_lwb_list have been synced and freed
2085 	 * (which is achieved via the txg_wait_synced() call).
2086 	 */
2087 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
2088 	txg_wait_synced(zilog->zl_dmu_pool, 0);
2089 	ASSERT3P(list_tail(&zilog->zl_lwb_list), ==, NULL);
2090 }
2091 
2092 /*
2093  * This function will traverse the commit list, creating new lwbs as
2094  * needed, and committing the itxs from the commit list to these newly
2095  * created lwbs. Additionally, as a new lwb is created, the previous
2096  * lwb will be issued to the zio layer to be written to disk.
2097  */
2098 static void
zil_process_commit_list(zilog_t * zilog)2099 zil_process_commit_list(zilog_t *zilog)
2100 {
2101 	spa_t *spa = zilog->zl_spa;
2102 	list_t nolwb_waiters;
2103 	lwb_t *lwb;
2104 	itx_t *itx;
2105 
2106 	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
2107 
2108 	/*
2109 	 * Return if there's nothing to commit before we dirty the fs by
2110 	 * calling zil_create().
2111 	 */
2112 	if (list_head(&zilog->zl_itx_commit_list) == NULL)
2113 		return;
2114 
2115 	list_create(&nolwb_waiters, sizeof (zil_commit_waiter_t),
2116 	    offsetof(zil_commit_waiter_t, zcw_node));
2117 
2118 	lwb = list_tail(&zilog->zl_lwb_list);
2119 	if (lwb == NULL) {
2120 		lwb = zil_create(zilog);
2121 	} else {
2122 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED);
2123 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_WRITE_DONE);
2124 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_FLUSH_DONE);
2125 	}
2126 
2127 	while (itx = list_head(&zilog->zl_itx_commit_list)) {
2128 		lr_t *lrc = &itx->itx_lr;
2129 		uint64_t txg = lrc->lrc_txg;
2130 
2131 		ASSERT3U(txg, !=, 0);
2132 
2133 		if (lrc->lrc_txtype == TX_COMMIT) {
2134 			DTRACE_PROBE2(zil__process__commit__itx,
2135 			    zilog_t *, zilog, itx_t *, itx);
2136 		} else {
2137 			DTRACE_PROBE2(zil__process__normal__itx,
2138 			    zilog_t *, zilog, itx_t *, itx);
2139 		}
2140 
2141 		boolean_t synced = txg <= spa_last_synced_txg(spa);
2142 		boolean_t frozen = txg > spa_freeze_txg(spa);
2143 
2144 		/*
2145 		 * If the txg of this itx has already been synced out, then
2146 		 * we don't need to commit this itx to an lwb. This is
2147 		 * because the data of this itx will have already been
2148 		 * written to the main pool. This is inherently racy, and
2149 		 * it's still ok to commit an itx whose txg has already
2150 		 * been synced; this will result in a write that's
2151 		 * unnecessary, but will do no harm.
2152 		 *
2153 		 * With that said, we always want to commit TX_COMMIT itxs
2154 		 * to an lwb, regardless of whether or not that itx's txg
2155 		 * has been synced out. We do this to ensure any OPENED lwb
2156 		 * will always have at least one zil_commit_waiter_t linked
2157 		 * to the lwb.
2158 		 *
2159 		 * As a counter-example, if we skipped TX_COMMIT itx's
2160 		 * whose txg had already been synced, the following
2161 		 * situation could occur if we happened to be racing with
2162 		 * spa_sync:
2163 		 *
2164 		 * 1. we commit a non-TX_COMMIT itx to an lwb, where the
2165 		 *    itx's txg is 10 and the last synced txg is 9.
2166 		 * 2. spa_sync finishes syncing out txg 10.
2167 		 * 3. we move to the next itx in the list, it's a TX_COMMIT
2168 		 *    whose txg is 10, so we skip it rather than committing
2169 		 *    it to the lwb used in (1).
2170 		 *
2171 		 * If the itx that is skipped in (3) is the last TX_COMMIT
2172 		 * itx in the commit list, than it's possible for the lwb
2173 		 * used in (1) to remain in the OPENED state indefinitely.
2174 		 *
2175 		 * To prevent the above scenario from occuring, ensuring
2176 		 * that once an lwb is OPENED it will transition to ISSUED
2177 		 * and eventually DONE, we always commit TX_COMMIT itx's to
2178 		 * an lwb here, even if that itx's txg has already been
2179 		 * synced.
2180 		 *
2181 		 * Finally, if the pool is frozen, we _always_ commit the
2182 		 * itx.  The point of freezing the pool is to prevent data
2183 		 * from being written to the main pool via spa_sync, and
2184 		 * instead rely solely on the ZIL to persistently store the
2185 		 * data; i.e.  when the pool is frozen, the last synced txg
2186 		 * value can't be trusted.
2187 		 */
2188 		if (frozen || !synced || lrc->lrc_txtype == TX_COMMIT) {
2189 			if (lwb != NULL) {
2190 				lwb = zil_lwb_commit(zilog, itx, lwb);
2191 			} else if (lrc->lrc_txtype == TX_COMMIT) {
2192 				ASSERT3P(lwb, ==, NULL);
2193 				zil_commit_waiter_link_nolwb(
2194 				    itx->itx_private, &nolwb_waiters);
2195 			}
2196 		}
2197 
2198 		list_remove(&zilog->zl_itx_commit_list, itx);
2199 		zil_itx_destroy(itx);
2200 	}
2201 
2202 	if (lwb == NULL) {
2203 		/*
2204 		 * This indicates zio_alloc_zil() failed to allocate the
2205 		 * "next" lwb on-disk. When this happens, we must stall
2206 		 * the ZIL write pipeline; see the comment within
2207 		 * zil_commit_writer_stall() for more details.
2208 		 */
2209 		zil_commit_writer_stall(zilog);
2210 
2211 		/*
2212 		 * Additionally, we have to signal and mark the "nolwb"
2213 		 * waiters as "done" here, since without an lwb, we
2214 		 * can't do this via zil_lwb_flush_vdevs_done() like
2215 		 * normal.
2216 		 */
2217 		zil_commit_waiter_t *zcw;
2218 		while (zcw = list_head(&nolwb_waiters)) {
2219 			zil_commit_waiter_skip(zcw);
2220 			list_remove(&nolwb_waiters, zcw);
2221 		}
2222 	} else {
2223 		ASSERT(list_is_empty(&nolwb_waiters));
2224 		ASSERT3P(lwb, !=, NULL);
2225 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED);
2226 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_WRITE_DONE);
2227 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_FLUSH_DONE);
2228 
2229 		/*
2230 		 * At this point, the ZIL block pointed at by the "lwb"
2231 		 * variable is in one of the following states: "closed"
2232 		 * or "open".
2233 		 *
2234 		 * If its "closed", then no itxs have been committed to
2235 		 * it, so there's no point in issuing its zio (i.e.
2236 		 * it's "empty").
2237 		 *
2238 		 * If its "open" state, then it contains one or more
2239 		 * itxs that eventually need to be committed to stable
2240 		 * storage. In this case we intentionally do not issue
2241 		 * the lwb's zio to disk yet, and instead rely on one of
2242 		 * the following two mechanisms for issuing the zio:
2243 		 *
2244 		 * 1. Ideally, there will be more ZIL activity occuring
2245 		 * on the system, such that this function will be
2246 		 * immediately called again (not necessarily by the same
2247 		 * thread) and this lwb's zio will be issued via
2248 		 * zil_lwb_commit(). This way, the lwb is guaranteed to
2249 		 * be "full" when it is issued to disk, and we'll make
2250 		 * use of the lwb's size the best we can.
2251 		 *
2252 		 * 2. If there isn't sufficient ZIL activity occuring on
2253 		 * the system, such that this lwb's zio isn't issued via
2254 		 * zil_lwb_commit(), zil_commit_waiter() will issue the
2255 		 * lwb's zio. If this occurs, the lwb is not guaranteed
2256 		 * to be "full" by the time its zio is issued, and means
2257 		 * the size of the lwb was "too large" given the amount
2258 		 * of ZIL activity occuring on the system at that time.
2259 		 *
2260 		 * We do this for a couple of reasons:
2261 		 *
2262 		 * 1. To try and reduce the number of IOPs needed to
2263 		 * write the same number of itxs. If an lwb has space
2264 		 * available in it's buffer for more itxs, and more itxs
2265 		 * will be committed relatively soon (relative to the
2266 		 * latency of performing a write), then it's beneficial
2267 		 * to wait for these "next" itxs. This way, more itxs
2268 		 * can be committed to stable storage with fewer writes.
2269 		 *
2270 		 * 2. To try and use the largest lwb block size that the
2271 		 * incoming rate of itxs can support. Again, this is to
2272 		 * try and pack as many itxs into as few lwbs as
2273 		 * possible, without significantly impacting the latency
2274 		 * of each individual itx.
2275 		 */
2276 	}
2277 }
2278 
2279 /*
2280  * This function is responsible for ensuring the passed in commit waiter
2281  * (and associated commit itx) is committed to an lwb. If the waiter is
2282  * not already committed to an lwb, all itxs in the zilog's queue of
2283  * itxs will be processed. The assumption is the passed in waiter's
2284  * commit itx will found in the queue just like the other non-commit
2285  * itxs, such that when the entire queue is processed, the waiter will
2286  * have been commited to an lwb.
2287  *
2288  * The lwb associated with the passed in waiter is not guaranteed to
2289  * have been issued by the time this function completes. If the lwb is
2290  * not issued, we rely on future calls to zil_commit_writer() to issue
2291  * the lwb, or the timeout mechanism found in zil_commit_waiter().
2292  */
2293 static void
zil_commit_writer(zilog_t * zilog,zil_commit_waiter_t * zcw)2294 zil_commit_writer(zilog_t *zilog, zil_commit_waiter_t *zcw)
2295 {
2296 	ASSERT(!MUTEX_HELD(&zilog->zl_lock));
2297 	ASSERT(spa_writeable(zilog->zl_spa));
2298 
2299 	mutex_enter(&zilog->zl_issuer_lock);
2300 
2301 	if (zcw->zcw_lwb != NULL || zcw->zcw_done) {
2302 		/*
2303 		 * It's possible that, while we were waiting to acquire
2304 		 * the "zl_issuer_lock", another thread committed this
2305 		 * waiter to an lwb. If that occurs, we bail out early,
2306 		 * without processing any of the zilog's queue of itxs.
2307 		 *
2308 		 * On certain workloads and system configurations, the
2309 		 * "zl_issuer_lock" can become highly contended. In an
2310 		 * attempt to reduce this contention, we immediately drop
2311 		 * the lock if the waiter has already been processed.
2312 		 *
2313 		 * We've measured this optimization to reduce CPU spent
2314 		 * contending on this lock by up to 5%, using a system
2315 		 * with 32 CPUs, low latency storage (~50 usec writes),
2316 		 * and 1024 threads performing sync writes.
2317 		 */
2318 		goto out;
2319 	}
2320 
2321 	zil_get_commit_list(zilog);
2322 	zil_prune_commit_list(zilog);
2323 	zil_process_commit_list(zilog);
2324 
2325 out:
2326 	mutex_exit(&zilog->zl_issuer_lock);
2327 }
2328 
2329 static void
zil_commit_waiter_timeout(zilog_t * zilog,zil_commit_waiter_t * zcw)2330 zil_commit_waiter_timeout(zilog_t *zilog, zil_commit_waiter_t *zcw)
2331 {
2332 	ASSERT(!MUTEX_HELD(&zilog->zl_issuer_lock));
2333 	ASSERT(MUTEX_HELD(&zcw->zcw_lock));
2334 	ASSERT3B(zcw->zcw_done, ==, B_FALSE);
2335 
2336 	lwb_t *lwb = zcw->zcw_lwb;
2337 	ASSERT3P(lwb, !=, NULL);
2338 	ASSERT3S(lwb->lwb_state, !=, LWB_STATE_CLOSED);
2339 
2340 	/*
2341 	 * If the lwb has already been issued by another thread, we can
2342 	 * immediately return since there's no work to be done (the
2343 	 * point of this function is to issue the lwb). Additionally, we
2344 	 * do this prior to acquiring the zl_issuer_lock, to avoid
2345 	 * acquiring it when it's not necessary to do so.
2346 	 */
2347 	if (lwb->lwb_state == LWB_STATE_ISSUED ||
2348 	    lwb->lwb_state == LWB_STATE_WRITE_DONE ||
2349 	    lwb->lwb_state == LWB_STATE_FLUSH_DONE)
2350 		return;
2351 
2352 	/*
2353 	 * In order to call zil_lwb_write_issue() we must hold the
2354 	 * zilog's "zl_issuer_lock". We can't simply acquire that lock,
2355 	 * since we're already holding the commit waiter's "zcw_lock",
2356 	 * and those two locks are aquired in the opposite order
2357 	 * elsewhere.
2358 	 */
2359 	mutex_exit(&zcw->zcw_lock);
2360 	mutex_enter(&zilog->zl_issuer_lock);
2361 	mutex_enter(&zcw->zcw_lock);
2362 
2363 	/*
2364 	 * Since we just dropped and re-acquired the commit waiter's
2365 	 * lock, we have to re-check to see if the waiter was marked
2366 	 * "done" during that process. If the waiter was marked "done",
2367 	 * the "lwb" pointer is no longer valid (it can be free'd after
2368 	 * the waiter is marked "done"), so without this check we could
2369 	 * wind up with a use-after-free error below.
2370 	 */
2371 	if (zcw->zcw_done)
2372 		goto out;
2373 
2374 	ASSERT3P(lwb, ==, zcw->zcw_lwb);
2375 
2376 	/*
2377 	 * We've already checked this above, but since we hadn't acquired
2378 	 * the zilog's zl_issuer_lock, we have to perform this check a
2379 	 * second time while holding the lock.
2380 	 *
2381 	 * We don't need to hold the zl_lock since the lwb cannot transition
2382 	 * from OPENED to ISSUED while we hold the zl_issuer_lock. The lwb
2383 	 * _can_ transition from ISSUED to DONE, but it's OK to race with
2384 	 * that transition since we treat the lwb the same, whether it's in
2385 	 * the ISSUED or DONE states.
2386 	 *
2387 	 * The important thing, is we treat the lwb differently depending on
2388 	 * if it's ISSUED or OPENED, and block any other threads that might
2389 	 * attempt to issue this lwb. For that reason we hold the
2390 	 * zl_issuer_lock when checking the lwb_state; we must not call
2391 	 * zil_lwb_write_issue() if the lwb had already been issued.
2392 	 *
2393 	 * See the comment above the lwb_state_t structure definition for
2394 	 * more details on the lwb states, and locking requirements.
2395 	 */
2396 	if (lwb->lwb_state == LWB_STATE_ISSUED ||
2397 	    lwb->lwb_state == LWB_STATE_WRITE_DONE ||
2398 	    lwb->lwb_state == LWB_STATE_FLUSH_DONE)
2399 		goto out;
2400 
2401 	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED);
2402 
2403 	/*
2404 	 * As described in the comments above zil_commit_waiter() and
2405 	 * zil_process_commit_list(), we need to issue this lwb's zio
2406 	 * since we've reached the commit waiter's timeout and it still
2407 	 * hasn't been issued.
2408 	 */
2409 	lwb_t *nlwb = zil_lwb_write_issue(zilog, lwb);
2410 
2411 	IMPLY(nlwb != NULL, lwb->lwb_state != LWB_STATE_OPENED);
2412 
2413 	/*
2414 	 * Since the lwb's zio hadn't been issued by the time this thread
2415 	 * reached its timeout, we reset the zilog's "zl_cur_used" field
2416 	 * to influence the zil block size selection algorithm.
2417 	 *
2418 	 * By having to issue the lwb's zio here, it means the size of the
2419 	 * lwb was too large, given the incoming throughput of itxs.  By
2420 	 * setting "zl_cur_used" to zero, we communicate this fact to the
2421 	 * block size selection algorithm, so it can take this informaiton
2422 	 * into account, and potentially select a smaller size for the
2423 	 * next lwb block that is allocated.
2424 	 */
2425 	zilog->zl_cur_used = 0;
2426 
2427 	if (nlwb == NULL) {
2428 		/*
2429 		 * When zil_lwb_write_issue() returns NULL, this
2430 		 * indicates zio_alloc_zil() failed to allocate the
2431 		 * "next" lwb on-disk. When this occurs, the ZIL write
2432 		 * pipeline must be stalled; see the comment within the
2433 		 * zil_commit_writer_stall() function for more details.
2434 		 *
2435 		 * We must drop the commit waiter's lock prior to
2436 		 * calling zil_commit_writer_stall() or else we can wind
2437 		 * up with the following deadlock:
2438 		 *
2439 		 * - This thread is waiting for the txg to sync while
2440 		 *   holding the waiter's lock; txg_wait_synced() is
2441 		 *   used within txg_commit_writer_stall().
2442 		 *
2443 		 * - The txg can't sync because it is waiting for this
2444 		 *   lwb's zio callback to call dmu_tx_commit().
2445 		 *
2446 		 * - The lwb's zio callback can't call dmu_tx_commit()
2447 		 *   because it's blocked trying to acquire the waiter's
2448 		 *   lock, which occurs prior to calling dmu_tx_commit()
2449 		 */
2450 		mutex_exit(&zcw->zcw_lock);
2451 		zil_commit_writer_stall(zilog);
2452 		mutex_enter(&zcw->zcw_lock);
2453 	}
2454 
2455 out:
2456 	mutex_exit(&zilog->zl_issuer_lock);
2457 	ASSERT(MUTEX_HELD(&zcw->zcw_lock));
2458 }
2459 
2460 /*
2461  * This function is responsible for performing the following two tasks:
2462  *
2463  * 1. its primary responsibility is to block until the given "commit
2464  *    waiter" is considered "done".
2465  *
2466  * 2. its secondary responsibility is to issue the zio for the lwb that
2467  *    the given "commit waiter" is waiting on, if this function has
2468  *    waited "long enough" and the lwb is still in the "open" state.
2469  *
2470  * Given a sufficient amount of itxs being generated and written using
2471  * the ZIL, the lwb's zio will be issued via the zil_lwb_commit()
2472  * function. If this does not occur, this secondary responsibility will
2473  * ensure the lwb is issued even if there is not other synchronous
2474  * activity on the system.
2475  *
2476  * For more details, see zil_process_commit_list(); more specifically,
2477  * the comment at the bottom of that function.
2478  */
2479 static void
zil_commit_waiter(zilog_t * zilog,zil_commit_waiter_t * zcw)2480 zil_commit_waiter(zilog_t *zilog, zil_commit_waiter_t *zcw)
2481 {
2482 	ASSERT(!MUTEX_HELD(&zilog->zl_lock));
2483 	ASSERT(!MUTEX_HELD(&zilog->zl_issuer_lock));
2484 	ASSERT(spa_writeable(zilog->zl_spa));
2485 
2486 	mutex_enter(&zcw->zcw_lock);
2487 
2488 	/*
2489 	 * The timeout is scaled based on the lwb latency to avoid
2490 	 * significantly impacting the latency of each individual itx.
2491 	 * For more details, see the comment at the bottom of the
2492 	 * zil_process_commit_list() function.
2493 	 */
2494 	int pct = MAX(zfs_commit_timeout_pct, 1);
2495 	hrtime_t sleep = (zilog->zl_last_lwb_latency * pct) / 100;
2496 	hrtime_t wakeup = gethrtime() + sleep;
2497 	boolean_t timedout = B_FALSE;
2498 
2499 	while (!zcw->zcw_done) {
2500 		ASSERT(MUTEX_HELD(&zcw->zcw_lock));
2501 
2502 		lwb_t *lwb = zcw->zcw_lwb;
2503 
2504 		/*
2505 		 * Usually, the waiter will have a non-NULL lwb field here,
2506 		 * but it's possible for it to be NULL as a result of
2507 		 * zil_commit() racing with spa_sync().
2508 		 *
2509 		 * When zil_clean() is called, it's possible for the itxg
2510 		 * list (which may be cleaned via a taskq) to contain
2511 		 * commit itxs. When this occurs, the commit waiters linked
2512 		 * off of these commit itxs will not be committed to an
2513 		 * lwb.  Additionally, these commit waiters will not be
2514 		 * marked done until zil_commit_waiter_skip() is called via
2515 		 * zil_itxg_clean().
2516 		 *
2517 		 * Thus, it's possible for this commit waiter (i.e. the
2518 		 * "zcw" variable) to be found in this "in between" state;
2519 		 * where it's "zcw_lwb" field is NULL, and it hasn't yet
2520 		 * been skipped, so it's "zcw_done" field is still B_FALSE.
2521 		 */
2522 		IMPLY(lwb != NULL, lwb->lwb_state != LWB_STATE_CLOSED);
2523 
2524 		if (lwb != NULL && lwb->lwb_state == LWB_STATE_OPENED) {
2525 			ASSERT3B(timedout, ==, B_FALSE);
2526 
2527 			/*
2528 			 * If the lwb hasn't been issued yet, then we
2529 			 * need to wait with a timeout, in case this
2530 			 * function needs to issue the lwb after the
2531 			 * timeout is reached; responsibility (2) from
2532 			 * the comment above this function.
2533 			 */
2534 			clock_t timeleft = cv_timedwait_hires(&zcw->zcw_cv,
2535 			    &zcw->zcw_lock, wakeup, USEC2NSEC(1),
2536 			    CALLOUT_FLAG_ABSOLUTE);
2537 
2538 			if (timeleft >= 0 || zcw->zcw_done)
2539 				continue;
2540 
2541 			timedout = B_TRUE;
2542 			zil_commit_waiter_timeout(zilog, zcw);
2543 
2544 			if (!zcw->zcw_done) {
2545 				/*
2546 				 * If the commit waiter has already been
2547 				 * marked "done", it's possible for the
2548 				 * waiter's lwb structure to have already
2549 				 * been freed.  Thus, we can only reliably
2550 				 * make these assertions if the waiter
2551 				 * isn't done.
2552 				 */
2553 				ASSERT3P(lwb, ==, zcw->zcw_lwb);
2554 				ASSERT3S(lwb->lwb_state, !=, LWB_STATE_OPENED);
2555 			}
2556 		} else {
2557 			/*
2558 			 * If the lwb isn't open, then it must have already
2559 			 * been issued. In that case, there's no need to
2560 			 * use a timeout when waiting for the lwb to
2561 			 * complete.
2562 			 *
2563 			 * Additionally, if the lwb is NULL, the waiter
2564 			 * will soon be signalled and marked done via
2565 			 * zil_clean() and zil_itxg_clean(), so no timeout
2566 			 * is required.
2567 			 */
2568 
2569 			IMPLY(lwb != NULL,
2570 			    lwb->lwb_state == LWB_STATE_ISSUED ||
2571 			    lwb->lwb_state == LWB_STATE_WRITE_DONE ||
2572 			    lwb->lwb_state == LWB_STATE_FLUSH_DONE);
2573 			cv_wait(&zcw->zcw_cv, &zcw->zcw_lock);
2574 		}
2575 	}
2576 
2577 	mutex_exit(&zcw->zcw_lock);
2578 }
2579 
2580 static zil_commit_waiter_t *
zil_alloc_commit_waiter()2581 zil_alloc_commit_waiter()
2582 {
2583 	zil_commit_waiter_t *zcw = kmem_cache_alloc(zil_zcw_cache, KM_SLEEP);
2584 
2585 	cv_init(&zcw->zcw_cv, NULL, CV_DEFAULT, NULL);
2586 	mutex_init(&zcw->zcw_lock, NULL, MUTEX_DEFAULT, NULL);
2587 	list_link_init(&zcw->zcw_node);
2588 	zcw->zcw_lwb = NULL;
2589 	zcw->zcw_done = B_FALSE;
2590 	zcw->zcw_zio_error = 0;
2591 
2592 	return (zcw);
2593 }
2594 
2595 static void
zil_free_commit_waiter(zil_commit_waiter_t * zcw)2596 zil_free_commit_waiter(zil_commit_waiter_t *zcw)
2597 {
2598 	ASSERT(!list_link_active(&zcw->zcw_node));
2599 	ASSERT3P(zcw->zcw_lwb, ==, NULL);
2600 	ASSERT3B(zcw->zcw_done, ==, B_TRUE);
2601 	mutex_destroy(&zcw->zcw_lock);
2602 	cv_destroy(&zcw->zcw_cv);
2603 	kmem_cache_free(zil_zcw_cache, zcw);
2604 }
2605 
2606 /*
2607  * This function is used to create a TX_COMMIT itx and assign it. This
2608  * way, it will be linked into the ZIL's list of synchronous itxs, and
2609  * then later committed to an lwb (or skipped) when
2610  * zil_process_commit_list() is called.
2611  */
2612 static void
zil_commit_itx_assign(zilog_t * zilog,zil_commit_waiter_t * zcw)2613 zil_commit_itx_assign(zilog_t *zilog, zil_commit_waiter_t *zcw)
2614 {
2615 	dmu_tx_t *tx = dmu_tx_create(zilog->zl_os);
2616 	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
2617 
2618 	itx_t *itx = zil_itx_create(TX_COMMIT, sizeof (lr_t));
2619 	itx->itx_sync = B_TRUE;
2620 	itx->itx_private = zcw;
2621 
2622 	zil_itx_assign(zilog, itx, tx);
2623 
2624 	dmu_tx_commit(tx);
2625 }
2626 
2627 /*
2628  * Commit ZFS Intent Log transactions (itxs) to stable storage.
2629  *
2630  * When writing ZIL transactions to the on-disk representation of the
2631  * ZIL, the itxs are committed to a Log Write Block (lwb). Multiple
2632  * itxs can be committed to a single lwb. Once a lwb is written and
2633  * committed to stable storage (i.e. the lwb is written, and vdevs have
2634  * been flushed), each itx that was committed to that lwb is also
2635  * considered to be committed to stable storage.
2636  *
2637  * When an itx is committed to an lwb, the log record (lr_t) contained
2638  * by the itx is copied into the lwb's zio buffer, and once this buffer
2639  * is written to disk, it becomes an on-disk ZIL block.
2640  *
2641  * As itxs are generated, they're inserted into the ZIL's queue of
2642  * uncommitted itxs. The semantics of zil_commit() are such that it will
2643  * block until all itxs that were in the queue when it was called, are
2644  * committed to stable storage.
2645  *
2646  * If "foid" is zero, this means all "synchronous" and "asynchronous"
2647  * itxs, for all objects in the dataset, will be committed to stable
2648  * storage prior to zil_commit() returning. If "foid" is non-zero, all
2649  * "synchronous" itxs for all objects, but only "asynchronous" itxs
2650  * that correspond to the foid passed in, will be committed to stable
2651  * storage prior to zil_commit() returning.
2652  *
2653  * Generally speaking, when zil_commit() is called, the consumer doesn't
2654  * actually care about _all_ of the uncommitted itxs. Instead, they're
2655  * simply trying to waiting for a specific itx to be committed to disk,
2656  * but the interface(s) for interacting with the ZIL don't allow such
2657  * fine-grained communication. A better interface would allow a consumer
2658  * to create and assign an itx, and then pass a reference to this itx to
2659  * zil_commit(); such that zil_commit() would return as soon as that
2660  * specific itx was committed to disk (instead of waiting for _all_
2661  * itxs to be committed).
2662  *
2663  * When a thread calls zil_commit() a special "commit itx" will be
2664  * generated, along with a corresponding "waiter" for this commit itx.
2665  * zil_commit() will wait on this waiter's CV, such that when the waiter
2666  * is marked done, and signalled, zil_commit() will return.
2667  *
2668  * This commit itx is inserted into the queue of uncommitted itxs. This
2669  * provides an easy mechanism for determining which itxs were in the
2670  * queue prior to zil_commit() having been called, and which itxs were
2671  * added after zil_commit() was called.
2672  *
2673  * The commit it is special; it doesn't have any on-disk representation.
2674  * When a commit itx is "committed" to an lwb, the waiter associated
2675  * with it is linked onto the lwb's list of waiters. Then, when that lwb
2676  * completes, each waiter on the lwb's list is marked done and signalled
2677  * -- allowing the thread waiting on the waiter to return from zil_commit().
2678  *
2679  * It's important to point out a few critical factors that allow us
2680  * to make use of the commit itxs, commit waiters, per-lwb lists of
2681  * commit waiters, and zio completion callbacks like we're doing:
2682  *
2683  *   1. The list of waiters for each lwb is traversed, and each commit
2684  *      waiter is marked "done" and signalled, in the zio completion
2685  *      callback of the lwb's zio[*].
2686  *
2687  *      * Actually, the waiters are signalled in the zio completion
2688  *        callback of the root zio for the DKIOCFLUSHWRITECACHE commands
2689  *        that are sent to the vdevs upon completion of the lwb zio.
2690  *
2691  *   2. When the itxs are inserted into the ZIL's queue of uncommitted
2692  *      itxs, the order in which they are inserted is preserved[*]; as
2693  *      itxs are added to the queue, they are added to the tail of
2694  *      in-memory linked lists.
2695  *
2696  *      When committing the itxs to lwbs (to be written to disk), they
2697  *      are committed in the same order in which the itxs were added to
2698  *      the uncommitted queue's linked list(s); i.e. the linked list of
2699  *      itxs to commit is traversed from head to tail, and each itx is
2700  *      committed to an lwb in that order.
2701  *
2702  *      * To clarify:
2703  *
2704  *        - the order of "sync" itxs is preserved w.r.t. other
2705  *          "sync" itxs, regardless of the corresponding objects.
2706  *        - the order of "async" itxs is preserved w.r.t. other
2707  *          "async" itxs corresponding to the same object.
2708  *        - the order of "async" itxs is *not* preserved w.r.t. other
2709  *          "async" itxs corresponding to different objects.
2710  *        - the order of "sync" itxs w.r.t. "async" itxs (or vice
2711  *          versa) is *not* preserved, even for itxs that correspond
2712  *          to the same object.
2713  *
2714  *      For more details, see: zil_itx_assign(), zil_async_to_sync(),
2715  *      zil_get_commit_list(), and zil_process_commit_list().
2716  *
2717  *   3. The lwbs represent a linked list of blocks on disk. Thus, any
2718  *      lwb cannot be considered committed to stable storage, until its
2719  *      "previous" lwb is also committed to stable storage. This fact,
2720  *      coupled with the fact described above, means that itxs are
2721  *      committed in (roughly) the order in which they were generated.
2722  *      This is essential because itxs are dependent on prior itxs.
2723  *      Thus, we *must not* deem an itx as being committed to stable
2724  *      storage, until *all* prior itxs have also been committed to
2725  *      stable storage.
2726  *
2727  *      To enforce this ordering of lwb zio's, while still leveraging as
2728  *      much of the underlying storage performance as possible, we rely
2729  *      on two fundamental concepts:
2730  *
2731  *          1. The creation and issuance of lwb zio's is protected by
2732  *             the zilog's "zl_issuer_lock", which ensures only a single
2733  *             thread is creating and/or issuing lwb's at a time
2734  *          2. The "previous" lwb is a child of the "current" lwb
2735  *             (leveraging the zio parent-child depenency graph)
2736  *
2737  *      By relying on this parent-child zio relationship, we can have
2738  *      many lwb zio's concurrently issued to the underlying storage,
2739  *      but the order in which they complete will be the same order in
2740  *      which they were created.
2741  */
2742 void
zil_commit(zilog_t * zilog,uint64_t foid)2743 zil_commit(zilog_t *zilog, uint64_t foid)
2744 {
2745 	/*
2746 	 * We should never attempt to call zil_commit on a snapshot for
2747 	 * a couple of reasons:
2748 	 *
2749 	 * 1. A snapshot may never be modified, thus it cannot have any
2750 	 *    in-flight itxs that would have modified the dataset.
2751 	 *
2752 	 * 2. By design, when zil_commit() is called, a commit itx will
2753 	 *    be assigned to this zilog; as a result, the zilog will be
2754 	 *    dirtied. We must not dirty the zilog of a snapshot; there's
2755 	 *    checks in the code that enforce this invariant, and will
2756 	 *    cause a panic if it's not upheld.
2757 	 */
2758 	ASSERT3B(dmu_objset_is_snapshot(zilog->zl_os), ==, B_FALSE);
2759 
2760 	if (zilog->zl_sync == ZFS_SYNC_DISABLED)
2761 		return;
2762 
2763 	if (!spa_writeable(zilog->zl_spa)) {
2764 		/*
2765 		 * If the SPA is not writable, there should never be any
2766 		 * pending itxs waiting to be committed to disk. If that
2767 		 * weren't true, we'd skip writing those itxs out, and
2768 		 * would break the sematics of zil_commit(); thus, we're
2769 		 * verifying that truth before we return to the caller.
2770 		 */
2771 		ASSERT(list_is_empty(&zilog->zl_lwb_list));
2772 		ASSERT3P(zilog->zl_last_lwb_opened, ==, NULL);
2773 		for (int i = 0; i < TXG_SIZE; i++)
2774 			ASSERT3P(zilog->zl_itxg[i].itxg_itxs, ==, NULL);
2775 		return;
2776 	}
2777 
2778 	/*
2779 	 * If the ZIL is suspended, we don't want to dirty it by calling
2780 	 * zil_commit_itx_assign() below, nor can we write out
2781 	 * lwbs like would be done in zil_commit_write(). Thus, we
2782 	 * simply rely on txg_wait_synced() to maintain the necessary
2783 	 * semantics, and avoid calling those functions altogether.
2784 	 */
2785 	if (zilog->zl_suspend > 0) {
2786 		txg_wait_synced(zilog->zl_dmu_pool, 0);
2787 		return;
2788 	}
2789 
2790 	zil_commit_impl(zilog, foid);
2791 }
2792 
2793 void
zil_commit_impl(zilog_t * zilog,uint64_t foid)2794 zil_commit_impl(zilog_t *zilog, uint64_t foid)
2795 {
2796 	/*
2797 	 * Move the "async" itxs for the specified foid to the "sync"
2798 	 * queues, such that they will be later committed (or skipped)
2799 	 * to an lwb when zil_process_commit_list() is called.
2800 	 *
2801 	 * Since these "async" itxs must be committed prior to this
2802 	 * call to zil_commit returning, we must perform this operation
2803 	 * before we call zil_commit_itx_assign().
2804 	 */
2805 	zil_async_to_sync(zilog, foid);
2806 
2807 	/*
2808 	 * We allocate a new "waiter" structure which will initially be
2809 	 * linked to the commit itx using the itx's "itx_private" field.
2810 	 * Since the commit itx doesn't represent any on-disk state,
2811 	 * when it's committed to an lwb, rather than copying the its
2812 	 * lr_t into the lwb's buffer, the commit itx's "waiter" will be
2813 	 * added to the lwb's list of waiters. Then, when the lwb is
2814 	 * committed to stable storage, each waiter in the lwb's list of
2815 	 * waiters will be marked "done", and signalled.
2816 	 *
2817 	 * We must create the waiter and assign the commit itx prior to
2818 	 * calling zil_commit_writer(), or else our specific commit itx
2819 	 * is not guaranteed to be committed to an lwb prior to calling
2820 	 * zil_commit_waiter().
2821 	 */
2822 	zil_commit_waiter_t *zcw = zil_alloc_commit_waiter();
2823 	zil_commit_itx_assign(zilog, zcw);
2824 
2825 	zil_commit_writer(zilog, zcw);
2826 	zil_commit_waiter(zilog, zcw);
2827 
2828 	if (zcw->zcw_zio_error != 0) {
2829 		/*
2830 		 * If there was an error writing out the ZIL blocks that
2831 		 * this thread is waiting on, then we fallback to
2832 		 * relying on spa_sync() to write out the data this
2833 		 * thread is waiting on. Obviously this has performance
2834 		 * implications, but the expectation is for this to be
2835 		 * an exceptional case, and shouldn't occur often.
2836 		 */
2837 		DTRACE_PROBE2(zil__commit__io__error,
2838 		    zilog_t *, zilog, zil_commit_waiter_t *, zcw);
2839 		txg_wait_synced(zilog->zl_dmu_pool, 0);
2840 	}
2841 
2842 	zil_free_commit_waiter(zcw);
2843 }
2844 
2845 /*
2846  * Called in syncing context to free committed log blocks and update log header.
2847  */
2848 void
zil_sync(zilog_t * zilog,dmu_tx_t * tx)2849 zil_sync(zilog_t *zilog, dmu_tx_t *tx)
2850 {
2851 	zil_header_t *zh = zil_header_in_syncing_context(zilog);
2852 	uint64_t txg = dmu_tx_get_txg(tx);
2853 	spa_t *spa = zilog->zl_spa;
2854 	uint64_t *replayed_seq = &zilog->zl_replayed_seq[txg & TXG_MASK];
2855 	lwb_t *lwb;
2856 
2857 	/*
2858 	 * We don't zero out zl_destroy_txg, so make sure we don't try
2859 	 * to destroy it twice.
2860 	 */
2861 	if (spa_sync_pass(spa) != 1)
2862 		return;
2863 
2864 	mutex_enter(&zilog->zl_lock);
2865 
2866 	ASSERT(zilog->zl_stop_sync == 0);
2867 
2868 	if (*replayed_seq != 0) {
2869 		ASSERT(zh->zh_replay_seq < *replayed_seq);
2870 		zh->zh_replay_seq = *replayed_seq;
2871 		*replayed_seq = 0;
2872 	}
2873 
2874 	if (zilog->zl_destroy_txg == txg) {
2875 		blkptr_t blk = zh->zh_log;
2876 
2877 		ASSERT(list_head(&zilog->zl_lwb_list) == NULL);
2878 
2879 		bzero(zh, sizeof (zil_header_t));
2880 		bzero(zilog->zl_replayed_seq, sizeof (zilog->zl_replayed_seq));
2881 
2882 		if (zilog->zl_keep_first) {
2883 			/*
2884 			 * If this block was part of log chain that couldn't
2885 			 * be claimed because a device was missing during
2886 			 * zil_claim(), but that device later returns,
2887 			 * then this block could erroneously appear valid.
2888 			 * To guard against this, assign a new GUID to the new
2889 			 * log chain so it doesn't matter what blk points to.
2890 			 */
2891 			zil_init_log_chain(zilog, &blk);
2892 			zh->zh_log = blk;
2893 		}
2894 	}
2895 
2896 	while ((lwb = list_head(&zilog->zl_lwb_list)) != NULL) {
2897 		zh->zh_log = lwb->lwb_blk;
2898 		if (lwb->lwb_buf != NULL || lwb->lwb_max_txg > txg)
2899 			break;
2900 		list_remove(&zilog->zl_lwb_list, lwb);
2901 		zio_free(spa, txg, &lwb->lwb_blk);
2902 		zil_free_lwb(zilog, lwb);
2903 
2904 		/*
2905 		 * If we don't have anything left in the lwb list then
2906 		 * we've had an allocation failure and we need to zero
2907 		 * out the zil_header blkptr so that we don't end
2908 		 * up freeing the same block twice.
2909 		 */
2910 		if (list_head(&zilog->zl_lwb_list) == NULL)
2911 			BP_ZERO(&zh->zh_log);
2912 	}
2913 	mutex_exit(&zilog->zl_lock);
2914 }
2915 
2916 /* ARGSUSED */
2917 static int
zil_lwb_cons(void * vbuf,void * unused,int kmflag)2918 zil_lwb_cons(void *vbuf, void *unused, int kmflag)
2919 {
2920 	lwb_t *lwb = vbuf;
2921 	list_create(&lwb->lwb_waiters, sizeof (zil_commit_waiter_t),
2922 	    offsetof(zil_commit_waiter_t, zcw_node));
2923 	avl_create(&lwb->lwb_vdev_tree, zil_lwb_vdev_compare,
2924 	    sizeof (zil_vdev_node_t), offsetof(zil_vdev_node_t, zv_node));
2925 	mutex_init(&lwb->lwb_vdev_lock, NULL, MUTEX_DEFAULT, NULL);
2926 	return (0);
2927 }
2928 
2929 /* ARGSUSED */
2930 static void
zil_lwb_dest(void * vbuf,void * unused)2931 zil_lwb_dest(void *vbuf, void *unused)
2932 {
2933 	lwb_t *lwb = vbuf;
2934 	mutex_destroy(&lwb->lwb_vdev_lock);
2935 	avl_destroy(&lwb->lwb_vdev_tree);
2936 	list_destroy(&lwb->lwb_waiters);
2937 }
2938 
2939 void
zil_init(void)2940 zil_init(void)
2941 {
2942 	zil_lwb_cache = kmem_cache_create("zil_lwb_cache",
2943 	    sizeof (lwb_t), 0, zil_lwb_cons, zil_lwb_dest, NULL, NULL, NULL, 0);
2944 
2945 	zil_zcw_cache = kmem_cache_create("zil_zcw_cache",
2946 	    sizeof (zil_commit_waiter_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
2947 }
2948 
2949 void
zil_fini(void)2950 zil_fini(void)
2951 {
2952 	kmem_cache_destroy(zil_zcw_cache);
2953 	kmem_cache_destroy(zil_lwb_cache);
2954 }
2955 
2956 void
zil_set_sync(zilog_t * zilog,uint64_t sync)2957 zil_set_sync(zilog_t *zilog, uint64_t sync)
2958 {
2959 	zilog->zl_sync = sync;
2960 }
2961 
2962 void
zil_set_logbias(zilog_t * zilog,uint64_t logbias)2963 zil_set_logbias(zilog_t *zilog, uint64_t logbias)
2964 {
2965 	zilog->zl_logbias = logbias;
2966 }
2967 
2968 zilog_t *
zil_alloc(objset_t * os,zil_header_t * zh_phys)2969 zil_alloc(objset_t *os, zil_header_t *zh_phys)
2970 {
2971 	zilog_t *zilog;
2972 
2973 	zilog = kmem_zalloc(sizeof (zilog_t), KM_SLEEP);
2974 
2975 	zilog->zl_header = zh_phys;
2976 	zilog->zl_os = os;
2977 	zilog->zl_spa = dmu_objset_spa(os);
2978 	zilog->zl_dmu_pool = dmu_objset_pool(os);
2979 	zilog->zl_destroy_txg = TXG_INITIAL - 1;
2980 	zilog->zl_logbias = dmu_objset_logbias(os);
2981 	zilog->zl_sync = dmu_objset_syncprop(os);
2982 	zilog->zl_dirty_max_txg = 0;
2983 	zilog->zl_last_lwb_opened = NULL;
2984 	zilog->zl_last_lwb_latency = 0;
2985 
2986 	mutex_init(&zilog->zl_lock, NULL, MUTEX_DEFAULT, NULL);
2987 	mutex_init(&zilog->zl_issuer_lock, NULL, MUTEX_DEFAULT, NULL);
2988 
2989 	for (int i = 0; i < TXG_SIZE; i++) {
2990 		mutex_init(&zilog->zl_itxg[i].itxg_lock, NULL,
2991 		    MUTEX_DEFAULT, NULL);
2992 	}
2993 
2994 	list_create(&zilog->zl_lwb_list, sizeof (lwb_t),
2995 	    offsetof(lwb_t, lwb_node));
2996 
2997 	list_create(&zilog->zl_itx_commit_list, sizeof (itx_t),
2998 	    offsetof(itx_t, itx_node));
2999 
3000 	cv_init(&zilog->zl_cv_suspend, NULL, CV_DEFAULT, NULL);
3001 
3002 	return (zilog);
3003 }
3004 
3005 void
zil_free(zilog_t * zilog)3006 zil_free(zilog_t *zilog)
3007 {
3008 	zilog->zl_stop_sync = 1;
3009 
3010 	ASSERT0(zilog->zl_suspend);
3011 	ASSERT0(zilog->zl_suspending);
3012 
3013 	ASSERT(list_is_empty(&zilog->zl_lwb_list));
3014 	list_destroy(&zilog->zl_lwb_list);
3015 
3016 	ASSERT(list_is_empty(&zilog->zl_itx_commit_list));
3017 	list_destroy(&zilog->zl_itx_commit_list);
3018 
3019 	for (int i = 0; i < TXG_SIZE; i++) {
3020 		/*
3021 		 * It's possible for an itx to be generated that doesn't dirty
3022 		 * a txg (e.g. ztest TX_TRUNCATE). So there's no zil_clean()
3023 		 * callback to remove the entry. We remove those here.
3024 		 *
3025 		 * Also free up the ziltest itxs.
3026 		 */
3027 		if (zilog->zl_itxg[i].itxg_itxs)
3028 			zil_itxg_clean(zilog->zl_itxg[i].itxg_itxs);
3029 		mutex_destroy(&zilog->zl_itxg[i].itxg_lock);
3030 	}
3031 
3032 	mutex_destroy(&zilog->zl_issuer_lock);
3033 	mutex_destroy(&zilog->zl_lock);
3034 
3035 	cv_destroy(&zilog->zl_cv_suspend);
3036 
3037 	kmem_free(zilog, sizeof (zilog_t));
3038 }
3039 
3040 /*
3041  * Open an intent log.
3042  */
3043 zilog_t *
zil_open(objset_t * os,zil_get_data_t * get_data)3044 zil_open(objset_t *os, zil_get_data_t *get_data)
3045 {
3046 	zilog_t *zilog = dmu_objset_zil(os);
3047 
3048 	ASSERT3P(zilog->zl_get_data, ==, NULL);
3049 	ASSERT3P(zilog->zl_last_lwb_opened, ==, NULL);
3050 	ASSERT(list_is_empty(&zilog->zl_lwb_list));
3051 
3052 	zilog->zl_get_data = get_data;
3053 
3054 	return (zilog);
3055 }
3056 
3057 /*
3058  * Close an intent log.
3059  */
3060 void
zil_close(zilog_t * zilog)3061 zil_close(zilog_t *zilog)
3062 {
3063 	lwb_t *lwb;
3064 	uint64_t txg;
3065 
3066 	if (!dmu_objset_is_snapshot(zilog->zl_os)) {
3067 		zil_commit(zilog, 0);
3068 	} else {
3069 		ASSERT3P(list_tail(&zilog->zl_lwb_list), ==, NULL);
3070 		ASSERT0(zilog->zl_dirty_max_txg);
3071 		ASSERT3B(zilog_is_dirty(zilog), ==, B_FALSE);
3072 	}
3073 
3074 	mutex_enter(&zilog->zl_lock);
3075 	lwb = list_tail(&zilog->zl_lwb_list);
3076 	if (lwb == NULL)
3077 		txg = zilog->zl_dirty_max_txg;
3078 	else
3079 		txg = MAX(zilog->zl_dirty_max_txg, lwb->lwb_max_txg);
3080 	mutex_exit(&zilog->zl_lock);
3081 
3082 	/*
3083 	 * We need to use txg_wait_synced() to wait long enough for the
3084 	 * ZIL to be clean, and to wait for all pending lwbs to be
3085 	 * written out.
3086 	 */
3087 	if (txg != 0)
3088 		txg_wait_synced(zilog->zl_dmu_pool, txg);
3089 
3090 	if (zilog_is_dirty(zilog))
3091 		zfs_dbgmsg("zil (%p) is dirty, txg %llu", zilog, txg);
3092 	if (txg < spa_freeze_txg(zilog->zl_spa))
3093 		VERIFY(!zilog_is_dirty(zilog));
3094 
3095 	zilog->zl_get_data = NULL;
3096 
3097 	/*
3098 	 * We should have only one lwb left on the list; remove it now.
3099 	 */
3100 	mutex_enter(&zilog->zl_lock);
3101 	lwb = list_head(&zilog->zl_lwb_list);
3102 	if (lwb != NULL) {
3103 		ASSERT3P(lwb, ==, list_tail(&zilog->zl_lwb_list));
3104 		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED);
3105 		list_remove(&zilog->zl_lwb_list, lwb);
3106 		zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
3107 		zil_free_lwb(zilog, lwb);
3108 	}
3109 	mutex_exit(&zilog->zl_lock);
3110 }
3111 
3112 static char *suspend_tag = "zil suspending";
3113 
3114 /*
3115  * Suspend an intent log.  While in suspended mode, we still honor
3116  * synchronous semantics, but we rely on txg_wait_synced() to do it.
3117  * On old version pools, we suspend the log briefly when taking a
3118  * snapshot so that it will have an empty intent log.
3119  *
3120  * Long holds are not really intended to be used the way we do here --
3121  * held for such a short time.  A concurrent caller of dsl_dataset_long_held()
3122  * could fail.  Therefore we take pains to only put a long hold if it is
3123  * actually necessary.  Fortunately, it will only be necessary if the
3124  * objset is currently mounted (or the ZVOL equivalent).  In that case it
3125  * will already have a long hold, so we are not really making things any worse.
3126  *
3127  * Ideally, we would locate the existing long-holder (i.e. the zfsvfs_t or
3128  * zvol_state_t), and use their mechanism to prevent their hold from being
3129  * dropped (e.g. VFS_HOLD()).  However, that would be even more pain for
3130  * very little gain.
3131  *
3132  * if cookiep == NULL, this does both the suspend & resume.
3133  * Otherwise, it returns with the dataset "long held", and the cookie
3134  * should be passed into zil_resume().
3135  */
3136 int
zil_suspend(const char * osname,void ** cookiep)3137 zil_suspend(const char *osname, void **cookiep)
3138 {
3139 	objset_t *os;
3140 	zilog_t *zilog;
3141 	const zil_header_t *zh;
3142 	int error;
3143 
3144 	error = dmu_objset_hold(osname, suspend_tag, &os);
3145 	if (error != 0)
3146 		return (error);
3147 	zilog = dmu_objset_zil(os);
3148 
3149 	mutex_enter(&zilog->zl_lock);
3150 	zh = zilog->zl_header;
3151 
3152 	if (zh->zh_flags & ZIL_REPLAY_NEEDED) {		/* unplayed log */
3153 		mutex_exit(&zilog->zl_lock);
3154 		dmu_objset_rele(os, suspend_tag);
3155 		return (SET_ERROR(EBUSY));
3156 	}
3157 
3158 	/*
3159 	 * Don't put a long hold in the cases where we can avoid it.  This
3160 	 * is when there is no cookie so we are doing a suspend & resume
3161 	 * (i.e. called from zil_vdev_offline()), and there's nothing to do
3162 	 * for the suspend because it's already suspended, or there's no ZIL.
3163 	 */
3164 	if (cookiep == NULL && !zilog->zl_suspending &&
3165 	    (zilog->zl_suspend > 0 || BP_IS_HOLE(&zh->zh_log))) {
3166 		mutex_exit(&zilog->zl_lock);
3167 		dmu_objset_rele(os, suspend_tag);
3168 		return (0);
3169 	}
3170 
3171 	dsl_dataset_long_hold(dmu_objset_ds(os), suspend_tag);
3172 	dsl_pool_rele(dmu_objset_pool(os), suspend_tag);
3173 
3174 	zilog->zl_suspend++;
3175 
3176 	if (zilog->zl_suspend > 1) {
3177 		/*
3178 		 * Someone else is already suspending it.
3179 		 * Just wait for them to finish.
3180 		 */
3181 
3182 		while (zilog->zl_suspending)
3183 			cv_wait(&zilog->zl_cv_suspend, &zilog->zl_lock);
3184 		mutex_exit(&zilog->zl_lock);
3185 
3186 		if (cookiep == NULL)
3187 			zil_resume(os);
3188 		else
3189 			*cookiep = os;
3190 		return (0);
3191 	}
3192 
3193 	/*
3194 	 * If there is no pointer to an on-disk block, this ZIL must not
3195 	 * be active (e.g. filesystem not mounted), so there's nothing
3196 	 * to clean up.
3197 	 */
3198 	if (BP_IS_HOLE(&zh->zh_log)) {
3199 		ASSERT(cookiep != NULL); /* fast path already handled */
3200 
3201 		*cookiep = os;
3202 		mutex_exit(&zilog->zl_lock);
3203 		return (0);
3204 	}
3205 
3206 	/*
3207 	 * The ZIL has work to do. Ensure that the associated encryption
3208 	 * key will remain mapped while we are committing the log by
3209 	 * grabbing a reference to it. If the key isn't loaded we have no
3210 	 * choice but to return an error until the wrapping key is loaded.
3211 	 */
3212 	if (os->os_encrypted &&
3213 	    dsl_dataset_create_key_mapping(dmu_objset_ds(os)) != 0) {
3214 		zilog->zl_suspend--;
3215 		mutex_exit(&zilog->zl_lock);
3216 		dsl_dataset_long_rele(dmu_objset_ds(os), suspend_tag);
3217 		dsl_dataset_rele(dmu_objset_ds(os), suspend_tag);
3218 		return (SET_ERROR(EBUSY));
3219 	}
3220 
3221 	zilog->zl_suspending = B_TRUE;
3222 	mutex_exit(&zilog->zl_lock);
3223 
3224 	/*
3225 	 * We need to use zil_commit_impl to ensure we wait for all
3226 	 * LWB_STATE_OPENED and LWB_STATE_ISSUED lwb's to be committed
3227 	 * to disk before proceeding. If we used zil_commit instead, it
3228 	 * would just call txg_wait_synced(), because zl_suspend is set.
3229 	 * txg_wait_synced() doesn't wait for these lwb's to be
3230 	 * LWB_STATE_FLUSH_DONE before returning.
3231 	 */
3232 	zil_commit_impl(zilog, 0);
3233 
3234 	/*
3235 	 * Now that we've ensured all lwb's are LWB_STATE_DONE,
3236 	 * txg_wait_synced() will be called from within zil_destroy(),
3237 	 * which will ensure the data from the zilog has migrated to the
3238 	 * main pool before it returns.
3239 	 */
3240 	txg_wait_synced(zilog->zl_dmu_pool, 0);
3241 
3242 	zil_destroy(zilog, B_FALSE);
3243 
3244 	mutex_enter(&zilog->zl_lock);
3245 	zilog->zl_suspending = B_FALSE;
3246 	cv_broadcast(&zilog->zl_cv_suspend);
3247 	mutex_exit(&zilog->zl_lock);
3248 
3249 	if (os->os_encrypted)
3250 		dsl_dataset_remove_key_mapping(dmu_objset_ds(os));
3251 
3252 	if (cookiep == NULL)
3253 		zil_resume(os);
3254 	else
3255 		*cookiep = os;
3256 	return (0);
3257 }
3258 
3259 void
zil_resume(void * cookie)3260 zil_resume(void *cookie)
3261 {
3262 	objset_t *os = cookie;
3263 	zilog_t *zilog = dmu_objset_zil(os);
3264 
3265 	mutex_enter(&zilog->zl_lock);
3266 	ASSERT(zilog->zl_suspend != 0);
3267 	zilog->zl_suspend--;
3268 	mutex_exit(&zilog->zl_lock);
3269 	dsl_dataset_long_rele(dmu_objset_ds(os), suspend_tag);
3270 	dsl_dataset_rele(dmu_objset_ds(os), suspend_tag);
3271 }
3272 
3273 typedef struct zil_replay_arg {
3274 	zil_replay_func_t **zr_replay;
3275 	void		*zr_arg;
3276 	boolean_t	zr_byteswap;
3277 	char		*zr_lr;
3278 } zil_replay_arg_t;
3279 
3280 static int
zil_replay_error(zilog_t * zilog,lr_t * lr,int error)3281 zil_replay_error(zilog_t *zilog, lr_t *lr, int error)
3282 {
3283 	char name[ZFS_MAX_DATASET_NAME_LEN];
3284 
3285 	zilog->zl_replaying_seq--;	/* didn't actually replay this one */
3286 
3287 	dmu_objset_name(zilog->zl_os, name);
3288 
3289 	cmn_err(CE_WARN, "ZFS replay transaction error %d, "
3290 	    "dataset %s, seq 0x%llx, txtype %llu %s\n", error, name,
3291 	    (u_longlong_t)lr->lrc_seq,
3292 	    (u_longlong_t)(lr->lrc_txtype & ~TX_CI),
3293 	    (lr->lrc_txtype & TX_CI) ? "CI" : "");
3294 
3295 	return (error);
3296 }
3297 
3298 static int
zil_replay_log_record(zilog_t * zilog,lr_t * lr,void * zra,uint64_t claim_txg)3299 zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
3300 {
3301 	zil_replay_arg_t *zr = zra;
3302 	const zil_header_t *zh = zilog->zl_header;
3303 	uint64_t reclen = lr->lrc_reclen;
3304 	uint64_t txtype = lr->lrc_txtype;
3305 	int error = 0;
3306 
3307 	zilog->zl_replaying_seq = lr->lrc_seq;
3308 
3309 	if (lr->lrc_seq <= zh->zh_replay_seq)	/* already replayed */
3310 		return (0);
3311 
3312 	if (lr->lrc_txg < claim_txg)		/* already committed */
3313 		return (0);
3314 
3315 	/* Strip case-insensitive bit, still present in log record */
3316 	txtype &= ~TX_CI;
3317 
3318 	if (txtype == 0 || txtype >= TX_MAX_TYPE)
3319 		return (zil_replay_error(zilog, lr, EINVAL));
3320 
3321 	/*
3322 	 * If this record type can be logged out of order, the object
3323 	 * (lr_foid) may no longer exist.  That's legitimate, not an error.
3324 	 */
3325 	if (TX_OOO(txtype)) {
3326 		error = dmu_object_info(zilog->zl_os,
3327 		    LR_FOID_GET_OBJ(((lr_ooo_t *)lr)->lr_foid), NULL);
3328 		if (error == ENOENT || error == EEXIST)
3329 			return (0);
3330 	}
3331 
3332 	/*
3333 	 * Make a copy of the data so we can revise and extend it.
3334 	 */
3335 	bcopy(lr, zr->zr_lr, reclen);
3336 
3337 	/*
3338 	 * If this is a TX_WRITE with a blkptr, suck in the data.
3339 	 */
3340 	if (txtype == TX_WRITE && reclen == sizeof (lr_write_t)) {
3341 		error = zil_read_log_data(zilog, (lr_write_t *)lr,
3342 		    zr->zr_lr + reclen);
3343 		if (error != 0)
3344 			return (zil_replay_error(zilog, lr, error));
3345 	}
3346 
3347 	/*
3348 	 * The log block containing this lr may have been byteswapped
3349 	 * so that we can easily examine common fields like lrc_txtype.
3350 	 * However, the log is a mix of different record types, and only the
3351 	 * replay vectors know how to byteswap their records.  Therefore, if
3352 	 * the lr was byteswapped, undo it before invoking the replay vector.
3353 	 */
3354 	if (zr->zr_byteswap)
3355 		byteswap_uint64_array(zr->zr_lr, reclen);
3356 
3357 	/*
3358 	 * We must now do two things atomically: replay this log record,
3359 	 * and update the log header sequence number to reflect the fact that
3360 	 * we did so. At the end of each replay function the sequence number
3361 	 * is updated if we are in replay mode.
3362 	 */
3363 	error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lr, zr->zr_byteswap);
3364 	if (error != 0) {
3365 		/*
3366 		 * The DMU's dnode layer doesn't see removes until the txg
3367 		 * commits, so a subsequent claim can spuriously fail with
3368 		 * EEXIST. So if we receive any error we try syncing out
3369 		 * any removes then retry the transaction.  Note that we
3370 		 * specify B_FALSE for byteswap now, so we don't do it twice.
3371 		 */
3372 		txg_wait_synced(spa_get_dsl(zilog->zl_spa), 0);
3373 		error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lr, B_FALSE);
3374 		if (error != 0)
3375 			return (zil_replay_error(zilog, lr, error));
3376 	}
3377 	return (0);
3378 }
3379 
3380 /* ARGSUSED */
3381 static int
zil_incr_blks(zilog_t * zilog,blkptr_t * bp,void * arg,uint64_t claim_txg)3382 zil_incr_blks(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
3383 {
3384 	zilog->zl_replay_blks++;
3385 
3386 	return (0);
3387 }
3388 
3389 /*
3390  * If this dataset has a non-empty intent log, replay it and destroy it.
3391  */
3392 void
zil_replay(objset_t * os,void * arg,zil_replay_func_t * replay_func[TX_MAX_TYPE])3393 zil_replay(objset_t *os, void *arg, zil_replay_func_t *replay_func[TX_MAX_TYPE])
3394 {
3395 	zilog_t *zilog = dmu_objset_zil(os);
3396 	const zil_header_t *zh = zilog->zl_header;
3397 	zil_replay_arg_t zr;
3398 
3399 	if ((zh->zh_flags & ZIL_REPLAY_NEEDED) == 0) {
3400 		zil_destroy(zilog, B_TRUE);
3401 		return;
3402 	}
3403 
3404 	zr.zr_replay = replay_func;
3405 	zr.zr_arg = arg;
3406 	zr.zr_byteswap = BP_SHOULD_BYTESWAP(&zh->zh_log);
3407 	zr.zr_lr = kmem_alloc(2 * SPA_MAXBLOCKSIZE, KM_SLEEP);
3408 
3409 	/*
3410 	 * Wait for in-progress removes to sync before starting replay.
3411 	 */
3412 	txg_wait_synced(zilog->zl_dmu_pool, 0);
3413 
3414 	zilog->zl_replay = B_TRUE;
3415 	zilog->zl_replay_time = ddi_get_lbolt();
3416 	ASSERT(zilog->zl_replay_blks == 0);
3417 	(void) zil_parse(zilog, zil_incr_blks, zil_replay_log_record, &zr,
3418 	    zh->zh_claim_txg, B_TRUE);
3419 	kmem_free(zr.zr_lr, 2 * SPA_MAXBLOCKSIZE);
3420 
3421 	zil_destroy(zilog, B_FALSE);
3422 	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
3423 	zilog->zl_replay = B_FALSE;
3424 }
3425 
3426