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 */
90int zfs_commit_timeout_pct = 5;
91
92/*
93 * Disable intent logging replay.  This global ZIL switch affects all pools.
94 */
95int 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 */
103boolean_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 */
110uint64_t zil_slog_bulk = 768 * 1024;
111
112static kmem_cache_t *zil_lwb_cache;
113static kmem_cache_t *zil_zcw_cache;
114
115static 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
120static int
121zil_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 = AVL_CMP(DVA_GET_VDEV(dva1), DVA_GET_VDEV(dva2));
127	if (likely(cmp))
128		return (cmp);
129
130	return (AVL_CMP(DVA_GET_OFFSET(dva1), DVA_GET_OFFSET(dva2)));
131}
132
133static void
134zil_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
140static void
141zil_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
153int
154zil_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
176static zil_header_t *
177zil_header_in_syncing_context(zilog_t *zilog)
178{
179	return ((zil_header_t *)zilog->zl_header);
180}
181
182static void
183zil_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 */
196static int
197zil_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 */
275static int
276zil_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 */
320int
321zil_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	}
393done:
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 */
411static int
412zil_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 */
433static int
434zil_noop_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t first_txg)
435{
436	return (0);
437}
438
439static int
440zil_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
455static int
456zil_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 */
482static int
483zil_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
490static int
491zil_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
507static int
508zil_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 (AVL_CMP(v1, v2));
514}
515
516static lwb_t *
517zil_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
551static void
552zil_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 */
578void
579zilog_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 */
604boolean_t
605zilog_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 */
618boolean_t
619zilog_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 */
633static lwb_t *
634zil_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 */
707void
708zil_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
754void
755zil_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
762int
763zil_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 */
872int
873zil_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 */
947static void
948zil_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 */
963static void
964zil_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 */
990static void
991zil_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
1000void
1001zil_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
1024static void
1025zil_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
1060void
1061zil_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 */
1081static void
1082zil_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 */
1165static void
1166zil_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
1240static void
1241zil_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 */
1314static void
1315zil_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 */
1368uint64_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 */
1379static lwb_t *
1380zil_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
1511static lwb_t *
1512zil_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
1560cont:
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
1659itx_t *
1660zil_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
1675void
1676zil_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 */
1685static void
1686zil_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
1740static int
1741zil_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 (AVL_CMP(o1, o2));
1747}
1748
1749/*
1750 * Remove all async itx with the given oid.
1751 */
1752static void
1753zil_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
1797void
1798zil_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	 * Object ids can be re-instantiated in the next txg so
1806	 * remove any async transactions to avoid future leaks.
1807	 * This can happen if a fsync occurs on the re-instantiated
1808	 * object for a WR_INDIRECT or WR_NEED_COPY write, which gets
1809	 * the new file data and flushes a write record for the old object.
1810	 */
1811	if ((itx->itx_lr.lrc_txtype & ~TX_CI) == TX_REMOVE)
1812		zil_remove_async(zilog, itx->itx_oid);
1813
1814	/*
1815	 * Ensure the data of a renamed file is committed before the rename.
1816	 */
1817	if ((itx->itx_lr.lrc_txtype & ~TX_CI) == TX_RENAME)
1818		zil_async_to_sync(zilog, itx->itx_oid);
1819
1820	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX)
1821		txg = ZILTEST_TXG;
1822	else
1823		txg = dmu_tx_get_txg(tx);
1824
1825	itxg = &zilog->zl_itxg[txg & TXG_MASK];
1826	mutex_enter(&itxg->itxg_lock);
1827	itxs = itxg->itxg_itxs;
1828	if (itxg->itxg_txg != txg) {
1829		if (itxs != NULL) {
1830			/*
1831			 * The zil_clean callback hasn't got around to cleaning
1832			 * this itxg. Save the itxs for release below.
1833			 * This should be rare.
1834			 */
1835			zfs_dbgmsg("zil_itx_assign: missed itx cleanup for "
1836			    "txg %llu", itxg->itxg_txg);
1837			clean = itxg->itxg_itxs;
1838		}
1839		itxg->itxg_txg = txg;
1840		itxs = itxg->itxg_itxs = kmem_zalloc(sizeof (itxs_t), KM_SLEEP);
1841
1842		list_create(&itxs->i_sync_list, sizeof (itx_t),
1843		    offsetof(itx_t, itx_node));
1844		avl_create(&itxs->i_async_tree, zil_aitx_compare,
1845		    sizeof (itx_async_node_t),
1846		    offsetof(itx_async_node_t, ia_node));
1847	}
1848	if (itx->itx_sync) {
1849		list_insert_tail(&itxs->i_sync_list, itx);
1850	} else {
1851		avl_tree_t *t = &itxs->i_async_tree;
1852		uint64_t foid =
1853		    LR_FOID_GET_OBJ(((lr_ooo_t *)&itx->itx_lr)->lr_foid);
1854		itx_async_node_t *ian;
1855		avl_index_t where;
1856
1857		ian = avl_find(t, &foid, &where);
1858		if (ian == NULL) {
1859			ian = kmem_alloc(sizeof (itx_async_node_t), KM_SLEEP);
1860			list_create(&ian->ia_list, sizeof (itx_t),
1861			    offsetof(itx_t, itx_node));
1862			ian->ia_foid = foid;
1863			avl_insert(t, ian, where);
1864		}
1865		list_insert_tail(&ian->ia_list, itx);
1866	}
1867
1868	itx->itx_lr.lrc_txg = dmu_tx_get_txg(tx);
1869
1870	/*
1871	 * We don't want to dirty the ZIL using ZILTEST_TXG, because
1872	 * zil_clean() will never be called using ZILTEST_TXG. Thus, we
1873	 * need to be careful to always dirty the ZIL using the "real"
1874	 * TXG (not itxg_txg) even when the SPA is frozen.
1875	 */
1876	zilog_dirty(zilog, dmu_tx_get_txg(tx));
1877	mutex_exit(&itxg->itxg_lock);
1878
1879	/* Release the old itxs now we've dropped the lock */
1880	if (clean != NULL)
1881		zil_itxg_clean(clean);
1882}
1883
1884/*
1885 * If there are any in-memory intent log transactions which have now been
1886 * synced then start up a taskq to free them. We should only do this after we
1887 * have written out the uberblocks (i.e. txg has been comitted) so that
1888 * don't inadvertently clean out in-memory log records that would be required
1889 * by zil_commit().
1890 */
1891void
1892zil_clean(zilog_t *zilog, uint64_t synced_txg)
1893{
1894	itxg_t *itxg = &zilog->zl_itxg[synced_txg & TXG_MASK];
1895	itxs_t *clean_me;
1896
1897	ASSERT3U(synced_txg, <, ZILTEST_TXG);
1898
1899	mutex_enter(&itxg->itxg_lock);
1900	if (itxg->itxg_itxs == NULL || itxg->itxg_txg == ZILTEST_TXG) {
1901		mutex_exit(&itxg->itxg_lock);
1902		return;
1903	}
1904	ASSERT3U(itxg->itxg_txg, <=, synced_txg);
1905	ASSERT3U(itxg->itxg_txg, !=, 0);
1906	clean_me = itxg->itxg_itxs;
1907	itxg->itxg_itxs = NULL;
1908	itxg->itxg_txg = 0;
1909	mutex_exit(&itxg->itxg_lock);
1910	/*
1911	 * Preferably start a task queue to free up the old itxs but
1912	 * if taskq_dispatch can't allocate resources to do that then
1913	 * free it in-line. This should be rare. Note, using TQ_SLEEP
1914	 * created a bad performance problem.
1915	 */
1916	ASSERT3P(zilog->zl_dmu_pool, !=, NULL);
1917	ASSERT3P(zilog->zl_dmu_pool->dp_zil_clean_taskq, !=, NULL);
1918	if (taskq_dispatch(zilog->zl_dmu_pool->dp_zil_clean_taskq,
1919	    (void (*)(void *))zil_itxg_clean, clean_me, TQ_NOSLEEP) ==
1920	    TASKQID_INVALID)
1921		zil_itxg_clean(clean_me);
1922}
1923
1924/*
1925 * This function will traverse the queue of itxs that need to be
1926 * committed, and move them onto the ZIL's zl_itx_commit_list.
1927 */
1928static void
1929zil_get_commit_list(zilog_t *zilog)
1930{
1931	uint64_t otxg, txg;
1932	list_t *commit_list = &zilog->zl_itx_commit_list;
1933
1934	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
1935
1936	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */
1937		otxg = ZILTEST_TXG;
1938	else
1939		otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
1940
1941	/*
1942	 * This is inherently racy, since there is nothing to prevent
1943	 * the last synced txg from changing. That's okay since we'll
1944	 * only commit things in the future.
1945	 */
1946	for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
1947		itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
1948
1949		mutex_enter(&itxg->itxg_lock);
1950		if (itxg->itxg_txg != txg) {
1951			mutex_exit(&itxg->itxg_lock);
1952			continue;
1953		}
1954
1955		/*
1956		 * If we're adding itx records to the zl_itx_commit_list,
1957		 * then the zil better be dirty in this "txg". We can assert
1958		 * that here since we're holding the itxg_lock which will
1959		 * prevent spa_sync from cleaning it. Once we add the itxs
1960		 * to the zl_itx_commit_list we must commit it to disk even
1961		 * if it's unnecessary (i.e. the txg was synced).
1962		 */
1963		ASSERT(zilog_is_dirty_in_txg(zilog, txg) ||
1964		    spa_freeze_txg(zilog->zl_spa) != UINT64_MAX);
1965		list_move_tail(commit_list, &itxg->itxg_itxs->i_sync_list);
1966
1967		mutex_exit(&itxg->itxg_lock);
1968	}
1969}
1970
1971/*
1972 * Move the async itxs for a specified object to commit into sync lists.
1973 */
1974static void
1975zil_async_to_sync(zilog_t *zilog, uint64_t foid)
1976{
1977	uint64_t otxg, txg;
1978	itx_async_node_t *ian;
1979	avl_tree_t *t;
1980	avl_index_t where;
1981
1982	if (spa_freeze_txg(zilog->zl_spa) != UINT64_MAX) /* ziltest support */
1983		otxg = ZILTEST_TXG;
1984	else
1985		otxg = spa_last_synced_txg(zilog->zl_spa) + 1;
1986
1987	/*
1988	 * This is inherently racy, since there is nothing to prevent
1989	 * the last synced txg from changing.
1990	 */
1991	for (txg = otxg; txg < (otxg + TXG_CONCURRENT_STATES); txg++) {
1992		itxg_t *itxg = &zilog->zl_itxg[txg & TXG_MASK];
1993
1994		mutex_enter(&itxg->itxg_lock);
1995		if (itxg->itxg_txg != txg) {
1996			mutex_exit(&itxg->itxg_lock);
1997			continue;
1998		}
1999
2000		/*
2001		 * If a foid is specified then find that node and append its
2002		 * list. Otherwise walk the tree appending all the lists
2003		 * to the sync list. We add to the end rather than the
2004		 * beginning to ensure the create has happened.
2005		 */
2006		t = &itxg->itxg_itxs->i_async_tree;
2007		if (foid != 0) {
2008			ian = avl_find(t, &foid, &where);
2009			if (ian != NULL) {
2010				list_move_tail(&itxg->itxg_itxs->i_sync_list,
2011				    &ian->ia_list);
2012			}
2013		} else {
2014			void *cookie = NULL;
2015
2016			while ((ian = avl_destroy_nodes(t, &cookie)) != NULL) {
2017				list_move_tail(&itxg->itxg_itxs->i_sync_list,
2018				    &ian->ia_list);
2019				list_destroy(&ian->ia_list);
2020				kmem_free(ian, sizeof (itx_async_node_t));
2021			}
2022		}
2023		mutex_exit(&itxg->itxg_lock);
2024	}
2025}
2026
2027/*
2028 * This function will prune commit itxs that are at the head of the
2029 * commit list (it won't prune past the first non-commit itx), and
2030 * either: a) attach them to the last lwb that's still pending
2031 * completion, or b) skip them altogether.
2032 *
2033 * This is used as a performance optimization to prevent commit itxs
2034 * from generating new lwbs when it's unnecessary to do so.
2035 */
2036static void
2037zil_prune_commit_list(zilog_t *zilog)
2038{
2039	itx_t *itx;
2040
2041	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
2042
2043	while (itx = list_head(&zilog->zl_itx_commit_list)) {
2044		lr_t *lrc = &itx->itx_lr;
2045		if (lrc->lrc_txtype != TX_COMMIT)
2046			break;
2047
2048		mutex_enter(&zilog->zl_lock);
2049
2050		lwb_t *last_lwb = zilog->zl_last_lwb_opened;
2051		if (last_lwb == NULL ||
2052		    last_lwb->lwb_state == LWB_STATE_FLUSH_DONE) {
2053			/*
2054			 * All of the itxs this waiter was waiting on
2055			 * must have already completed (or there were
2056			 * never any itx's for it to wait on), so it's
2057			 * safe to skip this waiter and mark it done.
2058			 */
2059			zil_commit_waiter_skip(itx->itx_private);
2060		} else {
2061			zil_commit_waiter_link_lwb(itx->itx_private, last_lwb);
2062			itx->itx_private = NULL;
2063		}
2064
2065		mutex_exit(&zilog->zl_lock);
2066
2067		list_remove(&zilog->zl_itx_commit_list, itx);
2068		zil_itx_destroy(itx);
2069	}
2070
2071	IMPLY(itx != NULL, itx->itx_lr.lrc_txtype != TX_COMMIT);
2072}
2073
2074static void
2075zil_commit_writer_stall(zilog_t *zilog)
2076{
2077	/*
2078	 * When zio_alloc_zil() fails to allocate the next lwb block on
2079	 * disk, we must call txg_wait_synced() to ensure all of the
2080	 * lwbs in the zilog's zl_lwb_list are synced and then freed (in
2081	 * zil_sync()), such that any subsequent ZIL writer (i.e. a call
2082	 * to zil_process_commit_list()) will have to call zil_create(),
2083	 * and start a new ZIL chain.
2084	 *
2085	 * Since zil_alloc_zil() failed, the lwb that was previously
2086	 * issued does not have a pointer to the "next" lwb on disk.
2087	 * Thus, if another ZIL writer thread was to allocate the "next"
2088	 * on-disk lwb, that block could be leaked in the event of a
2089	 * crash (because the previous lwb on-disk would not point to
2090	 * it).
2091	 *
2092	 * We must hold the zilog's zl_issuer_lock while we do this, to
2093	 * ensure no new threads enter zil_process_commit_list() until
2094	 * all lwb's in the zl_lwb_list have been synced and freed
2095	 * (which is achieved via the txg_wait_synced() call).
2096	 */
2097	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
2098	txg_wait_synced(zilog->zl_dmu_pool, 0);
2099	ASSERT3P(list_tail(&zilog->zl_lwb_list), ==, NULL);
2100}
2101
2102/*
2103 * This function will traverse the commit list, creating new lwbs as
2104 * needed, and committing the itxs from the commit list to these newly
2105 * created lwbs. Additionally, as a new lwb is created, the previous
2106 * lwb will be issued to the zio layer to be written to disk.
2107 */
2108static void
2109zil_process_commit_list(zilog_t *zilog)
2110{
2111	spa_t *spa = zilog->zl_spa;
2112	list_t nolwb_waiters;
2113	lwb_t *lwb;
2114	itx_t *itx;
2115
2116	ASSERT(MUTEX_HELD(&zilog->zl_issuer_lock));
2117
2118	/*
2119	 * Return if there's nothing to commit before we dirty the fs by
2120	 * calling zil_create().
2121	 */
2122	if (list_head(&zilog->zl_itx_commit_list) == NULL)
2123		return;
2124
2125	list_create(&nolwb_waiters, sizeof (zil_commit_waiter_t),
2126	    offsetof(zil_commit_waiter_t, zcw_node));
2127
2128	lwb = list_tail(&zilog->zl_lwb_list);
2129	if (lwb == NULL) {
2130		lwb = zil_create(zilog);
2131	} else {
2132		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED);
2133		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_WRITE_DONE);
2134		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_FLUSH_DONE);
2135	}
2136
2137	while (itx = list_head(&zilog->zl_itx_commit_list)) {
2138		lr_t *lrc = &itx->itx_lr;
2139		uint64_t txg = lrc->lrc_txg;
2140
2141		ASSERT3U(txg, !=, 0);
2142
2143		if (lrc->lrc_txtype == TX_COMMIT) {
2144			DTRACE_PROBE2(zil__process__commit__itx,
2145			    zilog_t *, zilog, itx_t *, itx);
2146		} else {
2147			DTRACE_PROBE2(zil__process__normal__itx,
2148			    zilog_t *, zilog, itx_t *, itx);
2149		}
2150
2151		boolean_t synced = txg <= spa_last_synced_txg(spa);
2152		boolean_t frozen = txg > spa_freeze_txg(spa);
2153
2154		/*
2155		 * If the txg of this itx has already been synced out, then
2156		 * we don't need to commit this itx to an lwb. This is
2157		 * because the data of this itx will have already been
2158		 * written to the main pool. This is inherently racy, and
2159		 * it's still ok to commit an itx whose txg has already
2160		 * been synced; this will result in a write that's
2161		 * unnecessary, but will do no harm.
2162		 *
2163		 * With that said, we always want to commit TX_COMMIT itxs
2164		 * to an lwb, regardless of whether or not that itx's txg
2165		 * has been synced out. We do this to ensure any OPENED lwb
2166		 * will always have at least one zil_commit_waiter_t linked
2167		 * to the lwb.
2168		 *
2169		 * As a counter-example, if we skipped TX_COMMIT itx's
2170		 * whose txg had already been synced, the following
2171		 * situation could occur if we happened to be racing with
2172		 * spa_sync:
2173		 *
2174		 * 1. we commit a non-TX_COMMIT itx to an lwb, where the
2175		 *    itx's txg is 10 and the last synced txg is 9.
2176		 * 2. spa_sync finishes syncing out txg 10.
2177		 * 3. we move to the next itx in the list, it's a TX_COMMIT
2178		 *    whose txg is 10, so we skip it rather than committing
2179		 *    it to the lwb used in (1).
2180		 *
2181		 * If the itx that is skipped in (3) is the last TX_COMMIT
2182		 * itx in the commit list, than it's possible for the lwb
2183		 * used in (1) to remain in the OPENED state indefinitely.
2184		 *
2185		 * To prevent the above scenario from occuring, ensuring
2186		 * that once an lwb is OPENED it will transition to ISSUED
2187		 * and eventually DONE, we always commit TX_COMMIT itx's to
2188		 * an lwb here, even if that itx's txg has already been
2189		 * synced.
2190		 *
2191		 * Finally, if the pool is frozen, we _always_ commit the
2192		 * itx.  The point of freezing the pool is to prevent data
2193		 * from being written to the main pool via spa_sync, and
2194		 * instead rely solely on the ZIL to persistently store the
2195		 * data; i.e.  when the pool is frozen, the last synced txg
2196		 * value can't be trusted.
2197		 */
2198		if (frozen || !synced || lrc->lrc_txtype == TX_COMMIT) {
2199			if (lwb != NULL) {
2200				lwb = zil_lwb_commit(zilog, itx, lwb);
2201			} else if (lrc->lrc_txtype == TX_COMMIT) {
2202				ASSERT3P(lwb, ==, NULL);
2203				zil_commit_waiter_link_nolwb(
2204				    itx->itx_private, &nolwb_waiters);
2205			}
2206		}
2207
2208		list_remove(&zilog->zl_itx_commit_list, itx);
2209		zil_itx_destroy(itx);
2210	}
2211
2212	if (lwb == NULL) {
2213		/*
2214		 * This indicates zio_alloc_zil() failed to allocate the
2215		 * "next" lwb on-disk. When this happens, we must stall
2216		 * the ZIL write pipeline; see the comment within
2217		 * zil_commit_writer_stall() for more details.
2218		 */
2219		zil_commit_writer_stall(zilog);
2220
2221		/*
2222		 * Additionally, we have to signal and mark the "nolwb"
2223		 * waiters as "done" here, since without an lwb, we
2224		 * can't do this via zil_lwb_flush_vdevs_done() like
2225		 * normal.
2226		 */
2227		zil_commit_waiter_t *zcw;
2228		while (zcw = list_head(&nolwb_waiters)) {
2229			zil_commit_waiter_skip(zcw);
2230			list_remove(&nolwb_waiters, zcw);
2231		}
2232	} else {
2233		ASSERT(list_is_empty(&nolwb_waiters));
2234		ASSERT3P(lwb, !=, NULL);
2235		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED);
2236		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_WRITE_DONE);
2237		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_FLUSH_DONE);
2238
2239		/*
2240		 * At this point, the ZIL block pointed at by the "lwb"
2241		 * variable is in one of the following states: "closed"
2242		 * or "open".
2243		 *
2244		 * If its "closed", then no itxs have been committed to
2245		 * it, so there's no point in issuing its zio (i.e.
2246		 * it's "empty").
2247		 *
2248		 * If its "open" state, then it contains one or more
2249		 * itxs that eventually need to be committed to stable
2250		 * storage. In this case we intentionally do not issue
2251		 * the lwb's zio to disk yet, and instead rely on one of
2252		 * the following two mechanisms for issuing the zio:
2253		 *
2254		 * 1. Ideally, there will be more ZIL activity occuring
2255		 * on the system, such that this function will be
2256		 * immediately called again (not necessarily by the same
2257		 * thread) and this lwb's zio will be issued via
2258		 * zil_lwb_commit(). This way, the lwb is guaranteed to
2259		 * be "full" when it is issued to disk, and we'll make
2260		 * use of the lwb's size the best we can.
2261		 *
2262		 * 2. If there isn't sufficient ZIL activity occuring on
2263		 * the system, such that this lwb's zio isn't issued via
2264		 * zil_lwb_commit(), zil_commit_waiter() will issue the
2265		 * lwb's zio. If this occurs, the lwb is not guaranteed
2266		 * to be "full" by the time its zio is issued, and means
2267		 * the size of the lwb was "too large" given the amount
2268		 * of ZIL activity occuring on the system at that time.
2269		 *
2270		 * We do this for a couple of reasons:
2271		 *
2272		 * 1. To try and reduce the number of IOPs needed to
2273		 * write the same number of itxs. If an lwb has space
2274		 * available in it's buffer for more itxs, and more itxs
2275		 * will be committed relatively soon (relative to the
2276		 * latency of performing a write), then it's beneficial
2277		 * to wait for these "next" itxs. This way, more itxs
2278		 * can be committed to stable storage with fewer writes.
2279		 *
2280		 * 2. To try and use the largest lwb block size that the
2281		 * incoming rate of itxs can support. Again, this is to
2282		 * try and pack as many itxs into as few lwbs as
2283		 * possible, without significantly impacting the latency
2284		 * of each individual itx.
2285		 */
2286	}
2287}
2288
2289/*
2290 * This function is responsible for ensuring the passed in commit waiter
2291 * (and associated commit itx) is committed to an lwb. If the waiter is
2292 * not already committed to an lwb, all itxs in the zilog's queue of
2293 * itxs will be processed. The assumption is the passed in waiter's
2294 * commit itx will found in the queue just like the other non-commit
2295 * itxs, such that when the entire queue is processed, the waiter will
2296 * have been commited to an lwb.
2297 *
2298 * The lwb associated with the passed in waiter is not guaranteed to
2299 * have been issued by the time this function completes. If the lwb is
2300 * not issued, we rely on future calls to zil_commit_writer() to issue
2301 * the lwb, or the timeout mechanism found in zil_commit_waiter().
2302 */
2303static void
2304zil_commit_writer(zilog_t *zilog, zil_commit_waiter_t *zcw)
2305{
2306	ASSERT(!MUTEX_HELD(&zilog->zl_lock));
2307	ASSERT(spa_writeable(zilog->zl_spa));
2308
2309	mutex_enter(&zilog->zl_issuer_lock);
2310
2311	if (zcw->zcw_lwb != NULL || zcw->zcw_done) {
2312		/*
2313		 * It's possible that, while we were waiting to acquire
2314		 * the "zl_issuer_lock", another thread committed this
2315		 * waiter to an lwb. If that occurs, we bail out early,
2316		 * without processing any of the zilog's queue of itxs.
2317		 *
2318		 * On certain workloads and system configurations, the
2319		 * "zl_issuer_lock" can become highly contended. In an
2320		 * attempt to reduce this contention, we immediately drop
2321		 * the lock if the waiter has already been processed.
2322		 *
2323		 * We've measured this optimization to reduce CPU spent
2324		 * contending on this lock by up to 5%, using a system
2325		 * with 32 CPUs, low latency storage (~50 usec writes),
2326		 * and 1024 threads performing sync writes.
2327		 */
2328		goto out;
2329	}
2330
2331	zil_get_commit_list(zilog);
2332	zil_prune_commit_list(zilog);
2333	zil_process_commit_list(zilog);
2334
2335out:
2336	mutex_exit(&zilog->zl_issuer_lock);
2337}
2338
2339static void
2340zil_commit_waiter_timeout(zilog_t *zilog, zil_commit_waiter_t *zcw)
2341{
2342	ASSERT(!MUTEX_HELD(&zilog->zl_issuer_lock));
2343	ASSERT(MUTEX_HELD(&zcw->zcw_lock));
2344	ASSERT3B(zcw->zcw_done, ==, B_FALSE);
2345
2346	lwb_t *lwb = zcw->zcw_lwb;
2347	ASSERT3P(lwb, !=, NULL);
2348	ASSERT3S(lwb->lwb_state, !=, LWB_STATE_CLOSED);
2349
2350	/*
2351	 * If the lwb has already been issued by another thread, we can
2352	 * immediately return since there's no work to be done (the
2353	 * point of this function is to issue the lwb). Additionally, we
2354	 * do this prior to acquiring the zl_issuer_lock, to avoid
2355	 * acquiring it when it's not necessary to do so.
2356	 */
2357	if (lwb->lwb_state == LWB_STATE_ISSUED ||
2358	    lwb->lwb_state == LWB_STATE_WRITE_DONE ||
2359	    lwb->lwb_state == LWB_STATE_FLUSH_DONE)
2360		return;
2361
2362	/*
2363	 * In order to call zil_lwb_write_issue() we must hold the
2364	 * zilog's "zl_issuer_lock". We can't simply acquire that lock,
2365	 * since we're already holding the commit waiter's "zcw_lock",
2366	 * and those two locks are aquired in the opposite order
2367	 * elsewhere.
2368	 */
2369	mutex_exit(&zcw->zcw_lock);
2370	mutex_enter(&zilog->zl_issuer_lock);
2371	mutex_enter(&zcw->zcw_lock);
2372
2373	/*
2374	 * Since we just dropped and re-acquired the commit waiter's
2375	 * lock, we have to re-check to see if the waiter was marked
2376	 * "done" during that process. If the waiter was marked "done",
2377	 * the "lwb" pointer is no longer valid (it can be free'd after
2378	 * the waiter is marked "done"), so without this check we could
2379	 * wind up with a use-after-free error below.
2380	 */
2381	if (zcw->zcw_done)
2382		goto out;
2383
2384	ASSERT3P(lwb, ==, zcw->zcw_lwb);
2385
2386	/*
2387	 * We've already checked this above, but since we hadn't acquired
2388	 * the zilog's zl_issuer_lock, we have to perform this check a
2389	 * second time while holding the lock.
2390	 *
2391	 * We don't need to hold the zl_lock since the lwb cannot transition
2392	 * from OPENED to ISSUED while we hold the zl_issuer_lock. The lwb
2393	 * _can_ transition from ISSUED to DONE, but it's OK to race with
2394	 * that transition since we treat the lwb the same, whether it's in
2395	 * the ISSUED or DONE states.
2396	 *
2397	 * The important thing, is we treat the lwb differently depending on
2398	 * if it's ISSUED or OPENED, and block any other threads that might
2399	 * attempt to issue this lwb. For that reason we hold the
2400	 * zl_issuer_lock when checking the lwb_state; we must not call
2401	 * zil_lwb_write_issue() if the lwb had already been issued.
2402	 *
2403	 * See the comment above the lwb_state_t structure definition for
2404	 * more details on the lwb states, and locking requirements.
2405	 */
2406	if (lwb->lwb_state == LWB_STATE_ISSUED ||
2407	    lwb->lwb_state == LWB_STATE_WRITE_DONE ||
2408	    lwb->lwb_state == LWB_STATE_FLUSH_DONE)
2409		goto out;
2410
2411	ASSERT3S(lwb->lwb_state, ==, LWB_STATE_OPENED);
2412
2413	/*
2414	 * As described in the comments above zil_commit_waiter() and
2415	 * zil_process_commit_list(), we need to issue this lwb's zio
2416	 * since we've reached the commit waiter's timeout and it still
2417	 * hasn't been issued.
2418	 */
2419	lwb_t *nlwb = zil_lwb_write_issue(zilog, lwb);
2420
2421	IMPLY(nlwb != NULL, lwb->lwb_state != LWB_STATE_OPENED);
2422
2423	/*
2424	 * Since the lwb's zio hadn't been issued by the time this thread
2425	 * reached its timeout, we reset the zilog's "zl_cur_used" field
2426	 * to influence the zil block size selection algorithm.
2427	 *
2428	 * By having to issue the lwb's zio here, it means the size of the
2429	 * lwb was too large, given the incoming throughput of itxs.  By
2430	 * setting "zl_cur_used" to zero, we communicate this fact to the
2431	 * block size selection algorithm, so it can take this informaiton
2432	 * into account, and potentially select a smaller size for the
2433	 * next lwb block that is allocated.
2434	 */
2435	zilog->zl_cur_used = 0;
2436
2437	if (nlwb == NULL) {
2438		/*
2439		 * When zil_lwb_write_issue() returns NULL, this
2440		 * indicates zio_alloc_zil() failed to allocate the
2441		 * "next" lwb on-disk. When this occurs, the ZIL write
2442		 * pipeline must be stalled; see the comment within the
2443		 * zil_commit_writer_stall() function for more details.
2444		 *
2445		 * We must drop the commit waiter's lock prior to
2446		 * calling zil_commit_writer_stall() or else we can wind
2447		 * up with the following deadlock:
2448		 *
2449		 * - This thread is waiting for the txg to sync while
2450		 *   holding the waiter's lock; txg_wait_synced() is
2451		 *   used within txg_commit_writer_stall().
2452		 *
2453		 * - The txg can't sync because it is waiting for this
2454		 *   lwb's zio callback to call dmu_tx_commit().
2455		 *
2456		 * - The lwb's zio callback can't call dmu_tx_commit()
2457		 *   because it's blocked trying to acquire the waiter's
2458		 *   lock, which occurs prior to calling dmu_tx_commit()
2459		 */
2460		mutex_exit(&zcw->zcw_lock);
2461		zil_commit_writer_stall(zilog);
2462		mutex_enter(&zcw->zcw_lock);
2463	}
2464
2465out:
2466	mutex_exit(&zilog->zl_issuer_lock);
2467	ASSERT(MUTEX_HELD(&zcw->zcw_lock));
2468}
2469
2470/*
2471 * This function is responsible for performing the following two tasks:
2472 *
2473 * 1. its primary responsibility is to block until the given "commit
2474 *    waiter" is considered "done".
2475 *
2476 * 2. its secondary responsibility is to issue the zio for the lwb that
2477 *    the given "commit waiter" is waiting on, if this function has
2478 *    waited "long enough" and the lwb is still in the "open" state.
2479 *
2480 * Given a sufficient amount of itxs being generated and written using
2481 * the ZIL, the lwb's zio will be issued via the zil_lwb_commit()
2482 * function. If this does not occur, this secondary responsibility will
2483 * ensure the lwb is issued even if there is not other synchronous
2484 * activity on the system.
2485 *
2486 * For more details, see zil_process_commit_list(); more specifically,
2487 * the comment at the bottom of that function.
2488 */
2489static void
2490zil_commit_waiter(zilog_t *zilog, zil_commit_waiter_t *zcw)
2491{
2492	ASSERT(!MUTEX_HELD(&zilog->zl_lock));
2493	ASSERT(!MUTEX_HELD(&zilog->zl_issuer_lock));
2494	ASSERT(spa_writeable(zilog->zl_spa));
2495
2496	mutex_enter(&zcw->zcw_lock);
2497
2498	/*
2499	 * The timeout is scaled based on the lwb latency to avoid
2500	 * significantly impacting the latency of each individual itx.
2501	 * For more details, see the comment at the bottom of the
2502	 * zil_process_commit_list() function.
2503	 */
2504	int pct = MAX(zfs_commit_timeout_pct, 1);
2505	hrtime_t sleep = (zilog->zl_last_lwb_latency * pct) / 100;
2506	hrtime_t wakeup = gethrtime() + sleep;
2507	boolean_t timedout = B_FALSE;
2508
2509	while (!zcw->zcw_done) {
2510		ASSERT(MUTEX_HELD(&zcw->zcw_lock));
2511
2512		lwb_t *lwb = zcw->zcw_lwb;
2513
2514		/*
2515		 * Usually, the waiter will have a non-NULL lwb field here,
2516		 * but it's possible for it to be NULL as a result of
2517		 * zil_commit() racing with spa_sync().
2518		 *
2519		 * When zil_clean() is called, it's possible for the itxg
2520		 * list (which may be cleaned via a taskq) to contain
2521		 * commit itxs. When this occurs, the commit waiters linked
2522		 * off of these commit itxs will not be committed to an
2523		 * lwb.  Additionally, these commit waiters will not be
2524		 * marked done until zil_commit_waiter_skip() is called via
2525		 * zil_itxg_clean().
2526		 *
2527		 * Thus, it's possible for this commit waiter (i.e. the
2528		 * "zcw" variable) to be found in this "in between" state;
2529		 * where it's "zcw_lwb" field is NULL, and it hasn't yet
2530		 * been skipped, so it's "zcw_done" field is still B_FALSE.
2531		 */
2532		IMPLY(lwb != NULL, lwb->lwb_state != LWB_STATE_CLOSED);
2533
2534		if (lwb != NULL && lwb->lwb_state == LWB_STATE_OPENED) {
2535			ASSERT3B(timedout, ==, B_FALSE);
2536
2537			/*
2538			 * If the lwb hasn't been issued yet, then we
2539			 * need to wait with a timeout, in case this
2540			 * function needs to issue the lwb after the
2541			 * timeout is reached; responsibility (2) from
2542			 * the comment above this function.
2543			 */
2544			clock_t timeleft = cv_timedwait_hires(&zcw->zcw_cv,
2545			    &zcw->zcw_lock, wakeup, USEC2NSEC(1),
2546			    CALLOUT_FLAG_ABSOLUTE);
2547
2548			if (timeleft >= 0 || zcw->zcw_done)
2549				continue;
2550
2551			timedout = B_TRUE;
2552			zil_commit_waiter_timeout(zilog, zcw);
2553
2554			if (!zcw->zcw_done) {
2555				/*
2556				 * If the commit waiter has already been
2557				 * marked "done", it's possible for the
2558				 * waiter's lwb structure to have already
2559				 * been freed.  Thus, we can only reliably
2560				 * make these assertions if the waiter
2561				 * isn't done.
2562				 */
2563				ASSERT3P(lwb, ==, zcw->zcw_lwb);
2564				ASSERT3S(lwb->lwb_state, !=, LWB_STATE_OPENED);
2565			}
2566		} else {
2567			/*
2568			 * If the lwb isn't open, then it must have already
2569			 * been issued. In that case, there's no need to
2570			 * use a timeout when waiting for the lwb to
2571			 * complete.
2572			 *
2573			 * Additionally, if the lwb is NULL, the waiter
2574			 * will soon be signalled and marked done via
2575			 * zil_clean() and zil_itxg_clean(), so no timeout
2576			 * is required.
2577			 */
2578
2579			IMPLY(lwb != NULL,
2580			    lwb->lwb_state == LWB_STATE_ISSUED ||
2581			    lwb->lwb_state == LWB_STATE_WRITE_DONE ||
2582			    lwb->lwb_state == LWB_STATE_FLUSH_DONE);
2583			cv_wait(&zcw->zcw_cv, &zcw->zcw_lock);
2584		}
2585	}
2586
2587	mutex_exit(&zcw->zcw_lock);
2588}
2589
2590static zil_commit_waiter_t *
2591zil_alloc_commit_waiter()
2592{
2593	zil_commit_waiter_t *zcw = kmem_cache_alloc(zil_zcw_cache, KM_SLEEP);
2594
2595	cv_init(&zcw->zcw_cv, NULL, CV_DEFAULT, NULL);
2596	mutex_init(&zcw->zcw_lock, NULL, MUTEX_DEFAULT, NULL);
2597	list_link_init(&zcw->zcw_node);
2598	zcw->zcw_lwb = NULL;
2599	zcw->zcw_done = B_FALSE;
2600	zcw->zcw_zio_error = 0;
2601
2602	return (zcw);
2603}
2604
2605static void
2606zil_free_commit_waiter(zil_commit_waiter_t *zcw)
2607{
2608	ASSERT(!list_link_active(&zcw->zcw_node));
2609	ASSERT3P(zcw->zcw_lwb, ==, NULL);
2610	ASSERT3B(zcw->zcw_done, ==, B_TRUE);
2611	mutex_destroy(&zcw->zcw_lock);
2612	cv_destroy(&zcw->zcw_cv);
2613	kmem_cache_free(zil_zcw_cache, zcw);
2614}
2615
2616/*
2617 * This function is used to create a TX_COMMIT itx and assign it. This
2618 * way, it will be linked into the ZIL's list of synchronous itxs, and
2619 * then later committed to an lwb (or skipped) when
2620 * zil_process_commit_list() is called.
2621 */
2622static void
2623zil_commit_itx_assign(zilog_t *zilog, zil_commit_waiter_t *zcw)
2624{
2625	dmu_tx_t *tx = dmu_tx_create(zilog->zl_os);
2626	VERIFY0(dmu_tx_assign(tx, TXG_WAIT));
2627
2628	itx_t *itx = zil_itx_create(TX_COMMIT, sizeof (lr_t));
2629	itx->itx_sync = B_TRUE;
2630	itx->itx_private = zcw;
2631
2632	zil_itx_assign(zilog, itx, tx);
2633
2634	dmu_tx_commit(tx);
2635}
2636
2637/*
2638 * Commit ZFS Intent Log transactions (itxs) to stable storage.
2639 *
2640 * When writing ZIL transactions to the on-disk representation of the
2641 * ZIL, the itxs are committed to a Log Write Block (lwb). Multiple
2642 * itxs can be committed to a single lwb. Once a lwb is written and
2643 * committed to stable storage (i.e. the lwb is written, and vdevs have
2644 * been flushed), each itx that was committed to that lwb is also
2645 * considered to be committed to stable storage.
2646 *
2647 * When an itx is committed to an lwb, the log record (lr_t) contained
2648 * by the itx is copied into the lwb's zio buffer, and once this buffer
2649 * is written to disk, it becomes an on-disk ZIL block.
2650 *
2651 * As itxs are generated, they're inserted into the ZIL's queue of
2652 * uncommitted itxs. The semantics of zil_commit() are such that it will
2653 * block until all itxs that were in the queue when it was called, are
2654 * committed to stable storage.
2655 *
2656 * If "foid" is zero, this means all "synchronous" and "asynchronous"
2657 * itxs, for all objects in the dataset, will be committed to stable
2658 * storage prior to zil_commit() returning. If "foid" is non-zero, all
2659 * "synchronous" itxs for all objects, but only "asynchronous" itxs
2660 * that correspond to the foid passed in, will be committed to stable
2661 * storage prior to zil_commit() returning.
2662 *
2663 * Generally speaking, when zil_commit() is called, the consumer doesn't
2664 * actually care about _all_ of the uncommitted itxs. Instead, they're
2665 * simply trying to waiting for a specific itx to be committed to disk,
2666 * but the interface(s) for interacting with the ZIL don't allow such
2667 * fine-grained communication. A better interface would allow a consumer
2668 * to create and assign an itx, and then pass a reference to this itx to
2669 * zil_commit(); such that zil_commit() would return as soon as that
2670 * specific itx was committed to disk (instead of waiting for _all_
2671 * itxs to be committed).
2672 *
2673 * When a thread calls zil_commit() a special "commit itx" will be
2674 * generated, along with a corresponding "waiter" for this commit itx.
2675 * zil_commit() will wait on this waiter's CV, such that when the waiter
2676 * is marked done, and signalled, zil_commit() will return.
2677 *
2678 * This commit itx is inserted into the queue of uncommitted itxs. This
2679 * provides an easy mechanism for determining which itxs were in the
2680 * queue prior to zil_commit() having been called, and which itxs were
2681 * added after zil_commit() was called.
2682 *
2683 * The commit it is special; it doesn't have any on-disk representation.
2684 * When a commit itx is "committed" to an lwb, the waiter associated
2685 * with it is linked onto the lwb's list of waiters. Then, when that lwb
2686 * completes, each waiter on the lwb's list is marked done and signalled
2687 * -- allowing the thread waiting on the waiter to return from zil_commit().
2688 *
2689 * It's important to point out a few critical factors that allow us
2690 * to make use of the commit itxs, commit waiters, per-lwb lists of
2691 * commit waiters, and zio completion callbacks like we're doing:
2692 *
2693 *   1. The list of waiters for each lwb is traversed, and each commit
2694 *      waiter is marked "done" and signalled, in the zio completion
2695 *      callback of the lwb's zio[*].
2696 *
2697 *      * Actually, the waiters are signalled in the zio completion
2698 *        callback of the root zio for the DKIOCFLUSHWRITECACHE commands
2699 *        that are sent to the vdevs upon completion of the lwb zio.
2700 *
2701 *   2. When the itxs are inserted into the ZIL's queue of uncommitted
2702 *      itxs, the order in which they are inserted is preserved[*]; as
2703 *      itxs are added to the queue, they are added to the tail of
2704 *      in-memory linked lists.
2705 *
2706 *      When committing the itxs to lwbs (to be written to disk), they
2707 *      are committed in the same order in which the itxs were added to
2708 *      the uncommitted queue's linked list(s); i.e. the linked list of
2709 *      itxs to commit is traversed from head to tail, and each itx is
2710 *      committed to an lwb in that order.
2711 *
2712 *      * To clarify:
2713 *
2714 *        - the order of "sync" itxs is preserved w.r.t. other
2715 *          "sync" itxs, regardless of the corresponding objects.
2716 *        - the order of "async" itxs is preserved w.r.t. other
2717 *          "async" itxs corresponding to the same object.
2718 *        - the order of "async" itxs is *not* preserved w.r.t. other
2719 *          "async" itxs corresponding to different objects.
2720 *        - the order of "sync" itxs w.r.t. "async" itxs (or vice
2721 *          versa) is *not* preserved, even for itxs that correspond
2722 *          to the same object.
2723 *
2724 *      For more details, see: zil_itx_assign(), zil_async_to_sync(),
2725 *      zil_get_commit_list(), and zil_process_commit_list().
2726 *
2727 *   3. The lwbs represent a linked list of blocks on disk. Thus, any
2728 *      lwb cannot be considered committed to stable storage, until its
2729 *      "previous" lwb is also committed to stable storage. This fact,
2730 *      coupled with the fact described above, means that itxs are
2731 *      committed in (roughly) the order in which they were generated.
2732 *      This is essential because itxs are dependent on prior itxs.
2733 *      Thus, we *must not* deem an itx as being committed to stable
2734 *      storage, until *all* prior itxs have also been committed to
2735 *      stable storage.
2736 *
2737 *      To enforce this ordering of lwb zio's, while still leveraging as
2738 *      much of the underlying storage performance as possible, we rely
2739 *      on two fundamental concepts:
2740 *
2741 *          1. The creation and issuance of lwb zio's is protected by
2742 *             the zilog's "zl_issuer_lock", which ensures only a single
2743 *             thread is creating and/or issuing lwb's at a time
2744 *          2. The "previous" lwb is a child of the "current" lwb
2745 *             (leveraging the zio parent-child depenency graph)
2746 *
2747 *      By relying on this parent-child zio relationship, we can have
2748 *      many lwb zio's concurrently issued to the underlying storage,
2749 *      but the order in which they complete will be the same order in
2750 *      which they were created.
2751 */
2752void
2753zil_commit(zilog_t *zilog, uint64_t foid)
2754{
2755	/*
2756	 * We should never attempt to call zil_commit on a snapshot for
2757	 * a couple of reasons:
2758	 *
2759	 * 1. A snapshot may never be modified, thus it cannot have any
2760	 *    in-flight itxs that would have modified the dataset.
2761	 *
2762	 * 2. By design, when zil_commit() is called, a commit itx will
2763	 *    be assigned to this zilog; as a result, the zilog will be
2764	 *    dirtied. We must not dirty the zilog of a snapshot; there's
2765	 *    checks in the code that enforce this invariant, and will
2766	 *    cause a panic if it's not upheld.
2767	 */
2768	ASSERT3B(dmu_objset_is_snapshot(zilog->zl_os), ==, B_FALSE);
2769
2770	if (zilog->zl_sync == ZFS_SYNC_DISABLED)
2771		return;
2772
2773	if (!spa_writeable(zilog->zl_spa)) {
2774		/*
2775		 * If the SPA is not writable, there should never be any
2776		 * pending itxs waiting to be committed to disk. If that
2777		 * weren't true, we'd skip writing those itxs out, and
2778		 * would break the sematics of zil_commit(); thus, we're
2779		 * verifying that truth before we return to the caller.
2780		 */
2781		ASSERT(list_is_empty(&zilog->zl_lwb_list));
2782		ASSERT3P(zilog->zl_last_lwb_opened, ==, NULL);
2783		for (int i = 0; i < TXG_SIZE; i++)
2784			ASSERT3P(zilog->zl_itxg[i].itxg_itxs, ==, NULL);
2785		return;
2786	}
2787
2788	/*
2789	 * If the ZIL is suspended, we don't want to dirty it by calling
2790	 * zil_commit_itx_assign() below, nor can we write out
2791	 * lwbs like would be done in zil_commit_write(). Thus, we
2792	 * simply rely on txg_wait_synced() to maintain the necessary
2793	 * semantics, and avoid calling those functions altogether.
2794	 */
2795	if (zilog->zl_suspend > 0) {
2796		txg_wait_synced(zilog->zl_dmu_pool, 0);
2797		return;
2798	}
2799
2800	zil_commit_impl(zilog, foid);
2801}
2802
2803void
2804zil_commit_impl(zilog_t *zilog, uint64_t foid)
2805{
2806	/*
2807	 * Move the "async" itxs for the specified foid to the "sync"
2808	 * queues, such that they will be later committed (or skipped)
2809	 * to an lwb when zil_process_commit_list() is called.
2810	 *
2811	 * Since these "async" itxs must be committed prior to this
2812	 * call to zil_commit returning, we must perform this operation
2813	 * before we call zil_commit_itx_assign().
2814	 */
2815	zil_async_to_sync(zilog, foid);
2816
2817	/*
2818	 * We allocate a new "waiter" structure which will initially be
2819	 * linked to the commit itx using the itx's "itx_private" field.
2820	 * Since the commit itx doesn't represent any on-disk state,
2821	 * when it's committed to an lwb, rather than copying the its
2822	 * lr_t into the lwb's buffer, the commit itx's "waiter" will be
2823	 * added to the lwb's list of waiters. Then, when the lwb is
2824	 * committed to stable storage, each waiter in the lwb's list of
2825	 * waiters will be marked "done", and signalled.
2826	 *
2827	 * We must create the waiter and assign the commit itx prior to
2828	 * calling zil_commit_writer(), or else our specific commit itx
2829	 * is not guaranteed to be committed to an lwb prior to calling
2830	 * zil_commit_waiter().
2831	 */
2832	zil_commit_waiter_t *zcw = zil_alloc_commit_waiter();
2833	zil_commit_itx_assign(zilog, zcw);
2834
2835	zil_commit_writer(zilog, zcw);
2836	zil_commit_waiter(zilog, zcw);
2837
2838	if (zcw->zcw_zio_error != 0) {
2839		/*
2840		 * If there was an error writing out the ZIL blocks that
2841		 * this thread is waiting on, then we fallback to
2842		 * relying on spa_sync() to write out the data this
2843		 * thread is waiting on. Obviously this has performance
2844		 * implications, but the expectation is for this to be
2845		 * an exceptional case, and shouldn't occur often.
2846		 */
2847		DTRACE_PROBE2(zil__commit__io__error,
2848		    zilog_t *, zilog, zil_commit_waiter_t *, zcw);
2849		txg_wait_synced(zilog->zl_dmu_pool, 0);
2850	}
2851
2852	zil_free_commit_waiter(zcw);
2853}
2854
2855/*
2856 * Called in syncing context to free committed log blocks and update log header.
2857 */
2858void
2859zil_sync(zilog_t *zilog, dmu_tx_t *tx)
2860{
2861	zil_header_t *zh = zil_header_in_syncing_context(zilog);
2862	uint64_t txg = dmu_tx_get_txg(tx);
2863	spa_t *spa = zilog->zl_spa;
2864	uint64_t *replayed_seq = &zilog->zl_replayed_seq[txg & TXG_MASK];
2865	lwb_t *lwb;
2866
2867	/*
2868	 * We don't zero out zl_destroy_txg, so make sure we don't try
2869	 * to destroy it twice.
2870	 */
2871	if (spa_sync_pass(spa) != 1)
2872		return;
2873
2874	mutex_enter(&zilog->zl_lock);
2875
2876	ASSERT(zilog->zl_stop_sync == 0);
2877
2878	if (*replayed_seq != 0) {
2879		ASSERT(zh->zh_replay_seq < *replayed_seq);
2880		zh->zh_replay_seq = *replayed_seq;
2881		*replayed_seq = 0;
2882	}
2883
2884	if (zilog->zl_destroy_txg == txg) {
2885		blkptr_t blk = zh->zh_log;
2886
2887		ASSERT(list_head(&zilog->zl_lwb_list) == NULL);
2888
2889		bzero(zh, sizeof (zil_header_t));
2890		bzero(zilog->zl_replayed_seq, sizeof (zilog->zl_replayed_seq));
2891
2892		if (zilog->zl_keep_first) {
2893			/*
2894			 * If this block was part of log chain that couldn't
2895			 * be claimed because a device was missing during
2896			 * zil_claim(), but that device later returns,
2897			 * then this block could erroneously appear valid.
2898			 * To guard against this, assign a new GUID to the new
2899			 * log chain so it doesn't matter what blk points to.
2900			 */
2901			zil_init_log_chain(zilog, &blk);
2902			zh->zh_log = blk;
2903		}
2904	}
2905
2906	while ((lwb = list_head(&zilog->zl_lwb_list)) != NULL) {
2907		zh->zh_log = lwb->lwb_blk;
2908		if (lwb->lwb_buf != NULL || lwb->lwb_max_txg > txg)
2909			break;
2910		list_remove(&zilog->zl_lwb_list, lwb);
2911		zio_free(spa, txg, &lwb->lwb_blk);
2912		zil_free_lwb(zilog, lwb);
2913
2914		/*
2915		 * If we don't have anything left in the lwb list then
2916		 * we've had an allocation failure and we need to zero
2917		 * out the zil_header blkptr so that we don't end
2918		 * up freeing the same block twice.
2919		 */
2920		if (list_head(&zilog->zl_lwb_list) == NULL)
2921			BP_ZERO(&zh->zh_log);
2922	}
2923	mutex_exit(&zilog->zl_lock);
2924}
2925
2926/* ARGSUSED */
2927static int
2928zil_lwb_cons(void *vbuf, void *unused, int kmflag)
2929{
2930	lwb_t *lwb = vbuf;
2931	list_create(&lwb->lwb_waiters, sizeof (zil_commit_waiter_t),
2932	    offsetof(zil_commit_waiter_t, zcw_node));
2933	avl_create(&lwb->lwb_vdev_tree, zil_lwb_vdev_compare,
2934	    sizeof (zil_vdev_node_t), offsetof(zil_vdev_node_t, zv_node));
2935	mutex_init(&lwb->lwb_vdev_lock, NULL, MUTEX_DEFAULT, NULL);
2936	return (0);
2937}
2938
2939/* ARGSUSED */
2940static void
2941zil_lwb_dest(void *vbuf, void *unused)
2942{
2943	lwb_t *lwb = vbuf;
2944	mutex_destroy(&lwb->lwb_vdev_lock);
2945	avl_destroy(&lwb->lwb_vdev_tree);
2946	list_destroy(&lwb->lwb_waiters);
2947}
2948
2949void
2950zil_init(void)
2951{
2952	zil_lwb_cache = kmem_cache_create("zil_lwb_cache",
2953	    sizeof (lwb_t), 0, zil_lwb_cons, zil_lwb_dest, NULL, NULL, NULL, 0);
2954
2955	zil_zcw_cache = kmem_cache_create("zil_zcw_cache",
2956	    sizeof (zil_commit_waiter_t), 0, NULL, NULL, NULL, NULL, NULL, 0);
2957}
2958
2959void
2960zil_fini(void)
2961{
2962	kmem_cache_destroy(zil_zcw_cache);
2963	kmem_cache_destroy(zil_lwb_cache);
2964}
2965
2966void
2967zil_set_sync(zilog_t *zilog, uint64_t sync)
2968{
2969	zilog->zl_sync = sync;
2970}
2971
2972void
2973zil_set_logbias(zilog_t *zilog, uint64_t logbias)
2974{
2975	zilog->zl_logbias = logbias;
2976}
2977
2978zilog_t *
2979zil_alloc(objset_t *os, zil_header_t *zh_phys)
2980{
2981	zilog_t *zilog;
2982
2983	zilog = kmem_zalloc(sizeof (zilog_t), KM_SLEEP);
2984
2985	zilog->zl_header = zh_phys;
2986	zilog->zl_os = os;
2987	zilog->zl_spa = dmu_objset_spa(os);
2988	zilog->zl_dmu_pool = dmu_objset_pool(os);
2989	zilog->zl_destroy_txg = TXG_INITIAL - 1;
2990	zilog->zl_logbias = dmu_objset_logbias(os);
2991	zilog->zl_sync = dmu_objset_syncprop(os);
2992	zilog->zl_dirty_max_txg = 0;
2993	zilog->zl_last_lwb_opened = NULL;
2994	zilog->zl_last_lwb_latency = 0;
2995
2996	mutex_init(&zilog->zl_lock, NULL, MUTEX_DEFAULT, NULL);
2997	mutex_init(&zilog->zl_issuer_lock, NULL, MUTEX_DEFAULT, NULL);
2998
2999	for (int i = 0; i < TXG_SIZE; i++) {
3000		mutex_init(&zilog->zl_itxg[i].itxg_lock, NULL,
3001		    MUTEX_DEFAULT, NULL);
3002	}
3003
3004	list_create(&zilog->zl_lwb_list, sizeof (lwb_t),
3005	    offsetof(lwb_t, lwb_node));
3006
3007	list_create(&zilog->zl_itx_commit_list, sizeof (itx_t),
3008	    offsetof(itx_t, itx_node));
3009
3010	cv_init(&zilog->zl_cv_suspend, NULL, CV_DEFAULT, NULL);
3011
3012	return (zilog);
3013}
3014
3015void
3016zil_free(zilog_t *zilog)
3017{
3018	zilog->zl_stop_sync = 1;
3019
3020	ASSERT0(zilog->zl_suspend);
3021	ASSERT0(zilog->zl_suspending);
3022
3023	ASSERT(list_is_empty(&zilog->zl_lwb_list));
3024	list_destroy(&zilog->zl_lwb_list);
3025
3026	ASSERT(list_is_empty(&zilog->zl_itx_commit_list));
3027	list_destroy(&zilog->zl_itx_commit_list);
3028
3029	for (int i = 0; i < TXG_SIZE; i++) {
3030		/*
3031		 * It's possible for an itx to be generated that doesn't dirty
3032		 * a txg (e.g. ztest TX_TRUNCATE). So there's no zil_clean()
3033		 * callback to remove the entry. We remove those here.
3034		 *
3035		 * Also free up the ziltest itxs.
3036		 */
3037		if (zilog->zl_itxg[i].itxg_itxs)
3038			zil_itxg_clean(zilog->zl_itxg[i].itxg_itxs);
3039		mutex_destroy(&zilog->zl_itxg[i].itxg_lock);
3040	}
3041
3042	mutex_destroy(&zilog->zl_issuer_lock);
3043	mutex_destroy(&zilog->zl_lock);
3044
3045	cv_destroy(&zilog->zl_cv_suspend);
3046
3047	kmem_free(zilog, sizeof (zilog_t));
3048}
3049
3050/*
3051 * Open an intent log.
3052 */
3053zilog_t *
3054zil_open(objset_t *os, zil_get_data_t *get_data)
3055{
3056	zilog_t *zilog = dmu_objset_zil(os);
3057
3058	ASSERT3P(zilog->zl_get_data, ==, NULL);
3059	ASSERT3P(zilog->zl_last_lwb_opened, ==, NULL);
3060	ASSERT(list_is_empty(&zilog->zl_lwb_list));
3061
3062	zilog->zl_get_data = get_data;
3063
3064	return (zilog);
3065}
3066
3067/*
3068 * Close an intent log.
3069 */
3070void
3071zil_close(zilog_t *zilog)
3072{
3073	lwb_t *lwb;
3074	uint64_t txg;
3075
3076	if (!dmu_objset_is_snapshot(zilog->zl_os)) {
3077		zil_commit(zilog, 0);
3078	} else {
3079		ASSERT3P(list_tail(&zilog->zl_lwb_list), ==, NULL);
3080		ASSERT0(zilog->zl_dirty_max_txg);
3081		ASSERT3B(zilog_is_dirty(zilog), ==, B_FALSE);
3082	}
3083
3084	mutex_enter(&zilog->zl_lock);
3085	lwb = list_tail(&zilog->zl_lwb_list);
3086	if (lwb == NULL)
3087		txg = zilog->zl_dirty_max_txg;
3088	else
3089		txg = MAX(zilog->zl_dirty_max_txg, lwb->lwb_max_txg);
3090	mutex_exit(&zilog->zl_lock);
3091
3092	/*
3093	 * We need to use txg_wait_synced() to wait long enough for the
3094	 * ZIL to be clean, and to wait for all pending lwbs to be
3095	 * written out.
3096	 */
3097	if (txg != 0)
3098		txg_wait_synced(zilog->zl_dmu_pool, txg);
3099
3100	if (zilog_is_dirty(zilog))
3101		zfs_dbgmsg("zil (%p) is dirty, txg %llu", zilog, txg);
3102	if (txg < spa_freeze_txg(zilog->zl_spa))
3103		VERIFY(!zilog_is_dirty(zilog));
3104
3105	zilog->zl_get_data = NULL;
3106
3107	/*
3108	 * We should have only one lwb left on the list; remove it now.
3109	 */
3110	mutex_enter(&zilog->zl_lock);
3111	lwb = list_head(&zilog->zl_lwb_list);
3112	if (lwb != NULL) {
3113		ASSERT3P(lwb, ==, list_tail(&zilog->zl_lwb_list));
3114		ASSERT3S(lwb->lwb_state, !=, LWB_STATE_ISSUED);
3115		list_remove(&zilog->zl_lwb_list, lwb);
3116		zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
3117		zil_free_lwb(zilog, lwb);
3118	}
3119	mutex_exit(&zilog->zl_lock);
3120}
3121
3122static char *suspend_tag = "zil suspending";
3123
3124/*
3125 * Suspend an intent log.  While in suspended mode, we still honor
3126 * synchronous semantics, but we rely on txg_wait_synced() to do it.
3127 * On old version pools, we suspend the log briefly when taking a
3128 * snapshot so that it will have an empty intent log.
3129 *
3130 * Long holds are not really intended to be used the way we do here --
3131 * held for such a short time.  A concurrent caller of dsl_dataset_long_held()
3132 * could fail.  Therefore we take pains to only put a long hold if it is
3133 * actually necessary.  Fortunately, it will only be necessary if the
3134 * objset is currently mounted (or the ZVOL equivalent).  In that case it
3135 * will already have a long hold, so we are not really making things any worse.
3136 *
3137 * Ideally, we would locate the existing long-holder (i.e. the zfsvfs_t or
3138 * zvol_state_t), and use their mechanism to prevent their hold from being
3139 * dropped (e.g. VFS_HOLD()).  However, that would be even more pain for
3140 * very little gain.
3141 *
3142 * if cookiep == NULL, this does both the suspend & resume.
3143 * Otherwise, it returns with the dataset "long held", and the cookie
3144 * should be passed into zil_resume().
3145 */
3146int
3147zil_suspend(const char *osname, void **cookiep)
3148{
3149	objset_t *os;
3150	zilog_t *zilog;
3151	const zil_header_t *zh;
3152	int error;
3153
3154	error = dmu_objset_hold(osname, suspend_tag, &os);
3155	if (error != 0)
3156		return (error);
3157	zilog = dmu_objset_zil(os);
3158
3159	mutex_enter(&zilog->zl_lock);
3160	zh = zilog->zl_header;
3161
3162	if (zh->zh_flags & ZIL_REPLAY_NEEDED) {		/* unplayed log */
3163		mutex_exit(&zilog->zl_lock);
3164		dmu_objset_rele(os, suspend_tag);
3165		return (SET_ERROR(EBUSY));
3166	}
3167
3168	/*
3169	 * Don't put a long hold in the cases where we can avoid it.  This
3170	 * is when there is no cookie so we are doing a suspend & resume
3171	 * (i.e. called from zil_vdev_offline()), and there's nothing to do
3172	 * for the suspend because it's already suspended, or there's no ZIL.
3173	 */
3174	if (cookiep == NULL && !zilog->zl_suspending &&
3175	    (zilog->zl_suspend > 0 || BP_IS_HOLE(&zh->zh_log))) {
3176		mutex_exit(&zilog->zl_lock);
3177		dmu_objset_rele(os, suspend_tag);
3178		return (0);
3179	}
3180
3181	dsl_dataset_long_hold(dmu_objset_ds(os), suspend_tag);
3182	dsl_pool_rele(dmu_objset_pool(os), suspend_tag);
3183
3184	zilog->zl_suspend++;
3185
3186	if (zilog->zl_suspend > 1) {
3187		/*
3188		 * Someone else is already suspending it.
3189		 * Just wait for them to finish.
3190		 */
3191
3192		while (zilog->zl_suspending)
3193			cv_wait(&zilog->zl_cv_suspend, &zilog->zl_lock);
3194		mutex_exit(&zilog->zl_lock);
3195
3196		if (cookiep == NULL)
3197			zil_resume(os);
3198		else
3199			*cookiep = os;
3200		return (0);
3201	}
3202
3203	/*
3204	 * If there is no pointer to an on-disk block, this ZIL must not
3205	 * be active (e.g. filesystem not mounted), so there's nothing
3206	 * to clean up.
3207	 */
3208	if (BP_IS_HOLE(&zh->zh_log)) {
3209		ASSERT(cookiep != NULL); /* fast path already handled */
3210
3211		*cookiep = os;
3212		mutex_exit(&zilog->zl_lock);
3213		return (0);
3214	}
3215
3216	/*
3217	 * The ZIL has work to do. Ensure that the associated encryption
3218	 * key will remain mapped while we are committing the log by
3219	 * grabbing a reference to it. If the key isn't loaded we have no
3220	 * choice but to return an error until the wrapping key is loaded.
3221	 */
3222	if (os->os_encrypted &&
3223	    dsl_dataset_create_key_mapping(dmu_objset_ds(os)) != 0) {
3224		zilog->zl_suspend--;
3225		mutex_exit(&zilog->zl_lock);
3226		dsl_dataset_long_rele(dmu_objset_ds(os), suspend_tag);
3227		dsl_dataset_rele(dmu_objset_ds(os), suspend_tag);
3228		return (SET_ERROR(EBUSY));
3229	}
3230
3231	zilog->zl_suspending = B_TRUE;
3232	mutex_exit(&zilog->zl_lock);
3233
3234	/*
3235	 * We need to use zil_commit_impl to ensure we wait for all
3236	 * LWB_STATE_OPENED and LWB_STATE_ISSUED lwb's to be committed
3237	 * to disk before proceeding. If we used zil_commit instead, it
3238	 * would just call txg_wait_synced(), because zl_suspend is set.
3239	 * txg_wait_synced() doesn't wait for these lwb's to be
3240	 * LWB_STATE_FLUSH_DONE before returning.
3241	 */
3242	zil_commit_impl(zilog, 0);
3243
3244	/*
3245	 * Now that we've ensured all lwb's are LWB_STATE_DONE,
3246	 * txg_wait_synced() will be called from within zil_destroy(),
3247	 * which will ensure the data from the zilog has migrated to the
3248	 * main pool before it returns.
3249	 */
3250	txg_wait_synced(zilog->zl_dmu_pool, 0);
3251
3252	zil_destroy(zilog, B_FALSE);
3253
3254	mutex_enter(&zilog->zl_lock);
3255	zilog->zl_suspending = B_FALSE;
3256	cv_broadcast(&zilog->zl_cv_suspend);
3257	mutex_exit(&zilog->zl_lock);
3258
3259	if (os->os_encrypted)
3260		dsl_dataset_remove_key_mapping(dmu_objset_ds(os));
3261
3262	if (cookiep == NULL)
3263		zil_resume(os);
3264	else
3265		*cookiep = os;
3266	return (0);
3267}
3268
3269void
3270zil_resume(void *cookie)
3271{
3272	objset_t *os = cookie;
3273	zilog_t *zilog = dmu_objset_zil(os);
3274
3275	mutex_enter(&zilog->zl_lock);
3276	ASSERT(zilog->zl_suspend != 0);
3277	zilog->zl_suspend--;
3278	mutex_exit(&zilog->zl_lock);
3279	dsl_dataset_long_rele(dmu_objset_ds(os), suspend_tag);
3280	dsl_dataset_rele(dmu_objset_ds(os), suspend_tag);
3281}
3282
3283typedef struct zil_replay_arg {
3284	zil_replay_func_t **zr_replay;
3285	void		*zr_arg;
3286	boolean_t	zr_byteswap;
3287	char		*zr_lr;
3288} zil_replay_arg_t;
3289
3290static int
3291zil_replay_error(zilog_t *zilog, lr_t *lr, int error)
3292{
3293	char name[ZFS_MAX_DATASET_NAME_LEN];
3294
3295	zilog->zl_replaying_seq--;	/* didn't actually replay this one */
3296
3297	dmu_objset_name(zilog->zl_os, name);
3298
3299	cmn_err(CE_WARN, "ZFS replay transaction error %d, "
3300	    "dataset %s, seq 0x%llx, txtype %llu %s\n", error, name,
3301	    (u_longlong_t)lr->lrc_seq,
3302	    (u_longlong_t)(lr->lrc_txtype & ~TX_CI),
3303	    (lr->lrc_txtype & TX_CI) ? "CI" : "");
3304
3305	return (error);
3306}
3307
3308static int
3309zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
3310{
3311	zil_replay_arg_t *zr = zra;
3312	const zil_header_t *zh = zilog->zl_header;
3313	uint64_t reclen = lr->lrc_reclen;
3314	uint64_t txtype = lr->lrc_txtype;
3315	int error = 0;
3316
3317	zilog->zl_replaying_seq = lr->lrc_seq;
3318
3319	if (lr->lrc_seq <= zh->zh_replay_seq)	/* already replayed */
3320		return (0);
3321
3322	if (lr->lrc_txg < claim_txg)		/* already committed */
3323		return (0);
3324
3325	/* Strip case-insensitive bit, still present in log record */
3326	txtype &= ~TX_CI;
3327
3328	if (txtype == 0 || txtype >= TX_MAX_TYPE)
3329		return (zil_replay_error(zilog, lr, EINVAL));
3330
3331	/*
3332	 * If this record type can be logged out of order, the object
3333	 * (lr_foid) may no longer exist.  That's legitimate, not an error.
3334	 */
3335	if (TX_OOO(txtype)) {
3336		error = dmu_object_info(zilog->zl_os,
3337		    LR_FOID_GET_OBJ(((lr_ooo_t *)lr)->lr_foid), NULL);
3338		if (error == ENOENT || error == EEXIST)
3339			return (0);
3340	}
3341
3342	/*
3343	 * Make a copy of the data so we can revise and extend it.
3344	 */
3345	bcopy(lr, zr->zr_lr, reclen);
3346
3347	/*
3348	 * If this is a TX_WRITE with a blkptr, suck in the data.
3349	 */
3350	if (txtype == TX_WRITE && reclen == sizeof (lr_write_t)) {
3351		error = zil_read_log_data(zilog, (lr_write_t *)lr,
3352		    zr->zr_lr + reclen);
3353		if (error != 0)
3354			return (zil_replay_error(zilog, lr, error));
3355	}
3356
3357	/*
3358	 * The log block containing this lr may have been byteswapped
3359	 * so that we can easily examine common fields like lrc_txtype.
3360	 * However, the log is a mix of different record types, and only the
3361	 * replay vectors know how to byteswap their records.  Therefore, if
3362	 * the lr was byteswapped, undo it before invoking the replay vector.
3363	 */
3364	if (zr->zr_byteswap)
3365		byteswap_uint64_array(zr->zr_lr, reclen);
3366
3367	/*
3368	 * We must now do two things atomically: replay this log record,
3369	 * and update the log header sequence number to reflect the fact that
3370	 * we did so. At the end of each replay function the sequence number
3371	 * is updated if we are in replay mode.
3372	 */
3373	error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lr, zr->zr_byteswap);
3374	if (error != 0) {
3375		/*
3376		 * The DMU's dnode layer doesn't see removes until the txg
3377		 * commits, so a subsequent claim can spuriously fail with
3378		 * EEXIST. So if we receive any error we try syncing out
3379		 * any removes then retry the transaction.  Note that we
3380		 * specify B_FALSE for byteswap now, so we don't do it twice.
3381		 */
3382		txg_wait_synced(spa_get_dsl(zilog->zl_spa), 0);
3383		error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lr, B_FALSE);
3384		if (error != 0)
3385			return (zil_replay_error(zilog, lr, error));
3386	}
3387	return (0);
3388}
3389
3390/* ARGSUSED */
3391static int
3392zil_incr_blks(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
3393{
3394	zilog->zl_replay_blks++;
3395
3396	return (0);
3397}
3398
3399/*
3400 * If this dataset has a non-empty intent log, replay it and destroy it.
3401 */
3402void
3403zil_replay(objset_t *os, void *arg, zil_replay_func_t *replay_func[TX_MAX_TYPE])
3404{
3405	zilog_t *zilog = dmu_objset_zil(os);
3406	const zil_header_t *zh = zilog->zl_header;
3407	zil_replay_arg_t zr;
3408
3409	if ((zh->zh_flags & ZIL_REPLAY_NEEDED) == 0) {
3410		zil_destroy(zilog, B_TRUE);
3411		return;
3412	}
3413
3414	zr.zr_replay = replay_func;
3415	zr.zr_arg = arg;
3416	zr.zr_byteswap = BP_SHOULD_BYTESWAP(&zh->zh_log);
3417	zr.zr_lr = kmem_alloc(2 * SPA_MAXBLOCKSIZE, KM_SLEEP);
3418
3419	/*
3420	 * Wait for in-progress removes to sync before starting replay.
3421	 */
3422	txg_wait_synced(zilog->zl_dmu_pool, 0);
3423
3424	zilog->zl_replay = B_TRUE;
3425	zilog->zl_replay_time = ddi_get_lbolt();
3426	ASSERT(zilog->zl_replay_blks == 0);
3427	(void) zil_parse(zilog, zil_incr_blks, zil_replay_log_record, &zr,
3428	    zh->zh_claim_txg, B_TRUE);
3429	kmem_free(zr.zr_lr, 2 * SPA_MAXBLOCKSIZE);
3430
3431	zil_destroy(zilog, B_FALSE);
3432	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
3433	zilog->zl_replay = B_FALSE;
3434}
3435
3436boolean_t
3437zil_replaying(zilog_t *zilog, dmu_tx_t *tx)
3438{
3439	if (zilog->zl_sync == ZFS_SYNC_DISABLED)
3440		return (B_TRUE);
3441
3442	if (zilog->zl_replay) {
3443		dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
3444		zilog->zl_replayed_seq[dmu_tx_get_txg(tx) & TXG_MASK] =
3445		    zilog->zl_replaying_seq;
3446		return (B_TRUE);
3447	}
3448
3449	return (B_FALSE);
3450}
3451
3452/* ARGSUSED */
3453int
3454zil_reset(const char *osname, void *arg)
3455{
3456	int error;
3457
3458	error = zil_suspend(osname, NULL);
3459	if (error != 0)
3460		return (SET_ERROR(EEXIST));
3461	return (0);
3462}
3463