Update core ZFS code from build 121 to build 141.

1 files changed, 588 insertions, 495 deletions

diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index db3822f5a..4aa4d10b0 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -19,13 +19,13 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
- * Use is subject to license terms.
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  */
 
+/* Portions Copyright 2010 Robert Milkowski */
+
 #include <sys/zfs_context.h>
 #include <sys/spa.h>
-#include <sys/spa_impl.h>
 #include <sys/dmu.h>
 #include <sys/zap.h>
 #include <sys/arc.h>
@@ -36,6 +36,7 @@
 #include <sys/dsl_dataset.h>
 #include <sys/vdev.h>
 #include <sys/dmu_tx.h>
+#include <sys/dsl_pool.h>
 
 /*
  * The zfs intent log (ZIL) saves transaction records of system calls
@@ -66,7 +67,7 @@
 /*
  * This global ZIL switch affects all pools
  */
-int zil_disable = 0;	/* disable intent logging */
+int zil_replay_disable = 0;    /* disable intent logging replay */
 
 /*
  * Tunable parameter for debugging or performance analysis.  Setting
@@ -77,11 +78,17 @@ boolean_t zfs_nocacheflush = B_FALSE;
 
 static kmem_cache_t *zil_lwb_cache;
 
+static boolean_t zil_empty(zilog_t *zilog);
+
+#define	LWB_EMPTY(lwb) ((BP_GET_LSIZE(&lwb->lwb_blk) - \
+    sizeof (zil_chain_t)) == (lwb->lwb_sz - lwb->lwb_nused))
+
+
 static int
-zil_dva_compare(const void *x1, const void *x2)
+zil_bp_compare(const void *x1, const void *x2)
 {
-	const dva_t *dva1 = x1;
-	const dva_t *dva2 = x2;
+	const dva_t *dva1 = &((zil_bp_node_t *)x1)->zn_dva;
+	const dva_t *dva2 = &((zil_bp_node_t *)x2)->zn_dva;
 
 	if (DVA_GET_VDEV(dva1) < DVA_GET_VDEV(dva2))
 		return (-1);
@@ -97,34 +104,37 @@ zil_dva_compare(const void *x1, const void *x2)
 }
 
 static void
-zil_dva_tree_init(avl_tree_t *t)
+zil_bp_tree_init(zilog_t *zilog)
 {
-	avl_create(t, zil_dva_compare, sizeof (zil_dva_node_t),
-	    offsetof(zil_dva_node_t, zn_node));
+	avl_create(&zilog->zl_bp_tree, zil_bp_compare,
+	    sizeof (zil_bp_node_t), offsetof(zil_bp_node_t, zn_node));
 }
 
 static void
-zil_dva_tree_fini(avl_tree_t *t)
+zil_bp_tree_fini(zilog_t *zilog)
 {
-	zil_dva_node_t *zn;
+	avl_tree_t *t = &zilog->zl_bp_tree;
+	zil_bp_node_t *zn;
 	void *cookie = NULL;
 
 	while ((zn = avl_destroy_nodes(t, &cookie)) != NULL)
-		kmem_free(zn, sizeof (zil_dva_node_t));
+		kmem_free(zn, sizeof (zil_bp_node_t));
 
 	avl_destroy(t);
 }
 
-static int
-zil_dva_tree_add(avl_tree_t *t, dva_t *dva)
+int
+zil_bp_tree_add(zilog_t *zilog, const blkptr_t *bp)
 {
-	zil_dva_node_t *zn;
+	avl_tree_t *t = &zilog->zl_bp_tree;
+	const dva_t *dva = BP_IDENTITY(bp);
+	zil_bp_node_t *zn;
 	avl_index_t where;
 
 	if (avl_find(t, dva, &where) != NULL)
 		return (EEXIST);
 
-	zn = kmem_alloc(sizeof (zil_dva_node_t), KM_SLEEP);
+	zn = kmem_alloc(sizeof (zil_bp_node_t), KM_SLEEP);
 	zn->zn_dva = *dva;
 	avl_insert(t, zn, where);
 
@@ -149,35 +159,31 @@ zil_init_log_chain(zilog_t *zilog, blkptr_t *bp)
 }
 
 /*
- * Read a log block, make sure it's valid, and byteswap it if necessary.
+ * Read a log block and make sure it's valid.
  */
 static int
-zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, arc_buf_t **abufpp)
+zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, blkptr_t *nbp, void *dst,
+    char **end)
 {
-	blkptr_t blk = *bp;
-	zbookmark_t zb;
+	enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
 	uint32_t aflags = ARC_WAIT;
+	arc_buf_t *abuf = NULL;
+	zbookmark_t zb;
 	int error;
 
-	zb.zb_objset = bp->blk_cksum.zc_word[ZIL_ZC_OBJSET];
-	zb.zb_object = 0;
-	zb.zb_level = -1;
-	zb.zb_blkid = bp->blk_cksum.zc_word[ZIL_ZC_SEQ];
+	if (zilog->zl_header->zh_claim_txg == 0)
+		zio_flags |= ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB;
 
-	*abufpp = NULL;
+	if (!(zilog->zl_header->zh_flags & ZIL_CLAIM_LR_SEQ_VALID))
+		zio_flags |= ZIO_FLAG_SPECULATIVE;
 
-	/*
-	 * We shouldn't be doing any scrubbing while we're doing log
-	 * replay, it's OK to not lock.
-	 */
-	error = arc_read_nolock(NULL, zilog->zl_spa, &blk,
-	    arc_getbuf_func, abufpp, ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL |
-	    ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB, &aflags, &zb);
+	SET_BOOKMARK(&zb, bp->blk_cksum.zc_word[ZIL_ZC_OBJSET],
+	    ZB_ZIL_OBJECT, ZB_ZIL_LEVEL, bp->blk_cksum.zc_word[ZIL_ZC_SEQ]);
+
+	error = dsl_read_nolock(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
+	    ZIO_PRIORITY_SYNC_READ, zio_flags, &aflags, &zb);
 
 	if (error == 0) {
-		char *data = (*abufpp)->b_data;
-		uint64_t blksz = BP_GET_LSIZE(bp);
-		zil_trailer_t *ztp = (zil_trailer_t *)(data + blksz) - 1;
 		zio_cksum_t cksum = bp->blk_cksum;
 
 		/*
@@ -190,43 +196,102 @@ zil_read_log_block(zilog_t *zilog, const blkptr_t *bp, arc_buf_t **abufpp)
 		 */
 		cksum.zc_word[ZIL_ZC_SEQ]++;
 
-		if (bcmp(&cksum, &ztp->zit_next_blk.blk_cksum,
-		    sizeof (cksum)) || BP_IS_HOLE(&ztp->zit_next_blk) ||
-		    (ztp->zit_nused > (blksz - sizeof (zil_trailer_t)))) {
-			error = ECKSUM;
-		}
+		if (BP_GET_CHECKSUM(bp) == ZIO_CHECKSUM_ZILOG2) {
+			zil_chain_t *zilc = abuf->b_data;
+			char *lr = (char *)(zilc + 1);
+			uint64_t len = zilc->zc_nused - sizeof (zil_chain_t);
 
-		if (error) {
-			VERIFY(arc_buf_remove_ref(*abufpp, abufpp) == 1);
-			*abufpp = NULL;
+			if (bcmp(&cksum, &zilc->zc_next_blk.blk_cksum,
+			    sizeof (cksum)) || BP_IS_HOLE(&zilc->zc_next_blk)) {
+				error = ECKSUM;
+			} else {
+				bcopy(lr, dst, len);
+				*end = (char *)dst + len;
+				*nbp = zilc->zc_next_blk;
+			}
+		} else {
+			char *lr = abuf->b_data;
+			uint64_t size = BP_GET_LSIZE(bp);
+			zil_chain_t *zilc = (zil_chain_t *)(lr + size) - 1;
+
+			if (bcmp(&cksum, &zilc->zc_next_blk.blk_cksum,
+			    sizeof (cksum)) || BP_IS_HOLE(&zilc->zc_next_blk) ||
+			    (zilc->zc_nused > (size - sizeof (*zilc)))) {
+				error = ECKSUM;
+			} else {
+				bcopy(lr, dst, zilc->zc_nused);
+				*end = (char *)dst + zilc->zc_nused;
+				*nbp = zilc->zc_next_blk;
+			}
 		}
+
+		VERIFY(arc_buf_remove_ref(abuf, &abuf) == 1);
+	}
+
+	return (error);
+}
+
+/*
+ * Read a TX_WRITE log data block.
+ */
+static int
+zil_read_log_data(zilog_t *zilog, const lr_write_t *lr, void *wbuf)
+{
+	enum zio_flag zio_flags = ZIO_FLAG_CANFAIL;
+	const blkptr_t *bp = &lr->lr_blkptr;
+	uint32_t aflags = ARC_WAIT;
+	arc_buf_t *abuf = NULL;
+	zbookmark_t zb;
+	int error;
+
+	if (BP_IS_HOLE(bp)) {
+		if (wbuf != NULL)
+			bzero(wbuf, MAX(BP_GET_LSIZE(bp), lr->lr_length));
+		return (0);
 	}
 
-	dprintf("error %d on %llu:%llu\n", error, zb.zb_objset, zb.zb_blkid);
+	if (zilog->zl_header->zh_claim_txg == 0)
+		zio_flags |= ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB;
+
+	SET_BOOKMARK(&zb, dmu_objset_id(zilog->zl_os), lr->lr_foid,
+	    ZB_ZIL_LEVEL, lr->lr_offset / BP_GET_LSIZE(bp));
+
+	error = arc_read_nolock(NULL, zilog->zl_spa, bp, arc_getbuf_func, &abuf,
+	    ZIO_PRIORITY_SYNC_READ, zio_flags, &aflags, &zb);
+
+	if (error == 0) {
+		if (wbuf != NULL)
+			bcopy(abuf->b_data, wbuf, arc_buf_size(abuf));
+		(void) arc_buf_remove_ref(abuf, &abuf);
+	}
 
 	return (error);
 }
 
 /*
  * Parse the intent log, and call parse_func for each valid record within.
- * Return the highest sequence number.
  */
-uint64_t
+int
 zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
     zil_parse_lr_func_t *parse_lr_func, void *arg, uint64_t txg)
 {
 	const zil_header_t *zh = zilog->zl_header;
-	uint64_t claim_seq = zh->zh_claim_seq;
-	uint64_t seq = 0;
-	uint64_t max_seq = 0;
-	blkptr_t blk = zh->zh_log;
-	arc_buf_t *abuf;
+	boolean_t claimed = !!zh->zh_claim_txg;
+	uint64_t claim_blk_seq = claimed ? zh->zh_claim_blk_seq : UINT64_MAX;
+	uint64_t claim_lr_seq = claimed ? zh->zh_claim_lr_seq : UINT64_MAX;
+	uint64_t max_blk_seq = 0;
+	uint64_t max_lr_seq = 0;
+	uint64_t blk_count = 0;
+	uint64_t lr_count = 0;
+	blkptr_t blk, next_blk;
 	char *lrbuf, *lrp;
-	zil_trailer_t *ztp;
-	int reclen, error;
+	int error = 0;
 
-	if (BP_IS_HOLE(&blk))
-		return (max_seq);
+	/*
+	 * Old logs didn't record the maximum zh_claim_lr_seq.
+	 */
+	if (!(zh->zh_flags & ZIL_CLAIM_LR_SEQ_VALID))
+		claim_lr_seq = UINT64_MAX;
 
 	/*
 	 * Starting at the block pointed to by zh_log we read the log chain.
@@ -237,105 +302,156 @@ zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
 	 * If the log has been claimed, stop if we encounter a sequence
 	 * number greater than the highest claimed sequence number.
 	 */
-	zil_dva_tree_init(&zilog->zl_dva_tree);
-	for (;;) {
-		seq = blk.blk_cksum.zc_word[ZIL_ZC_SEQ];
+	lrbuf = zio_buf_alloc(SPA_MAXBLOCKSIZE);
+	zil_bp_tree_init(zilog);
 
-		if (claim_seq != 0 && seq > claim_seq)
-			break;
-
-		ASSERT(max_seq < seq);
-		max_seq = seq;
+	for (blk = zh->zh_log; !BP_IS_HOLE(&blk); blk = next_blk) {
+		uint64_t blk_seq = blk.blk_cksum.zc_word[ZIL_ZC_SEQ];
+		int reclen;
+		char *end;
 
-		error = zil_read_log_block(zilog, &blk, &abuf);
+		if (blk_seq > claim_blk_seq)
+			break;
+		if ((error = parse_blk_func(zilog, &blk, arg, txg)) != 0)
+			break;
+		ASSERT3U(max_blk_seq, <, blk_seq);
+		max_blk_seq = blk_seq;
+		blk_count++;
 
-		if (parse_blk_func != NULL)
-			parse_blk_func(zilog, &blk, arg, txg);
+		if (max_lr_seq == claim_lr_seq && max_blk_seq == claim_blk_seq)
+			break;
 
+		error = zil_read_log_block(zilog, &blk, &next_blk, lrbuf, &end);
 		if (error)
 			break;
 
-		lrbuf = abuf->b_data;
-		ztp = (zil_trailer_t *)(lrbuf + BP_GET_LSIZE(&blk)) - 1;
-		blk = ztp->zit_next_blk;
-
-		if (parse_lr_func == NULL) {
-			VERIFY(arc_buf_remove_ref(abuf, &abuf) == 1);
-			continue;
-		}
-
-		for (lrp = lrbuf; lrp < lrbuf + ztp->zit_nused; lrp += reclen) {
+		for (lrp = lrbuf; lrp < end; lrp += reclen) {
 			lr_t *lr = (lr_t *)lrp;
 			reclen = lr->lrc_reclen;
 			ASSERT3U(reclen, >=, sizeof (lr_t));
-			parse_lr_func(zilog, lr, arg, txg);
+			if (lr->lrc_seq > claim_lr_seq)
+				goto done;
+			if ((error = parse_lr_func(zilog, lr, arg, txg)) != 0)
+				goto done;
+			ASSERT3U(max_lr_seq, <, lr->lrc_seq);
+			max_lr_seq = lr->lrc_seq;
+			lr_count++;
 		}
-		VERIFY(arc_buf_remove_ref(abuf, &abuf) == 1);
 	}
-	zil_dva_tree_fini(&zilog->zl_dva_tree);
+done:
+	zilog->zl_parse_error = error;
+	zilog->zl_parse_blk_seq = max_blk_seq;
+	zilog->zl_parse_lr_seq = max_lr_seq;
+	zilog->zl_parse_blk_count = blk_count;
+	zilog->zl_parse_lr_count = lr_count;
+
+	ASSERT(!claimed || !(zh->zh_flags & ZIL_CLAIM_LR_SEQ_VALID) ||
+	    (max_blk_seq == claim_blk_seq && max_lr_seq == claim_lr_seq));
+
+	zil_bp_tree_fini(zilog);
+	zio_buf_free(lrbuf, SPA_MAXBLOCKSIZE);
 
-	return (max_seq);
+	return (error);
 }
 
-/* ARGSUSED */
-static void
+static int
 zil_claim_log_block(zilog_t *zilog, blkptr_t *bp, void *tx, uint64_t first_txg)
 {
-	spa_t *spa = zilog->zl_spa;
-	int err;
-
 	/*
 	 * Claim log block if not already committed and not already claimed.
+	 * If tx == NULL, just verify that the block is claimable.
 	 */
-	if (bp->blk_birth >= first_txg &&
-	    zil_dva_tree_add(&zilog->zl_dva_tree, BP_IDENTITY(bp)) == 0) {
-		err = zio_wait(zio_claim(NULL, spa, first_txg, bp, NULL, NULL,
-		    ZIO_FLAG_MUSTSUCCEED));
-		ASSERT(err == 0);
-	}
+	if (bp->blk_birth < first_txg || zil_bp_tree_add(zilog, bp) != 0)
+		return (0);
+
+	return (zio_wait(zio_claim(NULL, zilog->zl_spa,
+	    tx == NULL ? 0 : first_txg, bp, spa_claim_notify, NULL,
+	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_SCRUB)));
 }
 
-static void
+static int
 zil_claim_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t first_txg)
 {
-	if (lrc->lrc_txtype == TX_WRITE) {
-		lr_write_t *lr = (lr_write_t *)lrc;
-		zil_claim_log_block(zilog, &lr->lr_blkptr, tx, first_txg);
-	}
+	lr_write_t *lr = (lr_write_t *)lrc;
+	int error;
+
+	if (lrc->lrc_txtype != TX_WRITE)
+		return (0);
+
+	/*
+	 * If the block is not readable, don't claim it.  This can happen
+	 * in normal operation when a log block is written to disk before
+	 * some of the dmu_sync() blocks it points to.  In this case, the
+	 * transaction cannot have been committed to anyone (we would have
+	 * waited for all writes to be stable first), so it is semantically
+	 * correct to declare this the end of the log.
+	 */
+	if (lr->lr_blkptr.blk_birth >= first_txg &&
+	    (error = zil_read_log_data(zilog, lr, NULL)) != 0)
+		return (error);
+	return (zil_claim_log_block(zilog, &lr->lr_blkptr, tx, first_txg));
 }
 
 /* ARGSUSED */
-static void
+static int
 zil_free_log_block(zilog_t *zilog, blkptr_t *bp, void *tx, uint64_t claim_txg)
 {
-	zio_free_blk(zilog->zl_spa, bp, dmu_tx_get_txg(tx));
+	zio_free_zil(zilog->zl_spa, dmu_tx_get_txg(tx), bp);
+
+	return (0);
 }
 
-static void
+static int
 zil_free_log_record(zilog_t *zilog, lr_t *lrc, void *tx, uint64_t claim_txg)
 {
+	lr_write_t *lr = (lr_write_t *)lrc;
+	blkptr_t *bp = &lr->lr_blkptr;
+
 	/*
 	 * If we previously claimed it, we need to free it.
 	 */
-	if (claim_txg != 0 && lrc->lrc_txtype == TX_WRITE) {
-		lr_write_t *lr = (lr_write_t *)lrc;
-		blkptr_t *bp = &lr->lr_blkptr;
-		if (bp->blk_birth >= claim_txg &&
-		    !zil_dva_tree_add(&zilog->zl_dva_tree, BP_IDENTITY(bp))) {
-			(void) arc_free(NULL, zilog->zl_spa,
-			    dmu_tx_get_txg(tx), bp, NULL, NULL, ARC_WAIT);
-		}
+	if (claim_txg != 0 && lrc->lrc_txtype == TX_WRITE &&
+	    bp->blk_birth >= claim_txg && zil_bp_tree_add(zilog, bp) == 0)
+		zio_free(zilog->zl_spa, dmu_tx_get_txg(tx), bp);
+
+	return (0);
+}
+
+static lwb_t *
+zil_alloc_lwb(zilog_t *zilog, blkptr_t *bp, uint64_t txg)
+{
+	lwb_t *lwb;
+
+	lwb = kmem_cache_alloc(zil_lwb_cache, KM_SLEEP);
+	lwb->lwb_zilog = zilog;
+	lwb->lwb_blk = *bp;
+	lwb->lwb_buf = zio_buf_alloc(BP_GET_LSIZE(bp));
+	lwb->lwb_max_txg = txg;
+	lwb->lwb_zio = NULL;
+	lwb->lwb_tx = NULL;
+	if (BP_GET_CHECKSUM(bp) == ZIO_CHECKSUM_ZILOG2) {
+		lwb->lwb_nused = sizeof (zil_chain_t);
+		lwb->lwb_sz = BP_GET_LSIZE(bp);
+	} else {
+		lwb->lwb_nused = 0;
+		lwb->lwb_sz = BP_GET_LSIZE(bp) - sizeof (zil_chain_t);
 	}
+
+	mutex_enter(&zilog->zl_lock);
+	list_insert_tail(&zilog->zl_lwb_list, lwb);
+	mutex_exit(&zilog->zl_lock);
+
+	return (lwb);
 }
 
 /*
  * Create an on-disk intent log.
  */
-static void
+static lwb_t *
 zil_create(zilog_t *zilog)
 {
 	const zil_header_t *zh = zilog->zl_header;
-	lwb_t *lwb;
+	lwb_t *lwb = NULL;
 	uint64_t txg = 0;
 	dmu_tx_t *tx = NULL;
 	blkptr_t blk;
@@ -352,22 +468,23 @@ zil_create(zilog_t *zilog)
 	blk = zh->zh_log;
 
 	/*
-	 * If we don't already have an initial log block or we have one
-	 * but it's the wrong endianness then allocate one.
+	 * Allocate an initial log block if:
+	 *    - there isn't one already
+	 *    - the existing block is the wrong endianess
 	 */
 	if (BP_IS_HOLE(&blk) || BP_SHOULD_BYTESWAP(&blk)) {
 		tx = dmu_tx_create(zilog->zl_os);
-		(void) dmu_tx_assign(tx, TXG_WAIT);
+		VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0);
 		dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
 		txg = dmu_tx_get_txg(tx);
 
 		if (!BP_IS_HOLE(&blk)) {
-			zio_free_blk(zilog->zl_spa, &blk, txg);
+			zio_free_zil(zilog->zl_spa, txg, &blk);
 			BP_ZERO(&blk);
 		}
 
-		error = zio_alloc_blk(zilog->zl_spa, ZIL_MIN_BLKSZ, &blk,
-		    NULL, txg);
+		error = zio_alloc_zil(zilog->zl_spa, txg, &blk, NULL,
+		    ZIL_MIN_BLKSZ, zilog->zl_logbias == ZFS_LOGBIAS_LATENCY);
 
 		if (error == 0)
 			zil_init_log_chain(zilog, &blk);
@@ -376,20 +493,8 @@ zil_create(zilog_t *zilog)
 	/*
 	 * Allocate a log write buffer (lwb) for the first log block.
 	 */
-	if (error == 0) {
-		lwb = kmem_cache_alloc(zil_lwb_cache, KM_SLEEP);
-		lwb->lwb_zilog = zilog;
-		lwb->lwb_blk = blk;
-		lwb->lwb_nused = 0;
-		lwb->lwb_sz = BP_GET_LSIZE(&lwb->lwb_blk);
-		lwb->lwb_buf = zio_buf_alloc(lwb->lwb_sz);
-		lwb->lwb_max_txg = txg;
-		lwb->lwb_zio = NULL;
-
-		mutex_enter(&zilog->zl_lock);
-		list_insert_tail(&zilog->zl_lwb_list, lwb);
-		mutex_exit(&zilog->zl_lock);
-	}
+	if (error == 0)
+		lwb = zil_alloc_lwb(zilog, &blk, txg);
 
 	/*
 	 * If we just allocated the first log block, commit our transaction
@@ -402,6 +507,8 @@ zil_create(zilog_t *zilog)
 	}
 
 	ASSERT(bcmp(&blk, &zh->zh_log, sizeof (blk)) == 0);
+
+	return (lwb);
 }
 
 /*
@@ -426,26 +533,18 @@ zil_destroy(zilog_t *zilog, boolean_t keep_first)
 	 */
 	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
 
+	zilog->zl_old_header = *zh;		/* debugging aid */
+
 	if (BP_IS_HOLE(&zh->zh_log))
 		return;
 
 	tx = dmu_tx_create(zilog->zl_os);
-	(void) dmu_tx_assign(tx, TXG_WAIT);
+	VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0);
 	dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
 	txg = dmu_tx_get_txg(tx);
 
 	mutex_enter(&zilog->zl_lock);
 
-	/*
-	 * It is possible for the ZIL to get the previously mounted zilog
-	 * structure of the same dataset if quickly remounted and the dbuf
-	 * eviction has not completed. In this case we can see a non
-	 * empty lwb list and keep_first will be set. We fix this by
-	 * clearing the keep_first. This will be slower but it's very rare.
-	 */
-	if (!list_is_empty(&zilog->zl_lwb_list) && keep_first)
-		keep_first = B_FALSE;
-
 	ASSERT3U(zilog->zl_destroy_txg, <, txg);
 	zilog->zl_destroy_txg = txg;
 	zilog->zl_keep_first = keep_first;
@@ -457,41 +556,20 @@ zil_destroy(zilog_t *zilog, boolean_t keep_first)
 			list_remove(&zilog->zl_lwb_list, lwb);
 			if (lwb->lwb_buf != NULL)
 				zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
-			zio_free_blk(zilog->zl_spa, &lwb->lwb_blk, txg);
+			zio_free_zil(zilog->zl_spa, txg, &lwb->lwb_blk);
 			kmem_cache_free(zil_lwb_cache, lwb);
 		}
-	} else {
-		if (!keep_first) {
-			(void) zil_parse(zilog, zil_free_log_block,
-			    zil_free_log_record, tx, zh->zh_claim_txg);
-		}
+	} else if (!keep_first) {
+		(void) zil_parse(zilog, zil_free_log_block,
+		    zil_free_log_record, tx, zh->zh_claim_txg);
 	}
 	mutex_exit(&zilog->zl_lock);
 
 	dmu_tx_commit(tx);
 }
 
-/*
- * return true if the initial log block is not valid
- */
-static boolean_t
-zil_empty(zilog_t *zilog)
-{
-	const zil_header_t *zh = zilog->zl_header;
-	arc_buf_t *abuf = NULL;
-
-	if (BP_IS_HOLE(&zh->zh_log))
-		return (B_TRUE);
-
-	if (zil_read_log_block(zilog, &zh->zh_log, &abuf) != 0)
-		return (B_TRUE);
-
-	VERIFY(arc_buf_remove_ref(abuf, &abuf) == 1);
-	return (B_FALSE);
-}
-
 int
-zil_claim(char *osname, void *txarg)
+zil_claim(const char *osname, void *txarg)
 {
 	dmu_tx_t *tx = txarg;
 	uint64_t first_txg = dmu_tx_get_txg(tx);
@@ -500,7 +578,7 @@ zil_claim(char *osname, void *txarg)
 	objset_t *os;
 	int error;
 
-	error = dmu_objset_open(osname, DMU_OST_ANY, DS_MODE_USER, &os);
+	error = dmu_objset_hold(osname, FTAG, &os);
 	if (error) {
 		cmn_err(CE_WARN, "can't open objset for %s", osname);
 		return (0);
@@ -509,28 +587,13 @@ zil_claim(char *osname, void *txarg)
 	zilog = dmu_objset_zil(os);
 	zh = zil_header_in_syncing_context(zilog);
 
-	if (zilog->zl_spa->spa_log_state == SPA_LOG_CLEAR) {
+	if (spa_get_log_state(zilog->zl_spa) == SPA_LOG_CLEAR) {
 		if (!BP_IS_HOLE(&zh->zh_log))
-			zio_free_blk(zilog->zl_spa, &zh->zh_log, first_txg);
+			zio_free_zil(zilog->zl_spa, first_txg, &zh->zh_log);
 		BP_ZERO(&zh->zh_log);
 		dsl_dataset_dirty(dmu_objset_ds(os), tx);
-	}
-
-	/*
-	 * Record here whether the zil has any records to replay.
-	 * If the header block pointer is null or the block points
-	 * to the stubby then we know there are no valid log records.
-	 * We use the header to store this state as the the zilog gets
-	 * freed later in dmu_objset_close().
-	 * The flags (and the rest of the header fields) are cleared in
-	 * zil_sync() as a result of a zil_destroy(), after replaying the log.
-	 *
-	 * Note, the intent log can be empty but still need the
-	 * stubby to be claimed.
-	 */
-	if (!zil_empty(zilog)) {
-		zh->zh_flags |= ZIL_REPLAY_NEEDED;
-		dsl_dataset_dirty(dmu_objset_ds(os), tx);
+		dmu_objset_rele(os, FTAG);
+		return (0);
 	}
 
 	/*
@@ -542,14 +605,19 @@ zil_claim(char *osname, void *txarg)
 	 */
 	ASSERT3U(zh->zh_claim_txg, <=, first_txg);
 	if (zh->zh_claim_txg == 0 && !BP_IS_HOLE(&zh->zh_log)) {
-		zh->zh_claim_txg = first_txg;
-		zh->zh_claim_seq = zil_parse(zilog, zil_claim_log_block,
+		(void) zil_parse(zilog, zil_claim_log_block,
 		    zil_claim_log_record, tx, first_txg);
+		zh->zh_claim_txg = first_txg;
+		zh->zh_claim_blk_seq = zilog->zl_parse_blk_seq;
+		zh->zh_claim_lr_seq = zilog->zl_parse_lr_seq;
+		if (zilog->zl_parse_lr_count || zilog->zl_parse_blk_count > 1)
+			zh->zh_flags |= ZIL_REPLAY_NEEDED;
+		zh->zh_flags |= ZIL_CLAIM_LR_SEQ_VALID;
 		dsl_dataset_dirty(dmu_objset_ds(os), tx);
 	}
 
 	ASSERT3U(first_txg, ==, (spa_last_synced_txg(zilog->zl_spa) + 1));
-	dmu_objset_close(os);
+	dmu_objset_rele(os, FTAG);
 	return (0);
 }
 
@@ -558,46 +626,36 @@ zil_claim(char *osname, void *txarg)
  * Checksum errors are ok as they indicate the end of the chain.
  * Any other error (no device or read failure) returns an error.
  */
-/* ARGSUSED */
 int
-zil_check_log_chain(char *osname, void *txarg)
+zil_check_log_chain(const char *osname, void *tx)
 {
 	zilog_t *zilog;
-	zil_header_t *zh;
-	blkptr_t blk;
-	arc_buf_t *abuf;
 	objset_t *os;
-	char *lrbuf;
-	zil_trailer_t *ztp;
 	int error;
 
-	error = dmu_objset_open(osname, DMU_OST_ANY, DS_MODE_USER, &os);
+	ASSERT(tx == NULL);
+
+	error = dmu_objset_hold(osname, FTAG, &os);
 	if (error) {
 		cmn_err(CE_WARN, "can't open objset for %s", osname);
 		return (0);
 	}
 
 	zilog = dmu_objset_zil(os);
-	zh = zil_header_in_syncing_context(zilog);
-	blk = zh->zh_log;
-	if (BP_IS_HOLE(&blk)) {
-		dmu_objset_close(os);
-		return (0); /* no chain */
-	}
 
-	for (;;) {
-		error = zil_read_log_block(zilog, &blk, &abuf);
-		if (error)
-			break;
-		lrbuf = abuf->b_data;
-		ztp = (zil_trailer_t *)(lrbuf + BP_GET_LSIZE(&blk)) - 1;
-		blk = ztp->zit_next_blk;
-		VERIFY(arc_buf_remove_ref(abuf, &abuf) == 1);
-	}
-	dmu_objset_close(os);
-	if (error == ECKSUM)
-		return (0); /* normal end of chain */
-	return (error);
+	/*
+	 * Because tx == NULL, zil_claim_log_block() will not actually claim
+	 * any blocks, but just determine whether it is possible to do so.
+	 * In addition to checking the log chain, zil_claim_log_block()
+	 * will invoke zio_claim() with a done func of spa_claim_notify(),
+	 * which will update spa_max_claim_txg.  See spa_load() for details.
+	 */
+	error = zil_parse(zilog, zil_claim_log_block, zil_claim_log_record, tx,
+	    zilog->zl_header->zh_claim_txg ? -1ULL : spa_first_txg(os->os_spa));
+
+	dmu_objset_rele(os, FTAG);
+
+	return ((error == ECKSUM || error == ENOENT) ? 0 : error);
 }
 
 static int
@@ -615,7 +673,7 @@ zil_vdev_compare(const void *x1, const void *x2)
 }
 
 void
-zil_add_block(zilog_t *zilog, blkptr_t *bp)
+zil_add_block(zilog_t *zilog, const blkptr_t *bp)
 {
 	avl_tree_t *t = &zilog->zl_vdev_tree;
 	avl_index_t where;
@@ -691,9 +749,9 @@ zil_lwb_write_done(zio_t *zio)
 {
 	lwb_t *lwb = zio->io_private;
 	zilog_t *zilog = lwb->lwb_zilog;
+	dmu_tx_t *tx = lwb->lwb_tx;
 
 	ASSERT(BP_GET_COMPRESS(zio->io_bp) == ZIO_COMPRESS_OFF);
-	ASSERT(BP_GET_CHECKSUM(zio->io_bp) == ZIO_CHECKSUM_ZILOG);
 	ASSERT(BP_GET_TYPE(zio->io_bp) == DMU_OT_INTENT_LOG);
 	ASSERT(BP_GET_LEVEL(zio->io_bp) == 0);
 	ASSERT(BP_GET_BYTEORDER(zio->io_bp) == ZFS_HOST_BYTEORDER);
@@ -712,17 +770,15 @@ zil_lwb_write_done(zio_t *zio)
 	zio_buf_free(lwb->lwb_buf, lwb->lwb_sz);
 	mutex_enter(&zilog->zl_lock);
 	lwb->lwb_buf = NULL;
-	if (zio->io_error)
-		zilog->zl_log_error = B_TRUE;
+	lwb->lwb_tx = NULL;
+	mutex_exit(&zilog->zl_lock);
 
 	/*
 	 * Now that we've written this log block, we have a stable pointer
 	 * to the next block in the chain, so it's OK to let the txg in
-	 * which we allocated the next block sync. We still have the
-	 * zl_lock to ensure zil_sync doesn't kmem free the lwb.
+	 * which we allocated the next block sync.
 	 */
-	txg_rele_to_sync(&lwb->lwb_txgh);
-	mutex_exit(&zilog->zl_lock);
+	dmu_tx_commit(tx);
 }
 
 /*
@@ -733,10 +789,9 @@ zil_lwb_write_init(zilog_t *zilog, lwb_t *lwb)
 {
 	zbookmark_t zb;
 
-	zb.zb_objset = lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_OBJSET];
-	zb.zb_object = 0;
-	zb.zb_level = -1;
-	zb.zb_blkid = lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_SEQ];
+	SET_BOOKMARK(&zb, lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_OBJSET],
+	    ZB_ZIL_OBJECT, ZB_ZIL_LEVEL,
+	    lwb->lwb_blk.blk_cksum.zc_word[ZIL_ZC_SEQ]);
 
 	if (zilog->zl_root_zio == NULL) {
 		zilog->zl_root_zio = zio_root(zilog->zl_spa, NULL, NULL,
@@ -744,118 +799,147 @@ zil_lwb_write_init(zilog_t *zilog, lwb_t *lwb)
 	}
 	if (lwb->lwb_zio == NULL) {
 		lwb->lwb_zio = zio_rewrite(zilog->zl_root_zio, zilog->zl_spa,
-		    0, &lwb->lwb_blk, lwb->lwb_buf, lwb->lwb_sz,
+		    0, &lwb->lwb_blk, lwb->lwb_buf, BP_GET_LSIZE(&lwb->lwb_blk),
 		    zil_lwb_write_done, lwb, ZIO_PRIORITY_LOG_WRITE,
-		    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE, &zb);
+		    ZIO_FLAG_CANFAIL | ZIO_FLAG_DONT_PROPAGATE, &zb);
 	}
 }
 
 /*
+ * Define a limited set of intent log block sizes.
+ * These must be a multiple of 4KB. Note only the amount used (again
+ * aligned to 4KB) actually gets written. However, we can't always just
+ * allocate SPA_MAXBLOCKSIZE as the slog space could be exhausted.
+ */
+uint64_t zil_block_buckets[] = {
+    4096,		/* non TX_WRITE */
+    8192+4096,		/* data base */
+    32*1024 + 4096, 	/* NFS writes */
+    UINT64_MAX
+};
+
+/*
+ * Use the slog as long as the logbias is 'latency' and the current commit size
+ * is less than the limit or the total list size is less than 2X the limit.
+ * Limit checking is disabled by setting zil_slog_limit to UINT64_MAX.
+ */
+uint64_t zil_slog_limit = 1024 * 1024;
+#define	USE_SLOG(zilog) (((zilog)->zl_logbias == ZFS_LOGBIAS_LATENCY) && \
+	(((zilog)->zl_cur_used < zil_slog_limit) || \
+	((zilog)->zl_itx_list_sz < (zil_slog_limit << 1))))
+
+/*
  * Start a log block write and advance to the next log block.
  * Calls are serialized.
  */
 static lwb_t *
 zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb)
 {
-	lwb_t *nlwb;
-	zil_trailer_t *ztp = (zil_trailer_t *)(lwb->lwb_buf + lwb->lwb_sz) - 1;
+	lwb_t *nlwb = NULL;
+	zil_chain_t *zilc;
 	spa_t *spa = zilog->zl_spa;
-	blkptr_t *bp = &ztp->zit_next_blk;
+	blkptr_t *bp;
+	dmu_tx_t *tx;
 	uint64_t txg;
-	uint64_t zil_blksz;
-	int error;
+	uint64_t zil_blksz, wsz;
+	int i, error;
+
+	if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) {
+		zilc = (zil_chain_t *)lwb->lwb_buf;
+		bp = &zilc->zc_next_blk;
+	} else {
+		zilc = (zil_chain_t *)(lwb->lwb_buf + lwb->lwb_sz);
+		bp = &zilc->zc_next_blk;
+	}
 
-	ASSERT(lwb->lwb_nused <= ZIL_BLK_DATA_SZ(lwb));
+	ASSERT(lwb->lwb_nused <= lwb->lwb_sz);
 
 	/*
 	 * Allocate the next block and save its address in this block
 	 * before writing it in order to establish the log chain.
 	 * Note that if the allocation of nlwb synced before we wrote
 	 * the block that points at it (lwb), we'd leak it if we crashed.
-	 * Therefore, we don't do txg_rele_to_sync() until zil_lwb_write_done().
+	 * Therefore, we don't do dmu_tx_commit() until zil_lwb_write_done().
+	 * We dirty the dataset to ensure that zil_sync() will be called
+	 * to clean up in the event of allocation failure or I/O failure.
 	 */
-	txg = txg_hold_open(zilog->zl_dmu_pool, &lwb->lwb_txgh);
-	txg_rele_to_quiesce(&lwb->lwb_txgh);
+	tx = dmu_tx_create(zilog->zl_os);
+	VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0);
+	dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
+	txg = dmu_tx_get_txg(tx);
+
+	lwb->lwb_tx = tx;
 
 	/*
-	 * Pick a ZIL blocksize. We request a size that is the
-	 * maximum of the previous used size, the current used size and
-	 * the amount waiting in the queue.
+	 * Log blocks are pre-allocated. Here we select the size of the next
+	 * block, based on size used in the last block.
+	 * - first find the smallest bucket that will fit the block from a
+	 *   limited set of block sizes. This is because it's faster to write
+	 *   blocks allocated from the same metaslab as they are adjacent or
+	 *   close.
+	 * - next find the maximum from the new suggested size and an array of
+	 *   previous sizes. This lessens a picket fence effect of wrongly
+	 *   guesssing the size if we have a stream of say 2k, 64k, 2k, 64k
+	 *   requests.
+	 *
+	 * Note we only write what is used, but we can't just allocate
+	 * the maximum block size because we can exhaust the available
+	 * pool log space.
 	 */
-	zil_blksz = MAX(zilog->zl_prev_used,
-	    zilog->zl_cur_used + sizeof (*ztp));
-	zil_blksz = MAX(zil_blksz, zilog->zl_itx_list_sz + sizeof (*ztp));
-	zil_blksz = P2ROUNDUP_TYPED(zil_blksz, ZIL_MIN_BLKSZ, uint64_t);
-	if (zil_blksz > ZIL_MAX_BLKSZ)
-		zil_blksz = ZIL_MAX_BLKSZ;
+	zil_blksz = zilog->zl_cur_used + sizeof (zil_chain_t);
+	for (i = 0; zil_blksz > zil_block_buckets[i]; i++)
+		continue;
+	zil_blksz = zil_block_buckets[i];
+	if (zil_blksz == UINT64_MAX)
+		zil_blksz = SPA_MAXBLOCKSIZE;
+	zilog->zl_prev_blks[zilog->zl_prev_rotor] = zil_blksz;
+	for (i = 0; i < ZIL_PREV_BLKS; i++)
+		zil_blksz = MAX(zil_blksz, zilog->zl_prev_blks[i]);
+	zilog->zl_prev_rotor = (zilog->zl_prev_rotor + 1) & (ZIL_PREV_BLKS - 1);
 
 	BP_ZERO(bp);
 	/* pass the old blkptr in order to spread log blocks across devs */
-	error = zio_alloc_blk(spa, zil_blksz, bp, &lwb->lwb_blk, txg);
-	if (error) {
-		dmu_tx_t *tx = dmu_tx_create_assigned(zilog->zl_dmu_pool, txg);
+	error = zio_alloc_zil(spa, txg, bp, &lwb->lwb_blk, zil_blksz,
+	    USE_SLOG(zilog));
+	if (!error) {
+		ASSERT3U(bp->blk_birth, ==, txg);
+		bp->blk_cksum = lwb->lwb_blk.blk_cksum;
+		bp->blk_cksum.zc_word[ZIL_ZC_SEQ]++;
 
 		/*
-		 * We dirty the dataset to ensure that zil_sync() will
-		 * be called to remove this lwb from our zl_lwb_list.
-		 * Failing to do so, may leave an lwb with a NULL lwb_buf
-		 * hanging around on the zl_lwb_list.
+		 * Allocate a new log write buffer (lwb).
 		 */
-		dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
-		dmu_tx_commit(tx);
-
-		/*
-		 * Since we've just experienced an allocation failure so we
-		 * terminate the current lwb and send it on its way.
-		 */
-		ztp->zit_pad = 0;
-		ztp->zit_nused = lwb->lwb_nused;
-		ztp->zit_bt.zbt_cksum = lwb->lwb_blk.blk_cksum;
-		zio_nowait(lwb->lwb_zio);
+		nlwb = zil_alloc_lwb(zilog, bp, txg);
 
-		/*
-		 * By returning NULL the caller will call tx_wait_synced()
-		 */
-		return (NULL);
+		/* Record the block for later vdev flushing */
+		zil_add_block(zilog, &lwb->lwb_blk);
 	}
 
-	ASSERT3U(bp->blk_birth, ==, txg);
-	ztp->zit_pad = 0;
-	ztp->zit_nused = lwb->lwb_nused;
-	ztp->zit_bt.zbt_cksum = lwb->lwb_blk.blk_cksum;
-	bp->blk_cksum = lwb->lwb_blk.blk_cksum;
-	bp->blk_cksum.zc_word[ZIL_ZC_SEQ]++;
+	if (BP_GET_CHECKSUM(&lwb->lwb_blk) == ZIO_CHECKSUM_ZILOG2) {
+		/* For Slim ZIL only write what is used. */
+		wsz = P2ROUNDUP_TYPED(lwb->lwb_nused, ZIL_MIN_BLKSZ, uint64_t);
+		ASSERT3U(wsz, <=, lwb->lwb_sz);
+		zio_shrink(lwb->lwb_zio, wsz);
 
-	/*
-	 * Allocate a new log write buffer (lwb).
-	 */
-	nlwb = kmem_cache_alloc(zil_lwb_cache, KM_SLEEP);
+	} else {
+		wsz = lwb->lwb_sz;
+	}
 
-	nlwb->lwb_zilog = zilog;
-	nlwb->lwb_blk = *bp;
-	nlwb->lwb_nused = 0;
-	nlwb->lwb_sz = BP_GET_LSIZE(&nlwb->lwb_blk);
-	nlwb->lwb_buf = zio_buf_alloc(nlwb->lwb_sz);
-	nlwb->lwb_max_txg = txg;
-	nlwb->lwb_zio = NULL;
+	zilc->zc_pad = 0;
+	zilc->zc_nused = lwb->lwb_nused;
+	zilc->zc_eck.zec_cksum = lwb->lwb_blk.blk_cksum;
 
 	/*
-	 * Put new lwb at the end of the log chain
+	 * clear unused data for security
 	 */
-	mutex_enter(&zilog->zl_lock);
-	list_insert_tail(&zilog->zl_lwb_list, nlwb);
-	mutex_exit(&zilog->zl_lock);
+	bzero(lwb->lwb_buf + lwb->lwb_nused, wsz - lwb->lwb_nused);
 
-	/* Record the block for later vdev flushing */
-	zil_add_block(zilog, &lwb->lwb_blk);
+	zio_nowait(lwb->lwb_zio); /* Kick off the write for the old log block */
 
 	/*
-	 * kick off the write for the old log block
+	 * If there was an allocation failure then nlwb will be null which
+	 * forces a txg_wait_synced().
 	 */
-	dprintf_bp(&lwb->lwb_blk, "lwb %p txg %llu: ", lwb, txg);
-	ASSERT(lwb->lwb_zio);
-	zio_nowait(lwb->lwb_zio);
-
 	return (nlwb);
 }
 
@@ -863,20 +947,20 @@ static lwb_t *
 zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
 {
 	lr_t *lrc = &itx->itx_lr; /* common log record */
-	lr_write_t *lr = (lr_write_t *)lrc;
+	lr_write_t *lrw = (lr_write_t *)lrc;
+	char *lr_buf;
 	uint64_t txg = lrc->lrc_txg;
 	uint64_t reclen = lrc->lrc_reclen;
-	uint64_t dlen;
+	uint64_t dlen = 0;
 
 	if (lwb == NULL)
 		return (NULL);
+
 	ASSERT(lwb->lwb_buf != NULL);
 
 	if (lrc->lrc_txtype == TX_WRITE && itx->itx_wr_state == WR_NEED_COPY)
 		dlen = P2ROUNDUP_TYPED(
-		    lr->lr_length, sizeof (uint64_t), uint64_t);
-	else
-		dlen = 0;
+		    lrw->lr_length, sizeof (uint64_t), uint64_t);
 
 	zilog->zl_cur_used += (reclen + dlen);
 
@@ -885,24 +969,22 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
 	/*
 	 * If this record won't fit in the current log block, start a new one.
 	 */
-	if (lwb->lwb_nused + reclen + dlen > ZIL_BLK_DATA_SZ(lwb)) {
+	if (lwb->lwb_nused + reclen + dlen > lwb->lwb_sz) {
 		lwb = zil_lwb_write_start(zilog, lwb);
 		if (lwb == NULL)
 			return (NULL);
 		zil_lwb_write_init(zilog, lwb);
-		ASSERT(lwb->lwb_nused == 0);
-		if (reclen + dlen > ZIL_BLK_DATA_SZ(lwb)) {
+		ASSERT(LWB_EMPTY(lwb));
+		if (lwb->lwb_nused + reclen + dlen > lwb->lwb_sz) {
 			txg_wait_synced(zilog->zl_dmu_pool, txg);
 			return (lwb);
 		}
 	}
 
-	/*
-	 * Update the lrc_seq, to be log record sequence number. See zil.h
-	 * Then copy the record to the log buffer.
-	 */
-	lrc->lrc_seq = ++zilog->zl_lr_seq; /* we are single threaded */
-	bcopy(lrc, lwb->lwb_buf + lwb->lwb_nused, reclen);
+	lr_buf = lwb->lwb_buf + lwb->lwb_nused;
+	bcopy(lrc, lr_buf, reclen);
+	lrc = (lr_t *)lr_buf;
+	lrw = (lr_write_t *)lrc;
 
 	/*
 	 * If it's a write, fetch the data or get its blkptr as appropriate.
@@ -914,18 +996,16 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
 			char *dbuf;
 			int error;
 
-			/* alignment is guaranteed */
-			lr = (lr_write_t *)(lwb->lwb_buf + lwb->lwb_nused);
 			if (dlen) {
 				ASSERT(itx->itx_wr_state == WR_NEED_COPY);
-				dbuf = lwb->lwb_buf + lwb->lwb_nused + reclen;
-				lr->lr_common.lrc_reclen += dlen;
+				dbuf = lr_buf + reclen;
+				lrw->lr_common.lrc_reclen += dlen;
 			} else {
 				ASSERT(itx->itx_wr_state == WR_INDIRECT);
 				dbuf = NULL;
 			}
 			error = zilog->zl_get_data(
-			    itx->itx_private, lr, dbuf, lwb->lwb_zio);
+			    itx->itx_private, lrw, dbuf, lwb->lwb_zio);
 			if (error == EIO) {
 				txg_wait_synced(zilog->zl_dmu_pool, txg);
 				return (lwb);
@@ -938,9 +1018,16 @@ zil_lwb_commit(zilog_t *zilog, itx_t *itx, lwb_t *lwb)
 		}
 	}
 
+	/*
+	 * We're actually making an entry, so update lrc_seq to be the
+	 * log record sequence number.  Note that this is generally not
+	 * equal to the itx sequence number because not all transactions
+	 * are synchronous, and sometimes spa_sync() gets there first.
+	 */
+	lrc->lrc_seq = ++zilog->zl_lr_seq; /* we are single threaded */
 	lwb->lwb_nused += reclen + dlen;
 	lwb->lwb_max_txg = MAX(lwb->lwb_max_txg, txg);
-	ASSERT3U(lwb->lwb_nused, <=, ZIL_BLK_DATA_SZ(lwb));
+	ASSERT3U(lwb->lwb_nused, <=, lwb->lwb_sz);
 	ASSERT3U(P2PHASE(lwb->lwb_nused, sizeof (uint64_t)), ==, 0);
 
 	return (lwb);
@@ -962,12 +1049,19 @@ zil_itx_create(uint64_t txtype, size_t lrsize)
 	return (itx);
 }
 
+void
+zil_itx_destroy(itx_t *itx)
+{
+	kmem_free(itx, offsetof(itx_t, itx_lr) + itx->itx_lr.lrc_reclen);
+}
+
 uint64_t
 zil_itx_assign(zilog_t *zilog, itx_t *itx, dmu_tx_t *tx)
 {
 	uint64_t seq;
 
 	ASSERT(itx->itx_lr.lrc_seq == 0);
+	ASSERT(!zilog->zl_replay);
 
 	mutex_enter(&zilog->zl_lock);
 	list_insert_tail(&zilog->zl_itx_list, itx);
@@ -1016,8 +1110,7 @@ zil_itx_clean(zilog_t *zilog)
 	/* destroy sync'd log transactions */
 	while ((itx = list_head(&clean_list)) != NULL) {
 		list_remove(&clean_list, itx);
-		kmem_free(itx, offsetof(itx_t, itx_lr)
-		    + itx->itx_lr.lrc_reclen);
+		zil_itx_destroy(itx);
 	}
 	list_destroy(&clean_list);
 }
@@ -1036,7 +1129,7 @@ zil_clean(zilog_t *zilog)
 	if ((itx != NULL) &&
 	    (itx->itx_lr.lrc_txg <= spa_last_synced_txg(zilog->zl_spa))) {
 		(void) taskq_dispatch(zilog->zl_clean_taskq,
-		    (task_func_t *)zil_itx_clean, zilog, TQ_SLEEP);
+		    (task_func_t *)zil_itx_clean, zilog, TQ_NOSLEEP);
 	}
 	mutex_exit(&zilog->zl_lock);
 }
@@ -1046,9 +1139,10 @@ zil_commit_writer(zilog_t *zilog, uint64_t seq, uint64_t foid)
 {
 	uint64_t txg;
 	uint64_t commit_seq = 0;
-	itx_t *itx, *itx_next = (itx_t *)-1;
+	itx_t *itx, *itx_next;
 	lwb_t *lwb;
 	spa_t *spa;
+	int error = 0;
 
 	zilog->zl_writer = B_TRUE;
 	ASSERT(zilog->zl_root_zio == NULL);
@@ -1068,77 +1162,64 @@ zil_commit_writer(zilog_t *zilog, uint64_t seq, uint64_t foid)
 				return;
 			}
 			mutex_exit(&zilog->zl_lock);
-			zil_create(zilog);
+			lwb = zil_create(zilog);
 			mutex_enter(&zilog->zl_lock);
-			lwb = list_tail(&zilog->zl_lwb_list);
 		}
 	}
+	ASSERT(lwb == NULL || lwb->lwb_zio == NULL);
 
 	/* Loop through in-memory log transactions filling log blocks. */
 	DTRACE_PROBE1(zil__cw1, zilog_t *, zilog);
-	for (;;) {
+
+	for (itx = list_head(&zilog->zl_itx_list); itx; itx = itx_next) {
 		/*
-		 * Find the next itx to push:
-		 * Push all transactions related to specified foid and all
-		 * other transactions except TX_WRITE, TX_TRUNCATE,
-		 * TX_SETATTR and TX_ACL for all other files.
+		 * Save the next pointer.  Even though we drop zl_lock below,
+		 * all threads that can remove itx list entries (other writers
+		 * and zil_itx_clean()) can't do so until they have zl_writer.
 		 */
-		if (itx_next != (itx_t *)-1)
-			itx = itx_next;
-		else
-			itx = list_head(&zilog->zl_itx_list);
-		for (; itx != NULL; itx = list_next(&zilog->zl_itx_list, itx)) {
-			if (foid == 0) /* push all foids? */
-				break;
-			if (itx->itx_sync) /* push all O_[D]SYNC */
-				break;
-			switch (itx->itx_lr.lrc_txtype) {
-			case TX_SETATTR:
-			case TX_WRITE:
-			case TX_TRUNCATE:
-			case TX_ACL:
-				/* lr_foid is same offset for these records */
-				if (((lr_write_t *)&itx->itx_lr)->lr_foid
-				    != foid) {
-					continue; /* skip this record */
-				}
-			}
-			break;
-		}
-		if (itx == NULL)
-			break;
+		itx_next = list_next(&zilog->zl_itx_list, itx);
+
+		/*
+		 * Determine whether to push this itx.
+		 * Push all transactions related to specified foid and
+		 * all other transactions except those that can be logged
+		 * out of order (TX_WRITE, TX_TRUNCATE, TX_SETATTR, TX_ACL)
+		 * for all other files.
+		 *
+		 * If foid == 0 (meaning "push all foids") or
+		 * itx->itx_sync is set (meaning O_[D]SYNC), push regardless.
+		 */
+		if (foid != 0 && !itx->itx_sync &&
+		    TX_OOO(itx->itx_lr.lrc_txtype) &&
+		    ((lr_ooo_t *)&itx->itx_lr)->lr_foid != foid)
+			continue; /* skip this record */
 
 		if ((itx->itx_lr.lrc_seq > seq) &&
-		    ((lwb == NULL) || (lwb->lwb_nused == 0) ||
-		    (lwb->lwb_nused + itx->itx_sod > ZIL_BLK_DATA_SZ(lwb)))) {
+		    ((lwb == NULL) || (LWB_EMPTY(lwb)) ||
+		    (lwb->lwb_nused + itx->itx_sod > lwb->lwb_sz)))
 			break;
-		}
 
-		/*
-		 * Save the next pointer.  Even though we soon drop
-		 * zl_lock all threads that may change the list
-		 * (another writer or zil_itx_clean) can't do so until
-		 * they have zl_writer.
-		 */
-		itx_next = list_next(&zilog->zl_itx_list, itx);
 		list_remove(&zilog->zl_itx_list, itx);
 		zilog->zl_itx_list_sz -= itx->itx_sod;
+
 		mutex_exit(&zilog->zl_lock);
+
 		txg = itx->itx_lr.lrc_txg;
 		ASSERT(txg);
 
 		if (txg > spa_last_synced_txg(spa) ||
 		    txg > spa_freeze_txg(spa))
 			lwb = zil_lwb_commit(zilog, itx, lwb);
-		kmem_free(itx, offsetof(itx_t, itx_lr)
-		    + itx->itx_lr.lrc_reclen);
+
+		zil_itx_destroy(itx);
+
 		mutex_enter(&zilog->zl_lock);
 	}
 	DTRACE_PROBE1(zil__cw2, zilog_t *, zilog);
 	/* determine commit sequence number */
 	itx = list_head(&zilog->zl_itx_list);
 	if (itx)
-		commit_seq = itx->itx_lr.lrc_seq;
+		commit_seq = itx->itx_lr.lrc_seq - 1;
 	else
 		commit_seq = zilog->zl_itx_seq;
 	mutex_exit(&zilog->zl_lock);
@@ -1155,22 +1236,28 @@ zil_commit_writer(zilog_t *zilog, uint64_t seq, uint64_t foid)
 	 */
 	if (zilog->zl_root_zio) {
 		DTRACE_PROBE1(zil__cw3, zilog_t *, zilog);
-		(void) zio_wait(zilog->zl_root_zio);
+		error = zio_wait(zilog->zl_root_zio);
 		zilog->zl_root_zio = NULL;
 		DTRACE_PROBE1(zil__cw4, zilog_t *, zilog);
 		zil_flush_vdevs(zilog);
 	}
 
-	if (zilog->zl_log_error || lwb == NULL) {
-		zilog->zl_log_error = 0;
+	if (error || lwb == NULL)
 		txg_wait_synced(zilog->zl_dmu_pool, 0);
-	}
 
 	mutex_enter(&zilog->zl_lock);
 	zilog->zl_writer = B_FALSE;
 
 	ASSERT3U(commit_seq, >=, zilog->zl_commit_seq);
 	zilog->zl_commit_seq = commit_seq;
+
+	/*
+	 * Remember the highest committed log sequence number for ztest.
+	 * We only update this value when all the log writes succeeded,
+	 * because ztest wants to ASSERT that it got the whole log chain.
+	 */
+	if (error == 0 && lwb != NULL)
+		zilog->zl_commit_lr_seq = zilog->zl_lr_seq;
 }
 
 /*
@@ -1181,7 +1268,7 @@ zil_commit_writer(zilog_t *zilog, uint64_t seq, uint64_t foid)
 void
 zil_commit(zilog_t *zilog, uint64_t seq, uint64_t foid)
 {
-	if (zilog == NULL || seq == 0)
+	if (zilog->zl_sync == ZFS_SYNC_DISABLED || seq == 0)
 		return;
 
 	mutex_enter(&zilog->zl_lock);
@@ -1190,7 +1277,7 @@ zil_commit(zilog_t *zilog, uint64_t seq, uint64_t foid)
 
 	while (zilog->zl_writer) {
 		cv_wait(&zilog->zl_cv_writer, &zilog->zl_lock);
-		if (seq < zilog->zl_commit_seq) {
+		if (seq <= zilog->zl_commit_seq) {
 			mutex_exit(&zilog->zl_lock);
 			return;
 		}
@@ -1202,6 +1289,33 @@ zil_commit(zilog_t *zilog, uint64_t seq, uint64_t foid)
 }
 
 /*
+ * Report whether all transactions are committed.
+ */
+static boolean_t
+zil_is_committed(zilog_t *zilog)
+{
+	lwb_t *lwb;
+	boolean_t committed;
+
+	mutex_enter(&zilog->zl_lock);
+
+	while (zilog->zl_writer)
+		cv_wait(&zilog->zl_cv_writer, &zilog->zl_lock);
+
+	if (!list_is_empty(&zilog->zl_itx_list))
+		committed = B_FALSE;		/* unpushed transactions */
+	else if ((lwb = list_head(&zilog->zl_lwb_list)) == NULL)
+		committed = B_TRUE;		/* intent log never used */
+	else if (list_next(&zilog->zl_lwb_list, lwb) != NULL)
+		committed = B_FALSE;		/* zil_sync() not done yet */
+	else
+		committed = B_TRUE;		/* everything synced */
+
+	mutex_exit(&zilog->zl_lock);
+	return (committed);
+}
+
+/*
  * Called in syncing context to free committed log blocks and update log header.
  */
 void
@@ -1210,6 +1324,7 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx)
 	zil_header_t *zh = zil_header_in_syncing_context(zilog);
 	uint64_t txg = dmu_tx_get_txg(tx);
 	spa_t *spa = zilog->zl_spa;
+	uint64_t *replayed_seq = &zilog->zl_replayed_seq[txg & TXG_MASK];
 	lwb_t *lwb;
 
 	/*
@@ -1223,7 +1338,11 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx)
 
 	ASSERT(zilog->zl_stop_sync == 0);
 
-	zh->zh_replay_seq = zilog->zl_replayed_seq[txg & TXG_MASK];
+	if (*replayed_seq != 0) {
+		ASSERT(zh->zh_replay_seq < *replayed_seq);
+		zh->zh_replay_seq = *replayed_seq;
+		*replayed_seq = 0;
+	}
 
 	if (zilog->zl_destroy_txg == txg) {
 		blkptr_t blk = zh->zh_log;
@@ -1252,7 +1371,7 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx)
 		if (lwb->lwb_buf != NULL || lwb->lwb_max_txg > txg)
 			break;
 		list_remove(&zilog->zl_lwb_list, lwb);
-		zio_free_blk(spa, &lwb->lwb_blk, txg);
+		zio_free_zil(spa, txg, &lwb->lwb_blk);
 		kmem_cache_free(zil_lwb_cache, lwb);
 
 		/*
@@ -1280,6 +1399,18 @@ zil_fini(void)
 	kmem_cache_destroy(zil_lwb_cache);
 }
 
+void
+zil_set_sync(zilog_t *zilog, uint64_t sync)
+{
+	zilog->zl_sync = sync;
+}
+
+void
+zil_set_logbias(zilog_t *zilog, uint64_t logbias)
+{
+	zilog->zl_logbias = logbias;
+}
+
 zilog_t *
 zil_alloc(objset_t *os, zil_header_t *zh_phys)
 {
@@ -1292,6 +1423,8 @@ zil_alloc(objset_t *os, zil_header_t *zh_phys)
 	zilog->zl_spa = dmu_objset_spa(os);
 	zilog->zl_dmu_pool = dmu_objset_pool(os);
 	zilog->zl_destroy_txg = TXG_INITIAL - 1;
+	zilog->zl_logbias = dmu_objset_logbias(os);
+	zilog->zl_sync = dmu_objset_syncprop(os);
 
 	mutex_init(&zilog->zl_lock, NULL, MUTEX_DEFAULT, NULL);
 
@@ -1368,7 +1501,7 @@ zil_close(zilog_t *zilog)
 	if (!zil_is_committed(zilog)) {
 		uint64_t txg;
 		dmu_tx_t *tx = dmu_tx_create(zilog->zl_os);
-		(void) dmu_tx_assign(tx, TXG_WAIT);
+		VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0);
 		dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
 		txg = dmu_tx_get_txg(tx);
 		dmu_tx_commit(tx);
@@ -1442,88 +1575,88 @@ zil_resume(zilog_t *zilog)
 }
 
 typedef struct zil_replay_arg {
-	objset_t	*zr_os;
 	zil_replay_func_t **zr_replay;
 	void		*zr_arg;
 	boolean_t	zr_byteswap;
-	char		*zr_lrbuf;
+	char		*zr_lr;
 } zil_replay_arg_t;
 
-static void
+static int
+zil_replay_error(zilog_t *zilog, lr_t *lr, int error)
+{
+	char name[MAXNAMELEN];
+
+	zilog->zl_replaying_seq--;	/* didn't actually replay this one */
+
+	dmu_objset_name(zilog->zl_os, name);
+
+	cmn_err(CE_WARN, "ZFS replay transaction error %d, "
+	    "dataset %s, seq 0x%llx, txtype %llu %s\n", error, name,
+	    (u_longlong_t)lr->lrc_seq,
+	    (u_longlong_t)(lr->lrc_txtype & ~TX_CI),
+	    (lr->lrc_txtype & TX_CI) ? "CI" : "");
+
+	return (error);
+}
+
+static int
 zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
 {
 	zil_replay_arg_t *zr = zra;
 	const zil_header_t *zh = zilog->zl_header;
 	uint64_t reclen = lr->lrc_reclen;
 	uint64_t txtype = lr->lrc_txtype;
-	char *name;
-	int pass, error;
-
-	if (!zilog->zl_replay)			/* giving up */
-		return;
+	int error = 0;
 
-	if (lr->lrc_txg < claim_txg)		/* already committed */
-		return;
+	zilog->zl_replaying_seq = lr->lrc_seq;
 
 	if (lr->lrc_seq <= zh->zh_replay_seq)	/* already replayed */
-		return;
+		return (0);
+
+	if (lr->lrc_txg < claim_txg)		/* already committed */
+		return (0);
 
 	/* Strip case-insensitive bit, still present in log record */
 	txtype &= ~TX_CI;
 
-	if (txtype == 0 || txtype >= TX_MAX_TYPE) {
-		error = EINVAL;
-		goto bad;
+	if (txtype == 0 || txtype >= TX_MAX_TYPE)
+		return (zil_replay_error(zilog, lr, EINVAL));
+
+	/*
+	 * If this record type can be logged out of order, the object
+	 * (lr_foid) may no longer exist.  That's legitimate, not an error.
+	 */
+	if (TX_OOO(txtype)) {
+		error = dmu_object_info(zilog->zl_os,
+		    ((lr_ooo_t *)lr)->lr_foid, NULL);
+		if (error == ENOENT || error == EEXIST)
+			return (0);
 	}
 
 	/*
 	 * Make a copy of the data so we can revise and extend it.
 	 */
-	bcopy(lr, zr->zr_lrbuf, reclen);
+	bcopy(lr, zr->zr_lr, reclen);
+
+	/*
+	 * If this is a TX_WRITE with a blkptr, suck in the data.
+	 */
+	if (txtype == TX_WRITE && reclen == sizeof (lr_write_t)) {
+		error = zil_read_log_data(zilog, (lr_write_t *)lr,
+		    zr->zr_lr + reclen);
+		if (error)
+			return (zil_replay_error(zilog, lr, error));
+	}
 
 	/*
 	 * The log block containing this lr may have been byteswapped
 	 * so that we can easily examine common fields like lrc_txtype.
-	 * However, the log is a mix of different data types, and only the
+	 * However, the log is a mix of different record types, and only the
 	 * replay vectors know how to byteswap their records.  Therefore, if
 	 * the lr was byteswapped, undo it before invoking the replay vector.
 	 */
 	if (zr->zr_byteswap)
-		byteswap_uint64_array(zr->zr_lrbuf, reclen);
-
-	/*
-	 * If this is a TX_WRITE with a blkptr, suck in the data.
-	 */
-	if (txtype == TX_WRITE && reclen == sizeof (lr_write_t)) {
-		lr_write_t *lrw = (lr_write_t *)lr;
-		blkptr_t *wbp = &lrw->lr_blkptr;
-		uint64_t wlen = lrw->lr_length;
-		char *wbuf = zr->zr_lrbuf + reclen;
-
-		if (BP_IS_HOLE(wbp)) {	/* compressed to a hole */
-			bzero(wbuf, wlen);
-		} else {
-			/*
-			 * A subsequent write may have overwritten this block,
-			 * in which case wbp may have been been freed and
-			 * reallocated, and our read of wbp may fail with a
-			 * checksum error.  We can safely ignore this because
-			 * the later write will provide the correct data.
-			 */
-			zbookmark_t zb;
-
-			zb.zb_objset = dmu_objset_id(zilog->zl_os);
-			zb.zb_object = lrw->lr_foid;
-			zb.zb_level = -1;
-			zb.zb_blkid = lrw->lr_offset / BP_GET_LSIZE(wbp);
-
-			(void) zio_wait(zio_read(NULL, zilog->zl_spa,
-			    wbp, wbuf, BP_GET_LSIZE(wbp), NULL, NULL,
-			    ZIO_PRIORITY_SYNC_READ,
-			    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE, &zb));
-			(void) memmove(wbuf, wbuf + lrw->lr_blkoff, wlen);
-		}
-	}
+		byteswap_uint64_array(zr->zr_lr, reclen);
 
 	/*
 	 * We must now do two things atomically: replay this log record,
@@ -1531,42 +1664,30 @@ zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
 	 * we did so. At the end of each replay function the sequence number
 	 * is updated if we are in replay mode.
 	 */
-	for (pass = 1; pass <= 2; pass++) {
-		zilog->zl_replaying_seq = lr->lrc_seq;
-		/* Only byteswap (if needed) on the 1st pass.  */
-		error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lrbuf,
-		    zr->zr_byteswap && pass == 1);
-
-		if (!error)
-			return;
-
+	error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lr, zr->zr_byteswap);
+	if (error) {
 		/*
 		 * The DMU's dnode layer doesn't see removes until the txg
 		 * commits, so a subsequent claim can spuriously fail with
 		 * EEXIST. So if we receive any error we try syncing out
-		 * any removes then retry the transaction.
+		 * any removes then retry the transaction.  Note that we
+		 * specify B_FALSE for byteswap now, so we don't do it twice.
 		 */
-		if (pass == 1)
-			txg_wait_synced(spa_get_dsl(zilog->zl_spa), 0);
+		txg_wait_synced(spa_get_dsl(zilog->zl_spa), 0);
+		error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lr, B_FALSE);
+		if (error)
+			return (zil_replay_error(zilog, lr, error));
 	}
-
-bad:
-	ASSERT(error);
-	name = kmem_alloc(MAXNAMELEN, KM_SLEEP);
-	dmu_objset_name(zr->zr_os, name);
-	cmn_err(CE_WARN, "ZFS replay transaction error %d, "
-	    "dataset %s, seq 0x%llx, txtype %llu %s\n",
-	    error, name, (u_longlong_t)lr->lrc_seq, (u_longlong_t)txtype,
-	    (lr->lrc_txtype & TX_CI) ? "CI" : "");
-	zilog->zl_replay = B_FALSE;
-	kmem_free(name, MAXNAMELEN);
+	return (0);
 }
 
 /* ARGSUSED */
-static void
+static int
 zil_incr_blks(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
 {
 	zilog->zl_replay_blks++;
+
+	return (0);
 }
 
 /*
@@ -1584,11 +1705,10 @@ zil_replay(objset_t *os, void *arg, zil_replay_func_t *replay_func[TX_MAX_TYPE])
 		return;
 	}
 
-	zr.zr_os = os;
 	zr.zr_replay = replay_func;
 	zr.zr_arg = arg;
 	zr.zr_byteswap = BP_SHOULD_BYTESWAP(&zh->zh_log);
-	zr.zr_lrbuf = kmem_alloc(2 * SPA_MAXBLOCKSIZE, KM_SLEEP);
+	zr.zr_lr = kmem_alloc(2 * SPA_MAXBLOCKSIZE, KM_SLEEP);
 
 	/*
 	 * Wait for in-progress removes to sync before starting replay.
@@ -1596,69 +1716,42 @@ zil_replay(objset_t *os, void *arg, zil_replay_func_t *replay_func[TX_MAX_TYPE])
 	txg_wait_synced(zilog->zl_dmu_pool, 0);
 
 	zilog->zl_replay = B_TRUE;
-	zilog->zl_replay_time = lbolt;
+	zilog->zl_replay_time = ddi_get_lbolt();
 	ASSERT(zilog->zl_replay_blks == 0);
 	(void) zil_parse(zilog, zil_incr_blks, zil_replay_log_record, &zr,
 	    zh->zh_claim_txg);
-	kmem_free(zr.zr_lrbuf, 2 * SPA_MAXBLOCKSIZE);
+	kmem_free(zr.zr_lr, 2 * SPA_MAXBLOCKSIZE);
 
 	zil_destroy(zilog, B_FALSE);
 	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
 	zilog->zl_replay = B_FALSE;
 }
 
-/*
- * Report whether all transactions are committed
- */
-int
-zil_is_committed(zilog_t *zilog)
+boolean_t
+zil_replaying(zilog_t *zilog, dmu_tx_t *tx)
 {
-	lwb_t *lwb;
-	int ret;
-
-	mutex_enter(&zilog->zl_lock);
-	while (zilog->zl_writer)
-		cv_wait(&zilog->zl_cv_writer, &zilog->zl_lock);
-
-	/* recent unpushed intent log transactions? */
-	if (!list_is_empty(&zilog->zl_itx_list)) {
-		ret = B_FALSE;
-		goto out;
-	}
-
-	/* intent log never used? */
-	lwb = list_head(&zilog->zl_lwb_list);
-	if (lwb == NULL) {
-		ret = B_TRUE;
-		goto out;
-	}
+	if (zilog->zl_sync == ZFS_SYNC_DISABLED)
+		return (B_TRUE);
 
-	/*
-	 * more than 1 log buffer means zil_sync() hasn't yet freed
-	 * entries after a txg has committed
-	 */
-	if (list_next(&zilog->zl_lwb_list, lwb)) {
-		ret = B_FALSE;
-		goto out;
+	if (zilog->zl_replay) {
+		dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx);
+		zilog->zl_replayed_seq[dmu_tx_get_txg(tx) & TXG_MASK] =
+		    zilog->zl_replaying_seq;
+		return (B_TRUE);
 	}
 
-	ASSERT(zil_empty(zilog));
-	ret = B_TRUE;
-out:
-	cv_broadcast(&zilog->zl_cv_writer);
-	mutex_exit(&zilog->zl_lock);
-	return (ret);
+	return (B_FALSE);
 }
 
 /* ARGSUSED */
 int
-zil_vdev_offline(char *osname, void *arg)
+zil_vdev_offline(const char *osname, void *arg)
 {
 	objset_t *os;
 	zilog_t *zilog;
 	int error;
 
-	error = dmu_objset_open(osname, DMU_OST_ANY, DS_MODE_USER, &os);
+	error = dmu_objset_hold(osname, FTAG, &os);
 	if (error)
 		return (error);
 
@@ -1667,6 +1760,6 @@ zil_vdev_offline(char *osname, void *arg)
 		error = EEXIST;
 	else
 		zil_resume(zilog);
-	dmu_objset_close(os);
+	dmu_objset_rele(os, FTAG);
 	return (error);
 }