Merge commit 'refs/top-bases/fix-clock-wrap' into fix-clock-wrap

39 files changed, 1094 insertions, 604 deletions

diff --git a/module/zfs/arc.c b/module/zfs/arc.c
index d59dfe2d9..dd9f914b3 100644
--- a/module/zfs/arc.c
+++ b/module/zfs/arc.c
@@ -3491,6 +3491,7 @@ arc_fini(void)
 	mutex_destroy(&arc_mru_ghost->arcs_mtx);
 	mutex_destroy(&arc_mfu->arcs_mtx);
 	mutex_destroy(&arc_mfu_ghost->arcs_mtx);
+	mutex_destroy(&arc_l2c_only->arcs_mtx);
 
 	mutex_destroy(&zfs_write_limit_lock);
 
@@ -4457,7 +4458,7 @@ l2arc_fini(void)
 void
 l2arc_start(void)
 {
-	if (!(spa_mode & FWRITE))
+	if (!(spa_mode_global & FWRITE))
 		return;
 
 	(void) thread_create(NULL, 0, l2arc_feed_thread, NULL, 0, &p0,
@@ -4467,7 +4468,7 @@ l2arc_start(void)
 void
 l2arc_stop(void)
 {
-	if (!(spa_mode & FWRITE))
+	if (!(spa_mode_global & FWRITE))
 		return;
 
 	mutex_enter(&l2arc_feed_thr_lock);
diff --git a/module/zfs/dmu_traverse.c b/module/zfs/dmu_traverse.c
index 512401470..197284e1e 100644
--- a/module/zfs/dmu_traverse.c
+++ b/module/zfs/dmu_traverse.c
@@ -119,7 +119,7 @@ traverse_zil(struct traverse_data *td, zil_header_t *zh)
 	 * We only want to visit blocks that have been claimed but not yet
 	 * replayed (or, in read-only mode, blocks that *would* be claimed).
 	 */
-	if (claim_txg == 0 && (spa_mode & FWRITE))
+	if (claim_txg == 0 && spa_writeable(td->td_spa))
 		return;
 
 	zilog = zil_alloc(spa_get_dsl(td->td_spa)->dp_meta_objset, zh);
diff --git a/module/zfs/dnode.c b/module/zfs/dnode.c
index e77834d60..8686ab983 100644
--- a/module/zfs/dnode.c
+++ b/module/zfs/dnode.c
@@ -56,6 +56,8 @@ dnode_cons(void *arg, void *unused, int kmflag)
 	rw_init(&dn->dn_struct_rwlock, NULL, RW_DEFAULT, NULL);
 	mutex_init(&dn->dn_mtx, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&dn->dn_dbufs_mtx, NULL, MUTEX_DEFAULT, NULL);
+	cv_init(&dn->dn_notxholds, NULL, CV_DEFAULT, NULL);
+
 	refcount_create(&dn->dn_holds);
 	refcount_create(&dn->dn_tx_holds);
 
@@ -84,6 +86,7 @@ dnode_dest(void *arg, void *unused)
 	rw_destroy(&dn->dn_struct_rwlock);
 	mutex_destroy(&dn->dn_mtx);
 	mutex_destroy(&dn->dn_dbufs_mtx);
+	cv_destroy(&dn->dn_notxholds);
 	refcount_destroy(&dn->dn_holds);
 	refcount_destroy(&dn->dn_tx_holds);
 
diff --git a/module/zfs/dsl_dataset.c b/module/zfs/dsl_dataset.c
index 93ea8aa11..e488b2bdd 100644
--- a/module/zfs/dsl_dataset.c
+++ b/module/zfs/dsl_dataset.c
@@ -1948,6 +1948,9 @@ dsl_dataset_fast_stat(dsl_dataset_t *ds, dmu_objset_stats_t *stat)
 	if (ds->ds_phys->ds_next_snap_obj) {
 		stat->dds_is_snapshot = B_TRUE;
 		stat->dds_num_clones = ds->ds_phys->ds_num_children - 1;
+	} else {
+		stat->dds_is_snapshot = B_FALSE;
+		stat->dds_num_clones = 0;
 	}
 
 	/* clone origin is really a dsl_dir thing... */
@@ -1959,6 +1962,8 @@ dsl_dataset_fast_stat(dsl_dataset_t *ds, dmu_objset_stats_t *stat)
 		    ds->ds_dir->dd_phys->dd_origin_obj, FTAG, &ods));
 		dsl_dataset_name(ods, stat->dds_origin);
 		dsl_dataset_drop_ref(ods, FTAG);
+	} else {
+		stat->dds_origin[0] = '\0';
 	}
 	rw_exit(&ds->ds_dir->dd_pool->dp_config_rwlock);
 }
diff --git a/module/zfs/dsl_scrub.c b/module/zfs/dsl_scrub.c
index 950a91f78..dbdfe8c75 100644
--- a/module/zfs/dsl_scrub.c
+++ b/module/zfs/dsl_scrub.c
@@ -391,7 +391,7 @@ traverse_zil(dsl_pool_t *dp, zil_header_t *zh)
 	 * We only want to visit blocks that have been claimed but not yet
 	 * replayed (or, in read-only mode, blocks that *would* be claimed).
 	 */
-	if (claim_txg == 0 && (spa_mode & FWRITE))
+	if (claim_txg == 0 && spa_writeable(dp->dp_spa))
 		return;
 
 	zilog = zil_alloc(dp->dp_meta_objset, zh);
@@ -409,9 +409,6 @@ scrub_visitbp(dsl_pool_t *dp, dnode_phys_t *dnp,
 	int err;
 	arc_buf_t *buf = NULL;
 
-	if (bp->blk_birth == 0)
-		return;
-
 	if (bp->blk_birth <= dp->dp_scrub_min_txg)
 		return;
 
@@ -740,6 +737,7 @@ enqueue_cb(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
 void
 dsl_pool_scrub_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 {
+	spa_t *spa = dp->dp_spa;
 	zap_cursor_t zc;
 	zap_attribute_t za;
 	boolean_t complete = B_TRUE;
@@ -747,8 +745,10 @@ dsl_pool_scrub_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 	if (dp->dp_scrub_func == SCRUB_FUNC_NONE)
 		return;
 
-	/* If the spa is not fully loaded, don't bother. */
-	if (dp->dp_spa->spa_load_state != SPA_LOAD_NONE)
+	/*
+	 * If the pool is not loaded, or is trying to unload, leave it alone.
+	 */
+	if (spa->spa_load_state != SPA_LOAD_NONE || spa_shutting_down(spa))
 		return;
 
 	if (dp->dp_scrub_restart) {
@@ -757,13 +757,13 @@ dsl_pool_scrub_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 		dsl_pool_scrub_setup_sync(dp, &func, kcred, tx);
 	}
 
-	if (dp->dp_spa->spa_root_vdev->vdev_stat.vs_scrub_type == 0) {
+	if (spa->spa_root_vdev->vdev_stat.vs_scrub_type == 0) {
 		/*
 		 * We must have resumed after rebooting; reset the vdev
 		 * stats to know that we're doing a scrub (although it
 		 * will think we're just starting now).
 		 */
-		vdev_scrub_stat_update(dp->dp_spa->spa_root_vdev,
+		vdev_scrub_stat_update(spa->spa_root_vdev,
 		    dp->dp_scrub_min_txg ? POOL_SCRUB_RESILVER :
 		    POOL_SCRUB_EVERYTHING, B_FALSE);
 	}
@@ -771,7 +771,7 @@ dsl_pool_scrub_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 	dp->dp_scrub_pausing = B_FALSE;
 	dp->dp_scrub_start_time = lbolt64;
 	dp->dp_scrub_isresilver = (dp->dp_scrub_min_txg != 0);
-	dp->dp_spa->spa_scrub_active = B_TRUE;
+	spa->spa_scrub_active = B_TRUE;
 
 	if (dp->dp_scrub_bookmark.zb_objset == 0) {
 		/* First do the MOS & ORIGIN */
@@ -779,8 +779,8 @@ dsl_pool_scrub_sync(dsl_pool_t *dp, dmu_tx_t *tx)
 		if (dp->dp_scrub_pausing)
 			goto out;
 
-		if (spa_version(dp->dp_spa) < SPA_VERSION_DSL_SCRUB) {
-			VERIFY(0 == dmu_objset_find_spa(dp->dp_spa,
+		if (spa_version(spa) < SPA_VERSION_DSL_SCRUB) {
+			VERIFY(0 == dmu_objset_find_spa(spa,
 			    NULL, enqueue_cb, tx, DS_FIND_CHILDREN));
 		} else {
 			scrub_visitds(dp, dp->dp_origin_snap->ds_object, tx);
@@ -830,15 +830,13 @@ out:
 	VERIFY(0 == zap_update(dp->dp_meta_objset,
 	    DMU_POOL_DIRECTORY_OBJECT,
 	    DMU_POOL_SCRUB_ERRORS, sizeof (uint64_t), 1,
-	    &dp->dp_spa->spa_scrub_errors, tx));
+	    &spa->spa_scrub_errors, tx));
 
 	/* XXX this is scrub-clean specific */
-	mutex_enter(&dp->dp_spa->spa_scrub_lock);
-	while (dp->dp_spa->spa_scrub_inflight > 0) {
-		cv_wait(&dp->dp_spa->spa_scrub_io_cv,
-		    &dp->dp_spa->spa_scrub_lock);
-	}
-	mutex_exit(&dp->dp_spa->spa_scrub_lock);
+	mutex_enter(&spa->spa_scrub_lock);
+	while (spa->spa_scrub_inflight > 0)
+		cv_wait(&spa->spa_scrub_io_cv, &spa->spa_scrub_lock);
+	mutex_exit(&spa->spa_scrub_lock);
 }
 
 void
@@ -920,13 +918,17 @@ static int
 dsl_pool_scrub_clean_cb(dsl_pool_t *dp,
     const blkptr_t *bp, const zbookmark_t *zb)
 {
-	size_t size = BP_GET_LSIZE(bp);
-	int d;
+	size_t size = BP_GET_PSIZE(bp);
 	spa_t *spa = dp->dp_spa;
 	boolean_t needs_io;
-	int zio_flags = ZIO_FLAG_SCRUB_THREAD | ZIO_FLAG_CANFAIL;
+	int zio_flags = ZIO_FLAG_SCRUB_THREAD | ZIO_FLAG_RAW | ZIO_FLAG_CANFAIL;
 	int zio_priority;
 
+	ASSERT(bp->blk_birth > dp->dp_scrub_min_txg);
+
+	if (bp->blk_birth >= dp->dp_scrub_max_txg)
+		return (0);
+
 	count_block(dp->dp_blkstats, bp);
 
 	if (dp->dp_scrub_isresilver == 0) {
@@ -945,7 +947,7 @@ dsl_pool_scrub_clean_cb(dsl_pool_t *dp,
 	if (zb->zb_level == -1 && BP_GET_TYPE(bp) != DMU_OT_OBJSET)
 		zio_flags |= ZIO_FLAG_SPECULATIVE;
 
-	for (d = 0; d < BP_GET_NDVAS(bp); d++) {
+	for (int d = 0; d < BP_GET_NDVAS(bp); d++) {
 		vdev_t *vd = vdev_lookup_top(spa,
 		    DVA_GET_VDEV(&bp->blk_dva[d]));
 
@@ -963,16 +965,17 @@ dsl_pool_scrub_clean_cb(dsl_pool_t *dp,
 			if (DVA_GET_GANG(&bp->blk_dva[d])) {
 				/*
 				 * Gang members may be spread across multiple
-				 * vdevs, so the best we can do is look at the
-				 * pool-wide DTL.
+				 * vdevs, so the best estimate we have is the
+				 * scrub range, which has already been checked.
 				 * XXX -- it would be better to change our
-				 * allocation policy to ensure that this can't
-				 * happen.
+				 * allocation policy to ensure that all
+				 * gang members reside on the same vdev.
 				 */
-				vd = spa->spa_root_vdev;
+				needs_io = B_TRUE;
+			} else {
+				needs_io = vdev_dtl_contains(vd, DTL_PARTIAL,
+				    bp->blk_birth, 1);
 			}
-			needs_io = vdev_dtl_contains(&vd->vdev_dtl_map,
-			    bp->blk_birth, 1);
 		}
 	}
 
diff --git a/module/zfs/include/sys/spa.h b/module/zfs/include/sys/spa.h
index 24b3ca447..519b1d0c0 100644
--- a/module/zfs/include/sys/spa.h
+++ b/module/zfs/include/sys/spa.h
@@ -332,7 +332,8 @@ extern int spa_import(const char *pool, nvlist_t *config, nvlist_t *props);
 extern int spa_import_faulted(const char *, nvlist_t *, nvlist_t *);
 extern nvlist_t *spa_tryimport(nvlist_t *tryconfig);
 extern int spa_destroy(char *pool);
-extern int spa_export(char *pool, nvlist_t **oldconfig, boolean_t force);
+extern int spa_export(char *pool, nvlist_t **oldconfig, boolean_t force,
+    boolean_t hardforce);
 extern int spa_reset(char *pool);
 extern void spa_async_request(spa_t *spa, int flag);
 extern void spa_async_unrequest(spa_t *spa, int flag);
@@ -351,7 +352,8 @@ extern void spa_inject_delref(spa_t *spa);
 extern int spa_vdev_add(spa_t *spa, nvlist_t *nvroot);
 extern int spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot,
     int replacing);
-extern int spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done);
+extern int spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid,
+    int replace_done);
 extern int spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare);
 extern int spa_vdev_setpath(spa_t *spa, uint64_t guid, const char *newpath);
 
@@ -475,6 +477,8 @@ extern boolean_t spa_has_spare(spa_t *, uint64_t guid);
 extern uint64_t bp_get_dasize(spa_t *spa, const blkptr_t *bp);
 extern boolean_t spa_has_slogs(spa_t *spa);
 extern boolean_t spa_is_root(spa_t *spa);
+extern boolean_t spa_writeable(spa_t *spa);
+extern int spa_mode(spa_t *spa);
 
 /* history logging */
 typedef enum history_log_type {
@@ -545,7 +549,7 @@ _NOTE(CONSTCOND) } while (0)
 #define	dprintf_bp(bp, fmt, ...)
 #endif
 
-extern int spa_mode;			/* mode, e.g. FREAD | FWRITE */
+extern int spa_mode_global;			/* mode, e.g. FREAD | FWRITE */
 
 #ifdef	__cplusplus
 }
diff --git a/module/zfs/include/sys/spa_impl.h b/module/zfs/include/sys/spa_impl.h
index 8aeb414fe..588b4f5a9 100644
--- a/module/zfs/include/sys/spa_impl.h
+++ b/module/zfs/include/sys/spa_impl.h
@@ -170,6 +170,7 @@ struct spa {
 	boolean_t	spa_import_faulted;	/* allow faulted vdevs */
 	boolean_t	spa_is_root;		/* pool is root */
 	int		spa_minref;		/* num refs when first opened */
+	int		spa_mode;		/* FREAD | FWRITE */
 	spa_log_state_t spa_log_state;		/* log state */
 	/*
 	 * spa_refcnt & spa_config_lock must be the last elements
diff --git a/module/zfs/include/sys/space_map.h b/module/zfs/include/sys/space_map.h
index db9daef1f..8d7860660 100644
--- a/module/zfs/include/sys/space_map.h
+++ b/module/zfs/include/sys/space_map.h
@@ -19,15 +19,13 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
 #ifndef _SYS_SPACE_MAP_H
 #define	_SYS_SPACE_MAP_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/avl.h>
 #include <sys/dmu.h>
 
@@ -58,6 +56,12 @@ typedef struct space_seg {
 	uint64_t	ss_end;		/* ending offset (non-inclusive) */
 } space_seg_t;
 
+typedef struct space_ref {
+	avl_node_t	sr_node;	/* AVL node */
+	uint64_t	sr_offset;	/* offset (start or end) */
+	int64_t		sr_refcnt;	/* associated reference count */
+} space_ref_t;
+
 typedef struct space_map_obj {
 	uint64_t	smo_object;	/* on-disk space map object */
 	uint64_t	smo_objsize;	/* size of the object */
@@ -133,13 +137,12 @@ extern void space_map_create(space_map_t *sm, uint64_t start, uint64_t size,
 extern void space_map_destroy(space_map_t *sm);
 extern void space_map_add(space_map_t *sm, uint64_t start, uint64_t size);
 extern void space_map_remove(space_map_t *sm, uint64_t start, uint64_t size);
-extern int space_map_contains(space_map_t *sm, uint64_t start, uint64_t size);
+extern boolean_t space_map_contains(space_map_t *sm,
+    uint64_t start, uint64_t size);
 extern void space_map_vacate(space_map_t *sm,
     space_map_func_t *func, space_map_t *mdest);
 extern void space_map_walk(space_map_t *sm,
     space_map_func_t *func, space_map_t *mdest);
-extern void space_map_excise(space_map_t *sm, uint64_t start, uint64_t size);
-extern void space_map_union(space_map_t *smd, space_map_t *sms);
 
 extern void space_map_load_wait(space_map_t *sm);
 extern int space_map_load(space_map_t *sm, space_map_ops_t *ops,
@@ -155,6 +158,15 @@ extern void space_map_sync(space_map_t *sm, uint8_t maptype,
 extern void space_map_truncate(space_map_obj_t *smo,
     objset_t *os, dmu_tx_t *tx);
 
+extern void space_map_ref_create(avl_tree_t *t);
+extern void space_map_ref_destroy(avl_tree_t *t);
+extern void space_map_ref_add_seg(avl_tree_t *t,
+    uint64_t start, uint64_t end, int64_t refcnt);
+extern void space_map_ref_add_map(avl_tree_t *t,
+    space_map_t *sm, int64_t refcnt);
+extern void space_map_ref_generate_map(avl_tree_t *t,
+    space_map_t *sm, int64_t minref);
+
 #ifdef	__cplusplus
 }
 #endif
diff --git a/module/zfs/include/sys/uberblock_impl.h b/module/zfs/include/sys/uberblock_impl.h
index 55a0dd5ae..b49df8ae0 100644
--- a/module/zfs/include/sys/uberblock_impl.h
+++ b/module/zfs/include/sys/uberblock_impl.h
@@ -19,15 +19,13 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
 #ifndef _SYS_UBERBLOCK_IMPL_H
 #define	_SYS_UBERBLOCK_IMPL_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/uberblock.h>
 
 #ifdef	__cplusplus
@@ -35,6 +33,11 @@ extern "C" {
 #endif
 
 /*
+ * For zdb use and debugging purposes only
+ */
+extern uint64_t ub_max_txg;
+
+/*
  * The uberblock version is incremented whenever an incompatible on-disk
  * format change is made to the SPA, DMU, or ZAP.
  *
diff --git a/module/zfs/include/sys/vdev.h b/module/zfs/include/sys/vdev.h
index c070d6f3d..b8313a920 100644
--- a/module/zfs/include/sys/vdev.h
+++ b/module/zfs/include/sys/vdev.h
@@ -36,6 +36,14 @@
 extern "C" {
 #endif
 
+typedef enum vdev_dtl_type {
+	DTL_MISSING,	/* 0% replication: no copies of the data */
+	DTL_PARTIAL,	/* less than 100% replication: some copies missing */
+	DTL_SCRUB,	/* unable to fully repair during scrub/resilver */
+	DTL_OUTAGE,	/* temporarily missing (used to attempt detach) */
+	DTL_TYPES
+} vdev_dtl_type_t;
+
 extern boolean_t zfs_nocacheflush;
 
 extern int vdev_open(vdev_t *);
@@ -50,10 +58,14 @@ extern zio_t *vdev_probe(vdev_t *vd, zio_t *pio);
 extern boolean_t vdev_is_bootable(vdev_t *vd);
 extern vdev_t *vdev_lookup_top(spa_t *spa, uint64_t vdev);
 extern vdev_t *vdev_lookup_by_guid(vdev_t *vd, uint64_t guid);
-extern void vdev_dtl_dirty(space_map_t *sm, uint64_t txg, uint64_t size);
-extern int vdev_dtl_contains(space_map_t *sm, uint64_t txg, uint64_t size);
+extern void vdev_dtl_dirty(vdev_t *vd, vdev_dtl_type_t d,
+    uint64_t txg, uint64_t size);
+extern boolean_t vdev_dtl_contains(vdev_t *vd, vdev_dtl_type_t d,
+    uint64_t txg, uint64_t size);
+extern boolean_t vdev_dtl_empty(vdev_t *vd, vdev_dtl_type_t d);
 extern void vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg,
     int scrub_done);
+extern boolean_t vdev_dtl_required(vdev_t *vd);
 extern boolean_t vdev_resilver_needed(vdev_t *vd,
     uint64_t *minp, uint64_t *maxp);
 
diff --git a/module/zfs/include/sys/vdev_impl.h b/module/zfs/include/sys/vdev_impl.h
index 26904d089..652349341 100644
--- a/module/zfs/include/sys/vdev_impl.h
+++ b/module/zfs/include/sys/vdev_impl.h
@@ -123,8 +123,7 @@ struct vdev {
 	vdev_t		*vdev_parent;	/* parent vdev			*/
 	vdev_t		**vdev_child;	/* array of children		*/
 	uint64_t	vdev_children;	/* number of children		*/
-	space_map_t	vdev_dtl_map;	/* dirty time log in-core state	*/
-	space_map_t	vdev_dtl_scrub;	/* DTL for scrub repair writes	*/
+	space_map_t	vdev_dtl[DTL_TYPES]; /* in-core dirty time logs	*/
 	vdev_stat_t	vdev_stat;	/* virtual device statistics	*/
 
 	/*
@@ -149,7 +148,7 @@ struct vdev {
 	 * Leaf vdev state.
 	 */
 	uint64_t	vdev_psize;	/* physical device capacity	*/
-	space_map_obj_t	vdev_dtl;	/* dirty time log on-disk state	*/
+	space_map_obj_t	vdev_dtl_smo;	/* dirty time log space map obj	*/
 	txg_node_t	vdev_dtl_node;	/* per-txg dirty DTL linkage	*/
 	uint64_t	vdev_wholedisk;	/* true if this is a whole disk */
 	uint64_t	vdev_offline;	/* persistent offline state	*/
diff --git a/module/zfs/include/sys/zfs_vfsops.h b/module/zfs/include/sys/zfs_vfsops.h
index 87b75e6e7..7e0440be4 100644
--- a/module/zfs/include/sys/zfs_vfsops.h
+++ b/module/zfs/include/sys/zfs_vfsops.h
@@ -26,8 +26,6 @@
 #ifndef	_SYS_FS_ZFS_VFSOPS_H
 #define	_SYS_FS_ZFS_VFSOPS_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/isa_defs.h>
 #include <sys/types32.h>
 #include <sys/list.h>
@@ -49,7 +47,6 @@ struct zfsvfs {
 	uint64_t	z_root;		/* id of root znode */
 	uint64_t	z_unlinkedobj;	/* id of unlinked zapobj */
 	uint64_t	z_max_blksz;	/* maximum block size for files */
-	uint64_t	z_assign;	/* TXG_NOWAIT or set by zil_replay() */
 	uint64_t	z_fuid_obj;	/* fuid table object number */
 	uint64_t	z_fuid_size;	/* fuid table size */
 	avl_tree_t	z_fuid_idx;	/* fuid tree keyed by index */
@@ -74,6 +71,7 @@ struct zfsvfs {
 	boolean_t	z_issnap;	/* true if this is a snapshot */
 	boolean_t	z_vscan;	/* virus scan on/off */
 	boolean_t	z_use_fuids;	/* version allows fuids */
+	boolean_t	z_replay;	/* set during ZIL replay */
 	kmutex_t	z_online_recv_lock; /* recv in prog grabs as WRITER */
 	uint64_t	z_version;	/* ZPL version */
 #define	ZFS_OBJ_MTX_SZ	64
diff --git a/module/zfs/include/sys/zil.h b/module/zfs/include/sys/zil.h
index 4d02d14f7..b69323cfa 100644
--- a/module/zfs/include/sys/zil.h
+++ b/module/zfs/include/sys/zil.h
@@ -335,7 +335,6 @@ typedef void zil_parse_blk_func_t(zilog_t *zilog, blkptr_t *bp, void *arg,
 typedef void zil_parse_lr_func_t(zilog_t *zilog, lr_t *lr, void *arg,
     uint64_t txg);
 typedef int zil_replay_func_t();
-typedef void zil_replay_cleaner_t();
 typedef int zil_get_data_t(void *arg, lr_write_t *lr, char *dbuf, zio_t *zio);
 
 extern uint64_t	zil_parse(zilog_t *zilog, zil_parse_blk_func_t *parse_blk_func,
@@ -350,9 +349,8 @@ extern void	zil_free(zilog_t *zilog);
 extern zilog_t	*zil_open(objset_t *os, zil_get_data_t *get_data);
 extern void	zil_close(zilog_t *zilog);
 
-extern void	zil_replay(objset_t *os, void *arg, uint64_t *txgp,
-    zil_replay_func_t *replay_func[TX_MAX_TYPE],
-    zil_replay_cleaner_t *replay_cleaner);
+extern void	zil_replay(objset_t *os, void *arg,
+    zil_replay_func_t *replay_func[TX_MAX_TYPE]);
 extern void	zil_destroy(zilog_t *zilog, boolean_t keep_first);
 extern void	zil_rollback_destroy(zilog_t *zilog, dmu_tx_t *tx);
 
diff --git a/module/zfs/include/sys/zil_impl.h b/module/zfs/include/sys/zil_impl.h
index 0fc800b96..3f2582931 100644
--- a/module/zfs/include/sys/zil_impl.h
+++ b/module/zfs/include/sys/zil_impl.h
@@ -19,15 +19,13 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
 #ifndef	_SYS_ZIL_IMPL_H
 #define	_SYS_ZIL_IMPL_H
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/zil.h>
 #include <sys/dmu_objset.h>
 
@@ -74,13 +72,14 @@ struct zilog {
 	uint64_t	zl_commit_seq;	/* committed upto this number */
 	uint64_t	zl_lr_seq;	/* log record sequence number */
 	uint64_t	zl_destroy_txg;	/* txg of last zil_destroy() */
-	uint64_t	zl_replay_seq[TXG_SIZE]; /* seq of last replayed rec */
+	uint64_t	zl_replayed_seq[TXG_SIZE]; /* last replayed rec seq */
+	uint64_t	zl_replaying_seq; /* current replay seq number */
 	uint32_t	zl_suspend;	/* log suspend count */
 	kcondvar_t	zl_cv_writer;	/* log writer thread completion */
 	kcondvar_t	zl_cv_suspend;	/* log suspend completion */
 	uint8_t		zl_suspending;	/* log is currently suspending */
 	uint8_t		zl_keep_first;	/* keep first log block in destroy */
-	uint8_t		zl_stop_replay;	/* don't replay any further */
+	uint8_t		zl_replay;	/* replaying records while set */
 	uint8_t		zl_stop_sync;	/* for debugging */
 	uint8_t		zl_writer;	/* boolean: write setup in progress */
 	uint8_t		zl_log_error;	/* boolean: log write error */
diff --git a/module/zfs/include/sys/zio.h b/module/zfs/include/sys/zio.h
index 4de78dfee..21b0fbc6b 100644
--- a/module/zfs/include/sys/zio.h
+++ b/module/zfs/include/sys/zio.h
@@ -132,12 +132,14 @@ enum zio_compress {
 #define	ZIO_FLAG_IO_RETRY		0x00400
 #define	ZIO_FLAG_IO_REWRITE		0x00800
 
-#define	ZIO_FLAG_PROBE			0x01000
+#define	ZIO_FLAG_SELF_HEAL		0x01000
 #define	ZIO_FLAG_RESILVER		0x02000
 #define	ZIO_FLAG_SCRUB			0x04000
 #define	ZIO_FLAG_SCRUB_THREAD		0x08000
 
-#define	ZIO_FLAG_GANG_CHILD		0x10000
+#define	ZIO_FLAG_PROBE			0x10000
+#define	ZIO_FLAG_GANG_CHILD		0x20000
+#define	ZIO_FLAG_RAW			0x40000
 
 #define	ZIO_FLAG_GANG_INHERIT		\
 	(ZIO_FLAG_CANFAIL |		\
@@ -146,6 +148,7 @@ enum zio_compress {
 	ZIO_FLAG_DONT_RETRY |		\
 	ZIO_FLAG_DONT_CACHE |		\
 	ZIO_FLAG_DONT_AGGREGATE |	\
+	ZIO_FLAG_SELF_HEAL |		\
 	ZIO_FLAG_RESILVER |		\
 	ZIO_FLAG_SCRUB |		\
 	ZIO_FLAG_SCRUB_THREAD)
@@ -156,6 +159,14 @@ enum zio_compress {
 	ZIO_FLAG_IO_RETRY |		\
 	ZIO_FLAG_PROBE)
 
+#define	ZIO_FLAG_AGG_INHERIT		\
+	(ZIO_FLAG_DONT_AGGREGATE |	\
+	ZIO_FLAG_IO_REPAIR |		\
+	ZIO_FLAG_SELF_HEAL |		\
+	ZIO_FLAG_RESILVER |		\
+	ZIO_FLAG_SCRUB |		\
+	ZIO_FLAG_SCRUB_THREAD)
+
 #define	ZIO_PIPELINE_CONTINUE		0x100
 #define	ZIO_PIPELINE_STOP		0x101
 
diff --git a/module/zfs/metaslab.c b/module/zfs/metaslab.c
index 87727fac2..412832968 100644
--- a/module/zfs/metaslab.c
+++ b/module/zfs/metaslab.c
@@ -720,6 +720,8 @@ metaslab_alloc_dva(spa_t *spa, metaslab_class_t *mc, uint64_t psize,
 	vdev_t *vd;
 	int dshift = 3;
 	int all_zero;
+	int zio_lock = B_FALSE;
+	boolean_t allocatable;
 	uint64_t offset = -1ULL;
 	uint64_t asize;
 	uint64_t distance;
@@ -778,11 +780,20 @@ top:
 	all_zero = B_TRUE;
 	do {
 		vd = mg->mg_vd;
+
 		/*
 		 * Don't allocate from faulted devices.
 		 */
-		if (!vdev_allocatable(vd))
+		if (zio_lock) {
+			spa_config_enter(spa, SCL_ZIO, FTAG, RW_READER);
+			allocatable = vdev_allocatable(vd);
+			spa_config_exit(spa, SCL_ZIO, FTAG);
+		} else {
+			allocatable = vdev_allocatable(vd);
+		}
+		if (!allocatable)
 			goto next;
+
 		/*
 		 * Avoid writing single-copy data to a failing vdev
 		 */
@@ -858,6 +869,12 @@ next:
 		goto top;
 	}
 
+	if (!zio_lock) {
+		dshift = 3;
+		zio_lock = B_TRUE;
+		goto top;
+	}
+
 	bzero(&dva[d], sizeof (dva_t));
 
 	return (ENOSPC);
@@ -946,7 +963,7 @@ metaslab_claim_dva(spa_t *spa, const dva_t *dva, uint64_t txg)
 
 	space_map_claim(&msp->ms_map, offset, size);
 
-	if (spa_mode & FWRITE) {	/* don't dirty if we're zdb(1M) */
+	if (spa_writeable(spa)) {	/* don't dirty if we're zdb(1M) */
 		if (msp->ms_allocmap[txg & TXG_MASK].sm_space == 0)
 			vdev_dirty(vd, VDD_METASLAB, msp, txg);
 		space_map_add(&msp->ms_allocmap[txg & TXG_MASK], offset, size);
diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index fb1b96f8b..ef04b7c94 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -486,11 +486,12 @@ spa_get_errlists(spa_t *spa, avl_tree_t *last, avl_tree_t *scrub)
  * Activate an uninitialized pool.
  */
 static void
-spa_activate(spa_t *spa)
+spa_activate(spa_t *spa, int mode)
 {
 	ASSERT(spa->spa_state == POOL_STATE_UNINITIALIZED);
 
 	spa->spa_state = POOL_STATE_ACTIVE;
+	spa->spa_mode = mode;
 
 	spa->spa_normal_class = metaslab_class_create();
 	spa->spa_log_class = metaslab_class_create();
@@ -640,11 +641,6 @@ spa_unload(spa_t *spa)
 	mutex_exit(&spa->spa_async_root_lock);
 
 	/*
-	 * Drop and purge level 2 cache
-	 */
-	spa_l2cache_drop(spa);
-
-	/*
 	 * Close the dsl pool.
 	 */
 	if (spa->spa_dsl_pool) {
@@ -652,6 +648,13 @@ spa_unload(spa_t *spa)
 		spa->spa_dsl_pool = NULL;
 	}
 
+	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+
+	/*
+	 * Drop and purge level 2 cache
+	 */
+	spa_l2cache_drop(spa);
+
 	/*
 	 * Close all vdevs.
 	 */
@@ -686,6 +689,8 @@ spa_unload(spa_t *spa)
 	spa->spa_l2cache.sav_count = 0;
 
 	spa->spa_async_suspended = 0;
+
+	spa_config_exit(spa, SCL_ALL, FTAG);
 }
 
 /*
@@ -897,12 +902,9 @@ spa_load_l2cache(spa_t *spa)
 
 		vd = oldvdevs[i];
 		if (vd != NULL) {
-			if ((spa_mode & FWRITE) &&
-			    spa_l2cache_exists(vd->vdev_guid, &pool) &&
-			    pool != 0ULL &&
-			    l2arc_vdev_present(vd)) {
+			if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
+			    pool != 0ULL && l2arc_vdev_present(vd))
 				l2arc_remove_vdev(vd);
-			}
 			(void) vdev_close(vd);
 			spa_l2cache_remove(vd);
 		}
@@ -1018,8 +1020,16 @@ spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
 	uint64_t pool_guid;
 	uint64_t version;
 	uint64_t autoreplace = 0;
+	int orig_mode = spa->spa_mode;
 	char *ereport = FM_EREPORT_ZFS_POOL;
 
+	/*
+	 * If this is an untrusted config, access the pool in read-only mode.
+	 * This prevents things like resilvering recently removed devices.
+	 */
+	if (!mosconfig)
+		spa->spa_mode = FREAD;
+
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 
 	spa->spa_load_state = state;
@@ -1077,12 +1087,13 @@ spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
 	 * Validate the labels for all leaf vdevs.  We need to grab the config
 	 * lock because all label I/O is done with ZIO_FLAG_CONFIG_WRITER.
 	 */
-	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
-	error = vdev_validate(rvd);
-	spa_config_exit(spa, SCL_ALL, FTAG);
-
-	if (error != 0)
-		goto out;
+	if (mosconfig) {
+		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
+		error = vdev_validate(rvd);
+		spa_config_exit(spa, SCL_ALL, FTAG);
+		if (error != 0)
+			goto out;
+	}
 
 	if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN) {
 		error = ENXIO;
@@ -1184,7 +1195,7 @@ spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
 		spa_config_set(spa, newconfig);
 		spa_unload(spa);
 		spa_deactivate(spa);
-		spa_activate(spa);
+		spa_activate(spa, orig_mode);
 
 		return (spa_load(spa, newconfig, state, B_TRUE));
 	}
@@ -1376,10 +1387,11 @@ spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
 		goto out;
 	}
 
-	if ((spa_mode & FWRITE) && state != SPA_LOAD_TRYIMPORT) {
+	if (spa_writeable(spa)) {
 		dmu_tx_t *tx;
 		int need_update = B_FALSE;
-		int c;
+
+		ASSERT(state != SPA_LOAD_TRYIMPORT);
 
 		/*
 		 * Claim log blocks that haven't been committed yet.
@@ -1407,7 +1419,7 @@ spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
 		    state == SPA_LOAD_IMPORT)
 			need_update = B_TRUE;
 
-		for (c = 0; c < rvd->vdev_children; c++)
+		for (int c = 0; c < rvd->vdev_children; c++)
 			if (rvd->vdev_child[c]->vdev_ms_array == 0)
 				need_update = B_TRUE;
 
@@ -1417,6 +1429,12 @@ spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
 		 */
 		if (need_update)
 			spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
+
+		/*
+		 * Check all DTLs to see if anything needs resilvering.
+		 */
+		if (vdev_resilver_needed(rvd, NULL, NULL))
+			spa_async_request(spa, SPA_ASYNC_RESILVER);
 	}
 
 	error = 0;
@@ -1469,7 +1487,7 @@ spa_open_common(const char *pool, spa_t **spapp, void *tag, nvlist_t **config)
 	}
 	if (spa->spa_state == POOL_STATE_UNINITIALIZED) {
 
-		spa_activate(spa);
+		spa_activate(spa, spa_mode_global);
 
 		error = spa_load(spa, spa->spa_config, SPA_LOAD_OPEN, B_FALSE);
 
@@ -1873,11 +1891,9 @@ spa_l2cache_drop(spa_t *spa)
 		vd = sav->sav_vdevs[i];
 		ASSERT(vd != NULL);
 
-		if ((spa_mode & FWRITE) &&
-		    spa_l2cache_exists(vd->vdev_guid, &pool) && pool != 0ULL &&
-		    l2arc_vdev_present(vd)) {
+		if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
+		    pool != 0ULL && l2arc_vdev_present(vd))
 			l2arc_remove_vdev(vd);
-		}
 		if (vd->vdev_isl2cache)
 			spa_l2cache_remove(vd);
 		vdev_clear_stats(vd);
@@ -1918,7 +1934,7 @@ spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
 	(void) nvlist_lookup_string(props,
 	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
 	spa = spa_add(pool, altroot);
-	spa_activate(spa);
+	spa_activate(spa, spa_mode_global);
 
 	spa->spa_uberblock.ub_txg = txg - 1;
 
@@ -2121,7 +2137,7 @@ spa_import_common(const char *pool, nvlist_t *config, nvlist_t *props,
 	(void) nvlist_lookup_string(props,
 	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
 	spa = spa_add(pool, altroot);
-	spa_activate(spa);
+	spa_activate(spa, spa_mode_global);
 
 	if (allowfaulted)
 		spa->spa_import_faulted = B_TRUE;
@@ -2160,7 +2176,8 @@ spa_import_common(const char *pool, nvlist_t *config, nvlist_t *props,
 		    VDEV_ALLOC_L2CACHE);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
-	if (error != 0 || (props && (error = spa_prop_set(spa, props)))) {
+	if (error != 0 || (props && spa_writeable(spa) &&
+	    (error = spa_prop_set(spa, props)))) {
 		if (loaderr != 0 && loaderr != EINVAL && allowfaulted) {
 			/*
 			 * If we failed to load the pool, but 'allowfaulted' is
@@ -2219,7 +2236,7 @@ spa_import_common(const char *pool, nvlist_t *config, nvlist_t *props,
 		spa->spa_l2cache.sav_sync = B_TRUE;
 	}
 
-	if (spa_mode & FWRITE) {
+	if (spa_writeable(spa)) {
 		/*
 		 * Update the config cache to include the newly-imported pool.
 		 */
@@ -2367,11 +2384,11 @@ spa_get_rootconf(char *devpath, char *devid, nvlist_t **bestconf)
 		char *cdevid, *cpath;
 		uint64_t tmptxg;
 
+		cpath = NULL;
+		cdevid = NULL;
 		if (nvlist_lookup_string(child[c], ZPOOL_CONFIG_PHYS_PATH,
-		    &cpath) != 0)
-			return (EINVAL);
-		if (nvlist_lookup_string(child[c], ZPOOL_CONFIG_DEVID,
-		    &cdevid) != 0)
+		    &cpath) != 0 && nvlist_lookup_string(child[c],
+		    ZPOOL_CONFIG_DEVID, &cdevid) != 0)
 			return (EINVAL);
 		if ((spa_check_rootconf(cpath, cdevid, NULL,
 		    &tmptxg) == 0) && (tmptxg > txg)) {
@@ -2489,7 +2506,7 @@ spa_tryimport(nvlist_t *tryconfig)
 	 */
 	mutex_enter(&spa_namespace_lock);
 	spa = spa_add(TRYIMPORT_NAME, NULL);
-	spa_activate(spa);
+	spa_activate(spa, FREAD);
 
 	/*
 	 * Pass off the heavy lifting to spa_load().
@@ -2563,18 +2580,19 @@ spa_tryimport(nvlist_t *tryconfig)
  * The act of destroying or exporting a pool is very simple.  We make sure there
  * is no more pending I/O and any references to the pool are gone.  Then, we
  * update the pool state and sync all the labels to disk, removing the
- * configuration from the cache afterwards.
+ * configuration from the cache afterwards. If the 'hardforce' flag is set, then
+ * we don't sync the labels or remove the configuration cache.
  */
 static int
 spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
-    boolean_t force)
+    boolean_t force, boolean_t hardforce)
 {
 	spa_t *spa;
 
 	if (oldconfig)
 		*oldconfig = NULL;
 
-	if (!(spa_mode & FWRITE))
+	if (!(spa_mode_global & FWRITE))
 		return (EROFS);
 
 	mutex_enter(&spa_namespace_lock);
@@ -2635,7 +2653,7 @@ spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
 		 * so mark them all dirty.  spa_unload() will do the
 		 * final sync that pushes these changes out.
 		 */
-		if (new_state != POOL_STATE_UNINITIALIZED) {
+		if (new_state != POOL_STATE_UNINITIALIZED && !hardforce) {
 			spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 			spa->spa_state = new_state;
 			spa->spa_final_txg = spa_last_synced_txg(spa) + 1;
@@ -2655,7 +2673,8 @@ spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
 		VERIFY(nvlist_dup(spa->spa_config, oldconfig, 0) == 0);
 
 	if (new_state != POOL_STATE_UNINITIALIZED) {
-		spa_config_sync(spa, B_TRUE, B_TRUE);
+		if (!hardforce)
+			spa_config_sync(spa, B_TRUE, B_TRUE);
 		spa_remove(spa);
 	}
 	mutex_exit(&spa_namespace_lock);
@@ -2669,16 +2688,19 @@ spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
 int
 spa_destroy(char *pool)
 {
-	return (spa_export_common(pool, POOL_STATE_DESTROYED, NULL, B_FALSE));
+	return (spa_export_common(pool, POOL_STATE_DESTROYED, NULL,
+	    B_FALSE, B_FALSE));
 }
 
 /*
  * Export a storage pool.
  */
 int
-spa_export(char *pool, nvlist_t **oldconfig, boolean_t force)
+spa_export(char *pool, nvlist_t **oldconfig, boolean_t force,
+    boolean_t hardforce)
 {
-	return (spa_export_common(pool, POOL_STATE_EXPORTED, oldconfig, force));
+	return (spa_export_common(pool, POOL_STATE_EXPORTED, oldconfig,
+	    force, hardforce));
 }
 
 /*
@@ -2689,7 +2711,7 @@ int
 spa_reset(char *pool)
 {
 	return (spa_export_common(pool, POOL_STATE_UNINITIALIZED, NULL,
-	    B_FALSE));
+	    B_FALSE, B_FALSE));
 }
 
 /*
@@ -2705,7 +2727,7 @@ int
 spa_vdev_add(spa_t *spa, nvlist_t *nvroot)
 {
 	uint64_t txg;
-	int c, error;
+	int error;
 	vdev_t *rvd = spa->spa_root_vdev;
 	vdev_t *vd, *tvd;
 	nvlist_t **spares, **l2cache;
@@ -2744,7 +2766,7 @@ spa_vdev_add(spa_t *spa, nvlist_t *nvroot)
 	/*
 	 * Transfer each new top-level vdev from vd to rvd.
 	 */
-	for (c = 0; c < vd->vdev_children; c++) {
+	for (int c = 0; c < vd->vdev_children; c++) {
 		tvd = vd->vdev_child[c];
 		vdev_remove_child(vd, tvd);
 		tvd->vdev_id = rvd->vdev_children;
@@ -2952,10 +2974,8 @@ spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing)
 	 */
 	open_txg = txg + TXG_CONCURRENT_STATES - 1;
 
-	mutex_enter(&newvd->vdev_dtl_lock);
-	space_map_add(&newvd->vdev_dtl_map, TXG_INITIAL,
-	    open_txg - TXG_INITIAL + 1);
-	mutex_exit(&newvd->vdev_dtl_lock);
+	vdev_dtl_dirty(newvd, DTL_MISSING,
+	    TXG_INITIAL, open_txg - TXG_INITIAL + 1);
 
 	if (newvd->vdev_isspare)
 		spa_spare_activate(newvd);
@@ -2999,10 +3019,10 @@ spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing)
  * is a replacing vdev.
  */
 int
-spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
+spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid, int replace_done)
 {
 	uint64_t txg;
-	int c, t, error;
+	int error;
 	vdev_t *rvd = spa->spa_root_vdev;
 	vdev_t *vd, *pvd, *cvd, *tvd;
 	boolean_t unspare = B_FALSE;
@@ -3022,6 +3042,22 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
 	pvd = vd->vdev_parent;
 
 	/*
+	 * If the parent/child relationship is not as expected, don't do it.
+	 * Consider M(A,R(B,C)) -- that is, a mirror of A with a replacing
+	 * vdev that's replacing B with C.  The user's intent in replacing
+	 * is to go from M(A,B) to M(A,C).  If the user decides to cancel
+	 * the replace by detaching C, the expected behavior is to end up
+	 * M(A,B).  But suppose that right after deciding to detach C,
+	 * the replacement of B completes.  We would have M(A,C), and then
+	 * ask to detach C, which would leave us with just A -- not what
+	 * the user wanted.  To prevent this, we make sure that the
+	 * parent/child relationship hasn't changed -- in this example,
+	 * that C's parent is still the replacing vdev R.
+	 */
+	if (pvd->vdev_guid != pguid && pguid != 0)
+		return (spa_vdev_exit(spa, NULL, txg, EBUSY));
+
+	/*
 	 * If replace_done is specified, only remove this device if it's
 	 * the first child of a replacing vdev.  For the 'spare' vdev, either
 	 * disk can be removed.
@@ -3047,36 +3083,13 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
 		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));
 
 	/*
-	 * If there's only one replica, you can't detach it.
+	 * If this device has the only valid copy of some data,
+	 * we cannot safely detach it.
 	 */
-	if (pvd->vdev_children <= 1)
+	if (vdev_dtl_required(vd))
 		return (spa_vdev_exit(spa, NULL, txg, EBUSY));
 
-	/*
-	 * If all siblings have non-empty DTLs, this device may have the only
-	 * valid copy of the data, which means we cannot safely detach it.
-	 *
-	 * XXX -- as in the vdev_offline() case, we really want a more
-	 * precise DTL check.
-	 */
-	for (c = 0; c < pvd->vdev_children; c++) {
-		uint64_t dirty;
-
-		cvd = pvd->vdev_child[c];
-		if (cvd == vd)
-			continue;
-		if (vdev_is_dead(cvd))
-			continue;
-		mutex_enter(&cvd->vdev_dtl_lock);
-		dirty = cvd->vdev_dtl_map.sm_space |
-		    cvd->vdev_dtl_scrub.sm_space;
-		mutex_exit(&cvd->vdev_dtl_lock);
-		if (!dirty)
-			break;
-	}
-
-	if (c == pvd->vdev_children)
-		return (spa_vdev_exit(spa, NULL, txg, EBUSY));
+	ASSERT(pvd->vdev_children >= 2);
 
 	/*
 	 * If we are detaching the second disk from a replacing vdev, then
@@ -3102,7 +3115,7 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
 	 * active spare list for the pool.
 	 */
 	if (pvd->vdev_ops == &vdev_spare_ops &&
-	    vd->vdev_id == 0)
+	    vd->vdev_id == 0 && pvd->vdev_child[1]->vdev_isspare)
 		unspare = B_TRUE;
 
 	/*
@@ -3128,14 +3141,18 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
 
 	/*
 	 * If we need to remove the remaining child from the list of hot spares,
-	 * do it now, marking the vdev as no longer a spare in the process.  We
-	 * must do this before vdev_remove_parent(), because that can change the
-	 * GUID if it creates a new toplevel GUID.
+	 * do it now, marking the vdev as no longer a spare in the process.
+	 * We must do this before vdev_remove_parent(), because that can
+	 * change the GUID if it creates a new toplevel GUID.  For a similar
+	 * reason, we must remove the spare now, in the same txg as the detach;
+	 * otherwise someone could attach a new sibling, change the GUID, and
+	 * the subsequent attempt to spa_vdev_remove(unspare_guid) would fail.
 	 */
 	if (unspare) {
 		ASSERT(cvd->vdev_isspare);
 		spa_spare_remove(cvd);
 		unspare_guid = cvd->vdev_guid;
+		(void) spa_vdev_remove(spa, unspare_guid, B_TRUE);
 	}
 
 	/*
@@ -3173,7 +3190,7 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
 	 * But first make sure we're not on any *other* txg's DTL list, to
 	 * prevent vd from being accessed after it's freed.
 	 */
-	for (t = 0; t < TXG_SIZE; t++)
+	for (int t = 0; t < TXG_SIZE; t++)
 		(void) txg_list_remove_this(&tvd->vdev_dtl_list, vd, t);
 	vd->vdev_detached = B_TRUE;
 	vdev_dirty(tvd, VDD_DTL, vd, txg);
@@ -3188,11 +3205,14 @@ spa_vdev_detach(spa_t *spa, uint64_t guid, int replace_done)
 	 * list of every other pool.
 	 */
 	if (unspare) {
+		spa_t *myspa = spa;
 		spa = NULL;
 		mutex_enter(&spa_namespace_lock);
 		while ((spa = spa_next(spa)) != NULL) {
 			if (spa->spa_state != POOL_STATE_ACTIVE)
 				continue;
+			if (spa == myspa)
+				continue;
 			spa_open_ref(spa, FTAG);
 			mutex_exit(&spa_namespace_lock);
 			(void) spa_vdev_remove(spa, unspare_guid, B_TRUE);
@@ -3256,10 +3276,12 @@ spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare)
 	vdev_t *vd;
 	nvlist_t **spares, **l2cache, *nv;
 	uint_t nspares, nl2cache;
-	uint64_t txg;
+	uint64_t txg = 0;
 	int error = 0;
+	boolean_t locked = MUTEX_HELD(&spa_namespace_lock);
 
-	txg = spa_vdev_enter(spa);
+	if (!locked)
+		txg = spa_vdev_enter(spa);
 
 	vd = spa_lookup_by_guid(spa, guid, B_FALSE);
 
@@ -3302,7 +3324,10 @@ spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare)
 		error = ENOENT;
 	}
 
-	return (spa_vdev_exit(spa, NULL, txg, error));
+	if (!locked)
+		return (spa_vdev_exit(spa, NULL, txg, error));
+
+	return (error);
 }
 
 /*
@@ -3328,13 +3353,9 @@ spa_vdev_resilver_done_hunt(vdev_t *vd)
 		oldvd = vd->vdev_child[0];
 		newvd = vd->vdev_child[1];
 
-		mutex_enter(&newvd->vdev_dtl_lock);
-		if (newvd->vdev_dtl_map.sm_space == 0 &&
-		    newvd->vdev_dtl_scrub.sm_space == 0) {
-			mutex_exit(&newvd->vdev_dtl_lock);
+		if (vdev_dtl_empty(newvd, DTL_MISSING) &&
+		    !vdev_dtl_required(oldvd))
 			return (oldvd);
-		}
-		mutex_exit(&newvd->vdev_dtl_lock);
 	}
 
 	/*
@@ -3344,15 +3365,12 @@ spa_vdev_resilver_done_hunt(vdev_t *vd)
 		newvd = vd->vdev_child[0];
 		oldvd = vd->vdev_child[1];
 
-		mutex_enter(&newvd->vdev_dtl_lock);
 		if (newvd->vdev_unspare &&
-		    newvd->vdev_dtl_map.sm_space == 0 &&
-		    newvd->vdev_dtl_scrub.sm_space == 0) {
+		    vdev_dtl_empty(newvd, DTL_MISSING) &&
+		    !vdev_dtl_required(oldvd)) {
 			newvd->vdev_unspare = 0;
-			mutex_exit(&newvd->vdev_dtl_lock);
 			return (oldvd);
 		}
-		mutex_exit(&newvd->vdev_dtl_lock);
 	}
 
 	return (NULL);
@@ -3361,36 +3379,37 @@ spa_vdev_resilver_done_hunt(vdev_t *vd)
 static void
 spa_vdev_resilver_done(spa_t *spa)
 {
-	vdev_t *vd;
-	vdev_t *pvd;
-	uint64_t guid;
-	uint64_t pguid = 0;
+	vdev_t *vd, *pvd, *ppvd;
+	uint64_t guid, sguid, pguid, ppguid;
 
-	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 
 	while ((vd = spa_vdev_resilver_done_hunt(spa->spa_root_vdev)) != NULL) {
+		pvd = vd->vdev_parent;
+		ppvd = pvd->vdev_parent;
 		guid = vd->vdev_guid;
+		pguid = pvd->vdev_guid;
+		ppguid = ppvd->vdev_guid;
+		sguid = 0;
 		/*
 		 * If we have just finished replacing a hot spared device, then
 		 * we need to detach the parent's first child (the original hot
 		 * spare) as well.
 		 */
-		pvd = vd->vdev_parent;
-		if (pvd->vdev_parent->vdev_ops == &vdev_spare_ops &&
-		    pvd->vdev_id == 0) {
+		if (ppvd->vdev_ops == &vdev_spare_ops && pvd->vdev_id == 0) {
 			ASSERT(pvd->vdev_ops == &vdev_replacing_ops);
-			ASSERT(pvd->vdev_parent->vdev_children == 2);
-			pguid = pvd->vdev_parent->vdev_child[1]->vdev_guid;
+			ASSERT(ppvd->vdev_children == 2);
+			sguid = ppvd->vdev_child[1]->vdev_guid;
 		}
-		spa_config_exit(spa, SCL_CONFIG, FTAG);
-		if (spa_vdev_detach(spa, guid, B_TRUE) != 0)
+		spa_config_exit(spa, SCL_ALL, FTAG);
+		if (spa_vdev_detach(spa, guid, pguid, B_TRUE) != 0)
 			return;
-		if (pguid != 0 && spa_vdev_detach(spa, pguid, B_TRUE) != 0)
+		if (sguid && spa_vdev_detach(spa, sguid, ppguid, B_TRUE) != 0)
 			return;
-		spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
+		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	}
 
-	spa_config_exit(spa, SCL_CONFIG, FTAG);
+	spa_config_exit(spa, SCL_ALL, FTAG);
 }
 
 /*
@@ -3925,9 +3944,22 @@ spa_sync(spa_t *spa, uint64_t txg)
 	 * into config changes that go out with this transaction group.
 	 */
 	spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
-	while ((vd = list_head(&spa->spa_state_dirty_list)) != NULL) {
-		vdev_state_clean(vd);
-		vdev_config_dirty(vd);
+	while (list_head(&spa->spa_state_dirty_list) != NULL) {
+		/*
+		 * We need the write lock here because, for aux vdevs,
+		 * calling vdev_config_dirty() modifies sav_config.
+		 * This is ugly and will become unnecessary when we
+		 * eliminate the aux vdev wart by integrating all vdevs
+		 * into the root vdev tree.
+		 */
+		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
+		spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_WRITER);
+		while ((vd = list_head(&spa->spa_state_dirty_list)) != NULL) {
+			vdev_state_clean(vd);
+			vdev_config_dirty(vd);
+		}
+		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
+		spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_READER);
 	}
 	spa_config_exit(spa, SCL_STATE, FTAG);
 
diff --git a/module/zfs/spa_config.c b/module/zfs/spa_config.c
index ee425a916..252869d69 100644
--- a/module/zfs/spa_config.c
+++ b/module/zfs/spa_config.c
@@ -208,6 +208,9 @@ spa_config_sync(spa_t *target, boolean_t removing, boolean_t postsysevent)
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 
+	if (rootdir == NULL)
+		return;
+
 	/*
 	 * Iterate over all cachefiles for the pool, past or present.  When the
 	 * cachefile is changed, the new one is pushed onto this list, allowing
diff --git a/module/zfs/spa_misc.c b/module/zfs/spa_misc.c
index 36046e6df..485e83fce 100644
--- a/module/zfs/spa_misc.c
+++ b/module/zfs/spa_misc.c
@@ -230,7 +230,7 @@ static kmutex_t spa_l2cache_lock;
 static avl_tree_t spa_l2cache_avl;
 
 kmem_cache_t *spa_buffer_pool;
-int spa_mode;
+int spa_mode_global;
 
 #ifdef ZFS_DEBUG
 /* Everything except dprintf is on by default in debug builds */
@@ -880,8 +880,10 @@ spa_vdev_exit(spa_t *spa, vdev_t *vd, uint64_t txg, int error)
 		txg_wait_synced(spa->spa_dsl_pool, txg);
 
 	if (vd != NULL) {
-		ASSERT(!vd->vdev_detached || vd->vdev_dtl.smo_object == 0);
+		ASSERT(!vd->vdev_detached || vd->vdev_dtl_smo.smo_object == 0);
+		spa_config_enter(spa, SCL_ALL, spa, RW_WRITER);
 		vdev_free(vd);
+		spa_config_exit(spa, SCL_ALL, spa);
 	}
 
 	/*
@@ -912,6 +914,15 @@ spa_vdev_state_exit(spa_t *spa, vdev_t *vd, int error)
 
 	spa_config_exit(spa, SCL_STATE_ALL, spa);
 
+	/*
+	 * If anything changed, wait for it to sync.  This ensures that,
+	 * from the system administrator's perspective, zpool(1M) commands
+	 * are synchronous.  This is important for things like zpool offline:
+	 * when the command completes, you expect no further I/O from ZFS.
+	 */
+	if (vd != NULL)
+		txg_wait_synced(spa->spa_dsl_pool, 0);
+
 	return (error);
 }
 
@@ -1351,7 +1362,7 @@ spa_init(int mode)
 	avl_create(&spa_l2cache_avl, spa_l2cache_compare, sizeof (spa_aux_t),
 	    offsetof(spa_aux_t, aux_avl));
 
-	spa_mode = mode;
+	spa_mode_global = mode;
 
 	refcount_init();
 	unique_init();
@@ -1408,3 +1419,15 @@ spa_is_root(spa_t *spa)
 {
 	return (spa->spa_is_root);
 }
+
+boolean_t
+spa_writeable(spa_t *spa)
+{
+	return (!!(spa->spa_mode & FWRITE));
+}
+
+int
+spa_mode(spa_t *spa)
+{
+	return (spa->spa_mode);
+}
diff --git a/module/zfs/space_map.c b/module/zfs/space_map.c
index 0a1fd59ea..1cdacc81d 100644
--- a/module/zfs/space_map.c
+++ b/module/zfs/space_map.c
@@ -23,8 +23,6 @@
  * Use is subject to license terms.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/zfs_context.h>
 #include <sys/spa.h>
 #include <sys/dmu.h>
@@ -60,6 +58,8 @@ space_map_create(space_map_t *sm, uint64_t start, uint64_t size, uint8_t shift,
 {
 	bzero(sm, sizeof (*sm));
 
+	cv_init(&sm->sm_load_cv, NULL, CV_DEFAULT, NULL);
+
 	avl_create(&sm->sm_root, space_map_seg_compare,
 	    sizeof (space_seg_t), offsetof(struct space_seg, ss_node));
 
@@ -75,6 +75,7 @@ space_map_destroy(space_map_t *sm)
 	ASSERT(!sm->sm_loaded && !sm->sm_loading);
 	VERIFY3U(sm->sm_space, ==, 0);
 	avl_destroy(&sm->sm_root);
+	cv_destroy(&sm->sm_load_cv);
 }
 
 void
@@ -180,7 +181,7 @@ space_map_remove(space_map_t *sm, uint64_t start, uint64_t size)
 	sm->sm_space -= size;
 }
 
-int
+boolean_t
 space_map_contains(space_map_t *sm, uint64_t start, uint64_t size)
 {
 	avl_index_t where;
@@ -220,59 +221,10 @@ space_map_walk(space_map_t *sm, space_map_func_t *func, space_map_t *mdest)
 {
 	space_seg_t *ss;
 
-	for (ss = avl_first(&sm->sm_root); ss; ss = AVL_NEXT(&sm->sm_root, ss))
-		func(mdest, ss->ss_start, ss->ss_end - ss->ss_start);
-}
-
-void
-space_map_excise(space_map_t *sm, uint64_t start, uint64_t size)
-{
-	avl_tree_t *t = &sm->sm_root;
-	avl_index_t where;
-	space_seg_t *ss, search;
-	uint64_t end = start + size;
-	uint64_t rm_start, rm_end;
-
 	ASSERT(MUTEX_HELD(sm->sm_lock));
 
-	search.ss_start = start;
-	search.ss_end = start;
-
-	for (;;) {
-		ss = avl_find(t, &search, &where);
-
-		if (ss == NULL)
-			ss = avl_nearest(t, where, AVL_AFTER);
-
-		if (ss == NULL || ss->ss_start >= end)
-			break;
-
-		rm_start = MAX(ss->ss_start, start);
-		rm_end = MIN(ss->ss_end, end);
-
-		space_map_remove(sm, rm_start, rm_end - rm_start);
-	}
-}
-
-/*
- * Replace smd with the union of smd and sms.
- */
-void
-space_map_union(space_map_t *smd, space_map_t *sms)
-{
-	avl_tree_t *t = &sms->sm_root;
-	space_seg_t *ss;
-
-	ASSERT(MUTEX_HELD(smd->sm_lock));
-
-	/*
-	 * For each source segment, remove any intersections with the
-	 * destination, then add the source segment to the destination.
-	 */
-	for (ss = avl_first(t); ss != NULL; ss = AVL_NEXT(t, ss)) {
-		space_map_excise(smd, ss->ss_start, ss->ss_end - ss->ss_start);
-		space_map_add(smd, ss->ss_start, ss->ss_end - ss->ss_start);
-	}
+	for (ss = avl_first(&sm->sm_root); ss; ss = AVL_NEXT(&sm->sm_root, ss))
+		func(mdest, ss->ss_start, ss->ss_end - ss->ss_start);
 }
 
 /*
@@ -504,3 +456,131 @@ space_map_truncate(space_map_obj_t *smo, objset_t *os, dmu_tx_t *tx)
 	smo->smo_objsize = 0;
 	smo->smo_alloc = 0;
 }
+
+/*
+ * Space map reference trees.
+ *
+ * A space map is a collection of integers.  Every integer is either
+ * in the map, or it's not.  A space map reference tree generalizes
+ * the idea: it allows its members to have arbitrary reference counts,
+ * as opposed to the implicit reference count of 0 or 1 in a space map.
+ * This representation comes in handy when computing the union or
+ * intersection of multiple space maps.  For example, the union of
+ * N space maps is the subset of the reference tree with refcnt >= 1.
+ * The intersection of N space maps is the subset with refcnt >= N.
+ *
+ * [It's very much like a Fourier transform.  Unions and intersections
+ * are hard to perform in the 'space map domain', so we convert the maps
+ * into the 'reference count domain', where it's trivial, then invert.]
+ *
+ * vdev_dtl_reassess() uses computations of this form to determine
+ * DTL_MISSING and DTL_OUTAGE for interior vdevs -- e.g. a RAID-Z vdev
+ * has an outage wherever refcnt >= vdev_nparity + 1, and a mirror vdev
+ * has an outage wherever refcnt >= vdev_children.
+ */
+static int
+space_map_ref_compare(const void *x1, const void *x2)
+{
+	const space_ref_t *sr1 = x1;
+	const space_ref_t *sr2 = x2;
+
+	if (sr1->sr_offset < sr2->sr_offset)
+		return (-1);
+	if (sr1->sr_offset > sr2->sr_offset)
+		return (1);
+
+	if (sr1 < sr2)
+		return (-1);
+	if (sr1 > sr2)
+		return (1);
+
+	return (0);
+}
+
+void
+space_map_ref_create(avl_tree_t *t)
+{
+	avl_create(t, space_map_ref_compare,
+	    sizeof (space_ref_t), offsetof(space_ref_t, sr_node));
+}
+
+void
+space_map_ref_destroy(avl_tree_t *t)
+{
+	space_ref_t *sr;
+	void *cookie = NULL;
+
+	while ((sr = avl_destroy_nodes(t, &cookie)) != NULL)
+		kmem_free(sr, sizeof (*sr));
+
+	avl_destroy(t);
+}
+
+static void
+space_map_ref_add_node(avl_tree_t *t, uint64_t offset, int64_t refcnt)
+{
+	space_ref_t *sr;
+
+	sr = kmem_alloc(sizeof (*sr), KM_SLEEP);
+	sr->sr_offset = offset;
+	sr->sr_refcnt = refcnt;
+
+	avl_add(t, sr);
+}
+
+void
+space_map_ref_add_seg(avl_tree_t *t, uint64_t start, uint64_t end,
+	int64_t refcnt)
+{
+	space_map_ref_add_node(t, start, refcnt);
+	space_map_ref_add_node(t, end, -refcnt);
+}
+
+/*
+ * Convert (or add) a space map into a reference tree.
+ */
+void
+space_map_ref_add_map(avl_tree_t *t, space_map_t *sm, int64_t refcnt)
+{
+	space_seg_t *ss;
+
+	ASSERT(MUTEX_HELD(sm->sm_lock));
+
+	for (ss = avl_first(&sm->sm_root); ss; ss = AVL_NEXT(&sm->sm_root, ss))
+		space_map_ref_add_seg(t, ss->ss_start, ss->ss_end, refcnt);
+}
+
+/*
+ * Convert a reference tree into a space map.  The space map will contain
+ * all members of the reference tree for which refcnt >= minref.
+ */
+void
+space_map_ref_generate_map(avl_tree_t *t, space_map_t *sm, int64_t minref)
+{
+	uint64_t start = -1ULL;
+	int64_t refcnt = 0;
+	space_ref_t *sr;
+
+	ASSERT(MUTEX_HELD(sm->sm_lock));
+
+	space_map_vacate(sm, NULL, NULL);
+
+	for (sr = avl_first(t); sr != NULL; sr = AVL_NEXT(t, sr)) {
+		refcnt += sr->sr_refcnt;
+		if (refcnt >= minref) {
+			if (start == -1ULL) {
+				start = sr->sr_offset;
+			}
+		} else {
+			if (start != -1ULL) {
+				uint64_t end = sr->sr_offset;
+				ASSERT(start <= end);
+				if (end > start)
+					space_map_add(sm, start, end - start);
+				start = -1ULL;
+			}
+		}
+	}
+	ASSERT(refcnt == 0);
+	ASSERT(start == -1ULL);
+}
diff --git a/module/zfs/txg.c b/module/zfs/txg.c
index 2bbf2f086..e3c0e2a13 100644
--- a/module/zfs/txg.c
+++ b/module/zfs/txg.c
@@ -63,6 +63,12 @@ txg_init(dsl_pool_t *dp, uint64_t txg)
 	rw_init(&tx->tx_suspend, NULL, RW_DEFAULT, NULL);
 	mutex_init(&tx->tx_sync_lock, NULL, MUTEX_DEFAULT, NULL);
 
+	cv_init(&tx->tx_sync_more_cv, NULL, CV_DEFAULT, NULL);
+	cv_init(&tx->tx_sync_done_cv, NULL, CV_DEFAULT, NULL);
+	cv_init(&tx->tx_quiesce_more_cv, NULL, CV_DEFAULT, NULL);
+	cv_init(&tx->tx_quiesce_done_cv, NULL, CV_DEFAULT, NULL);
+	cv_init(&tx->tx_exit_cv, NULL, CV_DEFAULT, NULL);
+
 	tx->tx_open_txg = txg;
 }
 
@@ -80,6 +86,12 @@ txg_fini(dsl_pool_t *dp)
 	rw_destroy(&tx->tx_suspend);
 	mutex_destroy(&tx->tx_sync_lock);
 
+	cv_destroy(&tx->tx_sync_more_cv);
+	cv_destroy(&tx->tx_sync_done_cv);
+	cv_destroy(&tx->tx_quiesce_more_cv);
+	cv_destroy(&tx->tx_quiesce_done_cv);
+	cv_destroy(&tx->tx_exit_cv);
+
 	for (c = 0; c < max_ncpus; c++) {
 		int i;
 
diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index 16a27e514..d9689e803 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -316,8 +316,10 @@ vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
 	mutex_init(&vd->vdev_dtl_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_stat_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_probe_lock, NULL, MUTEX_DEFAULT, NULL);
-	space_map_create(&vd->vdev_dtl_map, 0, -1ULL, 0, &vd->vdev_dtl_lock);
-	space_map_create(&vd->vdev_dtl_scrub, 0, -1ULL, 0, &vd->vdev_dtl_lock);
+	for (int t = 0; t < DTL_TYPES; t++) {
+		space_map_create(&vd->vdev_dtl[t], 0, -1ULL, 0,
+		    &vd->vdev_dtl_lock);
+	}
 	txg_list_create(&vd->vdev_ms_list,
 	    offsetof(struct metaslab, ms_txg_node));
 	txg_list_create(&vd->vdev_dtl_list,
@@ -474,7 +476,7 @@ vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent, uint_t id,
 	    (alloctype == VDEV_ALLOC_LOAD || alloctype == VDEV_ALLOC_L2CACHE)) {
 		if (alloctype == VDEV_ALLOC_LOAD) {
 			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DTL,
-			    &vd->vdev_dtl.smo_object);
+			    &vd->vdev_dtl_smo.smo_object);
 			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_UNSPARE,
 			    &vd->vdev_unspare);
 		}
@@ -566,12 +568,14 @@ vdev_free(vdev_t *vd)
 
 	txg_list_destroy(&vd->vdev_ms_list);
 	txg_list_destroy(&vd->vdev_dtl_list);
+
 	mutex_enter(&vd->vdev_dtl_lock);
-	space_map_unload(&vd->vdev_dtl_map);
-	space_map_destroy(&vd->vdev_dtl_map);
-	space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
-	space_map_destroy(&vd->vdev_dtl_scrub);
+	for (int t = 0; t < DTL_TYPES; t++) {
+		space_map_unload(&vd->vdev_dtl[t]);
+		space_map_destroy(&vd->vdev_dtl[t]);
+	}
 	mutex_exit(&vd->vdev_dtl_lock);
+
 	mutex_destroy(&vd->vdev_dtl_lock);
 	mutex_destroy(&vd->vdev_stat_lock);
 	mutex_destroy(&vd->vdev_probe_lock);
@@ -709,14 +713,18 @@ vdev_remove_parent(vdev_t *cvd)
 
 	vdev_remove_child(mvd, cvd);
 	vdev_remove_child(pvd, mvd);
+
 	/*
 	 * If cvd will replace mvd as a top-level vdev, preserve mvd's guid.
 	 * Otherwise, we could have detached an offline device, and when we
 	 * go to import the pool we'll think we have two top-level vdevs,
 	 * instead of a different version of the same top-level vdev.
 	 */
-	if (mvd->vdev_top == mvd)
-		cvd->vdev_guid = cvd->vdev_guid_sum = mvd->vdev_guid;
+	if (mvd->vdev_top == mvd) {
+		uint64_t guid_delta = mvd->vdev_guid - cvd->vdev_guid;
+		cvd->vdev_guid += guid_delta;
+		cvd->vdev_guid_sum += guid_delta;
+	}
 	cvd->vdev_id = mvd->vdev_id;
 	vdev_add_child(pvd, cvd);
 	vdev_top_update(cvd->vdev_top, cvd->vdev_top);
@@ -815,6 +823,7 @@ typedef struct vdev_probe_stats {
 static void
 vdev_probe_done(zio_t *zio)
 {
+	spa_t *spa = zio->io_spa;
 	vdev_probe_stats_t *vps = zio->io_private;
 	vdev_t *vd = vps->vps_vd;
 
@@ -822,7 +831,7 @@ vdev_probe_done(zio_t *zio)
 		ASSERT(zio->io_vd == vd);
 		if (zio->io_error == 0)
 			vps->vps_readable = 1;
-		if (zio->io_error == 0 && (spa_mode & FWRITE)) {
+		if (zio->io_error == 0 && spa_writeable(spa)) {
 			zio_nowait(zio_write_phys(vps->vps_root, vd,
 			    zio->io_offset, zio->io_size, zio->io_data,
 			    ZIO_CHECKSUM_OFF, vdev_probe_done, vps,
@@ -843,12 +852,12 @@ vdev_probe_done(zio_t *zio)
 		vd->vdev_cant_write |= !vps->vps_writeable;
 
 		if (vdev_readable(vd) &&
-		    (vdev_writeable(vd) || !(spa_mode & FWRITE))) {
+		    (vdev_writeable(vd) || !spa_writeable(spa))) {
 			zio->io_error = 0;
 		} else {
 			ASSERT(zio->io_error != 0);
 			zfs_ereport_post(FM_EREPORT_ZFS_PROBE_FAILURE,
-			    zio->io_spa, vd, NULL, 0, 0);
+			    spa, vd, NULL, 0, 0);
 			zio->io_error = ENXIO;
 		}
 		kmem_free(vps, sizeof (*vps));
@@ -916,12 +925,15 @@ vdev_probe(vdev_t *vd, zio_t *pio)
 int
 vdev_open(vdev_t *vd)
 {
+	spa_t *spa = vd->vdev_spa;
 	int error;
 	int c;
 	uint64_t osize = 0;
 	uint64_t asize, psize;
 	uint64_t ashift = 0;
 
+	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
+
 	ASSERT(vd->vdev_state == VDEV_STATE_CLOSED ||
 	    vd->vdev_state == VDEV_STATE_CANT_OPEN ||
 	    vd->vdev_state == VDEV_STATE_OFFLINE);
@@ -1055,16 +1067,12 @@ vdev_open(vdev_t *vd)
 
 	/*
 	 * If a leaf vdev has a DTL, and seems healthy, then kick off a
-	 * resilver.  But don't do this if we are doing a reopen for a
-	 * scrub, since this would just restart the scrub we are already
-	 * doing.
+	 * resilver.  But don't do this if we are doing a reopen for a scrub,
+	 * since this would just restart the scrub we are already doing.
 	 */
-	if (vd->vdev_children == 0 && !vd->vdev_spa->spa_scrub_reopen) {
-		mutex_enter(&vd->vdev_dtl_lock);
-		if (vd->vdev_dtl_map.sm_space != 0 && vdev_writeable(vd))
-			spa_async_request(vd->vdev_spa, SPA_ASYNC_RESILVER);
-		mutex_exit(&vd->vdev_dtl_lock);
-	}
+	if (vd->vdev_ops->vdev_op_leaf && !spa->spa_scrub_reopen &&
+	    vdev_resilver_needed(vd, NULL, NULL))
+		spa_async_request(spa, SPA_ASYNC_RESILVER);
 
 	return (0);
 }
@@ -1165,6 +1173,10 @@ vdev_validate(vdev_t *vd)
 void
 vdev_close(vdev_t *vd)
 {
+	spa_t *spa = vd->vdev_spa;
+
+	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
+
 	vd->vdev_ops->vdev_op_close(vd);
 
 	vdev_cache_purge(vd);
@@ -1283,34 +1295,88 @@ vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg)
 	(void) txg_list_add(&vd->vdev_spa->spa_vdev_txg_list, vd, txg);
 }
 
+/*
+ * DTLs.
+ *
+ * A vdev's DTL (dirty time log) is the set of transaction groups for which
+ * the vdev has less than perfect replication.  There are three kinds of DTL:
+ *
+ * DTL_MISSING: txgs for which the vdev has no valid copies of the data
+ *
+ * DTL_PARTIAL: txgs for which data is available, but not fully replicated
+ *
+ * DTL_SCRUB: the txgs that could not be repaired by the last scrub; upon
+ *	scrub completion, DTL_SCRUB replaces DTL_MISSING in the range of
+ *	txgs that was scrubbed.
+ *
+ * DTL_OUTAGE: txgs which cannot currently be read, whether due to
+ *	persistent errors or just some device being offline.
+ *	Unlike the other three, the DTL_OUTAGE map is not generally
+ *	maintained; it's only computed when needed, typically to
+ *	determine whether a device can be detached.
+ *
+ * For leaf vdevs, DTL_MISSING and DTL_PARTIAL are identical: the device
+ * either has the data or it doesn't.
+ *
+ * For interior vdevs such as mirror and RAID-Z the picture is more complex.
+ * A vdev's DTL_PARTIAL is the union of its children's DTL_PARTIALs, because
+ * if any child is less than fully replicated, then so is its parent.
+ * A vdev's DTL_MISSING is a modified union of its children's DTL_MISSINGs,
+ * comprising only those txgs which appear in 'maxfaults' or more children;
+ * those are the txgs we don't have enough replication to read.  For example,
+ * double-parity RAID-Z can tolerate up to two missing devices (maxfaults == 2);
+ * thus, its DTL_MISSING consists of the set of txgs that appear in more than
+ * two child DTL_MISSING maps.
+ *
+ * It should be clear from the above that to compute the DTLs and outage maps
+ * for all vdevs, it suffices to know just the leaf vdevs' DTL_MISSING maps.
+ * Therefore, that is all we keep on disk.  When loading the pool, or after
+ * a configuration change, we generate all other DTLs from first principles.
+ */
 void
-vdev_dtl_dirty(space_map_t *sm, uint64_t txg, uint64_t size)
+vdev_dtl_dirty(vdev_t *vd, vdev_dtl_type_t t, uint64_t txg, uint64_t size)
 {
+	space_map_t *sm = &vd->vdev_dtl[t];
+
+	ASSERT(t < DTL_TYPES);
+	ASSERT(vd != vd->vdev_spa->spa_root_vdev);
+
 	mutex_enter(sm->sm_lock);
 	if (!space_map_contains(sm, txg, size))
 		space_map_add(sm, txg, size);
 	mutex_exit(sm->sm_lock);
 }
 
-int
-vdev_dtl_contains(space_map_t *sm, uint64_t txg, uint64_t size)
+boolean_t
+vdev_dtl_contains(vdev_t *vd, vdev_dtl_type_t t, uint64_t txg, uint64_t size)
 {
-	int dirty;
+	space_map_t *sm = &vd->vdev_dtl[t];
+	boolean_t dirty = B_FALSE;
 
-	/*
-	 * Quick test without the lock -- covers the common case that
-	 * there are no dirty time segments.
-	 */
-	if (sm->sm_space == 0)
-		return (0);
+	ASSERT(t < DTL_TYPES);
+	ASSERT(vd != vd->vdev_spa->spa_root_vdev);
 
 	mutex_enter(sm->sm_lock);
-	dirty = space_map_contains(sm, txg, size);
+	if (sm->sm_space != 0)
+		dirty = space_map_contains(sm, txg, size);
 	mutex_exit(sm->sm_lock);
 
 	return (dirty);
 }
 
+boolean_t
+vdev_dtl_empty(vdev_t *vd, vdev_dtl_type_t t)
+{
+	space_map_t *sm = &vd->vdev_dtl[t];
+	boolean_t empty;
+
+	mutex_enter(sm->sm_lock);
+	empty = (sm->sm_space == 0);
+	mutex_exit(sm->sm_lock);
+
+	return (empty);
+}
+
 /*
  * Reassess DTLs after a config change or scrub completion.
  */
@@ -1318,11 +1384,19 @@ void
 vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg, int scrub_done)
 {
 	spa_t *spa = vd->vdev_spa;
-	int c;
+	avl_tree_t reftree;
+	int minref;
 
-	ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));
+	ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
 
-	if (vd->vdev_children == 0) {
+	for (int c = 0; c < vd->vdev_children; c++)
+		vdev_dtl_reassess(vd->vdev_child[c], txg,
+		    scrub_txg, scrub_done);
+
+	if (vd == spa->spa_root_vdev)
+		return;
+
+	if (vd->vdev_ops->vdev_op_leaf) {
 		mutex_enter(&vd->vdev_dtl_lock);
 		if (scrub_txg != 0 &&
 		    (spa->spa_scrub_started || spa->spa_scrub_errors == 0)) {
@@ -1333,12 +1407,38 @@ vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg, int scrub_done)
 			 * will be valid, so excise the old region and
 			 * fold in the scrub dtl.  Otherwise, leave the
 			 * dtl as-is if there was an error.
+			 *
+			 * There's little trick here: to excise the beginning
+			 * of the DTL_MISSING map, we put it into a reference
+			 * tree and then add a segment with refcnt -1 that
+			 * covers the range [0, scrub_txg).  This means
+			 * that each txg in that range has refcnt -1 or 0.
+			 * We then add DTL_SCRUB with a refcnt of 2, so that
+			 * entries in the range [0, scrub_txg) will have a
+			 * positive refcnt -- either 1 or 2.  We then convert
+			 * the reference tree into the new DTL_MISSING map.
 			 */
-			space_map_excise(&vd->vdev_dtl_map, 0, scrub_txg);
-			space_map_union(&vd->vdev_dtl_map, &vd->vdev_dtl_scrub);
+			space_map_ref_create(&reftree);
+			space_map_ref_add_map(&reftree,
+			    &vd->vdev_dtl[DTL_MISSING], 1);
+			space_map_ref_add_seg(&reftree, 0, scrub_txg, -1);
+			space_map_ref_add_map(&reftree,
+			    &vd->vdev_dtl[DTL_SCRUB], 2);
+			space_map_ref_generate_map(&reftree,
+			    &vd->vdev_dtl[DTL_MISSING], 1);
+			space_map_ref_destroy(&reftree);
 		}
+		space_map_vacate(&vd->vdev_dtl[DTL_PARTIAL], NULL, NULL);
+		space_map_walk(&vd->vdev_dtl[DTL_MISSING],
+		    space_map_add, &vd->vdev_dtl[DTL_PARTIAL]);
 		if (scrub_done)
-			space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
+			space_map_vacate(&vd->vdev_dtl[DTL_SCRUB], NULL, NULL);
+		space_map_vacate(&vd->vdev_dtl[DTL_OUTAGE], NULL, NULL);
+		if (!vdev_readable(vd))
+			space_map_add(&vd->vdev_dtl[DTL_OUTAGE], 0, -1ULL);
+		else
+			space_map_walk(&vd->vdev_dtl[DTL_MISSING],
+			    space_map_add, &vd->vdev_dtl[DTL_OUTAGE]);
 		mutex_exit(&vd->vdev_dtl_lock);
 
 		if (txg != 0)
@@ -1346,35 +1446,34 @@ vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg, int scrub_done)
 		return;
 	}
 
-	/*
-	 * Make sure the DTLs are always correct under the scrub lock.
-	 */
-	if (vd == spa->spa_root_vdev)
-		mutex_enter(&spa->spa_scrub_lock);
-
 	mutex_enter(&vd->vdev_dtl_lock);
-	space_map_vacate(&vd->vdev_dtl_map, NULL, NULL);
-	space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
-	mutex_exit(&vd->vdev_dtl_lock);
-
-	for (c = 0; c < vd->vdev_children; c++) {
-		vdev_t *cvd = vd->vdev_child[c];
-		vdev_dtl_reassess(cvd, txg, scrub_txg, scrub_done);
-		mutex_enter(&vd->vdev_dtl_lock);
-		space_map_union(&vd->vdev_dtl_map, &cvd->vdev_dtl_map);
-		space_map_union(&vd->vdev_dtl_scrub, &cvd->vdev_dtl_scrub);
-		mutex_exit(&vd->vdev_dtl_lock);
+	for (int t = 0; t < DTL_TYPES; t++) {
+		if (t == DTL_SCRUB)
+			continue;			/* leaf vdevs only */
+		if (t == DTL_PARTIAL)
+			minref = 1;			/* i.e. non-zero */
+		else if (vd->vdev_nparity != 0)
+			minref = vd->vdev_nparity + 1;	/* RAID-Z */
+		else
+			minref = vd->vdev_children;	/* any kind of mirror */
+		space_map_ref_create(&reftree);
+		for (int c = 0; c < vd->vdev_children; c++) {
+			vdev_t *cvd = vd->vdev_child[c];
+			mutex_enter(&cvd->vdev_dtl_lock);
+			space_map_ref_add_map(&reftree, &cvd->vdev_dtl[t], 1);
+			mutex_exit(&cvd->vdev_dtl_lock);
+		}
+		space_map_ref_generate_map(&reftree, &vd->vdev_dtl[t], minref);
+		space_map_ref_destroy(&reftree);
 	}
-
-	if (vd == spa->spa_root_vdev)
-		mutex_exit(&spa->spa_scrub_lock);
+	mutex_exit(&vd->vdev_dtl_lock);
 }
 
 static int
 vdev_dtl_load(vdev_t *vd)
 {
 	spa_t *spa = vd->vdev_spa;
-	space_map_obj_t *smo = &vd->vdev_dtl;
+	space_map_obj_t *smo = &vd->vdev_dtl_smo;
 	objset_t *mos = spa->spa_meta_objset;
 	dmu_buf_t *db;
 	int error;
@@ -1392,7 +1491,8 @@ vdev_dtl_load(vdev_t *vd)
 	dmu_buf_rele(db, FTAG);
 
 	mutex_enter(&vd->vdev_dtl_lock);
-	error = space_map_load(&vd->vdev_dtl_map, NULL, SM_ALLOC, smo, mos);
+	error = space_map_load(&vd->vdev_dtl[DTL_MISSING],
+	    NULL, SM_ALLOC, smo, mos);
 	mutex_exit(&vd->vdev_dtl_lock);
 
 	return (error);
@@ -1402,8 +1502,8 @@ void
 vdev_dtl_sync(vdev_t *vd, uint64_t txg)
 {
 	spa_t *spa = vd->vdev_spa;
-	space_map_obj_t *smo = &vd->vdev_dtl;
-	space_map_t *sm = &vd->vdev_dtl_map;
+	space_map_obj_t *smo = &vd->vdev_dtl_smo;
+	space_map_t *sm = &vd->vdev_dtl[DTL_MISSING];
 	objset_t *mos = spa->spa_meta_objset;
 	space_map_t smsync;
 	kmutex_t smlock;
@@ -1461,6 +1561,37 @@ vdev_dtl_sync(vdev_t *vd, uint64_t txg)
 }
 
 /*
+ * Determine whether the specified vdev can be offlined/detached/removed
+ * without losing data.
+ */
+boolean_t
+vdev_dtl_required(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+	vdev_t *tvd = vd->vdev_top;
+	uint8_t cant_read = vd->vdev_cant_read;
+	boolean_t required;
+
+	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
+
+	if (vd == spa->spa_root_vdev || vd == tvd)
+		return (B_TRUE);
+
+	/*
+	 * Temporarily mark the device as unreadable, and then determine
+	 * whether this results in any DTL outages in the top-level vdev.
+	 * If not, we can safely offline/detach/remove the device.
+	 */
+	vd->vdev_cant_read = B_TRUE;
+	vdev_dtl_reassess(tvd, 0, 0, B_FALSE);
+	required = !vdev_dtl_empty(tvd, DTL_OUTAGE);
+	vd->vdev_cant_read = cant_read;
+	vdev_dtl_reassess(tvd, 0, 0, B_FALSE);
+
+	return (required);
+}
+
+/*
  * Determine if resilver is needed, and if so the txg range.
  */
 boolean_t
@@ -1472,19 +1603,19 @@ vdev_resilver_needed(vdev_t *vd, uint64_t *minp, uint64_t *maxp)
 
 	if (vd->vdev_children == 0) {
 		mutex_enter(&vd->vdev_dtl_lock);
-		if (vd->vdev_dtl_map.sm_space != 0 && vdev_writeable(vd)) {
+		if (vd->vdev_dtl[DTL_MISSING].sm_space != 0 &&
+		    vdev_writeable(vd)) {
 			space_seg_t *ss;
 
-			ss = avl_first(&vd->vdev_dtl_map.sm_root);
+			ss = avl_first(&vd->vdev_dtl[DTL_MISSING].sm_root);
 			thismin = ss->ss_start - 1;
-			ss = avl_last(&vd->vdev_dtl_map.sm_root);
+			ss = avl_last(&vd->vdev_dtl[DTL_MISSING].sm_root);
 			thismax = ss->ss_end;
 			needed = B_TRUE;
 		}
 		mutex_exit(&vd->vdev_dtl_lock);
 	} else {
-		int c;
-		for (c = 0; c < vd->vdev_children; c++) {
+		for (int c = 0; c < vd->vdev_children; c++) {
 			vdev_t *cvd = vd->vdev_child[c];
 			uint64_t cmin, cmax;
 
@@ -1506,12 +1637,10 @@ vdev_resilver_needed(vdev_t *vd, uint64_t *minp, uint64_t *maxp)
 void
 vdev_load(vdev_t *vd)
 {
-	int c;
-
 	/*
 	 * Recursively load all children.
 	 */
-	for (c = 0; c < vd->vdev_children; c++)
+	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_load(vd->vdev_child[c]);
 
 	/*
@@ -1731,11 +1860,7 @@ vdev_online(spa_t *spa, uint64_t guid, uint64_t flags, vdev_state_t *newstate)
 	    vd->vdev_parent->vdev_child[0] == vd)
 		vd->vdev_unspare = B_TRUE;
 
-	(void) spa_vdev_state_exit(spa, vd, 0);
-
-	VERIFY3U(spa_scrub(spa, POOL_SCRUB_RESILVER), ==, 0);
-
-	return (0);
+	return (spa_vdev_state_exit(spa, vd, 0));
 }
 
 int
@@ -1756,13 +1881,10 @@ vdev_offline(spa_t *spa, uint64_t guid, uint64_t flags)
 	 */
 	if (!vd->vdev_offline) {
 		/*
-		 * If this device's top-level vdev has a non-empty DTL,
-		 * don't allow the device to be offlined.
-		 *
-		 * XXX -- make this more precise by allowing the offline
-		 * as long as the remaining devices don't have any DTL holes.
+		 * If this device has the only valid copy of some data,
+		 * don't allow it to be offlined.
 		 */
-		if (vd->vdev_top->vdev_dtl_map.sm_space != 0)
+		if (vd->vdev_aux == NULL && vdev_dtl_required(vd))
 			return (spa_vdev_state_exit(spa, NULL, EBUSY));
 
 		/*
@@ -1772,7 +1894,7 @@ vdev_offline(spa_t *spa, uint64_t guid, uint64_t flags)
 		 */
 		vd->vdev_offline = B_TRUE;
 		vdev_reopen(vd->vdev_top);
-		if (vdev_is_dead(vd->vdev_top) && vd->vdev_aux == NULL) {
+		if (vd->vdev_aux == NULL && vdev_is_dead(vd->vdev_top)) {
 			vd->vdev_offline = B_FALSE;
 			vdev_reopen(vd->vdev_top);
 			return (spa_vdev_state_exit(spa, NULL, EBUSY));
@@ -1852,13 +1974,17 @@ vdev_writeable(vdev_t *vd)
 boolean_t
 vdev_allocatable(vdev_t *vd)
 {
+	uint64_t state = vd->vdev_state;
+
 	/*
-	 * We currently allow allocations from vdevs which maybe in the
+	 * We currently allow allocations from vdevs which may be in the
 	 * process of reopening (i.e. VDEV_STATE_CLOSED). If the device
 	 * fails to reopen then we'll catch it later when we're holding
-	 * the proper locks.
+	 * the proper locks.  Note that we have to get the vdev state
+	 * in a local variable because although it changes atomically,
+	 * we're asking two separate questions about it.
 	 */
-	return (!(vdev_is_dead(vd) && vd->vdev_state != VDEV_STATE_CLOSED) &&
+	return (!(state < VDEV_STATE_DEGRADED && state != VDEV_STATE_CLOSED) &&
 	    !vd->vdev_cant_write);
 }
 
@@ -1928,7 +2054,8 @@ vdev_clear_stats(vdev_t *vd)
 void
 vdev_stat_update(zio_t *zio, uint64_t psize)
 {
-	vdev_t *rvd = zio->io_spa->spa_root_vdev;
+	spa_t *spa = zio->io_spa;
+	vdev_t *rvd = spa->spa_root_vdev;
 	vdev_t *vd = zio->io_vd ? zio->io_vd : rvd;
 	vdev_t *pvd;
 	uint64_t txg = zio->io_txg;
@@ -1961,21 +2088,23 @@ vdev_stat_update(zio_t *zio, uint64_t psize)
 			return;
 
 		ASSERT(vd == zio->io_vd);
-		if (!(flags & ZIO_FLAG_IO_BYPASS)) {
-			mutex_enter(&vd->vdev_stat_lock);
-			vs->vs_ops[type]++;
-			vs->vs_bytes[type] += psize;
-			mutex_exit(&vd->vdev_stat_lock);
-		}
+
+		if (flags & ZIO_FLAG_IO_BYPASS)
+			return;
+
+		mutex_enter(&vd->vdev_stat_lock);
+
 		if (flags & ZIO_FLAG_IO_REPAIR) {
-			ASSERT(zio->io_delegate_list == NULL);
-			mutex_enter(&vd->vdev_stat_lock);
 			if (flags & ZIO_FLAG_SCRUB_THREAD)
 				vs->vs_scrub_repaired += psize;
-			else
+			if (flags & ZIO_FLAG_SELF_HEAL)
 				vs->vs_self_healed += psize;
-			mutex_exit(&vd->vdev_stat_lock);
 		}
+
+		vs->vs_ops[type]++;
+		vs->vs_bytes[type] += psize;
+
+		mutex_exit(&vd->vdev_stat_lock);
 		return;
 	}
 
@@ -1993,19 +2122,39 @@ vdev_stat_update(zio_t *zio, uint64_t psize)
 		vs->vs_write_errors++;
 	mutex_exit(&vd->vdev_stat_lock);
 
-	if (type == ZIO_TYPE_WRITE && txg != 0 && vd->vdev_children == 0) {
-		if (flags & ZIO_FLAG_SCRUB_THREAD) {
-			ASSERT(flags & ZIO_FLAG_IO_REPAIR);
-			for (pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
-				vdev_dtl_dirty(&pvd->vdev_dtl_scrub, txg, 1);
-		}
-		if (!(flags & ZIO_FLAG_IO_REPAIR)) {
-			if (vdev_dtl_contains(&vd->vdev_dtl_map, txg, 1))
+	if (type == ZIO_TYPE_WRITE && txg != 0 &&
+	    (!(flags & ZIO_FLAG_IO_REPAIR) ||
+	    (flags & ZIO_FLAG_SCRUB_THREAD))) {
+		/*
+		 * This is either a normal write (not a repair), or it's a
+		 * repair induced by the scrub thread.  In the normal case,
+		 * we commit the DTL change in the same txg as the block
+		 * was born.  In the scrub-induced repair case, we know that
+		 * scrubs run in first-pass syncing context, so we commit
+		 * the DTL change in spa->spa_syncing_txg.
+		 *
+		 * We currently do not make DTL entries for failed spontaneous
+		 * self-healing writes triggered by normal (non-scrubbing)
+		 * reads, because we have no transactional context in which to
+		 * do so -- and it's not clear that it'd be desirable anyway.
+		 */
+		if (vd->vdev_ops->vdev_op_leaf) {
+			uint64_t commit_txg = txg;
+			if (flags & ZIO_FLAG_SCRUB_THREAD) {
+				ASSERT(flags & ZIO_FLAG_IO_REPAIR);
+				ASSERT(spa_sync_pass(spa) == 1);
+				vdev_dtl_dirty(vd, DTL_SCRUB, txg, 1);
+				commit_txg = spa->spa_syncing_txg;
+			}
+			ASSERT(commit_txg >= spa->spa_syncing_txg);
+			if (vdev_dtl_contains(vd, DTL_MISSING, txg, 1))
 				return;
-			vdev_dirty(vd->vdev_top, VDD_DTL, vd, txg);
-			for (pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
-				vdev_dtl_dirty(&pvd->vdev_dtl_map, txg, 1);
+			for (pvd = vd; pvd != rvd; pvd = pvd->vdev_parent)
+				vdev_dtl_dirty(pvd, DTL_PARTIAL, txg, 1);
+			vdev_dirty(vd->vdev_top, VDD_DTL, vd, commit_txg);
 		}
+		if (vd != rvd)
+			vdev_dtl_dirty(vd, DTL_MISSING, txg, 1);
 	}
 }
 
@@ -2218,7 +2367,8 @@ vdev_state_clean(vdev_t *vd)
 void
 vdev_propagate_state(vdev_t *vd)
 {
-	vdev_t *rvd = vd->vdev_spa->spa_root_vdev;
+	spa_t *spa = vd->vdev_spa;
+	vdev_t *rvd = spa->spa_root_vdev;
 	int degraded = 0, faulted = 0;
 	int corrupted = 0;
 	int c;
@@ -2229,7 +2379,7 @@ vdev_propagate_state(vdev_t *vd)
 			child = vd->vdev_child[c];
 
 			if (!vdev_readable(child) ||
-			    (!vdev_writeable(child) && (spa_mode & FWRITE))) {
+			    (!vdev_writeable(child) && spa_writeable(spa))) {
 				/*
 				 * Root special: if there is a top-level log
 				 * device, treat the root vdev as if it were
diff --git a/module/zfs/vdev_file.c b/module/zfs/vdev_file.c
index dc0e920bf..f91dddbe5 100644
--- a/module/zfs/vdev_file.c
+++ b/module/zfs/vdev_file.c
@@ -61,7 +61,7 @@ vdev_file_open(vdev_t *vd, uint64_t *psize, uint64_t *ashift)
 	 */
 	ASSERT(vd->vdev_path != NULL && vd->vdev_path[0] == '/');
 	error = vn_openat(vd->vdev_path + 1, UIO_SYSSPACE,
-	    spa_mode | FOFFMAX, 0, &vp, 0, 0, rootdir, -1);
+	    spa_mode(vd->vdev_spa) | FOFFMAX, 0, &vp, 0, 0, rootdir, -1);
 
 	if (error) {
 		vd->vdev_stat.vs_aux = VDEV_AUX_OPEN_FAILED;
@@ -105,7 +105,8 @@ vdev_file_close(vdev_t *vd)
 
 	if (vf->vf_vnode != NULL) {
 		(void) VOP_PUTPAGE(vf->vf_vnode, 0, 0, B_INVAL, kcred, NULL);
-		(void) VOP_CLOSE(vf->vf_vnode, spa_mode, 1, 0, kcred, NULL);
+		(void) VOP_CLOSE(vf->vf_vnode, spa_mode(vd->vdev_spa), 1, 0,
+		    kcred, NULL);
 		VN_RELE(vf->vf_vnode);
 	}
 
diff --git a/module/zfs/vdev_label.c b/module/zfs/vdev_label.c
index bf930466f..f8f90196b 100644
--- a/module/zfs/vdev_label.c
+++ b/module/zfs/vdev_label.c
@@ -277,9 +277,9 @@ vdev_config_generate(spa_t *spa, vdev_t *vd, boolean_t getstats,
 		    vd->vdev_islog) == 0);
 	}
 
-	if (vd->vdev_dtl.smo_object != 0)
+	if (vd->vdev_dtl_smo.smo_object != 0)
 		VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_DTL,
-		    vd->vdev_dtl.smo_object) == 0);
+		    vd->vdev_dtl_smo.smo_object) == 0);
 
 	if (getstats) {
 		vdev_stat_t vs;
@@ -520,9 +520,6 @@ vdev_label_init(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason)
 	    vdev_inuse(vd, crtxg, reason, &spare_guid, &l2cache_guid))
 		return (EBUSY);
 
-	ASSERT(reason != VDEV_LABEL_REMOVE ||
-	    vdev_inuse(vd, crtxg, reason, NULL, NULL));
-
 	/*
 	 * If this is a request to add or replace a spare or l2cache device
 	 * that is in use elsewhere on the system, then we must update the
@@ -705,6 +702,11 @@ vdev_label_init(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason)
  */
 
 /*
+ * For use by zdb and debugging purposes only
+ */
+uint64_t ub_max_txg = UINT64_MAX;
+
+/*
  * Consider the following situation: txg is safely synced to disk.  We've
  * written the first uberblock for txg + 1, and then we lose power.  When we
  * come back up, we fail to see the uberblock for txg + 1 because, say,
@@ -741,7 +743,8 @@ vdev_uberblock_load_done(zio_t *zio)
 
 	if (zio->io_error == 0 && uberblock_verify(ub) == 0) {
 		mutex_enter(&rio->io_lock);
-		if (vdev_uberblock_compare(ub, ubbest) > 0)
+		if (ub->ub_txg <= ub_max_txg &&
+		    vdev_uberblock_compare(ub, ubbest) > 0)
 			*ubbest = *ub;
 		mutex_exit(&rio->io_lock);
 	}
diff --git a/module/zfs/vdev_mirror.c b/module/zfs/vdev_mirror.c
index c4629ff45..184da82ab 100644
--- a/module/zfs/vdev_mirror.c
+++ b/module/zfs/vdev_mirror.c
@@ -225,7 +225,7 @@ vdev_mirror_child_select(zio_t *zio)
 			mc->mc_skipped = 1;
 			continue;
 		}
-		if (!vdev_dtl_contains(&mc->mc_vd->vdev_dtl_map, txg, 1))
+		if (!vdev_dtl_contains(mc->mc_vd, DTL_MISSING, txg, 1))
 			return (c);
 		mc->mc_error = ESTALE;
 		mc->mc_skipped = 1;
@@ -282,20 +282,10 @@ vdev_mirror_io_start(zio_t *zio)
 		ASSERT(zio->io_type == ZIO_TYPE_WRITE);
 
 		/*
-		 * If this is a resilvering I/O to a replacing vdev,
-		 * only the last child should be written -- unless the
-		 * first child happens to have a DTL entry here as well.
-		 * All other writes go to all children.
+		 * Writes go to all children.
 		 */
-		if ((zio->io_flags & ZIO_FLAG_RESILVER) && mm->mm_replacing &&
-		    !vdev_dtl_contains(&mm->mm_child[0].mc_vd->vdev_dtl_map,
-		    zio->io_txg, 1)) {
-			c = mm->mm_children - 1;
-			children = 1;
-		} else {
-			c = 0;
-			children = mm->mm_children;
-		}
+		c = 0;
+		children = mm->mm_children;
 	}
 
 	while (children--) {
@@ -398,7 +388,7 @@ vdev_mirror_io_done(zio_t *zio)
 		ASSERT(zio->io_error != 0);
 	}
 
-	if (good_copies && (spa_mode & FWRITE) &&
+	if (good_copies && spa_writeable(zio->io_spa) &&
 	    (unexpected_errors ||
 	    (zio->io_flags & ZIO_FLAG_RESILVER) ||
 	    ((zio->io_flags & ZIO_FLAG_SCRUB) && mm->mm_replacing))) {
@@ -419,7 +409,7 @@ vdev_mirror_io_done(zio_t *zio)
 				if (mc->mc_tried)
 					continue;
 				if (!(zio->io_flags & ZIO_FLAG_SCRUB) &&
-				    !vdev_dtl_contains(&mc->mc_vd->vdev_dtl_map,
+				    !vdev_dtl_contains(mc->mc_vd, DTL_PARTIAL,
 				    zio->io_txg, 1))
 					continue;
 				mc->mc_error = ESTALE;
@@ -429,7 +419,8 @@ vdev_mirror_io_done(zio_t *zio)
 			    mc->mc_vd, mc->mc_offset,
 			    zio->io_data, zio->io_size,
 			    ZIO_TYPE_WRITE, zio->io_priority,
-			    ZIO_FLAG_IO_REPAIR, NULL, NULL));
+			    ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
+			    ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
 		}
 	}
 }
diff --git a/module/zfs/vdev_queue.c b/module/zfs/vdev_queue.c
index 46fca0e3b..137afdd42 100644
--- a/module/zfs/vdev_queue.c
+++ b/module/zfs/vdev_queue.c
@@ -176,6 +176,7 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 	zio_t *fio, *lio, *aio, *dio;
 	avl_tree_t *tree;
 	uint64_t size;
+	int flags;
 
 	ASSERT(MUTEX_HELD(&vq->vq_lock));
 
@@ -187,21 +188,32 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 
 	tree = fio->io_vdev_tree;
 	size = fio->io_size;
-
-	while ((dio = AVL_PREV(tree, fio)) != NULL && IS_ADJACENT(dio, fio) &&
-	    !((dio->io_flags | fio->io_flags) & ZIO_FLAG_DONT_AGGREGATE) &&
-	    size + dio->io_size <= zfs_vdev_aggregation_limit) {
-		dio->io_delegate_next = fio;
-		fio = dio;
-		size += dio->io_size;
-	}
-
-	while ((dio = AVL_NEXT(tree, lio)) != NULL && IS_ADJACENT(lio, dio) &&
-	    !((lio->io_flags | dio->io_flags) & ZIO_FLAG_DONT_AGGREGATE) &&
-	    size + dio->io_size <= zfs_vdev_aggregation_limit) {
-		lio->io_delegate_next = dio;
-		lio = dio;
-		size += dio->io_size;
+	flags = fio->io_flags & ZIO_FLAG_AGG_INHERIT;
+
+	if (!(flags & ZIO_FLAG_DONT_AGGREGATE)) {
+		/*
+		 * We can aggregate I/Os that are adjacent and of the
+		 * same flavor, as expressed by the AGG_INHERIT flags.
+		 * The latter is necessary so that certain attributes
+		 * of the I/O, such as whether it's a normal I/O or a
+		 * scrub/resilver, can be preserved in the aggregate.
+		 */
+		while ((dio = AVL_PREV(tree, fio)) != NULL &&
+		    IS_ADJACENT(dio, fio) &&
+		    (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
+		    size + dio->io_size <= zfs_vdev_aggregation_limit) {
+			dio->io_delegate_next = fio;
+			fio = dio;
+			size += dio->io_size;
+		}
+		while ((dio = AVL_NEXT(tree, lio)) != NULL &&
+		    IS_ADJACENT(lio, dio) &&
+		    (dio->io_flags & ZIO_FLAG_AGG_INHERIT) == flags &&
+		    size + dio->io_size <= zfs_vdev_aggregation_limit) {
+			lio->io_delegate_next = dio;
+			lio = dio;
+			size += dio->io_size;
+		}
 	}
 
 	if (fio != lio) {
@@ -212,7 +224,7 @@ vdev_queue_io_to_issue(vdev_queue_t *vq, uint64_t pending_limit)
 
 		aio = zio_vdev_delegated_io(fio->io_vd, fio->io_offset,
 		    buf, size, fio->io_type, ZIO_PRIORITY_NOW,
-		    ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
+		    flags | ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_QUEUE,
 		    vdev_queue_agg_io_done, NULL);
 
 		aio->io_delegate_list = fio;
diff --git a/module/zfs/vdev_raidz.c b/module/zfs/vdev_raidz.c
index 69e314468..ad997f528 100644
--- a/module/zfs/vdev_raidz.c
+++ b/module/zfs/vdev_raidz.c
@@ -687,7 +687,7 @@ vdev_raidz_io_start(zio_t *zio)
 			rc->rc_skipped = 1;
 			continue;
 		}
-		if (vdev_dtl_contains(&cvd->vdev_dtl_map, bp->blk_birth, 1)) {
+		if (vdev_dtl_contains(cvd, DTL_MISSING, bp->blk_birth, 1)) {
 			if (c >= rm->rm_firstdatacol)
 				rm->rm_missingdata++;
 			else
@@ -1165,7 +1165,7 @@ vdev_raidz_io_done(zio_t *zio)
 done:
 	zio_checksum_verified(zio);
 
-	if (zio->io_error == 0 && (spa_mode & FWRITE) &&
+	if (zio->io_error == 0 && spa_writeable(zio->io_spa) &&
 	    (unexpected_errors || (zio->io_flags & ZIO_FLAG_RESILVER))) {
 		/*
 		 * Use the good data we have in hand to repair damaged children.
@@ -1180,7 +1180,8 @@ done:
 			zio_nowait(zio_vdev_child_io(zio, NULL, cvd,
 			    rc->rc_offset, rc->rc_data, rc->rc_size,
 			    ZIO_TYPE_WRITE, zio->io_priority,
-			    ZIO_FLAG_IO_REPAIR, NULL, NULL));
+			    ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
+			    ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
 		}
 	}
 }
diff --git a/module/zfs/zfs_acl.c b/module/zfs/zfs_acl.c
index 341dc4dfe..fdf92a156 100644
--- a/module/zfs/zfs_acl.c
+++ b/module/zfs/zfs_acl.c
@@ -2148,12 +2148,12 @@ top:
 		}
 	}
 
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		mutex_exit(&zp->z_acl_lock);
 		mutex_exit(&zp->z_lock);
 
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -2208,7 +2208,7 @@ zfs_zaccess_common(znode_t *zp, uint32_t v4_mode, uint32_t *working_mode,
 
 	*check_privs = B_TRUE;
 
-	if (zfsvfs->z_assign >= TXG_INITIAL) {		/* ZIL replay */
+	if (zfsvfs->z_replay) {
 		*working_mode = 0;
 		return (0);
 	}
diff --git a/module/zfs/zfs_byteswap.c b/module/zfs/zfs_byteswap.c
index ab97f83eb..cd36696f9 100644
--- a/module/zfs/zfs_byteswap.c
+++ b/module/zfs/zfs_byteswap.c
@@ -19,12 +19,10 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
 #include <sys/zfs_context.h>
 #include <sys/vfs.h>
 #include <sys/fs/zfs.h>
@@ -63,6 +61,20 @@ zfs_ace_byteswap(void *buf, size_t size, boolean_t zfs_layout)
 
 	while (ptr < end) {
 		if (zfs_layout) {
+			/*
+			 * Avoid overrun.  Embedded aces can have one
+			 * of several sizes.  We don't know exactly
+			 * how many our present, only the size of the
+			 * buffer containing them.  That size may be
+			 * larger than needed to hold the aces
+			 * present.  As long as we do not do any
+			 * swapping beyond the end of our block we are
+			 * okay.  It it safe to swap any non-ace data
+			 * within the block since it is just zeros.
+			 */
+			if (ptr + sizeof (zfs_ace_hdr_t) > end) {
+				break;
+			}
 			zacep = (zfs_ace_t *)ptr;
 			zacep->z_hdr.z_access_mask =
 			    BSWAP_32(zacep->z_hdr.z_access_mask);
@@ -71,6 +83,10 @@ zfs_ace_byteswap(void *buf, size_t size, boolean_t zfs_layout)
 			    BSWAP_16(zacep->z_hdr.z_type);
 			entry_type = zacep->z_hdr.z_flags & ACE_TYPE_FLAGS;
 		} else {
+			/* Overrun avoidance */
+			if (ptr + sizeof (ace_t) > end) {
+				break;
+			}
 			acep = (ace_t *)ptr;
 			acep->a_access_mask = BSWAP_32(acep->a_access_mask);
 			acep->a_flags = BSWAP_16(acep->a_flags);
@@ -87,8 +103,14 @@ zfs_ace_byteswap(void *buf, size_t size, boolean_t zfs_layout)
 			break;
 		case ACE_IDENTIFIER_GROUP:
 		default:
+			/* Overrun avoidance */
 			if (zfs_layout) {
-				zacep->z_fuid = BSWAP_64(zacep->z_fuid);
+				if (ptr + sizeof (zfs_ace_t) <= end) {
+					zacep->z_fuid = BSWAP_64(zacep->z_fuid);
+				} else {
+					entry_size = sizeof (zfs_ace_t);
+					break;
+				}
 			}
 			switch (ace_type) {
 			case ACE_ACCESS_ALLOWED_OBJECT_ACE_TYPE:
@@ -169,7 +191,8 @@ zfs_znode_byteswap(void *buf, size_t size)
 	if (zp->zp_acl.z_acl_version == ZFS_ACL_VERSION) {
 		zfs_acl_byteswap((void *)&zp->zp_acl.z_ace_data[0],
 		    ZFS_ACE_SPACE);
-	} else
+	} else {
 		zfs_oldace_byteswap((ace_t *)&zp->zp_acl.z_ace_data[0],
 		    ACE_SLOT_CNT);
+	}
 }
diff --git a/module/zfs/zfs_dir.c b/module/zfs/zfs_dir.c
index 1ec493264..9353d0199 100644
--- a/module/zfs/zfs_dir.c
+++ b/module/zfs/zfs_dir.c
@@ -562,24 +562,6 @@ zfs_rmnode(znode_t *zp)
 	ASSERT(zp->z_phys->zp_links == 0);
 
 	/*
-	 * If this is a ZIL replay then leave the object in the unlinked set.
-	 * Otherwise we can get a deadlock, because the delete can be
-	 * quite large and span multiple tx's and txgs, but each replay
-	 * creates a tx to atomically run the replay function and mark the
-	 * replay record as complete. We deadlock trying to start a tx in
-	 * a new txg to further the deletion but can't because the replay
-	 * tx hasn't finished.
-	 *
-	 * We actually delete the object if we get a failure to create an
-	 * object in zil_replay_log_record(), or after calling zil_replay().
-	 */
-	if (zfsvfs->z_assign >= TXG_INITIAL) {
-		zfs_znode_dmu_fini(zp);
-		zfs_znode_free(zp);
-		return;
-	}
-
-	/*
 	 * If this is an attribute directory, purge its contents.
 	 */
 	if (ZTOV(zp)->v_type == VDIR && (zp->z_phys->zp_flags & ZFS_XATTR)) {
@@ -845,9 +827,9 @@ zfs_make_xattrdir(znode_t *zp, vattr_t *vap, vnode_t **xvpp, cred_t *cr)
 			    FUID_SIZE_ESTIMATE(zfsvfs));
 		}
 	}
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT)
+		if (error == ERESTART)
 			dmu_tx_wait(tx);
 		dmu_tx_abort(tx);
 		return (error);
@@ -930,7 +912,7 @@ top:
 	error = zfs_make_xattrdir(zp, &va, xvpp, cr);
 	zfs_dirent_unlock(dl);
 
-	if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+	if (error == ERESTART) {
 		/* NB: we already did dmu_tx_wait() if necessary */
 		goto top;
 	}
@@ -959,7 +941,7 @@ zfs_sticky_remove_access(znode_t *zdp, znode_t *zp, cred_t *cr)
 	uid_t		fowner;
 	zfsvfs_t	*zfsvfs = zdp->z_zfsvfs;
 
-	if (zdp->z_zfsvfs->z_assign >= TXG_INITIAL)	/* ZIL replay */
+	if (zdp->z_zfsvfs->z_replay)
 		return (0);
 
 	if ((zdp->z_phys->zp_mode & S_ISVTX) == 0)
diff --git a/module/zfs/zfs_fuid.c b/module/zfs/zfs_fuid.c
index 7cb505258..286dafba8 100644
--- a/module/zfs/zfs_fuid.c
+++ b/module/zfs/zfs_fuid.c
@@ -519,7 +519,6 @@ zfs_fuid_create(zfsvfs_t *zfsvfs, uint64_t id, cred_t *cr,
 	uint32_t rid;
 	idmap_stat status;
 	uint64_t idx;
-	boolean_t is_replay = (zfsvfs->z_assign >= TXG_INITIAL);
 	zfs_fuid_t *zfuid = NULL;
 	zfs_fuid_info_t *fuidp;
 
@@ -534,7 +533,7 @@ zfs_fuid_create(zfsvfs_t *zfsvfs, uint64_t id, cred_t *cr,
 	if (!zfsvfs->z_use_fuids || !IS_EPHEMERAL(id) || fuid_idx != 0)
 		return (id);
 
-	if (is_replay) {
+	if (zfsvfs->z_replay) {
 		fuidp = zfsvfs->z_fuid_replay;
 
 		/*
@@ -584,7 +583,7 @@ zfs_fuid_create(zfsvfs_t *zfsvfs, uint64_t id, cred_t *cr,
 
 	idx = zfs_fuid_find_by_domain(zfsvfs, domain, &kdomain, tx);
 
-	if (!is_replay)
+	if (!zfsvfs->z_replay)
 		zfs_fuid_node_add(fuidpp, kdomain, rid, idx, id, type);
 	else if (zfuid != NULL) {
 		list_remove(&fuidp->z_fuids, zfuid);
diff --git a/module/zfs/zfs_ioctl.c b/module/zfs/zfs_ioctl.c
index b6ad57451..49ee55265 100644
--- a/module/zfs/zfs_ioctl.c
+++ b/module/zfs/zfs_ioctl.c
@@ -856,9 +856,10 @@ zfs_ioc_pool_export(zfs_cmd_t *zc)
 {
 	int error;
 	boolean_t force = (boolean_t)zc->zc_cookie;
+	boolean_t hardforce = (boolean_t)zc->zc_guid;
 
 	zfs_log_history(zc);
-	error = spa_export(zc->zc_name, NULL, force);
+	error = spa_export(zc->zc_name, NULL, force, hardforce);
 	return (error);
 }
 
@@ -1162,7 +1163,7 @@ zfs_ioc_vdev_detach(zfs_cmd_t *zc)
 	if ((error = spa_open(zc->zc_name, &spa, FTAG)) != 0)
 		return (error);
 
-	error = spa_vdev_detach(spa, zc->zc_guid, B_FALSE);
+	error = spa_vdev_detach(spa, zc->zc_guid, 0, B_FALSE);
 
 	spa_close(spa, FTAG);
 	return (error);
diff --git a/module/zfs/zfs_log.c b/module/zfs/zfs_log.c
index 11cd4c264..84d64b4df 100644
--- a/module/zfs/zfs_log.c
+++ b/module/zfs/zfs_log.c
@@ -45,13 +45,33 @@
 #include <sys/spa.h>
 #include <sys/zfs_fuid.h>
 #include <sys/ddi.h>
+#include <sys/dsl_dataset.h>
+
+#define	ZFS_HANDLE_REPLAY(zilog, tx) \
+	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; \
+	}
 
 /*
- * All the functions in this file are used to construct the log entries
- * to record transactions. They allocate * an intent log transaction
- * structure (itx_t) and save within it all the information necessary to
- * possibly replay the transaction. The itx is then assigned a sequence
- * number and inserted in the in-memory list anchored in the zilog.
+ * These zfs_log_* functions must be called within a dmu tx, in one
+ * of 2 contexts depending on zilog->z_replay:
+ *
+ * Non replay mode
+ * ---------------
+ * We need to record the transaction so that if it is committed to
+ * the Intent Log then it can be replayed.  An intent log transaction
+ * structure (itx_t) is allocated and all the information necessary to
+ * possibly replay the transaction is saved in it. The itx is then assigned
+ * a sequence number and inserted in the in-memory list anchored in the zilog.
+ *
+ * Replay mode
+ * -----------
+ * We need to mark the intent log record as replayed in the log header.
+ * This is done in the same transaction as the replay so that they
+ * commit atomically.
  */
 
 int
@@ -231,6 +251,8 @@ zfs_log_create(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	if (zilog == NULL)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	/*
 	 * If we have FUIDs present then add in space for
 	 * domains and ACE fuid's if any.
@@ -334,6 +356,8 @@ zfs_log_remove(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	if (zilog == NULL)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	itx = zil_itx_create(txtype, sizeof (*lr) + namesize);
 	lr = (lr_remove_t *)&itx->itx_lr;
 	lr->lr_doid = dzp->z_id;
@@ -358,6 +382,8 @@ zfs_log_link(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	if (zilog == NULL)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	itx = zil_itx_create(txtype, sizeof (*lr) + namesize);
 	lr = (lr_link_t *)&itx->itx_lr;
 	lr->lr_doid = dzp->z_id;
@@ -385,6 +411,8 @@ zfs_log_symlink(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	if (zilog == NULL)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	itx = zil_itx_create(txtype, sizeof (*lr) + namesize + linksize);
 	lr = (lr_create_t *)&itx->itx_lr;
 	lr->lr_doid = dzp->z_id;
@@ -419,6 +447,8 @@ zfs_log_rename(zilog_t *zilog, dmu_tx_t *tx, uint64_t txtype,
 	if (zilog == NULL)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	itx = zil_itx_create(txtype, sizeof (*lr) + snamesize + dnamesize);
 	lr = (lr_rename_t *)&itx->itx_lr;
 	lr->lr_sdoid = sdzp->z_id;
@@ -451,6 +481,8 @@ zfs_log_write(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	if (zilog == NULL || zp->z_unlinked)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	/*
 	 * Writes are handled in three different ways:
 	 *
@@ -549,6 +581,8 @@ zfs_log_truncate(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	if (zilog == NULL || zp->z_unlinked)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	itx = zil_itx_create(txtype, sizeof (*lr));
 	lr = (lr_truncate_t *)&itx->itx_lr;
 	lr->lr_foid = zp->z_id;
@@ -578,6 +612,8 @@ zfs_log_setattr(zilog_t *zilog, dmu_tx_t *tx, int txtype,
 	if (zilog == NULL || zp->z_unlinked)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	/*
 	 * If XVATTR set, then log record size needs to allow
 	 * for lr_attr_t + xvattr mask, mapsize and create time
@@ -644,6 +680,8 @@ zfs_log_acl(zilog_t *zilog, dmu_tx_t *tx, znode_t *zp,
 	if (zilog == NULL || zp->z_unlinked)
 		return;
 
+	ZFS_HANDLE_REPLAY(zilog, tx); /* exits if replay */
+
 	txtype = (zp->z_zfsvfs->z_version < ZPL_VERSION_FUID) ?
 	    TX_ACL_V0 : TX_ACL;
 
diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index 06b4dee46..1bf1bc527 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -583,21 +583,50 @@ zfsvfs_setup(zfsvfs_t *zfsvfs, boolean_t mounting)
 		 * allow replays to succeed.
 		 */
 		readonly = zfsvfs->z_vfs->vfs_flag & VFS_RDONLY;
-		zfsvfs->z_vfs->vfs_flag &= ~VFS_RDONLY;
-
-		/*
-		 * Parse and replay the intent log.
-		 */
-		zil_replay(zfsvfs->z_os, zfsvfs, &zfsvfs->z_assign,
-		    zfs_replay_vector, zfs_unlinked_drain);
+		if (readonly != 0)
+			zfsvfs->z_vfs->vfs_flag &= ~VFS_RDONLY;
+		else
+			zfs_unlinked_drain(zfsvfs);
 
-		zfs_unlinked_drain(zfsvfs);
+		zfsvfs->z_log = zil_open(zfsvfs->z_os, zfs_get_data);
+		if (zil_disable) {
+			zil_destroy(zfsvfs->z_log, 0);
+			zfsvfs->z_log = NULL;
+		} else {
+			/*
+			 * Parse and replay the intent log.
+			 *
+			 * Because of ziltest, this must be done after
+			 * zfs_unlinked_drain().  (Further note: ziltest
+			 * doesn't use readonly mounts, where
+			 * zfs_unlinked_drain() isn't called.)  This is because
+			 * ziltest causes spa_sync() to think it's committed,
+			 * but actually it is not, so the intent log contains
+			 * many txg's worth of changes.
+			 *
+			 * In particular, if object N is in the unlinked set in
+			 * the last txg to actually sync, then it could be
+			 * actually freed in a later txg and then reallocated
+			 * in a yet later txg.  This would write a "create
+			 * object N" record to the intent log.  Normally, this
+			 * would be fine because the spa_sync() would have
+			 * written out the fact that object N is free, before
+			 * we could write the "create object N" intent log
+			 * record.
+			 *
+			 * But when we are in ziltest mode, we advance the "open
+			 * txg" without actually spa_sync()-ing the changes to
+			 * disk.  So we would see that object N is still
+			 * allocated and in the unlinked set, and there is an
+			 * intent log record saying to allocate it.
+			 */
+			zfsvfs->z_replay = B_TRUE;
+			zil_replay(zfsvfs->z_os, zfsvfs, zfs_replay_vector);
+			zfsvfs->z_replay = B_FALSE;
+		}
 		zfsvfs->z_vfs->vfs_flag |= readonly; /* restore readonly bit */
 	}
 
-	if (!zil_disable)
-		zfsvfs->z_log = zil_open(zfsvfs->z_os, zfs_get_data);
-
 	return (0);
 }
 
@@ -634,7 +663,6 @@ zfs_domount(vfs_t *vfsp, char *osname)
 	zfsvfs = kmem_zalloc(sizeof (zfsvfs_t), KM_SLEEP);
 	zfsvfs->z_vfs = vfsp;
 	zfsvfs->z_parent = zfsvfs;
-	zfsvfs->z_assign = TXG_NOWAIT;
 	zfsvfs->z_max_blksz = SPA_MAXBLOCKSIZE;
 	zfsvfs->z_show_ctldir = ZFS_SNAPDIR_VISIBLE;
 
diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 8e0037e37..f62d3bfa0 100644
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -105,9 +105,7 @@
  *  (3)	All range locks must be grabbed before calling dmu_tx_assign(),
  *	as they can span dmu_tx_assign() calls.
  *
- *  (4)	Always pass zfsvfs->z_assign as the second argument to dmu_tx_assign().
- *	In normal operation, this will be TXG_NOWAIT.  During ZIL replay,
- *	it will be a specific txg.  Either way, dmu_tx_assign() never blocks.
+ *  (4)	Always pass TXG_NOWAIT as the second argument to dmu_tx_assign().
  *	This is critical because we don't want to block while holding locks.
  *	Note, in particular, that if a lock is sometimes acquired before
  *	the tx assigns, and sometimes after (e.g. z_lock), then failing to
@@ -124,6 +122,8 @@
  *  (5)	If the operation succeeded, generate the intent log entry for it
  *	before dropping locks.  This ensures that the ordering of events
  *	in the intent log matches the order in which they actually occurred.
+ *      During ZIL replay the zfs_log_* functions will update the sequence
+ *	number to indicate the zil transaction has replayed.
  *
  *  (6)	At the end of each vnode op, the DMU tx must always commit,
  *	regardless of whether there were any errors.
@@ -139,12 +139,12 @@
  *	rw_enter(...);			// grab any other locks you need
  *	tx = dmu_tx_create(...);	// get DMU tx
  *	dmu_tx_hold_*();		// hold each object you might modify
- *	error = dmu_tx_assign(tx, zfsvfs->z_assign);	// try to assign
+ *	error = dmu_tx_assign(tx, TXG_NOWAIT);	// try to assign
  *	if (error) {
  *		rw_exit(...);		// drop locks
  *		zfs_dirent_unlock(dl);	// unlock directory entry
  *		VN_RELE(...);		// release held vnodes
- *		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+ *		if (error == ERESTART) {
  *			dmu_tx_wait(tx);
  *			dmu_tx_abort(tx);
  *			goto top;
@@ -698,10 +698,9 @@ zfs_write(vnode_t *vp, uio_t *uio, int ioflag, cred_t *cr, caller_context_t *ct)
 		tx = dmu_tx_create(zfsvfs->z_os);
 		dmu_tx_hold_bonus(tx, zp->z_id);
 		dmu_tx_hold_write(tx, zp->z_id, woff, MIN(n, max_blksz));
-		error = dmu_tx_assign(tx, zfsvfs->z_assign);
+		error = dmu_tx_assign(tx, TXG_NOWAIT);
 		if (error) {
-			if (error == ERESTART &&
-			    zfsvfs->z_assign == TXG_NOWAIT) {
+			if (error == ERESTART) {
 				dmu_tx_wait(tx);
 				dmu_tx_abort(tx);
 				continue;
@@ -807,7 +806,7 @@ zfs_write(vnode_t *vp, uio_t *uio, int ioflag, cred_t *cr, caller_context_t *ct)
 	 * If we're in replay mode, or we made no progress, return error.
 	 * Otherwise, it's at least a partial write, so it's successful.
 	 */
-	if (zfsvfs->z_assign >= TXG_INITIAL || uio->uio_resid == start_resid) {
+	if (zfsvfs->z_replay || uio->uio_resid == start_resid) {
 		ZFS_EXIT(zfsvfs);
 		return (error);
 	}
@@ -1233,11 +1232,10 @@ top:
 			dmu_tx_hold_write(tx, DMU_NEW_OBJECT,
 			    0, SPA_MAXBLOCKSIZE);
 		}
-		error = dmu_tx_assign(tx, zfsvfs->z_assign);
+		error = dmu_tx_assign(tx, TXG_NOWAIT);
 		if (error) {
 			zfs_dirent_unlock(dl);
-			if (error == ERESTART &&
-			    zfsvfs->z_assign == TXG_NOWAIT) {
+			if (error == ERESTART) {
 				dmu_tx_wait(tx);
 				dmu_tx_abort(tx);
 				goto top;
@@ -1449,11 +1447,11 @@ top:
 	/* charge as an update -- would be nice not to charge at all */
 	dmu_tx_hold_zap(tx, zfsvfs->z_unlinkedobj, FALSE, NULL);
 
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		zfs_dirent_unlock(dl);
 		VN_RELE(vp);
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -1659,10 +1657,10 @@ top:
 	if ((dzp->z_phys->zp_flags & ZFS_INHERIT_ACE) || aclp)
 		dmu_tx_hold_write(tx, DMU_NEW_OBJECT,
 		    0, SPA_MAXBLOCKSIZE);
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		zfs_dirent_unlock(dl);
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -1789,13 +1787,13 @@ top:
 	dmu_tx_hold_zap(tx, dzp->z_id, FALSE, name);
 	dmu_tx_hold_bonus(tx, zp->z_id);
 	dmu_tx_hold_zap(tx, zfsvfs->z_unlinkedobj, FALSE, NULL);
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		rw_exit(&zp->z_parent_lock);
 		rw_exit(&zp->z_name_lock);
 		zfs_dirent_unlock(dl);
 		VN_RELE(vp);
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -2342,6 +2340,7 @@ zfs_setattr(vnode_t *vp, vattr_t *vap, int flags, cred_t *cr,
 	zilog_t		*zilog;
 	dmu_tx_t	*tx;
 	vattr_t		oldva;
+	xvattr_t	tmpxvattr;
 	uint_t		mask = vap->va_mask;
 	uint_t		saved_mask;
 	int		trim_mask = 0;
@@ -2396,6 +2395,8 @@ zfs_setattr(vnode_t *vp, vattr_t *vap, int flags, cred_t *cr,
 	 */
 	xoap = xva_getxoptattr(xvap);
 
+	xva_init(&tmpxvattr);
+
 	/*
 	 * Immutable files can only alter immutable bit and atime
 	 */
@@ -2518,28 +2519,78 @@ top:
 	oldva.va_mode = pzp->zp_mode;
 	zfs_fuid_map_ids(zp, cr, &oldva.va_uid, &oldva.va_gid);
 	if (mask & AT_XVATTR) {
-		if ((need_policy == FALSE) &&
-		    (XVA_ISSET_REQ(xvap, XAT_APPENDONLY) &&
-		    xoap->xoa_appendonly !=
-		    ((pzp->zp_flags & ZFS_APPENDONLY) != 0)) ||
-		    (XVA_ISSET_REQ(xvap, XAT_NOUNLINK) &&
-		    xoap->xoa_nounlink !=
-		    ((pzp->zp_flags & ZFS_NOUNLINK) != 0)) ||
-		    (XVA_ISSET_REQ(xvap, XAT_IMMUTABLE) &&
-		    xoap->xoa_immutable !=
-		    ((pzp->zp_flags & ZFS_IMMUTABLE) != 0)) ||
-		    (XVA_ISSET_REQ(xvap, XAT_NODUMP) &&
-		    xoap->xoa_nodump !=
-		    ((pzp->zp_flags & ZFS_NODUMP) != 0)) ||
-		    (XVA_ISSET_REQ(xvap, XAT_AV_MODIFIED) &&
-		    xoap->xoa_av_modified !=
-		    ((pzp->zp_flags & ZFS_AV_MODIFIED) != 0)) ||
-		    ((XVA_ISSET_REQ(xvap, XAT_AV_QUARANTINED) &&
-		    ((vp->v_type != VREG && xoap->xoa_av_quarantined) ||
-		    xoap->xoa_av_quarantined !=
-		    ((pzp->zp_flags & ZFS_AV_QUARANTINED) != 0)))) ||
-		    (XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP)) ||
-		    (XVA_ISSET_REQ(xvap, XAT_OPAQUE))) {
+		/*
+		 * Update xvattr mask to include only those attributes
+		 * that are actually changing.
+		 *
+		 * the bits will be restored prior to actually setting
+		 * the attributes so the caller thinks they were set.
+		 */
+		if (XVA_ISSET_REQ(xvap, XAT_APPENDONLY)) {
+			if (xoap->xoa_appendonly !=
+			    ((pzp->zp_flags & ZFS_APPENDONLY) != 0)) {
+				need_policy = TRUE;
+			} else {
+				XVA_CLR_REQ(xvap, XAT_APPENDONLY);
+				XVA_SET_REQ(&tmpxvattr, XAT_APPENDONLY);
+			}
+		}
+
+		if (XVA_ISSET_REQ(xvap, XAT_NOUNLINK)) {
+			if (xoap->xoa_nounlink !=
+			    ((pzp->zp_flags & ZFS_NOUNLINK) != 0)) {
+				need_policy = TRUE;
+			} else {
+				XVA_CLR_REQ(xvap, XAT_NOUNLINK);
+				XVA_SET_REQ(&tmpxvattr, XAT_NOUNLINK);
+			}
+		}
+
+		if (XVA_ISSET_REQ(xvap, XAT_IMMUTABLE)) {
+			if (xoap->xoa_immutable !=
+			    ((pzp->zp_flags & ZFS_IMMUTABLE) != 0)) {
+				need_policy = TRUE;
+			} else {
+				XVA_CLR_REQ(xvap, XAT_IMMUTABLE);
+				XVA_SET_REQ(&tmpxvattr, XAT_IMMUTABLE);
+			}
+		}
+
+		if (XVA_ISSET_REQ(xvap, XAT_NODUMP)) {
+			if (xoap->xoa_nodump !=
+			    ((pzp->zp_flags & ZFS_NODUMP) != 0)) {
+				need_policy = TRUE;
+			} else {
+				XVA_CLR_REQ(xvap, XAT_NODUMP);
+				XVA_SET_REQ(&tmpxvattr, XAT_NODUMP);
+			}
+		}
+
+		if (XVA_ISSET_REQ(xvap, XAT_AV_MODIFIED)) {
+			if (xoap->xoa_av_modified !=
+			    ((pzp->zp_flags & ZFS_AV_MODIFIED) != 0)) {
+				need_policy = TRUE;
+			} else {
+				XVA_CLR_REQ(xvap, XAT_AV_MODIFIED);
+				XVA_SET_REQ(&tmpxvattr, XAT_AV_MODIFIED);
+			}
+		}
+
+		if (XVA_ISSET_REQ(xvap, XAT_AV_QUARANTINED)) {
+			if ((vp->v_type != VREG &&
+			    xoap->xoa_av_quarantined) ||
+			    xoap->xoa_av_quarantined !=
+			    ((pzp->zp_flags & ZFS_AV_QUARANTINED) != 0)) {
+				need_policy = TRUE;
+			} else {
+				XVA_CLR_REQ(xvap, XAT_AV_QUARANTINED);
+				XVA_SET_REQ(&tmpxvattr, XAT_AV_QUARANTINED);
+			}
+		}
+
+		if (need_policy == FALSE &&
+		    (XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP) ||
+		    XVA_ISSET_REQ(xvap, XAT_OPAQUE))) {
 			need_policy = TRUE;
 		}
 	}
@@ -2649,7 +2700,7 @@ top:
 		dmu_tx_hold_bonus(tx, attrzp->z_id);
 	}
 
-	err = dmu_tx_assign(tx, zfsvfs->z_assign);
+	err = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (err) {
 		if (attrzp)
 			VN_RELE(ZTOV(attrzp));
@@ -2659,7 +2710,7 @@ top:
 			aclp = NULL;
 		}
 
-		if (err == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (err == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -2732,6 +2783,31 @@ top:
 	 */
 
 	if (xoap && (mask & AT_XVATTR)) {
+
+		/*
+		 * restore trimmed off masks
+		 * so that return masks can be set for caller.
+		 */
+
+		if (XVA_ISSET_REQ(&tmpxvattr, XAT_APPENDONLY)) {
+			XVA_SET_REQ(xvap, XAT_APPENDONLY);
+		}
+		if (XVA_ISSET_REQ(&tmpxvattr, XAT_NOUNLINK)) {
+			XVA_SET_REQ(xvap, XAT_NOUNLINK);
+		}
+		if (XVA_ISSET_REQ(&tmpxvattr, XAT_IMMUTABLE)) {
+			XVA_SET_REQ(xvap, XAT_IMMUTABLE);
+		}
+		if (XVA_ISSET_REQ(&tmpxvattr, XAT_NODUMP)) {
+			XVA_SET_REQ(xvap, XAT_NODUMP);
+		}
+		if (XVA_ISSET_REQ(&tmpxvattr, XAT_AV_MODIFIED)) {
+			XVA_SET_REQ(xvap, XAT_AV_MODIFIED);
+		}
+		if (XVA_ISSET_REQ(&tmpxvattr, XAT_AV_QUARANTINED)) {
+			XVA_SET_REQ(xvap, XAT_AV_QUARANTINED);
+		}
+
 		if (XVA_ISSET_REQ(xvap, XAT_AV_SCANSTAMP)) {
 			size_t len;
 			dmu_object_info_t doi;
@@ -3104,7 +3180,7 @@ top:
 	if (tzp)
 		dmu_tx_hold_bonus(tx, tzp->z_id);	/* parent changes */
 	dmu_tx_hold_zap(tx, zfsvfs->z_unlinkedobj, FALSE, NULL);
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		if (zl != NULL)
 			zfs_rename_unlock(&zl);
@@ -3113,7 +3189,7 @@ top:
 		VN_RELE(ZTOV(szp));
 		if (tzp)
 			VN_RELE(ZTOV(tzp));
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -3242,10 +3318,10 @@ top:
 			    FUID_SIZE_ESTIMATE(zfsvfs));
 		}
 	}
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		zfs_dirent_unlock(dl);
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -3462,10 +3538,10 @@ top:
 	tx = dmu_tx_create(zfsvfs->z_os);
 	dmu_tx_hold_bonus(tx, szp->z_id);
 	dmu_tx_hold_zap(tx, dzp->z_id, TRUE, name);
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
 		zfs_dirent_unlock(dl);
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -3547,7 +3623,7 @@ zfs_putapage(vnode_t *vp, page_t *pp, u_offset_t *offp,
 	len = PAGESIZE;
 	/*
 	 * If our blocksize is bigger than the page size, try to kluster
-	 * muiltiple pages so that we write a full block (thus avoiding
+	 * multiple pages so that we write a full block (thus avoiding
 	 * a read-modify-write).
 	 */
 	if (off < filesz && zp->z_blksz > PAGESIZE) {
@@ -3589,9 +3665,9 @@ top:
 	tx = dmu_tx_create(zfsvfs->z_os);
 	dmu_tx_hold_write(tx, zp->z_id, off, len);
 	dmu_tx_hold_bonus(tx, zp->z_id);
-	err = dmu_tx_assign(tx, zfsvfs->z_assign);
+	err = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (err != 0) {
-		if (err == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (err == ERESTART) {
 			zfs_range_unlock(rl);
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
diff --git a/module/zfs/zfs_znode.c b/module/zfs/zfs_znode.c
index 25751ae5f..9a7860380 100644
--- a/module/zfs/zfs_znode.c
+++ b/module/zfs/zfs_znode.c
@@ -734,7 +734,7 @@ zfs_mknode(znode_t *dzp, vattr_t *vap, dmu_tx_t *tx, cred_t *cr,
 
 	ASSERT(vap && (vap->va_mask & (AT_TYPE|AT_MODE)) == (AT_TYPE|AT_MODE));
 
-	if (zfsvfs->z_assign >= TXG_INITIAL) {		/* ZIL replay */
+	if (zfsvfs->z_replay) {
 		obj = vap->va_nodeid;
 		flag |= IS_REPLAY;
 		now = vap->va_ctime;		/* see zfs_replay_create() */
@@ -1254,9 +1254,9 @@ top:
 		newblksz = 0;
 	}
 
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -1358,9 +1358,9 @@ zfs_trunc(znode_t *zp, uint64_t end)
 top:
 	tx = dmu_tx_create(zfsvfs->z_os);
 	dmu_tx_hold_bonus(tx, zp->z_id);
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto top;
@@ -1456,9 +1456,9 @@ zfs_freesp(znode_t *zp, uint64_t off, uint64_t len, int flag, boolean_t log)
 log:
 	tx = dmu_tx_create(zfsvfs->z_os);
 	dmu_tx_hold_bonus(tx, zp->z_id);
-	error = dmu_tx_assign(tx, zfsvfs->z_assign);
+	error = dmu_tx_assign(tx, TXG_NOWAIT);
 	if (error) {
-		if (error == ERESTART && zfsvfs->z_assign == TXG_NOWAIT) {
+		if (error == ERESTART) {
 			dmu_tx_wait(tx);
 			dmu_tx_abort(tx);
 			goto log;
@@ -1562,7 +1562,6 @@ zfs_create_fs(objset_t *os, cred_t *cr, nvlist_t *zplprops, dmu_tx_t *tx)
 	bzero(&zfsvfs, sizeof (zfsvfs_t));
 
 	zfsvfs.z_os = os;
-	zfsvfs.z_assign = TXG_NOWAIT;
 	zfsvfs.z_parent = &zfsvfs;
 	zfsvfs.z_version = version;
 	zfsvfs.z_use_fuids = USE_FUIDS(version, os);
diff --git a/module/zfs/zil.c b/module/zfs/zil.c
index 95101882b..83fef0d87 100644
--- a/module/zfs/zil.c
+++ b/module/zfs/zil.c
@@ -351,14 +351,20 @@ zil_create(zilog_t *zilog)
 	blk = zh->zh_log;
 
 	/*
-	 * If we don't already have an initial log block, allocate one now.
+	 * If we don't already have an initial log block or we have one
+	 * but it's the wrong endianness then allocate one.
 	 */
-	if (BP_IS_HOLE(&blk)) {
+	if (BP_IS_HOLE(&blk) || BP_SHOULD_BYTESWAP(&blk)) {
 		tx = dmu_tx_create(zilog->zl_os);
 		(void) dmu_tx_assign(tx, TXG_WAIT);
 		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);
+			BP_ZERO(&blk);
+		}
+
 		error = zio_alloc_blk(zilog->zl_spa, ZIL_MIN_BLKSZ, &blk,
 		    NULL, txg);
 
@@ -1214,7 +1220,7 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx)
 
 	ASSERT(zilog->zl_stop_sync == 0);
 
-	zh->zh_replay_seq = zilog->zl_replay_seq[txg & TXG_MASK];
+	zh->zh_replay_seq = zilog->zl_replayed_seq[txg & TXG_MASK];
 
 	if (zilog->zl_destroy_txg == txg) {
 		blkptr_t blk = zh->zh_log;
@@ -1223,7 +1229,7 @@ zil_sync(zilog_t *zilog, dmu_tx_t *tx)
 		ASSERT(spa_sync_pass(spa) == 1);
 
 		bzero(zh, sizeof (zil_header_t));
-		bzero(zilog->zl_replay_seq, sizeof (zilog->zl_replay_seq));
+		bzero(zilog->zl_replayed_seq, sizeof (zilog->zl_replayed_seq));
 
 		if (zilog->zl_keep_first) {
 			/*
@@ -1460,9 +1466,7 @@ zil_resume(zilog_t *zilog)
 typedef struct zil_replay_arg {
 	objset_t	*zr_os;
 	zil_replay_func_t **zr_replay;
-	zil_replay_cleaner_t *zr_replay_cleaner;
 	void		*zr_arg;
-	uint64_t	*zr_txgp;
 	boolean_t	zr_byteswap;
 	char		*zr_lrbuf;
 } zil_replay_arg_t;
@@ -1475,9 +1479,9 @@ zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
 	uint64_t reclen = lr->lrc_reclen;
 	uint64_t txtype = lr->lrc_txtype;
 	char *name;
-	int pass, error, sunk;
+	int pass, error;
 
-	if (zilog->zl_stop_replay)
+	if (!zilog->zl_replay)			/* giving up */
 		return;
 
 	if (lr->lrc_txg < claim_txg)		/* already committed */
@@ -1489,6 +1493,11 @@ zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
 	/* Strip case-insensitive bit, still present in log record */
 	txtype &= ~TX_CI;
 
+	if (txtype == 0 || txtype >= TX_MAX_TYPE) {
+		error = EINVAL;
+		goto bad;
+	}
+
 	/*
 	 * Make a copy of the data so we can revise and extend it.
 	 */
@@ -1539,69 +1548,16 @@ zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
 	}
 
 	/*
-	 * Replay of large truncates can end up needing additional txs
-	 * and a different txg. If they are nested within the replay tx
-	 * as below then a hang is possible. So we do the truncate here
-	 * and redo the truncate later (a no-op) and update the sequence
-	 * number whilst in the replay tx. Fortunately, it's safe to repeat
-	 * a truncate if we crash and the truncate commits. A create over
-	 * an existing file will also come in as a TX_TRUNCATE record.
-	 *
-	 * Note, remove of large files and renames over large files is
-	 * handled by putting the deleted object on a stable list
-	 * and if necessary force deleting the object outside of the replay
-	 * transaction using the zr_replay_cleaner.
-	 */
-	if (txtype == TX_TRUNCATE) {
-		*zr->zr_txgp = TXG_NOWAIT;
-		error = zr->zr_replay[TX_TRUNCATE](zr->zr_arg, zr->zr_lrbuf,
-		    zr->zr_byteswap);
-		if (error)
-			goto bad;
-		zr->zr_byteswap = 0; /* only byteswap once */
-	}
-
-	/*
 	 * We must now do two things atomically: replay this log record,
-	 * and update the log header to reflect the fact that we did so.
-	 * We use the DMU's ability to assign into a specific txg to do this.
+	 * and update the log header sequence number to reflect the fact that
+	 * we did so. At the end of each replay function the sequence number
+	 * is updated if we are in replay mode.
 	 */
-	for (pass = 1, sunk = B_FALSE; /* CONSTANTCONDITION */; pass++) {
-		uint64_t replay_txg;
-		dmu_tx_t *replay_tx;
-
-		replay_tx = dmu_tx_create(zr->zr_os);
-		error = dmu_tx_assign(replay_tx, TXG_WAIT);
-		if (error) {
-			dmu_tx_abort(replay_tx);
-			break;
-		}
-
-		replay_txg = dmu_tx_get_txg(replay_tx);
-
-		if (txtype == 0 || txtype >= TX_MAX_TYPE) {
-			error = EINVAL;
-		} else {
-			/*
-			 * On the first pass, arrange for the replay vector
-			 * to fail its dmu_tx_assign().  That's the only way
-			 * to ensure that those code paths remain well tested.
-			 *
-			 * Only byteswap (if needed) on the 1st pass.
-			 */
-			*zr->zr_txgp = replay_txg - (pass == 1);
-			error = zr->zr_replay[txtype](zr->zr_arg, zr->zr_lrbuf,
-			    zr->zr_byteswap && pass == 1);
-			*zr->zr_txgp = TXG_NOWAIT;
-		}
-
-		if (error == 0) {
-			dsl_dataset_dirty(dmu_objset_ds(zr->zr_os), replay_tx);
-			zilog->zl_replay_seq[replay_txg & TXG_MASK] =
-			    lr->lrc_seq;
-		}
-
-		dmu_tx_commit(replay_tx);
+	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;
@@ -1609,37 +1565,22 @@ zil_replay_log_record(zilog_t *zilog, lr_t *lr, void *zra, uint64_t claim_txg)
 		/*
 		 * 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 other than ERESTART
-		 * we try syncing out any removes then retrying the
-		 * transaction.
+		 * EEXIST. So if we receive any error we try syncing out
+		 * any removes then retry the transaction.
 		 */
-		if (error != ERESTART && !sunk) {
-			if (zr->zr_replay_cleaner)
-				zr->zr_replay_cleaner(zr->zr_arg);
+		if (pass == 1)
 			txg_wait_synced(spa_get_dsl(zilog->zl_spa), 0);
-			sunk = B_TRUE;
-			continue; /* retry */
-		}
-
-		if (error != ERESTART)
-			break;
-
-		if (pass != 1)
-			txg_wait_open(spa_get_dsl(zilog->zl_spa),
-			    replay_txg + 1);
-
-		dprintf("pass %d, retrying\n", pass);
 	}
 
 bad:
-	ASSERT(error && error != ERESTART);
+	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_stop_replay = 1;
+	zilog->zl_replay = B_FALSE;
 	kmem_free(name, MAXNAMELEN);
 }
 
@@ -1654,9 +1595,7 @@ zil_incr_blks(zilog_t *zilog, blkptr_t *bp, void *arg, uint64_t claim_txg)
  * If this dataset has a non-empty intent log, replay it and destroy it.
  */
 void
-zil_replay(objset_t *os, void *arg, uint64_t *txgp,
-	zil_replay_func_t *replay_func[TX_MAX_TYPE],
-	zil_replay_cleaner_t *replay_cleaner)
+zil_replay(objset_t *os, void *arg, zil_replay_func_t *replay_func[TX_MAX_TYPE])
 {
 	zilog_t *zilog = dmu_objset_zil(os);
 	const zil_header_t *zh = zilog->zl_header;
@@ -1669,9 +1608,7 @@ zil_replay(objset_t *os, void *arg, uint64_t *txgp,
 
 	zr.zr_os = os;
 	zr.zr_replay = replay_func;
-	zr.zr_replay_cleaner = replay_cleaner;
 	zr.zr_arg = arg;
-	zr.zr_txgp = txgp;
 	zr.zr_byteswap = BP_SHOULD_BYTESWAP(&zh->zh_log);
 	zr.zr_lrbuf = kmem_alloc(2 * SPA_MAXBLOCKSIZE, KM_SLEEP);
 
@@ -1680,7 +1617,7 @@ zil_replay(objset_t *os, void *arg, uint64_t *txgp,
 	 */
 	txg_wait_synced(zilog->zl_dmu_pool, 0);
 
-	zilog->zl_stop_replay = 0;
+	zilog->zl_replay = B_TRUE;
 	zilog->zl_replay_time = lbolt;
 	ASSERT(zilog->zl_replay_blks == 0);
 	(void) zil_parse(zilog, zil_incr_blks, zil_replay_log_record, &zr,
@@ -1689,6 +1626,7 @@ zil_replay(objset_t *os, void *arg, uint64_t *txgp,
 
 	zil_destroy(zilog, B_FALSE);
 	txg_wait_synced(zilog->zl_dmu_pool, zilog->zl_destroy_txg);
+	zilog->zl_replay = B_FALSE;
 }
 
 /*
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index d347920ea..62af799f5 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -767,7 +767,8 @@ zio_read_bp_init(zio_t *zio)
 {
 	blkptr_t *bp = zio->io_bp;
 
-	if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF && zio->io_logical == zio) {
+	if (BP_GET_COMPRESS(bp) != ZIO_COMPRESS_OFF &&
+	    zio->io_logical == zio && !(zio->io_flags & ZIO_FLAG_RAW)) {
 		uint64_t csize = BP_GET_PSIZE(bp);
 		void *cbuf = zio_buf_alloc(csize);
 
@@ -1790,7 +1791,30 @@ zio_vdev_io_start(zio_t *zio)
 
 	ASSERT(P2PHASE(zio->io_offset, align) == 0);
 	ASSERT(P2PHASE(zio->io_size, align) == 0);
-	ASSERT(zio->io_type != ZIO_TYPE_WRITE || (spa_mode & FWRITE));
+	ASSERT(zio->io_type != ZIO_TYPE_WRITE || spa_writeable(spa));
+
+	/*
+	 * If this is a repair I/O, and there's no self-healing involved --
+	 * that is, we're just resilvering what we expect to resilver --
+	 * then don't do the I/O unless zio's txg is actually in vd's DTL.
+	 * This prevents spurious resilvering with nested replication.
+	 * For example, given a mirror of mirrors, (A+B)+(C+D), if only
+	 * A is out of date, we'll read from C+D, then use the data to
+	 * resilver A+B -- but we don't actually want to resilver B, just A.
+	 * The top-level mirror has no way to know this, so instead we just
+	 * discard unnecessary repairs as we work our way down the vdev tree.
+	 * The same logic applies to any form of nested replication:
+	 * ditto + mirror, RAID-Z + replacing, etc.  This covers them all.
+	 */
+	if ((zio->io_flags & ZIO_FLAG_IO_REPAIR) &&
+	    !(zio->io_flags & ZIO_FLAG_SELF_HEAL) &&
+	    zio->io_txg != 0 &&	/* not a delegated i/o */
+	    !vdev_dtl_contains(vd, DTL_PARTIAL, zio->io_txg, 1)) {
+		ASSERT(zio->io_type == ZIO_TYPE_WRITE);
+		ASSERT(zio->io_delegate_list == NULL);
+		zio_vdev_io_bypass(zio);
+		return (ZIO_PIPELINE_CONTINUE);
+	}
 
 	if (vd->vdev_ops->vdev_op_leaf &&
 	    (zio->io_type == ZIO_TYPE_READ || zio->io_type == ZIO_TYPE_WRITE)) {
@@ -1806,7 +1830,6 @@ zio_vdev_io_start(zio_t *zio)
 			zio_interrupt(zio);
 			return (ZIO_PIPELINE_STOP);
 		}
-
 	}
 
 	return (vd->vdev_ops->vdev_op_io_start(zio));
@@ -2157,6 +2180,7 @@ zio_done(zio_t *zio)
 		if ((zio->io_type == ZIO_TYPE_READ ||
 		    zio->io_type == ZIO_TYPE_FREE) &&
 		    zio->io_error == ENXIO &&
+		    spa->spa_load_state == SPA_LOAD_NONE &&
 		    spa_get_failmode(spa) != ZIO_FAILURE_MODE_CONTINUE)
 			zio->io_reexecute |= ZIO_REEXECUTE_SUSPEND;
 
diff --git a/module/zfs/zvol.c b/module/zfs/zvol.c
index 4e993060c..0206dad9e 100644
--- a/module/zfs/zvol.c
+++ b/module/zfs/zvol.c
@@ -75,6 +75,7 @@
 #include <sys/vdev_impl.h>
 #include <sys/zvol.h>
 #include <sys/dumphdr.h>
+#include <sys/zil_impl.h>
 
 #include "zfs_namecheck.h"
 
@@ -113,7 +114,6 @@ typedef struct zvol_state {
 	uint32_t	zv_total_opens;	/* total open count */
 	zilog_t		*zv_zilog;	/* ZIL handle */
 	list_t		zv_extents;	/* List of extents for dump */
-	uint64_t	zv_txg_assign;	/* txg to assign during ZIL replay */
 	znode_t		zv_znode;	/* for range locking */
 } zvol_state_t;
 
@@ -381,7 +381,7 @@ zvol_replay_write(zvol_state_t *zv, lr_write_t *lr, boolean_t byteswap)
 
 	tx = dmu_tx_create(os);
 	dmu_tx_hold_write(tx, ZVOL_OBJ, off, len);
-	error = dmu_tx_assign(tx, zv->zv_txg_assign);
+	error = dmu_tx_assign(tx, TXG_WAIT);
 	if (error) {
 		dmu_tx_abort(tx);
 	} else {
@@ -558,7 +558,7 @@ zvol_create_minor(const char *name, major_t maj)
 	ASSERT(error == 0);
 	zv->zv_volblocksize = doi.doi_data_block_size;
 
-	zil_replay(os, zv, &zv->zv_txg_assign, zvol_replay_vector, NULL);
+	zil_replay(os, zv, zvol_replay_vector);
 	zvol_size_changed(zv, maj);
 
 	/* XXX this should handle the possible i/o error */
@@ -971,8 +971,16 @@ static void
 zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, offset_t off, ssize_t len)
 {
 	uint32_t blocksize = zv->zv_volblocksize;
+	zilog_t *zilog = zv->zv_zilog;
 	lr_write_t *lr;
 
+	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;
+	}
+
 	while (len) {
 		ssize_t nbytes = MIN(len, blocksize - P2PHASE(off, blocksize));
 		itx_t *itx = zil_itx_create(TX_WRITE, sizeof (*lr));
@@ -987,7 +995,7 @@ zvol_log_write(zvol_state_t *zv, dmu_tx_t *tx, offset_t off, ssize_t len)
 		lr->lr_blkoff = off - P2ALIGN_TYPED(off, blocksize, uint64_t);
 		BP_ZERO(&lr->lr_blkptr);
 
-		(void) zil_itx_assign(zv->zv_zilog, itx, tx);
+		(void) zil_itx_assign(zilog, itx, tx);
 		len -= nbytes;
 		off += nbytes;
 	}