1 files changed, 259 insertions, 109 deletions

diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index e7408daf2..ec5217145 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