Merge commit 'refs/top-bases/gcc-cast' into gcc-cast

1 files changed, 2425 insertions, 0 deletions

diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
new file mode 100644
index 000000000..16a27e514
--- /dev/null
+++ b/module/zfs/vdev.c
@@ -0,0 +1,2425 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
+ * Use is subject to license terms.
+ */
+
+#include <sys/zfs_context.h>
+#include <sys/fm/fs/zfs.h>
+#include <sys/spa.h>
+#include <sys/spa_impl.h>
+#include <sys/dmu.h>
+#include <sys/dmu_tx.h>
+#include <sys/vdev_impl.h>
+#include <sys/uberblock_impl.h>
+#include <sys/metaslab.h>
+#include <sys/metaslab_impl.h>
+#include <sys/space_map.h>
+#include <sys/zio.h>
+#include <sys/zap.h>
+#include <sys/fs/zfs.h>
+#include <sys/arc.h>
+
+/*
+ * Virtual device management.
+ */
+
+static vdev_ops_t *vdev_ops_table[] = {
+	&vdev_root_ops,
+	&vdev_raidz_ops,
+	&vdev_mirror_ops,
+	&vdev_replacing_ops,
+	&vdev_spare_ops,
+	&vdev_disk_ops,
+	&vdev_file_ops,
+	&vdev_missing_ops,
+	NULL
+};
+
+/* maximum scrub/resilver I/O queue per leaf vdev */
+int zfs_scrub_limit = 10;
+
+/*
+ * Given a vdev type, return the appropriate ops vector.
+ */
+static vdev_ops_t *
+vdev_getops(const char *type)
+{
+	vdev_ops_t *ops, **opspp;
+
+	for (opspp = vdev_ops_table; (ops = *opspp) != NULL; opspp++)
+		if (strcmp(ops->vdev_op_type, type) == 0)
+			break;
+
+	return (ops);
+}
+
+/*
+ * Default asize function: return the MAX of psize with the asize of
+ * all children.  This is what's used by anything other than RAID-Z.
+ */
+uint64_t
+vdev_default_asize(vdev_t *vd, uint64_t psize)
+{
+	uint64_t asize = P2ROUNDUP(psize, 1ULL << vd->vdev_top->vdev_ashift);
+	uint64_t csize;
+	uint64_t c;
+
+	for (c = 0; c < vd->vdev_children; c++) {
+		csize = vdev_psize_to_asize(vd->vdev_child[c], psize);
+		asize = MAX(asize, csize);
+	}
+
+	return (asize);
+}
+
+/*
+ * Get the replaceable or attachable device size.
+ * If the parent is a mirror or raidz, the replaceable size is the minimum
+ * psize of all its children. For the rest, just return our own psize.
+ *
+ * e.g.
+ *			psize	rsize
+ * root			-	-
+ *	mirror/raidz	-	-
+ *	    disk1	20g	20g
+ *	    disk2 	40g	20g
+ *	disk3 		80g	80g
+ */
+uint64_t
+vdev_get_rsize(vdev_t *vd)
+{
+	vdev_t *pvd, *cvd;
+	uint64_t c, rsize;
+
+	pvd = vd->vdev_parent;
+
+	/*
+	 * If our parent is NULL or the root, just return our own psize.
+	 */
+	if (pvd == NULL || pvd->vdev_parent == NULL)
+		return (vd->vdev_psize);
+
+	rsize = 0;
+
+	for (c = 0; c < pvd->vdev_children; c++) {
+		cvd = pvd->vdev_child[c];
+		rsize = MIN(rsize - 1, cvd->vdev_psize - 1) + 1;
+	}
+
+	return (rsize);
+}
+
+vdev_t *
+vdev_lookup_top(spa_t *spa, uint64_t vdev)
+{
+	vdev_t *rvd = spa->spa_root_vdev;
+
+	ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
+
+	if (vdev < rvd->vdev_children) {
+		ASSERT(rvd->vdev_child[vdev] != NULL);
+		return (rvd->vdev_child[vdev]);
+	}
+
+	return (NULL);
+}
+
+vdev_t *
+vdev_lookup_by_guid(vdev_t *vd, uint64_t guid)
+{
+	int c;
+	vdev_t *mvd;
+
+	if (vd->vdev_guid == guid)
+		return (vd);
+
+	for (c = 0; c < vd->vdev_children; c++)
+		if ((mvd = vdev_lookup_by_guid(vd->vdev_child[c], guid)) !=
+		    NULL)
+			return (mvd);
+
+	return (NULL);
+}
+
+void
+vdev_add_child(vdev_t *pvd, vdev_t *cvd)
+{
+	size_t oldsize, newsize;
+	uint64_t id = cvd->vdev_id;
+	vdev_t **newchild;
+
+	ASSERT(spa_config_held(cvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
+	ASSERT(cvd->vdev_parent == NULL);
+
+	cvd->vdev_parent = pvd;
+
+	if (pvd == NULL)
+		return;
+
+	ASSERT(id >= pvd->vdev_children || pvd->vdev_child[id] == NULL);
+
+	oldsize = pvd->vdev_children * sizeof (vdev_t *);
+	pvd->vdev_children = MAX(pvd->vdev_children, id + 1);
+	newsize = pvd->vdev_children * sizeof (vdev_t *);
+
+	newchild = kmem_zalloc(newsize, KM_SLEEP);
+	if (pvd->vdev_child != NULL) {
+		bcopy(pvd->vdev_child, newchild, oldsize);
+		kmem_free(pvd->vdev_child, oldsize);
+	}
+
+	pvd->vdev_child = newchild;
+	pvd->vdev_child[id] = cvd;
+
+	cvd->vdev_top = (pvd->vdev_top ? pvd->vdev_top: cvd);
+	ASSERT(cvd->vdev_top->vdev_parent->vdev_parent == NULL);
+
+	/*
+	 * Walk up all ancestors to update guid sum.
+	 */
+	for (; pvd != NULL; pvd = pvd->vdev_parent)
+		pvd->vdev_guid_sum += cvd->vdev_guid_sum;
+
+	if (cvd->vdev_ops->vdev_op_leaf)
+		cvd->vdev_spa->spa_scrub_maxinflight += zfs_scrub_limit;
+}
+
+void
+vdev_remove_child(vdev_t *pvd, vdev_t *cvd)
+{
+	int c;
+	uint_t id = cvd->vdev_id;
+
+	ASSERT(cvd->vdev_parent == pvd);
+
+	if (pvd == NULL)
+		return;
+
+	ASSERT(id < pvd->vdev_children);
+	ASSERT(pvd->vdev_child[id] == cvd);
+
+	pvd->vdev_child[id] = NULL;
+	cvd->vdev_parent = NULL;
+
+	for (c = 0; c < pvd->vdev_children; c++)
+		if (pvd->vdev_child[c])
+			break;
+
+	if (c == pvd->vdev_children) {
+		kmem_free(pvd->vdev_child, c * sizeof (vdev_t *));
+		pvd->vdev_child = NULL;
+		pvd->vdev_children = 0;
+	}
+
+	/*
+	 * Walk up all ancestors to update guid sum.
+	 */
+	for (; pvd != NULL; pvd = pvd->vdev_parent)
+		pvd->vdev_guid_sum -= cvd->vdev_guid_sum;
+
+	if (cvd->vdev_ops->vdev_op_leaf)
+		cvd->vdev_spa->spa_scrub_maxinflight -= zfs_scrub_limit;
+}
+
+/*
+ * Remove any holes in the child array.
+ */
+void
+vdev_compact_children(vdev_t *pvd)
+{
+	vdev_t **newchild, *cvd;
+	int oldc = pvd->vdev_children;
+	int newc, c;
+
+	ASSERT(spa_config_held(pvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
+
+	for (c = newc = 0; c < oldc; c++)
+		if (pvd->vdev_child[c])
+			newc++;
+
+	newchild = kmem_alloc(newc * sizeof (vdev_t *), KM_SLEEP);
+
+	for (c = newc = 0; c < oldc; c++) {
+		if ((cvd = pvd->vdev_child[c]) != NULL) {
+			newchild[newc] = cvd;
+			cvd->vdev_id = newc++;
+		}
+	}
+
+	kmem_free(pvd->vdev_child, oldc * sizeof (vdev_t *));
+	pvd->vdev_child = newchild;
+	pvd->vdev_children = newc;
+}
+
+/*
+ * Allocate and minimally initialize a vdev_t.
+ */
+static vdev_t *
+vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
+{
+	vdev_t *vd;
+
+	vd = kmem_zalloc(sizeof (vdev_t), KM_SLEEP);
+
+	if (spa->spa_root_vdev == NULL) {
+		ASSERT(ops == &vdev_root_ops);
+		spa->spa_root_vdev = vd;
+	}
+
+	if (guid == 0) {
+		if (spa->spa_root_vdev == vd) {
+			/*
+			 * The root vdev's guid will also be the pool guid,
+			 * which must be unique among all pools.
+			 */
+			while (guid == 0 || spa_guid_exists(guid, 0))
+				guid = spa_get_random(-1ULL);
+		} else {
+			/*
+			 * Any other vdev's guid must be unique within the pool.
+			 */
+			while (guid == 0 ||
+			    spa_guid_exists(spa_guid(spa), guid))
+				guid = spa_get_random(-1ULL);
+		}
+		ASSERT(!spa_guid_exists(spa_guid(spa), guid));
+	}
+
+	vd->vdev_spa = spa;
+	vd->vdev_id = id;
+	vd->vdev_guid = guid;
+	vd->vdev_guid_sum = guid;
+	vd->vdev_ops = ops;
+	vd->vdev_state = VDEV_STATE_CLOSED;
+
+	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);
+	txg_list_create(&vd->vdev_ms_list,
+	    offsetof(struct metaslab, ms_txg_node));
+	txg_list_create(&vd->vdev_dtl_list,
+	    offsetof(struct vdev, vdev_dtl_node));
+	vd->vdev_stat.vs_timestamp = gethrtime();
+	vdev_queue_init(vd);
+	vdev_cache_init(vd);
+
+	return (vd);
+}
+
+/*
+ * Allocate a new vdev.  The 'alloctype' is used to control whether we are
+ * creating a new vdev or loading an existing one - the behavior is slightly
+ * different for each case.
+ */
+int
+vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent, uint_t id,
+    int alloctype)
+{
+	vdev_ops_t *ops;
+	char *type;
+	uint64_t guid = 0, islog, nparity;
+	vdev_t *vd;
+
+	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
+
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE, &type) != 0)
+		return (EINVAL);
+
+	if ((ops = vdev_getops(type)) == NULL)
+		return (EINVAL);
+
+	/*
+	 * If this is a load, get the vdev guid from the nvlist.
+	 * Otherwise, vdev_alloc_common() will generate one for us.
+	 */
+	if (alloctype == VDEV_ALLOC_LOAD) {
+		uint64_t label_id;
+
+		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ID, &label_id) ||
+		    label_id != id)
+			return (EINVAL);
+
+		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
+			return (EINVAL);
+	} else if (alloctype == VDEV_ALLOC_SPARE) {
+		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
+			return (EINVAL);
+	} else if (alloctype == VDEV_ALLOC_L2CACHE) {
+		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
+			return (EINVAL);
+	}
+
+	/*
+	 * The first allocated vdev must be of type 'root'.
+	 */
+	if (ops != &vdev_root_ops && spa->spa_root_vdev == NULL)
+		return (EINVAL);
+
+	/*
+	 * Determine whether we're a log vdev.
+	 */
+	islog = 0;
+	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_IS_LOG, &islog);
+	if (islog && spa_version(spa) < SPA_VERSION_SLOGS)
+		return (ENOTSUP);
+
+	/*
+	 * Set the nparity property for RAID-Z vdevs.
+	 */
+	nparity = -1ULL;
+	if (ops == &vdev_raidz_ops) {
+		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NPARITY,
+		    &nparity) == 0) {
+			/*
+			 * Currently, we can only support 2 parity devices.
+			 */
+			if (nparity == 0 || nparity > 2)
+				return (EINVAL);
+			/*
+			 * Older versions can only support 1 parity device.
+			 */
+			if (nparity == 2 &&
+			    spa_version(spa) < SPA_VERSION_RAID6)
+				return (ENOTSUP);
+		} else {
+			/*
+			 * We require the parity to be specified for SPAs that
+			 * support multiple parity levels.
+			 */
+			if (spa_version(spa) >= SPA_VERSION_RAID6)
+				return (EINVAL);
+			/*
+			 * Otherwise, we default to 1 parity device for RAID-Z.
+			 */
+			nparity = 1;
+		}
+	} else {
+		nparity = 0;
+	}
+	ASSERT(nparity != -1ULL);
+
+	vd = vdev_alloc_common(spa, id, guid, ops);
+
+	vd->vdev_islog = islog;
+	vd->vdev_nparity = nparity;
+
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &vd->vdev_path) == 0)
+		vd->vdev_path = spa_strdup(vd->vdev_path);
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_DEVID, &vd->vdev_devid) == 0)
+		vd->vdev_devid = spa_strdup(vd->vdev_devid);
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PHYS_PATH,
+	    &vd->vdev_physpath) == 0)
+		vd->vdev_physpath = spa_strdup(vd->vdev_physpath);
+
+	/*
+	 * Set the whole_disk property.  If it's not specified, leave the value
+	 * as -1.
+	 */
+	if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK,
+	    &vd->vdev_wholedisk) != 0)
+		vd->vdev_wholedisk = -1ULL;
+
+	/*
+	 * Look for the 'not present' flag.  This will only be set if the device
+	 * was not present at the time of import.
+	 */
+	if (!spa->spa_import_faulted)
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT,
+		    &vd->vdev_not_present);
+
+	/*
+	 * Get the alignment requirement.
+	 */
+	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT, &vd->vdev_ashift);
+
+	/*
+	 * If we're a top-level vdev, try to load the allocation parameters.
+	 */
+	if (parent && !parent->vdev_parent && alloctype == VDEV_ALLOC_LOAD) {
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY,
+		    &vd->vdev_ms_array);
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT,
+		    &vd->vdev_ms_shift);
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASIZE,
+		    &vd->vdev_asize);
+	}
+
+	/*
+	 * If we're a leaf vdev, try to load the DTL object and other state.
+	 */
+	if (vd->vdev_ops->vdev_op_leaf &&
+	    (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);
+			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_UNSPARE,
+			    &vd->vdev_unspare);
+		}
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_OFFLINE,
+		    &vd->vdev_offline);
+
+		/*
+		 * When importing a pool, we want to ignore the persistent fault
+		 * state, as the diagnosis made on another system may not be
+		 * valid in the current context.
+		 */
+		if (spa->spa_load_state == SPA_LOAD_OPEN) {
+			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_FAULTED,
+			    &vd->vdev_faulted);
+			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DEGRADED,
+			    &vd->vdev_degraded);
+			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REMOVED,
+			    &vd->vdev_removed);
+		}
+	}
+
+	/*
+	 * Add ourselves to the parent's list of children.
+	 */
+	vdev_add_child(parent, vd);
+
+	*vdp = vd;
+
+	return (0);
+}
+
+void
+vdev_free(vdev_t *vd)
+{
+	int c;
+	spa_t *spa = vd->vdev_spa;
+
+	/*
+	 * vdev_free() implies closing the vdev first.  This is simpler than
+	 * trying to ensure complicated semantics for all callers.
+	 */
+	vdev_close(vd);
+
+	ASSERT(!list_link_active(&vd->vdev_config_dirty_node));
+
+	/*
+	 * Free all children.
+	 */
+	for (c = 0; c < vd->vdev_children; c++)
+		vdev_free(vd->vdev_child[c]);
+
+	ASSERT(vd->vdev_child == NULL);
+	ASSERT(vd->vdev_guid_sum == vd->vdev_guid);
+
+	/*
+	 * Discard allocation state.
+	 */
+	if (vd == vd->vdev_top)
+		vdev_metaslab_fini(vd);
+
+	ASSERT3U(vd->vdev_stat.vs_space, ==, 0);
+	ASSERT3U(vd->vdev_stat.vs_dspace, ==, 0);
+	ASSERT3U(vd->vdev_stat.vs_alloc, ==, 0);
+
+	/*
+	 * Remove this vdev from its parent's child list.
+	 */
+	vdev_remove_child(vd->vdev_parent, vd);
+
+	ASSERT(vd->vdev_parent == NULL);
+
+	/*
+	 * Clean up vdev structure.
+	 */
+	vdev_queue_fini(vd);
+	vdev_cache_fini(vd);
+
+	if (vd->vdev_path)
+		spa_strfree(vd->vdev_path);
+	if (vd->vdev_devid)
+		spa_strfree(vd->vdev_devid);
+	if (vd->vdev_physpath)
+		spa_strfree(vd->vdev_physpath);
+
+	if (vd->vdev_isspare)
+		spa_spare_remove(vd);
+	if (vd->vdev_isl2cache)
+		spa_l2cache_remove(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);
+	mutex_exit(&vd->vdev_dtl_lock);
+	mutex_destroy(&vd->vdev_dtl_lock);
+	mutex_destroy(&vd->vdev_stat_lock);
+	mutex_destroy(&vd->vdev_probe_lock);
+
+	if (vd == spa->spa_root_vdev)
+		spa->spa_root_vdev = NULL;
+
+	kmem_free(vd, sizeof (vdev_t));
+}
+
+/*
+ * Transfer top-level vdev state from svd to tvd.
+ */
+static void
+vdev_top_transfer(vdev_t *svd, vdev_t *tvd)
+{
+	spa_t *spa = svd->vdev_spa;
+	metaslab_t *msp;
+	vdev_t *vd;
+	int t;
+
+	ASSERT(tvd == tvd->vdev_top);
+
+	tvd->vdev_ms_array = svd->vdev_ms_array;
+	tvd->vdev_ms_shift = svd->vdev_ms_shift;
+	tvd->vdev_ms_count = svd->vdev_ms_count;
+
+	svd->vdev_ms_array = 0;
+	svd->vdev_ms_shift = 0;
+	svd->vdev_ms_count = 0;
+
+	tvd->vdev_mg = svd->vdev_mg;
+	tvd->vdev_ms = svd->vdev_ms;
+
+	svd->vdev_mg = NULL;
+	svd->vdev_ms = NULL;
+
+	if (tvd->vdev_mg != NULL)
+		tvd->vdev_mg->mg_vd = tvd;
+
+	tvd->vdev_stat.vs_alloc = svd->vdev_stat.vs_alloc;
+	tvd->vdev_stat.vs_space = svd->vdev_stat.vs_space;
+	tvd->vdev_stat.vs_dspace = svd->vdev_stat.vs_dspace;
+
+	svd->vdev_stat.vs_alloc = 0;
+	svd->vdev_stat.vs_space = 0;
+	svd->vdev_stat.vs_dspace = 0;
+
+	for (t = 0; t < TXG_SIZE; t++) {
+		while ((msp = txg_list_remove(&svd->vdev_ms_list, t)) != NULL)
+			(void) txg_list_add(&tvd->vdev_ms_list, msp, t);
+		while ((vd = txg_list_remove(&svd->vdev_dtl_list, t)) != NULL)
+			(void) txg_list_add(&tvd->vdev_dtl_list, vd, t);
+		if (txg_list_remove_this(&spa->spa_vdev_txg_list, svd, t))
+			(void) txg_list_add(&spa->spa_vdev_txg_list, tvd, t);
+	}
+
+	if (list_link_active(&svd->vdev_config_dirty_node)) {
+		vdev_config_clean(svd);
+		vdev_config_dirty(tvd);
+	}
+
+	if (list_link_active(&svd->vdev_state_dirty_node)) {
+		vdev_state_clean(svd);
+		vdev_state_dirty(tvd);
+	}
+
+	tvd->vdev_deflate_ratio = svd->vdev_deflate_ratio;
+	svd->vdev_deflate_ratio = 0;
+
+	tvd->vdev_islog = svd->vdev_islog;
+	svd->vdev_islog = 0;
+}
+
+static void
+vdev_top_update(vdev_t *tvd, vdev_t *vd)
+{
+	int c;
+
+	if (vd == NULL)
+		return;
+
+	vd->vdev_top = tvd;
+
+	for (c = 0; c < vd->vdev_children; c++)
+		vdev_top_update(tvd, vd->vdev_child[c]);
+}
+
+/*
+ * Add a mirror/replacing vdev above an existing vdev.
+ */
+vdev_t *
+vdev_add_parent(vdev_t *cvd, vdev_ops_t *ops)
+{
+	spa_t *spa = cvd->vdev_spa;
+	vdev_t *pvd = cvd->vdev_parent;
+	vdev_t *mvd;
+
+	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
+
+	mvd = vdev_alloc_common(spa, cvd->vdev_id, 0, ops);
+
+	mvd->vdev_asize = cvd->vdev_asize;
+	mvd->vdev_ashift = cvd->vdev_ashift;
+	mvd->vdev_state = cvd->vdev_state;
+
+	vdev_remove_child(pvd, cvd);
+	vdev_add_child(pvd, mvd);
+	cvd->vdev_id = mvd->vdev_children;
+	vdev_add_child(mvd, cvd);
+	vdev_top_update(cvd->vdev_top, cvd->vdev_top);
+
+	if (mvd == mvd->vdev_top)
+		vdev_top_transfer(cvd, mvd);
+
+	return (mvd);
+}
+
+/*
+ * Remove a 1-way mirror/replacing vdev from the tree.
+ */
+void
+vdev_remove_parent(vdev_t *cvd)
+{
+	vdev_t *mvd = cvd->vdev_parent;
+	vdev_t *pvd = mvd->vdev_parent;
+
+	ASSERT(spa_config_held(cvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
+
+	ASSERT(mvd->vdev_children == 1);
+	ASSERT(mvd->vdev_ops == &vdev_mirror_ops ||
+	    mvd->vdev_ops == &vdev_replacing_ops ||
+	    mvd->vdev_ops == &vdev_spare_ops);
+	cvd->vdev_ashift = mvd->vdev_ashift;
+
+	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;
+	cvd->vdev_id = mvd->vdev_id;
+	vdev_add_child(pvd, cvd);
+	vdev_top_update(cvd->vdev_top, cvd->vdev_top);
+
+	if (cvd == cvd->vdev_top)
+		vdev_top_transfer(mvd, cvd);
+
+	ASSERT(mvd->vdev_children == 0);
+	vdev_free(mvd);
+}
+
+int
+vdev_metaslab_init(vdev_t *vd, uint64_t txg)
+{
+	spa_t *spa = vd->vdev_spa;
+	objset_t *mos = spa->spa_meta_objset;
+	metaslab_class_t *mc;
+	uint64_t m;
+	uint64_t oldc = vd->vdev_ms_count;
+	uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
+	metaslab_t **mspp;
+	int error;
+
+	if (vd->vdev_ms_shift == 0)	/* not being allocated from yet */
+		return (0);
+
+	ASSERT(oldc <= newc);
+
+	if (vd->vdev_islog)
+		mc = spa->spa_log_class;
+	else
+		mc = spa->spa_normal_class;
+
+	if (vd->vdev_mg == NULL)
+		vd->vdev_mg = metaslab_group_create(mc, vd);
+
+	mspp = kmem_zalloc(newc * sizeof (*mspp), KM_SLEEP);
+
+	if (oldc != 0) {
+		bcopy(vd->vdev_ms, mspp, oldc * sizeof (*mspp));
+		kmem_free(vd->vdev_ms, oldc * sizeof (*mspp));
+	}
+
+	vd->vdev_ms = mspp;
+	vd->vdev_ms_count = newc;
+
+	for (m = oldc; m < newc; m++) {
+		space_map_obj_t smo = { 0, 0, 0 };
+		if (txg == 0) {
+			uint64_t object = 0;
+			error = dmu_read(mos, vd->vdev_ms_array,
+			    m * sizeof (uint64_t), sizeof (uint64_t), &object);
+			if (error)
+				return (error);
+			if (object != 0) {
+				dmu_buf_t *db;
+				error = dmu_bonus_hold(mos, object, FTAG, &db);
+				if (error)
+					return (error);
+				ASSERT3U(db->db_size, >=, sizeof (smo));
+				bcopy(db->db_data, &smo, sizeof (smo));
+				ASSERT3U(smo.smo_object, ==, object);
+				dmu_buf_rele(db, FTAG);
+			}
+		}
+		vd->vdev_ms[m] = metaslab_init(vd->vdev_mg, &smo,
+		    m << vd->vdev_ms_shift, 1ULL << vd->vdev_ms_shift, txg);
+	}
+
+	return (0);
+}
+
+void
+vdev_metaslab_fini(vdev_t *vd)
+{
+	uint64_t m;
+	uint64_t count = vd->vdev_ms_count;
+
+	if (vd->vdev_ms != NULL) {
+		for (m = 0; m < count; m++)
+			if (vd->vdev_ms[m] != NULL)
+				metaslab_fini(vd->vdev_ms[m]);
+		kmem_free(vd->vdev_ms, count * sizeof (metaslab_t *));
+		vd->vdev_ms = NULL;
+	}
+}
+
+typedef struct vdev_probe_stats {
+	boolean_t	vps_readable;
+	boolean_t	vps_writeable;
+	int		vps_flags;
+	zio_t		*vps_root;
+	vdev_t		*vps_vd;
+} vdev_probe_stats_t;
+
+static void
+vdev_probe_done(zio_t *zio)
+{
+	vdev_probe_stats_t *vps = zio->io_private;
+	vdev_t *vd = vps->vps_vd;
+
+	if (zio->io_type == ZIO_TYPE_READ) {
+		ASSERT(zio->io_vd == vd);
+		if (zio->io_error == 0)
+			vps->vps_readable = 1;
+		if (zio->io_error == 0 && (spa_mode & FWRITE)) {
+			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,
+			    ZIO_PRIORITY_SYNC_WRITE, vps->vps_flags, B_TRUE));
+		} else {
+			zio_buf_free(zio->io_data, zio->io_size);
+		}
+	} else if (zio->io_type == ZIO_TYPE_WRITE) {
+		ASSERT(zio->io_vd == vd);
+		if (zio->io_error == 0)
+			vps->vps_writeable = 1;
+		zio_buf_free(zio->io_data, zio->io_size);
+	} else if (zio->io_type == ZIO_TYPE_NULL) {
+		ASSERT(zio->io_vd == NULL);
+		ASSERT(zio == vps->vps_root);
+
+		vd->vdev_cant_read |= !vps->vps_readable;
+		vd->vdev_cant_write |= !vps->vps_writeable;
+
+		if (vdev_readable(vd) &&
+		    (vdev_writeable(vd) || !(spa_mode & FWRITE))) {
+			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);
+			zio->io_error = ENXIO;
+		}
+		kmem_free(vps, sizeof (*vps));
+	}
+}
+
+/*
+ * Determine whether this device is accessible by reading and writing
+ * to several known locations: the pad regions of each vdev label
+ * but the first (which we leave alone in case it contains a VTOC).
+ */
+zio_t *
+vdev_probe(vdev_t *vd, zio_t *pio)
+{
+	spa_t *spa = vd->vdev_spa;
+	vdev_probe_stats_t *vps;
+	zio_t *zio;
+
+	vps = kmem_zalloc(sizeof (*vps), KM_SLEEP);
+
+	vps->vps_flags = ZIO_FLAG_CANFAIL | ZIO_FLAG_PROBE |
+	    ZIO_FLAG_DONT_CACHE | ZIO_FLAG_DONT_AGGREGATE | ZIO_FLAG_DONT_RETRY;
+
+	if (spa_config_held(spa, SCL_ZIO, RW_WRITER)) {
+		/*
+		 * vdev_cant_read and vdev_cant_write can only transition
+		 * from TRUE to FALSE when we have the SCL_ZIO lock as writer;
+		 * otherwise they can only transition from FALSE to TRUE.
+		 * This ensures that any zio looking at these values can
+		 * assume that failures persist for the life of the I/O.
+		 * That's important because when a device has intermittent
+		 * connectivity problems, we want to ensure that they're
+		 * ascribed to the device (ENXIO) and not the zio (EIO).
+		 *
+		 * Since we hold SCL_ZIO as writer here, clear both values
+		 * so the probe can reevaluate from first principles.
+		 */
+		vps->vps_flags |= ZIO_FLAG_CONFIG_WRITER;
+		vd->vdev_cant_read = B_FALSE;
+		vd->vdev_cant_write = B_FALSE;
+	}
+
+	ASSERT(vd->vdev_ops->vdev_op_leaf);
+
+	zio = zio_null(pio, spa, vdev_probe_done, vps, vps->vps_flags);
+
+	vps->vps_root = zio;
+	vps->vps_vd = vd;
+
+	for (int l = 1; l < VDEV_LABELS; l++) {
+		zio_nowait(zio_read_phys(zio, vd,
+		    vdev_label_offset(vd->vdev_psize, l,
+		    offsetof(vdev_label_t, vl_pad)),
+		    VDEV_SKIP_SIZE, zio_buf_alloc(VDEV_SKIP_SIZE),
+		    ZIO_CHECKSUM_OFF, vdev_probe_done, vps,
+		    ZIO_PRIORITY_SYNC_READ, vps->vps_flags, B_TRUE));
+	}
+
+	return (zio);
+}
+
+/*
+ * Prepare a virtual device for access.
+ */
+int
+vdev_open(vdev_t *vd)
+{
+	int error;
+	int c;
+	uint64_t osize = 0;
+	uint64_t asize, psize;
+	uint64_t ashift = 0;
+
+	ASSERT(vd->vdev_state == VDEV_STATE_CLOSED ||
+	    vd->vdev_state == VDEV_STATE_CANT_OPEN ||
+	    vd->vdev_state == VDEV_STATE_OFFLINE);
+
+	vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
+
+	if (!vd->vdev_removed && vd->vdev_faulted) {
+		ASSERT(vd->vdev_children == 0);
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_FAULTED,
+		    VDEV_AUX_ERR_EXCEEDED);
+		return (ENXIO);
+	} else if (vd->vdev_offline) {
+		ASSERT(vd->vdev_children == 0);
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE, VDEV_AUX_NONE);
+		return (ENXIO);
+	}
+
+	error = vd->vdev_ops->vdev_op_open(vd, &osize, &ashift);
+
+	if (zio_injection_enabled && error == 0)
+		error = zio_handle_device_injection(vd, ENXIO);
+
+	if (error) {
+		if (vd->vdev_removed &&
+		    vd->vdev_stat.vs_aux != VDEV_AUX_OPEN_FAILED)
+			vd->vdev_removed = B_FALSE;
+
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+		    vd->vdev_stat.vs_aux);
+		return (error);
+	}
+
+	vd->vdev_removed = B_FALSE;
+
+	if (vd->vdev_degraded) {
+		ASSERT(vd->vdev_children == 0);
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_DEGRADED,
+		    VDEV_AUX_ERR_EXCEEDED);
+	} else {
+		vd->vdev_state = VDEV_STATE_HEALTHY;
+	}
+
+	for (c = 0; c < vd->vdev_children; c++)
+		if (vd->vdev_child[c]->vdev_state != VDEV_STATE_HEALTHY) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_DEGRADED,
+			    VDEV_AUX_NONE);
+			break;
+		}
+
+	osize = P2ALIGN(osize, (uint64_t)sizeof (vdev_label_t));
+
+	if (vd->vdev_children == 0) {
+		if (osize < SPA_MINDEVSIZE) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_TOO_SMALL);
+			return (EOVERFLOW);
+		}
+		psize = osize;
+		asize = osize - (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE);
+	} else {
+		if (vd->vdev_parent != NULL && osize < SPA_MINDEVSIZE -
+		    (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE)) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_TOO_SMALL);
+			return (EOVERFLOW);
+		}
+		psize = 0;
+		asize = osize;
+	}
+
+	vd->vdev_psize = psize;
+
+	if (vd->vdev_asize == 0) {
+		/*
+		 * This is the first-ever open, so use the computed values.
+		 * For testing purposes, a higher ashift can be requested.
+		 */
+		vd->vdev_asize = asize;
+		vd->vdev_ashift = MAX(ashift, vd->vdev_ashift);
+	} else {
+		/*
+		 * Make sure the alignment requirement hasn't increased.
+		 */
+		if (ashift > vd->vdev_top->vdev_ashift) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_BAD_LABEL);
+			return (EINVAL);
+		}
+
+		/*
+		 * Make sure the device hasn't shrunk.
+		 */
+		if (asize < vd->vdev_asize) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_BAD_LABEL);
+			return (EINVAL);
+		}
+
+		/*
+		 * If all children are healthy and the asize has increased,
+		 * then we've experienced dynamic LUN growth.
+		 */
+		if (vd->vdev_state == VDEV_STATE_HEALTHY &&
+		    asize > vd->vdev_asize) {
+			vd->vdev_asize = asize;
+		}
+	}
+
+	/*
+	 * Ensure we can issue some IO before declaring the
+	 * vdev open for business.
+	 */
+	if (vd->vdev_ops->vdev_op_leaf &&
+	    (error = zio_wait(vdev_probe(vd, NULL))) != 0) {
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+		    VDEV_AUX_IO_FAILURE);
+		return (error);
+	}
+
+	/*
+	 * If this is a top-level vdev, compute the raidz-deflation
+	 * ratio.  Note, we hard-code in 128k (1<<17) because it is the
+	 * current "typical" blocksize.  Even if SPA_MAXBLOCKSIZE
+	 * changes, this algorithm must never change, or we will
+	 * inconsistently account for existing bp's.
+	 */
+	if (vd->vdev_top == vd) {
+		vd->vdev_deflate_ratio = (1<<17) /
+		    (vdev_psize_to_asize(vd, 1<<17) >> SPA_MINBLOCKSHIFT);
+	}
+
+	/*
+	 * 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.
+	 */
+	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);
+	}
+
+	return (0);
+}
+
+/*
+ * Called once the vdevs are all opened, this routine validates the label
+ * contents.  This needs to be done before vdev_load() so that we don't
+ * inadvertently do repair I/Os to the wrong device.
+ *
+ * This function will only return failure if one of the vdevs indicates that it
+ * has since been destroyed or exported.  This is only possible if
+ * /etc/zfs/zpool.cache was readonly at the time.  Otherwise, the vdev state
+ * will be updated but the function will return 0.
+ */
+int
+vdev_validate(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+	int c;
+	nvlist_t *label;
+	uint64_t guid, top_guid;
+	uint64_t state;
+
+	for (c = 0; c < vd->vdev_children; c++)
+		if (vdev_validate(vd->vdev_child[c]) != 0)
+			return (EBADF);
+
+	/*
+	 * If the device has already failed, or was marked offline, don't do
+	 * any further validation.  Otherwise, label I/O will fail and we will
+	 * overwrite the previous state.
+	 */
+	if (vd->vdev_ops->vdev_op_leaf && vdev_readable(vd)) {
+
+		if ((label = vdev_label_read_config(vd)) == NULL) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_BAD_LABEL);
+			return (0);
+		}
+
+		if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID,
+		    &guid) != 0 || guid != spa_guid(spa)) {
+			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_CORRUPT_DATA);
+			nvlist_free(label);
+			return (0);
+		}
+
+		/*
+		 * If this vdev just became a top-level vdev because its
+		 * sibling was detached, it will have adopted the parent's
+		 * vdev guid -- but the label may or may not be on disk yet.
+		 * Fortunately, either version of the label will have the
+		 * same top guid, so if we're a top-level vdev, we can
+		 * safely compare to that instead.
+		 */
+		if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID,
+		    &guid) != 0 ||
+		    nvlist_lookup_uint64(label, ZPOOL_CONFIG_TOP_GUID,
+		    &top_guid) != 0 ||
+		    (vd->vdev_guid != guid &&
+		    (vd->vdev_guid != top_guid || vd != vd->vdev_top))) {
+			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_CORRUPT_DATA);
+			nvlist_free(label);
+			return (0);
+		}
+
+		if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
+		    &state) != 0) {
+			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_CORRUPT_DATA);
+			nvlist_free(label);
+			return (0);
+		}
+
+		nvlist_free(label);
+
+		if (spa->spa_load_state == SPA_LOAD_OPEN &&
+		    state != POOL_STATE_ACTIVE)
+			return (EBADF);
+
+		/*
+		 * If we were able to open and validate a vdev that was
+		 * previously marked permanently unavailable, clear that state
+		 * now.
+		 */
+		if (vd->vdev_not_present)
+			vd->vdev_not_present = 0;
+	}
+
+	return (0);
+}
+
+/*
+ * Close a virtual device.
+ */
+void
+vdev_close(vdev_t *vd)
+{
+	vd->vdev_ops->vdev_op_close(vd);
+
+	vdev_cache_purge(vd);
+
+	/*
+	 * We record the previous state before we close it, so  that if we are
+	 * doing a reopen(), we don't generate FMA ereports if we notice that
+	 * it's still faulted.
+	 */
+	vd->vdev_prevstate = vd->vdev_state;
+
+	if (vd->vdev_offline)
+		vd->vdev_state = VDEV_STATE_OFFLINE;
+	else
+		vd->vdev_state = VDEV_STATE_CLOSED;
+	vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
+}
+
+void
+vdev_reopen(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+
+	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
+
+	vdev_close(vd);
+	(void) vdev_open(vd);
+
+	/*
+	 * Call vdev_validate() here to make sure we have the same device.
+	 * Otherwise, a device with an invalid label could be successfully
+	 * opened in response to vdev_reopen().
+	 */
+	if (vd->vdev_aux) {
+		(void) vdev_validate_aux(vd);
+		if (vdev_readable(vd) && vdev_writeable(vd) &&
+		    !l2arc_vdev_present(vd)) {
+			uint64_t size = vdev_get_rsize(vd);
+			l2arc_add_vdev(spa, vd,
+			    VDEV_LABEL_START_SIZE,
+			    size - VDEV_LABEL_START_SIZE);
+		}
+	} else {
+		(void) vdev_validate(vd);
+	}
+
+	/*
+	 * Reassess parent vdev's health.
+	 */
+	vdev_propagate_state(vd);
+}
+
+int
+vdev_create(vdev_t *vd, uint64_t txg, boolean_t isreplacing)
+{
+	int error;
+
+	/*
+	 * Normally, partial opens (e.g. of a mirror) are allowed.
+	 * For a create, however, we want to fail the request if
+	 * there are any components we can't open.
+	 */
+	error = vdev_open(vd);
+
+	if (error || vd->vdev_state != VDEV_STATE_HEALTHY) {
+		vdev_close(vd);
+		return (error ? error : ENXIO);
+	}
+
+	/*
+	 * Recursively initialize all labels.
+	 */
+	if ((error = vdev_label_init(vd, txg, isreplacing ?
+	    VDEV_LABEL_REPLACE : VDEV_LABEL_CREATE)) != 0) {
+		vdev_close(vd);
+		return (error);
+	}
+
+	return (0);
+}
+
+/*
+ * The is the latter half of vdev_create().  It is distinct because it
+ * involves initiating transactions in order to do metaslab creation.
+ * For creation, we want to try to create all vdevs at once and then undo it
+ * if anything fails; this is much harder if we have pending transactions.
+ */
+void
+vdev_init(vdev_t *vd, uint64_t txg)
+{
+	/*
+	 * Aim for roughly 200 metaslabs per vdev.
+	 */
+	vd->vdev_ms_shift = highbit(vd->vdev_asize / 200);
+	vd->vdev_ms_shift = MAX(vd->vdev_ms_shift, SPA_MAXBLOCKSHIFT);
+
+	/*
+	 * Initialize the vdev's metaslabs.  This can't fail because
+	 * there's nothing to read when creating all new metaslabs.
+	 */
+	VERIFY(vdev_metaslab_init(vd, txg) == 0);
+}
+
+void
+vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg)
+{
+	ASSERT(vd == vd->vdev_top);
+	ASSERT(ISP2(flags));
+
+	if (flags & VDD_METASLAB)
+		(void) txg_list_add(&vd->vdev_ms_list, arg, txg);
+
+	if (flags & VDD_DTL)
+		(void) txg_list_add(&vd->vdev_dtl_list, arg, txg);
+
+	(void) txg_list_add(&vd->vdev_spa->spa_vdev_txg_list, vd, txg);
+}
+
+void
+vdev_dtl_dirty(space_map_t *sm, uint64_t txg, uint64_t size)
+{
+	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)
+{
+	int dirty;
+
+	/*
+	 * Quick test without the lock -- covers the common case that
+	 * there are no dirty time segments.
+	 */
+	if (sm->sm_space == 0)
+		return (0);
+
+	mutex_enter(sm->sm_lock);
+	dirty = space_map_contains(sm, txg, size);
+	mutex_exit(sm->sm_lock);
+
+	return (dirty);
+}
+
+/*
+ * Reassess DTLs after a config change or scrub completion.
+ */
+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;
+
+	ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));
+
+	if (vd->vdev_children == 0) {
+		mutex_enter(&vd->vdev_dtl_lock);
+		if (scrub_txg != 0 &&
+		    (spa->spa_scrub_started || spa->spa_scrub_errors == 0)) {
+			/* XXX should check scrub_done? */
+			/*
+			 * We completed a scrub up to scrub_txg.  If we
+			 * did it without rebooting, then the scrub dtl
+			 * 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.
+			 */
+			space_map_excise(&vd->vdev_dtl_map, 0, scrub_txg);
+			space_map_union(&vd->vdev_dtl_map, &vd->vdev_dtl_scrub);
+		}
+		if (scrub_done)
+			space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
+		mutex_exit(&vd->vdev_dtl_lock);
+
+		if (txg != 0)
+			vdev_dirty(vd->vdev_top, VDD_DTL, vd, txg);
+		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);
+	}
+
+	if (vd == spa->spa_root_vdev)
+		mutex_exit(&spa->spa_scrub_lock);
+}
+
+static int
+vdev_dtl_load(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+	space_map_obj_t *smo = &vd->vdev_dtl;
+	objset_t *mos = spa->spa_meta_objset;
+	dmu_buf_t *db;
+	int error;
+
+	ASSERT(vd->vdev_children == 0);
+
+	if (smo->smo_object == 0)
+		return (0);
+
+	if ((error = dmu_bonus_hold(mos, smo->smo_object, FTAG, &db)) != 0)
+		return (error);
+
+	ASSERT3U(db->db_size, >=, sizeof (*smo));
+	bcopy(db->db_data, smo, sizeof (*smo));
+	dmu_buf_rele(db, FTAG);
+
+	mutex_enter(&vd->vdev_dtl_lock);
+	error = space_map_load(&vd->vdev_dtl_map, NULL, SM_ALLOC, smo, mos);
+	mutex_exit(&vd->vdev_dtl_lock);
+
+	return (error);
+}
+
+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;
+	objset_t *mos = spa->spa_meta_objset;
+	space_map_t smsync;
+	kmutex_t smlock;
+	dmu_buf_t *db;
+	dmu_tx_t *tx;
+
+	tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
+
+	if (vd->vdev_detached) {
+		if (smo->smo_object != 0) {
+			int err = dmu_object_free(mos, smo->smo_object, tx);
+			ASSERT3U(err, ==, 0);
+			smo->smo_object = 0;
+		}
+		dmu_tx_commit(tx);
+		return;
+	}
+
+	if (smo->smo_object == 0) {
+		ASSERT(smo->smo_objsize == 0);
+		ASSERT(smo->smo_alloc == 0);
+		smo->smo_object = dmu_object_alloc(mos,
+		    DMU_OT_SPACE_MAP, 1 << SPACE_MAP_BLOCKSHIFT,
+		    DMU_OT_SPACE_MAP_HEADER, sizeof (*smo), tx);
+		ASSERT(smo->smo_object != 0);
+		vdev_config_dirty(vd->vdev_top);
+	}
+
+	mutex_init(&smlock, NULL, MUTEX_DEFAULT, NULL);
+
+	space_map_create(&smsync, sm->sm_start, sm->sm_size, sm->sm_shift,
+	    &smlock);
+
+	mutex_enter(&smlock);
+
+	mutex_enter(&vd->vdev_dtl_lock);
+	space_map_walk(sm, space_map_add, &smsync);
+	mutex_exit(&vd->vdev_dtl_lock);
+
+	space_map_truncate(smo, mos, tx);
+	space_map_sync(&smsync, SM_ALLOC, smo, mos, tx);
+
+	space_map_destroy(&smsync);
+
+	mutex_exit(&smlock);
+	mutex_destroy(&smlock);
+
+	VERIFY(0 == dmu_bonus_hold(mos, smo->smo_object, FTAG, &db));
+	dmu_buf_will_dirty(db, tx);
+	ASSERT3U(db->db_size, >=, sizeof (*smo));
+	bcopy(smo, db->db_data, sizeof (*smo));
+	dmu_buf_rele(db, FTAG);
+
+	dmu_tx_commit(tx);
+}
+
+/*
+ * Determine if resilver is needed, and if so the txg range.
+ */
+boolean_t
+vdev_resilver_needed(vdev_t *vd, uint64_t *minp, uint64_t *maxp)
+{
+	boolean_t needed = B_FALSE;
+	uint64_t thismin = UINT64_MAX;
+	uint64_t thismax = 0;
+
+	if (vd->vdev_children == 0) {
+		mutex_enter(&vd->vdev_dtl_lock);
+		if (vd->vdev_dtl_map.sm_space != 0 && vdev_writeable(vd)) {
+			space_seg_t *ss;
+
+			ss = avl_first(&vd->vdev_dtl_map.sm_root);
+			thismin = ss->ss_start - 1;
+			ss = avl_last(&vd->vdev_dtl_map.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++) {
+			vdev_t *cvd = vd->vdev_child[c];
+			uint64_t cmin, cmax;
+
+			if (vdev_resilver_needed(cvd, &cmin, &cmax)) {
+				thismin = MIN(thismin, cmin);
+				thismax = MAX(thismax, cmax);
+				needed = B_TRUE;
+			}
+		}
+	}
+
+	if (needed && minp) {
+		*minp = thismin;
+		*maxp = thismax;
+	}
+	return (needed);
+}
+
+void
+vdev_load(vdev_t *vd)
+{
+	int c;
+
+	/*
+	 * Recursively load all children.
+	 */
+	for (c = 0; c < vd->vdev_children; c++)
+		vdev_load(vd->vdev_child[c]);
+
+	/*
+	 * If this is a top-level vdev, initialize its metaslabs.
+	 */
+	if (vd == vd->vdev_top &&
+	    (vd->vdev_ashift == 0 || vd->vdev_asize == 0 ||
+	    vdev_metaslab_init(vd, 0) != 0))
+		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
+		    VDEV_AUX_CORRUPT_DATA);
+
+	/*
+	 * If this is a leaf vdev, load its DTL.
+	 */
+	if (vd->vdev_ops->vdev_op_leaf && vdev_dtl_load(vd) != 0)
+		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
+		    VDEV_AUX_CORRUPT_DATA);
+}
+
+/*
+ * The special vdev case is used for hot spares and l2cache devices.  Its
+ * sole purpose it to set the vdev state for the associated vdev.  To do this,
+ * we make sure that we can open the underlying device, then try to read the
+ * label, and make sure that the label is sane and that it hasn't been
+ * repurposed to another pool.
+ */
+int
+vdev_validate_aux(vdev_t *vd)
+{
+	nvlist_t *label;
+	uint64_t guid, version;
+	uint64_t state;
+
+	if (!vdev_readable(vd))
+		return (0);
+
+	if ((label = vdev_label_read_config(vd)) == NULL) {
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+		    VDEV_AUX_CORRUPT_DATA);
+		return (-1);
+	}
+
+	if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_VERSION, &version) != 0 ||
+	    version > SPA_VERSION ||
+	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &guid) != 0 ||
+	    guid != vd->vdev_guid ||
+	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE, &state) != 0) {
+		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+		    VDEV_AUX_CORRUPT_DATA);
+		nvlist_free(label);
+		return (-1);
+	}
+
+	/*
+	 * We don't actually check the pool state here.  If it's in fact in
+	 * use by another pool, we update this fact on the fly when requested.
+	 */
+	nvlist_free(label);
+	return (0);
+}
+
+void
+vdev_sync_done(vdev_t *vd, uint64_t txg)
+{
+	metaslab_t *msp;
+
+	while (msp = txg_list_remove(&vd->vdev_ms_list, TXG_CLEAN(txg)))
+		metaslab_sync_done(msp, txg);
+}
+
+void
+vdev_sync(vdev_t *vd, uint64_t txg)
+{
+	spa_t *spa = vd->vdev_spa;
+	vdev_t *lvd;
+	metaslab_t *msp;
+	dmu_tx_t *tx;
+
+	if (vd->vdev_ms_array == 0 && vd->vdev_ms_shift != 0) {
+		ASSERT(vd == vd->vdev_top);
+		tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
+		vd->vdev_ms_array = dmu_object_alloc(spa->spa_meta_objset,
+		    DMU_OT_OBJECT_ARRAY, 0, DMU_OT_NONE, 0, tx);
+		ASSERT(vd->vdev_ms_array != 0);
+		vdev_config_dirty(vd);
+		dmu_tx_commit(tx);
+	}
+
+	while ((msp = txg_list_remove(&vd->vdev_ms_list, txg)) != NULL) {
+		metaslab_sync(msp, txg);
+		(void) txg_list_add(&vd->vdev_ms_list, msp, TXG_CLEAN(txg));
+	}
+
+	while ((lvd = txg_list_remove(&vd->vdev_dtl_list, txg)) != NULL)
+		vdev_dtl_sync(lvd, txg);
+
+	(void) txg_list_add(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg));
+}
+
+uint64_t
+vdev_psize_to_asize(vdev_t *vd, uint64_t psize)
+{
+	return (vd->vdev_ops->vdev_op_asize(vd, psize));
+}
+
+/*
+ * Mark the given vdev faulted.  A faulted vdev behaves as if the device could
+ * not be opened, and no I/O is attempted.
+ */
+int
+vdev_fault(spa_t *spa, uint64_t guid)
+{
+	vdev_t *vd;
+
+	spa_vdev_state_enter(spa);
+
+	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
+		return (spa_vdev_state_exit(spa, NULL, ENODEV));
+
+	if (!vd->vdev_ops->vdev_op_leaf)
+		return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
+
+	/*
+	 * Faulted state takes precedence over degraded.
+	 */
+	vd->vdev_faulted = 1ULL;
+	vd->vdev_degraded = 0ULL;
+	vdev_set_state(vd, B_FALSE, VDEV_STATE_FAULTED, VDEV_AUX_ERR_EXCEEDED);
+
+	/*
+	 * If marking the vdev as faulted cause the top-level vdev to become
+	 * unavailable, then back off and simply mark the vdev as degraded
+	 * instead.
+	 */
+	if (vdev_is_dead(vd->vdev_top) && vd->vdev_aux == NULL) {
+		vd->vdev_degraded = 1ULL;
+		vd->vdev_faulted = 0ULL;
+
+		/*
+		 * If we reopen the device and it's not dead, only then do we
+		 * mark it degraded.
+		 */
+		vdev_reopen(vd);
+
+		if (vdev_readable(vd)) {
+			vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED,
+			    VDEV_AUX_ERR_EXCEEDED);
+		}
+	}
+
+	return (spa_vdev_state_exit(spa, vd, 0));
+}
+
+/*
+ * Mark the given vdev degraded.  A degraded vdev is purely an indication to the
+ * user that something is wrong.  The vdev continues to operate as normal as far
+ * as I/O is concerned.
+ */
+int
+vdev_degrade(spa_t *spa, uint64_t guid)
+{
+	vdev_t *vd;
+
+	spa_vdev_state_enter(spa);
+
+	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
+		return (spa_vdev_state_exit(spa, NULL, ENODEV));
+
+	if (!vd->vdev_ops->vdev_op_leaf)
+		return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
+
+	/*
+	 * If the vdev is already faulted, then don't do anything.
+	 */
+	if (vd->vdev_faulted || vd->vdev_degraded)
+		return (spa_vdev_state_exit(spa, NULL, 0));
+
+	vd->vdev_degraded = 1ULL;
+	if (!vdev_is_dead(vd))
+		vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED,
+		    VDEV_AUX_ERR_EXCEEDED);
+
+	return (spa_vdev_state_exit(spa, vd, 0));
+}
+
+/*
+ * Online the given vdev.  If 'unspare' is set, it implies two things.  First,
+ * any attached spare device should be detached when the device finishes
+ * resilvering.  Second, the online should be treated like a 'test' online case,
+ * so no FMA events are generated if the device fails to open.
+ */
+int
+vdev_online(spa_t *spa, uint64_t guid, uint64_t flags, vdev_state_t *newstate)
+{
+	vdev_t *vd;
+
+	spa_vdev_state_enter(spa);
+
+	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
+		return (spa_vdev_state_exit(spa, NULL, ENODEV));
+
+	if (!vd->vdev_ops->vdev_op_leaf)
+		return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
+
+	vd->vdev_offline = B_FALSE;
+	vd->vdev_tmpoffline = B_FALSE;
+	vd->vdev_checkremove = !!(flags & ZFS_ONLINE_CHECKREMOVE);
+	vd->vdev_forcefault = !!(flags & ZFS_ONLINE_FORCEFAULT);
+	vdev_reopen(vd->vdev_top);
+	vd->vdev_checkremove = vd->vdev_forcefault = B_FALSE;
+
+	if (newstate)
+		*newstate = vd->vdev_state;
+	if ((flags & ZFS_ONLINE_UNSPARE) &&
+	    !vdev_is_dead(vd) && vd->vdev_parent &&
+	    vd->vdev_parent->vdev_ops == &vdev_spare_ops &&
+	    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);
+}
+
+int
+vdev_offline(spa_t *spa, uint64_t guid, uint64_t flags)
+{
+	vdev_t *vd;
+
+	spa_vdev_state_enter(spa);
+
+	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
+		return (spa_vdev_state_exit(spa, NULL, ENODEV));
+
+	if (!vd->vdev_ops->vdev_op_leaf)
+		return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
+
+	/*
+	 * If the device isn't already offline, try to offline it.
+	 */
+	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 (vd->vdev_top->vdev_dtl_map.sm_space != 0)
+			return (spa_vdev_state_exit(spa, NULL, EBUSY));
+
+		/*
+		 * Offline this device and reopen its top-level vdev.
+		 * If this action results in the top-level vdev becoming
+		 * unusable, undo it and fail the request.
+		 */
+		vd->vdev_offline = B_TRUE;
+		vdev_reopen(vd->vdev_top);
+		if (vdev_is_dead(vd->vdev_top) && vd->vdev_aux == NULL) {
+			vd->vdev_offline = B_FALSE;
+			vdev_reopen(vd->vdev_top);
+			return (spa_vdev_state_exit(spa, NULL, EBUSY));
+		}
+	}
+
+	vd->vdev_tmpoffline = !!(flags & ZFS_OFFLINE_TEMPORARY);
+
+	return (spa_vdev_state_exit(spa, vd, 0));
+}
+
+/*
+ * Clear the error counts associated with this vdev.  Unlike vdev_online() and
+ * vdev_offline(), we assume the spa config is locked.  We also clear all
+ * children.  If 'vd' is NULL, then the user wants to clear all vdevs.
+ */
+void
+vdev_clear(spa_t *spa, vdev_t *vd)
+{
+	vdev_t *rvd = spa->spa_root_vdev;
+
+	ASSERT(spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
+
+	if (vd == NULL)
+		vd = rvd;
+
+	vd->vdev_stat.vs_read_errors = 0;
+	vd->vdev_stat.vs_write_errors = 0;
+	vd->vdev_stat.vs_checksum_errors = 0;
+
+	for (int c = 0; c < vd->vdev_children; c++)
+		vdev_clear(spa, vd->vdev_child[c]);
+
+	/*
+	 * If we're in the FAULTED state or have experienced failed I/O, then
+	 * clear the persistent state and attempt to reopen the device.  We
+	 * also mark the vdev config dirty, so that the new faulted state is
+	 * written out to disk.
+	 */
+	if (vd->vdev_faulted || vd->vdev_degraded ||
+	    !vdev_readable(vd) || !vdev_writeable(vd)) {
+
+		vd->vdev_faulted = vd->vdev_degraded = 0;
+		vd->vdev_cant_read = B_FALSE;
+		vd->vdev_cant_write = B_FALSE;
+
+		vdev_reopen(vd);
+
+		if (vd != rvd)
+			vdev_state_dirty(vd->vdev_top);
+
+		if (vd->vdev_aux == NULL && !vdev_is_dead(vd))
+			spa_async_request(spa, SPA_ASYNC_RESILVER);
+
+		spa_event_notify(spa, vd, ESC_ZFS_VDEV_CLEAR);
+	}
+}
+
+boolean_t
+vdev_is_dead(vdev_t *vd)
+{
+	return (vd->vdev_state < VDEV_STATE_DEGRADED);
+}
+
+boolean_t
+vdev_readable(vdev_t *vd)
+{
+	return (!vdev_is_dead(vd) && !vd->vdev_cant_read);
+}
+
+boolean_t
+vdev_writeable(vdev_t *vd)
+{
+	return (!vdev_is_dead(vd) && !vd->vdev_cant_write);
+}
+
+boolean_t
+vdev_allocatable(vdev_t *vd)
+{
+	/*
+	 * We currently allow allocations from vdevs which maybe 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.
+	 */
+	return (!(vdev_is_dead(vd) && vd->vdev_state != VDEV_STATE_CLOSED) &&
+	    !vd->vdev_cant_write);
+}
+
+boolean_t
+vdev_accessible(vdev_t *vd, zio_t *zio)
+{
+	ASSERT(zio->io_vd == vd);
+
+	if (vdev_is_dead(vd) || vd->vdev_remove_wanted)
+		return (B_FALSE);
+
+	if (zio->io_type == ZIO_TYPE_READ)
+		return (!vd->vdev_cant_read);
+
+	if (zio->io_type == ZIO_TYPE_WRITE)
+		return (!vd->vdev_cant_write);
+
+	return (B_TRUE);
+}
+
+/*
+ * Get statistics for the given vdev.
+ */
+void
+vdev_get_stats(vdev_t *vd, vdev_stat_t *vs)
+{
+	vdev_t *rvd = vd->vdev_spa->spa_root_vdev;
+
+	mutex_enter(&vd->vdev_stat_lock);
+	bcopy(&vd->vdev_stat, vs, sizeof (*vs));
+	vs->vs_scrub_errors = vd->vdev_spa->spa_scrub_errors;
+	vs->vs_timestamp = gethrtime() - vs->vs_timestamp;
+	vs->vs_state = vd->vdev_state;
+	vs->vs_rsize = vdev_get_rsize(vd);
+	mutex_exit(&vd->vdev_stat_lock);
+
+	/*
+	 * If we're getting stats on the root vdev, aggregate the I/O counts
+	 * over all top-level vdevs (i.e. the direct children of the root).
+	 */
+	if (vd == rvd) {
+		for (int c = 0; c < rvd->vdev_children; c++) {
+			vdev_t *cvd = rvd->vdev_child[c];
+			vdev_stat_t *cvs = &cvd->vdev_stat;
+
+			mutex_enter(&vd->vdev_stat_lock);
+			for (int t = 0; t < ZIO_TYPES; t++) {
+				vs->vs_ops[t] += cvs->vs_ops[t];
+				vs->vs_bytes[t] += cvs->vs_bytes[t];
+			}
+			vs->vs_scrub_examined += cvs->vs_scrub_examined;
+			mutex_exit(&vd->vdev_stat_lock);
+		}
+	}
+}
+
+void
+vdev_clear_stats(vdev_t *vd)
+{
+	mutex_enter(&vd->vdev_stat_lock);
+	vd->vdev_stat.vs_space = 0;
+	vd->vdev_stat.vs_dspace = 0;
+	vd->vdev_stat.vs_alloc = 0;
+	mutex_exit(&vd->vdev_stat_lock);
+}
+
+void
+vdev_stat_update(zio_t *zio, uint64_t psize)
+{
+	vdev_t *rvd = zio->io_spa->spa_root_vdev;
+	vdev_t *vd = zio->io_vd ? zio->io_vd : rvd;
+	vdev_t *pvd;
+	uint64_t txg = zio->io_txg;
+	vdev_stat_t *vs = &vd->vdev_stat;
+	zio_type_t type = zio->io_type;
+	int flags = zio->io_flags;
+
+	/*
+	 * If this i/o is a gang leader, it didn't do any actual work.
+	 */
+	if (zio->io_gang_tree)
+		return;
+
+	if (zio->io_error == 0) {
+		/*
+		 * If this is a root i/o, don't count it -- we've already
+		 * counted the top-level vdevs, and vdev_get_stats() will
+		 * aggregate them when asked.  This reduces contention on
+		 * the root vdev_stat_lock and implicitly handles blocks
+		 * that compress away to holes, for which there is no i/o.
+		 * (Holes never create vdev children, so all the counters
+		 * remain zero, which is what we want.)
+		 *
+		 * Note: this only applies to successful i/o (io_error == 0)
+		 * because unlike i/o counts, errors are not additive.
+		 * When reading a ditto block, for example, failure of
+		 * one top-level vdev does not imply a root-level error.
+		 */
+		if (vd == rvd)
+			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_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
+				vs->vs_self_healed += psize;
+			mutex_exit(&vd->vdev_stat_lock);
+		}
+		return;
+	}
+
+	if (flags & ZIO_FLAG_SPECULATIVE)
+		return;
+
+	mutex_enter(&vd->vdev_stat_lock);
+	if (type == ZIO_TYPE_READ) {
+		if (zio->io_error == ECKSUM)
+			vs->vs_checksum_errors++;
+		else
+			vs->vs_read_errors++;
+	}
+	if (type == ZIO_TYPE_WRITE)
+		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))
+				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);
+		}
+	}
+}
+
+void
+vdev_scrub_stat_update(vdev_t *vd, pool_scrub_type_t type, boolean_t complete)
+{
+	int c;
+	vdev_stat_t *vs = &vd->vdev_stat;
+
+	for (c = 0; c < vd->vdev_children; c++)
+		vdev_scrub_stat_update(vd->vdev_child[c], type, complete);
+
+	mutex_enter(&vd->vdev_stat_lock);
+
+	if (type == POOL_SCRUB_NONE) {
+		/*
+		 * Update completion and end time.  Leave everything else alone
+		 * so we can report what happened during the previous scrub.
+		 */
+		vs->vs_scrub_complete = complete;
+		vs->vs_scrub_end = gethrestime_sec();
+	} else {
+		vs->vs_scrub_type = type;
+		vs->vs_scrub_complete = 0;
+		vs->vs_scrub_examined = 0;
+		vs->vs_scrub_repaired = 0;
+		vs->vs_scrub_start = gethrestime_sec();
+		vs->vs_scrub_end = 0;
+	}
+
+	mutex_exit(&vd->vdev_stat_lock);
+}
+
+/*
+ * Update the in-core space usage stats for this vdev and the root vdev.
+ */
+void
+vdev_space_update(vdev_t *vd, int64_t space_delta, int64_t alloc_delta,
+    boolean_t update_root)
+{
+	int64_t dspace_delta = space_delta;
+	spa_t *spa = vd->vdev_spa;
+	vdev_t *rvd = spa->spa_root_vdev;
+
+	ASSERT(vd == vd->vdev_top);
+
+	/*
+	 * Apply the inverse of the psize-to-asize (ie. RAID-Z) space-expansion
+	 * factor.  We must calculate this here and not at the root vdev
+	 * because the root vdev's psize-to-asize is simply the max of its
+	 * childrens', thus not accurate enough for us.
+	 */
+	ASSERT((dspace_delta & (SPA_MINBLOCKSIZE-1)) == 0);
+	dspace_delta = (dspace_delta >> SPA_MINBLOCKSHIFT) *
+	    vd->vdev_deflate_ratio;
+
+	mutex_enter(&vd->vdev_stat_lock);
+	vd->vdev_stat.vs_space += space_delta;
+	vd->vdev_stat.vs_alloc += alloc_delta;
+	vd->vdev_stat.vs_dspace += dspace_delta;
+	mutex_exit(&vd->vdev_stat_lock);
+
+	if (update_root) {
+		ASSERT(rvd == vd->vdev_parent);
+		ASSERT(vd->vdev_ms_count != 0);
+
+		/*
+		 * Don't count non-normal (e.g. intent log) space as part of
+		 * the pool's capacity.
+		 */
+		if (vd->vdev_mg->mg_class != spa->spa_normal_class)
+			return;
+
+		mutex_enter(&rvd->vdev_stat_lock);
+		rvd->vdev_stat.vs_space += space_delta;
+		rvd->vdev_stat.vs_alloc += alloc_delta;
+		rvd->vdev_stat.vs_dspace += dspace_delta;
+		mutex_exit(&rvd->vdev_stat_lock);
+	}
+}
+
+/*
+ * Mark a top-level vdev's config as dirty, placing it on the dirty list
+ * so that it will be written out next time the vdev configuration is synced.
+ * If the root vdev is specified (vdev_top == NULL), dirty all top-level vdevs.
+ */
+void
+vdev_config_dirty(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+	vdev_t *rvd = spa->spa_root_vdev;
+	int c;
+
+	/*
+	 * If this is an aux vdev (as with l2cache devices), then we update the
+	 * vdev config manually and set the sync flag.
+	 */
+	if (vd->vdev_aux != NULL) {
+		spa_aux_vdev_t *sav = vd->vdev_aux;
+		nvlist_t **aux;
+		uint_t naux;
+
+		for (c = 0; c < sav->sav_count; c++) {
+			if (sav->sav_vdevs[c] == vd)
+				break;
+		}
+
+		if (c == sav->sav_count) {
+			/*
+			 * We're being removed.  There's nothing more to do.
+			 */
+			ASSERT(sav->sav_sync == B_TRUE);
+			return;
+		}
+
+		sav->sav_sync = B_TRUE;
+
+		VERIFY(nvlist_lookup_nvlist_array(sav->sav_config,
+		    ZPOOL_CONFIG_L2CACHE, &aux, &naux) == 0);
+
+		ASSERT(c < naux);
+
+		/*
+		 * Setting the nvlist in the middle if the array is a little
+		 * sketchy, but it will work.
+		 */
+		nvlist_free(aux[c]);
+		aux[c] = vdev_config_generate(spa, vd, B_TRUE, B_FALSE, B_TRUE);
+
+		return;
+	}
+
+	/*
+	 * The dirty list is protected by the SCL_CONFIG lock.  The caller
+	 * must either hold SCL_CONFIG as writer, or must be the sync thread
+	 * (which holds SCL_CONFIG as reader).  There's only one sync thread,
+	 * so this is sufficient to ensure mutual exclusion.
+	 */
+	ASSERT(spa_config_held(spa, SCL_CONFIG, RW_WRITER) ||
+	    (dsl_pool_sync_context(spa_get_dsl(spa)) &&
+	    spa_config_held(spa, SCL_CONFIG, RW_READER)));
+
+	if (vd == rvd) {
+		for (c = 0; c < rvd->vdev_children; c++)
+			vdev_config_dirty(rvd->vdev_child[c]);
+	} else {
+		ASSERT(vd == vd->vdev_top);
+
+		if (!list_link_active(&vd->vdev_config_dirty_node))
+			list_insert_head(&spa->spa_config_dirty_list, vd);
+	}
+}
+
+void
+vdev_config_clean(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+
+	ASSERT(spa_config_held(spa, SCL_CONFIG, RW_WRITER) ||
+	    (dsl_pool_sync_context(spa_get_dsl(spa)) &&
+	    spa_config_held(spa, SCL_CONFIG, RW_READER)));
+
+	ASSERT(list_link_active(&vd->vdev_config_dirty_node));
+	list_remove(&spa->spa_config_dirty_list, vd);
+}
+
+/*
+ * Mark a top-level vdev's state as dirty, so that the next pass of
+ * spa_sync() can convert this into vdev_config_dirty().  We distinguish
+ * the state changes from larger config changes because they require
+ * much less locking, and are often needed for administrative actions.
+ */
+void
+vdev_state_dirty(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+
+	ASSERT(vd == vd->vdev_top);
+
+	/*
+	 * The state list is protected by the SCL_STATE lock.  The caller
+	 * must either hold SCL_STATE as writer, or must be the sync thread
+	 * (which holds SCL_STATE as reader).  There's only one sync thread,
+	 * so this is sufficient to ensure mutual exclusion.
+	 */
+	ASSERT(spa_config_held(spa, SCL_STATE, RW_WRITER) ||
+	    (dsl_pool_sync_context(spa_get_dsl(spa)) &&
+	    spa_config_held(spa, SCL_STATE, RW_READER)));
+
+	if (!list_link_active(&vd->vdev_state_dirty_node))
+		list_insert_head(&spa->spa_state_dirty_list, vd);
+}
+
+void
+vdev_state_clean(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+
+	ASSERT(spa_config_held(spa, SCL_STATE, RW_WRITER) ||
+	    (dsl_pool_sync_context(spa_get_dsl(spa)) &&
+	    spa_config_held(spa, SCL_STATE, RW_READER)));
+
+	ASSERT(list_link_active(&vd->vdev_state_dirty_node));
+	list_remove(&spa->spa_state_dirty_list, vd);
+}
+
+/*
+ * Propagate vdev state up from children to parent.
+ */
+void
+vdev_propagate_state(vdev_t *vd)
+{
+	vdev_t *rvd = vd->vdev_spa->spa_root_vdev;
+	int degraded = 0, faulted = 0;
+	int corrupted = 0;
+	int c;
+	vdev_t *child;
+
+	if (vd->vdev_children > 0) {
+		for (c = 0; c < vd->vdev_children; c++) {
+			child = vd->vdev_child[c];
+
+			if (!vdev_readable(child) ||
+			    (!vdev_writeable(child) && (spa_mode & FWRITE))) {
+				/*
+				 * Root special: if there is a top-level log
+				 * device, treat the root vdev as if it were
+				 * degraded.
+				 */
+				if (child->vdev_islog && vd == rvd)
+					degraded++;
+				else
+					faulted++;
+			} else if (child->vdev_state <= VDEV_STATE_DEGRADED) {
+				degraded++;
+			}
+
+			if (child->vdev_stat.vs_aux == VDEV_AUX_CORRUPT_DATA)
+				corrupted++;
+		}
+
+		vd->vdev_ops->vdev_op_state_change(vd, faulted, degraded);
+
+		/*
+		 * Root special: if there is a top-level vdev that cannot be
+		 * opened due to corrupted metadata, then propagate the root
+		 * vdev's aux state as 'corrupt' rather than 'insufficient
+		 * replicas'.
+		 */
+		if (corrupted && vd == rvd &&
+		    rvd->vdev_state == VDEV_STATE_CANT_OPEN)
+			vdev_set_state(rvd, B_FALSE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_CORRUPT_DATA);
+	}
+
+	if (vd->vdev_parent)
+		vdev_propagate_state(vd->vdev_parent);
+}
+
+/*
+ * Set a vdev's state.  If this is during an open, we don't update the parent
+ * state, because we're in the process of opening children depth-first.
+ * Otherwise, we propagate the change to the parent.
+ *
+ * If this routine places a device in a faulted state, an appropriate ereport is
+ * generated.
+ */
+void
+vdev_set_state(vdev_t *vd, boolean_t isopen, vdev_state_t state, vdev_aux_t aux)
+{
+	uint64_t save_state;
+	spa_t *spa = vd->vdev_spa;
+
+	if (state == vd->vdev_state) {
+		vd->vdev_stat.vs_aux = aux;
+		return;
+	}
+
+	save_state = vd->vdev_state;
+
+	vd->vdev_state = state;
+	vd->vdev_stat.vs_aux = aux;
+
+	/*
+	 * If we are setting the vdev state to anything but an open state, then
+	 * always close the underlying device.  Otherwise, we keep accessible
+	 * but invalid devices open forever.  We don't call vdev_close() itself,
+	 * because that implies some extra checks (offline, etc) that we don't
+	 * want here.  This is limited to leaf devices, because otherwise
+	 * closing the device will affect other children.
+	 */
+	if (vdev_is_dead(vd) && vd->vdev_ops->vdev_op_leaf)
+		vd->vdev_ops->vdev_op_close(vd);
+
+	if (vd->vdev_removed &&
+	    state == VDEV_STATE_CANT_OPEN &&
+	    (aux == VDEV_AUX_OPEN_FAILED || vd->vdev_checkremove)) {
+		/*
+		 * If the previous state is set to VDEV_STATE_REMOVED, then this
+		 * device was previously marked removed and someone attempted to
+		 * reopen it.  If this failed due to a nonexistent device, then
+		 * keep the device in the REMOVED state.  We also let this be if
+		 * it is one of our special test online cases, which is only
+		 * attempting to online the device and shouldn't generate an FMA
+		 * fault.
+		 */
+		vd->vdev_state = VDEV_STATE_REMOVED;
+		vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
+	} else if (state == VDEV_STATE_REMOVED) {
+		/*
+		 * Indicate to the ZFS DE that this device has been removed, and
+		 * any recent errors should be ignored.
+		 */
+		zfs_post_remove(spa, vd);
+		vd->vdev_removed = B_TRUE;
+	} else if (state == VDEV_STATE_CANT_OPEN) {
+		/*
+		 * If we fail to open a vdev during an import, we mark it as
+		 * "not available", which signifies that it was never there to
+		 * begin with.  Failure to open such a device is not considered
+		 * an error.
+		 */
+		if (spa->spa_load_state == SPA_LOAD_IMPORT &&
+		    !spa->spa_import_faulted &&
+		    vd->vdev_ops->vdev_op_leaf)
+			vd->vdev_not_present = 1;
+
+		/*
+		 * Post the appropriate ereport.  If the 'prevstate' field is
+		 * set to something other than VDEV_STATE_UNKNOWN, it indicates
+		 * that this is part of a vdev_reopen().  In this case, we don't
+		 * want to post the ereport if the device was already in the
+		 * CANT_OPEN state beforehand.
+		 *
+		 * If the 'checkremove' flag is set, then this is an attempt to
+		 * online the device in response to an insertion event.  If we
+		 * hit this case, then we have detected an insertion event for a
+		 * faulted or offline device that wasn't in the removed state.
+		 * In this scenario, we don't post an ereport because we are
+		 * about to replace the device, or attempt an online with
+		 * vdev_forcefault, which will generate the fault for us.
+		 */
+		if ((vd->vdev_prevstate != state || vd->vdev_forcefault) &&
+		    !vd->vdev_not_present && !vd->vdev_checkremove &&
+		    vd != spa->spa_root_vdev) {
+			const char *class;
+
+			switch (aux) {
+			case VDEV_AUX_OPEN_FAILED:
+				class = FM_EREPORT_ZFS_DEVICE_OPEN_FAILED;
+				break;
+			case VDEV_AUX_CORRUPT_DATA:
+				class = FM_EREPORT_ZFS_DEVICE_CORRUPT_DATA;
+				break;
+			case VDEV_AUX_NO_REPLICAS:
+				class = FM_EREPORT_ZFS_DEVICE_NO_REPLICAS;
+				break;
+			case VDEV_AUX_BAD_GUID_SUM:
+				class = FM_EREPORT_ZFS_DEVICE_BAD_GUID_SUM;
+				break;
+			case VDEV_AUX_TOO_SMALL:
+				class = FM_EREPORT_ZFS_DEVICE_TOO_SMALL;
+				break;
+			case VDEV_AUX_BAD_LABEL:
+				class = FM_EREPORT_ZFS_DEVICE_BAD_LABEL;
+				break;
+			case VDEV_AUX_IO_FAILURE:
+				class = FM_EREPORT_ZFS_IO_FAILURE;
+				break;
+			default:
+				class = FM_EREPORT_ZFS_DEVICE_UNKNOWN;
+			}
+
+			zfs_ereport_post(class, spa, vd, NULL, save_state, 0);
+		}
+
+		/* Erase any notion of persistent removed state */
+		vd->vdev_removed = B_FALSE;
+	} else {
+		vd->vdev_removed = B_FALSE;
+	}
+
+	if (!isopen)
+		vdev_propagate_state(vd);
+}
+
+/*
+ * Check the vdev configuration to ensure that it's capable of supporting
+ * a root pool. Currently, we do not support RAID-Z or partial configuration.
+ * In addition, only a single top-level vdev is allowed and none of the leaves
+ * can be wholedisks.
+ */
+boolean_t
+vdev_is_bootable(vdev_t *vd)
+{
+	int c;
+
+	if (!vd->vdev_ops->vdev_op_leaf) {
+		char *vdev_type = vd->vdev_ops->vdev_op_type;
+
+		if (strcmp(vdev_type, VDEV_TYPE_ROOT) == 0 &&
+		    vd->vdev_children > 1) {
+			return (B_FALSE);
+		} else if (strcmp(vdev_type, VDEV_TYPE_RAIDZ) == 0 ||
+		    strcmp(vdev_type, VDEV_TYPE_MISSING) == 0) {
+			return (B_FALSE);
+		}
+	} else if (vd->vdev_wholedisk == 1) {
+		return (B_FALSE);
+	}
+
+	for (c = 0; c < vd->vdev_children; c++) {
+		if (!vdev_is_bootable(vd->vdev_child[c]))
+			return (B_FALSE);
+	}
+	return (B_TRUE);
+}