diff --git a/module/zfs/vdev.c b/module/zfs/vdev.c
index c74f72159dc9..11cc39ba3527 100644
--- a/module/zfs/vdev.c
+++ b/module/zfs/vdev.c
@@ -1,6514 +1,6515 @@
 /*
  * 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 https://opensource.org/licenses/CDDL-1.0.
  * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2021 by Delphix. All rights reserved.
  * Copyright 2017 Nexenta Systems, Inc.
  * Copyright (c) 2014 Integros [integros.com]
  * Copyright 2016 Toomas Soome <tsoome@me.com>
  * Copyright 2017 Joyent, Inc.
  * Copyright (c) 2017, Intel Corporation.
  * Copyright (c) 2019, Datto Inc. All rights reserved.
  * Copyright (c) 2021, Klara Inc.
  * Copyright (c) 2021, 2023 Hewlett Packard Enterprise Development LP.
  */
 
 #include <sys/zfs_context.h>
 #include <sys/fm/fs/zfs.h>
 #include <sys/spa.h>
 #include <sys/spa_impl.h>
 #include <sys/bpobj.h>
 #include <sys/dmu.h>
 #include <sys/dmu_tx.h>
 #include <sys/dsl_dir.h>
 #include <sys/vdev_impl.h>
 #include <sys/vdev_rebuild.h>
 #include <sys/vdev_draid.h>
 #include <sys/uberblock_impl.h>
 #include <sys/metaslab.h>
 #include <sys/metaslab_impl.h>
 #include <sys/space_map.h>
 #include <sys/space_reftree.h>
 #include <sys/zio.h>
 #include <sys/zap.h>
 #include <sys/fs/zfs.h>
 #include <sys/arc.h>
 #include <sys/zil.h>
 #include <sys/dsl_scan.h>
 #include <sys/vdev_raidz.h>
 #include <sys/abd.h>
 #include <sys/vdev_initialize.h>
 #include <sys/vdev_trim.h>
 #include <sys/vdev_raidz.h>
 #include <sys/zvol.h>
 #include <sys/zfs_ratelimit.h>
 #include "zfs_prop.h"
 
 /*
  * One metaslab from each (normal-class) vdev is used by the ZIL.  These are
  * called "embedded slog metaslabs", are referenced by vdev_log_mg, and are
  * part of the spa_embedded_log_class.  The metaslab with the most free space
  * in each vdev is selected for this purpose when the pool is opened (or a
  * vdev is added).  See vdev_metaslab_init().
  *
  * Log blocks can be allocated from the following locations.  Each one is tried
  * in order until the allocation succeeds:
  * 1. dedicated log vdevs, aka "slog" (spa_log_class)
  * 2. embedded slog metaslabs (spa_embedded_log_class)
  * 3. other metaslabs in normal vdevs (spa_normal_class)
  *
  * zfs_embedded_slog_min_ms disables the embedded slog if there are fewer
  * than this number of metaslabs in the vdev.  This ensures that we don't set
  * aside an unreasonable amount of space for the ZIL.  If set to less than
  * 1 << (spa_slop_shift + 1), on small pools the usable space may be reduced
  * (by more than 1<<spa_slop_shift) due to the embedded slog metaslab.
  */
 static uint_t zfs_embedded_slog_min_ms = 64;
 
 /* default target for number of metaslabs per top-level vdev */
 static uint_t zfs_vdev_default_ms_count = 200;
 
 /* minimum number of metaslabs per top-level vdev */
 static uint_t zfs_vdev_min_ms_count = 16;
 
 /* practical upper limit of total metaslabs per top-level vdev */
 static uint_t zfs_vdev_ms_count_limit = 1ULL << 17;
 
 /* lower limit for metaslab size (512M) */
 static uint_t zfs_vdev_default_ms_shift = 29;
 
 /* upper limit for metaslab size (16G) */
 static uint_t zfs_vdev_max_ms_shift = 34;
 
 int vdev_validate_skip = B_FALSE;
 
 /*
  * Since the DTL space map of a vdev is not expected to have a lot of
  * entries, we default its block size to 4K.
  */
 int zfs_vdev_dtl_sm_blksz = (1 << 12);
 
 /*
  * Rate limit slow IO (delay) events to this many per second.
  */
 static unsigned int zfs_slow_io_events_per_second = 20;
 
 /*
  * Rate limit deadman "hung IO" events to this many per second.
  */
 static unsigned int zfs_deadman_events_per_second = 1;
 
 /*
  * Rate limit checksum events after this many checksum errors per second.
  */
 static unsigned int zfs_checksum_events_per_second = 20;
 
 /*
  * Ignore errors during scrub/resilver.  Allows to work around resilver
  * upon import when there are pool errors.
  */
 static int zfs_scan_ignore_errors = 0;
 
 /*
  * vdev-wide space maps that have lots of entries written to them at
  * the end of each transaction can benefit from a higher I/O bandwidth
  * (e.g. vdev_obsolete_sm), thus we default their block size to 128K.
  */
 int zfs_vdev_standard_sm_blksz = (1 << 17);
 
 /*
  * Tunable parameter for debugging or performance analysis. Setting this
  * will cause pool corruption on power loss if a volatile out-of-order
  * write cache is enabled.
  */
 int zfs_nocacheflush = 0;
 
 /*
  * Maximum and minimum ashift values that can be automatically set based on
  * vdev's physical ashift (disk's physical sector size).  While ASHIFT_MAX
  * is higher than the maximum value, it is intentionally limited here to not
  * excessively impact pool space efficiency.  Higher ashift values may still
  * be forced by vdev logical ashift or by user via ashift property, but won't
  * be set automatically as a performance optimization.
  */
 uint_t zfs_vdev_max_auto_ashift = 14;
 uint_t zfs_vdev_min_auto_ashift = ASHIFT_MIN;
 
 void
 vdev_dbgmsg(vdev_t *vd, const char *fmt, ...)
 {
 	va_list adx;
 	char buf[256];
 
 	va_start(adx, fmt);
 	(void) vsnprintf(buf, sizeof (buf), fmt, adx);
 	va_end(adx);
 
 	if (vd->vdev_path != NULL) {
 		zfs_dbgmsg("%s vdev '%s': %s", vd->vdev_ops->vdev_op_type,
 		    vd->vdev_path, buf);
 	} else {
 		zfs_dbgmsg("%s-%llu vdev (guid %llu): %s",
 		    vd->vdev_ops->vdev_op_type,
 		    (u_longlong_t)vd->vdev_id,
 		    (u_longlong_t)vd->vdev_guid, buf);
 	}
 }
 
 void
 vdev_dbgmsg_print_tree(vdev_t *vd, int indent)
 {
 	char state[20];
 
 	if (vd->vdev_ishole || vd->vdev_ops == &vdev_missing_ops) {
 		zfs_dbgmsg("%*svdev %llu: %s", indent, "",
 		    (u_longlong_t)vd->vdev_id,
 		    vd->vdev_ops->vdev_op_type);
 		return;
 	}
 
 	switch (vd->vdev_state) {
 	case VDEV_STATE_UNKNOWN:
 		(void) snprintf(state, sizeof (state), "unknown");
 		break;
 	case VDEV_STATE_CLOSED:
 		(void) snprintf(state, sizeof (state), "closed");
 		break;
 	case VDEV_STATE_OFFLINE:
 		(void) snprintf(state, sizeof (state), "offline");
 		break;
 	case VDEV_STATE_REMOVED:
 		(void) snprintf(state, sizeof (state), "removed");
 		break;
 	case VDEV_STATE_CANT_OPEN:
 		(void) snprintf(state, sizeof (state), "can't open");
 		break;
 	case VDEV_STATE_FAULTED:
 		(void) snprintf(state, sizeof (state), "faulted");
 		break;
 	case VDEV_STATE_DEGRADED:
 		(void) snprintf(state, sizeof (state), "degraded");
 		break;
 	case VDEV_STATE_HEALTHY:
 		(void) snprintf(state, sizeof (state), "healthy");
 		break;
 	default:
 		(void) snprintf(state, sizeof (state), "<state %u>",
 		    (uint_t)vd->vdev_state);
 	}
 
 	zfs_dbgmsg("%*svdev %u: %s%s, guid: %llu, path: %s, %s", indent,
 	    "", (int)vd->vdev_id, vd->vdev_ops->vdev_op_type,
 	    vd->vdev_islog ? " (log)" : "",
 	    (u_longlong_t)vd->vdev_guid,
 	    vd->vdev_path ? vd->vdev_path : "N/A", state);
 
 	for (uint64_t i = 0; i < vd->vdev_children; i++)
 		vdev_dbgmsg_print_tree(vd->vdev_child[i], indent + 2);
 }
 
 /*
  * Virtual device management.
  */
 
 static vdev_ops_t *const vdev_ops_table[] = {
 	&vdev_root_ops,
 	&vdev_raidz_ops,
 	&vdev_draid_ops,
 	&vdev_draid_spare_ops,
 	&vdev_mirror_ops,
 	&vdev_replacing_ops,
 	&vdev_spare_ops,
 	&vdev_disk_ops,
 	&vdev_file_ops,
 	&vdev_missing_ops,
 	&vdev_hole_ops,
 	&vdev_indirect_ops,
 	NULL
 };
 
 /*
  * Given a vdev type, return the appropriate ops vector.
  */
 static vdev_ops_t *
 vdev_getops(const char *type)
 {
 	vdev_ops_t *ops, *const *opspp;
 
 	for (opspp = vdev_ops_table; (ops = *opspp) != NULL; opspp++)
 		if (strcmp(ops->vdev_op_type, type) == 0)
 			break;
 
 	return (ops);
 }
 
 /*
  * Given a vdev and a metaslab class, find which metaslab group we're
  * interested in. All vdevs may belong to two different metaslab classes.
  * Dedicated slog devices use only the primary metaslab group, rather than a
  * separate log group. For embedded slogs, the vdev_log_mg will be non-NULL.
  */
 metaslab_group_t *
 vdev_get_mg(vdev_t *vd, metaslab_class_t *mc)
 {
 	if (mc == spa_embedded_log_class(vd->vdev_spa) &&
 	    vd->vdev_log_mg != NULL)
 		return (vd->vdev_log_mg);
 	else
 		return (vd->vdev_mg);
 }
 
 void
 vdev_default_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
     range_seg64_t *physical_rs, range_seg64_t *remain_rs)
 {
 	(void) vd, (void) remain_rs;
 
 	physical_rs->rs_start = logical_rs->rs_start;
 	physical_rs->rs_end = logical_rs->rs_end;
 }
 
 /*
  * Derive the enumerated allocation bias from string input.
  * String origin is either the per-vdev zap or zpool(8).
  */
 static vdev_alloc_bias_t
 vdev_derive_alloc_bias(const char *bias)
 {
 	vdev_alloc_bias_t alloc_bias = VDEV_BIAS_NONE;
 
 	if (strcmp(bias, VDEV_ALLOC_BIAS_LOG) == 0)
 		alloc_bias = VDEV_BIAS_LOG;
 	else if (strcmp(bias, VDEV_ALLOC_BIAS_SPECIAL) == 0)
 		alloc_bias = VDEV_BIAS_SPECIAL;
 	else if (strcmp(bias, VDEV_ALLOC_BIAS_DEDUP) == 0)
 		alloc_bias = VDEV_BIAS_DEDUP;
 
 	return (alloc_bias);
 }
 
 /*
  * 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 txg)
 {
 	uint64_t asize = P2ROUNDUP(psize, 1ULL << vd->vdev_top->vdev_ashift);
 	uint64_t csize;
 
 	for (int c = 0; c < vd->vdev_children; c++) {
 		csize = vdev_psize_to_asize_txg(vd->vdev_child[c], psize, txg);
 		asize = MAX(asize, csize);
 	}
 
 	return (asize);
 }
 
 uint64_t
 vdev_default_min_asize(vdev_t *vd)
 {
 	return (vd->vdev_min_asize);
 }
 
 /*
  * Get the minimum allocatable size. We define the allocatable size as
  * the vdev's asize rounded to the nearest metaslab. This allows us to
  * replace or attach devices which don't have the same physical size but
  * can still satisfy the same number of allocations.
  */
 uint64_t
 vdev_get_min_asize(vdev_t *vd)
 {
 	vdev_t *pvd = vd->vdev_parent;
 
 	/*
 	 * If our parent is NULL (inactive spare or cache) or is the root,
 	 * just return our own asize.
 	 */
 	if (pvd == NULL)
 		return (vd->vdev_asize);
 
 	/*
 	 * The top-level vdev just returns the allocatable size rounded
 	 * to the nearest metaslab.
 	 */
 	if (vd == vd->vdev_top)
 		return (P2ALIGN_TYPED(vd->vdev_asize, 1ULL << vd->vdev_ms_shift,
 		    uint64_t));
 
 	return (pvd->vdev_ops->vdev_op_min_asize(pvd));
 }
 
 void
 vdev_set_min_asize(vdev_t *vd)
 {
 	vd->vdev_min_asize = vdev_get_min_asize(vd);
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_set_min_asize(vd->vdev_child[c]);
 }
 
 /*
  * Get the minimal allocation size for the top-level vdev.
  */
 uint64_t
 vdev_get_min_alloc(vdev_t *vd)
 {
 	uint64_t min_alloc = 1ULL << vd->vdev_ashift;
 
 	if (vd->vdev_ops->vdev_op_min_alloc != NULL)
 		min_alloc = vd->vdev_ops->vdev_op_min_alloc(vd);
 
 	return (min_alloc);
 }
 
 /*
  * Get the parity level for a top-level vdev.
  */
 uint64_t
 vdev_get_nparity(vdev_t *vd)
 {
 	uint64_t nparity = 0;
 
 	if (vd->vdev_ops->vdev_op_nparity != NULL)
 		nparity = vd->vdev_ops->vdev_op_nparity(vd);
 
 	return (nparity);
 }
 
 static int
 vdev_prop_get_int(vdev_t *vd, vdev_prop_t prop, uint64_t *value)
 {
 	spa_t *spa = vd->vdev_spa;
 	objset_t *mos = spa->spa_meta_objset;
 	uint64_t objid;
 	int err;
 
 	if (vd->vdev_root_zap != 0) {
 		objid = vd->vdev_root_zap;
 	} else if (vd->vdev_top_zap != 0) {
 		objid = vd->vdev_top_zap;
 	} else if (vd->vdev_leaf_zap != 0) {
 		objid = vd->vdev_leaf_zap;
 	} else {
 		return (EINVAL);
 	}
 
 	err = zap_lookup(mos, objid, vdev_prop_to_name(prop),
 	    sizeof (uint64_t), 1, value);
 
 	if (err == ENOENT)
 		*value = vdev_prop_default_numeric(prop);
 
 	return (err);
 }
 
 /*
  * Get the number of data disks for a top-level vdev.
  */
 uint64_t
 vdev_get_ndisks(vdev_t *vd)
 {
 	uint64_t ndisks = 1;
 
 	if (vd->vdev_ops->vdev_op_ndisks != NULL)
 		ndisks = vd->vdev_ops->vdev_op_ndisks(vd);
 
 	return (ndisks);
 }
 
 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)
 {
 	vdev_t *mvd;
 
 	if (vd->vdev_guid == guid)
 		return (vd);
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		if ((mvd = vdev_lookup_by_guid(vd->vdev_child[c], guid)) !=
 		    NULL)
 			return (mvd);
 
 	return (NULL);
 }
 
 static int
 vdev_count_leaves_impl(vdev_t *vd)
 {
 	int n = 0;
 
 	if (vd->vdev_ops->vdev_op_leaf)
 		return (1);
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		n += vdev_count_leaves_impl(vd->vdev_child[c]);
 
 	return (n);
 }
 
 int
 vdev_count_leaves(spa_t *spa)
 {
 	int rc;
 
 	spa_config_enter(spa, SCL_VDEV, FTAG, RW_READER);
 	rc = vdev_count_leaves_impl(spa->spa_root_vdev);
 	spa_config_exit(spa, SCL_VDEV, FTAG);
 
 	return (rc);
 }
 
 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_alloc(newsize, KM_SLEEP);
 	if (pvd->vdev_child != NULL) {
 		memcpy(newchild, pvd->vdev_child, 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) {
 		list_insert_head(&cvd->vdev_spa->spa_leaf_list, cvd);
 		cvd->vdev_spa->spa_leaf_list_gen++;
 	}
 }
 
 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;
 	}
 
 	if (cvd->vdev_ops->vdev_op_leaf) {
 		spa_t *spa = cvd->vdev_spa;
 		list_remove(&spa->spa_leaf_list, cvd);
 		spa->spa_leaf_list_gen++;
 	}
 
 	/*
 	 * Walk up all ancestors to update guid sum.
 	 */
 	for (; pvd != NULL; pvd = pvd->vdev_parent)
 		pvd->vdev_guid_sum -= cvd->vdev_guid_sum;
 }
 
 /*
  * 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;
 
 	ASSERT(spa_config_held(pvd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
 	if (oldc == 0)
 		return;
 
 	for (int c = newc = 0; c < oldc; c++)
 		if (pvd->vdev_child[c])
 			newc++;
 
 	if (newc > 0) {
 		newchild = kmem_zalloc(newc * sizeof (vdev_t *), KM_SLEEP);
 
 		for (int c = newc = 0; c < oldc; c++) {
 			if ((cvd = pvd->vdev_child[c]) != NULL) {
 				newchild[newc] = cvd;
 				cvd->vdev_id = newc++;
 			}
 		}
 	} else {
 		newchild = NULL;
 	}
 
 	kmem_free(pvd->vdev_child, oldc * sizeof (vdev_t *));
 	pvd->vdev_child = newchild;
 	pvd->vdev_children = newc;
 }
 
 /*
  * Allocate and minimally initialize a vdev_t.
  */
 vdev_t *
 vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
 {
 	vdev_t *vd;
 	vdev_indirect_config_t *vic;
 
 	vd = kmem_zalloc(sizeof (vdev_t), KM_SLEEP);
 	vic = &vd->vdev_indirect_config;
 
 	if (spa->spa_root_vdev == NULL) {
 		ASSERT(ops == &vdev_root_ops);
 		spa->spa_root_vdev = vd;
 		spa->spa_load_guid = spa_generate_guid(NULL);
 	}
 
 	if (guid == 0 && ops != &vdev_hole_ops) {
 		if (spa->spa_root_vdev == vd) {
 			/*
 			 * The root vdev's guid will also be the pool guid,
 			 * which must be unique among all pools.
 			 */
 			guid = spa_generate_guid(NULL);
 		} else {
 			/*
 			 * Any other vdev's guid must be unique within the pool.
 			 */
 			guid = spa_generate_guid(spa);
 		}
 		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;
 	vd->vdev_ishole = (ops == &vdev_hole_ops);
 	vic->vic_prev_indirect_vdev = UINT64_MAX;
 
 	rw_init(&vd->vdev_indirect_rwlock, NULL, RW_DEFAULT, NULL);
 	mutex_init(&vd->vdev_obsolete_lock, NULL, MUTEX_DEFAULT, NULL);
 	vd->vdev_obsolete_segments = range_tree_create(NULL, RANGE_SEG64, NULL,
 	    0, 0);
 
 	/*
 	 * Initialize rate limit structs for events.  We rate limit ZIO delay
 	 * and checksum events so that we don't overwhelm ZED with thousands
 	 * of events when a disk is acting up.
 	 */
 	zfs_ratelimit_init(&vd->vdev_delay_rl, &zfs_slow_io_events_per_second,
 	    1);
 	zfs_ratelimit_init(&vd->vdev_deadman_rl, &zfs_deadman_events_per_second,
 	    1);
 	zfs_ratelimit_init(&vd->vdev_checksum_rl,
 	    &zfs_checksum_events_per_second, 1);
 
 	/*
 	 * Default Thresholds for tuning ZED
 	 */
 	vd->vdev_checksum_n = vdev_prop_default_numeric(VDEV_PROP_CHECKSUM_N);
 	vd->vdev_checksum_t = vdev_prop_default_numeric(VDEV_PROP_CHECKSUM_T);
 	vd->vdev_io_n = vdev_prop_default_numeric(VDEV_PROP_IO_N);
 	vd->vdev_io_t = vdev_prop_default_numeric(VDEV_PROP_IO_T);
 	vd->vdev_slow_io_n = vdev_prop_default_numeric(VDEV_PROP_SLOW_IO_N);
 	vd->vdev_slow_io_t = vdev_prop_default_numeric(VDEV_PROP_SLOW_IO_T);
 
 	list_link_init(&vd->vdev_config_dirty_node);
 	list_link_init(&vd->vdev_state_dirty_node);
 	list_link_init(&vd->vdev_initialize_node);
 	list_link_init(&vd->vdev_leaf_node);
 	list_link_init(&vd->vdev_trim_node);
 
 	mutex_init(&vd->vdev_dtl_lock, NULL, MUTEX_NOLOCKDEP, NULL);
 	mutex_init(&vd->vdev_stat_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_probe_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_scan_io_queue_lock, NULL, MUTEX_DEFAULT, NULL);
 
 	mutex_init(&vd->vdev_initialize_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_initialize_io_lock, NULL, MUTEX_DEFAULT, NULL);
 	cv_init(&vd->vdev_initialize_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&vd->vdev_initialize_io_cv, NULL, CV_DEFAULT, NULL);
 
 	mutex_init(&vd->vdev_trim_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_autotrim_lock, NULL, MUTEX_DEFAULT, NULL);
 	mutex_init(&vd->vdev_trim_io_lock, NULL, MUTEX_DEFAULT, NULL);
 	cv_init(&vd->vdev_trim_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&vd->vdev_autotrim_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&vd->vdev_autotrim_kick_cv, NULL, CV_DEFAULT, NULL);
 	cv_init(&vd->vdev_trim_io_cv, NULL, CV_DEFAULT, NULL);
 
 	mutex_init(&vd->vdev_rebuild_lock, NULL, MUTEX_DEFAULT, NULL);
 	cv_init(&vd->vdev_rebuild_cv, NULL, CV_DEFAULT, NULL);
 
 	for (int t = 0; t < DTL_TYPES; t++) {
 		vd->vdev_dtl[t] = range_tree_create(NULL, RANGE_SEG64, NULL, 0,
 		    0);
 	}
 
 	txg_list_create(&vd->vdev_ms_list, spa,
 	    offsetof(struct metaslab, ms_txg_node));
 	txg_list_create(&vd->vdev_dtl_list, spa,
 	    offsetof(struct vdev, vdev_dtl_node));
 	vd->vdev_stat.vs_timestamp = gethrtime();
 	vdev_queue_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;
 	const char *type;
 	uint64_t guid = 0, islog;
 	vdev_t *vd;
 	vdev_indirect_config_t *vic;
 	const char *tmp = NULL;
 	int rc;
 	vdev_alloc_bias_t alloc_bias = VDEV_BIAS_NONE;
 	boolean_t top_level = (parent && !parent->vdev_parent);
 
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE, &type) != 0)
 		return (SET_ERROR(EINVAL));
 
 	if ((ops = vdev_getops(type)) == NULL)
 		return (SET_ERROR(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 (SET_ERROR(EINVAL));
 
 		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
 			return (SET_ERROR(EINVAL));
 	} else if (alloctype == VDEV_ALLOC_SPARE) {
 		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
 			return (SET_ERROR(EINVAL));
 	} else if (alloctype == VDEV_ALLOC_L2CACHE) {
 		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
 			return (SET_ERROR(EINVAL));
 	} else if (alloctype == VDEV_ALLOC_ROOTPOOL) {
 		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
 			return (SET_ERROR(EINVAL));
 	}
 
 	/*
 	 * The first allocated vdev must be of type 'root'.
 	 */
 	if (ops != &vdev_root_ops && spa->spa_root_vdev == NULL)
 		return (SET_ERROR(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 (SET_ERROR(ENOTSUP));
 
 	if (ops == &vdev_hole_ops && spa_version(spa) < SPA_VERSION_HOLES)
 		return (SET_ERROR(ENOTSUP));
 
 	if (top_level && alloctype == VDEV_ALLOC_ADD) {
 		const char *bias;
 
 		/*
 		 * If creating a top-level vdev, check for allocation
 		 * classes input.
 		 */
 		if (nvlist_lookup_string(nv, ZPOOL_CONFIG_ALLOCATION_BIAS,
 		    &bias) == 0) {
 			alloc_bias = vdev_derive_alloc_bias(bias);
 
 			/* spa_vdev_add() expects feature to be enabled */
 			if (spa->spa_load_state != SPA_LOAD_CREATE &&
 			    !spa_feature_is_enabled(spa,
 			    SPA_FEATURE_ALLOCATION_CLASSES)) {
 				return (SET_ERROR(ENOTSUP));
 			}
 		}
 
 		/* spa_vdev_add() expects feature to be enabled */
 		if (ops == &vdev_draid_ops &&
 		    spa->spa_load_state != SPA_LOAD_CREATE &&
 		    !spa_feature_is_enabled(spa, SPA_FEATURE_DRAID)) {
 			return (SET_ERROR(ENOTSUP));
 		}
 	}
 
 	/*
 	 * Initialize the vdev specific data.  This is done before calling
 	 * vdev_alloc_common() since it may fail and this simplifies the
 	 * error reporting and cleanup code paths.
 	 */
 	void *tsd = NULL;
 	if (ops->vdev_op_init != NULL) {
 		rc = ops->vdev_op_init(spa, nv, &tsd);
 		if (rc != 0) {
 			return (rc);
 		}
 	}
 
 	vd = vdev_alloc_common(spa, id, guid, ops);
 	vd->vdev_tsd = tsd;
 	vd->vdev_islog = islog;
 
 	if (top_level && alloc_bias != VDEV_BIAS_NONE)
 		vd->vdev_alloc_bias = alloc_bias;
 
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &tmp) == 0)
 		vd->vdev_path = spa_strdup(tmp);
 
 	/*
 	 * ZPOOL_CONFIG_AUX_STATE = "external" means we previously forced a
 	 * fault on a vdev and want it to persist across imports (like with
 	 * zpool offline -f).
 	 */
 	rc = nvlist_lookup_string(nv, ZPOOL_CONFIG_AUX_STATE, &tmp);
 	if (rc == 0 && tmp != NULL && strcmp(tmp, "external") == 0) {
 		vd->vdev_stat.vs_aux = VDEV_AUX_EXTERNAL;
 		vd->vdev_faulted = 1;
 		vd->vdev_label_aux = VDEV_AUX_EXTERNAL;
 	}
 
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_DEVID, &tmp) == 0)
 		vd->vdev_devid = spa_strdup(tmp);
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PHYS_PATH, &tmp) == 0)
 		vd->vdev_physpath = spa_strdup(tmp);
 
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH,
 	    &tmp) == 0)
 		vd->vdev_enc_sysfs_path = spa_strdup(tmp);
 
 	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_FRU, &tmp) == 0)
 		vd->vdev_fru = spa_strdup(tmp);
 
 	/*
 	 * 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;
 
 	vic = &vd->vdev_indirect_config;
 
 	ASSERT0(vic->vic_mapping_object);
 	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_INDIRECT_OBJECT,
 	    &vic->vic_mapping_object);
 	ASSERT0(vic->vic_births_object);
 	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_INDIRECT_BIRTHS,
 	    &vic->vic_births_object);
 	ASSERT3U(vic->vic_prev_indirect_vdev, ==, UINT64_MAX);
 	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_PREV_INDIRECT_VDEV,
 	    &vic->vic_prev_indirect_vdev);
 
 	/*
 	 * Look for the 'not present' flag.  This will only be set if the device
 	 * was not present at the time of import.
 	 */
 	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT,
 	    &vd->vdev_not_present);
 
 	/*
 	 * Get the alignment requirement. Ignore pool ashift for vdev
 	 * attach case.
 	 */
 	if (alloctype != VDEV_ALLOC_ATTACH) {
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT,
 		    &vd->vdev_ashift);
 	} else {
 		vd->vdev_attaching = B_TRUE;
 	}
 
 	/*
 	 * Retrieve the vdev creation time.
 	 */
 	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_CREATE_TXG,
 	    &vd->vdev_crtxg);
 
 	if (vd->vdev_ops == &vdev_root_ops &&
 	    (alloctype == VDEV_ALLOC_LOAD ||
 	    alloctype == VDEV_ALLOC_SPLIT ||
 	    alloctype == VDEV_ALLOC_ROOTPOOL)) {
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_VDEV_ROOT_ZAP,
 		    &vd->vdev_root_zap);
 	}
 
 	/*
 	 * If we're a top-level vdev, try to load the allocation parameters.
 	 */
 	if (top_level &&
 	    (alloctype == VDEV_ALLOC_LOAD || alloctype == VDEV_ALLOC_SPLIT)) {
 		(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);
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NONALLOCATING,
 		    &vd->vdev_noalloc);
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REMOVING,
 		    &vd->vdev_removing);
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_VDEV_TOP_ZAP,
 		    &vd->vdev_top_zap);
 		vd->vdev_rz_expanding = nvlist_exists(nv,
 		    ZPOOL_CONFIG_RAIDZ_EXPANDING);
 	} else {
 		ASSERT0(vd->vdev_top_zap);
 	}
 
 	if (top_level && alloctype != VDEV_ALLOC_ATTACH) {
 		ASSERT(alloctype == VDEV_ALLOC_LOAD ||
 		    alloctype == VDEV_ALLOC_ADD ||
 		    alloctype == VDEV_ALLOC_SPLIT ||
 		    alloctype == VDEV_ALLOC_ROOTPOOL);
 		/* Note: metaslab_group_create() is now deferred */
 	}
 
 	if (vd->vdev_ops->vdev_op_leaf &&
 	    (alloctype == VDEV_ALLOC_LOAD || alloctype == VDEV_ALLOC_SPLIT)) {
 		(void) nvlist_lookup_uint64(nv,
 		    ZPOOL_CONFIG_VDEV_LEAF_ZAP, &vd->vdev_leaf_zap);
 	} else {
 		ASSERT0(vd->vdev_leaf_zap);
 	}
 
 	/*
 	 * 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 ||
 	    alloctype == VDEV_ALLOC_ROOTPOOL)) {
 		if (alloctype == VDEV_ALLOC_LOAD) {
 			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DTL,
 			    &vd->vdev_dtl_object);
 			(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_UNSPARE,
 			    &vd->vdev_unspare);
 		}
 
 		if (alloctype == VDEV_ALLOC_ROOTPOOL) {
 			uint64_t spare = 0;
 
 			if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_IS_SPARE,
 			    &spare) == 0 && spare)
 				spa_spare_add(vd);
 		}
 
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_OFFLINE,
 		    &vd->vdev_offline);
 
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_RESILVER_TXG,
 		    &vd->vdev_resilver_txg);
 
 		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REBUILD_TXG,
 		    &vd->vdev_rebuild_txg);
 
 		if (nvlist_exists(nv, ZPOOL_CONFIG_RESILVER_DEFER))
 			vdev_defer_resilver(vd);
 
 		/*
 		 * In general, 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.  The only
 		 * exception is if we forced a vdev to a persistently faulted
 		 * state with 'zpool offline -f'.  The persistent fault will
 		 * remain across imports until cleared.
 		 *
 		 * Local vdevs will remain in the faulted state.
 		 */
 		if (spa_load_state(spa) == SPA_LOAD_OPEN ||
 		    spa_load_state(spa) == SPA_LOAD_IMPORT) {
 			(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);
 
 			if (vd->vdev_faulted || vd->vdev_degraded) {
 				const char *aux;
 
 				vd->vdev_label_aux =
 				    VDEV_AUX_ERR_EXCEEDED;
 				if (nvlist_lookup_string(nv,
 				    ZPOOL_CONFIG_AUX_STATE, &aux) == 0 &&
 				    strcmp(aux, "external") == 0)
 					vd->vdev_label_aux = VDEV_AUX_EXTERNAL;
 				else
 					vd->vdev_faulted = 0ULL;
 			}
 		}
 	}
 
 	/*
 	 * Add ourselves to the parent's list of children.
 	 */
 	vdev_add_child(parent, vd);
 
 	*vdp = vd;
 
 	return (0);
 }
 
 void
 vdev_free(vdev_t *vd)
 {
 	spa_t *spa = vd->vdev_spa;
 
 	ASSERT3P(vd->vdev_initialize_thread, ==, NULL);
 	ASSERT3P(vd->vdev_trim_thread, ==, NULL);
 	ASSERT3P(vd->vdev_autotrim_thread, ==, NULL);
 	ASSERT3P(vd->vdev_rebuild_thread, ==, NULL);
 
 	/*
 	 * Scan queues are normally destroyed at the end of a scan. If the
 	 * queue exists here, that implies the vdev is being removed while
 	 * the scan is still running.
 	 */
 	if (vd->vdev_scan_io_queue != NULL) {
 		mutex_enter(&vd->vdev_scan_io_queue_lock);
 		dsl_scan_io_queue_destroy(vd->vdev_scan_io_queue);
 		vd->vdev_scan_io_queue = NULL;
 		mutex_exit(&vd->vdev_scan_io_queue_lock);
 	}
 
 	/*
 	 * 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));
 	ASSERT(!list_link_active(&vd->vdev_state_dirty_node));
 
 	/*
 	 * Free all children.
 	 */
 	for (int 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);
 
 	if (vd->vdev_ops->vdev_op_fini != NULL)
 		vd->vdev_ops->vdev_op_fini(vd);
 
 	/*
 	 * Discard allocation state.
 	 */
 	if (vd->vdev_mg != NULL) {
 		vdev_metaslab_fini(vd);
 		metaslab_group_destroy(vd->vdev_mg);
 		vd->vdev_mg = NULL;
 	}
 	if (vd->vdev_log_mg != NULL) {
 		ASSERT0(vd->vdev_ms_count);
 		metaslab_group_destroy(vd->vdev_log_mg);
 		vd->vdev_log_mg = NULL;
 	}
 
 	ASSERT0(vd->vdev_stat.vs_space);
 	ASSERT0(vd->vdev_stat.vs_dspace);
 	ASSERT0(vd->vdev_stat.vs_alloc);
 
 	/*
 	 * Remove this vdev from its parent's child list.
 	 */
 	vdev_remove_child(vd->vdev_parent, vd);
 
 	ASSERT(vd->vdev_parent == NULL);
 	ASSERT(!list_link_active(&vd->vdev_leaf_node));
 
 	/*
 	 * Clean up vdev structure.
 	 */
 	vdev_queue_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_enc_sysfs_path)
 		spa_strfree(vd->vdev_enc_sysfs_path);
 
 	if (vd->vdev_fru)
 		spa_strfree(vd->vdev_fru);
 
 	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_close(vd->vdev_dtl_sm);
 	for (int t = 0; t < DTL_TYPES; t++) {
 		range_tree_vacate(vd->vdev_dtl[t], NULL, NULL);
 		range_tree_destroy(vd->vdev_dtl[t]);
 	}
 	mutex_exit(&vd->vdev_dtl_lock);
 
 	EQUIV(vd->vdev_indirect_births != NULL,
 	    vd->vdev_indirect_mapping != NULL);
 	if (vd->vdev_indirect_births != NULL) {
 		vdev_indirect_mapping_close(vd->vdev_indirect_mapping);
 		vdev_indirect_births_close(vd->vdev_indirect_births);
 	}
 
 	if (vd->vdev_obsolete_sm != NULL) {
 		ASSERT(vd->vdev_removing ||
 		    vd->vdev_ops == &vdev_indirect_ops);
 		space_map_close(vd->vdev_obsolete_sm);
 		vd->vdev_obsolete_sm = NULL;
 	}
 	range_tree_destroy(vd->vdev_obsolete_segments);
 	rw_destroy(&vd->vdev_indirect_rwlock);
 	mutex_destroy(&vd->vdev_obsolete_lock);
 
 	mutex_destroy(&vd->vdev_dtl_lock);
 	mutex_destroy(&vd->vdev_stat_lock);
 	mutex_destroy(&vd->vdev_probe_lock);
 	mutex_destroy(&vd->vdev_scan_io_queue_lock);
 
 	mutex_destroy(&vd->vdev_initialize_lock);
 	mutex_destroy(&vd->vdev_initialize_io_lock);
 	cv_destroy(&vd->vdev_initialize_io_cv);
 	cv_destroy(&vd->vdev_initialize_cv);
 
 	mutex_destroy(&vd->vdev_trim_lock);
 	mutex_destroy(&vd->vdev_autotrim_lock);
 	mutex_destroy(&vd->vdev_trim_io_lock);
 	cv_destroy(&vd->vdev_trim_cv);
 	cv_destroy(&vd->vdev_autotrim_cv);
 	cv_destroy(&vd->vdev_autotrim_kick_cv);
 	cv_destroy(&vd->vdev_trim_io_cv);
 
 	mutex_destroy(&vd->vdev_rebuild_lock);
 	cv_destroy(&vd->vdev_rebuild_cv);
 
 	zfs_ratelimit_fini(&vd->vdev_delay_rl);
 	zfs_ratelimit_fini(&vd->vdev_deadman_rl);
 	zfs_ratelimit_fini(&vd->vdev_checksum_rl);
 
 	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;
 	tvd->vdev_top_zap = svd->vdev_top_zap;
 
 	svd->vdev_ms_array = 0;
 	svd->vdev_ms_shift = 0;
 	svd->vdev_ms_count = 0;
 	svd->vdev_top_zap = 0;
 
 	if (tvd->vdev_mg)
 		ASSERT3P(tvd->vdev_mg, ==, svd->vdev_mg);
 	if (tvd->vdev_log_mg)
 		ASSERT3P(tvd->vdev_log_mg, ==, svd->vdev_log_mg);
 	tvd->vdev_mg = svd->vdev_mg;
 	tvd->vdev_log_mg = svd->vdev_log_mg;
 	tvd->vdev_ms = svd->vdev_ms;
 
 	svd->vdev_mg = NULL;
 	svd->vdev_log_mg = NULL;
 	svd->vdev_ms = NULL;
 
 	if (tvd->vdev_mg != NULL)
 		tvd->vdev_mg->mg_vd = tvd;
 	if (tvd->vdev_log_mg != NULL)
 		tvd->vdev_log_mg->mg_vd = tvd;
 
 	tvd->vdev_checkpoint_sm = svd->vdev_checkpoint_sm;
 	svd->vdev_checkpoint_sm = NULL;
 
 	tvd->vdev_alloc_bias = svd->vdev_alloc_bias;
 	svd->vdev_alloc_bias = VDEV_BIAS_NONE;
 
 	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;
 
 	/*
 	 * State which may be set on a top-level vdev that's in the
 	 * process of being removed.
 	 */
 	ASSERT0(tvd->vdev_indirect_config.vic_births_object);
 	ASSERT0(tvd->vdev_indirect_config.vic_mapping_object);
 	ASSERT3U(tvd->vdev_indirect_config.vic_prev_indirect_vdev, ==, -1ULL);
 	ASSERT3P(tvd->vdev_indirect_mapping, ==, NULL);
 	ASSERT3P(tvd->vdev_indirect_births, ==, NULL);
 	ASSERT3P(tvd->vdev_obsolete_sm, ==, NULL);
 	ASSERT0(tvd->vdev_noalloc);
 	ASSERT0(tvd->vdev_removing);
 	ASSERT0(tvd->vdev_rebuilding);
 	tvd->vdev_noalloc = svd->vdev_noalloc;
 	tvd->vdev_removing = svd->vdev_removing;
 	tvd->vdev_rebuilding = svd->vdev_rebuilding;
 	tvd->vdev_rebuild_config = svd->vdev_rebuild_config;
 	tvd->vdev_indirect_config = svd->vdev_indirect_config;
 	tvd->vdev_indirect_mapping = svd->vdev_indirect_mapping;
 	tvd->vdev_indirect_births = svd->vdev_indirect_births;
 	range_tree_swap(&svd->vdev_obsolete_segments,
 	    &tvd->vdev_obsolete_segments);
 	tvd->vdev_obsolete_sm = svd->vdev_obsolete_sm;
 	svd->vdev_indirect_config.vic_mapping_object = 0;
 	svd->vdev_indirect_config.vic_births_object = 0;
 	svd->vdev_indirect_config.vic_prev_indirect_vdev = -1ULL;
 	svd->vdev_indirect_mapping = NULL;
 	svd->vdev_indirect_births = NULL;
 	svd->vdev_obsolete_sm = NULL;
 	svd->vdev_noalloc = 0;
 	svd->vdev_removing = 0;
 	svd->vdev_rebuilding = 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;
 
 	dsl_scan_io_queue_vdev_xfer(svd, tvd);
 }
 
 static void
 vdev_top_update(vdev_t *tvd, vdev_t *vd)
 {
 	if (vd == NULL)
 		return;
 
 	vd->vdev_top = tvd;
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_top_update(tvd, vd->vdev_child[c]);
 }
 
 /*
  * Add a mirror/replacing vdev above an existing vdev.  There is no need to
  * call .vdev_op_init() since mirror/replacing vdevs do not have private state.
  */
 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_min_asize = cvd->vdev_min_asize;
 	mvd->vdev_max_asize = cvd->vdev_max_asize;
 	mvd->vdev_psize = cvd->vdev_psize;
 	mvd->vdev_ashift = cvd->vdev_ashift;
 	mvd->vdev_logical_ashift = cvd->vdev_logical_ashift;
 	mvd->vdev_physical_ashift = cvd->vdev_physical_ashift;
 	mvd->vdev_state = cvd->vdev_state;
 	mvd->vdev_crtxg = cvd->vdev_crtxg;
 
 	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;
 	cvd->vdev_logical_ashift = mvd->vdev_logical_ashift;
 	cvd->vdev_physical_ashift = mvd->vdev_physical_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) {
 		uint64_t guid_delta = mvd->vdev_guid - cvd->vdev_guid;
 		cvd->vdev_orig_guid = cvd->vdev_guid;
 		cvd->vdev_guid += guid_delta;
 		cvd->vdev_guid_sum += guid_delta;
 
 		/*
 		 * If pool not set for autoexpand, we need to also preserve
 		 * mvd's asize to prevent automatic expansion of cvd.
 		 * Otherwise if we are adjusting the mirror by attaching and
 		 * detaching children of non-uniform sizes, the mirror could
 		 * autoexpand, unexpectedly requiring larger devices to
 		 * re-establish the mirror.
 		 */
 		if (!cvd->vdev_spa->spa_autoexpand)
 			cvd->vdev_asize = mvd->vdev_asize;
 	}
 	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);
 }
 
 /*
  * Choose GCD for spa_gcd_alloc.
  */
 static uint64_t
 vdev_gcd(uint64_t a, uint64_t b)
 {
 	while (b != 0) {
 		uint64_t t = b;
 		b = a % b;
 		a = t;
 	}
 	return (a);
 }
 
 /*
  * Set spa_min_alloc and spa_gcd_alloc.
  */
 static void
 vdev_spa_set_alloc(spa_t *spa, uint64_t min_alloc)
 {
 	if (min_alloc < spa->spa_min_alloc)
 		spa->spa_min_alloc = min_alloc;
 	if (spa->spa_gcd_alloc == INT_MAX) {
 		spa->spa_gcd_alloc = min_alloc;
 	} else {
 		spa->spa_gcd_alloc = vdev_gcd(min_alloc,
 		    spa->spa_gcd_alloc);
 	}
 }
 
 void
 vdev_metaslab_group_create(vdev_t *vd)
 {
 	spa_t *spa = vd->vdev_spa;
 
 	/*
 	 * metaslab_group_create was delayed until allocation bias was available
 	 */
 	if (vd->vdev_mg == NULL) {
 		metaslab_class_t *mc;
 
 		if (vd->vdev_islog && vd->vdev_alloc_bias == VDEV_BIAS_NONE)
 			vd->vdev_alloc_bias = VDEV_BIAS_LOG;
 
 		ASSERT3U(vd->vdev_islog, ==,
 		    (vd->vdev_alloc_bias == VDEV_BIAS_LOG));
 
 		switch (vd->vdev_alloc_bias) {
 		case VDEV_BIAS_LOG:
 			mc = spa_log_class(spa);
 			break;
 		case VDEV_BIAS_SPECIAL:
 			mc = spa_special_class(spa);
 			break;
 		case VDEV_BIAS_DEDUP:
 			mc = spa_dedup_class(spa);
 			break;
 		default:
 			mc = spa_normal_class(spa);
 		}
 
 		vd->vdev_mg = metaslab_group_create(mc, vd,
 		    spa->spa_alloc_count);
 
 		if (!vd->vdev_islog) {
 			vd->vdev_log_mg = metaslab_group_create(
 			    spa_embedded_log_class(spa), vd, 1);
 		}
 
 		/*
 		 * The spa ashift min/max only apply for the normal metaslab
 		 * class. Class destination is late binding so ashift boundary
 		 * setting had to wait until now.
 		 */
 		if (vd->vdev_top == vd && vd->vdev_ashift != 0 &&
 		    mc == spa_normal_class(spa) && vd->vdev_aux == NULL) {
 			if (vd->vdev_ashift > spa->spa_max_ashift)
 				spa->spa_max_ashift = vd->vdev_ashift;
 			if (vd->vdev_ashift < spa->spa_min_ashift)
 				spa->spa_min_ashift = vd->vdev_ashift;
 
 			uint64_t min_alloc = vdev_get_min_alloc(vd);
 			vdev_spa_set_alloc(spa, min_alloc);
 		}
 	}
 }
 
 int
 vdev_metaslab_init(vdev_t *vd, uint64_t txg)
 {
 	spa_t *spa = vd->vdev_spa;
 	uint64_t oldc = vd->vdev_ms_count;
 	uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
 	metaslab_t **mspp;
 	int error;
 	boolean_t expanding = (oldc != 0);
 
 	ASSERT(txg == 0 || spa_config_held(spa, SCL_ALLOC, RW_WRITER));
 
 	/*
 	 * This vdev is not being allocated from yet or is a hole.
 	 */
 	if (vd->vdev_ms_shift == 0)
 		return (0);
 
 	ASSERT(!vd->vdev_ishole);
 
 	ASSERT(oldc <= newc);
 
 	mspp = vmem_zalloc(newc * sizeof (*mspp), KM_SLEEP);
 
 	if (expanding) {
 		memcpy(mspp, vd->vdev_ms, oldc * sizeof (*mspp));
 		vmem_free(vd->vdev_ms, oldc * sizeof (*mspp));
 	}
 
 	vd->vdev_ms = mspp;
 	vd->vdev_ms_count = newc;
 
 	for (uint64_t m = oldc; m < newc; m++) {
 		uint64_t object = 0;
 		/*
 		 * vdev_ms_array may be 0 if we are creating the "fake"
 		 * metaslabs for an indirect vdev for zdb's leak detection.
 		 * See zdb_leak_init().
 		 */
 		if (txg == 0 && vd->vdev_ms_array != 0) {
 			error = dmu_read(spa->spa_meta_objset,
 			    vd->vdev_ms_array,
 			    m * sizeof (uint64_t), sizeof (uint64_t), &object,
 			    DMU_READ_PREFETCH);
 			if (error != 0) {
 				vdev_dbgmsg(vd, "unable to read the metaslab "
 				    "array [error=%d]", error);
 				return (error);
 			}
 		}
 
 		error = metaslab_init(vd->vdev_mg, m, object, txg,
 		    &(vd->vdev_ms[m]));
 		if (error != 0) {
 			vdev_dbgmsg(vd, "metaslab_init failed [error=%d]",
 			    error);
 			return (error);
 		}
 	}
 
 	/*
 	 * Find the emptiest metaslab on the vdev and mark it for use for
 	 * embedded slog by moving it from the regular to the log metaslab
 	 * group.
 	 */
 	if (vd->vdev_mg->mg_class == spa_normal_class(spa) &&
 	    vd->vdev_ms_count > zfs_embedded_slog_min_ms &&
 	    avl_is_empty(&vd->vdev_log_mg->mg_metaslab_tree)) {
 		uint64_t slog_msid = 0;
 		uint64_t smallest = UINT64_MAX;
 
 		/*
 		 * Note, we only search the new metaslabs, because the old
 		 * (pre-existing) ones may be active (e.g. have non-empty
 		 * range_tree's), and we don't move them to the new
 		 * metaslab_t.
 		 */
 		for (uint64_t m = oldc; m < newc; m++) {
 			uint64_t alloc =
 			    space_map_allocated(vd->vdev_ms[m]->ms_sm);
 			if (alloc < smallest) {
 				slog_msid = m;
 				smallest = alloc;
 			}
 		}
 		metaslab_t *slog_ms = vd->vdev_ms[slog_msid];
 		/*
 		 * The metaslab was marked as dirty at the end of
 		 * metaslab_init(). Remove it from the dirty list so that we
 		 * can uninitialize and reinitialize it to the new class.
 		 */
 		if (txg != 0) {
 			(void) txg_list_remove_this(&vd->vdev_ms_list,
 			    slog_ms, txg);
 		}
 		uint64_t sm_obj = space_map_object(slog_ms->ms_sm);
 		metaslab_fini(slog_ms);
 		VERIFY0(metaslab_init(vd->vdev_log_mg, slog_msid, sm_obj, txg,
 		    &vd->vdev_ms[slog_msid]));
 	}
 
 	if (txg == 0)
 		spa_config_enter(spa, SCL_ALLOC, FTAG, RW_WRITER);
 
 	/*
 	 * If the vdev is marked as non-allocating then don't
 	 * activate the metaslabs since we want to ensure that
 	 * no allocations are performed on this device.
 	 */
 	if (vd->vdev_noalloc) {
 		/* track non-allocating vdev space */
 		spa->spa_nonallocating_dspace += spa_deflate(spa) ?
 		    vd->vdev_stat.vs_dspace : vd->vdev_stat.vs_space;
 	} else if (!expanding) {
 		metaslab_group_activate(vd->vdev_mg);
 		if (vd->vdev_log_mg != NULL)
 			metaslab_group_activate(vd->vdev_log_mg);
 	}
 
 	if (txg == 0)
 		spa_config_exit(spa, SCL_ALLOC, FTAG);
 
 	return (0);
 }
 
 void
 vdev_metaslab_fini(vdev_t *vd)
 {
 	if (vd->vdev_checkpoint_sm != NULL) {
 		ASSERT(spa_feature_is_active(vd->vdev_spa,
 		    SPA_FEATURE_POOL_CHECKPOINT));
 		space_map_close(vd->vdev_checkpoint_sm);
 		/*
 		 * Even though we close the space map, we need to set its
 		 * pointer to NULL. The reason is that vdev_metaslab_fini()
 		 * may be called multiple times for certain operations
 		 * (i.e. when destroying a pool) so we need to ensure that
 		 * this clause never executes twice. This logic is similar
 		 * to the one used for the vdev_ms clause below.
 		 */
 		vd->vdev_checkpoint_sm = NULL;
 	}
 
 	if (vd->vdev_ms != NULL) {
 		metaslab_group_t *mg = vd->vdev_mg;
 
 		metaslab_group_passivate(mg);
 		if (vd->vdev_log_mg != NULL) {
 			ASSERT(!vd->vdev_islog);
 			metaslab_group_passivate(vd->vdev_log_mg);
 		}
 
 		uint64_t count = vd->vdev_ms_count;
 		for (uint64_t m = 0; m < count; m++) {
 			metaslab_t *msp = vd->vdev_ms[m];
 			if (msp != NULL)
 				metaslab_fini(msp);
 		}
 		vmem_free(vd->vdev_ms, count * sizeof (metaslab_t *));
 		vd->vdev_ms = NULL;
 		vd->vdev_ms_count = 0;
 
 		for (int i = 0; i < RANGE_TREE_HISTOGRAM_SIZE; i++) {
 			ASSERT0(mg->mg_histogram[i]);
 			if (vd->vdev_log_mg != NULL)
 				ASSERT0(vd->vdev_log_mg->mg_histogram[i]);
 		}
 	}
 	ASSERT0(vd->vdev_ms_count);
 }
 
 typedef struct vdev_probe_stats {
 	boolean_t	vps_readable;
 	boolean_t	vps_writeable;
 	boolean_t	vps_zio_done_probe;
 	int		vps_flags;
 } vdev_probe_stats_t;
 
 static void
 vdev_probe_done(zio_t *zio)
 {
 	spa_t *spa = zio->io_spa;
 	vdev_t *vd = zio->io_vd;
 	vdev_probe_stats_t *vps = zio->io_private;
 
 	ASSERT(vd->vdev_probe_zio != NULL);
 
 	if (zio->io_type == ZIO_TYPE_READ) {
 		if (zio->io_error == 0)
 			vps->vps_readable = 1;
 		if (zio->io_error == 0 && spa_writeable(spa)) {
 			zio_nowait(zio_write_phys(vd->vdev_probe_zio, vd,
 			    zio->io_offset, zio->io_size, zio->io_abd,
 			    ZIO_CHECKSUM_OFF, vdev_probe_done, vps,
 			    ZIO_PRIORITY_SYNC_WRITE, vps->vps_flags, B_TRUE));
 		} else {
 			abd_free(zio->io_abd);
 		}
 	} else if (zio->io_type == ZIO_TYPE_WRITE) {
 		if (zio->io_error == 0)
 			vps->vps_writeable = 1;
 		abd_free(zio->io_abd);
 	} else if (zio->io_type == ZIO_TYPE_NULL) {
 		zio_t *pio;
 		zio_link_t *zl;
 
 		vd->vdev_cant_read |= !vps->vps_readable;
 		vd->vdev_cant_write |= !vps->vps_writeable;
 		vdev_dbgmsg(vd, "probe done, cant_read=%u cant_write=%u",
 		    vd->vdev_cant_read, vd->vdev_cant_write);
 
 		if (vdev_readable(vd) &&
 		    (vdev_writeable(vd) || !spa_writeable(spa))) {
 			zio->io_error = 0;
 		} else {
 			ASSERT(zio->io_error != 0);
 			vdev_dbgmsg(vd, "failed probe");
 			(void) zfs_ereport_post(FM_EREPORT_ZFS_PROBE_FAILURE,
 			    spa, vd, NULL, NULL, 0);
 			zio->io_error = SET_ERROR(ENXIO);
 
 			/*
 			 * If this probe was initiated from zio pipeline, then
 			 * change the state in a spa_async_request. Probes that
 			 * were initiated from a vdev_open can change the state
 			 * as part of the open call.
 			 */
 			if (vps->vps_zio_done_probe) {
 				vd->vdev_fault_wanted = B_TRUE;
 				spa_async_request(spa, SPA_ASYNC_FAULT_VDEV);
 			}
 		}
 
 		mutex_enter(&vd->vdev_probe_lock);
 		ASSERT(vd->vdev_probe_zio == zio);
 		vd->vdev_probe_zio = NULL;
 		mutex_exit(&vd->vdev_probe_lock);
 
 		zl = NULL;
 		while ((pio = zio_walk_parents(zio, &zl)) != NULL)
 			if (!vdev_accessible(vd, pio))
 				pio->io_error = SET_ERROR(ENXIO);
 
 		kmem_free(vps, sizeof (*vps));
 	}
 }
 
 /*
  * Determine whether this device is accessible.
  *
  * Read and write 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 *zio)
 {
 	spa_t *spa = vd->vdev_spa;
 	vdev_probe_stats_t *vps = NULL;
 	zio_t *pio;
 
 	ASSERT(vd->vdev_ops->vdev_op_leaf);
 
 	/*
 	 * Don't probe the probe.
 	 */
 	if (zio && (zio->io_flags & ZIO_FLAG_PROBE))
 		return (NULL);
 
 	/*
 	 * To prevent 'probe storms' when a device fails, we create
 	 * just one probe i/o at a time.  All zios that want to probe
 	 * this vdev will become parents of the probe io.
 	 */
 	mutex_enter(&vd->vdev_probe_lock);
 
 	if ((pio = vd->vdev_probe_zio) == NULL) {
 		vps = kmem_zalloc(sizeof (*vps), KM_SLEEP);
 
 		vps->vps_flags = ZIO_FLAG_CANFAIL | ZIO_FLAG_PROBE |
 		    ZIO_FLAG_DONT_AGGREGATE | ZIO_FLAG_TRYHARD;
 		vps->vps_zio_done_probe = (zio != NULL);
 
 		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;
 		}
 
 		vd->vdev_probe_zio = pio = zio_null(NULL, spa, vd,
 		    vdev_probe_done, vps,
 		    vps->vps_flags | ZIO_FLAG_DONT_PROPAGATE);
 	}
 
 	if (zio != NULL)
 		zio_add_child(zio, pio);
 
 	mutex_exit(&vd->vdev_probe_lock);
 
 	if (vps == NULL) {
 		ASSERT(zio != NULL);
 		return (NULL);
 	}
 
 	for (int l = 1; l < VDEV_LABELS; l++) {
 		zio_nowait(zio_read_phys(pio, vd,
 		    vdev_label_offset(vd->vdev_psize, l,
 		    offsetof(vdev_label_t, vl_be)), VDEV_PAD_SIZE,
 		    abd_alloc_for_io(VDEV_PAD_SIZE, B_TRUE),
 		    ZIO_CHECKSUM_OFF, vdev_probe_done, vps,
 		    ZIO_PRIORITY_SYNC_READ, vps->vps_flags, B_TRUE));
 	}
 
 	if (zio == NULL)
 		return (pio);
 
 	zio_nowait(pio);
 	return (NULL);
 }
 
 static void
 vdev_load_child(void *arg)
 {
 	vdev_t *vd = arg;
 
 	vd->vdev_load_error = vdev_load(vd);
 }
 
 static void
 vdev_open_child(void *arg)
 {
 	vdev_t *vd = arg;
 
 	vd->vdev_open_thread = curthread;
 	vd->vdev_open_error = vdev_open(vd);
 	vd->vdev_open_thread = NULL;
 }
 
 static boolean_t
 vdev_uses_zvols(vdev_t *vd)
 {
 #ifdef _KERNEL
 	if (zvol_is_zvol(vd->vdev_path))
 		return (B_TRUE);
 #endif
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		if (vdev_uses_zvols(vd->vdev_child[c]))
 			return (B_TRUE);
 
 	return (B_FALSE);
 }
 
 /*
  * Returns B_TRUE if the passed child should be opened.
  */
 static boolean_t
 vdev_default_open_children_func(vdev_t *vd)
 {
 	(void) vd;
 	return (B_TRUE);
 }
 
 /*
  * Open the requested child vdevs.  If any of the leaf vdevs are using
  * a ZFS volume then do the opens in a single thread.  This avoids a
  * deadlock when the current thread is holding the spa_namespace_lock.
  */
 static void
 vdev_open_children_impl(vdev_t *vd, vdev_open_children_func_t *open_func)
 {
 	int children = vd->vdev_children;
 
 	taskq_t *tq = taskq_create("vdev_open", children, minclsyspri,
 	    children, children, TASKQ_PREPOPULATE);
 	vd->vdev_nonrot = B_TRUE;
 
 	for (int c = 0; c < children; c++) {
 		vdev_t *cvd = vd->vdev_child[c];
 
 		if (open_func(cvd) == B_FALSE)
 			continue;
 
 		if (tq == NULL || vdev_uses_zvols(vd)) {
 			cvd->vdev_open_error = vdev_open(cvd);
 		} else {
 			VERIFY(taskq_dispatch(tq, vdev_open_child,
 			    cvd, TQ_SLEEP) != TASKQID_INVALID);
 		}
 
 		vd->vdev_nonrot &= cvd->vdev_nonrot;
 	}
 
 	if (tq != NULL) {
 		taskq_wait(tq);
 		taskq_destroy(tq);
 	}
 }
 
 /*
  * Open all child vdevs.
  */
 void
 vdev_open_children(vdev_t *vd)
 {
 	vdev_open_children_impl(vd, vdev_default_open_children_func);
 }
 
 /*
  * Conditionally open a subset of child vdevs.
  */
 void
 vdev_open_children_subset(vdev_t *vd, vdev_open_children_func_t *open_func)
 {
 	vdev_open_children_impl(vd, open_func);
 }
 
 /*
  * Compute the raidz-deflation ratio.  Note, we hard-code 128k (1 << 17)
  * because it is the "typical" blocksize.  Even though SPA_MAXBLOCKSIZE
  * changed, this algorithm can not change, otherwise it would inconsistently
  * account for existing bp's.  We also hard-code txg 0 for the same reason
  * since expanded RAIDZ vdevs can use a different asize for different birth
  * txg's.
  */
 static void
 vdev_set_deflate_ratio(vdev_t *vd)
 {
 	if (vd == vd->vdev_top && !vd->vdev_ishole && vd->vdev_ashift != 0) {
 		vd->vdev_deflate_ratio = (1 << 17) /
 		    (vdev_psize_to_asize_txg(vd, 1 << 17, 0) >>
 		    SPA_MINBLOCKSHIFT);
 	}
 }
 
 /*
  * Choose the best of two ashifts, preferring one between logical ashift
  * (absolute minimum) and administrator defined maximum, otherwise take
  * the biggest of the two.
  */
 uint64_t
 vdev_best_ashift(uint64_t logical, uint64_t a, uint64_t b)
 {
 	if (a > logical && a <= zfs_vdev_max_auto_ashift) {
 		if (b <= logical || b > zfs_vdev_max_auto_ashift)
 			return (a);
 		else
 			return (MAX(a, b));
 	} else if (b <= logical || b > zfs_vdev_max_auto_ashift)
 		return (MAX(a, b));
 	return (b);
 }
 
 /*
  * Maximize performance by inflating the configured ashift for top level
  * vdevs to be as close to the physical ashift as possible while maintaining
  * administrator defined limits and ensuring it doesn't go below the
  * logical ashift.
  */
 static void
 vdev_ashift_optimize(vdev_t *vd)
 {
 	ASSERT(vd == vd->vdev_top);
 
 	if (vd->vdev_ashift < vd->vdev_physical_ashift &&
 	    vd->vdev_physical_ashift <= zfs_vdev_max_auto_ashift) {
 		vd->vdev_ashift = MIN(
 		    MAX(zfs_vdev_max_auto_ashift, vd->vdev_ashift),
 		    MAX(zfs_vdev_min_auto_ashift,
 		    vd->vdev_physical_ashift));
 	} else {
 		/*
 		 * If the logical and physical ashifts are the same, then
 		 * we ensure that the top-level vdev's ashift is not smaller
 		 * than our minimum ashift value. For the unusual case
 		 * where logical ashift > physical ashift, we can't cap
 		 * the calculated ashift based on max ashift as that
 		 * would cause failures.
 		 * We still check if we need to increase it to match
 		 * the min ashift.
 		 */
 		vd->vdev_ashift = MAX(zfs_vdev_min_auto_ashift,
 		    vd->vdev_ashift);
 	}
 }
 
 /*
  * Prepare a virtual device for access.
  */
 int
 vdev_open(vdev_t *vd)
 {
 	spa_t *spa = vd->vdev_spa;
 	int error;
 	uint64_t osize = 0;
 	uint64_t max_osize = 0;
 	uint64_t asize, max_asize, psize;
 	uint64_t logical_ashift = 0;
 	uint64_t physical_ashift = 0;
 
 	ASSERT(vd->vdev_open_thread == curthread ||
 	    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);
 
 	vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
 	vd->vdev_cant_read = B_FALSE;
 	vd->vdev_cant_write = B_FALSE;
+	vd->vdev_fault_wanted = B_FALSE;
 	vd->vdev_min_asize = vdev_get_min_asize(vd);
 
 	/*
 	 * If this vdev is not removed, check its fault status.  If it's
 	 * faulted, bail out of the open.
 	 */
 	if (!vd->vdev_removed && vd->vdev_faulted) {
 		ASSERT(vd->vdev_children == 0);
 		ASSERT(vd->vdev_label_aux == VDEV_AUX_ERR_EXCEEDED ||
 		    vd->vdev_label_aux == VDEV_AUX_EXTERNAL);
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_FAULTED,
 		    vd->vdev_label_aux);
 		return (SET_ERROR(ENXIO));
 	} else if (vd->vdev_offline) {
 		ASSERT(vd->vdev_children == 0);
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE, VDEV_AUX_NONE);
 		return (SET_ERROR(ENXIO));
 	}
 
 	error = vd->vdev_ops->vdev_op_open(vd, &osize, &max_osize,
 	    &logical_ashift, &physical_ashift);
 
 	/* Keep the device in removed state if unplugged */
 	if (error == ENOENT && vd->vdev_removed) {
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_REMOVED,
 		    VDEV_AUX_NONE);
 		return (error);
 	}
 
 	/*
 	 * Physical volume size should never be larger than its max size, unless
 	 * the disk has shrunk while we were reading it or the device is buggy
 	 * or damaged: either way it's not safe for use, bail out of the open.
 	 */
 	if (osize > max_osize) {
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_OPEN_FAILED);
 		return (SET_ERROR(ENXIO));
 	}
 
 	/*
 	 * Reset the vdev_reopening flag so that we actually close
 	 * the vdev on error.
 	 */
 	vd->vdev_reopening = B_FALSE;
 	if (zio_injection_enabled && error == 0)
 		error = zio_handle_device_injection(vd, NULL, SET_ERROR(ENXIO));
 
 	if (error) {
 		if (vd->vdev_removed &&
 		    vd->vdev_stat.vs_aux != VDEV_AUX_OPEN_FAILED)
 			vd->vdev_removed = B_FALSE;
 
 		if (vd->vdev_stat.vs_aux == VDEV_AUX_CHILDREN_OFFLINE) {
 			vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE,
 			    vd->vdev_stat.vs_aux);
 		} else {
 			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
 			    vd->vdev_stat.vs_aux);
 		}
 		return (error);
 	}
 
 	vd->vdev_removed = B_FALSE;
 
 	/*
 	 * Recheck the faulted flag now that we have confirmed that
 	 * the vdev is accessible.  If we're faulted, bail.
 	 */
 	if (vd->vdev_faulted) {
 		ASSERT(vd->vdev_children == 0);
 		ASSERT(vd->vdev_label_aux == VDEV_AUX_ERR_EXCEEDED ||
 		    vd->vdev_label_aux == VDEV_AUX_EXTERNAL);
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_FAULTED,
 		    vd->vdev_label_aux);
 		return (SET_ERROR(ENXIO));
 	}
 
 	if (vd->vdev_degraded) {
 		ASSERT(vd->vdev_children == 0);
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_DEGRADED,
 		    VDEV_AUX_ERR_EXCEEDED);
 	} else {
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_HEALTHY, 0);
 	}
 
 	/*
 	 * For hole or missing vdevs we just return success.
 	 */
 	if (vd->vdev_ishole || vd->vdev_ops == &vdev_missing_ops)
 		return (0);
 
 	for (int 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_TYPED(osize, sizeof (vdev_label_t), uint64_t);
 	max_osize = P2ALIGN_TYPED(max_osize, sizeof (vdev_label_t), uint64_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 (SET_ERROR(EOVERFLOW));
 		}
 		psize = osize;
 		asize = osize - (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE);
 		max_asize = max_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 (SET_ERROR(EOVERFLOW));
 		}
 		psize = 0;
 		asize = osize;
 		max_asize = max_osize;
 	}
 
 	/*
 	 * If the vdev was expanded, record this so that we can re-create the
 	 * uberblock rings in labels {2,3}, during the next sync.
 	 */
 	if ((psize > vd->vdev_psize) && (vd->vdev_psize != 0))
 		vd->vdev_copy_uberblocks = B_TRUE;
 
 	vd->vdev_psize = psize;
 
 	/*
 	 * Make sure the allocatable size hasn't shrunk too much.
 	 */
 	if (asize < vd->vdev_min_asize) {
 		vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_BAD_LABEL);
 		return (SET_ERROR(EINVAL));
 	}
 
 	/*
 	 * We can always set the logical/physical ashift members since
 	 * their values are only used to calculate the vdev_ashift when
 	 * the device is first added to the config. These values should
 	 * not be used for anything else since they may change whenever
 	 * the device is reopened and we don't store them in the label.
 	 */
 	vd->vdev_physical_ashift =
 	    MAX(physical_ashift, vd->vdev_physical_ashift);
 	vd->vdev_logical_ashift = MAX(logical_ashift,
 	    vd->vdev_logical_ashift);
 
 	if (vd->vdev_asize == 0) {
 		/*
 		 * This is the first-ever open, so use the computed values.
 		 * For compatibility, a different ashift can be requested.
 		 */
 		vd->vdev_asize = asize;
 		vd->vdev_max_asize = max_asize;
 
 		/*
 		 * If the vdev_ashift was not overridden at creation time,
 		 * then set it the logical ashift and optimize the ashift.
 		 */
 		if (vd->vdev_ashift == 0) {
 			vd->vdev_ashift = vd->vdev_logical_ashift;
 
 			if (vd->vdev_logical_ashift > ASHIFT_MAX) {
 				vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
 				    VDEV_AUX_ASHIFT_TOO_BIG);
 				return (SET_ERROR(EDOM));
 			}
 
 			if (vd->vdev_top == vd && vd->vdev_attaching == B_FALSE)
 				vdev_ashift_optimize(vd);
 			vd->vdev_attaching = B_FALSE;
 		}
 		if (vd->vdev_ashift != 0 && (vd->vdev_ashift < ASHIFT_MIN ||
 		    vd->vdev_ashift > ASHIFT_MAX)) {
 			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_BAD_ASHIFT);
 			return (SET_ERROR(EDOM));
 		}
 	} else {
 		/*
 		 * Make sure the alignment required hasn't increased.
 		 */
 		if (vd->vdev_ashift > vd->vdev_top->vdev_ashift &&
 		    vd->vdev_ops->vdev_op_leaf) {
 			(void) zfs_ereport_post(
 			    FM_EREPORT_ZFS_DEVICE_BAD_ASHIFT,
 			    spa, vd, NULL, NULL, 0);
 			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_BAD_LABEL);
 			return (SET_ERROR(EDOM));
 		}
 		vd->vdev_max_asize = max_asize;
 	}
 
 	/*
 	 * If all children are healthy we update asize if either:
 	 * The asize has increased, due to a device expansion caused by dynamic
 	 * LUN growth or vdev replacement, and automatic expansion is enabled;
 	 * making the additional space available.
 	 *
 	 * The asize has decreased, due to a device shrink usually caused by a
 	 * vdev replace with a smaller device. This ensures that calculations
 	 * based of max_asize and asize e.g. esize are always valid. It's safe
 	 * to do this as we've already validated that asize is greater than
 	 * vdev_min_asize.
 	 */
 	if (vd->vdev_state == VDEV_STATE_HEALTHY &&
 	    ((asize > vd->vdev_asize &&
 	    (vd->vdev_expanding || spa->spa_autoexpand)) ||
 	    (asize < vd->vdev_asize)))
 		vd->vdev_asize = asize;
 
 	vdev_set_min_asize(vd);
 
 	/*
 	 * 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_FAULTED,
 		    VDEV_AUX_ERR_EXCEEDED);
 		return (error);
 	}
 
 	/*
 	 * Track the minimum allocation size.
 	 */
 	if (vd->vdev_top == vd && vd->vdev_ashift != 0 &&
 	    vd->vdev_islog == 0 && vd->vdev_aux == NULL) {
 		uint64_t min_alloc = vdev_get_min_alloc(vd);
 		vdev_spa_set_alloc(spa, min_alloc);
 	}
 
 	/*
 	 * If this is a leaf vdev, assess whether a resilver is needed.
 	 * 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_ops->vdev_op_leaf && !spa->spa_scrub_reopen)
 		dsl_scan_assess_vdev(spa->spa_dsl_pool, vd);
 
 	return (0);
 }
 
 static void
 vdev_validate_child(void *arg)
 {
 	vdev_t *vd = arg;
 
 	vd->vdev_validate_thread = curthread;
 	vd->vdev_validate_error = vdev_validate(vd);
 	vd->vdev_validate_thread = NULL;
 }
 
 /*
  * 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;
 	taskq_t *tq = NULL;
 	nvlist_t *label;
 	uint64_t guid = 0, aux_guid = 0, top_guid;
 	uint64_t state;
 	nvlist_t *nvl;
 	uint64_t txg;
 	int children = vd->vdev_children;
 
 	if (vdev_validate_skip)
 		return (0);
 
 	if (children > 0) {
 		tq = taskq_create("vdev_validate", children, minclsyspri,
 		    children, children, TASKQ_PREPOPULATE);
 	}
 
 	for (uint64_t c = 0; c < children; c++) {
 		vdev_t *cvd = vd->vdev_child[c];
 
 		if (tq == NULL || vdev_uses_zvols(cvd)) {
 			vdev_validate_child(cvd);
 		} else {
 			VERIFY(taskq_dispatch(tq, vdev_validate_child, cvd,
 			    TQ_SLEEP) != TASKQID_INVALID);
 		}
 	}
 	if (tq != NULL) {
 		taskq_wait(tq);
 		taskq_destroy(tq);
 	}
 	for (int c = 0; c < children; c++) {
 		int error = vd->vdev_child[c]->vdev_validate_error;
 
 		if (error != 0)
 			return (SET_ERROR(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))
 		return (0);
 
 	/*
 	 * If we are performing an extreme rewind, we allow for a label that
 	 * was modified at a point after the current txg.
 	 * If config lock is not held do not check for the txg. spa_sync could
 	 * be updating the vdev's label before updating spa_last_synced_txg.
 	 */
 	if (spa->spa_extreme_rewind || spa_last_synced_txg(spa) == 0 ||
 	    spa_config_held(spa, SCL_CONFIG, RW_WRITER) != SCL_CONFIG)
 		txg = UINT64_MAX;
 	else
 		txg = spa_last_synced_txg(spa);
 
 	if ((label = vdev_label_read_config(vd, txg)) == NULL) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_BAD_LABEL);
 		vdev_dbgmsg(vd, "vdev_validate: failed reading config for "
 		    "txg %llu", (u_longlong_t)txg);
 		return (0);
 	}
 
 	/*
 	 * Determine if this vdev has been split off into another
 	 * pool.  If so, then refuse to open it.
 	 */
 	if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_SPLIT_GUID,
 	    &aux_guid) == 0 && aux_guid == spa_guid(spa)) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_SPLIT_POOL);
 		nvlist_free(label);
 		vdev_dbgmsg(vd, "vdev_validate: vdev split into other pool");
 		return (0);
 	}
 
 	if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &guid) != 0) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_CORRUPT_DATA);
 		nvlist_free(label);
 		vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
 		    ZPOOL_CONFIG_POOL_GUID);
 		return (0);
 	}
 
 	/*
 	 * If config is not trusted then ignore the spa guid check. This is
 	 * necessary because if the machine crashed during a re-guid the new
 	 * guid might have been written to all of the vdev labels, but not the
 	 * cached config. The check will be performed again once we have the
 	 * trusted config from the MOS.
 	 */
 	if (spa->spa_trust_config && guid != spa_guid(spa)) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_CORRUPT_DATA);
 		nvlist_free(label);
 		vdev_dbgmsg(vd, "vdev_validate: vdev label pool_guid doesn't "
 		    "match config (%llu != %llu)", (u_longlong_t)guid,
 		    (u_longlong_t)spa_guid(spa));
 		return (0);
 	}
 
 	if (nvlist_lookup_nvlist(label, ZPOOL_CONFIG_VDEV_TREE, &nvl)
 	    != 0 || nvlist_lookup_uint64(nvl, ZPOOL_CONFIG_ORIG_GUID,
 	    &aux_guid) != 0)
 		aux_guid = 0;
 
 	if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &guid) != 0) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_CORRUPT_DATA);
 		nvlist_free(label);
 		vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
 		    ZPOOL_CONFIG_GUID);
 		return (0);
 	}
 
 	if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_TOP_GUID, &top_guid)
 	    != 0) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_CORRUPT_DATA);
 		nvlist_free(label);
 		vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
 		    ZPOOL_CONFIG_TOP_GUID);
 		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.
 	 * However, if the config comes from a cachefile that failed to update
 	 * after the detach, a top-level vdev will appear as a non top-level
 	 * vdev in the config. Also relax the constraints if we perform an
 	 * extreme rewind.
 	 *
 	 * If we split this vdev off instead, then we also check the
 	 * original pool's guid. We don't want to consider the vdev
 	 * corrupt if it is partway through a split operation.
 	 */
 	if (vd->vdev_guid != guid && vd->vdev_guid != aux_guid) {
 		boolean_t mismatch = B_FALSE;
 		if (spa->spa_trust_config && !spa->spa_extreme_rewind) {
 			if (vd != vd->vdev_top || vd->vdev_guid != top_guid)
 				mismatch = B_TRUE;
 		} else {
 			if (vd->vdev_guid != top_guid &&
 			    vd->vdev_top->vdev_guid != guid)
 				mismatch = B_TRUE;
 		}
 
 		if (mismatch) {
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_CORRUPT_DATA);
 			nvlist_free(label);
 			vdev_dbgmsg(vd, "vdev_validate: config guid "
 			    "doesn't match label guid");
 			vdev_dbgmsg(vd, "CONFIG: guid %llu, top_guid %llu",
 			    (u_longlong_t)vd->vdev_guid,
 			    (u_longlong_t)vd->vdev_top->vdev_guid);
 			vdev_dbgmsg(vd, "LABEL: guid %llu, top_guid %llu, "
 			    "aux_guid %llu", (u_longlong_t)guid,
 			    (u_longlong_t)top_guid, (u_longlong_t)aux_guid);
 			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);
 		vdev_dbgmsg(vd, "vdev_validate: '%s' missing from label",
 		    ZPOOL_CONFIG_POOL_STATE);
 		return (0);
 	}
 
 	nvlist_free(label);
 
 	/*
 	 * If this is a verbatim import, no need to check the
 	 * state of the pool.
 	 */
 	if (!(spa->spa_import_flags & ZFS_IMPORT_VERBATIM) &&
 	    spa_load_state(spa) == SPA_LOAD_OPEN &&
 	    state != POOL_STATE_ACTIVE) {
 		vdev_dbgmsg(vd, "vdev_validate: invalid pool state (%llu) "
 		    "for spa %s", (u_longlong_t)state, spa->spa_name);
 		return (SET_ERROR(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);
 }
 
 static void
 vdev_update_path(const char *prefix, char *svd, char **dvd, uint64_t guid)
 {
 	if (svd != NULL && *dvd != NULL) {
 		if (strcmp(svd, *dvd) != 0) {
 			zfs_dbgmsg("vdev_copy_path: vdev %llu: %s changed "
 			    "from '%s' to '%s'", (u_longlong_t)guid, prefix,
 			    *dvd, svd);
 			spa_strfree(*dvd);
 			*dvd = spa_strdup(svd);
 		}
 	} else if (svd != NULL) {
 		*dvd = spa_strdup(svd);
 		zfs_dbgmsg("vdev_copy_path: vdev %llu: path set to '%s'",
 		    (u_longlong_t)guid, *dvd);
 	}
 }
 
 static void
 vdev_copy_path_impl(vdev_t *svd, vdev_t *dvd)
 {
 	char *old, *new;
 
 	vdev_update_path("vdev_path", svd->vdev_path, &dvd->vdev_path,
 	    dvd->vdev_guid);
 
 	vdev_update_path("vdev_devid", svd->vdev_devid, &dvd->vdev_devid,
 	    dvd->vdev_guid);
 
 	vdev_update_path("vdev_physpath", svd->vdev_physpath,
 	    &dvd->vdev_physpath, dvd->vdev_guid);
 
 	/*
 	 * Our enclosure sysfs path may have changed between imports
 	 */
 	old = dvd->vdev_enc_sysfs_path;
 	new = svd->vdev_enc_sysfs_path;
 	if ((old != NULL && new == NULL) ||
 	    (old == NULL && new != NULL) ||
 	    ((old != NULL && new != NULL) && strcmp(new, old) != 0)) {
 		zfs_dbgmsg("vdev_copy_path: vdev %llu: vdev_enc_sysfs_path "
 		    "changed from '%s' to '%s'", (u_longlong_t)dvd->vdev_guid,
 		    old, new);
 
 		if (dvd->vdev_enc_sysfs_path)
 			spa_strfree(dvd->vdev_enc_sysfs_path);
 
 		if (svd->vdev_enc_sysfs_path) {
 			dvd->vdev_enc_sysfs_path = spa_strdup(
 			    svd->vdev_enc_sysfs_path);
 		} else {
 			dvd->vdev_enc_sysfs_path = NULL;
 		}
 	}
 }
 
 /*
  * Recursively copy vdev paths from one vdev to another. Source and destination
  * vdev trees must have same geometry otherwise return error. Intended to copy
  * paths from userland config into MOS config.
  */
 int
 vdev_copy_path_strict(vdev_t *svd, vdev_t *dvd)
 {
 	if ((svd->vdev_ops == &vdev_missing_ops) ||
 	    (svd->vdev_ishole && dvd->vdev_ishole) ||
 	    (dvd->vdev_ops == &vdev_indirect_ops))
 		return (0);
 
 	if (svd->vdev_ops != dvd->vdev_ops) {
 		vdev_dbgmsg(svd, "vdev_copy_path: vdev type mismatch: %s != %s",
 		    svd->vdev_ops->vdev_op_type, dvd->vdev_ops->vdev_op_type);
 		return (SET_ERROR(EINVAL));
 	}
 
 	if (svd->vdev_guid != dvd->vdev_guid) {
 		vdev_dbgmsg(svd, "vdev_copy_path: guids mismatch (%llu != "
 		    "%llu)", (u_longlong_t)svd->vdev_guid,
 		    (u_longlong_t)dvd->vdev_guid);
 		return (SET_ERROR(EINVAL));
 	}
 
 	if (svd->vdev_children != dvd->vdev_children) {
 		vdev_dbgmsg(svd, "vdev_copy_path: children count mismatch: "
 		    "%llu != %llu", (u_longlong_t)svd->vdev_children,
 		    (u_longlong_t)dvd->vdev_children);
 		return (SET_ERROR(EINVAL));
 	}
 
 	for (uint64_t i = 0; i < svd->vdev_children; i++) {
 		int error = vdev_copy_path_strict(svd->vdev_child[i],
 		    dvd->vdev_child[i]);
 		if (error != 0)
 			return (error);
 	}
 
 	if (svd->vdev_ops->vdev_op_leaf)
 		vdev_copy_path_impl(svd, dvd);
 
 	return (0);
 }
 
 static void
 vdev_copy_path_search(vdev_t *stvd, vdev_t *dvd)
 {
 	ASSERT(stvd->vdev_top == stvd);
 	ASSERT3U(stvd->vdev_id, ==, dvd->vdev_top->vdev_id);
 
 	for (uint64_t i = 0; i < dvd->vdev_children; i++) {
 		vdev_copy_path_search(stvd, dvd->vdev_child[i]);
 	}
 
 	if (!dvd->vdev_ops->vdev_op_leaf || !vdev_is_concrete(dvd))
 		return;
 
 	/*
 	 * The idea here is that while a vdev can shift positions within
 	 * a top vdev (when replacing, attaching mirror, etc.) it cannot
 	 * step outside of it.
 	 */
 	vdev_t *vd = vdev_lookup_by_guid(stvd, dvd->vdev_guid);
 
 	if (vd == NULL || vd->vdev_ops != dvd->vdev_ops)
 		return;
 
 	ASSERT(vd->vdev_ops->vdev_op_leaf);
 
 	vdev_copy_path_impl(vd, dvd);
 }
 
 /*
  * Recursively copy vdev paths from one root vdev to another. Source and
  * destination vdev trees may differ in geometry. For each destination leaf
  * vdev, search a vdev with the same guid and top vdev id in the source.
  * Intended to copy paths from userland config into MOS config.
  */
 void
 vdev_copy_path_relaxed(vdev_t *srvd, vdev_t *drvd)
 {
 	uint64_t children = MIN(srvd->vdev_children, drvd->vdev_children);
 	ASSERT(srvd->vdev_ops == &vdev_root_ops);
 	ASSERT(drvd->vdev_ops == &vdev_root_ops);
 
 	for (uint64_t i = 0; i < children; i++) {
 		vdev_copy_path_search(srvd->vdev_child[i],
 		    drvd->vdev_child[i]);
 	}
 }
 
 /*
  * Close a virtual device.
  */
 void
 vdev_close(vdev_t *vd)
 {
 	vdev_t *pvd = vd->vdev_parent;
 	spa_t *spa __maybe_unused = vd->vdev_spa;
 
 	ASSERT(vd != NULL);
 	ASSERT(vd->vdev_open_thread == curthread ||
 	    spa_config_held(spa, SCL_STATE_ALL, RW_WRITER) == SCL_STATE_ALL);
 
 	/*
 	 * If our parent is reopening, then we are as well, unless we are
 	 * going offline.
 	 */
 	if (pvd != NULL && pvd->vdev_reopening)
 		vd->vdev_reopening = (pvd->vdev_reopening && !vd->vdev_offline);
 
 	vd->vdev_ops->vdev_op_close(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_hold(vdev_t *vd)
 {
 	spa_t *spa = vd->vdev_spa;
 
 	ASSERT(spa_is_root(spa));
 	if (spa->spa_state == POOL_STATE_UNINITIALIZED)
 		return;
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_hold(vd->vdev_child[c]);
 
 	if (vd->vdev_ops->vdev_op_leaf && vd->vdev_ops->vdev_op_hold != NULL)
 		vd->vdev_ops->vdev_op_hold(vd);
 }
 
 void
 vdev_rele(vdev_t *vd)
 {
 	ASSERT(spa_is_root(vd->vdev_spa));
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_rele(vd->vdev_child[c]);
 
 	if (vd->vdev_ops->vdev_op_leaf && vd->vdev_ops->vdev_op_rele != NULL)
 		vd->vdev_ops->vdev_op_rele(vd);
 }
 
 /*
  * Reopen all interior vdevs and any unopened leaves.  We don't actually
  * reopen leaf vdevs which had previously been opened as they might deadlock
  * on the spa_config_lock.  Instead we only obtain the leaf's physical size.
  * If the leaf has never been opened then open it, as usual.
  */
 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);
 
 	/* set the reopening flag unless we're taking the vdev offline */
 	vd->vdev_reopening = !vd->vdev_offline;
 	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) &&
 		    vd->vdev_aux == &spa->spa_l2cache) {
 			/*
 			 * In case the vdev is present we should evict all ARC
 			 * buffers and pointers to log blocks and reclaim their
 			 * space before restoring its contents to L2ARC.
 			 */
 			if (l2arc_vdev_present(vd)) {
 				l2arc_rebuild_vdev(vd, B_TRUE);
 			} else {
 				l2arc_add_vdev(spa, vd);
 			}
 			spa_async_request(spa, SPA_ASYNC_L2CACHE_REBUILD);
 			spa_async_request(spa, SPA_ASYNC_L2CACHE_TRIM);
 		}
 	} else {
 		(void) vdev_validate(vd);
 	}
 
 	/*
 	 * Recheck if resilver is still needed and cancel any
 	 * scheduled resilver if resilver is unneeded.
 	 */
 	if (!vdev_resilver_needed(spa->spa_root_vdev, NULL, NULL) &&
 	    spa->spa_async_tasks & SPA_ASYNC_RESILVER) {
 		mutex_enter(&spa->spa_async_lock);
 		spa->spa_async_tasks &= ~SPA_ASYNC_RESILVER;
 		mutex_exit(&spa->spa_async_lock);
 	}
 
 	/*
 	 * 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 : SET_ERROR(ENXIO));
 	}
 
 	/*
 	 * Recursively load DTLs and initialize all labels.
 	 */
 	if ((error = vdev_dtl_load(vd)) != 0 ||
 	    (error = vdev_label_init(vd, txg, isreplacing ?
 	    VDEV_LABEL_REPLACE : VDEV_LABEL_CREATE)) != 0) {
 		vdev_close(vd);
 		return (error);
 	}
 
 	return (0);
 }
 
 void
 vdev_metaslab_set_size(vdev_t *vd)
 {
 	uint64_t asize = vd->vdev_asize;
 	uint64_t ms_count = asize >> zfs_vdev_default_ms_shift;
 	uint64_t ms_shift;
 
 	/*
 	 * There are two dimensions to the metaslab sizing calculation:
 	 * the size of the metaslab and the count of metaslabs per vdev.
 	 *
 	 * The default values used below are a good balance between memory
 	 * usage (larger metaslab size means more memory needed for loaded
 	 * metaslabs; more metaslabs means more memory needed for the
 	 * metaslab_t structs), metaslab load time (larger metaslabs take
 	 * longer to load), and metaslab sync time (more metaslabs means
 	 * more time spent syncing all of them).
 	 *
 	 * In general, we aim for zfs_vdev_default_ms_count (200) metaslabs.
 	 * The range of the dimensions are as follows:
 	 *
 	 *	2^29 <= ms_size  <= 2^34
 	 *	  16 <= ms_count <= 131,072
 	 *
 	 * On the lower end of vdev sizes, we aim for metaslabs sizes of
 	 * at least 512MB (2^29) to minimize fragmentation effects when
 	 * testing with smaller devices.  However, the count constraint
 	 * of at least 16 metaslabs will override this minimum size goal.
 	 *
 	 * On the upper end of vdev sizes, we aim for a maximum metaslab
 	 * size of 16GB.  However, we will cap the total count to 2^17
 	 * metaslabs to keep our memory footprint in check and let the
 	 * metaslab size grow from there if that limit is hit.
 	 *
 	 * The net effect of applying above constrains is summarized below.
 	 *
 	 *   vdev size       metaslab count
 	 *  --------------|-----------------
 	 *      < 8GB        ~16
 	 *  8GB   - 100GB   one per 512MB
 	 *  100GB - 3TB     ~200
 	 *  3TB   - 2PB     one per 16GB
 	 *      > 2PB       ~131,072
 	 *  --------------------------------
 	 *
 	 *  Finally, note that all of the above calculate the initial
 	 *  number of metaslabs. Expanding a top-level vdev will result
 	 *  in additional metaslabs being allocated making it possible
 	 *  to exceed the zfs_vdev_ms_count_limit.
 	 */
 
 	if (ms_count < zfs_vdev_min_ms_count)
 		ms_shift = highbit64(asize / zfs_vdev_min_ms_count);
 	else if (ms_count > zfs_vdev_default_ms_count)
 		ms_shift = highbit64(asize / zfs_vdev_default_ms_count);
 	else
 		ms_shift = zfs_vdev_default_ms_shift;
 
 	if (ms_shift < SPA_MAXBLOCKSHIFT) {
 		ms_shift = SPA_MAXBLOCKSHIFT;
 	} else if (ms_shift > zfs_vdev_max_ms_shift) {
 		ms_shift = zfs_vdev_max_ms_shift;
 		/* cap the total count to constrain memory footprint */
 		if ((asize >> ms_shift) > zfs_vdev_ms_count_limit)
 			ms_shift = highbit64(asize / zfs_vdev_ms_count_limit);
 	}
 
 	vd->vdev_ms_shift = ms_shift;
 	ASSERT3U(vd->vdev_ms_shift, >=, SPA_MAXBLOCKSHIFT);
 }
 
 void
 vdev_dirty(vdev_t *vd, int flags, void *arg, uint64_t txg)
 {
 	ASSERT(vd == vd->vdev_top);
 	/* indirect vdevs don't have metaslabs or dtls */
 	ASSERT(vdev_is_concrete(vd) || flags == 0);
 	ASSERT(ISP2(flags));
 	ASSERT(spa_writeable(vd->vdev_spa));
 
 	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_dirty_leaves(vdev_t *vd, int flags, uint64_t txg)
 {
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_dirty_leaves(vd->vdev_child[c], flags, txg);
 
 	if (vd->vdev_ops->vdev_op_leaf)
 		vdev_dirty(vd->vdev_top, flags, 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 four 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(vdev_t *vd, vdev_dtl_type_t t, uint64_t txg, uint64_t size)
 {
 	range_tree_t *rt = vd->vdev_dtl[t];
 
 	ASSERT(t < DTL_TYPES);
 	ASSERT(vd != vd->vdev_spa->spa_root_vdev);
 	ASSERT(spa_writeable(vd->vdev_spa));
 
 	mutex_enter(&vd->vdev_dtl_lock);
 	if (!range_tree_contains(rt, txg, size))
 		range_tree_add(rt, txg, size);
 	mutex_exit(&vd->vdev_dtl_lock);
 }
 
 boolean_t
 vdev_dtl_contains(vdev_t *vd, vdev_dtl_type_t t, uint64_t txg, uint64_t size)
 {
 	range_tree_t *rt = vd->vdev_dtl[t];
 	boolean_t dirty = B_FALSE;
 
 	ASSERT(t < DTL_TYPES);
 	ASSERT(vd != vd->vdev_spa->spa_root_vdev);
 
 	/*
 	 * While we are loading the pool, the DTLs have not been loaded yet.
 	 * This isn't a problem but it can result in devices being tried
 	 * which are known to not have the data.  In which case, the import
 	 * is relying on the checksum to ensure that we get the right data.
 	 * Note that while importing we are only reading the MOS, which is
 	 * always checksummed.
 	 */
 	mutex_enter(&vd->vdev_dtl_lock);
 	if (!range_tree_is_empty(rt))
 		dirty = range_tree_contains(rt, txg, size);
 	mutex_exit(&vd->vdev_dtl_lock);
 
 	return (dirty);
 }
 
 boolean_t
 vdev_dtl_empty(vdev_t *vd, vdev_dtl_type_t t)
 {
 	range_tree_t *rt = vd->vdev_dtl[t];
 	boolean_t empty;
 
 	mutex_enter(&vd->vdev_dtl_lock);
 	empty = range_tree_is_empty(rt);
 	mutex_exit(&vd->vdev_dtl_lock);
 
 	return (empty);
 }
 
 /*
  * Check if the txg falls within the range which must be
  * resilvered.  DVAs outside this range can always be skipped.
  */
 boolean_t
 vdev_default_need_resilver(vdev_t *vd, const dva_t *dva, size_t psize,
     uint64_t phys_birth)
 {
 	(void) dva, (void) psize;
 
 	/* Set by sequential resilver. */
 	if (phys_birth == TXG_UNKNOWN)
 		return (B_TRUE);
 
 	return (vdev_dtl_contains(vd, DTL_PARTIAL, phys_birth, 1));
 }
 
 /*
  * Returns B_TRUE if the vdev determines the DVA needs to be resilvered.
  */
 boolean_t
 vdev_dtl_need_resilver(vdev_t *vd, const dva_t *dva, size_t psize,
     uint64_t phys_birth)
 {
 	ASSERT(vd != vd->vdev_spa->spa_root_vdev);
 
 	if (vd->vdev_ops->vdev_op_need_resilver == NULL ||
 	    vd->vdev_ops->vdev_op_leaf)
 		return (B_TRUE);
 
 	return (vd->vdev_ops->vdev_op_need_resilver(vd, dva, psize,
 	    phys_birth));
 }
 
 /*
  * Returns the lowest txg in the DTL range.
  */
 static uint64_t
 vdev_dtl_min(vdev_t *vd)
 {
 	ASSERT(MUTEX_HELD(&vd->vdev_dtl_lock));
 	ASSERT3U(range_tree_space(vd->vdev_dtl[DTL_MISSING]), !=, 0);
 	ASSERT0(vd->vdev_children);
 
 	return (range_tree_min(vd->vdev_dtl[DTL_MISSING]) - 1);
 }
 
 /*
  * Returns the highest txg in the DTL.
  */
 static uint64_t
 vdev_dtl_max(vdev_t *vd)
 {
 	ASSERT(MUTEX_HELD(&vd->vdev_dtl_lock));
 	ASSERT3U(range_tree_space(vd->vdev_dtl[DTL_MISSING]), !=, 0);
 	ASSERT0(vd->vdev_children);
 
 	return (range_tree_max(vd->vdev_dtl[DTL_MISSING]));
 }
 
 /*
  * Determine if a resilvering vdev should remove any DTL entries from
  * its range. If the vdev was resilvering for the entire duration of the
  * scan then it should excise that range from its DTLs. Otherwise, this
  * vdev is considered partially resilvered and should leave its DTL
  * entries intact. The comment in vdev_dtl_reassess() describes how we
  * excise the DTLs.
  */
 static boolean_t
 vdev_dtl_should_excise(vdev_t *vd, boolean_t rebuild_done)
 {
 	ASSERT0(vd->vdev_children);
 
 	if (vd->vdev_state < VDEV_STATE_DEGRADED)
 		return (B_FALSE);
 
 	if (vd->vdev_resilver_deferred)
 		return (B_FALSE);
 
 	if (range_tree_is_empty(vd->vdev_dtl[DTL_MISSING]))
 		return (B_TRUE);
 
 	if (rebuild_done) {
 		vdev_rebuild_t *vr = &vd->vdev_top->vdev_rebuild_config;
 		vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
 
 		/* Rebuild not initiated by attach */
 		if (vd->vdev_rebuild_txg == 0)
 			return (B_TRUE);
 
 		/*
 		 * When a rebuild completes without error then all missing data
 		 * up to the rebuild max txg has been reconstructed and the DTL
 		 * is eligible for excision.
 		 */
 		if (vrp->vrp_rebuild_state == VDEV_REBUILD_COMPLETE &&
 		    vdev_dtl_max(vd) <= vrp->vrp_max_txg) {
 			ASSERT3U(vrp->vrp_min_txg, <=, vdev_dtl_min(vd));
 			ASSERT3U(vrp->vrp_min_txg, <, vd->vdev_rebuild_txg);
 			ASSERT3U(vd->vdev_rebuild_txg, <=, vrp->vrp_max_txg);
 			return (B_TRUE);
 		}
 	} else {
 		dsl_scan_t *scn = vd->vdev_spa->spa_dsl_pool->dp_scan;
 		dsl_scan_phys_t *scnp __maybe_unused = &scn->scn_phys;
 
 		/* Resilver not initiated by attach */
 		if (vd->vdev_resilver_txg == 0)
 			return (B_TRUE);
 
 		/*
 		 * When a resilver is initiated the scan will assign the
 		 * scn_max_txg value to the highest txg value that exists
 		 * in all DTLs. If this device's max DTL is not part of this
 		 * scan (i.e. it is not in the range (scn_min_txg, scn_max_txg]
 		 * then it is not eligible for excision.
 		 */
 		if (vdev_dtl_max(vd) <= scn->scn_phys.scn_max_txg) {
 			ASSERT3U(scnp->scn_min_txg, <=, vdev_dtl_min(vd));
 			ASSERT3U(scnp->scn_min_txg, <, vd->vdev_resilver_txg);
 			ASSERT3U(vd->vdev_resilver_txg, <=, scnp->scn_max_txg);
 			return (B_TRUE);
 		}
 	}
 
 	return (B_FALSE);
 }
 
 /*
  * Reassess DTLs after a config change or scrub completion. If txg == 0 no
  * write operations will be issued to the pool.
  */
 void
 vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg,
     boolean_t scrub_done, boolean_t rebuild_done)
 {
 	spa_t *spa = vd->vdev_spa;
 	avl_tree_t reftree;
 	int minref;
 
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_READER) != 0);
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_dtl_reassess(vd->vdev_child[c], txg,
 		    scrub_txg, scrub_done, rebuild_done);
 
 	if (vd == spa->spa_root_vdev || !vdev_is_concrete(vd) || vd->vdev_aux)
 		return;
 
 	if (vd->vdev_ops->vdev_op_leaf) {
 		dsl_scan_t *scn = spa->spa_dsl_pool->dp_scan;
 		vdev_rebuild_t *vr = &vd->vdev_top->vdev_rebuild_config;
 		boolean_t check_excise = B_FALSE;
 		boolean_t wasempty = B_TRUE;
 
 		mutex_enter(&vd->vdev_dtl_lock);
 
 		/*
 		 * If requested, pretend the scan or rebuild completed cleanly.
 		 */
 		if (zfs_scan_ignore_errors) {
 			if (scn != NULL)
 				scn->scn_phys.scn_errors = 0;
 			if (vr != NULL)
 				vr->vr_rebuild_phys.vrp_errors = 0;
 		}
 
 		if (scrub_txg != 0 &&
 		    !range_tree_is_empty(vd->vdev_dtl[DTL_MISSING])) {
 			wasempty = B_FALSE;
 			zfs_dbgmsg("guid:%llu txg:%llu scrub:%llu started:%d "
 			    "dtl:%llu/%llu errors:%llu",
 			    (u_longlong_t)vd->vdev_guid, (u_longlong_t)txg,
 			    (u_longlong_t)scrub_txg, spa->spa_scrub_started,
 			    (u_longlong_t)vdev_dtl_min(vd),
 			    (u_longlong_t)vdev_dtl_max(vd),
 			    (u_longlong_t)(scn ? scn->scn_phys.scn_errors : 0));
 		}
 
 		/*
 		 * If we've completed a scrub/resilver or a rebuild cleanly
 		 * then determine if this vdev should remove any DTLs. We
 		 * only want to excise regions on vdevs that were available
 		 * during the entire duration of this scan.
 		 */
 		if (rebuild_done &&
 		    vr != NULL && vr->vr_rebuild_phys.vrp_errors == 0) {
 			check_excise = B_TRUE;
 		} else {
 			if (spa->spa_scrub_started ||
 			    (scn != NULL && scn->scn_phys.scn_errors == 0)) {
 				check_excise = B_TRUE;
 			}
 		}
 
 		if (scrub_txg && check_excise &&
 		    vdev_dtl_should_excise(vd, rebuild_done)) {
 			/*
 			 * We completed a scrub, resilver or rebuild 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.
 			 *
 			 * 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_reftree_create(&reftree);
 			space_reftree_add_map(&reftree,
 			    vd->vdev_dtl[DTL_MISSING], 1);
 			space_reftree_add_seg(&reftree, 0, scrub_txg, -1);
 			space_reftree_add_map(&reftree,
 			    vd->vdev_dtl[DTL_SCRUB], 2);
 			space_reftree_generate_map(&reftree,
 			    vd->vdev_dtl[DTL_MISSING], 1);
 			space_reftree_destroy(&reftree);
 
 			if (!range_tree_is_empty(vd->vdev_dtl[DTL_MISSING])) {
 				zfs_dbgmsg("update DTL_MISSING:%llu/%llu",
 				    (u_longlong_t)vdev_dtl_min(vd),
 				    (u_longlong_t)vdev_dtl_max(vd));
 			} else if (!wasempty) {
 				zfs_dbgmsg("DTL_MISSING is now empty");
 			}
 		}
 		range_tree_vacate(vd->vdev_dtl[DTL_PARTIAL], NULL, NULL);
 		range_tree_walk(vd->vdev_dtl[DTL_MISSING],
 		    range_tree_add, vd->vdev_dtl[DTL_PARTIAL]);
 		if (scrub_done)
 			range_tree_vacate(vd->vdev_dtl[DTL_SCRUB], NULL, NULL);
 		range_tree_vacate(vd->vdev_dtl[DTL_OUTAGE], NULL, NULL);
 		if (!vdev_readable(vd))
 			range_tree_add(vd->vdev_dtl[DTL_OUTAGE], 0, -1ULL);
 		else
 			range_tree_walk(vd->vdev_dtl[DTL_MISSING],
 			    range_tree_add, vd->vdev_dtl[DTL_OUTAGE]);
 
 		/*
 		 * If the vdev was resilvering or rebuilding and no longer
 		 * has any DTLs then reset the appropriate flag and dirty
 		 * the top level so that we persist the change.
 		 */
 		if (txg != 0 &&
 		    range_tree_is_empty(vd->vdev_dtl[DTL_MISSING]) &&
 		    range_tree_is_empty(vd->vdev_dtl[DTL_OUTAGE])) {
 			if (vd->vdev_rebuild_txg != 0) {
 				vd->vdev_rebuild_txg = 0;
 				vdev_config_dirty(vd->vdev_top);
 			} else if (vd->vdev_resilver_txg != 0) {
 				vd->vdev_resilver_txg = 0;
 				vdev_config_dirty(vd->vdev_top);
 			}
 		}
 
 		mutex_exit(&vd->vdev_dtl_lock);
 
 		if (txg != 0)
 			vdev_dirty(vd->vdev_top, VDD_DTL, vd, txg);
 	} else {
 		mutex_enter(&vd->vdev_dtl_lock);
 		for (int t = 0; t < DTL_TYPES; t++) {
 			/* account for child's outage in parent's missing map */
 			int s = (t == DTL_MISSING) ? DTL_OUTAGE: t;
 			if (t == DTL_SCRUB) {
 				/* leaf vdevs only */
 				continue;
 			}
 			if (t == DTL_PARTIAL) {
 				/* i.e. non-zero */
 				minref = 1;
 			} else if (vdev_get_nparity(vd) != 0) {
 				/* RAIDZ, DRAID */
 				minref = vdev_get_nparity(vd) + 1;
 			} else {
 				/* any kind of mirror */
 				minref = vd->vdev_children;
 			}
 			space_reftree_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_reftree_add_map(&reftree,
 				    cvd->vdev_dtl[s], 1);
 				mutex_exit(&cvd->vdev_dtl_lock);
 			}
 			space_reftree_generate_map(&reftree,
 			    vd->vdev_dtl[t], minref);
 			space_reftree_destroy(&reftree);
 		}
 		mutex_exit(&vd->vdev_dtl_lock);
 	}
 
 	if (vd->vdev_top->vdev_ops == &vdev_raidz_ops) {
 		raidz_dtl_reassessed(vd);
 	}
 }
 
 /*
  * Iterate over all the vdevs except spare, and post kobj events
  */
 void
 vdev_post_kobj_evt(vdev_t *vd)
 {
 	if (vd->vdev_ops->vdev_op_kobj_evt_post &&
 	    vd->vdev_kobj_flag == B_FALSE) {
 		vd->vdev_kobj_flag = B_TRUE;
 		vd->vdev_ops->vdev_op_kobj_evt_post(vd);
 	}
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_post_kobj_evt(vd->vdev_child[c]);
 }
 
 /*
  * Iterate over all the vdevs except spare, and clear kobj events
  */
 void
 vdev_clear_kobj_evt(vdev_t *vd)
 {
 	vd->vdev_kobj_flag = B_FALSE;
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_clear_kobj_evt(vd->vdev_child[c]);
 }
 
 int
 vdev_dtl_load(vdev_t *vd)
 {
 	spa_t *spa = vd->vdev_spa;
 	objset_t *mos = spa->spa_meta_objset;
 	range_tree_t *rt;
 	int error = 0;
 
 	if (vd->vdev_ops->vdev_op_leaf && vd->vdev_dtl_object != 0) {
 		ASSERT(vdev_is_concrete(vd));
 
 		/*
 		 * If the dtl cannot be sync'd there is no need to open it.
 		 */
 		if (spa->spa_mode == SPA_MODE_READ && !spa->spa_read_spacemaps)
 			return (0);
 
 		error = space_map_open(&vd->vdev_dtl_sm, mos,
 		    vd->vdev_dtl_object, 0, -1ULL, 0);
 		if (error)
 			return (error);
 		ASSERT(vd->vdev_dtl_sm != NULL);
 
 		rt = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
 		error = space_map_load(vd->vdev_dtl_sm, rt, SM_ALLOC);
 		if (error == 0) {
 			mutex_enter(&vd->vdev_dtl_lock);
 			range_tree_walk(rt, range_tree_add,
 			    vd->vdev_dtl[DTL_MISSING]);
 			mutex_exit(&vd->vdev_dtl_lock);
 		}
 
 		range_tree_vacate(rt, NULL, NULL);
 		range_tree_destroy(rt);
 
 		return (error);
 	}
 
 	for (int c = 0; c < vd->vdev_children; c++) {
 		error = vdev_dtl_load(vd->vdev_child[c]);
 		if (error != 0)
 			break;
 	}
 
 	return (error);
 }
 
 static void
 vdev_zap_allocation_data(vdev_t *vd, dmu_tx_t *tx)
 {
 	spa_t *spa = vd->vdev_spa;
 	objset_t *mos = spa->spa_meta_objset;
 	vdev_alloc_bias_t alloc_bias = vd->vdev_alloc_bias;
 	const char *string;
 
 	ASSERT(alloc_bias != VDEV_BIAS_NONE);
 
 	string =
 	    (alloc_bias == VDEV_BIAS_LOG) ? VDEV_ALLOC_BIAS_LOG :
 	    (alloc_bias == VDEV_BIAS_SPECIAL) ? VDEV_ALLOC_BIAS_SPECIAL :
 	    (alloc_bias == VDEV_BIAS_DEDUP) ? VDEV_ALLOC_BIAS_DEDUP : NULL;
 
 	ASSERT(string != NULL);
 	VERIFY0(zap_add(mos, vd->vdev_top_zap, VDEV_TOP_ZAP_ALLOCATION_BIAS,
 	    1, strlen(string) + 1, string, tx));
 
 	if (alloc_bias == VDEV_BIAS_SPECIAL || alloc_bias == VDEV_BIAS_DEDUP) {
 		spa_activate_allocation_classes(spa, tx);
 	}
 }
 
 void
 vdev_destroy_unlink_zap(vdev_t *vd, uint64_t zapobj, dmu_tx_t *tx)
 {
 	spa_t *spa = vd->vdev_spa;
 
 	VERIFY0(zap_destroy(spa->spa_meta_objset, zapobj, tx));
 	VERIFY0(zap_remove_int(spa->spa_meta_objset, spa->spa_all_vdev_zaps,
 	    zapobj, tx));
 }
 
 uint64_t
 vdev_create_link_zap(vdev_t *vd, dmu_tx_t *tx)
 {
 	spa_t *spa = vd->vdev_spa;
 	uint64_t zap = zap_create(spa->spa_meta_objset, DMU_OTN_ZAP_METADATA,
 	    DMU_OT_NONE, 0, tx);
 
 	ASSERT(zap != 0);
 	VERIFY0(zap_add_int(spa->spa_meta_objset, spa->spa_all_vdev_zaps,
 	    zap, tx));
 
 	return (zap);
 }
 
 void
 vdev_construct_zaps(vdev_t *vd, dmu_tx_t *tx)
 {
 	if (vd->vdev_ops != &vdev_hole_ops &&
 	    vd->vdev_ops != &vdev_missing_ops &&
 	    vd->vdev_ops != &vdev_root_ops &&
 	    !vd->vdev_top->vdev_removing) {
 		if (vd->vdev_ops->vdev_op_leaf && vd->vdev_leaf_zap == 0) {
 			vd->vdev_leaf_zap = vdev_create_link_zap(vd, tx);
 		}
 		if (vd == vd->vdev_top && vd->vdev_top_zap == 0) {
 			vd->vdev_top_zap = vdev_create_link_zap(vd, tx);
 			if (vd->vdev_alloc_bias != VDEV_BIAS_NONE)
 				vdev_zap_allocation_data(vd, tx);
 		}
 	}
 	if (vd->vdev_ops == &vdev_root_ops && vd->vdev_root_zap == 0 &&
 	    spa_feature_is_enabled(vd->vdev_spa, SPA_FEATURE_AVZ_V2)) {
 		if (!spa_feature_is_active(vd->vdev_spa, SPA_FEATURE_AVZ_V2))
 			spa_feature_incr(vd->vdev_spa, SPA_FEATURE_AVZ_V2, tx);
 		vd->vdev_root_zap = vdev_create_link_zap(vd, tx);
 	}
 
 	for (uint64_t i = 0; i < vd->vdev_children; i++) {
 		vdev_construct_zaps(vd->vdev_child[i], tx);
 	}
 }
 
 static void
 vdev_dtl_sync(vdev_t *vd, uint64_t txg)
 {
 	spa_t *spa = vd->vdev_spa;
 	range_tree_t *rt = vd->vdev_dtl[DTL_MISSING];
 	objset_t *mos = spa->spa_meta_objset;
 	range_tree_t *rtsync;
 	dmu_tx_t *tx;
 	uint64_t object = space_map_object(vd->vdev_dtl_sm);
 
 	ASSERT(vdev_is_concrete(vd));
 	ASSERT(vd->vdev_ops->vdev_op_leaf);
 
 	tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
 
 	if (vd->vdev_detached || vd->vdev_top->vdev_removing) {
 		mutex_enter(&vd->vdev_dtl_lock);
 		space_map_free(vd->vdev_dtl_sm, tx);
 		space_map_close(vd->vdev_dtl_sm);
 		vd->vdev_dtl_sm = NULL;
 		mutex_exit(&vd->vdev_dtl_lock);
 
 		/*
 		 * We only destroy the leaf ZAP for detached leaves or for
 		 * removed log devices. Removed data devices handle leaf ZAP
 		 * cleanup later, once cancellation is no longer possible.
 		 */
 		if (vd->vdev_leaf_zap != 0 && (vd->vdev_detached ||
 		    vd->vdev_top->vdev_islog)) {
 			vdev_destroy_unlink_zap(vd, vd->vdev_leaf_zap, tx);
 			vd->vdev_leaf_zap = 0;
 		}
 
 		dmu_tx_commit(tx);
 		return;
 	}
 
 	if (vd->vdev_dtl_sm == NULL) {
 		uint64_t new_object;
 
 		new_object = space_map_alloc(mos, zfs_vdev_dtl_sm_blksz, tx);
 		VERIFY3U(new_object, !=, 0);
 
 		VERIFY0(space_map_open(&vd->vdev_dtl_sm, mos, new_object,
 		    0, -1ULL, 0));
 		ASSERT(vd->vdev_dtl_sm != NULL);
 	}
 
 	rtsync = range_tree_create(NULL, RANGE_SEG64, NULL, 0, 0);
 
 	mutex_enter(&vd->vdev_dtl_lock);
 	range_tree_walk(rt, range_tree_add, rtsync);
 	mutex_exit(&vd->vdev_dtl_lock);
 
 	space_map_truncate(vd->vdev_dtl_sm, zfs_vdev_dtl_sm_blksz, tx);
 	space_map_write(vd->vdev_dtl_sm, rtsync, SM_ALLOC, SM_NO_VDEVID, tx);
 	range_tree_vacate(rtsync, NULL, NULL);
 
 	range_tree_destroy(rtsync);
 
 	/*
 	 * If the object for the space map has changed then dirty
 	 * the top level so that we update the config.
 	 */
 	if (object != space_map_object(vd->vdev_dtl_sm)) {
 		vdev_dbgmsg(vd, "txg %llu, spa %s, DTL old object %llu, "
 		    "new object %llu", (u_longlong_t)txg, spa_name(spa),
 		    (u_longlong_t)object,
 		    (u_longlong_t)space_map_object(vd->vdev_dtl_sm));
 		vdev_config_dirty(vd->vdev_top);
 	}
 
 	dmu_tx_commit(tx);
 }
 
 /*
  * 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, B_FALSE);
 	required = !vdev_dtl_empty(tvd, DTL_OUTAGE);
 	vd->vdev_cant_read = cant_read;
 	vdev_dtl_reassess(tvd, 0, 0, B_FALSE, B_FALSE);
 
 	if (!required && zio_injection_enabled) {
 		required = !!zio_handle_device_injection(vd, NULL,
 		    SET_ERROR(ECHILD));
 	}
 
 	return (required);
 }
 
 /*
  * 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 (!range_tree_is_empty(vd->vdev_dtl[DTL_MISSING]) &&
 		    vdev_writeable(vd)) {
 
 			thismin = vdev_dtl_min(vd);
 			thismax = vdev_dtl_max(vd);
 			needed = B_TRUE;
 		}
 		mutex_exit(&vd->vdev_dtl_lock);
 	} else {
 		for (int 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);
 }
 
 /*
  * Gets the checkpoint space map object from the vdev's ZAP.  On success sm_obj
  * will contain either the checkpoint spacemap object or zero if none exists.
  * All other errors are returned to the caller.
  */
 int
 vdev_checkpoint_sm_object(vdev_t *vd, uint64_t *sm_obj)
 {
 	ASSERT0(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER));
 
 	if (vd->vdev_top_zap == 0) {
 		*sm_obj = 0;
 		return (0);
 	}
 
 	int error = zap_lookup(spa_meta_objset(vd->vdev_spa), vd->vdev_top_zap,
 	    VDEV_TOP_ZAP_POOL_CHECKPOINT_SM, sizeof (uint64_t), 1, sm_obj);
 	if (error == ENOENT) {
 		*sm_obj = 0;
 		error = 0;
 	}
 
 	return (error);
 }
 
 int
 vdev_load(vdev_t *vd)
 {
 	int children = vd->vdev_children;
 	int error = 0;
 	taskq_t *tq = NULL;
 
 	/*
 	 * It's only worthwhile to use the taskq for the root vdev, because the
 	 * slow part is metaslab_init, and that only happens for top-level
 	 * vdevs.
 	 */
 	if (vd->vdev_ops == &vdev_root_ops && vd->vdev_children > 0) {
 		tq = taskq_create("vdev_load", children, minclsyspri,
 		    children, children, TASKQ_PREPOPULATE);
 	}
 
 	/*
 	 * Recursively load all children.
 	 */
 	for (int c = 0; c < vd->vdev_children; c++) {
 		vdev_t *cvd = vd->vdev_child[c];
 
 		if (tq == NULL || vdev_uses_zvols(cvd)) {
 			cvd->vdev_load_error = vdev_load(cvd);
 		} else {
 			VERIFY(taskq_dispatch(tq, vdev_load_child,
 			    cvd, TQ_SLEEP) != TASKQID_INVALID);
 		}
 	}
 
 	if (tq != NULL) {
 		taskq_wait(tq);
 		taskq_destroy(tq);
 	}
 
 	for (int c = 0; c < vd->vdev_children; c++) {
 		int error = vd->vdev_child[c]->vdev_load_error;
 
 		if (error != 0)
 			return (error);
 	}
 
 	vdev_set_deflate_ratio(vd);
 
 	if (vd->vdev_ops == &vdev_raidz_ops) {
 		error = vdev_raidz_load(vd);
 		if (error != 0)
 			return (error);
 	}
 
 	/*
 	 * On spa_load path, grab the allocation bias from our zap
 	 */
 	if (vd == vd->vdev_top && vd->vdev_top_zap != 0) {
 		spa_t *spa = vd->vdev_spa;
 		char bias_str[64];
 
 		error = zap_lookup(spa->spa_meta_objset, vd->vdev_top_zap,
 		    VDEV_TOP_ZAP_ALLOCATION_BIAS, 1, sizeof (bias_str),
 		    bias_str);
 		if (error == 0) {
 			ASSERT(vd->vdev_alloc_bias == VDEV_BIAS_NONE);
 			vd->vdev_alloc_bias = vdev_derive_alloc_bias(bias_str);
 		} else if (error != ENOENT) {
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_CORRUPT_DATA);
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(top_zap=%llu) "
 			    "failed [error=%d]",
 			    (u_longlong_t)vd->vdev_top_zap, error);
 			return (error);
 		}
 	}
 
 	if (vd == vd->vdev_top && vd->vdev_top_zap != 0) {
 		spa_t *spa = vd->vdev_spa;
 		uint64_t failfast;
 
 		error = zap_lookup(spa->spa_meta_objset, vd->vdev_top_zap,
 		    vdev_prop_to_name(VDEV_PROP_FAILFAST), sizeof (failfast),
 		    1, &failfast);
 		if (error == 0) {
 			vd->vdev_failfast = failfast & 1;
 		} else if (error == ENOENT) {
 			vd->vdev_failfast = vdev_prop_default_numeric(
 			    VDEV_PROP_FAILFAST);
 		} else {
 			vdev_dbgmsg(vd,
 			    "vdev_load: zap_lookup(top_zap=%llu) "
 			    "failed [error=%d]",
 			    (u_longlong_t)vd->vdev_top_zap, error);
 		}
 	}
 
 	/*
 	 * Load any rebuild state from the top-level vdev zap.
 	 */
 	if (vd == vd->vdev_top && vd->vdev_top_zap != 0) {
 		error = vdev_rebuild_load(vd);
 		if (error && error != ENOTSUP) {
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_CORRUPT_DATA);
 			vdev_dbgmsg(vd, "vdev_load: vdev_rebuild_load "
 			    "failed [error=%d]", error);
 			return (error);
 		}
 	}
 
 	if (vd->vdev_top_zap != 0 || vd->vdev_leaf_zap != 0) {
 		uint64_t zapobj;
 
 		if (vd->vdev_top_zap != 0)
 			zapobj = vd->vdev_top_zap;
 		else
 			zapobj = vd->vdev_leaf_zap;
 
 		error = vdev_prop_get_int(vd, VDEV_PROP_CHECKSUM_N,
 		    &vd->vdev_checksum_n);
 		if (error && error != ENOENT)
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
 			    "failed [error=%d]", (u_longlong_t)zapobj, error);
 
 		error = vdev_prop_get_int(vd, VDEV_PROP_CHECKSUM_T,
 		    &vd->vdev_checksum_t);
 		if (error && error != ENOENT)
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
 			    "failed [error=%d]", (u_longlong_t)zapobj, error);
 
 		error = vdev_prop_get_int(vd, VDEV_PROP_IO_N,
 		    &vd->vdev_io_n);
 		if (error && error != ENOENT)
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
 			    "failed [error=%d]", (u_longlong_t)zapobj, error);
 
 		error = vdev_prop_get_int(vd, VDEV_PROP_IO_T,
 		    &vd->vdev_io_t);
 		if (error && error != ENOENT)
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
 			    "failed [error=%d]", (u_longlong_t)zapobj, error);
 
 		error = vdev_prop_get_int(vd, VDEV_PROP_SLOW_IO_N,
 		    &vd->vdev_slow_io_n);
 		if (error && error != ENOENT)
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
 			    "failed [error=%d]", (u_longlong_t)zapobj, error);
 
 		error = vdev_prop_get_int(vd, VDEV_PROP_SLOW_IO_T,
 		    &vd->vdev_slow_io_t);
 		if (error && error != ENOENT)
 			vdev_dbgmsg(vd, "vdev_load: zap_lookup(zap=%llu) "
 			    "failed [error=%d]", (u_longlong_t)zapobj, error);
 	}
 
 	/*
 	 * If this is a top-level vdev, initialize its metaslabs.
 	 */
 	if (vd == vd->vdev_top && vdev_is_concrete(vd)) {
 		vdev_metaslab_group_create(vd);
 
 		if (vd->vdev_ashift == 0 || vd->vdev_asize == 0) {
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_CORRUPT_DATA);
 			vdev_dbgmsg(vd, "vdev_load: invalid size. ashift=%llu, "
 			    "asize=%llu", (u_longlong_t)vd->vdev_ashift,
 			    (u_longlong_t)vd->vdev_asize);
 			return (SET_ERROR(ENXIO));
 		}
 
 		error = vdev_metaslab_init(vd, 0);
 		if (error != 0) {
 			vdev_dbgmsg(vd, "vdev_load: metaslab_init failed "
 			    "[error=%d]", error);
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_CORRUPT_DATA);
 			return (error);
 		}
 
 		uint64_t checkpoint_sm_obj;
 		error = vdev_checkpoint_sm_object(vd, &checkpoint_sm_obj);
 		if (error == 0 && checkpoint_sm_obj != 0) {
 			objset_t *mos = spa_meta_objset(vd->vdev_spa);
 			ASSERT(vd->vdev_asize != 0);
 			ASSERT3P(vd->vdev_checkpoint_sm, ==, NULL);
 
 			error = space_map_open(&vd->vdev_checkpoint_sm,
 			    mos, checkpoint_sm_obj, 0, vd->vdev_asize,
 			    vd->vdev_ashift);
 			if (error != 0) {
 				vdev_dbgmsg(vd, "vdev_load: space_map_open "
 				    "failed for checkpoint spacemap (obj %llu) "
 				    "[error=%d]",
 				    (u_longlong_t)checkpoint_sm_obj, error);
 				return (error);
 			}
 			ASSERT3P(vd->vdev_checkpoint_sm, !=, NULL);
 
 			/*
 			 * Since the checkpoint_sm contains free entries
 			 * exclusively we can use space_map_allocated() to
 			 * indicate the cumulative checkpointed space that
 			 * has been freed.
 			 */
 			vd->vdev_stat.vs_checkpoint_space =
 			    -space_map_allocated(vd->vdev_checkpoint_sm);
 			vd->vdev_spa->spa_checkpoint_info.sci_dspace +=
 			    vd->vdev_stat.vs_checkpoint_space;
 		} else if (error != 0) {
 			vdev_dbgmsg(vd, "vdev_load: failed to retrieve "
 			    "checkpoint space map object from vdev ZAP "
 			    "[error=%d]", error);
 			return (error);
 		}
 	}
 
 	/*
 	 * If this is a leaf vdev, load its DTL.
 	 */
 	if (vd->vdev_ops->vdev_op_leaf && (error = vdev_dtl_load(vd)) != 0) {
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 		    VDEV_AUX_CORRUPT_DATA);
 		vdev_dbgmsg(vd, "vdev_load: vdev_dtl_load failed "
 		    "[error=%d]", error);
 		return (error);
 	}
 
 	uint64_t obsolete_sm_object;
 	error = vdev_obsolete_sm_object(vd, &obsolete_sm_object);
 	if (error == 0 && obsolete_sm_object != 0) {
 		objset_t *mos = vd->vdev_spa->spa_meta_objset;
 		ASSERT(vd->vdev_asize != 0);
 		ASSERT3P(vd->vdev_obsolete_sm, ==, NULL);
 
 		if ((error = space_map_open(&vd->vdev_obsolete_sm, mos,
 		    obsolete_sm_object, 0, vd->vdev_asize, 0))) {
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
 			    VDEV_AUX_CORRUPT_DATA);
 			vdev_dbgmsg(vd, "vdev_load: space_map_open failed for "
 			    "obsolete spacemap (obj %llu) [error=%d]",
 			    (u_longlong_t)obsolete_sm_object, error);
 			return (error);
 		}
 	} else if (error != 0) {
 		vdev_dbgmsg(vd, "vdev_load: failed to retrieve obsolete "
 		    "space map object from vdev ZAP [error=%d]", error);
 		return (error);
 	}
 
 	return (0);
 }
 
 /*
  * 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, -1ULL)) == 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 ||
 	    !SPA_VERSION_IS_SUPPORTED(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);
 }
 
 static void
 vdev_destroy_ms_flush_data(vdev_t *vd, dmu_tx_t *tx)
 {
 	objset_t *mos = spa_meta_objset(vd->vdev_spa);
 
 	if (vd->vdev_top_zap == 0)
 		return;
 
 	uint64_t object = 0;
 	int err = zap_lookup(mos, vd->vdev_top_zap,
 	    VDEV_TOP_ZAP_MS_UNFLUSHED_PHYS_TXGS, sizeof (uint64_t), 1, &object);
 	if (err == ENOENT)
 		return;
 	VERIFY0(err);
 
 	VERIFY0(dmu_object_free(mos, object, tx));
 	VERIFY0(zap_remove(mos, vd->vdev_top_zap,
 	    VDEV_TOP_ZAP_MS_UNFLUSHED_PHYS_TXGS, tx));
 }
 
 /*
  * Free the objects used to store this vdev's spacemaps, and the array
  * that points to them.
  */
 void
 vdev_destroy_spacemaps(vdev_t *vd, dmu_tx_t *tx)
 {
 	if (vd->vdev_ms_array == 0)
 		return;
 
 	objset_t *mos = vd->vdev_spa->spa_meta_objset;
 	uint64_t array_count = vd->vdev_asize >> vd->vdev_ms_shift;
 	size_t array_bytes = array_count * sizeof (uint64_t);
 	uint64_t *smobj_array = kmem_alloc(array_bytes, KM_SLEEP);
 	VERIFY0(dmu_read(mos, vd->vdev_ms_array, 0,
 	    array_bytes, smobj_array, 0));
 
 	for (uint64_t i = 0; i < array_count; i++) {
 		uint64_t smobj = smobj_array[i];
 		if (smobj == 0)
 			continue;
 
 		space_map_free_obj(mos, smobj, tx);
 	}
 
 	kmem_free(smobj_array, array_bytes);
 	VERIFY0(dmu_object_free(mos, vd->vdev_ms_array, tx));
 	vdev_destroy_ms_flush_data(vd, tx);
 	vd->vdev_ms_array = 0;
 }
 
 static void
 vdev_remove_empty_log(vdev_t *vd, uint64_t txg)
 {
 	spa_t *spa = vd->vdev_spa;
 
 	ASSERT(vd->vdev_islog);
 	ASSERT(vd == vd->vdev_top);
 	ASSERT3U(txg, ==, spa_syncing_txg(spa));
 
 	dmu_tx_t *tx = dmu_tx_create_assigned(spa_get_dsl(spa), txg);
 
 	vdev_destroy_spacemaps(vd, tx);
 	if (vd->vdev_top_zap != 0) {
 		vdev_destroy_unlink_zap(vd, vd->vdev_top_zap, tx);
 		vd->vdev_top_zap = 0;
 	}
 
 	dmu_tx_commit(tx);
 }
 
 void
 vdev_sync_done(vdev_t *vd, uint64_t txg)
 {
 	metaslab_t *msp;
 	boolean_t reassess = !txg_list_empty(&vd->vdev_ms_list, TXG_CLEAN(txg));
 
 	ASSERT(vdev_is_concrete(vd));
 
 	while ((msp = txg_list_remove(&vd->vdev_ms_list, TXG_CLEAN(txg)))
 	    != NULL)
 		metaslab_sync_done(msp, txg);
 
 	if (reassess) {
 		metaslab_sync_reassess(vd->vdev_mg);
 		if (vd->vdev_log_mg != NULL)
 			metaslab_sync_reassess(vd->vdev_log_mg);
 	}
 }
 
 void
 vdev_sync(vdev_t *vd, uint64_t txg)
 {
 	spa_t *spa = vd->vdev_spa;
 	vdev_t *lvd;
 	metaslab_t *msp;
 
 	ASSERT3U(txg, ==, spa->spa_syncing_txg);
 	dmu_tx_t *tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
 	if (range_tree_space(vd->vdev_obsolete_segments) > 0) {
 		ASSERT(vd->vdev_removing ||
 		    vd->vdev_ops == &vdev_indirect_ops);
 
 		vdev_indirect_sync_obsolete(vd, tx);
 
 		/*
 		 * If the vdev is indirect, it can't have dirty
 		 * metaslabs or DTLs.
 		 */
 		if (vd->vdev_ops == &vdev_indirect_ops) {
 			ASSERT(txg_list_empty(&vd->vdev_ms_list, txg));
 			ASSERT(txg_list_empty(&vd->vdev_dtl_list, txg));
 			dmu_tx_commit(tx);
 			return;
 		}
 	}
 
 	ASSERT(vdev_is_concrete(vd));
 
 	if (vd->vdev_ms_array == 0 && vd->vdev_ms_shift != 0 &&
 	    !vd->vdev_removing) {
 		ASSERT(vd == vd->vdev_top);
 		ASSERT0(vd->vdev_indirect_config.vic_mapping_object);
 		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);
 	}
 
 	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);
 
 	/*
 	 * If this is an empty log device being removed, destroy the
 	 * metadata associated with it.
 	 */
 	if (vd->vdev_islog && vd->vdev_stat.vs_alloc == 0 && vd->vdev_removing)
 		vdev_remove_empty_log(vd, txg);
 
 	(void) txg_list_add(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg));
 	dmu_tx_commit(tx);
 }
 
 /*
  * Return the amount of space that should be (or was) allocated for the given
  * psize (compressed block size) in the given TXG. Note that for expanded
  * RAIDZ vdevs, the size allocated for older BP's may be larger. See
  * vdev_raidz_asize().
  */
 uint64_t
 vdev_psize_to_asize_txg(vdev_t *vd, uint64_t psize, uint64_t txg)
 {
 	return (vd->vdev_ops->vdev_op_asize(vd, psize, txg));
 }
 
 uint64_t
 vdev_psize_to_asize(vdev_t *vd, uint64_t psize)
 {
 	return (vdev_psize_to_asize_txg(vd, psize, 0));
 }
 
 /*
  * 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_aux_t aux)
 {
 	vdev_t *vd, *tvd;
 
 	spa_vdev_state_enter(spa, SCL_NONE);
 
 	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
 
 	if (!vd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
 
 	tvd = vd->vdev_top;
 
 	/*
 	 * If user did a 'zpool offline -f' then make the fault persist across
 	 * reboots.
 	 */
 	if (aux == VDEV_AUX_EXTERNAL_PERSIST) {
 		/*
 		 * There are two kinds of forced faults: temporary and
 		 * persistent.  Temporary faults go away at pool import, while
 		 * persistent faults stay set.  Both types of faults can be
 		 * cleared with a zpool clear.
 		 *
 		 * We tell if a vdev is persistently faulted by looking at the
 		 * ZPOOL_CONFIG_AUX_STATE nvpair.  If it's set to "external" at
 		 * import then it's a persistent fault.  Otherwise, it's
 		 * temporary.  We get ZPOOL_CONFIG_AUX_STATE set to "external"
 		 * by setting vd.vdev_stat.vs_aux to VDEV_AUX_EXTERNAL.  This
 		 * tells vdev_config_generate() (which gets run later) to set
 		 * ZPOOL_CONFIG_AUX_STATE to "external" in the nvlist.
 		 */
 		vd->vdev_stat.vs_aux = VDEV_AUX_EXTERNAL;
 		vd->vdev_tmpoffline = B_FALSE;
 		aux = VDEV_AUX_EXTERNAL;
 	} else {
 		vd->vdev_tmpoffline = B_TRUE;
 	}
 
 	/*
 	 * We don't directly use the aux state here, but if we do a
 	 * vdev_reopen(), we need this value to be present to remember why we
 	 * were faulted.
 	 */
 	vd->vdev_label_aux = aux;
 
 	/*
 	 * Faulted state takes precedence over degraded.
 	 */
 	vd->vdev_delayed_close = B_FALSE;
 	vd->vdev_faulted = 1ULL;
 	vd->vdev_degraded = 0ULL;
 	vdev_set_state(vd, B_FALSE, VDEV_STATE_FAULTED, aux);
 
 	/*
 	 * If this device has the only valid copy of the data, then
 	 * back off and simply mark the vdev as degraded instead.
 	 */
 	if (!tvd->vdev_islog && vd->vdev_aux == NULL && vdev_dtl_required(vd)) {
 		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(tvd);
 
 		if (vdev_readable(vd))
 			vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, aux);
 	}
 
 	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_aux_t aux)
 {
 	vdev_t *vd;
 
 	spa_vdev_state_enter(spa, SCL_NONE);
 
 	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
 
 	if (!vd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(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,
 		    aux);
 
 	return (spa_vdev_state_exit(spa, vd, 0));
 }
 
 int
 vdev_remove_wanted(spa_t *spa, uint64_t guid)
 {
 	vdev_t *vd;
 
 	spa_vdev_state_enter(spa, SCL_NONE);
 
 	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
 
 	/*
 	 * If the vdev is already removed, or expanding which can trigger
 	 * repartition add/remove events, then don't do anything.
 	 */
 	if (vd->vdev_removed || vd->vdev_expanding)
 		return (spa_vdev_state_exit(spa, NULL, 0));
 
 	/*
 	 * Confirm the vdev has been removed, otherwise don't do anything.
 	 */
 	if (vd->vdev_ops->vdev_op_leaf && !zio_wait(vdev_probe(vd, NULL)))
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(EEXIST)));
 
 	vd->vdev_remove_wanted = B_TRUE;
 	spa_async_request(spa, SPA_ASYNC_REMOVE);
 
 	return (spa_vdev_state_exit(spa, vd, 0));
 }
 
 
 /*
  * Online the given vdev.
  *
  * If 'ZFS_ONLINE_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, *tvd, *pvd, *rvd = spa->spa_root_vdev;
 	boolean_t wasoffline;
 	vdev_state_t oldstate;
 
 	spa_vdev_state_enter(spa, SCL_NONE);
 
 	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
 
 	wasoffline = (vd->vdev_offline || vd->vdev_tmpoffline);
 	oldstate = vd->vdev_state;
 
 	tvd = vd->vdev_top;
 	vd->vdev_offline = B_FALSE;
 	vd->vdev_tmpoffline = B_FALSE;
 	vd->vdev_checkremove = !!(flags & ZFS_ONLINE_CHECKREMOVE);
 	vd->vdev_forcefault = !!(flags & ZFS_ONLINE_FORCEFAULT);
 
 	/* XXX - L2ARC 1.0 does not support expansion */
 	if (!vd->vdev_aux) {
 		for (pvd = vd; pvd != rvd; pvd = pvd->vdev_parent)
 			pvd->vdev_expanding = !!((flags & ZFS_ONLINE_EXPAND) ||
 			    spa->spa_autoexpand);
 		vd->vdev_expansion_time = gethrestime_sec();
 	}
 
 	vdev_reopen(tvd);
 	vd->vdev_checkremove = vd->vdev_forcefault = B_FALSE;
 
 	if (!vd->vdev_aux) {
 		for (pvd = vd; pvd != rvd; pvd = pvd->vdev_parent)
 			pvd->vdev_expanding = 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;
 
 	if ((flags & ZFS_ONLINE_EXPAND) || spa->spa_autoexpand) {
 
 		/* XXX - L2ARC 1.0 does not support expansion */
 		if (vd->vdev_aux)
 			return (spa_vdev_state_exit(spa, vd, ENOTSUP));
 		spa->spa_ccw_fail_time = 0;
 		spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
 	}
 
 	/* Restart initializing if necessary */
 	mutex_enter(&vd->vdev_initialize_lock);
 	if (vdev_writeable(vd) &&
 	    vd->vdev_initialize_thread == NULL &&
 	    vd->vdev_initialize_state == VDEV_INITIALIZE_ACTIVE) {
 		(void) vdev_initialize(vd);
 	}
 	mutex_exit(&vd->vdev_initialize_lock);
 
 	/*
 	 * Restart trimming if necessary. We do not restart trimming for cache
 	 * devices here. This is triggered by l2arc_rebuild_vdev()
 	 * asynchronously for the whole device or in l2arc_evict() as it evicts
 	 * space for upcoming writes.
 	 */
 	mutex_enter(&vd->vdev_trim_lock);
 	if (vdev_writeable(vd) && !vd->vdev_isl2cache &&
 	    vd->vdev_trim_thread == NULL &&
 	    vd->vdev_trim_state == VDEV_TRIM_ACTIVE) {
 		(void) vdev_trim(vd, vd->vdev_trim_rate, vd->vdev_trim_partial,
 		    vd->vdev_trim_secure);
 	}
 	mutex_exit(&vd->vdev_trim_lock);
 
 	if (wasoffline ||
 	    (oldstate < VDEV_STATE_DEGRADED &&
 	    vd->vdev_state >= VDEV_STATE_DEGRADED)) {
 		spa_event_notify(spa, vd, NULL, ESC_ZFS_VDEV_ONLINE);
 
 		/*
 		 * Asynchronously detach spare vdev if resilver or
 		 * rebuild is not required
 		 */
 		if (vd->vdev_unspare &&
 		    !dsl_scan_resilvering(spa->spa_dsl_pool) &&
 		    !dsl_scan_resilver_scheduled(spa->spa_dsl_pool) &&
 		    !vdev_rebuild_active(tvd))
 			spa_async_request(spa, SPA_ASYNC_DETACH_SPARE);
 	}
 	return (spa_vdev_state_exit(spa, vd, 0));
 }
 
 static int
 vdev_offline_locked(spa_t *spa, uint64_t guid, uint64_t flags)
 {
 	vdev_t *vd, *tvd;
 	int error = 0;
 	uint64_t generation;
 	metaslab_group_t *mg;
 
 top:
 	spa_vdev_state_enter(spa, SCL_ALLOC);
 
 	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENODEV)));
 
 	if (!vd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
 
 	if (vd->vdev_ops == &vdev_draid_spare_ops)
 		return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
 
 	tvd = vd->vdev_top;
 	mg = tvd->vdev_mg;
 	generation = spa->spa_config_generation + 1;
 
 	/*
 	 * If the device isn't already offline, try to offline it.
 	 */
 	if (!vd->vdev_offline) {
 		/*
 		 * If this device has the only valid copy of some data,
 		 * don't allow it to be offlined. Log devices are always
 		 * expendable.
 		 */
 		if (!tvd->vdev_islog && vd->vdev_aux == NULL &&
 		    vdev_dtl_required(vd))
 			return (spa_vdev_state_exit(spa, NULL,
 			    SET_ERROR(EBUSY)));
 
 		/*
 		 * If the top-level is a slog and it has had allocations
 		 * then proceed.  We check that the vdev's metaslab group
 		 * is not NULL since it's possible that we may have just
 		 * added this vdev but not yet initialized its metaslabs.
 		 */
 		if (tvd->vdev_islog && mg != NULL) {
 			/*
 			 * Prevent any future allocations.
 			 */
 			ASSERT3P(tvd->vdev_log_mg, ==, NULL);
 			metaslab_group_passivate(mg);
 			(void) spa_vdev_state_exit(spa, vd, 0);
 
 			error = spa_reset_logs(spa);
 
 			/*
 			 * If the log device was successfully reset but has
 			 * checkpointed data, do not offline it.
 			 */
 			if (error == 0 &&
 			    tvd->vdev_checkpoint_sm != NULL) {
 				ASSERT3U(space_map_allocated(
 				    tvd->vdev_checkpoint_sm), !=, 0);
 				error = ZFS_ERR_CHECKPOINT_EXISTS;
 			}
 
 			spa_vdev_state_enter(spa, SCL_ALLOC);
 
 			/*
 			 * Check to see if the config has changed.
 			 */
 			if (error || generation != spa->spa_config_generation) {
 				metaslab_group_activate(mg);
 				if (error)
 					return (spa_vdev_state_exit(spa,
 					    vd, error));
 				(void) spa_vdev_state_exit(spa, vd, 0);
 				goto top;
 			}
 			ASSERT0(tvd->vdev_stat.vs_alloc);
 		}
 
 		/*
 		 * Offline this device and reopen its top-level vdev.
 		 * If the top-level vdev is a log device then just offline
 		 * it. Otherwise, if this action results in the top-level
 		 * vdev becoming unusable, undo it and fail the request.
 		 */
 		vd->vdev_offline = B_TRUE;
 		vdev_reopen(tvd);
 
 		if (!tvd->vdev_islog && vd->vdev_aux == NULL &&
 		    vdev_is_dead(tvd)) {
 			vd->vdev_offline = B_FALSE;
 			vdev_reopen(tvd);
 			return (spa_vdev_state_exit(spa, NULL,
 			    SET_ERROR(EBUSY)));
 		}
 
 		/*
 		 * Add the device back into the metaslab rotor so that
 		 * once we online the device it's open for business.
 		 */
 		if (tvd->vdev_islog && mg != NULL)
 			metaslab_group_activate(mg);
 	}
 
 	vd->vdev_tmpoffline = !!(flags & ZFS_OFFLINE_TEMPORARY);
 
 	return (spa_vdev_state_exit(spa, vd, 0));
 }
 
 int
 vdev_offline(spa_t *spa, uint64_t guid, uint64_t flags)
 {
 	int error;
 
 	mutex_enter(&spa->spa_vdev_top_lock);
 	error = vdev_offline_locked(spa, guid, flags);
 	mutex_exit(&spa->spa_vdev_top_lock);
 
 	return (error);
 }
 
 /*
  * 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;
 	vd->vdev_stat.vs_slow_ios = 0;
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_clear(spa, vd->vdev_child[c]);
 
 	/*
 	 * It makes no sense to "clear" an indirect  or removed vdev.
 	 */
 	if (!vdev_is_concrete(vd) || vd->vdev_removed)
 		return;
 
 	/*
 	 * 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)) {
 		/*
 		 * When reopening in response to a clear event, it may be due to
 		 * a fmadm repair request.  In this case, if the device is
 		 * still broken, we want to still post the ereport again.
 		 */
 		vd->vdev_forcefault = B_TRUE;
 
 		vd->vdev_faulted = vd->vdev_degraded = 0ULL;
 		vd->vdev_cant_read = B_FALSE;
 		vd->vdev_cant_write = B_FALSE;
 		vd->vdev_stat.vs_aux = 0;
 
 		vdev_reopen(vd == rvd ? rvd : vd->vdev_top);
 
 		vd->vdev_forcefault = B_FALSE;
 
 		if (vd != rvd && vdev_writeable(vd->vdev_top))
 			vdev_state_dirty(vd->vdev_top);
 
 		/* If a resilver isn't required, check if vdevs can be culled */
 		if (vd->vdev_aux == NULL && !vdev_is_dead(vd) &&
 		    !dsl_scan_resilvering(spa->spa_dsl_pool) &&
 		    !dsl_scan_resilver_scheduled(spa->spa_dsl_pool))
 			spa_async_request(spa, SPA_ASYNC_RESILVER_DONE);
 
 		spa_event_notify(spa, vd, NULL, ESC_ZFS_VDEV_CLEAR);
 	}
 
 	/*
 	 * When clearing a FMA-diagnosed fault, we always want to
 	 * unspare the device, as we assume that the original spare was
 	 * done in response to the FMA fault.
 	 */
 	if (!vdev_is_dead(vd) && vd->vdev_parent != NULL &&
 	    vd->vdev_parent->vdev_ops == &vdev_spare_ops &&
 	    vd->vdev_parent->vdev_child[0] == vd)
 		vd->vdev_unspare = B_TRUE;
 
 	/* Clear recent error events cache (i.e. duplicate events tracking) */
 	zfs_ereport_clear(spa, vd);
 }
 
 boolean_t
 vdev_is_dead(vdev_t *vd)
 {
 	/*
 	 * Holes and missing devices are always considered "dead".
 	 * This simplifies the code since we don't have to check for
 	 * these types of devices in the various code paths.
 	 * Instead we rely on the fact that we skip over dead devices
 	 * before issuing I/O to them.
 	 */
 	return (vd->vdev_state < VDEV_STATE_DEGRADED ||
 	    vd->vdev_ops == &vdev_hole_ops ||
 	    vd->vdev_ops == &vdev_missing_ops);
 }
 
 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 &&
 	    vdev_is_concrete(vd));
 }
 
 boolean_t
 vdev_allocatable(vdev_t *vd)
 {
 	uint64_t state = vd->vdev_state;
 
 	/*
 	 * 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.  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 (!(state < VDEV_STATE_DEGRADED && state != VDEV_STATE_CLOSED) &&
 	    !vd->vdev_cant_write && vdev_is_concrete(vd) &&
 	    vd->vdev_mg->mg_initialized);
 }
 
 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);
 }
 
 static void
 vdev_get_child_stat(vdev_t *cvd, vdev_stat_t *vs, vdev_stat_t *cvs)
 {
 	/*
 	 * Exclude the dRAID spare when aggregating to avoid double counting
 	 * the ops and bytes.  These IOs are counted by the physical leaves.
 	 */
 	if (cvd->vdev_ops == &vdev_draid_spare_ops)
 		return;
 
 	for (int t = 0; t < VS_ZIO_TYPES; t++) {
 		vs->vs_ops[t] += cvs->vs_ops[t];
 		vs->vs_bytes[t] += cvs->vs_bytes[t];
 	}
 
 	cvs->vs_scan_removing = cvd->vdev_removing;
 }
 
 /*
  * Get extended stats
  */
 static void
 vdev_get_child_stat_ex(vdev_t *cvd, vdev_stat_ex_t *vsx, vdev_stat_ex_t *cvsx)
 {
 	(void) cvd;
 
 	int t, b;
 	for (t = 0; t < ZIO_TYPES; t++) {
 		for (b = 0; b < ARRAY_SIZE(vsx->vsx_disk_histo[0]); b++)
 			vsx->vsx_disk_histo[t][b] += cvsx->vsx_disk_histo[t][b];
 
 		for (b = 0; b < ARRAY_SIZE(vsx->vsx_total_histo[0]); b++) {
 			vsx->vsx_total_histo[t][b] +=
 			    cvsx->vsx_total_histo[t][b];
 		}
 	}
 
 	for (t = 0; t < ZIO_PRIORITY_NUM_QUEUEABLE; t++) {
 		for (b = 0; b < ARRAY_SIZE(vsx->vsx_queue_histo[0]); b++) {
 			vsx->vsx_queue_histo[t][b] +=
 			    cvsx->vsx_queue_histo[t][b];
 		}
 		vsx->vsx_active_queue[t] += cvsx->vsx_active_queue[t];
 		vsx->vsx_pend_queue[t] += cvsx->vsx_pend_queue[t];
 
 		for (b = 0; b < ARRAY_SIZE(vsx->vsx_ind_histo[0]); b++)
 			vsx->vsx_ind_histo[t][b] += cvsx->vsx_ind_histo[t][b];
 
 		for (b = 0; b < ARRAY_SIZE(vsx->vsx_agg_histo[0]); b++)
 			vsx->vsx_agg_histo[t][b] += cvsx->vsx_agg_histo[t][b];
 	}
 
 }
 
 boolean_t
 vdev_is_spacemap_addressable(vdev_t *vd)
 {
 	if (spa_feature_is_active(vd->vdev_spa, SPA_FEATURE_SPACEMAP_V2))
 		return (B_TRUE);
 
 	/*
 	 * If double-word space map entries are not enabled we assume
 	 * 47 bits of the space map entry are dedicated to the entry's
 	 * offset (see SM_OFFSET_BITS in space_map.h). We then use that
 	 * to calculate the maximum address that can be described by a
 	 * space map entry for the given device.
 	 */
 	uint64_t shift = vd->vdev_ashift + SM_OFFSET_BITS;
 
 	if (shift >= 63) /* detect potential overflow */
 		return (B_TRUE);
 
 	return (vd->vdev_asize < (1ULL << shift));
 }
 
 /*
  * Get statistics for the given vdev.
  */
 static void
 vdev_get_stats_ex_impl(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx)
 {
 	int t;
 	/*
 	 * 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->vdev_ops->vdev_op_leaf) {
 		if (vs) {
 			memset(vs->vs_ops, 0, sizeof (vs->vs_ops));
 			memset(vs->vs_bytes, 0, sizeof (vs->vs_bytes));
 		}
 		if (vsx)
 			memset(vsx, 0, sizeof (*vsx));
 
 		for (int c = 0; c < vd->vdev_children; c++) {
 			vdev_t *cvd = vd->vdev_child[c];
 			vdev_stat_t *cvs = &cvd->vdev_stat;
 			vdev_stat_ex_t *cvsx = &cvd->vdev_stat_ex;
 
 			vdev_get_stats_ex_impl(cvd, cvs, cvsx);
 			if (vs)
 				vdev_get_child_stat(cvd, vs, cvs);
 			if (vsx)
 				vdev_get_child_stat_ex(cvd, vsx, cvsx);
 		}
 	} else {
 		/*
 		 * We're a leaf.  Just copy our ZIO active queue stats in.  The
 		 * other leaf stats are updated in vdev_stat_update().
 		 */
 		if (!vsx)
 			return;
 
 		memcpy(vsx, &vd->vdev_stat_ex, sizeof (vd->vdev_stat_ex));
 
 		for (t = 0; t < ZIO_PRIORITY_NUM_QUEUEABLE; t++) {
 			vsx->vsx_active_queue[t] = vd->vdev_queue.vq_cactive[t];
 			vsx->vsx_pend_queue[t] = vdev_queue_class_length(vd, t);
 		}
 	}
 }
 
 void
 vdev_get_stats_ex(vdev_t *vd, vdev_stat_t *vs, vdev_stat_ex_t *vsx)
 {
 	vdev_t *tvd = vd->vdev_top;
 	mutex_enter(&vd->vdev_stat_lock);
 	if (vs) {
 		memcpy(vs, &vd->vdev_stat, sizeof (*vs));
 		vs->vs_timestamp = gethrtime() - vs->vs_timestamp;
 		vs->vs_state = vd->vdev_state;
 		vs->vs_rsize = vdev_get_min_asize(vd);
 
 		if (vd->vdev_ops->vdev_op_leaf) {
 			vs->vs_pspace = vd->vdev_psize;
 			vs->vs_rsize += VDEV_LABEL_START_SIZE +
 			    VDEV_LABEL_END_SIZE;
 			/*
 			 * Report initializing progress. Since we don't
 			 * have the initializing locks held, this is only
 			 * an estimate (although a fairly accurate one).
 			 */
 			vs->vs_initialize_bytes_done =
 			    vd->vdev_initialize_bytes_done;
 			vs->vs_initialize_bytes_est =
 			    vd->vdev_initialize_bytes_est;
 			vs->vs_initialize_state = vd->vdev_initialize_state;
 			vs->vs_initialize_action_time =
 			    vd->vdev_initialize_action_time;
 
 			/*
 			 * Report manual TRIM progress. Since we don't have
 			 * the manual TRIM locks held, this is only an
 			 * estimate (although fairly accurate one).
 			 */
 			vs->vs_trim_notsup = !vd->vdev_has_trim;
 			vs->vs_trim_bytes_done = vd->vdev_trim_bytes_done;
 			vs->vs_trim_bytes_est = vd->vdev_trim_bytes_est;
 			vs->vs_trim_state = vd->vdev_trim_state;
 			vs->vs_trim_action_time = vd->vdev_trim_action_time;
 
 			/* Set when there is a deferred resilver. */
 			vs->vs_resilver_deferred = vd->vdev_resilver_deferred;
 		}
 
 		/*
 		 * Report expandable space on top-level, non-auxiliary devices
 		 * only. The expandable space is reported in terms of metaslab
 		 * sized units since that determines how much space the pool
 		 * can expand.
 		 */
 		if (vd->vdev_aux == NULL && tvd != NULL) {
 			vs->vs_esize = P2ALIGN_TYPED(
 			    vd->vdev_max_asize - vd->vdev_asize,
 			    1ULL << tvd->vdev_ms_shift, uint64_t);
 		}
 
 		vs->vs_configured_ashift = vd->vdev_top != NULL
 		    ? vd->vdev_top->vdev_ashift : vd->vdev_ashift;
 		vs->vs_logical_ashift = vd->vdev_logical_ashift;
 		if (vd->vdev_physical_ashift <= ASHIFT_MAX)
 			vs->vs_physical_ashift = vd->vdev_physical_ashift;
 		else
 			vs->vs_physical_ashift = 0;
 
 		/*
 		 * Report fragmentation and rebuild progress for top-level,
 		 * non-auxiliary, concrete devices.
 		 */
 		if (vd->vdev_aux == NULL && vd == vd->vdev_top &&
 		    vdev_is_concrete(vd)) {
 			/*
 			 * The vdev fragmentation rating doesn't take into
 			 * account the embedded slog metaslab (vdev_log_mg).
 			 * Since it's only one metaslab, it would have a tiny
 			 * impact on the overall fragmentation.
 			 */
 			vs->vs_fragmentation = (vd->vdev_mg != NULL) ?
 			    vd->vdev_mg->mg_fragmentation : 0;
 		}
 		vs->vs_noalloc = MAX(vd->vdev_noalloc,
 		    tvd ? tvd->vdev_noalloc : 0);
 	}
 
 	vdev_get_stats_ex_impl(vd, vs, vsx);
 	mutex_exit(&vd->vdev_stat_lock);
 }
 
 void
 vdev_get_stats(vdev_t *vd, vdev_stat_t *vs)
 {
 	return (vdev_get_stats_ex(vd, vs, NULL));
 }
 
 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_scan_stat_init(vdev_t *vd)
 {
 	vdev_stat_t *vs = &vd->vdev_stat;
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		vdev_scan_stat_init(vd->vdev_child[c]);
 
 	mutex_enter(&vd->vdev_stat_lock);
 	vs->vs_scan_processed = 0;
 	mutex_exit(&vd->vdev_stat_lock);
 }
 
 void
 vdev_stat_update(zio_t *zio, uint64_t psize)
 {
 	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;
 /* Suppress ASAN false positive */
 #ifdef __SANITIZE_ADDRESS__
 	vdev_stat_t *vs = vd ? &vd->vdev_stat : NULL;
 	vdev_stat_ex_t *vsx = vd ? &vd->vdev_stat_ex : NULL;
 #else
 	vdev_stat_t *vs = &vd->vdev_stat;
 	vdev_stat_ex_t *vsx = &vd->vdev_stat_ex;
 #endif
 	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)
 			return;
 
 		mutex_enter(&vd->vdev_stat_lock);
 
 		if (flags & ZIO_FLAG_IO_REPAIR) {
 			/*
 			 * Repair is the result of a resilver issued by the
 			 * scan thread (spa_sync).
 			 */
 			if (flags & ZIO_FLAG_SCAN_THREAD) {
 				dsl_scan_t *scn = spa->spa_dsl_pool->dp_scan;
 				dsl_scan_phys_t *scn_phys = &scn->scn_phys;
 				uint64_t *processed = &scn_phys->scn_processed;
 
 				if (vd->vdev_ops->vdev_op_leaf)
 					atomic_add_64(processed, psize);
 				vs->vs_scan_processed += psize;
 			}
 
 			/*
 			 * Repair is the result of a rebuild issued by the
 			 * rebuild thread (vdev_rebuild_thread).  To avoid
 			 * double counting repaired bytes the virtual dRAID
 			 * spare vdev is excluded from the processed bytes.
 			 */
 			if (zio->io_priority == ZIO_PRIORITY_REBUILD) {
 				vdev_t *tvd = vd->vdev_top;
 				vdev_rebuild_t *vr = &tvd->vdev_rebuild_config;
 				vdev_rebuild_phys_t *vrp = &vr->vr_rebuild_phys;
 				uint64_t *rebuilt = &vrp->vrp_bytes_rebuilt;
 
 				if (vd->vdev_ops->vdev_op_leaf &&
 				    vd->vdev_ops != &vdev_draid_spare_ops) {
 					atomic_add_64(rebuilt, psize);
 				}
 				vs->vs_rebuild_processed += psize;
 			}
 
 			if (flags & ZIO_FLAG_SELF_HEAL)
 				vs->vs_self_healed += psize;
 		}
 
 		/*
 		 * The bytes/ops/histograms are recorded at the leaf level and
 		 * aggregated into the higher level vdevs in vdev_get_stats().
 		 */
 		if (vd->vdev_ops->vdev_op_leaf &&
 		    (zio->io_priority < ZIO_PRIORITY_NUM_QUEUEABLE)) {
 			zio_type_t vs_type = type;
 			zio_priority_t priority = zio->io_priority;
 
 			/*
 			 * TRIM ops and bytes are reported to user space as
 			 * ZIO_TYPE_FLUSH.  This is done to preserve the
 			 * vdev_stat_t structure layout for user space.
 			 */
 			if (type == ZIO_TYPE_TRIM)
 				vs_type = ZIO_TYPE_FLUSH;
 
 			/*
 			 * Solely for the purposes of 'zpool iostat -lqrw'
 			 * reporting use the priority to categorize the IO.
 			 * Only the following are reported to user space:
 			 *
 			 *   ZIO_PRIORITY_SYNC_READ,
 			 *   ZIO_PRIORITY_SYNC_WRITE,
 			 *   ZIO_PRIORITY_ASYNC_READ,
 			 *   ZIO_PRIORITY_ASYNC_WRITE,
 			 *   ZIO_PRIORITY_SCRUB,
 			 *   ZIO_PRIORITY_TRIM,
 			 *   ZIO_PRIORITY_REBUILD.
 			 */
 			if (priority == ZIO_PRIORITY_INITIALIZING) {
 				ASSERT3U(type, ==, ZIO_TYPE_WRITE);
 				priority = ZIO_PRIORITY_ASYNC_WRITE;
 			} else if (priority == ZIO_PRIORITY_REMOVAL) {
 				priority = ((type == ZIO_TYPE_WRITE) ?
 				    ZIO_PRIORITY_ASYNC_WRITE :
 				    ZIO_PRIORITY_ASYNC_READ);
 			}
 
 			vs->vs_ops[vs_type]++;
 			vs->vs_bytes[vs_type] += psize;
 
 			if (flags & ZIO_FLAG_DELEGATED) {
 				vsx->vsx_agg_histo[priority]
 				    [RQ_HISTO(zio->io_size)]++;
 			} else {
 				vsx->vsx_ind_histo[priority]
 				    [RQ_HISTO(zio->io_size)]++;
 			}
 
 			if (zio->io_delta && zio->io_delay) {
 				vsx->vsx_queue_histo[priority]
 				    [L_HISTO(zio->io_delta - zio->io_delay)]++;
 				vsx->vsx_disk_histo[type]
 				    [L_HISTO(zio->io_delay)]++;
 				vsx->vsx_total_histo[type]
 				    [L_HISTO(zio->io_delta)]++;
 			}
 		}
 
 		mutex_exit(&vd->vdev_stat_lock);
 		return;
 	}
 
 	if (flags & ZIO_FLAG_SPECULATIVE)
 		return;
 
 	/*
 	 * If this is an I/O error that is going to be retried, then ignore the
 	 * error.  Otherwise, the user may interpret B_FAILFAST I/O errors as
 	 * hard errors, when in reality they can happen for any number of
 	 * innocuous reasons (bus resets, MPxIO link failure, etc).
 	 */
 	if (zio->io_error == EIO &&
 	    !(zio->io_flags & ZIO_FLAG_IO_RETRY))
 		return;
 
 	/*
 	 * Intent logs writes won't propagate their error to the root
 	 * I/O so don't mark these types of failures as pool-level
 	 * errors.
 	 */
 	if (zio->io_vd == NULL && (zio->io_flags & ZIO_FLAG_DONT_PROPAGATE))
 		return;
 
 	if (type == ZIO_TYPE_WRITE && txg != 0 &&
 	    (!(flags & ZIO_FLAG_IO_REPAIR) ||
 	    (flags & ZIO_FLAG_SCAN_THREAD) ||
 	    spa->spa_claiming)) {
 		/*
 		 * This is either a normal write (not a repair), or it's
 		 * a repair induced by the scrub thread, or it's a repair
 		 * made by zil_claim() during spa_load() in the first txg.
 		 * 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_syncing_txg(spa).
 		 * In the zil_claim() case, we commit in spa_first_txg(spa).
 		 *
 		 * 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_SCAN_THREAD) {
 				ASSERT(flags & ZIO_FLAG_IO_REPAIR);
 				ASSERT(spa_sync_pass(spa) == 1);
 				vdev_dtl_dirty(vd, DTL_SCRUB, txg, 1);
 				commit_txg = spa_syncing_txg(spa);
 			} else if (spa->spa_claiming) {
 				ASSERT(flags & ZIO_FLAG_IO_REPAIR);
 				commit_txg = spa_first_txg(spa);
 			}
 			ASSERT(commit_txg >= spa_syncing_txg(spa));
 			if (vdev_dtl_contains(vd, DTL_MISSING, txg, 1))
 				return;
 			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);
 	}
 }
 
 int64_t
 vdev_deflated_space(vdev_t *vd, int64_t space)
 {
 	ASSERT((space & (SPA_MINBLOCKSIZE-1)) == 0);
 	ASSERT(vd->vdev_deflate_ratio != 0 || vd->vdev_isl2cache);
 
 	return ((space >> SPA_MINBLOCKSHIFT) * vd->vdev_deflate_ratio);
 }
 
 /*
  * Update the in-core space usage stats for this vdev, its metaslab class,
  * and the root vdev.
  */
 void
 vdev_space_update(vdev_t *vd, int64_t alloc_delta, int64_t defer_delta,
     int64_t space_delta)
 {
 	(void) defer_delta;
 	int64_t dspace_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
 	 * children's, thus not accurate enough for us.
 	 */
 	dspace_delta = vdev_deflated_space(vd, space_delta);
 
 	mutex_enter(&vd->vdev_stat_lock);
 	/* ensure we won't underflow */
 	if (alloc_delta < 0) {
 		ASSERT3U(vd->vdev_stat.vs_alloc, >=, -alloc_delta);
 	}
 
 	vd->vdev_stat.vs_alloc += alloc_delta;
 	vd->vdev_stat.vs_space += space_delta;
 	vd->vdev_stat.vs_dspace += dspace_delta;
 	mutex_exit(&vd->vdev_stat_lock);
 
 	/* every class but log contributes to root space stats */
 	if (vd->vdev_mg != NULL && !vd->vdev_islog) {
 		ASSERT(!vd->vdev_isl2cache);
 		mutex_enter(&rvd->vdev_stat_lock);
 		rvd->vdev_stat.vs_alloc += alloc_delta;
 		rvd->vdev_stat.vs_space += space_delta;
 		rvd->vdev_stat.vs_dspace += dspace_delta;
 		mutex_exit(&rvd->vdev_stat_lock);
 	}
 	/* Note: metaslab_class_space_update moved to metaslab_space_update */
 }
 
 /*
  * 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;
 
 	ASSERT(spa_writeable(spa));
 
 	/*
 	 * If this is an aux vdev (as with l2cache and spare 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;
 
 		if (nvlist_lookup_nvlist_array(sav->sav_config,
 		    ZPOOL_CONFIG_L2CACHE, &aux, &naux) != 0) {
 			VERIFY(nvlist_lookup_nvlist_array(sav->sav_config,
 			    ZPOOL_CONFIG_SPARES, &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, 0);
 
 		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) &&
 		    vdev_is_concrete(vd)) {
 			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(spa_writeable(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) &&
 	    vdev_is_concrete(vd))
 		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)
 {
 	spa_t *spa = vd->vdev_spa;
 	vdev_t *rvd = spa->spa_root_vdev;
 	int degraded = 0, faulted = 0;
 	int corrupted = 0;
 	vdev_t *child;
 
 	if (vd->vdev_children > 0) {
 		for (int c = 0; c < vd->vdev_children; c++) {
 			child = vd->vdev_child[c];
 
 			/*
 			 * Don't factor holes or indirect vdevs into the
 			 * decision.
 			 */
 			if (!vdev_is_concrete(child))
 				continue;
 
 			if (!vdev_readable(child) ||
 			    (!vdev_writeable(child) && spa_writeable(spa))) {
 				/*
 				 * 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) {
 		/*
 		 * Since vdev_offline() code path is already in an offline
 		 * state we can miss a statechange event to OFFLINE. Check
 		 * the previous state to catch this condition.
 		 */
 		if (vd->vdev_ops->vdev_op_leaf &&
 		    (state == VDEV_STATE_OFFLINE) &&
 		    (vd->vdev_prevstate >= VDEV_STATE_FAULTED)) {
 			/* post an offline state change */
 			zfs_post_state_change(spa, vd, vd->vdev_prevstate);
 		}
 		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 unless the device has requested
 	 * a delayed close (i.e. we're about to remove or fault the 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 (!vd->vdev_delayed_close && 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) {
 		vd->vdev_removed = B_TRUE;
 	} else if (state == VDEV_STATE_CANT_OPEN) {
 		/*
 		 * If we fail to open a vdev during an import or recovery, 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_load_state(spa) == SPA_LOAD_IMPORT ||
 		    spa_load_state(spa) == SPA_LOAD_RECOVER) &&
 		    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_BAD_ASHIFT:
 				class = FM_EREPORT_ZFS_DEVICE_BAD_ASHIFT;
 				break;
 			default:
 				class = FM_EREPORT_ZFS_DEVICE_UNKNOWN;
 			}
 
 			(void) zfs_ereport_post(class, spa, vd, NULL, NULL,
 			    save_state);
 		}
 
 		/* Erase any notion of persistent removed state */
 		vd->vdev_removed = B_FALSE;
 	} else {
 		vd->vdev_removed = B_FALSE;
 	}
 
 	/*
 	 * Notify ZED of any significant state-change on a leaf vdev.
 	 *
 	 */
 	if (vd->vdev_ops->vdev_op_leaf) {
 		/* preserve original state from a vdev_reopen() */
 		if ((vd->vdev_prevstate != VDEV_STATE_UNKNOWN) &&
 		    (vd->vdev_prevstate != vd->vdev_state) &&
 		    (save_state <= VDEV_STATE_CLOSED))
 			save_state = vd->vdev_prevstate;
 
 		/* filter out state change due to initial vdev_open */
 		if (save_state > VDEV_STATE_CLOSED)
 			zfs_post_state_change(spa, vd, save_state);
 	}
 
 	if (!isopen && vd->vdev_parent)
 		vdev_propagate_state(vd->vdev_parent);
 }
 
 boolean_t
 vdev_children_are_offline(vdev_t *vd)
 {
 	ASSERT(!vd->vdev_ops->vdev_op_leaf);
 
 	for (uint64_t i = 0; i < vd->vdev_children; i++) {
 		if (vd->vdev_child[i]->vdev_state != VDEV_STATE_OFFLINE)
 			return (B_FALSE);
 	}
 
 	return (B_TRUE);
 }
 
 /*
  * Check the vdev configuration to ensure that it's capable of supporting
  * a root pool. We do not support partial configuration.
  */
 boolean_t
 vdev_is_bootable(vdev_t *vd)
 {
 	if (!vd->vdev_ops->vdev_op_leaf) {
 		const char *vdev_type = vd->vdev_ops->vdev_op_type;
 
 		if (strcmp(vdev_type, VDEV_TYPE_MISSING) == 0)
 			return (B_FALSE);
 	}
 
 	for (int c = 0; c < vd->vdev_children; c++) {
 		if (!vdev_is_bootable(vd->vdev_child[c]))
 			return (B_FALSE);
 	}
 	return (B_TRUE);
 }
 
 boolean_t
 vdev_is_concrete(vdev_t *vd)
 {
 	vdev_ops_t *ops = vd->vdev_ops;
 	if (ops == &vdev_indirect_ops || ops == &vdev_hole_ops ||
 	    ops == &vdev_missing_ops || ops == &vdev_root_ops) {
 		return (B_FALSE);
 	} else {
 		return (B_TRUE);
 	}
 }
 
 /*
  * Determine if a log device has valid content.  If the vdev was
  * removed or faulted in the MOS config then we know that
  * the content on the log device has already been written to the pool.
  */
 boolean_t
 vdev_log_state_valid(vdev_t *vd)
 {
 	if (vd->vdev_ops->vdev_op_leaf && !vd->vdev_faulted &&
 	    !vd->vdev_removed)
 		return (B_TRUE);
 
 	for (int c = 0; c < vd->vdev_children; c++)
 		if (vdev_log_state_valid(vd->vdev_child[c]))
 			return (B_TRUE);
 
 	return (B_FALSE);
 }
 
 /*
  * Expand a vdev if possible.
  */
 void
 vdev_expand(vdev_t *vd, uint64_t txg)
 {
 	ASSERT(vd->vdev_top == vd);
 	ASSERT(spa_config_held(vd->vdev_spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 	ASSERT(vdev_is_concrete(vd));
 
 	vdev_set_deflate_ratio(vd);
 
 	if ((vd->vdev_spa->spa_raidz_expand == NULL ||
 	    vd->vdev_spa->spa_raidz_expand->vre_vdev_id != vd->vdev_id) &&
 	    (vd->vdev_asize >> vd->vdev_ms_shift) > vd->vdev_ms_count &&
 	    vdev_is_concrete(vd)) {
 		vdev_metaslab_group_create(vd);
 		VERIFY(vdev_metaslab_init(vd, txg) == 0);
 		vdev_config_dirty(vd);
 	}
 }
 
 /*
  * Split a vdev.
  */
 void
 vdev_split(vdev_t *vd)
 {
 	vdev_t *cvd, *pvd = vd->vdev_parent;
 
 	VERIFY3U(pvd->vdev_children, >, 1);
 
 	vdev_remove_child(pvd, vd);
 	vdev_compact_children(pvd);
 
 	ASSERT3P(pvd->vdev_child, !=, NULL);
 
 	cvd = pvd->vdev_child[0];
 	if (pvd->vdev_children == 1) {
 		vdev_remove_parent(cvd);
 		cvd->vdev_splitting = B_TRUE;
 	}
 	vdev_propagate_state(cvd);
 }
 
 void
 vdev_deadman(vdev_t *vd, const char *tag)
 {
 	for (int c = 0; c < vd->vdev_children; c++) {
 		vdev_t *cvd = vd->vdev_child[c];
 
 		vdev_deadman(cvd, tag);
 	}
 
 	if (vd->vdev_ops->vdev_op_leaf) {
 		vdev_queue_t *vq = &vd->vdev_queue;
 
 		mutex_enter(&vq->vq_lock);
 		if (vq->vq_active > 0) {
 			spa_t *spa = vd->vdev_spa;
 			zio_t *fio;
 			uint64_t delta;
 
 			zfs_dbgmsg("slow vdev: %s has %u active IOs",
 			    vd->vdev_path, vq->vq_active);
 
 			/*
 			 * Look at the head of all the pending queues,
 			 * if any I/O has been outstanding for longer than
 			 * the spa_deadman_synctime invoke the deadman logic.
 			 */
 			fio = list_head(&vq->vq_active_list);
 			delta = gethrtime() - fio->io_timestamp;
 			if (delta > spa_deadman_synctime(spa))
 				zio_deadman(fio, tag);
 		}
 		mutex_exit(&vq->vq_lock);
 	}
 }
 
 void
 vdev_defer_resilver(vdev_t *vd)
 {
 	ASSERT(vd->vdev_ops->vdev_op_leaf);
 
 	vd->vdev_resilver_deferred = B_TRUE;
 	vd->vdev_spa->spa_resilver_deferred = B_TRUE;
 }
 
 /*
  * Clears the resilver deferred flag on all leaf devs under vd. Returns
  * B_TRUE if we have devices that need to be resilvered and are available to
  * accept resilver I/Os.
  */
 boolean_t
 vdev_clear_resilver_deferred(vdev_t *vd, dmu_tx_t *tx)
 {
 	boolean_t resilver_needed = B_FALSE;
 	spa_t *spa = vd->vdev_spa;
 
 	for (int c = 0; c < vd->vdev_children; c++) {
 		vdev_t *cvd = vd->vdev_child[c];
 		resilver_needed |= vdev_clear_resilver_deferred(cvd, tx);
 	}
 
 	if (vd == spa->spa_root_vdev &&
 	    spa_feature_is_active(spa, SPA_FEATURE_RESILVER_DEFER)) {
 		spa_feature_decr(spa, SPA_FEATURE_RESILVER_DEFER, tx);
 		vdev_config_dirty(vd);
 		spa->spa_resilver_deferred = B_FALSE;
 		return (resilver_needed);
 	}
 
 	if (!vdev_is_concrete(vd) || vd->vdev_aux ||
 	    !vd->vdev_ops->vdev_op_leaf)
 		return (resilver_needed);
 
 	vd->vdev_resilver_deferred = B_FALSE;
 
 	return (!vdev_is_dead(vd) && !vd->vdev_offline &&
 	    vdev_resilver_needed(vd, NULL, NULL));
 }
 
 boolean_t
 vdev_xlate_is_empty(range_seg64_t *rs)
 {
 	return (rs->rs_start == rs->rs_end);
 }
 
 /*
  * Translate a logical range to the first contiguous physical range for the
  * specified vdev_t.  This function is initially called with a leaf vdev and
  * will walk each parent vdev until it reaches a top-level vdev. Once the
  * top-level is reached the physical range is initialized and the recursive
  * function begins to unwind. As it unwinds it calls the parent's vdev
  * specific translation function to do the real conversion.
  */
 void
 vdev_xlate(vdev_t *vd, const range_seg64_t *logical_rs,
     range_seg64_t *physical_rs, range_seg64_t *remain_rs)
 {
 	/*
 	 * Walk up the vdev tree
 	 */
 	if (vd != vd->vdev_top) {
 		vdev_xlate(vd->vdev_parent, logical_rs, physical_rs,
 		    remain_rs);
 	} else {
 		/*
 		 * We've reached the top-level vdev, initialize the physical
 		 * range to the logical range and set an empty remaining
 		 * range then start to unwind.
 		 */
 		physical_rs->rs_start = logical_rs->rs_start;
 		physical_rs->rs_end = logical_rs->rs_end;
 
 		remain_rs->rs_start = logical_rs->rs_start;
 		remain_rs->rs_end = logical_rs->rs_start;
 
 		return;
 	}
 
 	vdev_t *pvd = vd->vdev_parent;
 	ASSERT3P(pvd, !=, NULL);
 	ASSERT3P(pvd->vdev_ops->vdev_op_xlate, !=, NULL);
 
 	/*
 	 * As this recursive function unwinds, translate the logical
 	 * range into its physical and any remaining components by calling
 	 * the vdev specific translate function.
 	 */
 	range_seg64_t intermediate = { 0 };
 	pvd->vdev_ops->vdev_op_xlate(vd, physical_rs, &intermediate, remain_rs);
 
 	physical_rs->rs_start = intermediate.rs_start;
 	physical_rs->rs_end = intermediate.rs_end;
 }
 
 void
 vdev_xlate_walk(vdev_t *vd, const range_seg64_t *logical_rs,
     vdev_xlate_func_t *func, void *arg)
 {
 	range_seg64_t iter_rs = *logical_rs;
 	range_seg64_t physical_rs;
 	range_seg64_t remain_rs;
 
 	while (!vdev_xlate_is_empty(&iter_rs)) {
 
 		vdev_xlate(vd, &iter_rs, &physical_rs, &remain_rs);
 
 		/*
 		 * With raidz and dRAID, it's possible that the logical range
 		 * does not live on this leaf vdev. Only when there is a non-
 		 * zero physical size call the provided function.
 		 */
 		if (!vdev_xlate_is_empty(&physical_rs))
 			func(arg, &physical_rs);
 
 		iter_rs = remain_rs;
 	}
 }
 
 static char *
 vdev_name(vdev_t *vd, char *buf, int buflen)
 {
 	if (vd->vdev_path == NULL) {
 		if (strcmp(vd->vdev_ops->vdev_op_type, "root") == 0) {
 			strlcpy(buf, vd->vdev_spa->spa_name, buflen);
 		} else if (!vd->vdev_ops->vdev_op_leaf) {
 			snprintf(buf, buflen, "%s-%llu",
 			    vd->vdev_ops->vdev_op_type,
 			    (u_longlong_t)vd->vdev_id);
 		}
 	} else {
 		strlcpy(buf, vd->vdev_path, buflen);
 	}
 	return (buf);
 }
 
 /*
  * Look at the vdev tree and determine whether any devices are currently being
  * replaced.
  */
 boolean_t
 vdev_replace_in_progress(vdev_t *vdev)
 {
 	ASSERT(spa_config_held(vdev->vdev_spa, SCL_ALL, RW_READER) != 0);
 
 	if (vdev->vdev_ops == &vdev_replacing_ops)
 		return (B_TRUE);
 
 	/*
 	 * A 'spare' vdev indicates that we have a replace in progress, unless
 	 * it has exactly two children, and the second, the hot spare, has
 	 * finished being resilvered.
 	 */
 	if (vdev->vdev_ops == &vdev_spare_ops && (vdev->vdev_children > 2 ||
 	    !vdev_dtl_empty(vdev->vdev_child[1], DTL_MISSING)))
 		return (B_TRUE);
 
 	for (int i = 0; i < vdev->vdev_children; i++) {
 		if (vdev_replace_in_progress(vdev->vdev_child[i]))
 			return (B_TRUE);
 	}
 
 	return (B_FALSE);
 }
 
 /*
  * Add a (source=src, propname=propval) list to an nvlist.
  */
 static void
 vdev_prop_add_list(nvlist_t *nvl, const char *propname, const char *strval,
     uint64_t intval, zprop_source_t src)
 {
 	nvlist_t *propval;
 
 	propval = fnvlist_alloc();
 	fnvlist_add_uint64(propval, ZPROP_SOURCE, src);
 
 	if (strval != NULL)
 		fnvlist_add_string(propval, ZPROP_VALUE, strval);
 	else
 		fnvlist_add_uint64(propval, ZPROP_VALUE, intval);
 
 	fnvlist_add_nvlist(nvl, propname, propval);
 	nvlist_free(propval);
 }
 
 static void
 vdev_props_set_sync(void *arg, dmu_tx_t *tx)
 {
 	vdev_t *vd;
 	nvlist_t *nvp = arg;
 	spa_t *spa = dmu_tx_pool(tx)->dp_spa;
 	objset_t *mos = spa->spa_meta_objset;
 	nvpair_t *elem = NULL;
 	uint64_t vdev_guid;
 	uint64_t objid;
 	nvlist_t *nvprops;
 
 	vdev_guid = fnvlist_lookup_uint64(nvp, ZPOOL_VDEV_PROPS_SET_VDEV);
 	nvprops = fnvlist_lookup_nvlist(nvp, ZPOOL_VDEV_PROPS_SET_PROPS);
 	vd = spa_lookup_by_guid(spa, vdev_guid, B_TRUE);
 
 	/* this vdev could get removed while waiting for this sync task */
 	if (vd == NULL)
 		return;
 
 	/*
 	 * Set vdev property values in the vdev props mos object.
 	 */
 	if (vd->vdev_root_zap != 0) {
 		objid = vd->vdev_root_zap;
 	} else if (vd->vdev_top_zap != 0) {
 		objid = vd->vdev_top_zap;
 	} else if (vd->vdev_leaf_zap != 0) {
 		objid = vd->vdev_leaf_zap;
 	} else {
 		panic("unexpected vdev type");
 	}
 
 	mutex_enter(&spa->spa_props_lock);
 
 	while ((elem = nvlist_next_nvpair(nvprops, elem)) != NULL) {
 		uint64_t intval;
 		const char *strval;
 		vdev_prop_t prop;
 		const char *propname = nvpair_name(elem);
 		zprop_type_t proptype;
 
 		switch (prop = vdev_name_to_prop(propname)) {
 		case VDEV_PROP_USERPROP:
 			if (vdev_prop_user(propname)) {
 				strval = fnvpair_value_string(elem);
 				if (strlen(strval) == 0) {
 					/* remove the property if value == "" */
 					(void) zap_remove(mos, objid, propname,
 					    tx);
 				} else {
 					VERIFY0(zap_update(mos, objid, propname,
 					    1, strlen(strval) + 1, strval, tx));
 				}
 				spa_history_log_internal(spa, "vdev set", tx,
 				    "vdev_guid=%llu: %s=%s",
 				    (u_longlong_t)vdev_guid, nvpair_name(elem),
 				    strval);
 			}
 			break;
 		default:
 			/* normalize the property name */
 			propname = vdev_prop_to_name(prop);
 			proptype = vdev_prop_get_type(prop);
 
 			if (nvpair_type(elem) == DATA_TYPE_STRING) {
 				ASSERT(proptype == PROP_TYPE_STRING);
 				strval = fnvpair_value_string(elem);
 				VERIFY0(zap_update(mos, objid, propname,
 				    1, strlen(strval) + 1, strval, tx));
 				spa_history_log_internal(spa, "vdev set", tx,
 				    "vdev_guid=%llu: %s=%s",
 				    (u_longlong_t)vdev_guid, nvpair_name(elem),
 				    strval);
 			} else if (nvpair_type(elem) == DATA_TYPE_UINT64) {
 				intval = fnvpair_value_uint64(elem);
 
 				if (proptype == PROP_TYPE_INDEX) {
 					const char *unused;
 					VERIFY0(vdev_prop_index_to_string(
 					    prop, intval, &unused));
 				}
 				VERIFY0(zap_update(mos, objid, propname,
 				    sizeof (uint64_t), 1, &intval, tx));
 				spa_history_log_internal(spa, "vdev set", tx,
 				    "vdev_guid=%llu: %s=%lld",
 				    (u_longlong_t)vdev_guid,
 				    nvpair_name(elem), (longlong_t)intval);
 			} else {
 				panic("invalid vdev property type %u",
 				    nvpair_type(elem));
 			}
 		}
 
 	}
 
 	mutex_exit(&spa->spa_props_lock);
 }
 
 int
 vdev_prop_set(vdev_t *vd, nvlist_t *innvl, nvlist_t *outnvl)
 {
 	spa_t *spa = vd->vdev_spa;
 	nvpair_t *elem = NULL;
 	uint64_t vdev_guid;
 	nvlist_t *nvprops;
 	int error = 0;
 
 	ASSERT(vd != NULL);
 
 	/* Check that vdev has a zap we can use */
 	if (vd->vdev_root_zap == 0 &&
 	    vd->vdev_top_zap == 0 &&
 	    vd->vdev_leaf_zap == 0)
 		return (SET_ERROR(EINVAL));
 
 	if (nvlist_lookup_uint64(innvl, ZPOOL_VDEV_PROPS_SET_VDEV,
 	    &vdev_guid) != 0)
 		return (SET_ERROR(EINVAL));
 
 	if (nvlist_lookup_nvlist(innvl, ZPOOL_VDEV_PROPS_SET_PROPS,
 	    &nvprops) != 0)
 		return (SET_ERROR(EINVAL));
 
 	if ((vd = spa_lookup_by_guid(spa, vdev_guid, B_TRUE)) == NULL)
 		return (SET_ERROR(EINVAL));
 
 	while ((elem = nvlist_next_nvpair(nvprops, elem)) != NULL) {
 		const char *propname = nvpair_name(elem);
 		vdev_prop_t prop = vdev_name_to_prop(propname);
 		uint64_t intval = 0;
 		const char *strval = NULL;
 
 		if (prop == VDEV_PROP_USERPROP && !vdev_prop_user(propname)) {
 			error = EINVAL;
 			goto end;
 		}
 
 		if (vdev_prop_readonly(prop)) {
 			error = EROFS;
 			goto end;
 		}
 
 		/* Special Processing */
 		switch (prop) {
 		case VDEV_PROP_PATH:
 			if (vd->vdev_path == NULL) {
 				error = EROFS;
 				break;
 			}
 			if (nvpair_value_string(elem, &strval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			/* New path must start with /dev/ */
 			if (strncmp(strval, "/dev/", 5)) {
 				error = EINVAL;
 				break;
 			}
 			error = spa_vdev_setpath(spa, vdev_guid, strval);
 			break;
 		case VDEV_PROP_ALLOCATING:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			if (intval != vd->vdev_noalloc)
 				break;
 			if (intval == 0)
 				error = spa_vdev_noalloc(spa, vdev_guid);
 			else
 				error = spa_vdev_alloc(spa, vdev_guid);
 			break;
 		case VDEV_PROP_FAILFAST:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_failfast = intval & 1;
 			break;
 		case VDEV_PROP_CHECKSUM_N:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_checksum_n = intval;
 			break;
 		case VDEV_PROP_CHECKSUM_T:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_checksum_t = intval;
 			break;
 		case VDEV_PROP_IO_N:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_io_n = intval;
 			break;
 		case VDEV_PROP_IO_T:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_io_t = intval;
 			break;
 		case VDEV_PROP_SLOW_IO_N:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_slow_io_n = intval;
 			break;
 		case VDEV_PROP_SLOW_IO_T:
 			if (nvpair_value_uint64(elem, &intval) != 0) {
 				error = EINVAL;
 				break;
 			}
 			vd->vdev_slow_io_t = intval;
 			break;
 		default:
 			/* Most processing is done in vdev_props_set_sync */
 			break;
 		}
 end:
 		if (error != 0) {
 			intval = error;
 			vdev_prop_add_list(outnvl, propname, strval, intval, 0);
 			return (error);
 		}
 	}
 
 	return (dsl_sync_task(spa->spa_name, NULL, vdev_props_set_sync,
 	    innvl, 6, ZFS_SPACE_CHECK_EXTRA_RESERVED));
 }
 
 int
 vdev_prop_get(vdev_t *vd, nvlist_t *innvl, nvlist_t *outnvl)
 {
 	spa_t *spa = vd->vdev_spa;
 	objset_t *mos = spa->spa_meta_objset;
 	int err = 0;
 	uint64_t objid;
 	uint64_t vdev_guid;
 	nvpair_t *elem = NULL;
 	nvlist_t *nvprops = NULL;
 	uint64_t intval = 0;
 	char *strval = NULL;
 	const char *propname = NULL;
 	vdev_prop_t prop;
 
 	ASSERT(vd != NULL);
 	ASSERT(mos != NULL);
 
 	if (nvlist_lookup_uint64(innvl, ZPOOL_VDEV_PROPS_GET_VDEV,
 	    &vdev_guid) != 0)
 		return (SET_ERROR(EINVAL));
 
 	nvlist_lookup_nvlist(innvl, ZPOOL_VDEV_PROPS_GET_PROPS, &nvprops);
 
 	if (vd->vdev_root_zap != 0) {
 		objid = vd->vdev_root_zap;
 	} else if (vd->vdev_top_zap != 0) {
 		objid = vd->vdev_top_zap;
 	} else if (vd->vdev_leaf_zap != 0) {
 		objid = vd->vdev_leaf_zap;
 	} else {
 		return (SET_ERROR(EINVAL));
 	}
 	ASSERT(objid != 0);
 
 	mutex_enter(&spa->spa_props_lock);
 
 	if (nvprops != NULL) {
 		char namebuf[64] = { 0 };
 
 		while ((elem = nvlist_next_nvpair(nvprops, elem)) != NULL) {
 			intval = 0;
 			strval = NULL;
 			propname = nvpair_name(elem);
 			prop = vdev_name_to_prop(propname);
 			zprop_source_t src = ZPROP_SRC_DEFAULT;
 			uint64_t integer_size, num_integers;
 
 			switch (prop) {
 			/* Special Read-only Properties */
 			case VDEV_PROP_NAME:
 				strval = vdev_name(vd, namebuf,
 				    sizeof (namebuf));
 				if (strval == NULL)
 					continue;
 				vdev_prop_add_list(outnvl, propname, strval, 0,
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_CAPACITY:
 				/* percent used */
 				intval = (vd->vdev_stat.vs_dspace == 0) ? 0 :
 				    (vd->vdev_stat.vs_alloc * 100 /
 				    vd->vdev_stat.vs_dspace);
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    intval, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_STATE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_state, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_GUID:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_guid, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_ASIZE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_asize, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_PSIZE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_psize, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_ASHIFT:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_ashift, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_SIZE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_dspace, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_FREE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_dspace -
 				    vd->vdev_stat.vs_alloc, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_ALLOCATED:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_alloc, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_EXPANDSZ:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_esize, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_FRAGMENTATION:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_fragmentation,
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_PARITY:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vdev_get_nparity(vd), ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_PATH:
 				if (vd->vdev_path == NULL)
 					continue;
 				vdev_prop_add_list(outnvl, propname,
 				    vd->vdev_path, 0, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_DEVID:
 				if (vd->vdev_devid == NULL)
 					continue;
 				vdev_prop_add_list(outnvl, propname,
 				    vd->vdev_devid, 0, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_PHYS_PATH:
 				if (vd->vdev_physpath == NULL)
 					continue;
 				vdev_prop_add_list(outnvl, propname,
 				    vd->vdev_physpath, 0, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_ENC_PATH:
 				if (vd->vdev_enc_sysfs_path == NULL)
 					continue;
 				vdev_prop_add_list(outnvl, propname,
 				    vd->vdev_enc_sysfs_path, 0, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_FRU:
 				if (vd->vdev_fru == NULL)
 					continue;
 				vdev_prop_add_list(outnvl, propname,
 				    vd->vdev_fru, 0, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_PARENT:
 				if (vd->vdev_parent != NULL) {
 					strval = vdev_name(vd->vdev_parent,
 					    namebuf, sizeof (namebuf));
 					vdev_prop_add_list(outnvl, propname,
 					    strval, 0, ZPROP_SRC_NONE);
 				}
 				continue;
 			case VDEV_PROP_CHILDREN:
 				if (vd->vdev_children > 0)
 					strval = kmem_zalloc(ZAP_MAXVALUELEN,
 					    KM_SLEEP);
 				for (uint64_t i = 0; i < vd->vdev_children;
 				    i++) {
 					const char *vname;
 
 					vname = vdev_name(vd->vdev_child[i],
 					    namebuf, sizeof (namebuf));
 					if (vname == NULL)
 						vname = "(unknown)";
 					if (strlen(strval) > 0)
 						strlcat(strval, ",",
 						    ZAP_MAXVALUELEN);
 					strlcat(strval, vname, ZAP_MAXVALUELEN);
 				}
 				if (strval != NULL) {
 					vdev_prop_add_list(outnvl, propname,
 					    strval, 0, ZPROP_SRC_NONE);
 					kmem_free(strval, ZAP_MAXVALUELEN);
 				}
 				continue;
 			case VDEV_PROP_NUMCHILDREN:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_children, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_READ_ERRORS:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_read_errors,
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_WRITE_ERRORS:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_write_errors,
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_CHECKSUM_ERRORS:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_checksum_errors,
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_INITIALIZE_ERRORS:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_initialize_errors,
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_OPS_NULL:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_ops[ZIO_TYPE_NULL],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_OPS_READ:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_ops[ZIO_TYPE_READ],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_OPS_WRITE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_ops[ZIO_TYPE_WRITE],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_OPS_FREE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_ops[ZIO_TYPE_FREE],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_OPS_CLAIM:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_ops[ZIO_TYPE_CLAIM],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_OPS_TRIM:
 				/*
 				 * TRIM ops and bytes are reported to user
 				 * space as ZIO_TYPE_FLUSH.  This is done to
 				 * preserve the vdev_stat_t structure layout
 				 * for user space.
 				 */
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_ops[ZIO_TYPE_FLUSH],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_BYTES_NULL:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_bytes[ZIO_TYPE_NULL],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_BYTES_READ:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_bytes[ZIO_TYPE_READ],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_BYTES_WRITE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_bytes[ZIO_TYPE_WRITE],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_BYTES_FREE:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_bytes[ZIO_TYPE_FREE],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_BYTES_CLAIM:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_bytes[ZIO_TYPE_CLAIM],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_BYTES_TRIM:
 				/*
 				 * TRIM ops and bytes are reported to user
 				 * space as ZIO_TYPE_FLUSH.  This is done to
 				 * preserve the vdev_stat_t structure layout
 				 * for user space.
 				 */
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_stat.vs_bytes[ZIO_TYPE_FLUSH],
 				    ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_REMOVING:
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    vd->vdev_removing, ZPROP_SRC_NONE);
 				continue;
 			case VDEV_PROP_RAIDZ_EXPANDING:
 				/* Only expose this for raidz */
 				if (vd->vdev_ops == &vdev_raidz_ops) {
 					vdev_prop_add_list(outnvl, propname,
 					    NULL, vd->vdev_rz_expanding,
 					    ZPROP_SRC_NONE);
 				}
 				continue;
 			/* Numeric Properites */
 			case VDEV_PROP_ALLOCATING:
 				/* Leaf vdevs cannot have this property */
 				if (vd->vdev_mg == NULL &&
 				    vd->vdev_top != NULL) {
 					src = ZPROP_SRC_NONE;
 					intval = ZPROP_BOOLEAN_NA;
 				} else {
 					err = vdev_prop_get_int(vd, prop,
 					    &intval);
 					if (err && err != ENOENT)
 						break;
 
 					if (intval ==
 					    vdev_prop_default_numeric(prop))
 						src = ZPROP_SRC_DEFAULT;
 					else
 						src = ZPROP_SRC_LOCAL;
 				}
 
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    intval, src);
 				break;
 			case VDEV_PROP_FAILFAST:
 				src = ZPROP_SRC_LOCAL;
 				strval = NULL;
 
 				err = zap_lookup(mos, objid, nvpair_name(elem),
 				    sizeof (uint64_t), 1, &intval);
 				if (err == ENOENT) {
 					intval = vdev_prop_default_numeric(
 					    prop);
 					err = 0;
 				} else if (err) {
 					break;
 				}
 				if (intval == vdev_prop_default_numeric(prop))
 					src = ZPROP_SRC_DEFAULT;
 
 				vdev_prop_add_list(outnvl, propname, strval,
 				    intval, src);
 				break;
 			case VDEV_PROP_CHECKSUM_N:
 			case VDEV_PROP_CHECKSUM_T:
 			case VDEV_PROP_IO_N:
 			case VDEV_PROP_IO_T:
 			case VDEV_PROP_SLOW_IO_N:
 			case VDEV_PROP_SLOW_IO_T:
 				err = vdev_prop_get_int(vd, prop, &intval);
 				if (err && err != ENOENT)
 					break;
 
 				if (intval == vdev_prop_default_numeric(prop))
 					src = ZPROP_SRC_DEFAULT;
 				else
 					src = ZPROP_SRC_LOCAL;
 
 				vdev_prop_add_list(outnvl, propname, NULL,
 				    intval, src);
 				break;
 			/* Text Properties */
 			case VDEV_PROP_COMMENT:
 				/* Exists in the ZAP below */
 				/* FALLTHRU */
 			case VDEV_PROP_USERPROP:
 				/* User Properites */
 				src = ZPROP_SRC_LOCAL;
 
 				err = zap_length(mos, objid, nvpair_name(elem),
 				    &integer_size, &num_integers);
 				if (err)
 					break;
 
 				switch (integer_size) {
 				case 8:
 					/* User properties cannot be integers */
 					err = EINVAL;
 					break;
 				case 1:
 					/* string property */
 					strval = kmem_alloc(num_integers,
 					    KM_SLEEP);
 					err = zap_lookup(mos, objid,
 					    nvpair_name(elem), 1,
 					    num_integers, strval);
 					if (err) {
 						kmem_free(strval,
 						    num_integers);
 						break;
 					}
 					vdev_prop_add_list(outnvl, propname,
 					    strval, 0, src);
 					kmem_free(strval, num_integers);
 					break;
 				}
 				break;
 			default:
 				err = ENOENT;
 				break;
 			}
 			if (err)
 				break;
 		}
 	} else {
 		/*
 		 * Get all properties from the MOS vdev property object.
 		 */
 		zap_cursor_t zc;
 		zap_attribute_t za;
 		for (zap_cursor_init(&zc, mos, objid);
 		    (err = zap_cursor_retrieve(&zc, &za)) == 0;
 		    zap_cursor_advance(&zc)) {
 			intval = 0;
 			strval = NULL;
 			zprop_source_t src = ZPROP_SRC_DEFAULT;
 			propname = za.za_name;
 
 			switch (za.za_integer_length) {
 			case 8:
 				/* We do not allow integer user properties */
 				/* This is likely an internal value */
 				break;
 			case 1:
 				/* string property */
 				strval = kmem_alloc(za.za_num_integers,
 				    KM_SLEEP);
 				err = zap_lookup(mos, objid, za.za_name, 1,
 				    za.za_num_integers, strval);
 				if (err) {
 					kmem_free(strval, za.za_num_integers);
 					break;
 				}
 				vdev_prop_add_list(outnvl, propname, strval, 0,
 				    src);
 				kmem_free(strval, za.za_num_integers);
 				break;
 
 			default:
 				break;
 			}
 		}
 		zap_cursor_fini(&zc);
 	}
 
 	mutex_exit(&spa->spa_props_lock);
 	if (err && err != ENOENT) {
 		return (err);
 	}
 
 	return (0);
 }
 
 EXPORT_SYMBOL(vdev_fault);
 EXPORT_SYMBOL(vdev_degrade);
 EXPORT_SYMBOL(vdev_online);
 EXPORT_SYMBOL(vdev_offline);
 EXPORT_SYMBOL(vdev_clear);
 
 ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, default_ms_count, UINT, ZMOD_RW,
 	"Target number of metaslabs per top-level vdev");
 
 ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, default_ms_shift, UINT, ZMOD_RW,
 	"Default lower limit for metaslab size");
 
 ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, max_ms_shift, UINT, ZMOD_RW,
 	"Default upper limit for metaslab size");
 
 ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, min_ms_count, UINT, ZMOD_RW,
 	"Minimum number of metaslabs per top-level vdev");
 
 ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, ms_count_limit, UINT, ZMOD_RW,
 	"Practical upper limit of total metaslabs per top-level vdev");
 
 ZFS_MODULE_PARAM(zfs, zfs_, slow_io_events_per_second, UINT, ZMOD_RW,
 	"Rate limit slow IO (delay) events to this many per second");
 
 ZFS_MODULE_PARAM(zfs, zfs_, deadman_events_per_second, UINT, ZMOD_RW,
 	"Rate limit hung IO (deadman) events to this many per second");
 
 /* BEGIN CSTYLED */
 ZFS_MODULE_PARAM(zfs, zfs_, checksum_events_per_second, UINT, ZMOD_RW,
 	"Rate limit checksum events to this many checksum errors per second "
 	"(do not set below ZED threshold).");
 /* END CSTYLED */
 
 ZFS_MODULE_PARAM(zfs, zfs_, scan_ignore_errors, INT, ZMOD_RW,
 	"Ignore errors during resilver/scrub");
 
 ZFS_MODULE_PARAM(zfs_vdev, vdev_, validate_skip, INT, ZMOD_RW,
 	"Bypass vdev_validate()");
 
 ZFS_MODULE_PARAM(zfs, zfs_, nocacheflush, INT, ZMOD_RW,
 	"Disable cache flushes");
 
 ZFS_MODULE_PARAM(zfs, zfs_, embedded_slog_min_ms, UINT, ZMOD_RW,
 	"Minimum number of metaslabs required to dedicate one for log blocks");
 
 /* BEGIN CSTYLED */
 ZFS_MODULE_PARAM_CALL(zfs_vdev, zfs_vdev_, min_auto_ashift,
 	param_set_min_auto_ashift, param_get_uint, ZMOD_RW,
 	"Minimum ashift used when creating new top-level vdevs");
 
 ZFS_MODULE_PARAM_CALL(zfs_vdev, zfs_vdev_, max_auto_ashift,
 	param_set_max_auto_ashift, param_get_uint, ZMOD_RW,
 	"Maximum ashift used when optimizing for logical -> physical sector "
 	"size on new top-level vdevs");
 /* END CSTYLED */