Initial import from vendor-sys branch of openzfs

1 files changed, 5090 insertions, 0 deletions

diff --git a/sys/contrib/openzfs/module/zfs/vdev.c b/sys/contrib/openzfs/module/zfs/vdev.c
new file mode 100644
index 000000000000..1844a5653f12
--- /dev/null
+++ b/sys/contrib/openzfs/module/zfs/vdev.c
@@ -0,0 +1,5090 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2020 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.
+ */
+
+#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/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/abd.h>
+#include <sys/vdev_initialize.h>
+#include <sys/vdev_trim.h>
+#include <sys/zvol.h>
+#include <sys/zfs_ratelimit.h>
+
+/* default target for number of metaslabs per top-level vdev */
+int zfs_vdev_default_ms_count = 200;
+
+/* minimum number of metaslabs per top-level vdev */
+int zfs_vdev_min_ms_count = 16;
+
+/* practical upper limit of total metaslabs per top-level vdev */
+int zfs_vdev_ms_count_limit = 1ULL << 17;
+
+/* lower limit for metaslab size (512M) */
+int zfs_vdev_default_ms_shift = 29;
+
+/* upper limit for metaslab size (16G) */
+int 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.
+ */
+unsigned int zfs_slow_io_events_per_second = 20;
+
+/*
+ * Rate limit checksum events after this many checksum errors per second.
+ */
+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.
+ */
+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;
+
+uint64_t zfs_vdev_max_auto_ashift = ASHIFT_MAX;
+uint64_t zfs_vdev_min_auto_ashift = ASHIFT_MIN;
+
+/*PRINTFLIKE2*/
+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 %u: %s", indent, "", 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 *vdev_ops_table[] = {
+	&vdev_root_ops,
+	&vdev_raidz_ops,
+	&vdev_mirror_ops,
+	&vdev_replacing_ops,
+	&vdev_spare_ops,
+	&vdev_disk_ops,
+	&vdev_file_ops,
+	&vdev_missing_ops,
+	&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, **opspp;
+
+	for (opspp = vdev_ops_table; (ops = *opspp) != NULL; opspp++)
+		if (strcmp(ops->vdev_op_type, type) == 0)
+			break;
+
+	return (ops);
+}
+
+/* ARGSUSED */
+void
+vdev_default_xlate(vdev_t *vd, const range_seg64_t *in, range_seg64_t *res)
+{
+	res->rs_start = in->rs_start;
+	res->rs_end = in->rs_end;
+}
+
+/*
+ * Derive the enumerated allocation bias from string input.
+ * String origin is either the per-vdev zap or zpool(1M).
+ */
+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 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(vd->vdev_child[c], psize);
+		asize = MAX(asize, csize);
+	}
+
+	return (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(vd->vdev_asize, 1ULL << vd->vdev_ms_shift));
+
+	/*
+	 * The allocatable space for a raidz vdev is N * sizeof(smallest child),
+	 * so each child must provide at least 1/Nth of its asize.
+	 */
+	if (pvd->vdev_ops == &vdev_raidz_ops)
+		return ((pvd->vdev_min_asize + pvd->vdev_children - 1) /
+		    pvd->vdev_children);
+
+	return (pvd->vdev_min_asize);
+}
+
+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]);
+}
+
+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) {
+		bcopy(pvd->vdev_child, newchild, oldsize);
+		kmem_free(pvd->vdev_child, oldsize);
+	}
+
+	pvd->vdev_child = newchild;
+	pvd->vdev_child[id] = cvd;
+
+	cvd->vdev_top = (pvd->vdev_top ? pvd->vdev_top: cvd);
+	ASSERT(cvd->vdev_top->vdev_parent->vdev_parent == NULL);
+
+	/*
+	 * Walk up all ancestors to update guid sum.
+	 */
+	for (; pvd != NULL; pvd = pvd->vdev_parent)
+		pvd->vdev_guid_sum += cvd->vdev_guid_sum;
+
+	if (cvd->vdev_ops->vdev_op_leaf) {
+		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_checksum_rl,
+	    &zfs_checksum_events_per_second, 1);
+
+	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_trim_io_cv, NULL, CV_DEFAULT, NULL);
+
+	mutex_init(&vd->vdev_rebuild_lock, NULL, MUTEX_DEFAULT, NULL);
+	mutex_init(&vd->vdev_rebuild_io_lock, NULL, MUTEX_DEFAULT, NULL);
+	cv_init(&vd->vdev_rebuild_cv, NULL, CV_DEFAULT, NULL);
+	cv_init(&vd->vdev_rebuild_io_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);
+	vdev_cache_init(vd);
+
+	return (vd);
+}
+
+/*
+ * Allocate a new vdev.  The 'alloctype' is used to control whether we are
+ * creating a new vdev or loading an existing one - the behavior is slightly
+ * different for each case.
+ */
+int
+vdev_alloc(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent, uint_t id,
+    int alloctype)
+{
+	vdev_ops_t *ops;
+	char *type;
+	uint64_t guid = 0, islog, nparity;
+	vdev_t *vd;
+	vdev_indirect_config_t *vic;
+	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));
+
+	/*
+	 * Set the nparity property for RAID-Z vdevs.
+	 */
+	nparity = -1ULL;
+	if (ops == &vdev_raidz_ops) {
+		if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NPARITY,
+		    &nparity) == 0) {
+			if (nparity == 0 || nparity > VDEV_RAIDZ_MAXPARITY)
+				return (SET_ERROR(EINVAL));
+			/*
+			 * Previous versions could only support 1 or 2 parity
+			 * device.
+			 */
+			if (nparity > 1 &&
+			    spa_version(spa) < SPA_VERSION_RAIDZ2)
+				return (SET_ERROR(ENOTSUP));
+			if (nparity > 2 &&
+			    spa_version(spa) < SPA_VERSION_RAIDZ3)
+				return (SET_ERROR(ENOTSUP));
+		} else {
+			/*
+			 * We require the parity to be specified for SPAs that
+			 * support multiple parity levels.
+			 */
+			if (spa_version(spa) >= SPA_VERSION_RAIDZ2)
+				return (SET_ERROR(EINVAL));
+			/*
+			 * Otherwise, we default to 1 parity device for RAID-Z.
+			 */
+			nparity = 1;
+		}
+	} else {
+		nparity = 0;
+	}
+	ASSERT(nparity != -1ULL);
+
+	/*
+	 * If creating a top-level vdev, check for allocation classes input
+	 */
+	if (top_level && alloctype == VDEV_ALLOC_ADD) {
+		char *bias;
+
+		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));
+			}
+		}
+	}
+
+	vd = vdev_alloc_common(spa, id, guid, ops);
+	vic = &vd->vdev_indirect_config;
+
+	vd->vdev_islog = islog;
+	vd->vdev_nparity = nparity;
+	if (top_level && alloc_bias != VDEV_BIAS_NONE)
+		vd->vdev_alloc_bias = alloc_bias;
+
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &vd->vdev_path) == 0)
+		vd->vdev_path = spa_strdup(vd->vdev_path);
+
+	/*
+	 * 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, &vd->vdev_devid) == 0)
+		vd->vdev_devid = spa_strdup(vd->vdev_devid);
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PHYS_PATH,
+	    &vd->vdev_physpath) == 0)
+		vd->vdev_physpath = spa_strdup(vd->vdev_physpath);
+
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_VDEV_ENC_SYSFS_PATH,
+	    &vd->vdev_enc_sysfs_path) == 0)
+		vd->vdev_enc_sysfs_path = spa_strdup(vd->vdev_enc_sysfs_path);
+
+	if (nvlist_lookup_string(nv, ZPOOL_CONFIG_FRU, &vd->vdev_fru) == 0)
+		vd->vdev_fru = spa_strdup(vd->vdev_fru);
+
+	/*
+	 * 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;
+
+	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.
+	 */
+	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT, &vd->vdev_ashift);
+
+	/*
+	 * Retrieve the vdev creation time.
+	 */
+	(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_CREATE_TXG,
+	    &vd->vdev_crtxg);
+
+	/*
+	 * 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_REMOVING,
+		    &vd->vdev_removing);
+		(void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_VDEV_TOP_ZAP,
+		    &vd->vdev_top_zap);
+	} 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) {
+				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);
+
+	/*
+	 * Discard allocation state.
+	 */
+	if (vd->vdev_mg != NULL) {
+		vdev_metaslab_fini(vd);
+		metaslab_group_destroy(vd->vdev_mg);
+		vd->vdev_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);
+	vdev_cache_fini(vd);
+
+	if (vd->vdev_path)
+		spa_strfree(vd->vdev_path);
+	if (vd->vdev_devid)
+		spa_strfree(vd->vdev_devid);
+	if (vd->vdev_physpath)
+		spa_strfree(vd->vdev_physpath);
+
+	if (vd->vdev_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_trim_io_cv);
+
+	mutex_destroy(&vd->vdev_rebuild_lock);
+	mutex_destroy(&vd->vdev_rebuild_io_lock);
+	cv_destroy(&vd->vdev_rebuild_cv);
+	cv_destroy(&vd->vdev_rebuild_io_cv);
+
+	zfs_ratelimit_fini(&vd->vdev_delay_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_pending_fastwrite = svd->vdev_pending_fastwrite;
+	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);
+	tvd->vdev_mg = svd->vdev_mg;
+	tvd->vdev_ms = svd->vdev_ms;
+
+	svd->vdev_mg = NULL;
+	svd->vdev_ms = NULL;
+
+	if (tvd->vdev_mg != NULL)
+		tvd->vdev_mg->mg_vd = tvd;
+
+	tvd->vdev_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_removing);
+	ASSERT0(tvd->vdev_rebuilding);
+	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_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.
+ */
+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);
+}
+
+static 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);
+
+		/*
+		 * The spa ashift values currently only reflect the
+		 * general vdev classes. Class destination is late
+		 * binding so ashift checking 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;
+		}
+	}
+}
+
+int
+vdev_metaslab_init(vdev_t *vd, uint64_t txg)
+{
+	spa_t *spa = vd->vdev_spa;
+	objset_t *mos = spa->spa_meta_objset;
+	uint64_t m;
+	uint64_t oldc = vd->vdev_ms_count;
+	uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
+	metaslab_t **mspp;
+	int error;
+	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) {
+		bcopy(vd->vdev_ms, mspp, oldc * sizeof (*mspp));
+		vmem_free(vd->vdev_ms, oldc * sizeof (*mspp));
+	}
+
+	vd->vdev_ms = mspp;
+	vd->vdev_ms_count = newc;
+	for (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(mos, 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);
+			}
+		}
+
+#ifndef _KERNEL
+		/*
+		 * To accommodate zdb_leak_init() fake indirect
+		 * metaslabs, we allocate a metaslab group for
+		 * indirect vdevs which normally don't have one.
+		 */
+		if (vd->vdev_mg == NULL) {
+			ASSERT0(vdev_is_concrete(vd));
+			vdev_metaslab_group_create(vd);
+		}
+#endif
+		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);
+		}
+	}
+
+	if (txg == 0)
+		spa_config_enter(spa, SCL_ALLOC, FTAG, RW_WRITER);
+
+	/*
+	 * If the vdev is being removed we don't activate
+	 * the metaslabs since we want to ensure that no new
+	 * allocations are performed on this device.
+	 */
+	if (!expanding && !vd->vdev_removing) {
+		metaslab_group_activate(vd->vdev_mg);
+	}
+
+	if (txg == 0)
+		spa_config_exit(spa, SCL_ALLOC, FTAG);
+
+	/*
+	 * Regardless whether this vdev was just added or it is being
+	 * expanded, the metaslab count has changed. Recalculate the
+	 * block limit.
+	 */
+	spa_log_sm_set_blocklimit(spa);
+
+	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);
+
+		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]);
+	}
+	ASSERT0(vd->vdev_ms_count);
+	ASSERT3U(vd->vdev_pending_fastwrite, ==, 0);
+}
+
+typedef struct vdev_probe_stats {
+	boolean_t	vps_readable;
+	boolean_t	vps_writeable;
+	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;
+
+		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");
+			zfs_ereport_post(FM_EREPORT_ZFS_PROBE_FAILURE,
+			    spa, vd, NULL, NULL, 0, 0);
+			zio->io_error = SET_ERROR(ENXIO);
+		}
+
+		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_CACHE | ZIO_FLAG_DONT_AGGREGATE |
+		    ZIO_FLAG_TRYHARD;
+
+		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);
+
+		/*
+		 * We can't change the vdev state in this context, so we
+		 * kick off an async task to do it on our behalf.
+		 */
+		if (zio != NULL) {
+			vd->vdev_probe_wanted = B_TRUE;
+			spa_async_request(spa, SPA_ASYNC_PROBE);
+		}
+	}
+
+	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_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);
+}
+
+void
+vdev_open_children(vdev_t *vd)
+{
+	taskq_t *tq;
+	int children = vd->vdev_children;
+
+	/*
+	 * in order to handle pools on top of zvols, do the opens
+	 * in a single thread so that the same thread holds the
+	 * spa_namespace_lock
+	 */
+	if (vdev_uses_zvols(vd)) {
+retry_sync:
+		for (int c = 0; c < children; c++)
+			vd->vdev_child[c]->vdev_open_error =
+			    vdev_open(vd->vdev_child[c]);
+	} else {
+		tq = taskq_create("vdev_open", children, minclsyspri,
+		    children, children, TASKQ_PREPOPULATE);
+		if (tq == NULL)
+			goto retry_sync;
+
+		for (int c = 0; c < children; c++)
+			VERIFY(taskq_dispatch(tq, vdev_open_child,
+			    vd->vdev_child[c], TQ_SLEEP) != TASKQID_INVALID);
+
+		taskq_destroy(tq);
+	}
+
+	vd->vdev_nonrot = B_TRUE;
+
+	for (int c = 0; c < children; c++)
+		vd->vdev_nonrot &= vd->vdev_child[c]->vdev_nonrot;
+}
+
+/*
+ * Compute the raidz-deflation ratio.  Note, we hard-code
+ * in 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.
+ */
+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(vd, 1 << 17) >> SPA_MINBLOCKSHIFT);
+	}
+}
+
+/*
+ * 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_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);
+	/*
+	 * 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(osize, (uint64_t)sizeof (vdev_label_t));
+	max_osize = P2ALIGN(max_osize, (uint64_t)sizeof (vdev_label_t));
+
+	if (vd->vdev_children == 0) {
+		if (osize < SPA_MINDEVSIZE) {
+			vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
+			    VDEV_AUX_TOO_SMALL);
+			return (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));
+	}
+
+	vd->vdev_physical_ashift =
+	    MAX(physical_ashift, vd->vdev_physical_ashift);
+	vd->vdev_logical_ashift = MAX(logical_ashift, vd->vdev_logical_ashift);
+	vd->vdev_ashift = MAX(vd->vdev_logical_ashift, vd->vdev_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_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 (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) {
+			zfs_ereport_post(FM_EREPORT_ZFS_DEVICE_BAD_ASHIFT,
+			    spa, vd, NULL, NULL, 0, 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 min and max ashift values for normal data devices.
+	 */
+	if (vd->vdev_top == vd && vd->vdev_ashift != 0 &&
+	    vd->vdev_alloc_bias == VDEV_BIAS_NONE &&
+	    vd->vdev_islog == 0 && 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;
+	}
+
+	/*
+	 * 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);
+}
+
+/*
+ * 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;
+	nvlist_t *label;
+	uint64_t guid = 0, aux_guid = 0, top_guid;
+	uint64_t state;
+	nvlist_t *nvl;
+	uint64_t txg;
+
+	if (vdev_validate_skip)
+		return (0);
+
+	for (uint64_t c = 0; c < vd->vdev_children; c++)
+		if (vdev_validate(vd->vdev_child[c]) != 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_TRUE, 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_copy_path_impl(vdev_t *svd, vdev_t *dvd)
+{
+	if (svd->vdev_path != NULL && dvd->vdev_path != NULL) {
+		if (strcmp(svd->vdev_path, dvd->vdev_path) != 0) {
+			zfs_dbgmsg("vdev_copy_path: vdev %llu: path changed "
+			    "from '%s' to '%s'", (u_longlong_t)dvd->vdev_guid,
+			    dvd->vdev_path, svd->vdev_path);
+			spa_strfree(dvd->vdev_path);
+			dvd->vdev_path = spa_strdup(svd->vdev_path);
+		}
+	} else if (svd->vdev_path != NULL) {
+		dvd->vdev_path = spa_strdup(svd->vdev_path);
+		zfs_dbgmsg("vdev_copy_path: vdev %llu: path set to '%s'",
+		    (u_longlong_t)dvd->vdev_guid, dvd->vdev_path);
+	}
+}
+
+/*
+ * 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(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);
+
+	vdev_cache_purge(vd);
+
+	/*
+	 * We record the previous state before we close it, so that if we are
+	 * doing a reopen(), we don't generate FMA ereports if we notice that
+	 * it's still faulted.
+	 */
+	vd->vdev_prevstate = vd->vdev_state;
+
+	if (vd->vdev_offline)
+		vd->vdev_state = VDEV_STATE_OFFLINE;
+	else
+		vd->vdev_state = VDEV_STATE_CLOSED;
+	vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
+}
+
+void
+vdev_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(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(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);
+	}
+
+	/*
+	 * 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);
+}
+
+/*
+ * 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.
+ */
+void
+vdev_ashift_optimize(vdev_t *vd)
+{
+	if (vd == vd->vdev_top) {
+		if (vd->vdev_ashift < vd->vdev_physical_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 {
+			/*
+			 * Unusual case where logical ashift > physical ashift
+			 * so 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);
+		}
+	}
+}
+
+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.
+	 * Ignore the DTLs and try all devices.  This avoids a recursive
+	 * mutex enter on the vdev_dtl_lock, and also makes us try hard
+	 * when loading the pool (relying on the checksum to ensure that
+	 * we get the right data -- note that we while loading, we are
+	 * only reading the MOS, which is always checksummed).
+	 */
+	if (vd->vdev_spa->spa_load_state != SPA_LOAD_NONE)
+		return (B_FALSE);
+
+	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);
+}
+
+/*
+ * Returns B_TRUE if vdev determines offset needs to be resilvered.
+ */
+boolean_t
+vdev_dtl_need_resilver(vdev_t *vd, uint64_t offset, size_t psize)
+{
+	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, offset, psize));
+}
+
+/*
+ * 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);
+		return;
+	}
+
+	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)
+			continue;			/* leaf vdevs only */
+		if (t == DTL_PARTIAL)
+			minref = 1;			/* i.e. non-zero */
+		else if (vd->vdev_nparity != 0)
+			minref = vd->vdev_nparity + 1;	/* RAID-Z */
+		else
+			minref = vd->vdev_children;	/* any kind of mirror */
+		space_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);
+}
+
+int
+vdev_dtl_load(vdev_t *vd)
+{
+	spa_t *spa = vd->vdev_spa;
+	objset_t *mos = spa->spa_meta_objset;
+	int error = 0;
+
+	if (vd->vdev_ops->vdev_op_leaf && vd->vdev_dtl_object != 0) {
+		ASSERT(vdev_is_concrete(vd));
+
+		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);
+
+		mutex_enter(&vd->vdev_dtl_lock);
+		error = space_map_load(vd->vdev_dtl_sm,
+		    vd->vdev_dtl[DTL_MISSING], SM_ALLOC);
+		mutex_exit(&vd->vdev_dtl_lock);
+
+		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);
+		}
+	}
+
+	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 error = 0;
+
+	/*
+	 * Recursively load all children.
+	 */
+	for (int c = 0; c < vd->vdev_children; c++) {
+		error = vdev_load(vd->vdev_child[c]);
+		if (error != 0) {
+			return (error);
+		}
+	}
+
+	vdev_set_deflate_ratio(vd);
+
+	/*
+	 * 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]", vd->vdev_top_zap, error);
+			return (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 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);
+}
+
+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);
+}
+
+uint64_t
+vdev_psize_to_asize(vdev_t *vd, uint64_t psize)
+{
+	return (vd->vdev_ops->vdev_op_asize(vd, psize));
+}
+
+/*
+ * Mark the given vdev faulted.  A faulted vdev behaves as if the device could
+ * not be opened, and no I/O is attempted.
+ */
+int
+vdev_fault(spa_t *spa, uint64_t guid, vdev_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));
+}
+
+/*
+ * 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)));
+
+	if (!vd->vdev_ops->vdev_op_leaf)
+		return (spa_vdev_state_exit(spa, NULL, SET_ERROR(ENOTSUP)));
+
+	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_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);
+
+	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)));
+
+	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.
+			 */
+			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 vdev.
+	 */
+	if (!vdev_is_concrete(vd))
+		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;
+}
+
+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)
+{
+	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)
+{
+	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 < ARRAY_SIZE(vd->vdev_queue.vq_class); t++) {
+			vsx->vsx_active_queue[t] =
+			    vd->vdev_queue.vq_class[t].vqc_active;
+			vsx->vsx_pend_queue[t] = avl_numnodes(
+			    &vd->vdev_queue.vq_class[t].vqc_queued_tree);
+		}
+	}
+}
+
+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) {
+		bcopy(&vd->vdev_stat, vs, 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_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(
+			    vd->vdev_max_asize - vd->vdev_asize,
+			    1ULL << tvd->vdev_ms_shift);
+		}
+
+		vs->vs_configured_ashift = vd->vdev_top != NULL
+		    ? vd->vdev_top->vdev_ashift : vd->vdev_ashift;
+		vs->vs_logical_ashift = vd->vdev_logical_ashift;
+		vs->vs_physical_ashift = vd->vdev_physical_ashift;
+
+		/*
+		 * 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)) {
+			vs->vs_fragmentation = (vd->vdev_mg != NULL) ?
+			    vd->vdev_mg->mg_fragmentation : 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;
+	vdev_stat_t *vs = &vd->vdev_stat;
+	vdev_stat_ex_t *vsx = &vd->vdev_stat_ex;
+	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).
+			 */
+			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)
+					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_IOCTL.  This is done to preserve the
+			 * vdev_stat_t structure layout for user space.
+			 */
+			if (type == ZIO_TYPE_TRIM)
+				vs_type = ZIO_TYPE_IOCTL;
+
+			/*
+			 * Solely for the purposes of 'zpool iostat -lqrw'
+			 * reporting use the priority to catagorize 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.
+			 */
+			if (priority == ZIO_PRIORITY_REBUILD) {
+				priority = ((type == ZIO_TYPE_WRITE) ?
+				    ZIO_PRIORITY_ASYNC_WRITE :
+				    ZIO_PRIORITY_SCRUB);
+			} else 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 (spa->spa_load_state == SPA_LOAD_NONE &&
+	    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)
+{
+	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;
+			}
+
+			zfs_ereport_post(class, spa, vd, NULL, NULL,
+			    save_state, 0);
+		}
+
+		/* 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 ||
+		    strcmp(vdev_type, VDEV_TYPE_INDIRECT) == 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_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;
+
+	vdev_remove_child(pvd, vd);
+	vdev_compact_children(pvd);
+
+	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, 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 (avl_numnodes(&vq->vq_active_tree) > 0) {
+			spa_t *spa = vd->vdev_spa;
+			zio_t *fio;
+			uint64_t delta;
+
+			zfs_dbgmsg("slow vdev: %s has %d active IOs",
+			    vd->vdev_path, avl_numnodes(&vq->vq_active_tree));
+
+			/*
+			 * 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 = avl_first(&vq->vq_active_tree);
+			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));
+}
+
+/*
+ * Translate a logical range to the 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)
+{
+	/*
+	 * Walk up the vdev tree
+	 */
+	if (vd != vd->vdev_top) {
+		vdev_xlate(vd->vdev_parent, logical_rs, physical_rs);
+	} else {
+		/*
+		 * We've reached the top-level vdev, initialize the
+		 * physical range to the logical range and start to
+		 * unwind.
+		 */
+		physical_rs->rs_start = logical_rs->rs_start;
+		physical_rs->rs_end = logical_rs->rs_end;
+		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 components by calling the
+	 * vdev specific translate function.
+	 */
+	range_seg64_t intermediate = { 0 };
+	pvd->vdev_ops->vdev_op_xlate(vd, physical_rs, &intermediate);
+
+	physical_rs->rs_start = intermediate.rs_start;
+	physical_rs->rs_end = intermediate.rs_end;
+}
+
+/*
+ * 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);
+}
+
+EXPORT_SYMBOL(vdev_fault);
+EXPORT_SYMBOL(vdev_degrade);
+EXPORT_SYMBOL(vdev_online);
+EXPORT_SYMBOL(vdev_offline);
+EXPORT_SYMBOL(vdev_clear);
+
+/* BEGIN CSTYLED */
+ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, default_ms_count, INT, ZMOD_RW,
+	"Target number of metaslabs per top-level vdev");
+
+ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, default_ms_shift, INT, ZMOD_RW,
+	"Default limit for metaslab size");
+
+ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, min_ms_count, INT, ZMOD_RW,
+	"Minimum number of metaslabs per top-level vdev");
+
+ZFS_MODULE_PARAM(zfs_vdev, zfs_vdev_, ms_count_limit, INT, 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_, checksum_events_per_second, UINT, ZMOD_RW,
+	"Rate limit checksum events to this many checksum errors per second "
+	"(do not set below zed threshold).");
+
+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_CALL(zfs_vdev, zfs_vdev_, min_auto_ashift,
+	param_set_min_auto_ashift, param_get_ulong, 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_ulong, ZMOD_RW,
+	"Maximum ashift used when optimizing for logical -> physical sector "
+	"size on new top-level vdevs");
+/* END CSTYLED */