diff --git a/module/zfs/spa.c b/module/zfs/spa.c
index 33798d3aff5f..b610a0dae6bf 100644
--- a/module/zfs/spa.c
+++ b/module/zfs/spa.c
@@ -1,6019 +1,6022 @@
 /*
  * 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 2011 Nexenta Systems, Inc. All rights reserved.
  * Copyright (c) 2012 by Delphix. All rights reserved.
  */
 
 /*
  * This file contains all the routines used when modifying on-disk SPA state.
  * This includes opening, importing, destroying, exporting a pool, and syncing a
  * pool.
  */
 
 #include <sys/zfs_context.h>
 #include <sys/fm/fs/zfs.h>
 #include <sys/spa_impl.h>
 #include <sys/zio.h>
 #include <sys/zio_checksum.h>
 #include <sys/dmu.h>
 #include <sys/dmu_tx.h>
 #include <sys/zap.h>
 #include <sys/zil.h>
 #include <sys/ddt.h>
 #include <sys/vdev_impl.h>
 #include <sys/vdev_disk.h>
 #include <sys/metaslab.h>
 #include <sys/metaslab_impl.h>
 #include <sys/uberblock_impl.h>
 #include <sys/txg.h>
 #include <sys/avl.h>
 #include <sys/dmu_traverse.h>
 #include <sys/dmu_objset.h>
 #include <sys/unique.h>
 #include <sys/dsl_pool.h>
 #include <sys/dsl_dataset.h>
 #include <sys/dsl_dir.h>
 #include <sys/dsl_prop.h>
 #include <sys/dsl_synctask.h>
 #include <sys/fs/zfs.h>
 #include <sys/arc.h>
 #include <sys/callb.h>
 #include <sys/systeminfo.h>
 #include <sys/spa_boot.h>
 #include <sys/zfs_ioctl.h>
 #include <sys/dsl_scan.h>
 
 #ifdef	_KERNEL
 #include <sys/bootprops.h>
 #include <sys/callb.h>
 #include <sys/cpupart.h>
 #include <sys/pool.h>
 #include <sys/sysdc.h>
 #include <sys/zone.h>
 #endif	/* _KERNEL */
 
 #include "zfs_prop.h"
 #include "zfs_comutil.h"
 
 typedef enum zti_modes {
 	zti_mode_fixed,			/* value is # of threads (min 1) */
 	zti_mode_online_percent,	/* value is % of online CPUs */
 	zti_mode_batch,			/* cpu-intensive; value is ignored */
 	zti_mode_null,			/* don't create a taskq */
 	zti_nmodes
 } zti_modes_t;
 
 #define	ZTI_FIX(n)	{ zti_mode_fixed, (n) }
 #define	ZTI_PCT(n)	{ zti_mode_online_percent, (n) }
 #define	ZTI_BATCH	{ zti_mode_batch, 0 }
 #define	ZTI_NULL	{ zti_mode_null, 0 }
 
 #define	ZTI_ONE		ZTI_FIX(1)
 
 typedef struct zio_taskq_info {
 	enum zti_modes zti_mode;
 	uint_t zti_value;
 } zio_taskq_info_t;
 
 static const char *const zio_taskq_types[ZIO_TASKQ_TYPES] = {
 	"iss", "iss_h", "int", "int_h"
 };
 
 /*
  * Define the taskq threads for the following I/O types:
  * 	NULL, READ, WRITE, FREE, CLAIM, and IOCTL
  */
 const zio_taskq_info_t zio_taskqs[ZIO_TYPES][ZIO_TASKQ_TYPES] = {
 	/* ISSUE	ISSUE_HIGH	INTR		INTR_HIGH */
 	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL },
 	{ ZTI_FIX(8),	ZTI_NULL,	ZTI_BATCH,	ZTI_NULL },
 	{ ZTI_BATCH,	ZTI_FIX(5),	ZTI_FIX(16),	ZTI_FIX(5) },
 	{ ZTI_PCT(100),	ZTI_NULL,	ZTI_ONE,	ZTI_NULL },
 	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL },
 	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL },
 };
 
 static dsl_syncfunc_t spa_sync_props;
 static boolean_t spa_has_active_shared_spare(spa_t *spa);
 static inline int spa_load_impl(spa_t *spa, uint64_t, nvlist_t *config,
     spa_load_state_t state, spa_import_type_t type, boolean_t mosconfig,
     char **ereport);
 static void spa_vdev_resilver_done(spa_t *spa);
 
 uint_t		zio_taskq_batch_pct = 100;	/* 1 thread per cpu in pset */
 id_t		zio_taskq_psrset_bind = PS_NONE;
 boolean_t	zio_taskq_sysdc = B_TRUE;	/* use SDC scheduling class */
 uint_t		zio_taskq_basedc = 80;		/* base duty cycle */
 
 boolean_t	spa_create_process = B_TRUE;	/* no process ==> no sysdc */
 
 /*
  * This (illegal) pool name is used when temporarily importing a spa_t in order
  * to get the vdev stats associated with the imported devices.
  */
 #define	TRYIMPORT_NAME	"$import"
 
 /*
  * ==========================================================================
  * SPA properties routines
  * ==========================================================================
  */
 
 /*
  * Add a (source=src, propname=propval) list to an nvlist.
  */
 static void
 spa_prop_add_list(nvlist_t *nvl, zpool_prop_t prop, char *strval,
     uint64_t intval, zprop_source_t src)
 {
 	const char *propname = zpool_prop_to_name(prop);
 	nvlist_t *propval;
 
 	VERIFY(nvlist_alloc(&propval, NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 	VERIFY(nvlist_add_uint64(propval, ZPROP_SOURCE, src) == 0);
 
 	if (strval != NULL)
 		VERIFY(nvlist_add_string(propval, ZPROP_VALUE, strval) == 0);
 	else
 		VERIFY(nvlist_add_uint64(propval, ZPROP_VALUE, intval) == 0);
 
 	VERIFY(nvlist_add_nvlist(nvl, propname, propval) == 0);
 	nvlist_free(propval);
 }
 
 /*
  * Get property values from the spa configuration.
  */
 static void
 spa_prop_get_config(spa_t *spa, nvlist_t **nvp)
 {
 	vdev_t *rvd = spa->spa_root_vdev;
 	uint64_t size;
 	uint64_t alloc;
 	uint64_t space;
 	uint64_t cap, version;
 	zprop_source_t src = ZPROP_SRC_NONE;
 	spa_config_dirent_t *dp;
 	int c;
 
 	ASSERT(MUTEX_HELD(&spa->spa_props_lock));
 
 	if (rvd != NULL) {
 		alloc = metaslab_class_get_alloc(spa_normal_class(spa));
 		size = metaslab_class_get_space(spa_normal_class(spa));
 		spa_prop_add_list(*nvp, ZPOOL_PROP_NAME, spa_name(spa), 0, src);
 		spa_prop_add_list(*nvp, ZPOOL_PROP_SIZE, NULL, size, src);
 		spa_prop_add_list(*nvp, ZPOOL_PROP_ALLOCATED, NULL, alloc, src);
 		spa_prop_add_list(*nvp, ZPOOL_PROP_FREE, NULL,
 		    size - alloc, src);
 
 		space = 0;
 		for (c = 0; c < rvd->vdev_children; c++) {
 			vdev_t *tvd = rvd->vdev_child[c];
 			space += tvd->vdev_max_asize - tvd->vdev_asize;
 		}
 		spa_prop_add_list(*nvp, ZPOOL_PROP_EXPANDSZ, NULL, space,
 		    src);
 
 		spa_prop_add_list(*nvp, ZPOOL_PROP_READONLY, NULL,
 		    (spa_mode(spa) == FREAD), src);
 
 		cap = (size == 0) ? 0 : (alloc * 100 / size);
 		spa_prop_add_list(*nvp, ZPOOL_PROP_CAPACITY, NULL, cap, src);
 
 		spa_prop_add_list(*nvp, ZPOOL_PROP_DEDUPRATIO, NULL,
 		    ddt_get_pool_dedup_ratio(spa), src);
 
 		spa_prop_add_list(*nvp, ZPOOL_PROP_HEALTH, NULL,
 		    rvd->vdev_state, src);
 
 		version = spa_version(spa);
 		if (version == zpool_prop_default_numeric(ZPOOL_PROP_VERSION))
 			src = ZPROP_SRC_DEFAULT;
 		else
 			src = ZPROP_SRC_LOCAL;
 		spa_prop_add_list(*nvp, ZPOOL_PROP_VERSION, NULL, version, src);
 	}
 
 	spa_prop_add_list(*nvp, ZPOOL_PROP_GUID, NULL, spa_guid(spa), src);
 
 	if (spa->spa_comment != NULL) {
 		spa_prop_add_list(*nvp, ZPOOL_PROP_COMMENT, spa->spa_comment,
 		    0, ZPROP_SRC_LOCAL);
 	}
 
 	if (spa->spa_root != NULL)
 		spa_prop_add_list(*nvp, ZPOOL_PROP_ALTROOT, spa->spa_root,
 		    0, ZPROP_SRC_LOCAL);
 
 	if ((dp = list_head(&spa->spa_config_list)) != NULL) {
 		if (dp->scd_path == NULL) {
 			spa_prop_add_list(*nvp, ZPOOL_PROP_CACHEFILE,
 			    "none", 0, ZPROP_SRC_LOCAL);
 		} else if (strcmp(dp->scd_path, spa_config_path) != 0) {
 			spa_prop_add_list(*nvp, ZPOOL_PROP_CACHEFILE,
 			    dp->scd_path, 0, ZPROP_SRC_LOCAL);
 		}
 	}
 }
 
 /*
  * Get zpool property values.
  */
 int
 spa_prop_get(spa_t *spa, nvlist_t **nvp)
 {
 	objset_t *mos = spa->spa_meta_objset;
 	zap_cursor_t zc;
 	zap_attribute_t za;
 	int err;
 
 	err = nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_PUSHPAGE);
 	if (err)
 		return err;
 
 	mutex_enter(&spa->spa_props_lock);
 
 	/*
 	 * Get properties from the spa config.
 	 */
 	spa_prop_get_config(spa, nvp);
 
 	/* If no pool property object, no more prop to get. */
 	if (mos == NULL || spa->spa_pool_props_object == 0) {
 		mutex_exit(&spa->spa_props_lock);
 		goto out;
 	}
 
 	/*
 	 * Get properties from the MOS pool property object.
 	 */
 	for (zap_cursor_init(&zc, mos, spa->spa_pool_props_object);
 	    (err = zap_cursor_retrieve(&zc, &za)) == 0;
 	    zap_cursor_advance(&zc)) {
 		uint64_t intval = 0;
 		char *strval = NULL;
 		zprop_source_t src = ZPROP_SRC_DEFAULT;
 		zpool_prop_t prop;
 
 		if ((prop = zpool_name_to_prop(za.za_name)) == ZPROP_INVAL)
 			continue;
 
 		switch (za.za_integer_length) {
 		case 8:
 			/* integer property */
 			if (za.za_first_integer !=
 			    zpool_prop_default_numeric(prop))
 				src = ZPROP_SRC_LOCAL;
 
 			if (prop == ZPOOL_PROP_BOOTFS) {
 				dsl_pool_t *dp;
 				dsl_dataset_t *ds = NULL;
 
 				dp = spa_get_dsl(spa);
 				rw_enter(&dp->dp_config_rwlock, RW_READER);
 				if ((err = dsl_dataset_hold_obj(dp,
 				    za.za_first_integer, FTAG, &ds))) {
 					rw_exit(&dp->dp_config_rwlock);
 					break;
 				}
 
 				strval = kmem_alloc(
 				    MAXNAMELEN + strlen(MOS_DIR_NAME) + 1,
 				    KM_PUSHPAGE);
 				dsl_dataset_name(ds, strval);
 				dsl_dataset_rele(ds, FTAG);
 				rw_exit(&dp->dp_config_rwlock);
 			} else {
 				strval = NULL;
 				intval = za.za_first_integer;
 			}
 
 			spa_prop_add_list(*nvp, prop, strval, intval, src);
 
 			if (strval != NULL)
 				kmem_free(strval,
 				    MAXNAMELEN + strlen(MOS_DIR_NAME) + 1);
 
 			break;
 
 		case 1:
 			/* string property */
 			strval = kmem_alloc(za.za_num_integers, KM_PUSHPAGE);
 			err = zap_lookup(mos, spa->spa_pool_props_object,
 			    za.za_name, 1, za.za_num_integers, strval);
 			if (err) {
 				kmem_free(strval, za.za_num_integers);
 				break;
 			}
 			spa_prop_add_list(*nvp, prop, strval, 0, src);
 			kmem_free(strval, za.za_num_integers);
 			break;
 
 		default:
 			break;
 		}
 	}
 	zap_cursor_fini(&zc);
 	mutex_exit(&spa->spa_props_lock);
 out:
 	if (err && err != ENOENT) {
 		nvlist_free(*nvp);
 		*nvp = NULL;
 		return (err);
 	}
 
 	return (0);
 }
 
 /*
  * Validate the given pool properties nvlist and modify the list
  * for the property values to be set.
  */
 static int
 spa_prop_validate(spa_t *spa, nvlist_t *props)
 {
 	nvpair_t *elem;
 	int error = 0, reset_bootfs = 0;
 	uint64_t objnum = 0;
 
 	elem = NULL;
 	while ((elem = nvlist_next_nvpair(props, elem)) != NULL) {
 		zpool_prop_t prop;
 		char *propname, *strval;
 		uint64_t intval;
 		objset_t *os;
 		char *slash, *check;
 
 		propname = nvpair_name(elem);
 
 		if ((prop = zpool_name_to_prop(propname)) == ZPROP_INVAL)
 			return (EINVAL);
 
 		switch (prop) {
 		case ZPOOL_PROP_VERSION:
 			error = nvpair_value_uint64(elem, &intval);
 			if (!error &&
 			    (intval < spa_version(spa) || intval > SPA_VERSION))
 				error = EINVAL;
 			break;
 
 		case ZPOOL_PROP_DELEGATION:
 		case ZPOOL_PROP_AUTOREPLACE:
 		case ZPOOL_PROP_LISTSNAPS:
 		case ZPOOL_PROP_AUTOEXPAND:
 			error = nvpair_value_uint64(elem, &intval);
 			if (!error && intval > 1)
 				error = EINVAL;
 			break;
 
 		case ZPOOL_PROP_BOOTFS:
 			/*
 			 * If the pool version is less than SPA_VERSION_BOOTFS,
 			 * or the pool is still being created (version == 0),
 			 * the bootfs property cannot be set.
 			 */
 			if (spa_version(spa) < SPA_VERSION_BOOTFS) {
 				error = ENOTSUP;
 				break;
 			}
 
 			/*
 			 * Make sure the vdev config is bootable
 			 */
 			if (!vdev_is_bootable(spa->spa_root_vdev)) {
 				error = ENOTSUP;
 				break;
 			}
 
 			reset_bootfs = 1;
 
 			error = nvpair_value_string(elem, &strval);
 
 			if (!error) {
 				uint64_t compress;
 
 				if (strval == NULL || strval[0] == '\0') {
 					objnum = zpool_prop_default_numeric(
 					    ZPOOL_PROP_BOOTFS);
 					break;
 				}
 
 				if ((error = dmu_objset_hold(strval,FTAG,&os)))
 					break;
 
 				/* Must be ZPL and not gzip compressed. */
 
 				if (dmu_objset_type(os) != DMU_OST_ZFS) {
 					error = ENOTSUP;
 				} else if ((error = dsl_prop_get_integer(strval,
 				    zfs_prop_to_name(ZFS_PROP_COMPRESSION),
 				    &compress, NULL)) == 0 &&
 				    !BOOTFS_COMPRESS_VALID(compress)) {
 					error = ENOTSUP;
 				} else {
 					objnum = dmu_objset_id(os);
 				}
 				dmu_objset_rele(os, FTAG);
 			}
 			break;
 
 		case ZPOOL_PROP_FAILUREMODE:
 			error = nvpair_value_uint64(elem, &intval);
 			if (!error && (intval < ZIO_FAILURE_MODE_WAIT ||
 			    intval > ZIO_FAILURE_MODE_PANIC))
 				error = EINVAL;
 
 			/*
 			 * This is a special case which only occurs when
 			 * the pool has completely failed. This allows
 			 * the user to change the in-core failmode property
 			 * without syncing it out to disk (I/Os might
 			 * currently be blocked). We do this by returning
 			 * EIO to the caller (spa_prop_set) to trick it
 			 * into thinking we encountered a property validation
 			 * error.
 			 */
 			if (!error && spa_suspended(spa)) {
 				spa->spa_failmode = intval;
 				error = EIO;
 			}
 			break;
 
 		case ZPOOL_PROP_CACHEFILE:
 			if ((error = nvpair_value_string(elem, &strval)) != 0)
 				break;
 
 			if (strval[0] == '\0')
 				break;
 
 			if (strcmp(strval, "none") == 0)
 				break;
 
 			if (strval[0] != '/') {
 				error = EINVAL;
 				break;
 			}
 
 			slash = strrchr(strval, '/');
 			ASSERT(slash != NULL);
 
 			if (slash[1] == '\0' || strcmp(slash, "/.") == 0 ||
 			    strcmp(slash, "/..") == 0)
 				error = EINVAL;
 			break;
 
 		case ZPOOL_PROP_COMMENT:
 			if ((error = nvpair_value_string(elem, &strval)) != 0)
 				break;
 			for (check = strval; *check != '\0'; check++) {
 				if (!isprint(*check)) {
 					error = EINVAL;
 					break;
 				}
 				check++;
 			}
 			if (strlen(strval) > ZPROP_MAX_COMMENT)
 				error = E2BIG;
 			break;
 
 		case ZPOOL_PROP_DEDUPDITTO:
 			if (spa_version(spa) < SPA_VERSION_DEDUP)
 				error = ENOTSUP;
 			else
 				error = nvpair_value_uint64(elem, &intval);
 			if (error == 0 &&
 			    intval != 0 && intval < ZIO_DEDUPDITTO_MIN)
 				error = EINVAL;
 			break;
 
 		default:
 			break;
 		}
 
 		if (error)
 			break;
 	}
 
 	if (!error && reset_bootfs) {
 		error = nvlist_remove(props,
 		    zpool_prop_to_name(ZPOOL_PROP_BOOTFS), DATA_TYPE_STRING);
 
 		if (!error) {
 			error = nvlist_add_uint64(props,
 			    zpool_prop_to_name(ZPOOL_PROP_BOOTFS), objnum);
 		}
 	}
 
 	return (error);
 }
 
 void
 spa_configfile_set(spa_t *spa, nvlist_t *nvp, boolean_t need_sync)
 {
 	char *cachefile;
 	spa_config_dirent_t *dp;
 
 	if (nvlist_lookup_string(nvp, zpool_prop_to_name(ZPOOL_PROP_CACHEFILE),
 	    &cachefile) != 0)
 		return;
 
 	dp = kmem_alloc(sizeof (spa_config_dirent_t),
 	    KM_PUSHPAGE);
 
 	if (cachefile[0] == '\0')
 		dp->scd_path = spa_strdup(spa_config_path);
 	else if (strcmp(cachefile, "none") == 0)
 		dp->scd_path = NULL;
 	else
 		dp->scd_path = spa_strdup(cachefile);
 
 	list_insert_head(&spa->spa_config_list, dp);
 	if (need_sync)
 		spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
 }
 
 int
 spa_prop_set(spa_t *spa, nvlist_t *nvp)
 {
 	int error;
 	nvpair_t *elem;
 	boolean_t need_sync = B_FALSE;
 	zpool_prop_t prop;
 
 	if ((error = spa_prop_validate(spa, nvp)) != 0)
 		return (error);
 
 	elem = NULL;
 	while ((elem = nvlist_next_nvpair(nvp, elem)) != NULL) {
 		if ((prop = zpool_name_to_prop(
 		    nvpair_name(elem))) == ZPROP_INVAL)
 			return (EINVAL);
 
 		if (prop == ZPOOL_PROP_CACHEFILE ||
 		    prop == ZPOOL_PROP_ALTROOT ||
 		    prop == ZPOOL_PROP_READONLY)
 			continue;
 
 		need_sync = B_TRUE;
 		break;
 	}
 
 	if (need_sync)
 		return (dsl_sync_task_do(spa_get_dsl(spa), NULL, spa_sync_props,
 		    spa, nvp, 3));
 	else
 		return (0);
 }
 
 /*
  * If the bootfs property value is dsobj, clear it.
  */
 void
 spa_prop_clear_bootfs(spa_t *spa, uint64_t dsobj, dmu_tx_t *tx)
 {
 	if (spa->spa_bootfs == dsobj && spa->spa_pool_props_object != 0) {
 		VERIFY(zap_remove(spa->spa_meta_objset,
 		    spa->spa_pool_props_object,
 		    zpool_prop_to_name(ZPOOL_PROP_BOOTFS), tx) == 0);
 		spa->spa_bootfs = 0;
 	}
 }
 
 /*
  * Change the GUID for the pool.  This is done so that we can later
  * re-import a pool built from a clone of our own vdevs.  We will modify
  * the root vdev's guid, our own pool guid, and then mark all of our
  * vdevs dirty.  Note that we must make sure that all our vdevs are
  * online when we do this, or else any vdevs that weren't present
  * would be orphaned from our pool.  We are also going to issue a
  * sysevent to update any watchers.
  */
 int
 spa_change_guid(spa_t *spa)
 {
 	uint64_t	oldguid, newguid;
 	uint64_t	txg;
 
 	if (!(spa_mode_global & FWRITE))
 		return (EROFS);
 
 	txg = spa_vdev_enter(spa);
 
 	if (spa->spa_root_vdev->vdev_state != VDEV_STATE_HEALTHY)
 		return (spa_vdev_exit(spa, NULL, txg, ENXIO));
 
 	oldguid = spa_guid(spa);
 	newguid = spa_generate_guid(NULL);
 	ASSERT3U(oldguid, !=, newguid);
 
 	spa->spa_root_vdev->vdev_guid = newguid;
 	spa->spa_root_vdev->vdev_guid_sum += (newguid - oldguid);
 
 	vdev_config_dirty(spa->spa_root_vdev);
 
 	spa_event_notify(spa, NULL, FM_EREPORT_ZFS_POOL_REGUID);
 
 	return (spa_vdev_exit(spa, NULL, txg, 0));
 }
 
 /*
  * ==========================================================================
  * SPA state manipulation (open/create/destroy/import/export)
  * ==========================================================================
  */
 
 static int
 spa_error_entry_compare(const void *a, const void *b)
 {
 	spa_error_entry_t *sa = (spa_error_entry_t *)a;
 	spa_error_entry_t *sb = (spa_error_entry_t *)b;
 	int ret;
 
 	ret = bcmp(&sa->se_bookmark, &sb->se_bookmark,
 	    sizeof (zbookmark_t));
 
 	if (ret < 0)
 		return (-1);
 	else if (ret > 0)
 		return (1);
 	else
 		return (0);
 }
 
 /*
  * Utility function which retrieves copies of the current logs and
  * re-initializes them in the process.
  */
 void
 spa_get_errlists(spa_t *spa, avl_tree_t *last, avl_tree_t *scrub)
 {
 	ASSERT(MUTEX_HELD(&spa->spa_errlist_lock));
 
 	bcopy(&spa->spa_errlist_last, last, sizeof (avl_tree_t));
 	bcopy(&spa->spa_errlist_scrub, scrub, sizeof (avl_tree_t));
 
 	avl_create(&spa->spa_errlist_scrub,
 	    spa_error_entry_compare, sizeof (spa_error_entry_t),
 	    offsetof(spa_error_entry_t, se_avl));
 	avl_create(&spa->spa_errlist_last,
 	    spa_error_entry_compare, sizeof (spa_error_entry_t),
 	    offsetof(spa_error_entry_t, se_avl));
 }
 
 static taskq_t *
 spa_taskq_create(spa_t *spa, const char *name, enum zti_modes mode,
     uint_t value)
 {
 	uint_t flags = TASKQ_PREPOPULATE;
 	boolean_t batch = B_FALSE;
 
 	switch (mode) {
 	case zti_mode_null:
 		return (NULL);		/* no taskq needed */
 
 	case zti_mode_fixed:
 		ASSERT3U(value, >=, 1);
 		value = MAX(value, 1);
 		break;
 
 	case zti_mode_batch:
 		batch = B_TRUE;
 		flags |= TASKQ_THREADS_CPU_PCT;
 		value = zio_taskq_batch_pct;
 		break;
 
 	case zti_mode_online_percent:
 		flags |= TASKQ_THREADS_CPU_PCT;
 		break;
 
 	default:
 		panic("unrecognized mode for %s taskq (%u:%u) in "
 		    "spa_activate()",
 		    name, mode, value);
 		break;
 	}
 
 	if (zio_taskq_sysdc && spa->spa_proc != &p0) {
 		if (batch)
 			flags |= TASKQ_DC_BATCH;
 
 		return (taskq_create_sysdc(name, value, 50, INT_MAX,
 		    spa->spa_proc, zio_taskq_basedc, flags));
 	}
 	return (taskq_create_proc(name, value, maxclsyspri, 50, INT_MAX,
 	    spa->spa_proc, flags));
 }
 
 static void
 spa_create_zio_taskqs(spa_t *spa)
 {
 	int t, q;
 
 	for (t = 0; t < ZIO_TYPES; t++) {
 		for (q = 0; q < ZIO_TASKQ_TYPES; q++) {
 			const zio_taskq_info_t *ztip = &zio_taskqs[t][q];
 			enum zti_modes mode = ztip->zti_mode;
 			uint_t value = ztip->zti_value;
 			char name[32];
 
 			(void) snprintf(name, sizeof (name),
 			    "%s_%s", zio_type_name[t], zio_taskq_types[q]);
 
 			spa->spa_zio_taskq[t][q] =
 			    spa_taskq_create(spa, name, mode, value);
 		}
 	}
 }
 
 #if defined(_KERNEL) && defined(HAVE_SPA_THREAD)
 static void
 spa_thread(void *arg)
 {
 	callb_cpr_t cprinfo;
 
 	spa_t *spa = arg;
 	user_t *pu = PTOU(curproc);
 
 	CALLB_CPR_INIT(&cprinfo, &spa->spa_proc_lock, callb_generic_cpr,
 	    spa->spa_name);
 
 	ASSERT(curproc != &p0);
 	(void) snprintf(pu->u_psargs, sizeof (pu->u_psargs),
 	    "zpool-%s", spa->spa_name);
 	(void) strlcpy(pu->u_comm, pu->u_psargs, sizeof (pu->u_comm));
 
 	/* bind this thread to the requested psrset */
 	if (zio_taskq_psrset_bind != PS_NONE) {
 		pool_lock();
 		mutex_enter(&cpu_lock);
 		mutex_enter(&pidlock);
 		mutex_enter(&curproc->p_lock);
 
 		if (cpupart_bind_thread(curthread, zio_taskq_psrset_bind,
 		    0, NULL, NULL) == 0)  {
 			curthread->t_bind_pset = zio_taskq_psrset_bind;
 		} else {
 			cmn_err(CE_WARN,
 			    "Couldn't bind process for zfs pool \"%s\" to "
 			    "pset %d\n", spa->spa_name, zio_taskq_psrset_bind);
 		}
 
 		mutex_exit(&curproc->p_lock);
 		mutex_exit(&pidlock);
 		mutex_exit(&cpu_lock);
 		pool_unlock();
 	}
 
 	if (zio_taskq_sysdc) {
 		sysdc_thread_enter(curthread, 100, 0);
 	}
 
 	spa->spa_proc = curproc;
 	spa->spa_did = curthread->t_did;
 
 	spa_create_zio_taskqs(spa);
 
 	mutex_enter(&spa->spa_proc_lock);
 	ASSERT(spa->spa_proc_state == SPA_PROC_CREATED);
 
 	spa->spa_proc_state = SPA_PROC_ACTIVE;
 	cv_broadcast(&spa->spa_proc_cv);
 
 	CALLB_CPR_SAFE_BEGIN(&cprinfo);
 	while (spa->spa_proc_state == SPA_PROC_ACTIVE)
 		cv_wait(&spa->spa_proc_cv, &spa->spa_proc_lock);
 	CALLB_CPR_SAFE_END(&cprinfo, &spa->spa_proc_lock);
 
 	ASSERT(spa->spa_proc_state == SPA_PROC_DEACTIVATE);
 	spa->spa_proc_state = SPA_PROC_GONE;
 	spa->spa_proc = &p0;
 	cv_broadcast(&spa->spa_proc_cv);
 	CALLB_CPR_EXIT(&cprinfo);	/* drops spa_proc_lock */
 
 	mutex_enter(&curproc->p_lock);
 	lwp_exit();
 }
 #endif
 
 /*
  * Activate an uninitialized pool.
  */
 static void
 spa_activate(spa_t *spa, int mode)
 {
 	ASSERT(spa->spa_state == POOL_STATE_UNINITIALIZED);
 
 	spa->spa_state = POOL_STATE_ACTIVE;
 	spa->spa_mode = mode;
 
 	spa->spa_normal_class = metaslab_class_create(spa, zfs_metaslab_ops);
 	spa->spa_log_class = metaslab_class_create(spa, zfs_metaslab_ops);
 
 	/* Try to create a covering process */
 	mutex_enter(&spa->spa_proc_lock);
 	ASSERT(spa->spa_proc_state == SPA_PROC_NONE);
 	ASSERT(spa->spa_proc == &p0);
 	spa->spa_did = 0;
 
 #ifdef HAVE_SPA_THREAD
 	/* Only create a process if we're going to be around a while. */
 	if (spa_create_process && strcmp(spa->spa_name, TRYIMPORT_NAME) != 0) {
 		if (newproc(spa_thread, (caddr_t)spa, syscid, maxclsyspri,
 		    NULL, 0) == 0) {
 			spa->spa_proc_state = SPA_PROC_CREATED;
 			while (spa->spa_proc_state == SPA_PROC_CREATED) {
 				cv_wait(&spa->spa_proc_cv,
 				    &spa->spa_proc_lock);
 			}
 			ASSERT(spa->spa_proc_state == SPA_PROC_ACTIVE);
 			ASSERT(spa->spa_proc != &p0);
 			ASSERT(spa->spa_did != 0);
 		} else {
 #ifdef _KERNEL
 			cmn_err(CE_WARN,
 			    "Couldn't create process for zfs pool \"%s\"\n",
 			    spa->spa_name);
 #endif
 		}
 	}
 #endif /* HAVE_SPA_THREAD */
 	mutex_exit(&spa->spa_proc_lock);
 
 	/* If we didn't create a process, we need to create our taskqs. */
 	if (spa->spa_proc == &p0) {
 		spa_create_zio_taskqs(spa);
 	}
 
 	list_create(&spa->spa_config_dirty_list, sizeof (vdev_t),
 	    offsetof(vdev_t, vdev_config_dirty_node));
 	list_create(&spa->spa_state_dirty_list, sizeof (vdev_t),
 	    offsetof(vdev_t, vdev_state_dirty_node));
 
 	txg_list_create(&spa->spa_vdev_txg_list,
 	    offsetof(struct vdev, vdev_txg_node));
 
 	avl_create(&spa->spa_errlist_scrub,
 	    spa_error_entry_compare, sizeof (spa_error_entry_t),
 	    offsetof(spa_error_entry_t, se_avl));
 	avl_create(&spa->spa_errlist_last,
 	    spa_error_entry_compare, sizeof (spa_error_entry_t),
 	    offsetof(spa_error_entry_t, se_avl));
 }
 
 /*
  * Opposite of spa_activate().
  */
 static void
 spa_deactivate(spa_t *spa)
 {
 	int t, q;
 
 	ASSERT(spa->spa_sync_on == B_FALSE);
 	ASSERT(spa->spa_dsl_pool == NULL);
 	ASSERT(spa->spa_root_vdev == NULL);
 	ASSERT(spa->spa_async_zio_root == NULL);
 	ASSERT(spa->spa_state != POOL_STATE_UNINITIALIZED);
 
 	txg_list_destroy(&spa->spa_vdev_txg_list);
 
 	list_destroy(&spa->spa_config_dirty_list);
 	list_destroy(&spa->spa_state_dirty_list);
 
 	for (t = 0; t < ZIO_TYPES; t++) {
 		for (q = 0; q < ZIO_TASKQ_TYPES; q++) {
 			if (spa->spa_zio_taskq[t][q] != NULL)
 				taskq_destroy(spa->spa_zio_taskq[t][q]);
 			spa->spa_zio_taskq[t][q] = NULL;
 		}
 	}
 
 	metaslab_class_destroy(spa->spa_normal_class);
 	spa->spa_normal_class = NULL;
 
 	metaslab_class_destroy(spa->spa_log_class);
 	spa->spa_log_class = NULL;
 
 	/*
 	 * If this was part of an import or the open otherwise failed, we may
 	 * still have errors left in the queues.  Empty them just in case.
 	 */
 	spa_errlog_drain(spa);
 
 	avl_destroy(&spa->spa_errlist_scrub);
 	avl_destroy(&spa->spa_errlist_last);
 
 	spa->spa_state = POOL_STATE_UNINITIALIZED;
 
 	mutex_enter(&spa->spa_proc_lock);
 	if (spa->spa_proc_state != SPA_PROC_NONE) {
 		ASSERT(spa->spa_proc_state == SPA_PROC_ACTIVE);
 		spa->spa_proc_state = SPA_PROC_DEACTIVATE;
 		cv_broadcast(&spa->spa_proc_cv);
 		while (spa->spa_proc_state == SPA_PROC_DEACTIVATE) {
 			ASSERT(spa->spa_proc != &p0);
 			cv_wait(&spa->spa_proc_cv, &spa->spa_proc_lock);
 		}
 		ASSERT(spa->spa_proc_state == SPA_PROC_GONE);
 		spa->spa_proc_state = SPA_PROC_NONE;
 	}
 	ASSERT(spa->spa_proc == &p0);
 	mutex_exit(&spa->spa_proc_lock);
 
 	/*
 	 * We want to make sure spa_thread() has actually exited the ZFS
 	 * module, so that the module can't be unloaded out from underneath
 	 * it.
 	 */
 	if (spa->spa_did != 0) {
 		thread_join(spa->spa_did);
 		spa->spa_did = 0;
 	}
 }
 
 /*
  * Verify a pool configuration, and construct the vdev tree appropriately.  This
  * will create all the necessary vdevs in the appropriate layout, with each vdev
  * in the CLOSED state.  This will prep the pool before open/creation/import.
  * All vdev validation is done by the vdev_alloc() routine.
  */
 static int
 spa_config_parse(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent,
     uint_t id, int atype)
 {
 	nvlist_t **child;
 	uint_t children;
 	int error;
 	int c;
 
 	if ((error = vdev_alloc(spa, vdp, nv, parent, id, atype)) != 0)
 		return (error);
 
 	if ((*vdp)->vdev_ops->vdev_op_leaf)
 		return (0);
 
 	error = nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
 	    &child, &children);
 
 	if (error == ENOENT)
 		return (0);
 
 	if (error) {
 		vdev_free(*vdp);
 		*vdp = NULL;
 		return (EINVAL);
 	}
 
 	for (c = 0; c < children; c++) {
 		vdev_t *vd;
 		if ((error = spa_config_parse(spa, &vd, child[c], *vdp, c,
 		    atype)) != 0) {
 			vdev_free(*vdp);
 			*vdp = NULL;
 			return (error);
 		}
 	}
 
 	ASSERT(*vdp != NULL);
 
 	return (0);
 }
 
 /*
  * Opposite of spa_load().
  */
 static void
 spa_unload(spa_t *spa)
 {
 	int i;
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 
 	/*
 	 * Stop async tasks.
 	 */
 	spa_async_suspend(spa);
 
 	/*
 	 * Stop syncing.
 	 */
 	if (spa->spa_sync_on) {
 		txg_sync_stop(spa->spa_dsl_pool);
 		spa->spa_sync_on = B_FALSE;
 	}
 
 	/*
 	 * Wait for any outstanding async I/O to complete.
 	 */
 	if (spa->spa_async_zio_root != NULL) {
 		(void) zio_wait(spa->spa_async_zio_root);
 		spa->spa_async_zio_root = NULL;
 	}
 
 	bpobj_close(&spa->spa_deferred_bpobj);
 
 	/*
 	 * Close the dsl pool.
 	 */
 	if (spa->spa_dsl_pool) {
 		dsl_pool_close(spa->spa_dsl_pool);
 		spa->spa_dsl_pool = NULL;
 		spa->spa_meta_objset = NULL;
 	}
 
 	ddt_unload(spa);
 
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 
 	/*
 	 * Drop and purge level 2 cache
 	 */
 	spa_l2cache_drop(spa);
 
 	/*
 	 * Close all vdevs.
 	 */
 	if (spa->spa_root_vdev)
 		vdev_free(spa->spa_root_vdev);
 	ASSERT(spa->spa_root_vdev == NULL);
 
 	for (i = 0; i < spa->spa_spares.sav_count; i++)
 		vdev_free(spa->spa_spares.sav_vdevs[i]);
 	if (spa->spa_spares.sav_vdevs) {
 		kmem_free(spa->spa_spares.sav_vdevs,
 		    spa->spa_spares.sav_count * sizeof (void *));
 		spa->spa_spares.sav_vdevs = NULL;
 	}
 	if (spa->spa_spares.sav_config) {
 		nvlist_free(spa->spa_spares.sav_config);
 		spa->spa_spares.sav_config = NULL;
 	}
 	spa->spa_spares.sav_count = 0;
 
 	for (i = 0; i < spa->spa_l2cache.sav_count; i++) {
 		vdev_clear_stats(spa->spa_l2cache.sav_vdevs[i]);
 		vdev_free(spa->spa_l2cache.sav_vdevs[i]);
 	}
 	if (spa->spa_l2cache.sav_vdevs) {
 		kmem_free(spa->spa_l2cache.sav_vdevs,
 		    spa->spa_l2cache.sav_count * sizeof (void *));
 		spa->spa_l2cache.sav_vdevs = NULL;
 	}
 	if (spa->spa_l2cache.sav_config) {
 		nvlist_free(spa->spa_l2cache.sav_config);
 		spa->spa_l2cache.sav_config = NULL;
 	}
 	spa->spa_l2cache.sav_count = 0;
 
 	spa->spa_async_suspended = 0;
 
 	if (spa->spa_comment != NULL) {
 		spa_strfree(spa->spa_comment);
 		spa->spa_comment = NULL;
 	}
 
 	spa_config_exit(spa, SCL_ALL, FTAG);
 }
 
 /*
  * Load (or re-load) the current list of vdevs describing the active spares for
  * this pool.  When this is called, we have some form of basic information in
  * 'spa_spares.sav_config'.  We parse this into vdevs, try to open them, and
  * then re-generate a more complete list including status information.
  */
 static void
 spa_load_spares(spa_t *spa)
 {
 	nvlist_t **spares;
 	uint_t nspares;
 	int i;
 	vdev_t *vd, *tvd;
 
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
 	/*
 	 * First, close and free any existing spare vdevs.
 	 */
 	for (i = 0; i < spa->spa_spares.sav_count; i++) {
 		vd = spa->spa_spares.sav_vdevs[i];
 
 		/* Undo the call to spa_activate() below */
 		if ((tvd = spa_lookup_by_guid(spa, vd->vdev_guid,
 		    B_FALSE)) != NULL && tvd->vdev_isspare)
 			spa_spare_remove(tvd);
 		vdev_close(vd);
 		vdev_free(vd);
 	}
 
 	if (spa->spa_spares.sav_vdevs)
 		kmem_free(spa->spa_spares.sav_vdevs,
 		    spa->spa_spares.sav_count * sizeof (void *));
 
 	if (spa->spa_spares.sav_config == NULL)
 		nspares = 0;
 	else
 		VERIFY(nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
 		    ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0);
 
 	spa->spa_spares.sav_count = (int)nspares;
 	spa->spa_spares.sav_vdevs = NULL;
 
 	if (nspares == 0)
 		return;
 
 	/*
 	 * Construct the array of vdevs, opening them to get status in the
 	 * process.   For each spare, there is potentially two different vdev_t
 	 * structures associated with it: one in the list of spares (used only
 	 * for basic validation purposes) and one in the active vdev
 	 * configuration (if it's spared in).  During this phase we open and
 	 * validate each vdev on the spare list.  If the vdev also exists in the
 	 * active configuration, then we also mark this vdev as an active spare.
 	 */
 	spa->spa_spares.sav_vdevs = kmem_alloc(nspares * sizeof (void *),
 	    KM_PUSHPAGE);
 	for (i = 0; i < spa->spa_spares.sav_count; i++) {
 		VERIFY(spa_config_parse(spa, &vd, spares[i], NULL, 0,
 		    VDEV_ALLOC_SPARE) == 0);
 		ASSERT(vd != NULL);
 
 		spa->spa_spares.sav_vdevs[i] = vd;
 
 		if ((tvd = spa_lookup_by_guid(spa, vd->vdev_guid,
 		    B_FALSE)) != NULL) {
 			if (!tvd->vdev_isspare)
 				spa_spare_add(tvd);
 
 			/*
 			 * We only mark the spare active if we were successfully
 			 * able to load the vdev.  Otherwise, importing a pool
 			 * with a bad active spare would result in strange
 			 * behavior, because multiple pool would think the spare
 			 * is actively in use.
 			 *
 			 * There is a vulnerability here to an equally bizarre
 			 * circumstance, where a dead active spare is later
 			 * brought back to life (onlined or otherwise).  Given
 			 * the rarity of this scenario, and the extra complexity
 			 * it adds, we ignore the possibility.
 			 */
 			if (!vdev_is_dead(tvd))
 				spa_spare_activate(tvd);
 		}
 
 		vd->vdev_top = vd;
 		vd->vdev_aux = &spa->spa_spares;
 
 		if (vdev_open(vd) != 0)
 			continue;
 
 		if (vdev_validate_aux(vd) == 0)
 			spa_spare_add(vd);
 	}
 
 	/*
 	 * Recompute the stashed list of spares, with status information
 	 * this time.
 	 */
 	VERIFY(nvlist_remove(spa->spa_spares.sav_config, ZPOOL_CONFIG_SPARES,
 	    DATA_TYPE_NVLIST_ARRAY) == 0);
 
 	spares = kmem_alloc(spa->spa_spares.sav_count * sizeof (void *),
 	    KM_PUSHPAGE);
 	for (i = 0; i < spa->spa_spares.sav_count; i++)
 		spares[i] = vdev_config_generate(spa,
 		    spa->spa_spares.sav_vdevs[i], B_TRUE, VDEV_CONFIG_SPARE);
 	VERIFY(nvlist_add_nvlist_array(spa->spa_spares.sav_config,
 	    ZPOOL_CONFIG_SPARES, spares, spa->spa_spares.sav_count) == 0);
 	for (i = 0; i < spa->spa_spares.sav_count; i++)
 		nvlist_free(spares[i]);
 	kmem_free(spares, spa->spa_spares.sav_count * sizeof (void *));
 }
 
 /*
  * Load (or re-load) the current list of vdevs describing the active l2cache for
  * this pool.  When this is called, we have some form of basic information in
  * 'spa_l2cache.sav_config'.  We parse this into vdevs, try to open them, and
  * then re-generate a more complete list including status information.
  * Devices which are already active have their details maintained, and are
  * not re-opened.
  */
 static void
 spa_load_l2cache(spa_t *spa)
 {
 	nvlist_t **l2cache;
 	uint_t nl2cache;
 	int i, j, oldnvdevs;
 	uint64_t guid;
 	vdev_t *vd, **oldvdevs, **newvdevs = NULL;
 	spa_aux_vdev_t *sav = &spa->spa_l2cache;
 
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
 	if (sav->sav_config != NULL) {
 		VERIFY(nvlist_lookup_nvlist_array(sav->sav_config,
 		    ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0);
 		newvdevs = kmem_alloc(nl2cache * sizeof (void *), KM_PUSHPAGE);
 	} else {
 		nl2cache = 0;
 	}
 
 	oldvdevs = sav->sav_vdevs;
 	oldnvdevs = sav->sav_count;
 	sav->sav_vdevs = NULL;
 	sav->sav_count = 0;
 
 	/*
 	 * Process new nvlist of vdevs.
 	 */
 	for (i = 0; i < nl2cache; i++) {
 		VERIFY(nvlist_lookup_uint64(l2cache[i], ZPOOL_CONFIG_GUID,
 		    &guid) == 0);
 
 		newvdevs[i] = NULL;
 		for (j = 0; j < oldnvdevs; j++) {
 			vd = oldvdevs[j];
 			if (vd != NULL && guid == vd->vdev_guid) {
 				/*
 				 * Retain previous vdev for add/remove ops.
 				 */
 				newvdevs[i] = vd;
 				oldvdevs[j] = NULL;
 				break;
 			}
 		}
 
 		if (newvdevs[i] == NULL) {
 			/*
 			 * Create new vdev
 			 */
 			VERIFY(spa_config_parse(spa, &vd, l2cache[i], NULL, 0,
 			    VDEV_ALLOC_L2CACHE) == 0);
 			ASSERT(vd != NULL);
 			newvdevs[i] = vd;
 
 			/*
 			 * Commit this vdev as an l2cache device,
 			 * even if it fails to open.
 			 */
 			spa_l2cache_add(vd);
 
 			vd->vdev_top = vd;
 			vd->vdev_aux = sav;
 
 			spa_l2cache_activate(vd);
 
 			if (vdev_open(vd) != 0)
 				continue;
 
 			(void) vdev_validate_aux(vd);
 
 			if (!vdev_is_dead(vd))
 				l2arc_add_vdev(spa, vd);
 		}
 	}
 
 	/*
 	 * Purge vdevs that were dropped
 	 */
 	for (i = 0; i < oldnvdevs; i++) {
 		uint64_t pool;
 
 		vd = oldvdevs[i];
 		if (vd != NULL) {
 			ASSERT(vd->vdev_isl2cache);
 
 			if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
 			    pool != 0ULL && l2arc_vdev_present(vd))
 				l2arc_remove_vdev(vd);
 			vdev_clear_stats(vd);
 			vdev_free(vd);
 		}
 	}
 
 	if (oldvdevs)
 		kmem_free(oldvdevs, oldnvdevs * sizeof (void *));
 
 	if (sav->sav_config == NULL)
 		goto out;
 
 	sav->sav_vdevs = newvdevs;
 	sav->sav_count = (int)nl2cache;
 
 	/*
 	 * Recompute the stashed list of l2cache devices, with status
 	 * information this time.
 	 */
 	VERIFY(nvlist_remove(sav->sav_config, ZPOOL_CONFIG_L2CACHE,
 	    DATA_TYPE_NVLIST_ARRAY) == 0);
 
 	l2cache = kmem_alloc(sav->sav_count * sizeof (void *), KM_PUSHPAGE);
 	for (i = 0; i < sav->sav_count; i++)
 		l2cache[i] = vdev_config_generate(spa,
 		    sav->sav_vdevs[i], B_TRUE, VDEV_CONFIG_L2CACHE);
 	VERIFY(nvlist_add_nvlist_array(sav->sav_config,
 	    ZPOOL_CONFIG_L2CACHE, l2cache, sav->sav_count) == 0);
 out:
 	for (i = 0; i < sav->sav_count; i++)
 		nvlist_free(l2cache[i]);
 	if (sav->sav_count)
 		kmem_free(l2cache, sav->sav_count * sizeof (void *));
 }
 
 static int
 load_nvlist(spa_t *spa, uint64_t obj, nvlist_t **value)
 {
 	dmu_buf_t *db;
 	char *packed = NULL;
 	size_t nvsize = 0;
 	int error;
 	*value = NULL;
 
-	VERIFY(0 == dmu_bonus_hold(spa->spa_meta_objset, obj, FTAG, &db));
+	error = dmu_bonus_hold(spa->spa_meta_objset, obj, FTAG, &db);
+	if (error)
+		return (error);
+
 	nvsize = *(uint64_t *)db->db_data;
 	dmu_buf_rele(db, FTAG);
 
 	packed = kmem_alloc(nvsize, KM_PUSHPAGE | KM_NODEBUG);
 	error = dmu_read(spa->spa_meta_objset, obj, 0, nvsize, packed,
 	    DMU_READ_PREFETCH);
 	if (error == 0)
 		error = nvlist_unpack(packed, nvsize, value, 0);
 	kmem_free(packed, nvsize);
 
 	return (error);
 }
 
 /*
  * Checks to see if the given vdev could not be opened, in which case we post a
  * sysevent to notify the autoreplace code that the device has been removed.
  */
 static void
 spa_check_removed(vdev_t *vd)
 {
 	int c;
 
 	for (c = 0; c < vd->vdev_children; c++)
 		spa_check_removed(vd->vdev_child[c]);
 
 	if (vd->vdev_ops->vdev_op_leaf && vdev_is_dead(vd)) {
 		zfs_ereport_post(FM_EREPORT_RESOURCE_AUTOREPLACE,
 		    vd->vdev_spa, vd, NULL, 0, 0);
 		spa_event_notify(vd->vdev_spa, vd, FM_EREPORT_ZFS_DEVICE_CHECK);
 	}
 }
 
 /*
  * Validate the current config against the MOS config
  */
 static boolean_t
 spa_config_valid(spa_t *spa, nvlist_t *config)
 {
 	vdev_t *mrvd, *rvd = spa->spa_root_vdev;
 	nvlist_t *nv;
 	int c, i;
 
 	VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &nv) == 0);
 
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	VERIFY(spa_config_parse(spa, &mrvd, nv, NULL, 0, VDEV_ALLOC_LOAD) == 0);
 
 	ASSERT3U(rvd->vdev_children, ==, mrvd->vdev_children);
 
 	/*
 	 * If we're doing a normal import, then build up any additional
 	 * diagnostic information about missing devices in this config.
 	 * We'll pass this up to the user for further processing.
 	 */
 	if (!(spa->spa_import_flags & ZFS_IMPORT_MISSING_LOG)) {
 		nvlist_t **child, *nv;
 		uint64_t idx = 0;
 
 		child = kmem_alloc(rvd->vdev_children * sizeof (nvlist_t **),
 		    KM_PUSHPAGE);
 		VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 
 		for (c = 0; c < rvd->vdev_children; c++) {
 			vdev_t *tvd = rvd->vdev_child[c];
 			vdev_t *mtvd  = mrvd->vdev_child[c];
 
 			if (tvd->vdev_ops == &vdev_missing_ops &&
 			    mtvd->vdev_ops != &vdev_missing_ops &&
 			    mtvd->vdev_islog)
 				child[idx++] = vdev_config_generate(spa, mtvd,
 				    B_FALSE, 0);
 		}
 
 		if (idx) {
 			VERIFY(nvlist_add_nvlist_array(nv,
 			    ZPOOL_CONFIG_CHILDREN, child, idx) == 0);
 			VERIFY(nvlist_add_nvlist(spa->spa_load_info,
 			    ZPOOL_CONFIG_MISSING_DEVICES, nv) == 0);
 
 			for (i = 0; i < idx; i++)
 				nvlist_free(child[i]);
 		}
 		nvlist_free(nv);
 		kmem_free(child, rvd->vdev_children * sizeof (char **));
 	}
 
 	/*
 	 * Compare the root vdev tree with the information we have
 	 * from the MOS config (mrvd). Check each top-level vdev
 	 * with the corresponding MOS config top-level (mtvd).
 	 */
 	for (c = 0; c < rvd->vdev_children; c++) {
 		vdev_t *tvd = rvd->vdev_child[c];
 		vdev_t *mtvd  = mrvd->vdev_child[c];
 
 		/*
 		 * Resolve any "missing" vdevs in the current configuration.
 		 * If we find that the MOS config has more accurate information
 		 * about the top-level vdev then use that vdev instead.
 		 */
 		if (tvd->vdev_ops == &vdev_missing_ops &&
 		    mtvd->vdev_ops != &vdev_missing_ops) {
 
 			if (!(spa->spa_import_flags & ZFS_IMPORT_MISSING_LOG))
 				continue;
 
 			/*
 			 * Device specific actions.
 			 */
 			if (mtvd->vdev_islog) {
 				spa_set_log_state(spa, SPA_LOG_CLEAR);
 			} else {
 				/*
 				 * XXX - once we have 'readonly' pool
 				 * support we should be able to handle
 				 * missing data devices by transitioning
 				 * the pool to readonly.
 				 */
 				continue;
 			}
 
 			/*
 			 * Swap the missing vdev with the data we were
 			 * able to obtain from the MOS config.
 			 */
 			vdev_remove_child(rvd, tvd);
 			vdev_remove_child(mrvd, mtvd);
 
 			vdev_add_child(rvd, mtvd);
 			vdev_add_child(mrvd, tvd);
 
 			spa_config_exit(spa, SCL_ALL, FTAG);
 			vdev_load(mtvd);
 			spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 
 			vdev_reopen(rvd);
 		} else if (mtvd->vdev_islog) {
 			/*
 			 * Load the slog device's state from the MOS config
 			 * since it's possible that the label does not
 			 * contain the most up-to-date information.
 			 */
 			vdev_load_log_state(tvd, mtvd);
 			vdev_reopen(tvd);
 		}
 	}
 	vdev_free(mrvd);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	/*
 	 * Ensure we were able to validate the config.
 	 */
 	return (rvd->vdev_guid_sum == spa->spa_uberblock.ub_guid_sum);
 }
 
 /*
  * Check for missing log devices
  */
 static int
 spa_check_logs(spa_t *spa)
 {
 	switch (spa->spa_log_state) {
 	default:
 		break;
 	case SPA_LOG_MISSING:
 		/* need to recheck in case slog has been restored */
 	case SPA_LOG_UNKNOWN:
 		if (dmu_objset_find(spa->spa_name, zil_check_log_chain, NULL,
 		    DS_FIND_CHILDREN)) {
 			spa_set_log_state(spa, SPA_LOG_MISSING);
 			return (1);
 		}
 		break;
 	}
 	return (0);
 }
 
 static boolean_t
 spa_passivate_log(spa_t *spa)
 {
 	vdev_t *rvd = spa->spa_root_vdev;
 	boolean_t slog_found = B_FALSE;
 	int c;
 
 	ASSERT(spa_config_held(spa, SCL_ALLOC, RW_WRITER));
 
 	if (!spa_has_slogs(spa))
 		return (B_FALSE);
 
 	for (c = 0; c < rvd->vdev_children; c++) {
 		vdev_t *tvd = rvd->vdev_child[c];
 		metaslab_group_t *mg = tvd->vdev_mg;
 
 		if (tvd->vdev_islog) {
 			metaslab_group_passivate(mg);
 			slog_found = B_TRUE;
 		}
 	}
 
 	return (slog_found);
 }
 
 static void
 spa_activate_log(spa_t *spa)
 {
 	vdev_t *rvd = spa->spa_root_vdev;
 	int c;
 
 	ASSERT(spa_config_held(spa, SCL_ALLOC, RW_WRITER));
 
 	for (c = 0; c < rvd->vdev_children; c++) {
 		vdev_t *tvd = rvd->vdev_child[c];
 		metaslab_group_t *mg = tvd->vdev_mg;
 
 		if (tvd->vdev_islog)
 			metaslab_group_activate(mg);
 	}
 }
 
 int
 spa_offline_log(spa_t *spa)
 {
 	int error = 0;
 
 	if ((error = dmu_objset_find(spa_name(spa), zil_vdev_offline,
 	    NULL, DS_FIND_CHILDREN)) == 0) {
 
 		/*
 		 * We successfully offlined the log device, sync out the
 		 * current txg so that the "stubby" block can be removed
 		 * by zil_sync().
 		 */
 		txg_wait_synced(spa->spa_dsl_pool, 0);
 	}
 	return (error);
 }
 
 static void
 spa_aux_check_removed(spa_aux_vdev_t *sav)
 {
 	int i;
 
 	for (i = 0; i < sav->sav_count; i++)
 		spa_check_removed(sav->sav_vdevs[i]);
 }
 
 void
 spa_claim_notify(zio_t *zio)
 {
 	spa_t *spa = zio->io_spa;
 
 	if (zio->io_error)
 		return;
 
 	mutex_enter(&spa->spa_props_lock);	/* any mutex will do */
 	if (spa->spa_claim_max_txg < zio->io_bp->blk_birth)
 		spa->spa_claim_max_txg = zio->io_bp->blk_birth;
 	mutex_exit(&spa->spa_props_lock);
 }
 
 typedef struct spa_load_error {
 	uint64_t	sle_meta_count;
 	uint64_t	sle_data_count;
 } spa_load_error_t;
 
 static void
 spa_load_verify_done(zio_t *zio)
 {
 	blkptr_t *bp = zio->io_bp;
 	spa_load_error_t *sle = zio->io_private;
 	dmu_object_type_t type = BP_GET_TYPE(bp);
 	int error = zio->io_error;
 
 	if (error) {
 		if ((BP_GET_LEVEL(bp) != 0 || dmu_ot[type].ot_metadata) &&
 		    type != DMU_OT_INTENT_LOG)
 			atomic_add_64(&sle->sle_meta_count, 1);
 		else
 			atomic_add_64(&sle->sle_data_count, 1);
 	}
 	zio_data_buf_free(zio->io_data, zio->io_size);
 }
 
 /*ARGSUSED*/
 static int
 spa_load_verify_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
     arc_buf_t *pbuf, const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
 	if (bp != NULL) {
 		zio_t *rio = arg;
 		size_t size = BP_GET_PSIZE(bp);
 		void *data = zio_data_buf_alloc(size);
 
 		zio_nowait(zio_read(rio, spa, bp, data, size,
 		    spa_load_verify_done, rio->io_private, ZIO_PRIORITY_SCRUB,
 		    ZIO_FLAG_SPECULATIVE | ZIO_FLAG_CANFAIL |
 		    ZIO_FLAG_SCRUB | ZIO_FLAG_RAW, zb));
 	}
 	return (0);
 }
 
 static int
 spa_load_verify(spa_t *spa)
 {
 	zio_t *rio;
 	spa_load_error_t sle = { 0 };
 	zpool_rewind_policy_t policy;
 	boolean_t verify_ok = B_FALSE;
 	int error;
 
 	zpool_get_rewind_policy(spa->spa_config, &policy);
 
 	if (policy.zrp_request & ZPOOL_NEVER_REWIND)
 		return (0);
 
 	rio = zio_root(spa, NULL, &sle,
 	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE);
 
 	error = traverse_pool(spa, spa->spa_verify_min_txg,
 	    TRAVERSE_PRE | TRAVERSE_PREFETCH, spa_load_verify_cb, rio);
 
 	(void) zio_wait(rio);
 
 	spa->spa_load_meta_errors = sle.sle_meta_count;
 	spa->spa_load_data_errors = sle.sle_data_count;
 
 	if (!error && sle.sle_meta_count <= policy.zrp_maxmeta &&
 	    sle.sle_data_count <= policy.zrp_maxdata) {
 		int64_t loss = 0;
 
 		verify_ok = B_TRUE;
 		spa->spa_load_txg = spa->spa_uberblock.ub_txg;
 		spa->spa_load_txg_ts = spa->spa_uberblock.ub_timestamp;
 
 		loss = spa->spa_last_ubsync_txg_ts - spa->spa_load_txg_ts;
 		VERIFY(nvlist_add_uint64(spa->spa_load_info,
 		    ZPOOL_CONFIG_LOAD_TIME, spa->spa_load_txg_ts) == 0);
 		VERIFY(nvlist_add_int64(spa->spa_load_info,
 		    ZPOOL_CONFIG_REWIND_TIME, loss) == 0);
 		VERIFY(nvlist_add_uint64(spa->spa_load_info,
 		    ZPOOL_CONFIG_LOAD_DATA_ERRORS, sle.sle_data_count) == 0);
 	} else {
 		spa->spa_load_max_txg = spa->spa_uberblock.ub_txg;
 	}
 
 	if (error) {
 		if (error != ENXIO && error != EIO)
 			error = EIO;
 		return (error);
 	}
 
 	return (verify_ok ? 0 : EIO);
 }
 
 /*
  * Find a value in the pool props object.
  */
 static void
 spa_prop_find(spa_t *spa, zpool_prop_t prop, uint64_t *val)
 {
 	(void) zap_lookup(spa->spa_meta_objset, spa->spa_pool_props_object,
 	    zpool_prop_to_name(prop), sizeof (uint64_t), 1, val);
 }
 
 /*
  * Find a value in the pool directory object.
  */
 static int
 spa_dir_prop(spa_t *spa, const char *name, uint64_t *val)
 {
 	return (zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
 	    name, sizeof (uint64_t), 1, val));
 }
 
 static int
 spa_vdev_err(vdev_t *vdev, vdev_aux_t aux, int err)
 {
 	vdev_set_state(vdev, B_TRUE, VDEV_STATE_CANT_OPEN, aux);
 	return (err);
 }
 
 /*
  * Fix up config after a partly-completed split.  This is done with the
  * ZPOOL_CONFIG_SPLIT nvlist.  Both the splitting pool and the split-off
  * pool have that entry in their config, but only the splitting one contains
  * a list of all the guids of the vdevs that are being split off.
  *
  * This function determines what to do with that list: either rejoin
  * all the disks to the pool, or complete the splitting process.  To attempt
  * the rejoin, each disk that is offlined is marked online again, and
  * we do a reopen() call.  If the vdev label for every disk that was
  * marked online indicates it was successfully split off (VDEV_AUX_SPLIT_POOL)
  * then we call vdev_split() on each disk, and complete the split.
  *
  * Otherwise we leave the config alone, with all the vdevs in place in
  * the original pool.
  */
 static void
 spa_try_repair(spa_t *spa, nvlist_t *config)
 {
 	uint_t extracted;
 	uint64_t *glist;
 	uint_t i, gcount;
 	nvlist_t *nvl;
 	vdev_t **vd;
 	boolean_t attempt_reopen;
 
 	if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_SPLIT, &nvl) != 0)
 		return;
 
 	/* check that the config is complete */
 	if (nvlist_lookup_uint64_array(nvl, ZPOOL_CONFIG_SPLIT_LIST,
 	    &glist, &gcount) != 0)
 		return;
 
 	vd = kmem_zalloc(gcount * sizeof (vdev_t *), KM_PUSHPAGE);
 
 	/* attempt to online all the vdevs & validate */
 	attempt_reopen = B_TRUE;
 	for (i = 0; i < gcount; i++) {
 		if (glist[i] == 0)	/* vdev is hole */
 			continue;
 
 		vd[i] = spa_lookup_by_guid(spa, glist[i], B_FALSE);
 		if (vd[i] == NULL) {
 			/*
 			 * Don't bother attempting to reopen the disks;
 			 * just do the split.
 			 */
 			attempt_reopen = B_FALSE;
 		} else {
 			/* attempt to re-online it */
 			vd[i]->vdev_offline = B_FALSE;
 		}
 	}
 
 	if (attempt_reopen) {
 		vdev_reopen(spa->spa_root_vdev);
 
 		/* check each device to see what state it's in */
 		for (extracted = 0, i = 0; i < gcount; i++) {
 			if (vd[i] != NULL &&
 			    vd[i]->vdev_stat.vs_aux != VDEV_AUX_SPLIT_POOL)
 				break;
 			++extracted;
 		}
 	}
 
 	/*
 	 * If every disk has been moved to the new pool, or if we never
 	 * even attempted to look at them, then we split them off for
 	 * good.
 	 */
 	if (!attempt_reopen || gcount == extracted) {
 		for (i = 0; i < gcount; i++)
 			if (vd[i] != NULL)
 				vdev_split(vd[i]);
 		vdev_reopen(spa->spa_root_vdev);
 	}
 
 	kmem_free(vd, gcount * sizeof (vdev_t *));
 }
 
 static int
 spa_load(spa_t *spa, spa_load_state_t state, spa_import_type_t type,
     boolean_t mosconfig)
 {
 	nvlist_t *config = spa->spa_config;
 	char *ereport = FM_EREPORT_ZFS_POOL;
 	char *comment;
 	int error;
 	uint64_t pool_guid;
 	nvlist_t *nvl;
 
 	if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID, &pool_guid))
 		return (EINVAL);
 
 	ASSERT(spa->spa_comment == NULL);
 	if (nvlist_lookup_string(config, ZPOOL_CONFIG_COMMENT, &comment) == 0)
 		spa->spa_comment = spa_strdup(comment);
 
 	/*
 	 * Versioning wasn't explicitly added to the label until later, so if
 	 * it's not present treat it as the initial version.
 	 */
 	if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_VERSION,
 	    &spa->spa_ubsync.ub_version) != 0)
 		spa->spa_ubsync.ub_version = SPA_VERSION_INITIAL;
 
 	(void) nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG,
 	    &spa->spa_config_txg);
 
 	if ((state == SPA_LOAD_IMPORT || state == SPA_LOAD_TRYIMPORT) &&
 	    spa_guid_exists(pool_guid, 0)) {
 		error = EEXIST;
 	} else {
 		spa->spa_config_guid = pool_guid;
 
 		if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_SPLIT,
 		    &nvl) == 0) {
 			VERIFY(nvlist_dup(nvl, &spa->spa_config_splitting,
 			    KM_PUSHPAGE) == 0);
 		}
 
 		gethrestime(&spa->spa_loaded_ts);
 		error = spa_load_impl(spa, pool_guid, config, state, type,
 		    mosconfig, &ereport);
 	}
 
 	spa->spa_minref = refcount_count(&spa->spa_refcount);
 	if (error) {
 		if (error != EEXIST) {
 			spa->spa_loaded_ts.tv_sec = 0;
 			spa->spa_loaded_ts.tv_nsec = 0;
 		}
 		if (error != EBADF) {
 			zfs_ereport_post(ereport, spa, NULL, NULL, 0, 0);
 		}
 	}
 	spa->spa_load_state = error ? SPA_LOAD_ERROR : SPA_LOAD_NONE;
 	spa->spa_ena = 0;
 
 	return (error);
 }
 
 /*
  * Load an existing storage pool, using the pool's builtin spa_config as a
  * source of configuration information.
  */
 __attribute__((always_inline))
 static inline int
 spa_load_impl(spa_t *spa, uint64_t pool_guid, nvlist_t *config,
     spa_load_state_t state, spa_import_type_t type, boolean_t mosconfig,
     char **ereport)
 {
 	int error = 0;
 	nvlist_t *nvroot = NULL;
 	vdev_t *rvd;
 	uberblock_t *ub = &spa->spa_uberblock;
 	uint64_t children, config_cache_txg = spa->spa_config_txg;
 	int orig_mode = spa->spa_mode;
 	int parse;
 	uint64_t obj;
 
 	/*
 	 * If this is an untrusted config, access the pool in read-only mode.
 	 * This prevents things like resilvering recently removed devices.
 	 */
 	if (!mosconfig)
 		spa->spa_mode = FREAD;
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 
 	spa->spa_load_state = state;
 
 	if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &nvroot))
 		return (EINVAL);
 
 	parse = (type == SPA_IMPORT_EXISTING ?
 	    VDEV_ALLOC_LOAD : VDEV_ALLOC_SPLIT);
 
 	/*
 	 * Create "The Godfather" zio to hold all async IOs
 	 */
 	spa->spa_async_zio_root = zio_root(spa, NULL, NULL,
 	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_GODFATHER);
 
 	/*
 	 * Parse the configuration into a vdev tree.  We explicitly set the
 	 * value that will be returned by spa_version() since parsing the
 	 * configuration requires knowing the version number.
 	 */
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	error = spa_config_parse(spa, &rvd, nvroot, NULL, 0, parse);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	if (error != 0)
 		return (error);
 
 	ASSERT(spa->spa_root_vdev == rvd);
 
 	if (type != SPA_IMPORT_ASSEMBLE) {
 		ASSERT(spa_guid(spa) == pool_guid);
 	}
 
 	/*
 	 * Try to open all vdevs, loading each label in the process.
 	 */
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	error = vdev_open(rvd);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 	if (error != 0)
 		return (error);
 
 	/*
 	 * We need to validate the vdev labels against the configuration that
 	 * we have in hand, which is dependent on the setting of mosconfig. If
 	 * mosconfig is true then we're validating the vdev labels based on
 	 * that config.  Otherwise, we're validating against the cached config
 	 * (zpool.cache) that was read when we loaded the zfs module, and then
 	 * later we will recursively call spa_load() and validate against
 	 * the vdev config.
 	 *
 	 * If we're assembling a new pool that's been split off from an
 	 * existing pool, the labels haven't yet been updated so we skip
 	 * validation for now.
 	 */
 	if (type != SPA_IMPORT_ASSEMBLE) {
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		error = vdev_validate(rvd, mosconfig);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 
 		if (error != 0)
 			return (error);
 
 		if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN)
 			return (ENXIO);
 	}
 
 	/*
 	 * Find the best uberblock.
 	 */
 	vdev_uberblock_load(NULL, rvd, ub);
 
 	/*
 	 * If we weren't able to find a single valid uberblock, return failure.
 	 */
 	if (ub->ub_txg == 0)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, ENXIO));
 
 	/*
 	 * If the pool is newer than the code, we can't open it.
 	 */
 	if (ub->ub_version > SPA_VERSION)
 		return (spa_vdev_err(rvd, VDEV_AUX_VERSION_NEWER, ENOTSUP));
 
 	/*
 	 * If the vdev guid sum doesn't match the uberblock, we have an
 	 * incomplete configuration.  We first check to see if the pool
 	 * is aware of the complete config (i.e ZPOOL_CONFIG_VDEV_CHILDREN).
 	 * If it is, defer the vdev_guid_sum check till later so we
 	 * can handle missing vdevs.
 	 */
 	if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_VDEV_CHILDREN,
 	    &children) != 0 && mosconfig && type != SPA_IMPORT_ASSEMBLE &&
 	    rvd->vdev_guid_sum != ub->ub_guid_sum)
 		return (spa_vdev_err(rvd, VDEV_AUX_BAD_GUID_SUM, ENXIO));
 
 	if (type != SPA_IMPORT_ASSEMBLE && spa->spa_config_splitting) {
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_try_repair(spa, config);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 		nvlist_free(spa->spa_config_splitting);
 		spa->spa_config_splitting = NULL;
 	}
 
 	/*
 	 * Initialize internal SPA structures.
 	 */
 	spa->spa_state = POOL_STATE_ACTIVE;
 	spa->spa_ubsync = spa->spa_uberblock;
 	spa->spa_verify_min_txg = spa->spa_extreme_rewind ?
 	    TXG_INITIAL - 1 : spa_last_synced_txg(spa) - TXG_DEFER_SIZE - 1;
 	spa->spa_first_txg = spa->spa_last_ubsync_txg ?
 	    spa->spa_last_ubsync_txg : spa_last_synced_txg(spa) + 1;
 	spa->spa_claim_max_txg = spa->spa_first_txg;
 	spa->spa_prev_software_version = ub->ub_software_version;
 
 	error = dsl_pool_open(spa, spa->spa_first_txg, &spa->spa_dsl_pool);
 	if (error)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 	spa->spa_meta_objset = spa->spa_dsl_pool->dp_meta_objset;
 
 	if (spa_dir_prop(spa, DMU_POOL_CONFIG, &spa->spa_config_object) != 0)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	if (!mosconfig) {
 		uint64_t hostid;
 		nvlist_t *policy = NULL, *nvconfig;
 
 		if (load_nvlist(spa, spa->spa_config_object, &nvconfig) != 0)
 			return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 		if (!spa_is_root(spa) && nvlist_lookup_uint64(nvconfig,
 		    ZPOOL_CONFIG_HOSTID, &hostid) == 0) {
 			char *hostname;
 			unsigned long myhostid = 0;
 
 			VERIFY(nvlist_lookup_string(nvconfig,
 			    ZPOOL_CONFIG_HOSTNAME, &hostname) == 0);
 
 #ifdef	_KERNEL
 			myhostid = zone_get_hostid(NULL);
 #else	/* _KERNEL */
 			/*
 			 * We're emulating the system's hostid in userland, so
 			 * we can't use zone_get_hostid().
 			 */
 			(void) ddi_strtoul(hw_serial, NULL, 10, &myhostid);
 #endif	/* _KERNEL */
 			if (hostid != 0 && myhostid != 0 &&
 			    hostid != myhostid) {
 				nvlist_free(nvconfig);
 				cmn_err(CE_WARN, "pool '%s' could not be "
 				    "loaded as it was last accessed by "
 				    "another system (host: %s hostid: 0x%lx). "
 				    "See: http://zfsonlinux.org/msg/ZFS-8000-EY",
 				    spa_name(spa), hostname,
 				    (unsigned long)hostid);
 				return (EBADF);
 			}
 		}
 		if (nvlist_lookup_nvlist(spa->spa_config,
 		    ZPOOL_REWIND_POLICY, &policy) == 0)
 			VERIFY(nvlist_add_nvlist(nvconfig,
 			    ZPOOL_REWIND_POLICY, policy) == 0);
 
 		spa_config_set(spa, nvconfig);
 		spa_unload(spa);
 		spa_deactivate(spa);
 		spa_activate(spa, orig_mode);
 
 		return (spa_load(spa, state, SPA_IMPORT_EXISTING, B_TRUE));
 	}
 
 	if (spa_dir_prop(spa, DMU_POOL_SYNC_BPOBJ, &obj) != 0)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 	error = bpobj_open(&spa->spa_deferred_bpobj, spa->spa_meta_objset, obj);
 	if (error != 0)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	/*
 	 * Load the bit that tells us to use the new accounting function
 	 * (raid-z deflation).  If we have an older pool, this will not
 	 * be present.
 	 */
 	error = spa_dir_prop(spa, DMU_POOL_DEFLATE, &spa->spa_deflate);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	error = spa_dir_prop(spa, DMU_POOL_CREATION_VERSION,
 	    &spa->spa_creation_version);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	/*
 	 * Load the persistent error log.  If we have an older pool, this will
 	 * not be present.
 	 */
 	error = spa_dir_prop(spa, DMU_POOL_ERRLOG_LAST, &spa->spa_errlog_last);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	error = spa_dir_prop(spa, DMU_POOL_ERRLOG_SCRUB,
 	    &spa->spa_errlog_scrub);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	/*
 	 * Load the history object.  If we have an older pool, this
 	 * will not be present.
 	 */
 	error = spa_dir_prop(spa, DMU_POOL_HISTORY, &spa->spa_history);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	/*
 	 * If we're assembling the pool from the split-off vdevs of
 	 * an existing pool, we don't want to attach the spares & cache
 	 * devices.
 	 */
 
 	/*
 	 * Load any hot spares for this pool.
 	 */
 	error = spa_dir_prop(spa, DMU_POOL_SPARES, &spa->spa_spares.sav_object);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 	if (error == 0 && type != SPA_IMPORT_ASSEMBLE) {
 		ASSERT(spa_version(spa) >= SPA_VERSION_SPARES);
 		if (load_nvlist(spa, spa->spa_spares.sav_object,
 		    &spa->spa_spares.sav_config) != 0)
 			return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_load_spares(spa);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 	} else if (error == 0) {
 		spa->spa_spares.sav_sync = B_TRUE;
 	}
 
 	/*
 	 * Load any level 2 ARC devices for this pool.
 	 */
 	error = spa_dir_prop(spa, DMU_POOL_L2CACHE,
 	    &spa->spa_l2cache.sav_object);
 	if (error != 0 && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 	if (error == 0 && type != SPA_IMPORT_ASSEMBLE) {
 		ASSERT(spa_version(spa) >= SPA_VERSION_L2CACHE);
 		if (load_nvlist(spa, spa->spa_l2cache.sav_object,
 		    &spa->spa_l2cache.sav_config) != 0)
 			return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_load_l2cache(spa);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 	} else if (error == 0) {
 		spa->spa_l2cache.sav_sync = B_TRUE;
 	}
 
 	spa->spa_delegation = zpool_prop_default_numeric(ZPOOL_PROP_DELEGATION);
 
 	error = spa_dir_prop(spa, DMU_POOL_PROPS, &spa->spa_pool_props_object);
 	if (error && error != ENOENT)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	if (error == 0) {
 		uint64_t autoreplace;
 
 		spa_prop_find(spa, ZPOOL_PROP_BOOTFS, &spa->spa_bootfs);
 		spa_prop_find(spa, ZPOOL_PROP_AUTOREPLACE, &autoreplace);
 		spa_prop_find(spa, ZPOOL_PROP_DELEGATION, &spa->spa_delegation);
 		spa_prop_find(spa, ZPOOL_PROP_FAILUREMODE, &spa->spa_failmode);
 		spa_prop_find(spa, ZPOOL_PROP_AUTOEXPAND, &spa->spa_autoexpand);
 		spa_prop_find(spa, ZPOOL_PROP_DEDUPDITTO,
 		    &spa->spa_dedup_ditto);
 
 		spa->spa_autoreplace = (autoreplace != 0);
 	}
 
 	/*
 	 * If the 'autoreplace' property is set, then post a resource notifying
 	 * the ZFS DE that it should not issue any faults for unopenable
 	 * devices.  We also iterate over the vdevs, and post a sysevent for any
 	 * unopenable vdevs so that the normal autoreplace handler can take
 	 * over.
 	 */
 	if (spa->spa_autoreplace && state != SPA_LOAD_TRYIMPORT) {
 		spa_check_removed(spa->spa_root_vdev);
 		/*
 		 * For the import case, this is done in spa_import(), because
 		 * at this point we're using the spare definitions from
 		 * the MOS config, not necessarily from the userland config.
 		 */
 		if (state != SPA_LOAD_IMPORT) {
 			spa_aux_check_removed(&spa->spa_spares);
 			spa_aux_check_removed(&spa->spa_l2cache);
 		}
 	}
 
 	/*
 	 * Load the vdev state for all toplevel vdevs.
 	 */
 	vdev_load(rvd);
 
 	/*
 	 * Propagate the leaf DTLs we just loaded all the way up the tree.
 	 */
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	vdev_dtl_reassess(rvd, 0, 0, B_FALSE);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	/*
 	 * Load the DDTs (dedup tables).
 	 */
 	error = ddt_load(spa);
 	if (error != 0)
 		return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 	spa_update_dspace(spa);
 
 	/*
 	 * Validate the config, using the MOS config to fill in any
 	 * information which might be missing.  If we fail to validate
 	 * the config then declare the pool unfit for use. If we're
 	 * assembling a pool from a split, the log is not transferred
 	 * over.
 	 */
 	if (type != SPA_IMPORT_ASSEMBLE) {
 		nvlist_t *nvconfig;
 
 		if (load_nvlist(spa, spa->spa_config_object, &nvconfig) != 0)
 			return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA, EIO));
 
 		if (!spa_config_valid(spa, nvconfig)) {
 			nvlist_free(nvconfig);
 			return (spa_vdev_err(rvd, VDEV_AUX_BAD_GUID_SUM,
 			    ENXIO));
 		}
 		nvlist_free(nvconfig);
 
 		/*
 		 * Now that we've validate the config, check the state of the
 		 * root vdev.  If it can't be opened, it indicates one or
 		 * more toplevel vdevs are faulted.
 		 */
 		if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN)
 			return (ENXIO);
 
 		if (spa_check_logs(spa)) {
 			*ereport = FM_EREPORT_ZFS_LOG_REPLAY;
 			return (spa_vdev_err(rvd, VDEV_AUX_BAD_LOG, ENXIO));
 		}
 	}
 
 	/*
 	 * We've successfully opened the pool, verify that we're ready
 	 * to start pushing transactions.
 	 */
 	if (state != SPA_LOAD_TRYIMPORT) {
 		if ((error = spa_load_verify(spa)))
 			return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA,
 			    error));
 	}
 
 	if (spa_writeable(spa) && (state == SPA_LOAD_RECOVER ||
 	    spa->spa_load_max_txg == UINT64_MAX)) {
 		dmu_tx_t *tx;
 		int need_update = B_FALSE;
 		int c;
 
 		ASSERT(state != SPA_LOAD_TRYIMPORT);
 
 		/*
 		 * Claim log blocks that haven't been committed yet.
 		 * This must all happen in a single txg.
 		 * Note: spa_claim_max_txg is updated by spa_claim_notify(),
 		 * invoked from zil_claim_log_block()'s i/o done callback.
 		 * Price of rollback is that we abandon the log.
 		 */
 		spa->spa_claiming = B_TRUE;
 
 		tx = dmu_tx_create_assigned(spa_get_dsl(spa),
 		    spa_first_txg(spa));
 		(void) dmu_objset_find(spa_name(spa),
 		    zil_claim, tx, DS_FIND_CHILDREN);
 		dmu_tx_commit(tx);
 
 		spa->spa_claiming = B_FALSE;
 
 		spa_set_log_state(spa, SPA_LOG_GOOD);
 		spa->spa_sync_on = B_TRUE;
 		txg_sync_start(spa->spa_dsl_pool);
 
 		/*
 		 * Wait for all claims to sync.  We sync up to the highest
 		 * claimed log block birth time so that claimed log blocks
 		 * don't appear to be from the future.  spa_claim_max_txg
 		 * will have been set for us by either zil_check_log_chain()
 		 * (invoked from spa_check_logs()) or zil_claim() above.
 		 */
 		txg_wait_synced(spa->spa_dsl_pool, spa->spa_claim_max_txg);
 
 		/*
 		 * If the config cache is stale, or we have uninitialized
 		 * metaslabs (see spa_vdev_add()), then update the config.
 		 *
 		 * If this is a verbatim import, trust the current
 		 * in-core spa_config and update the disk labels.
 		 */
 		if (config_cache_txg != spa->spa_config_txg ||
 		    state == SPA_LOAD_IMPORT ||
 		    state == SPA_LOAD_RECOVER ||
 		    (spa->spa_import_flags & ZFS_IMPORT_VERBATIM))
 			need_update = B_TRUE;
 
 		for (c = 0; c < rvd->vdev_children; c++)
 			if (rvd->vdev_child[c]->vdev_ms_array == 0)
 				need_update = B_TRUE;
 
 		/*
 		 * Update the config cache asychronously in case we're the
 		 * root pool, in which case the config cache isn't writable yet.
 		 */
 		if (need_update)
 			spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
 
 		/*
 		 * Check all DTLs to see if anything needs resilvering.
 		 */
 		if (!dsl_scan_resilvering(spa->spa_dsl_pool) &&
 		    vdev_resilver_needed(rvd, NULL, NULL))
 			spa_async_request(spa, SPA_ASYNC_RESILVER);
 
 		/*
 		 * Delete any inconsistent datasets.
 		 */
 		(void) dmu_objset_find(spa_name(spa),
 		    dsl_destroy_inconsistent, NULL, DS_FIND_CHILDREN);
 
 		/*
 		 * Clean up any stale temporary dataset userrefs.
 		 */
 		dsl_pool_clean_tmp_userrefs(spa->spa_dsl_pool);
 	}
 
 	return (0);
 }
 
 static int
 spa_load_retry(spa_t *spa, spa_load_state_t state, int mosconfig)
 {
 	int mode = spa->spa_mode;
 
 	spa_unload(spa);
 	spa_deactivate(spa);
 
 	spa->spa_load_max_txg--;
 
 	spa_activate(spa, mode);
 	spa_async_suspend(spa);
 
 	return (spa_load(spa, state, SPA_IMPORT_EXISTING, mosconfig));
 }
 
 static int
 spa_load_best(spa_t *spa, spa_load_state_t state, int mosconfig,
     uint64_t max_request, int rewind_flags)
 {
 	nvlist_t *config = NULL;
 	int load_error, rewind_error;
 	uint64_t safe_rewind_txg;
 	uint64_t min_txg;
 
 	if (spa->spa_load_txg && state == SPA_LOAD_RECOVER) {
 		spa->spa_load_max_txg = spa->spa_load_txg;
 		spa_set_log_state(spa, SPA_LOG_CLEAR);
 	} else {
 		spa->spa_load_max_txg = max_request;
 	}
 
 	load_error = rewind_error = spa_load(spa, state, SPA_IMPORT_EXISTING,
 	    mosconfig);
 	if (load_error == 0)
 		return (0);
 
 	if (spa->spa_root_vdev != NULL)
 		config = spa_config_generate(spa, NULL, -1ULL, B_TRUE);
 
 	spa->spa_last_ubsync_txg = spa->spa_uberblock.ub_txg;
 	spa->spa_last_ubsync_txg_ts = spa->spa_uberblock.ub_timestamp;
 
 	if (rewind_flags & ZPOOL_NEVER_REWIND) {
 		nvlist_free(config);
 		return (load_error);
 	}
 
 	/* Price of rolling back is discarding txgs, including log */
 	if (state == SPA_LOAD_RECOVER)
 		spa_set_log_state(spa, SPA_LOG_CLEAR);
 
 	spa->spa_load_max_txg = spa->spa_last_ubsync_txg;
 	safe_rewind_txg = spa->spa_last_ubsync_txg - TXG_DEFER_SIZE;
 	min_txg = (rewind_flags & ZPOOL_EXTREME_REWIND) ?
 	    TXG_INITIAL : safe_rewind_txg;
 
 	/*
 	 * Continue as long as we're finding errors, we're still within
 	 * the acceptable rewind range, and we're still finding uberblocks
 	 */
 	while (rewind_error && spa->spa_uberblock.ub_txg >= min_txg &&
 	    spa->spa_uberblock.ub_txg <= spa->spa_load_max_txg) {
 		if (spa->spa_load_max_txg < safe_rewind_txg)
 			spa->spa_extreme_rewind = B_TRUE;
 		rewind_error = spa_load_retry(spa, state, mosconfig);
 	}
 
 	spa->spa_extreme_rewind = B_FALSE;
 	spa->spa_load_max_txg = UINT64_MAX;
 
 	if (config && (rewind_error || state != SPA_LOAD_RECOVER))
 		spa_config_set(spa, config);
 
 	return (state == SPA_LOAD_RECOVER ? rewind_error : load_error);
 }
 
 /*
  * Pool Open/Import
  *
  * The import case is identical to an open except that the configuration is sent
  * down from userland, instead of grabbed from the configuration cache.  For the
  * case of an open, the pool configuration will exist in the
  * POOL_STATE_UNINITIALIZED state.
  *
  * The stats information (gen/count/ustats) is used to gather vdev statistics at
  * the same time open the pool, without having to keep around the spa_t in some
  * ambiguous state.
  */
 static int
 spa_open_common(const char *pool, spa_t **spapp, void *tag, nvlist_t *nvpolicy,
     nvlist_t **config)
 {
 	spa_t *spa;
 	spa_load_state_t state = SPA_LOAD_OPEN;
 	int error;
 	int locked = B_FALSE;
 
 	*spapp = NULL;
 
 	/*
 	 * As disgusting as this is, we need to support recursive calls to this
 	 * function because dsl_dir_open() is called during spa_load(), and ends
 	 * up calling spa_open() again.  The real fix is to figure out how to
 	 * avoid dsl_dir_open() calling this in the first place.
 	 */
 	if (mutex_owner(&spa_namespace_lock) != curthread) {
 		mutex_enter(&spa_namespace_lock);
 		locked = B_TRUE;
 	}
 
 	if ((spa = spa_lookup(pool)) == NULL) {
 		if (locked)
 			mutex_exit(&spa_namespace_lock);
 		return (ENOENT);
 	}
 
 	if (spa->spa_state == POOL_STATE_UNINITIALIZED) {
 		zpool_rewind_policy_t policy;
 
 		zpool_get_rewind_policy(nvpolicy ? nvpolicy : spa->spa_config,
 		    &policy);
 		if (policy.zrp_request & ZPOOL_DO_REWIND)
 			state = SPA_LOAD_RECOVER;
 
 		spa_activate(spa, spa_mode_global);
 
 		if (state != SPA_LOAD_RECOVER)
 			spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;
 
 		error = spa_load_best(spa, state, B_FALSE, policy.zrp_txg,
 		    policy.zrp_request);
 
 		if (error == EBADF) {
 			/*
 			 * If vdev_validate() returns failure (indicated by
 			 * EBADF), it indicates that one of the vdevs indicates
 			 * that the pool has been exported or destroyed.  If
 			 * this is the case, the config cache is out of sync and
 			 * we should remove the pool from the namespace.
 			 */
 			spa_unload(spa);
 			spa_deactivate(spa);
 			spa_config_sync(spa, B_TRUE, B_TRUE);
 			spa_remove(spa);
 			if (locked)
 				mutex_exit(&spa_namespace_lock);
 			return (ENOENT);
 		}
 
 		if (error) {
 			/*
 			 * We can't open the pool, but we still have useful
 			 * information: the state of each vdev after the
 			 * attempted vdev_open().  Return this to the user.
 			 */
 			if (config != NULL && spa->spa_config) {
 				VERIFY(nvlist_dup(spa->spa_config, config,
 				    KM_PUSHPAGE) == 0);
 				VERIFY(nvlist_add_nvlist(*config,
 				    ZPOOL_CONFIG_LOAD_INFO,
 				    spa->spa_load_info) == 0);
 			}
 			spa_unload(spa);
 			spa_deactivate(spa);
 			spa->spa_last_open_failed = error;
 			if (locked)
 				mutex_exit(&spa_namespace_lock);
 			*spapp = NULL;
 			return (error);
 		}
 	}
 
 	spa_open_ref(spa, tag);
 
 	if (config != NULL)
 		*config = spa_config_generate(spa, NULL, -1ULL, B_TRUE);
 
 	/*
 	 * If we've recovered the pool, pass back any information we
 	 * gathered while doing the load.
 	 */
 	if (state == SPA_LOAD_RECOVER) {
 		VERIFY(nvlist_add_nvlist(*config, ZPOOL_CONFIG_LOAD_INFO,
 		    spa->spa_load_info) == 0);
 	}
 
 	if (locked) {
 		spa->spa_last_open_failed = 0;
 		spa->spa_last_ubsync_txg = 0;
 		spa->spa_load_txg = 0;
 		mutex_exit(&spa_namespace_lock);
 	}
 
 	*spapp = spa;
 
 	return (0);
 }
 
 int
 spa_open_rewind(const char *name, spa_t **spapp, void *tag, nvlist_t *policy,
     nvlist_t **config)
 {
 	return (spa_open_common(name, spapp, tag, policy, config));
 }
 
 int
 spa_open(const char *name, spa_t **spapp, void *tag)
 {
 	return (spa_open_common(name, spapp, tag, NULL, NULL));
 }
 
 /*
  * Lookup the given spa_t, incrementing the inject count in the process,
  * preventing it from being exported or destroyed.
  */
 spa_t *
 spa_inject_addref(char *name)
 {
 	spa_t *spa;
 
 	mutex_enter(&spa_namespace_lock);
 	if ((spa = spa_lookup(name)) == NULL) {
 		mutex_exit(&spa_namespace_lock);
 		return (NULL);
 	}
 	spa->spa_inject_ref++;
 	mutex_exit(&spa_namespace_lock);
 
 	return (spa);
 }
 
 void
 spa_inject_delref(spa_t *spa)
 {
 	mutex_enter(&spa_namespace_lock);
 	spa->spa_inject_ref--;
 	mutex_exit(&spa_namespace_lock);
 }
 
 /*
  * Add spares device information to the nvlist.
  */
 static void
 spa_add_spares(spa_t *spa, nvlist_t *config)
 {
 	nvlist_t **spares;
 	uint_t i, nspares;
 	nvlist_t *nvroot;
 	uint64_t guid;
 	vdev_stat_t *vs;
 	uint_t vsc;
 	uint64_t pool;
 
 	ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));
 
 	if (spa->spa_spares.sav_count == 0)
 		return;
 
 	VERIFY(nvlist_lookup_nvlist(config,
 	    ZPOOL_CONFIG_VDEV_TREE, &nvroot) == 0);
 	VERIFY(nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
 	    ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0);
 	if (nspares != 0) {
 		VERIFY(nvlist_add_nvlist_array(nvroot,
 		    ZPOOL_CONFIG_SPARES, spares, nspares) == 0);
 		VERIFY(nvlist_lookup_nvlist_array(nvroot,
 		    ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0);
 
 		/*
 		 * Go through and find any spares which have since been
 		 * repurposed as an active spare.  If this is the case, update
 		 * their status appropriately.
 		 */
 		for (i = 0; i < nspares; i++) {
 			VERIFY(nvlist_lookup_uint64(spares[i],
 			    ZPOOL_CONFIG_GUID, &guid) == 0);
 			if (spa_spare_exists(guid, &pool, NULL) &&
 			    pool != 0ULL) {
 				VERIFY(nvlist_lookup_uint64_array(
 				    spares[i], ZPOOL_CONFIG_VDEV_STATS,
 				    (uint64_t **)&vs, &vsc) == 0);
 				vs->vs_state = VDEV_STATE_CANT_OPEN;
 				vs->vs_aux = VDEV_AUX_SPARED;
 			}
 		}
 	}
 }
 
 /*
  * Add l2cache device information to the nvlist, including vdev stats.
  */
 static void
 spa_add_l2cache(spa_t *spa, nvlist_t *config)
 {
 	nvlist_t **l2cache;
 	uint_t i, j, nl2cache;
 	nvlist_t *nvroot;
 	uint64_t guid;
 	vdev_t *vd;
 	vdev_stat_t *vs;
 	uint_t vsc;
 
 	ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));
 
 	if (spa->spa_l2cache.sav_count == 0)
 		return;
 
 	VERIFY(nvlist_lookup_nvlist(config,
 	    ZPOOL_CONFIG_VDEV_TREE, &nvroot) == 0);
 	VERIFY(nvlist_lookup_nvlist_array(spa->spa_l2cache.sav_config,
 	    ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0);
 	if (nl2cache != 0) {
 		VERIFY(nvlist_add_nvlist_array(nvroot,
 		    ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache) == 0);
 		VERIFY(nvlist_lookup_nvlist_array(nvroot,
 		    ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0);
 
 		/*
 		 * Update level 2 cache device stats.
 		 */
 
 		for (i = 0; i < nl2cache; i++) {
 			VERIFY(nvlist_lookup_uint64(l2cache[i],
 			    ZPOOL_CONFIG_GUID, &guid) == 0);
 
 			vd = NULL;
 			for (j = 0; j < spa->spa_l2cache.sav_count; j++) {
 				if (guid ==
 				    spa->spa_l2cache.sav_vdevs[j]->vdev_guid) {
 					vd = spa->spa_l2cache.sav_vdevs[j];
 					break;
 				}
 			}
 			ASSERT(vd != NULL);
 
 			VERIFY(nvlist_lookup_uint64_array(l2cache[i],
 			    ZPOOL_CONFIG_VDEV_STATS, (uint64_t **)&vs, &vsc)
 			    == 0);
 			vdev_get_stats(vd, vs);
 		}
 	}
 }
 
 int
 spa_get_stats(const char *name, nvlist_t **config, char *altroot, size_t buflen)
 {
 	int error;
 	spa_t *spa;
 
 	*config = NULL;
 	error = spa_open_common(name, &spa, FTAG, NULL, config);
 
 	if (spa != NULL) {
 		/*
 		 * This still leaves a window of inconsistency where the spares
 		 * or l2cache devices could change and the config would be
 		 * self-inconsistent.
 		 */
 		spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
 
 		if (*config != NULL) {
 			uint64_t loadtimes[2];
 
 			loadtimes[0] = spa->spa_loaded_ts.tv_sec;
 			loadtimes[1] = spa->spa_loaded_ts.tv_nsec;
 			VERIFY(nvlist_add_uint64_array(*config,
 			    ZPOOL_CONFIG_LOADED_TIME, loadtimes, 2) == 0);
 
 			VERIFY(nvlist_add_uint64(*config,
 			    ZPOOL_CONFIG_ERRCOUNT,
 			    spa_get_errlog_size(spa)) == 0);
 
 			if (spa_suspended(spa))
 				VERIFY(nvlist_add_uint64(*config,
 				    ZPOOL_CONFIG_SUSPENDED,
 				    spa->spa_failmode) == 0);
 
 			spa_add_spares(spa, *config);
 			spa_add_l2cache(spa, *config);
 		}
 	}
 
 	/*
 	 * We want to get the alternate root even for faulted pools, so we cheat
 	 * and call spa_lookup() directly.
 	 */
 	if (altroot) {
 		if (spa == NULL) {
 			mutex_enter(&spa_namespace_lock);
 			spa = spa_lookup(name);
 			if (spa)
 				spa_altroot(spa, altroot, buflen);
 			else
 				altroot[0] = '\0';
 			spa = NULL;
 			mutex_exit(&spa_namespace_lock);
 		} else {
 			spa_altroot(spa, altroot, buflen);
 		}
 	}
 
 	if (spa != NULL) {
 		spa_config_exit(spa, SCL_CONFIG, FTAG);
 		spa_close(spa, FTAG);
 	}
 
 	return (error);
 }
 
 /*
  * Validate that the auxiliary device array is well formed.  We must have an
  * array of nvlists, each which describes a valid leaf vdev.  If this is an
  * import (mode is VDEV_ALLOC_SPARE), then we allow corrupted spares to be
  * specified, as long as they are well-formed.
  */
 static int
 spa_validate_aux_devs(spa_t *spa, nvlist_t *nvroot, uint64_t crtxg, int mode,
     spa_aux_vdev_t *sav, const char *config, uint64_t version,
     vdev_labeltype_t label)
 {
 	nvlist_t **dev;
 	uint_t i, ndev;
 	vdev_t *vd;
 	int error;
 
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
 	/*
 	 * It's acceptable to have no devs specified.
 	 */
 	if (nvlist_lookup_nvlist_array(nvroot, config, &dev, &ndev) != 0)
 		return (0);
 
 	if (ndev == 0)
 		return (EINVAL);
 
 	/*
 	 * Make sure the pool is formatted with a version that supports this
 	 * device type.
 	 */
 	if (spa_version(spa) < version)
 		return (ENOTSUP);
 
 	/*
 	 * Set the pending device list so we correctly handle device in-use
 	 * checking.
 	 */
 	sav->sav_pending = dev;
 	sav->sav_npending = ndev;
 
 	for (i = 0; i < ndev; i++) {
 		if ((error = spa_config_parse(spa, &vd, dev[i], NULL, 0,
 		    mode)) != 0)
 			goto out;
 
 		if (!vd->vdev_ops->vdev_op_leaf) {
 			vdev_free(vd);
 			error = EINVAL;
 			goto out;
 		}
 
 		/*
 		 * The L2ARC currently only supports disk devices in
 		 * kernel context.  For user-level testing, we allow it.
 		 */
 #ifdef _KERNEL
 		if ((strcmp(config, ZPOOL_CONFIG_L2CACHE) == 0) &&
 		    strcmp(vd->vdev_ops->vdev_op_type, VDEV_TYPE_DISK) != 0) {
 			error = ENOTBLK;
 			vdev_free(vd);
 			goto out;
 		}
 #endif
 		vd->vdev_top = vd;
 
 		if ((error = vdev_open(vd)) == 0 &&
 		    (error = vdev_label_init(vd, crtxg, label)) == 0) {
 			VERIFY(nvlist_add_uint64(dev[i], ZPOOL_CONFIG_GUID,
 			    vd->vdev_guid) == 0);
 		}
 
 		vdev_free(vd);
 
 		if (error &&
 		    (mode != VDEV_ALLOC_SPARE && mode != VDEV_ALLOC_L2CACHE))
 			goto out;
 		else
 			error = 0;
 	}
 
 out:
 	sav->sav_pending = NULL;
 	sav->sav_npending = 0;
 	return (error);
 }
 
 static int
 spa_validate_aux(spa_t *spa, nvlist_t *nvroot, uint64_t crtxg, int mode)
 {
 	int error;
 
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 
 	if ((error = spa_validate_aux_devs(spa, nvroot, crtxg, mode,
 	    &spa->spa_spares, ZPOOL_CONFIG_SPARES, SPA_VERSION_SPARES,
 	    VDEV_LABEL_SPARE)) != 0) {
 		return (error);
 	}
 
 	return (spa_validate_aux_devs(spa, nvroot, crtxg, mode,
 	    &spa->spa_l2cache, ZPOOL_CONFIG_L2CACHE, SPA_VERSION_L2CACHE,
 	    VDEV_LABEL_L2CACHE));
 }
 
 static void
 spa_set_aux_vdevs(spa_aux_vdev_t *sav, nvlist_t **devs, int ndevs,
     const char *config)
 {
 	int i;
 
 	if (sav->sav_config != NULL) {
 		nvlist_t **olddevs;
 		uint_t oldndevs;
 		nvlist_t **newdevs;
 
 		/*
 		 * Generate new dev list by concatentating with the
 		 * current dev list.
 		 */
 		VERIFY(nvlist_lookup_nvlist_array(sav->sav_config, config,
 		    &olddevs, &oldndevs) == 0);
 
 		newdevs = kmem_alloc(sizeof (void *) *
 		    (ndevs + oldndevs), KM_PUSHPAGE);
 		for (i = 0; i < oldndevs; i++)
 			VERIFY(nvlist_dup(olddevs[i], &newdevs[i],
 			    KM_PUSHPAGE) == 0);
 		for (i = 0; i < ndevs; i++)
 			VERIFY(nvlist_dup(devs[i], &newdevs[i + oldndevs],
 			    KM_PUSHPAGE) == 0);
 
 		VERIFY(nvlist_remove(sav->sav_config, config,
 		    DATA_TYPE_NVLIST_ARRAY) == 0);
 
 		VERIFY(nvlist_add_nvlist_array(sav->sav_config,
 		    config, newdevs, ndevs + oldndevs) == 0);
 		for (i = 0; i < oldndevs + ndevs; i++)
 			nvlist_free(newdevs[i]);
 		kmem_free(newdevs, (oldndevs + ndevs) * sizeof (void *));
 	} else {
 		/*
 		 * Generate a new dev list.
 		 */
 		VERIFY(nvlist_alloc(&sav->sav_config, NV_UNIQUE_NAME,
 		    KM_PUSHPAGE) == 0);
 		VERIFY(nvlist_add_nvlist_array(sav->sav_config, config,
 		    devs, ndevs) == 0);
 	}
 }
 
 /*
  * Stop and drop level 2 ARC devices
  */
 void
 spa_l2cache_drop(spa_t *spa)
 {
 	vdev_t *vd;
 	int i;
 	spa_aux_vdev_t *sav = &spa->spa_l2cache;
 
 	for (i = 0; i < sav->sav_count; i++) {
 		uint64_t pool;
 
 		vd = sav->sav_vdevs[i];
 		ASSERT(vd != NULL);
 
 		if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
 		    pool != 0ULL && l2arc_vdev_present(vd))
 			l2arc_remove_vdev(vd);
 	}
 }
 
 /*
  * Pool Creation
  */
 int
 spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
     const char *history_str, nvlist_t *zplprops)
 {
 	spa_t *spa;
 	char *altroot = NULL;
 	vdev_t *rvd;
 	dsl_pool_t *dp;
 	dmu_tx_t *tx;
 	int error = 0;
 	uint64_t txg = TXG_INITIAL;
 	nvlist_t **spares, **l2cache;
 	uint_t nspares, nl2cache;
 	uint64_t version, obj;
 	int c;
 
 	/*
 	 * If this pool already exists, return failure.
 	 */
 	mutex_enter(&spa_namespace_lock);
 	if (spa_lookup(pool) != NULL) {
 		mutex_exit(&spa_namespace_lock);
 		return (EEXIST);
 	}
 
 	/*
 	 * Allocate a new spa_t structure.
 	 */
 	(void) nvlist_lookup_string(props,
 	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
 	spa = spa_add(pool, NULL, altroot);
 	spa_activate(spa, spa_mode_global);
 
 	if (props && (error = spa_prop_validate(spa, props))) {
 		spa_deactivate(spa);
 		spa_remove(spa);
 		mutex_exit(&spa_namespace_lock);
 		return (error);
 	}
 
 	if (nvlist_lookup_uint64(props, zpool_prop_to_name(ZPOOL_PROP_VERSION),
 	    &version) != 0)
 		version = SPA_VERSION;
 	ASSERT(version <= SPA_VERSION);
 
 	spa->spa_first_txg = txg;
 	spa->spa_uberblock.ub_txg = txg - 1;
 	spa->spa_uberblock.ub_version = version;
 	spa->spa_ubsync = spa->spa_uberblock;
 
 	/*
 	 * Create "The Godfather" zio to hold all async IOs
 	 */
 	spa->spa_async_zio_root = zio_root(spa, NULL, NULL,
 	    ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_GODFATHER);
 
 	/*
 	 * Create the root vdev.
 	 */
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 
 	error = spa_config_parse(spa, &rvd, nvroot, NULL, 0, VDEV_ALLOC_ADD);
 
 	ASSERT(error != 0 || rvd != NULL);
 	ASSERT(error != 0 || spa->spa_root_vdev == rvd);
 
 	if (error == 0 && !zfs_allocatable_devs(nvroot))
 		error = EINVAL;
 
 	if (error == 0 &&
 	    (error = vdev_create(rvd, txg, B_FALSE)) == 0 &&
 	    (error = spa_validate_aux(spa, nvroot, txg,
 	    VDEV_ALLOC_ADD)) == 0) {
 		for (c = 0; c < rvd->vdev_children; c++) {
 			vdev_metaslab_set_size(rvd->vdev_child[c]);
 			vdev_expand(rvd->vdev_child[c], txg);
 		}
 	}
 
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	if (error != 0) {
 		spa_unload(spa);
 		spa_deactivate(spa);
 		spa_remove(spa);
 		mutex_exit(&spa_namespace_lock);
 		return (error);
 	}
 
 	/*
 	 * Get the list of spares, if specified.
 	 */
 	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES,
 	    &spares, &nspares) == 0) {
 		VERIFY(nvlist_alloc(&spa->spa_spares.sav_config, NV_UNIQUE_NAME,
 		    KM_PUSHPAGE) == 0);
 		VERIFY(nvlist_add_nvlist_array(spa->spa_spares.sav_config,
 		    ZPOOL_CONFIG_SPARES, spares, nspares) == 0);
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_load_spares(spa);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 		spa->spa_spares.sav_sync = B_TRUE;
 	}
 
 	/*
 	 * Get the list of level 2 cache devices, if specified.
 	 */
 	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_L2CACHE,
 	    &l2cache, &nl2cache) == 0) {
 		VERIFY(nvlist_alloc(&spa->spa_l2cache.sav_config,
 		    NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 		VERIFY(nvlist_add_nvlist_array(spa->spa_l2cache.sav_config,
 		    ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache) == 0);
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_load_l2cache(spa);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 		spa->spa_l2cache.sav_sync = B_TRUE;
 	}
 
 	spa->spa_dsl_pool = dp = dsl_pool_create(spa, zplprops, txg);
 	spa->spa_meta_objset = dp->dp_meta_objset;
 
 	/*
 	 * Create DDTs (dedup tables).
 	 */
 	ddt_create(spa);
 
 	spa_update_dspace(spa);
 
 	tx = dmu_tx_create_assigned(dp, txg);
 
 	/*
 	 * Create the pool config object.
 	 */
 	spa->spa_config_object = dmu_object_alloc(spa->spa_meta_objset,
 	    DMU_OT_PACKED_NVLIST, SPA_CONFIG_BLOCKSIZE,
 	    DMU_OT_PACKED_NVLIST_SIZE, sizeof (uint64_t), tx);
 
 	if (zap_add(spa->spa_meta_objset,
 	    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CONFIG,
 	    sizeof (uint64_t), 1, &spa->spa_config_object, tx) != 0) {
 		cmn_err(CE_PANIC, "failed to add pool config");
 	}
 
 	if (zap_add(spa->spa_meta_objset,
 	    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CREATION_VERSION,
 	    sizeof (uint64_t), 1, &version, tx) != 0) {
 		cmn_err(CE_PANIC, "failed to add pool version");
 	}
 
 	/* Newly created pools with the right version are always deflated. */
 	if (version >= SPA_VERSION_RAIDZ_DEFLATE) {
 		spa->spa_deflate = TRUE;
 		if (zap_add(spa->spa_meta_objset,
 		    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
 		    sizeof (uint64_t), 1, &spa->spa_deflate, tx) != 0) {
 			cmn_err(CE_PANIC, "failed to add deflate");
 		}
 	}
 
 	/*
 	 * Create the deferred-free bpobj.  Turn off compression
 	 * because sync-to-convergence takes longer if the blocksize
 	 * keeps changing.
 	 */
 	obj = bpobj_alloc(spa->spa_meta_objset, 1 << 14, tx);
 	dmu_object_set_compress(spa->spa_meta_objset, obj,
 	    ZIO_COMPRESS_OFF, tx);
 	if (zap_add(spa->spa_meta_objset,
 	    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_SYNC_BPOBJ,
 	    sizeof (uint64_t), 1, &obj, tx) != 0) {
 		cmn_err(CE_PANIC, "failed to add bpobj");
 	}
 	VERIFY3U(0, ==, bpobj_open(&spa->spa_deferred_bpobj,
 	    spa->spa_meta_objset, obj));
 
 	/*
 	 * Create the pool's history object.
 	 */
 	if (version >= SPA_VERSION_ZPOOL_HISTORY)
 		spa_history_create_obj(spa, tx);
 
 	/*
 	 * Set pool properties.
 	 */
 	spa->spa_bootfs = zpool_prop_default_numeric(ZPOOL_PROP_BOOTFS);
 	spa->spa_delegation = zpool_prop_default_numeric(ZPOOL_PROP_DELEGATION);
 	spa->spa_failmode = zpool_prop_default_numeric(ZPOOL_PROP_FAILUREMODE);
 	spa->spa_autoexpand = zpool_prop_default_numeric(ZPOOL_PROP_AUTOEXPAND);
 
 	if (props != NULL) {
 		spa_configfile_set(spa, props, B_FALSE);
 		spa_sync_props(spa, props, tx);
 	}
 
 	dmu_tx_commit(tx);
 
 	spa->spa_sync_on = B_TRUE;
 	txg_sync_start(spa->spa_dsl_pool);
 
 	/*
 	 * We explicitly wait for the first transaction to complete so that our
 	 * bean counters are appropriately updated.
 	 */
 	txg_wait_synced(spa->spa_dsl_pool, txg);
 
 	spa_config_sync(spa, B_FALSE, B_TRUE);
 
 	if (version >= SPA_VERSION_ZPOOL_HISTORY && history_str != NULL)
 		(void) spa_history_log(spa, history_str, LOG_CMD_POOL_CREATE);
 	spa_history_log_version(spa, LOG_POOL_CREATE);
 
 	spa->spa_minref = refcount_count(&spa->spa_refcount);
 
 	mutex_exit(&spa_namespace_lock);
 
 	return (0);
 }
 
 #ifdef _KERNEL
 /*
  * Get the root pool information from the root disk, then import the root pool
  * during the system boot up time.
  */
 extern int vdev_disk_read_rootlabel(char *, char *, nvlist_t **);
 
 static nvlist_t *
 spa_generate_rootconf(char *devpath, char *devid, uint64_t *guid)
 {
 	nvlist_t *config;
 	nvlist_t *nvtop, *nvroot;
 	uint64_t pgid;
 
 	if (vdev_disk_read_rootlabel(devpath, devid, &config) != 0)
 		return (NULL);
 
 	/*
 	 * Add this top-level vdev to the child array.
 	 */
 	VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
 	    &nvtop) == 0);
 	VERIFY(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID,
 	    &pgid) == 0);
 	VERIFY(nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID, guid) == 0);
 
 	/*
 	 * Put this pool's top-level vdevs into a root vdev.
 	 */
 	VERIFY(nvlist_alloc(&nvroot, NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 	VERIFY(nvlist_add_string(nvroot, ZPOOL_CONFIG_TYPE,
 	    VDEV_TYPE_ROOT) == 0);
 	VERIFY(nvlist_add_uint64(nvroot, ZPOOL_CONFIG_ID, 0ULL) == 0);
 	VERIFY(nvlist_add_uint64(nvroot, ZPOOL_CONFIG_GUID, pgid) == 0);
 	VERIFY(nvlist_add_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
 	    &nvtop, 1) == 0);
 
 	/*
 	 * Replace the existing vdev_tree with the new root vdev in
 	 * this pool's configuration (remove the old, add the new).
 	 */
 	VERIFY(nvlist_add_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, nvroot) == 0);
 	nvlist_free(nvroot);
 	return (config);
 }
 
 /*
  * Walk the vdev tree and see if we can find a device with "better"
  * configuration. A configuration is "better" if the label on that
  * device has a more recent txg.
  */
 static void
 spa_alt_rootvdev(vdev_t *vd, vdev_t **avd, uint64_t *txg)
 {
 	int c;
 
 	for (c = 0; c < vd->vdev_children; c++)
 		spa_alt_rootvdev(vd->vdev_child[c], avd, txg);
 
 	if (vd->vdev_ops->vdev_op_leaf) {
 		nvlist_t *label;
 		uint64_t label_txg;
 
 		if (vdev_disk_read_rootlabel(vd->vdev_physpath, vd->vdev_devid,
 		    &label) != 0)
 			return;
 
 		VERIFY(nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_TXG,
 		    &label_txg) == 0);
 
 		/*
 		 * Do we have a better boot device?
 		 */
 		if (label_txg > *txg) {
 			*txg = label_txg;
 			*avd = vd;
 		}
 		nvlist_free(label);
 	}
 }
 
 /*
  * Import a root pool.
  *
  * For x86. devpath_list will consist of devid and/or physpath name of
  * the vdev (e.g. "id1,sd@SSEAGATE..." or "/pci@1f,0/ide@d/disk@0,0:a").
  * The GRUB "findroot" command will return the vdev we should boot.
  *
  * For Sparc, devpath_list consists the physpath name of the booting device
  * no matter the rootpool is a single device pool or a mirrored pool.
  * e.g.
  *	"/pci@1f,0/ide@d/disk@0,0:a"
  */
 int
 spa_import_rootpool(char *devpath, char *devid)
 {
 	spa_t *spa;
 	vdev_t *rvd, *bvd, *avd = NULL;
 	nvlist_t *config, *nvtop;
 	uint64_t guid, txg;
 	char *pname;
 	int error;
 
 	/*
 	 * Read the label from the boot device and generate a configuration.
 	 */
 	config = spa_generate_rootconf(devpath, devid, &guid);
 #if defined(_OBP) && defined(_KERNEL)
 	if (config == NULL) {
 		if (strstr(devpath, "/iscsi/ssd") != NULL) {
 			/* iscsi boot */
 			get_iscsi_bootpath_phy(devpath);
 			config = spa_generate_rootconf(devpath, devid, &guid);
 		}
 	}
 #endif
 	if (config == NULL) {
 		cmn_err(CE_NOTE, "Can not read the pool label from '%s'",
 		    devpath);
 		return (EIO);
 	}
 
 	VERIFY(nvlist_lookup_string(config, ZPOOL_CONFIG_POOL_NAME,
 	    &pname) == 0);
 	VERIFY(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG, &txg) == 0);
 
 	mutex_enter(&spa_namespace_lock);
 	if ((spa = spa_lookup(pname)) != NULL) {
 		/*
 		 * Remove the existing root pool from the namespace so that we
 		 * can replace it with the correct config we just read in.
 		 */
 		spa_remove(spa);
 	}
 
 	spa = spa_add(pname, config, NULL);
 	spa->spa_is_root = B_TRUE;
 	spa->spa_import_flags = ZFS_IMPORT_VERBATIM;
 
 	/*
 	 * Build up a vdev tree based on the boot device's label config.
 	 */
 	VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
 	    &nvtop) == 0);
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	error = spa_config_parse(spa, &rvd, nvtop, NULL, 0,
 	    VDEV_ALLOC_ROOTPOOL);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 	if (error) {
 		mutex_exit(&spa_namespace_lock);
 		nvlist_free(config);
 		cmn_err(CE_NOTE, "Can not parse the config for pool '%s'",
 		    pname);
 		return (error);
 	}
 
 	/*
 	 * Get the boot vdev.
 	 */
 	if ((bvd = vdev_lookup_by_guid(rvd, guid)) == NULL) {
 		cmn_err(CE_NOTE, "Can not find the boot vdev for guid %llu",
 		    (u_longlong_t)guid);
 		error = ENOENT;
 		goto out;
 	}
 
 	/*
 	 * Determine if there is a better boot device.
 	 */
 	avd = bvd;
 	spa_alt_rootvdev(rvd, &avd, &txg);
 	if (avd != bvd) {
 		cmn_err(CE_NOTE, "The boot device is 'degraded'. Please "
 		    "try booting from '%s'", avd->vdev_path);
 		error = EINVAL;
 		goto out;
 	}
 
 	/*
 	 * If the boot device is part of a spare vdev then ensure that
 	 * we're booting off the active spare.
 	 */
 	if (bvd->vdev_parent->vdev_ops == &vdev_spare_ops &&
 	    !bvd->vdev_isspare) {
 		cmn_err(CE_NOTE, "The boot device is currently spared. Please "
 		    "try booting from '%s'",
 		    bvd->vdev_parent->
 		    vdev_child[bvd->vdev_parent->vdev_children - 1]->vdev_path);
 		error = EINVAL;
 		goto out;
 	}
 
 	error = 0;
 	spa_history_log_version(spa, LOG_POOL_IMPORT);
 out:
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	vdev_free(rvd);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 	mutex_exit(&spa_namespace_lock);
 
 	nvlist_free(config);
 	return (error);
 }
 
 #endif
 
 /*
  * Import a non-root pool into the system.
  */
 int
 spa_import(const char *pool, nvlist_t *config, nvlist_t *props, uint64_t flags)
 {
 	spa_t *spa;
 	char *altroot = NULL;
 	spa_load_state_t state = SPA_LOAD_IMPORT;
 	zpool_rewind_policy_t policy;
 	uint64_t mode = spa_mode_global;
 	uint64_t readonly = B_FALSE;
 	int error;
 	nvlist_t *nvroot;
 	nvlist_t **spares, **l2cache;
 	uint_t nspares, nl2cache;
 
 	/*
 	 * If a pool with this name exists, return failure.
 	 */
 	mutex_enter(&spa_namespace_lock);
 	if (spa_lookup(pool) != NULL) {
 		mutex_exit(&spa_namespace_lock);
 		return (EEXIST);
 	}
 
 	/*
 	 * Create and initialize the spa structure.
 	 */
 	(void) nvlist_lookup_string(props,
 	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
 	(void) nvlist_lookup_uint64(props,
 	    zpool_prop_to_name(ZPOOL_PROP_READONLY), &readonly);
 	if (readonly)
 		mode = FREAD;
 	spa = spa_add(pool, config, altroot);
 	spa->spa_import_flags = flags;
 
 	/*
 	 * Verbatim import - Take a pool and insert it into the namespace
 	 * as if it had been loaded at boot.
 	 */
 	if (spa->spa_import_flags & ZFS_IMPORT_VERBATIM) {
 		if (props != NULL)
 			spa_configfile_set(spa, props, B_FALSE);
 
 		spa_config_sync(spa, B_FALSE, B_TRUE);
 
 		mutex_exit(&spa_namespace_lock);
 		spa_history_log_version(spa, LOG_POOL_IMPORT);
 
 		return (0);
 	}
 
 	spa_activate(spa, mode);
 
 	/*
 	 * Don't start async tasks until we know everything is healthy.
 	 */
 	spa_async_suspend(spa);
 
 	zpool_get_rewind_policy(config, &policy);
 	if (policy.zrp_request & ZPOOL_DO_REWIND)
 		state = SPA_LOAD_RECOVER;
 
 	/*
 	 * Pass off the heavy lifting to spa_load().  Pass TRUE for mosconfig
 	 * because the user-supplied config is actually the one to trust when
 	 * doing an import.
 	 */
 	if (state != SPA_LOAD_RECOVER)
 		spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;
 
 	error = spa_load_best(spa, state, B_TRUE, policy.zrp_txg,
 	    policy.zrp_request);
 
 	/*
 	 * Propagate anything learned while loading the pool and pass it
 	 * back to caller (i.e. rewind info, missing devices, etc).
 	 */
 	VERIFY(nvlist_add_nvlist(config, ZPOOL_CONFIG_LOAD_INFO,
 	    spa->spa_load_info) == 0);
 
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	/*
 	 * Toss any existing sparelist, as it doesn't have any validity
 	 * anymore, and conflicts with spa_has_spare().
 	 */
 	if (spa->spa_spares.sav_config) {
 		nvlist_free(spa->spa_spares.sav_config);
 		spa->spa_spares.sav_config = NULL;
 		spa_load_spares(spa);
 	}
 	if (spa->spa_l2cache.sav_config) {
 		nvlist_free(spa->spa_l2cache.sav_config);
 		spa->spa_l2cache.sav_config = NULL;
 		spa_load_l2cache(spa);
 	}
 
 	VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
 	    &nvroot) == 0);
 	if (error == 0)
 		error = spa_validate_aux(spa, nvroot, -1ULL,
 		    VDEV_ALLOC_SPARE);
 	if (error == 0)
 		error = spa_validate_aux(spa, nvroot, -1ULL,
 		    VDEV_ALLOC_L2CACHE);
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	if (props != NULL)
 		spa_configfile_set(spa, props, B_FALSE);
 
 	if (error != 0 || (props && spa_writeable(spa) &&
 	    (error = spa_prop_set(spa, props)))) {
 		spa_unload(spa);
 		spa_deactivate(spa);
 		spa_remove(spa);
 		mutex_exit(&spa_namespace_lock);
 		return (error);
 	}
 
 	spa_async_resume(spa);
 
 	/*
 	 * Override any spares and level 2 cache devices as specified by
 	 * the user, as these may have correct device names/devids, etc.
 	 */
 	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES,
 	    &spares, &nspares) == 0) {
 		if (spa->spa_spares.sav_config)
 			VERIFY(nvlist_remove(spa->spa_spares.sav_config,
 			    ZPOOL_CONFIG_SPARES, DATA_TYPE_NVLIST_ARRAY) == 0);
 		else
 			VERIFY(nvlist_alloc(&spa->spa_spares.sav_config,
 			    NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 		VERIFY(nvlist_add_nvlist_array(spa->spa_spares.sav_config,
 		    ZPOOL_CONFIG_SPARES, spares, nspares) == 0);
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_load_spares(spa);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 		spa->spa_spares.sav_sync = B_TRUE;
 	}
 	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_L2CACHE,
 	    &l2cache, &nl2cache) == 0) {
 		if (spa->spa_l2cache.sav_config)
 			VERIFY(nvlist_remove(spa->spa_l2cache.sav_config,
 			    ZPOOL_CONFIG_L2CACHE, DATA_TYPE_NVLIST_ARRAY) == 0);
 		else
 			VERIFY(nvlist_alloc(&spa->spa_l2cache.sav_config,
 			    NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 		VERIFY(nvlist_add_nvlist_array(spa->spa_l2cache.sav_config,
 		    ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache) == 0);
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 		spa_load_l2cache(spa);
 		spa_config_exit(spa, SCL_ALL, FTAG);
 		spa->spa_l2cache.sav_sync = B_TRUE;
 	}
 
 	/*
 	 * Check for any removed devices.
 	 */
 	if (spa->spa_autoreplace) {
 		spa_aux_check_removed(&spa->spa_spares);
 		spa_aux_check_removed(&spa->spa_l2cache);
 	}
 
 	if (spa_writeable(spa)) {
 		/*
 		 * Update the config cache to include the newly-imported pool.
 		 */
 		spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
 	}
 
 	/*
 	 * It's possible that the pool was expanded while it was exported.
 	 * We kick off an async task to handle this for us.
 	 */
 	spa_async_request(spa, SPA_ASYNC_AUTOEXPAND);
 
 	mutex_exit(&spa_namespace_lock);
 	spa_history_log_version(spa, LOG_POOL_IMPORT);
 
 	return (0);
 }
 
 nvlist_t *
 spa_tryimport(nvlist_t *tryconfig)
 {
 	nvlist_t *config = NULL;
 	char *poolname;
 	spa_t *spa;
 	uint64_t state;
 	int error;
 
 	if (nvlist_lookup_string(tryconfig, ZPOOL_CONFIG_POOL_NAME, &poolname))
 		return (NULL);
 
 	if (nvlist_lookup_uint64(tryconfig, ZPOOL_CONFIG_POOL_STATE, &state))
 		return (NULL);
 
 	/*
 	 * Create and initialize the spa structure.
 	 */
 	mutex_enter(&spa_namespace_lock);
 	spa = spa_add(TRYIMPORT_NAME, tryconfig, NULL);
 	spa_activate(spa, FREAD);
 
 	/*
 	 * Pass off the heavy lifting to spa_load().
 	 * Pass TRUE for mosconfig because the user-supplied config
 	 * is actually the one to trust when doing an import.
 	 */
 	error = spa_load(spa, SPA_LOAD_TRYIMPORT, SPA_IMPORT_EXISTING, B_TRUE);
 
 	/*
 	 * If 'tryconfig' was at least parsable, return the current config.
 	 */
 	if (spa->spa_root_vdev != NULL) {
 		config = spa_config_generate(spa, NULL, -1ULL, B_TRUE);
 		VERIFY(nvlist_add_string(config, ZPOOL_CONFIG_POOL_NAME,
 		    poolname) == 0);
 		VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_POOL_STATE,
 		    state) == 0);
 		VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_TIMESTAMP,
 		    spa->spa_uberblock.ub_timestamp) == 0);
 
 		/*
 		 * If the bootfs property exists on this pool then we
 		 * copy it out so that external consumers can tell which
 		 * pools are bootable.
 		 */
 		if ((!error || error == EEXIST) && spa->spa_bootfs) {
 			char *tmpname = kmem_alloc(MAXPATHLEN, KM_PUSHPAGE);
 
 			/*
 			 * We have to play games with the name since the
 			 * pool was opened as TRYIMPORT_NAME.
 			 */
 			if (dsl_dsobj_to_dsname(spa_name(spa),
 			    spa->spa_bootfs, tmpname) == 0) {
 				char *cp;
 				char *dsname = kmem_alloc(MAXPATHLEN, KM_PUSHPAGE);
 
 				cp = strchr(tmpname, '/');
 				if (cp == NULL) {
 					(void) strlcpy(dsname, tmpname,
 					    MAXPATHLEN);
 				} else {
 					(void) snprintf(dsname, MAXPATHLEN,
 					    "%s/%s", poolname, ++cp);
 				}
 				VERIFY(nvlist_add_string(config,
 				    ZPOOL_CONFIG_BOOTFS, dsname) == 0);
 				kmem_free(dsname, MAXPATHLEN);
 			}
 			kmem_free(tmpname, MAXPATHLEN);
 		}
 
 		/*
 		 * Add the list of hot spares and level 2 cache devices.
 		 */
 		spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
 		spa_add_spares(spa, config);
 		spa_add_l2cache(spa, config);
 		spa_config_exit(spa, SCL_CONFIG, FTAG);
 	}
 
 	spa_unload(spa);
 	spa_deactivate(spa);
 	spa_remove(spa);
 	mutex_exit(&spa_namespace_lock);
 
 	return (config);
 }
 
 /*
  * Pool export/destroy
  *
  * The act of destroying or exporting a pool is very simple.  We make sure there
  * is no more pending I/O and any references to the pool are gone.  Then, we
  * update the pool state and sync all the labels to disk, removing the
  * configuration from the cache afterwards. If the 'hardforce' flag is set, then
  * we don't sync the labels or remove the configuration cache.
  */
 static int
 spa_export_common(char *pool, int new_state, nvlist_t **oldconfig,
     boolean_t force, boolean_t hardforce)
 {
 	spa_t *spa;
 
 	if (oldconfig)
 		*oldconfig = NULL;
 
 	if (!(spa_mode_global & FWRITE))
 		return (EROFS);
 
 	mutex_enter(&spa_namespace_lock);
 	if ((spa = spa_lookup(pool)) == NULL) {
 		mutex_exit(&spa_namespace_lock);
 		return (ENOENT);
 	}
 
 	/*
 	 * Put a hold on the pool, drop the namespace lock, stop async tasks,
 	 * reacquire the namespace lock, and see if we can export.
 	 */
 	spa_open_ref(spa, FTAG);
 	mutex_exit(&spa_namespace_lock);
 	spa_async_suspend(spa);
 	mutex_enter(&spa_namespace_lock);
 	spa_close(spa, FTAG);
 
 	/*
 	 * The pool will be in core if it's openable,
 	 * in which case we can modify its state.
 	 */
 	if (spa->spa_state != POOL_STATE_UNINITIALIZED && spa->spa_sync_on) {
 		/*
 		 * Objsets may be open only because they're dirty, so we
 		 * have to force it to sync before checking spa_refcnt.
 		 */
 		txg_wait_synced(spa->spa_dsl_pool, 0);
 
 		/*
 		 * A pool cannot be exported or destroyed if there are active
 		 * references.  If we are resetting a pool, allow references by
 		 * fault injection handlers.
 		 */
 		if (!spa_refcount_zero(spa) ||
 		    (spa->spa_inject_ref != 0 &&
 		    new_state != POOL_STATE_UNINITIALIZED)) {
 			spa_async_resume(spa);
 			mutex_exit(&spa_namespace_lock);
 			return (EBUSY);
 		}
 
 		/*
 		 * A pool cannot be exported if it has an active shared spare.
 		 * This is to prevent other pools stealing the active spare
 		 * from an exported pool. At user's own will, such pool can
 		 * be forcedly exported.
 		 */
 		if (!force && new_state == POOL_STATE_EXPORTED &&
 		    spa_has_active_shared_spare(spa)) {
 			spa_async_resume(spa);
 			mutex_exit(&spa_namespace_lock);
 			return (EXDEV);
 		}
 
 		/*
 		 * We want this to be reflected on every label,
 		 * so mark them all dirty.  spa_unload() will do the
 		 * final sync that pushes these changes out.
 		 */
 		if (new_state != POOL_STATE_UNINITIALIZED && !hardforce) {
 			spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 			spa->spa_state = new_state;
 			spa->spa_final_txg = spa_last_synced_txg(spa) +
 			    TXG_DEFER_SIZE + 1;
 			vdev_config_dirty(spa->spa_root_vdev);
 			spa_config_exit(spa, SCL_ALL, FTAG);
 		}
 	}
 
 	spa_event_notify(spa, NULL, FM_EREPORT_ZFS_POOL_DESTROY);
 
 	if (spa->spa_state != POOL_STATE_UNINITIALIZED) {
 		spa_unload(spa);
 		spa_deactivate(spa);
 	}
 
 	if (oldconfig && spa->spa_config)
 		VERIFY(nvlist_dup(spa->spa_config, oldconfig, 0) == 0);
 
 	if (new_state != POOL_STATE_UNINITIALIZED) {
 		if (!hardforce)
 			spa_config_sync(spa, B_TRUE, B_TRUE);
 		spa_remove(spa);
 	}
 	mutex_exit(&spa_namespace_lock);
 
 	return (0);
 }
 
 /*
  * Destroy a storage pool.
  */
 int
 spa_destroy(char *pool)
 {
 	return (spa_export_common(pool, POOL_STATE_DESTROYED, NULL,
 	    B_FALSE, B_FALSE));
 }
 
 /*
  * Export a storage pool.
  */
 int
 spa_export(char *pool, nvlist_t **oldconfig, boolean_t force,
     boolean_t hardforce)
 {
 	return (spa_export_common(pool, POOL_STATE_EXPORTED, oldconfig,
 	    force, hardforce));
 }
 
 /*
  * Similar to spa_export(), this unloads the spa_t without actually removing it
  * from the namespace in any way.
  */
 int
 spa_reset(char *pool)
 {
 	return (spa_export_common(pool, POOL_STATE_UNINITIALIZED, NULL,
 	    B_FALSE, B_FALSE));
 }
 
 /*
  * ==========================================================================
  * Device manipulation
  * ==========================================================================
  */
 
 /*
  * Add a device to a storage pool.
  */
 int
 spa_vdev_add(spa_t *spa, nvlist_t *nvroot)
 {
 	uint64_t txg, id;
 	int error;
 	vdev_t *rvd = spa->spa_root_vdev;
 	vdev_t *vd, *tvd;
 	nvlist_t **spares, **l2cache;
 	uint_t nspares, nl2cache;
 	int c;
 
 	ASSERT(spa_writeable(spa));
 
 	txg = spa_vdev_enter(spa);
 
 	if ((error = spa_config_parse(spa, &vd, nvroot, NULL, 0,
 	    VDEV_ALLOC_ADD)) != 0)
 		return (spa_vdev_exit(spa, NULL, txg, error));
 
 	spa->spa_pending_vdev = vd;	/* spa_vdev_exit() will clear this */
 
 	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES, &spares,
 	    &nspares) != 0)
 		nspares = 0;
 
 	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_L2CACHE, &l2cache,
 	    &nl2cache) != 0)
 		nl2cache = 0;
 
 	if (vd->vdev_children == 0 && nspares == 0 && nl2cache == 0)
 		return (spa_vdev_exit(spa, vd, txg, EINVAL));
 
 	if (vd->vdev_children != 0 &&
 	    (error = vdev_create(vd, txg, B_FALSE)) != 0)
 		return (spa_vdev_exit(spa, vd, txg, error));
 
 	/*
 	 * We must validate the spares and l2cache devices after checking the
 	 * children.  Otherwise, vdev_inuse() will blindly overwrite the spare.
 	 */
 	if ((error = spa_validate_aux(spa, nvroot, txg, VDEV_ALLOC_ADD)) != 0)
 		return (spa_vdev_exit(spa, vd, txg, error));
 
 	/*
 	 * Transfer each new top-level vdev from vd to rvd.
 	 */
 	for (c = 0; c < vd->vdev_children; c++) {
 
 		/*
 		 * Set the vdev id to the first hole, if one exists.
 		 */
 		for (id = 0; id < rvd->vdev_children; id++) {
 			if (rvd->vdev_child[id]->vdev_ishole) {
 				vdev_free(rvd->vdev_child[id]);
 				break;
 			}
 		}
 		tvd = vd->vdev_child[c];
 		vdev_remove_child(vd, tvd);
 		tvd->vdev_id = id;
 		vdev_add_child(rvd, tvd);
 		vdev_config_dirty(tvd);
 	}
 
 	if (nspares != 0) {
 		spa_set_aux_vdevs(&spa->spa_spares, spares, nspares,
 		    ZPOOL_CONFIG_SPARES);
 		spa_load_spares(spa);
 		spa->spa_spares.sav_sync = B_TRUE;
 	}
 
 	if (nl2cache != 0) {
 		spa_set_aux_vdevs(&spa->spa_l2cache, l2cache, nl2cache,
 		    ZPOOL_CONFIG_L2CACHE);
 		spa_load_l2cache(spa);
 		spa->spa_l2cache.sav_sync = B_TRUE;
 	}
 
 	/*
 	 * We have to be careful when adding new vdevs to an existing pool.
 	 * If other threads start allocating from these vdevs before we
 	 * sync the config cache, and we lose power, then upon reboot we may
 	 * fail to open the pool because there are DVAs that the config cache
 	 * can't translate.  Therefore, we first add the vdevs without
 	 * initializing metaslabs; sync the config cache (via spa_vdev_exit());
 	 * and then let spa_config_update() initialize the new metaslabs.
 	 *
 	 * spa_load() checks for added-but-not-initialized vdevs, so that
 	 * if we lose power at any point in this sequence, the remaining
 	 * steps will be completed the next time we load the pool.
 	 */
 	(void) spa_vdev_exit(spa, vd, txg, 0);
 
 	mutex_enter(&spa_namespace_lock);
 	spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
 	mutex_exit(&spa_namespace_lock);
 
 	return (0);
 }
 
 /*
  * Attach a device to a mirror.  The arguments are the path to any device
  * in the mirror, and the nvroot for the new device.  If the path specifies
  * a device that is not mirrored, we automatically insert the mirror vdev.
  *
  * If 'replacing' is specified, the new device is intended to replace the
  * existing device; in this case the two devices are made into their own
  * mirror using the 'replacing' vdev, which is functionally identical to
  * the mirror vdev (it actually reuses all the same ops) but has a few
  * extra rules: you can't attach to it after it's been created, and upon
  * completion of resilvering, the first disk (the one being replaced)
  * is automatically detached.
  */
 int
 spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing)
 {
 	uint64_t txg, dtl_max_txg;
 	ASSERTV(vdev_t *rvd = spa->spa_root_vdev;)
 	vdev_t *oldvd, *newvd, *newrootvd, *pvd, *tvd;
 	vdev_ops_t *pvops;
 	char *oldvdpath, *newvdpath;
 	int newvd_isspare;
 	int error;
 
 	ASSERT(spa_writeable(spa));
 
 	txg = spa_vdev_enter(spa);
 
 	oldvd = spa_lookup_by_guid(spa, guid, B_FALSE);
 
 	if (oldvd == NULL)
 		return (spa_vdev_exit(spa, NULL, txg, ENODEV));
 
 	if (!oldvd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));
 
 	pvd = oldvd->vdev_parent;
 
 	if ((error = spa_config_parse(spa, &newrootvd, nvroot, NULL, 0,
 	    VDEV_ALLOC_ATTACH)) != 0)
 		return (spa_vdev_exit(spa, NULL, txg, EINVAL));
 
 	if (newrootvd->vdev_children != 1)
 		return (spa_vdev_exit(spa, newrootvd, txg, EINVAL));
 
 	newvd = newrootvd->vdev_child[0];
 
 	if (!newvd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_exit(spa, newrootvd, txg, EINVAL));
 
 	if ((error = vdev_create(newrootvd, txg, replacing)) != 0)
 		return (spa_vdev_exit(spa, newrootvd, txg, error));
 
 	/*
 	 * Spares can't replace logs
 	 */
 	if (oldvd->vdev_top->vdev_islog && newvd->vdev_isspare)
 		return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
 
 	if (!replacing) {
 		/*
 		 * For attach, the only allowable parent is a mirror or the root
 		 * vdev.
 		 */
 		if (pvd->vdev_ops != &vdev_mirror_ops &&
 		    pvd->vdev_ops != &vdev_root_ops)
 			return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
 
 		pvops = &vdev_mirror_ops;
 	} else {
 		/*
 		 * Active hot spares can only be replaced by inactive hot
 		 * spares.
 		 */
 		if (pvd->vdev_ops == &vdev_spare_ops &&
 		    oldvd->vdev_isspare &&
 		    !spa_has_spare(spa, newvd->vdev_guid))
 			return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
 
 		/*
 		 * If the source is a hot spare, and the parent isn't already a
 		 * spare, then we want to create a new hot spare.  Otherwise, we
 		 * want to create a replacing vdev.  The user is not allowed to
 		 * attach to a spared vdev child unless the 'isspare' state is
 		 * the same (spare replaces spare, non-spare replaces
 		 * non-spare).
 		 */
 		if (pvd->vdev_ops == &vdev_replacing_ops &&
 		    spa_version(spa) < SPA_VERSION_MULTI_REPLACE) {
 			return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
 		} else if (pvd->vdev_ops == &vdev_spare_ops &&
 		    newvd->vdev_isspare != oldvd->vdev_isspare) {
 			return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
 		}
 
 		if (newvd->vdev_isspare)
 			pvops = &vdev_spare_ops;
 		else
 			pvops = &vdev_replacing_ops;
 	}
 
 	/*
 	 * Make sure the new device is big enough.
 	 */
 	if (newvd->vdev_asize < vdev_get_min_asize(oldvd))
 		return (spa_vdev_exit(spa, newrootvd, txg, EOVERFLOW));
 
 	/*
 	 * The new device cannot have a higher alignment requirement
 	 * than the top-level vdev.
 	 */
 	if (newvd->vdev_ashift > oldvd->vdev_top->vdev_ashift)
 		return (spa_vdev_exit(spa, newrootvd, txg, EDOM));
 
 	/*
 	 * If this is an in-place replacement, update oldvd's path and devid
 	 * to make it distinguishable from newvd, and unopenable from now on.
 	 */
 	if (strcmp(oldvd->vdev_path, newvd->vdev_path) == 0) {
 		spa_strfree(oldvd->vdev_path);
 		oldvd->vdev_path = kmem_alloc(strlen(newvd->vdev_path) + 5,
 		    KM_PUSHPAGE);
 		(void) sprintf(oldvd->vdev_path, "%s/%s",
 		    newvd->vdev_path, "old");
 		if (oldvd->vdev_devid != NULL) {
 			spa_strfree(oldvd->vdev_devid);
 			oldvd->vdev_devid = NULL;
 		}
 	}
 
 	/* mark the device being resilvered */
 	newvd->vdev_resilvering = B_TRUE;
 
 	/*
 	 * If the parent is not a mirror, or if we're replacing, insert the new
 	 * mirror/replacing/spare vdev above oldvd.
 	 */
 	if (pvd->vdev_ops != pvops)
 		pvd = vdev_add_parent(oldvd, pvops);
 
 	ASSERT(pvd->vdev_top->vdev_parent == rvd);
 	ASSERT(pvd->vdev_ops == pvops);
 	ASSERT(oldvd->vdev_parent == pvd);
 
 	/*
 	 * Extract the new device from its root and add it to pvd.
 	 */
 	vdev_remove_child(newrootvd, newvd);
 	newvd->vdev_id = pvd->vdev_children;
 	newvd->vdev_crtxg = oldvd->vdev_crtxg;
 	vdev_add_child(pvd, newvd);
 
 	tvd = newvd->vdev_top;
 	ASSERT(pvd->vdev_top == tvd);
 	ASSERT(tvd->vdev_parent == rvd);
 
 	vdev_config_dirty(tvd);
 
 	/*
 	 * Set newvd's DTL to [TXG_INITIAL, dtl_max_txg) so that we account
 	 * for any dmu_sync-ed blocks.  It will propagate upward when
 	 * spa_vdev_exit() calls vdev_dtl_reassess().
 	 */
 	dtl_max_txg = txg + TXG_CONCURRENT_STATES;
 
 	vdev_dtl_dirty(newvd, DTL_MISSING, TXG_INITIAL,
 	    dtl_max_txg - TXG_INITIAL);
 
 	if (newvd->vdev_isspare) {
 		spa_spare_activate(newvd);
 		spa_event_notify(spa, newvd, FM_EREPORT_ZFS_DEVICE_SPARE);
 	}
 
 	oldvdpath = spa_strdup(oldvd->vdev_path);
 	newvdpath = spa_strdup(newvd->vdev_path);
 	newvd_isspare = newvd->vdev_isspare;
 
 	/*
 	 * Mark newvd's DTL dirty in this txg.
 	 */
 	vdev_dirty(tvd, VDD_DTL, newvd, txg);
 
 	/*
 	 * Restart the resilver
 	 */
 	dsl_resilver_restart(spa->spa_dsl_pool, dtl_max_txg);
 
 	/*
 	 * Commit the config
 	 */
 	(void) spa_vdev_exit(spa, newrootvd, dtl_max_txg, 0);
 
 	spa_history_log_internal(LOG_POOL_VDEV_ATTACH, spa, NULL,
 	    "%s vdev=%s %s vdev=%s",
 	    replacing && newvd_isspare ? "spare in" :
 	    replacing ? "replace" : "attach", newvdpath,
 	    replacing ? "for" : "to", oldvdpath);
 
 	spa_strfree(oldvdpath);
 	spa_strfree(newvdpath);
 
 	if (spa->spa_bootfs)
 		spa_event_notify(spa, newvd, FM_EREPORT_ZFS_BOOTFS_VDEV_ATTACH);
 
 	return (0);
 }
 
 /*
  * Detach a device from a mirror or replacing vdev.
  * If 'replace_done' is specified, only detach if the parent
  * is a replacing vdev.
  */
 int
 spa_vdev_detach(spa_t *spa, uint64_t guid, uint64_t pguid, int replace_done)
 {
 	uint64_t txg;
 	int error;
 	ASSERTV(vdev_t *rvd = spa->spa_root_vdev;)
 	vdev_t *vd, *pvd, *cvd, *tvd;
 	boolean_t unspare = B_FALSE;
 	uint64_t unspare_guid = 0;
 	char *vdpath;
 	int c, t;
 
 	ASSERT(spa_writeable(spa));
 
 	txg = spa_vdev_enter(spa);
 
 	vd = spa_lookup_by_guid(spa, guid, B_FALSE);
 
 	if (vd == NULL)
 		return (spa_vdev_exit(spa, NULL, txg, ENODEV));
 
 	if (!vd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));
 
 	pvd = vd->vdev_parent;
 
 	/*
 	 * If the parent/child relationship is not as expected, don't do it.
 	 * Consider M(A,R(B,C)) -- that is, a mirror of A with a replacing
 	 * vdev that's replacing B with C.  The user's intent in replacing
 	 * is to go from M(A,B) to M(A,C).  If the user decides to cancel
 	 * the replace by detaching C, the expected behavior is to end up
 	 * M(A,B).  But suppose that right after deciding to detach C,
 	 * the replacement of B completes.  We would have M(A,C), and then
 	 * ask to detach C, which would leave us with just A -- not what
 	 * the user wanted.  To prevent this, we make sure that the
 	 * parent/child relationship hasn't changed -- in this example,
 	 * that C's parent is still the replacing vdev R.
 	 */
 	if (pvd->vdev_guid != pguid && pguid != 0)
 		return (spa_vdev_exit(spa, NULL, txg, EBUSY));
 
 	/*
 	 * Only 'replacing' or 'spare' vdevs can be replaced.
 	 */
 	if (replace_done && pvd->vdev_ops != &vdev_replacing_ops &&
 	    pvd->vdev_ops != &vdev_spare_ops)
 		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));
 
 	ASSERT(pvd->vdev_ops != &vdev_spare_ops ||
 	    spa_version(spa) >= SPA_VERSION_SPARES);
 
 	/*
 	 * Only mirror, replacing, and spare vdevs support detach.
 	 */
 	if (pvd->vdev_ops != &vdev_replacing_ops &&
 	    pvd->vdev_ops != &vdev_mirror_ops &&
 	    pvd->vdev_ops != &vdev_spare_ops)
 		return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));
 
 	/*
 	 * If this device has the only valid copy of some data,
 	 * we cannot safely detach it.
 	 */
 	if (vdev_dtl_required(vd))
 		return (spa_vdev_exit(spa, NULL, txg, EBUSY));
 
 	ASSERT(pvd->vdev_children >= 2);
 
 	/*
 	 * If we are detaching the second disk from a replacing vdev, then
 	 * check to see if we changed the original vdev's path to have "/old"
 	 * at the end in spa_vdev_attach().  If so, undo that change now.
 	 */
 	if (pvd->vdev_ops == &vdev_replacing_ops && vd->vdev_id > 0 &&
 	    vd->vdev_path != NULL) {
 		size_t len = strlen(vd->vdev_path);
 
 		for (c = 0; c < pvd->vdev_children; c++) {
 			cvd = pvd->vdev_child[c];
 
 			if (cvd == vd || cvd->vdev_path == NULL)
 				continue;
 
 			if (strncmp(cvd->vdev_path, vd->vdev_path, len) == 0 &&
 			    strcmp(cvd->vdev_path + len, "/old") == 0) {
 				spa_strfree(cvd->vdev_path);
 				cvd->vdev_path = spa_strdup(vd->vdev_path);
 				break;
 			}
 		}
 	}
 
 	/*
 	 * If we are detaching the original disk from a spare, then it implies
 	 * that the spare should become a real disk, and be removed from the
 	 * active spare list for the pool.
 	 */
 	if (pvd->vdev_ops == &vdev_spare_ops &&
 	    vd->vdev_id == 0 &&
 	    pvd->vdev_child[pvd->vdev_children - 1]->vdev_isspare)
 		unspare = B_TRUE;
 
 	/*
 	 * Erase the disk labels so the disk can be used for other things.
 	 * This must be done after all other error cases are handled,
 	 * but before we disembowel vd (so we can still do I/O to it).
 	 * But if we can't do it, don't treat the error as fatal --
 	 * it may be that the unwritability of the disk is the reason
 	 * it's being detached!
 	 */
 	error = vdev_label_init(vd, 0, VDEV_LABEL_REMOVE);
 
 	/*
 	 * Remove vd from its parent and compact the parent's children.
 	 */
 	vdev_remove_child(pvd, vd);
 	vdev_compact_children(pvd);
 
 	/*
 	 * Remember one of the remaining children so we can get tvd below.
 	 */
 	cvd = pvd->vdev_child[pvd->vdev_children - 1];
 
 	/*
 	 * If we need to remove the remaining child from the list of hot spares,
 	 * do it now, marking the vdev as no longer a spare in the process.
 	 * We must do this before vdev_remove_parent(), because that can
 	 * change the GUID if it creates a new toplevel GUID.  For a similar
 	 * reason, we must remove the spare now, in the same txg as the detach;
 	 * otherwise someone could attach a new sibling, change the GUID, and
 	 * the subsequent attempt to spa_vdev_remove(unspare_guid) would fail.
 	 */
 	if (unspare) {
 		ASSERT(cvd->vdev_isspare);
 		spa_spare_remove(cvd);
 		unspare_guid = cvd->vdev_guid;
 		(void) spa_vdev_remove(spa, unspare_guid, B_TRUE);
 		cvd->vdev_unspare = B_TRUE;
 	}
 
 	/*
 	 * If the parent mirror/replacing vdev only has one child,
 	 * the parent is no longer needed.  Remove it from the tree.
 	 */
 	if (pvd->vdev_children == 1) {
 		if (pvd->vdev_ops == &vdev_spare_ops)
 			cvd->vdev_unspare = B_FALSE;
 		vdev_remove_parent(cvd);
 		cvd->vdev_resilvering = B_FALSE;
 	}
 
 
 	/*
 	 * We don't set tvd until now because the parent we just removed
 	 * may have been the previous top-level vdev.
 	 */
 	tvd = cvd->vdev_top;
 	ASSERT(tvd->vdev_parent == rvd);
 
 	/*
 	 * Reevaluate the parent vdev state.
 	 */
 	vdev_propagate_state(cvd);
 
 	/*
 	 * If the 'autoexpand' property is set on the pool then automatically
 	 * try to expand the size of the pool. For example if the device we
 	 * just detached was smaller than the others, it may be possible to
 	 * add metaslabs (i.e. grow the pool). We need to reopen the vdev
 	 * first so that we can obtain the updated sizes of the leaf vdevs.
 	 */
 	if (spa->spa_autoexpand) {
 		vdev_reopen(tvd);
 		vdev_expand(tvd, txg);
 	}
 
 	vdev_config_dirty(tvd);
 
 	/*
 	 * Mark vd's DTL as dirty in this txg.  vdev_dtl_sync() will see that
 	 * vd->vdev_detached is set and free vd's DTL object in syncing context.
 	 * But first make sure we're not on any *other* txg's DTL list, to
 	 * prevent vd from being accessed after it's freed.
 	 */
 	vdpath = spa_strdup(vd->vdev_path);
 	for (t = 0; t < TXG_SIZE; t++)
 		(void) txg_list_remove_this(&tvd->vdev_dtl_list, vd, t);
 	vd->vdev_detached = B_TRUE;
 	vdev_dirty(tvd, VDD_DTL, vd, txg);
 
 	spa_event_notify(spa, vd, FM_EREPORT_ZFS_DEVICE_REMOVE);
 
 	/* hang on to the spa before we release the lock */
 	spa_open_ref(spa, FTAG);
 
 	error = spa_vdev_exit(spa, vd, txg, 0);
 
 	spa_history_log_internal(LOG_POOL_VDEV_DETACH, spa, NULL,
 	    "vdev=%s", vdpath);
 	spa_strfree(vdpath);
 
 	/*
 	 * If this was the removal of the original device in a hot spare vdev,
 	 * then we want to go through and remove the device from the hot spare
 	 * list of every other pool.
 	 */
 	if (unspare) {
 		spa_t *altspa = NULL;
 
 		mutex_enter(&spa_namespace_lock);
 		while ((altspa = spa_next(altspa)) != NULL) {
 			if (altspa->spa_state != POOL_STATE_ACTIVE ||
 			    altspa == spa)
 				continue;
 
 			spa_open_ref(altspa, FTAG);
 			mutex_exit(&spa_namespace_lock);
 			(void) spa_vdev_remove(altspa, unspare_guid, B_TRUE);
 			mutex_enter(&spa_namespace_lock);
 			spa_close(altspa, FTAG);
 		}
 		mutex_exit(&spa_namespace_lock);
 
 		/* search the rest of the vdevs for spares to remove */
 		spa_vdev_resilver_done(spa);
 	}
 
 	/* all done with the spa; OK to release */
 	mutex_enter(&spa_namespace_lock);
 	spa_close(spa, FTAG);
 	mutex_exit(&spa_namespace_lock);
 
 	return (error);
 }
 
 /*
  * Split a set of devices from their mirrors, and create a new pool from them.
  */
 int
 spa_vdev_split_mirror(spa_t *spa, char *newname, nvlist_t *config,
     nvlist_t *props, boolean_t exp)
 {
 	int error = 0;
 	uint64_t txg, *glist;
 	spa_t *newspa;
 	uint_t c, children, lastlog;
 	nvlist_t **child, *nvl, *tmp;
 	dmu_tx_t *tx;
 	char *altroot = NULL;
 	vdev_t *rvd, **vml = NULL;			/* vdev modify list */
 	boolean_t activate_slog;
 
 	ASSERT(spa_writeable(spa));
 
 	txg = spa_vdev_enter(spa);
 
 	/* clear the log and flush everything up to now */
 	activate_slog = spa_passivate_log(spa);
 	(void) spa_vdev_config_exit(spa, NULL, txg, 0, FTAG);
 	error = spa_offline_log(spa);
 	txg = spa_vdev_config_enter(spa);
 
 	if (activate_slog)
 		spa_activate_log(spa);
 
 	if (error != 0)
 		return (spa_vdev_exit(spa, NULL, txg, error));
 
 	/* check new spa name before going any further */
 	if (spa_lookup(newname) != NULL)
 		return (spa_vdev_exit(spa, NULL, txg, EEXIST));
 
 	/*
 	 * scan through all the children to ensure they're all mirrors
 	 */
 	if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &nvl) != 0 ||
 	    nvlist_lookup_nvlist_array(nvl, ZPOOL_CONFIG_CHILDREN, &child,
 	    &children) != 0)
 		return (spa_vdev_exit(spa, NULL, txg, EINVAL));
 
 	/* first, check to ensure we've got the right child count */
 	rvd = spa->spa_root_vdev;
 	lastlog = 0;
 	for (c = 0; c < rvd->vdev_children; c++) {
 		vdev_t *vd = rvd->vdev_child[c];
 
 		/* don't count the holes & logs as children */
 		if (vd->vdev_islog || vd->vdev_ishole) {
 			if (lastlog == 0)
 				lastlog = c;
 			continue;
 		}
 
 		lastlog = 0;
 	}
 	if (children != (lastlog != 0 ? lastlog : rvd->vdev_children))
 		return (spa_vdev_exit(spa, NULL, txg, EINVAL));
 
 	/* next, ensure no spare or cache devices are part of the split */
 	if (nvlist_lookup_nvlist(nvl, ZPOOL_CONFIG_SPARES, &tmp) == 0 ||
 	    nvlist_lookup_nvlist(nvl, ZPOOL_CONFIG_L2CACHE, &tmp) == 0)
 		return (spa_vdev_exit(spa, NULL, txg, EINVAL));
 
 	vml = kmem_zalloc(children * sizeof (vdev_t *), KM_PUSHPAGE);
 	glist = kmem_zalloc(children * sizeof (uint64_t), KM_PUSHPAGE);
 
 	/* then, loop over each vdev and validate it */
 	for (c = 0; c < children; c++) {
 		uint64_t is_hole = 0;
 
 		(void) nvlist_lookup_uint64(child[c], ZPOOL_CONFIG_IS_HOLE,
 		    &is_hole);
 
 		if (is_hole != 0) {
 			if (spa->spa_root_vdev->vdev_child[c]->vdev_ishole ||
 			    spa->spa_root_vdev->vdev_child[c]->vdev_islog) {
 				continue;
 			} else {
 				error = EINVAL;
 				break;
 			}
 		}
 
 		/* which disk is going to be split? */
 		if (nvlist_lookup_uint64(child[c], ZPOOL_CONFIG_GUID,
 		    &glist[c]) != 0) {
 			error = EINVAL;
 			break;
 		}
 
 		/* look it up in the spa */
 		vml[c] = spa_lookup_by_guid(spa, glist[c], B_FALSE);
 		if (vml[c] == NULL) {
 			error = ENODEV;
 			break;
 		}
 
 		/* make sure there's nothing stopping the split */
 		if (vml[c]->vdev_parent->vdev_ops != &vdev_mirror_ops ||
 		    vml[c]->vdev_islog ||
 		    vml[c]->vdev_ishole ||
 		    vml[c]->vdev_isspare ||
 		    vml[c]->vdev_isl2cache ||
 		    !vdev_writeable(vml[c]) ||
 		    vml[c]->vdev_children != 0 ||
 		    vml[c]->vdev_state != VDEV_STATE_HEALTHY ||
 		    c != spa->spa_root_vdev->vdev_child[c]->vdev_id) {
 			error = EINVAL;
 			break;
 		}
 
 		if (vdev_dtl_required(vml[c])) {
 			error = EBUSY;
 			break;
 		}
 
 		/* we need certain info from the top level */
 		VERIFY(nvlist_add_uint64(child[c], ZPOOL_CONFIG_METASLAB_ARRAY,
 		    vml[c]->vdev_top->vdev_ms_array) == 0);
 		VERIFY(nvlist_add_uint64(child[c], ZPOOL_CONFIG_METASLAB_SHIFT,
 		    vml[c]->vdev_top->vdev_ms_shift) == 0);
 		VERIFY(nvlist_add_uint64(child[c], ZPOOL_CONFIG_ASIZE,
 		    vml[c]->vdev_top->vdev_asize) == 0);
 		VERIFY(nvlist_add_uint64(child[c], ZPOOL_CONFIG_ASHIFT,
 		    vml[c]->vdev_top->vdev_ashift) == 0);
 	}
 
 	if (error != 0) {
 		kmem_free(vml, children * sizeof (vdev_t *));
 		kmem_free(glist, children * sizeof (uint64_t));
 		return (spa_vdev_exit(spa, NULL, txg, error));
 	}
 
 	/* stop writers from using the disks */
 	for (c = 0; c < children; c++) {
 		if (vml[c] != NULL)
 			vml[c]->vdev_offline = B_TRUE;
 	}
 	vdev_reopen(spa->spa_root_vdev);
 
 	/*
 	 * Temporarily record the splitting vdevs in the spa config.  This
 	 * will disappear once the config is regenerated.
 	 */
 	VERIFY(nvlist_alloc(&nvl, NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 	VERIFY(nvlist_add_uint64_array(nvl, ZPOOL_CONFIG_SPLIT_LIST,
 	    glist, children) == 0);
 	kmem_free(glist, children * sizeof (uint64_t));
 
 	mutex_enter(&spa->spa_props_lock);
 	VERIFY(nvlist_add_nvlist(spa->spa_config, ZPOOL_CONFIG_SPLIT,
 	    nvl) == 0);
 	mutex_exit(&spa->spa_props_lock);
 	spa->spa_config_splitting = nvl;
 	vdev_config_dirty(spa->spa_root_vdev);
 
 	/* configure and create the new pool */
 	VERIFY(nvlist_add_string(config, ZPOOL_CONFIG_POOL_NAME, newname) == 0);
 	VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_POOL_STATE,
 	    exp ? POOL_STATE_EXPORTED : POOL_STATE_ACTIVE) == 0);
 	VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_VERSION,
 	    spa_version(spa)) == 0);
 	VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_POOL_TXG,
 	    spa->spa_config_txg) == 0);
 	VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_POOL_GUID,
 	    spa_generate_guid(NULL)) == 0);
 	(void) nvlist_lookup_string(props,
 	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
 
 	/* add the new pool to the namespace */
 	newspa = spa_add(newname, config, altroot);
 	newspa->spa_config_txg = spa->spa_config_txg;
 	spa_set_log_state(newspa, SPA_LOG_CLEAR);
 
 	/* release the spa config lock, retaining the namespace lock */
 	spa_vdev_config_exit(spa, NULL, txg, 0, FTAG);
 
 	if (zio_injection_enabled)
 		zio_handle_panic_injection(spa, FTAG, 1);
 
 	spa_activate(newspa, spa_mode_global);
 	spa_async_suspend(newspa);
 
 	/* create the new pool from the disks of the original pool */
 	error = spa_load(newspa, SPA_LOAD_IMPORT, SPA_IMPORT_ASSEMBLE, B_TRUE);
 	if (error)
 		goto out;
 
 	/* if that worked, generate a real config for the new pool */
 	if (newspa->spa_root_vdev != NULL) {
 		VERIFY(nvlist_alloc(&newspa->spa_config_splitting,
 		    NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 		VERIFY(nvlist_add_uint64(newspa->spa_config_splitting,
 		    ZPOOL_CONFIG_SPLIT_GUID, spa_guid(spa)) == 0);
 		spa_config_set(newspa, spa_config_generate(newspa, NULL, -1ULL,
 		    B_TRUE));
 	}
 
 	/* set the props */
 	if (props != NULL) {
 		spa_configfile_set(newspa, props, B_FALSE);
 		error = spa_prop_set(newspa, props);
 		if (error)
 			goto out;
 	}
 
 	/* flush everything */
 	txg = spa_vdev_config_enter(newspa);
 	vdev_config_dirty(newspa->spa_root_vdev);
 	(void) spa_vdev_config_exit(newspa, NULL, txg, 0, FTAG);
 
 	if (zio_injection_enabled)
 		zio_handle_panic_injection(spa, FTAG, 2);
 
 	spa_async_resume(newspa);
 
 	/* finally, update the original pool's config */
 	txg = spa_vdev_config_enter(spa);
 	tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
 	error = dmu_tx_assign(tx, TXG_WAIT);
 	if (error != 0)
 		dmu_tx_abort(tx);
 	for (c = 0; c < children; c++) {
 		if (vml[c] != NULL) {
 			vdev_split(vml[c]);
 			if (error == 0)
 				spa_history_log_internal(LOG_POOL_VDEV_DETACH,
 				    spa, tx, "vdev=%s",
 				    vml[c]->vdev_path);
 			vdev_free(vml[c]);
 		}
 	}
 	vdev_config_dirty(spa->spa_root_vdev);
 	spa->spa_config_splitting = NULL;
 	nvlist_free(nvl);
 	if (error == 0)
 		dmu_tx_commit(tx);
 	(void) spa_vdev_exit(spa, NULL, txg, 0);
 
 	if (zio_injection_enabled)
 		zio_handle_panic_injection(spa, FTAG, 3);
 
 	/* split is complete; log a history record */
 	spa_history_log_internal(LOG_POOL_SPLIT, newspa, NULL,
 	    "split new pool %s from pool %s", newname, spa_name(spa));
 
 	kmem_free(vml, children * sizeof (vdev_t *));
 
 	/* if we're not going to mount the filesystems in userland, export */
 	if (exp)
 		error = spa_export_common(newname, POOL_STATE_EXPORTED, NULL,
 		    B_FALSE, B_FALSE);
 
 	return (error);
 
 out:
 	spa_unload(newspa);
 	spa_deactivate(newspa);
 	spa_remove(newspa);
 
 	txg = spa_vdev_config_enter(spa);
 
 	/* re-online all offlined disks */
 	for (c = 0; c < children; c++) {
 		if (vml[c] != NULL)
 			vml[c]->vdev_offline = B_FALSE;
 	}
 	vdev_reopen(spa->spa_root_vdev);
 
 	nvlist_free(spa->spa_config_splitting);
 	spa->spa_config_splitting = NULL;
 	(void) spa_vdev_exit(spa, NULL, txg, error);
 
 	kmem_free(vml, children * sizeof (vdev_t *));
 	return (error);
 }
 
 static nvlist_t *
 spa_nvlist_lookup_by_guid(nvlist_t **nvpp, int count, uint64_t target_guid)
 {
 	int i;
 
 	for (i = 0; i < count; i++) {
 		uint64_t guid;
 
 		VERIFY(nvlist_lookup_uint64(nvpp[i], ZPOOL_CONFIG_GUID,
 		    &guid) == 0);
 
 		if (guid == target_guid)
 			return (nvpp[i]);
 	}
 
 	return (NULL);
 }
 
 static void
 spa_vdev_remove_aux(nvlist_t *config, char *name, nvlist_t **dev, int count,
 	nvlist_t *dev_to_remove)
 {
 	nvlist_t **newdev = NULL;
 	int i, j;
 
 	if (count > 1)
 		newdev = kmem_alloc((count - 1) * sizeof (void *), KM_PUSHPAGE);
 
 	for (i = 0, j = 0; i < count; i++) {
 		if (dev[i] == dev_to_remove)
 			continue;
 		VERIFY(nvlist_dup(dev[i], &newdev[j++], KM_PUSHPAGE) == 0);
 	}
 
 	VERIFY(nvlist_remove(config, name, DATA_TYPE_NVLIST_ARRAY) == 0);
 	VERIFY(nvlist_add_nvlist_array(config, name, newdev, count - 1) == 0);
 
 	for (i = 0; i < count - 1; i++)
 		nvlist_free(newdev[i]);
 
 	if (count > 1)
 		kmem_free(newdev, (count - 1) * sizeof (void *));
 }
 
 /*
  * Evacuate the device.
  */
 static int
 spa_vdev_remove_evacuate(spa_t *spa, vdev_t *vd)
 {
 	uint64_t txg;
 	int error = 0;
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);
 	ASSERT(vd == vd->vdev_top);
 
 	/*
 	 * Evacuate the device.  We don't hold the config lock as writer
 	 * since we need to do I/O but we do keep the
 	 * spa_namespace_lock held.  Once this completes the device
 	 * should no longer have any blocks allocated on it.
 	 */
 	if (vd->vdev_islog) {
 		if (vd->vdev_stat.vs_alloc != 0)
 			error = spa_offline_log(spa);
 	} else {
 		error = ENOTSUP;
 	}
 
 	if (error)
 		return (error);
 
 	/*
 	 * The evacuation succeeded.  Remove any remaining MOS metadata
 	 * associated with this vdev, and wait for these changes to sync.
 	 */
 	ASSERT3U(vd->vdev_stat.vs_alloc, ==, 0);
 	txg = spa_vdev_config_enter(spa);
 	vd->vdev_removing = B_TRUE;
 	vdev_dirty(vd, 0, NULL, txg);
 	vdev_config_dirty(vd);
 	spa_vdev_config_exit(spa, NULL, txg, 0, FTAG);
 
 	return (0);
 }
 
 /*
  * Complete the removal by cleaning up the namespace.
  */
 static void
 spa_vdev_remove_from_namespace(spa_t *spa, vdev_t *vd)
 {
 	vdev_t *rvd = spa->spa_root_vdev;
 	uint64_t id = vd->vdev_id;
 	boolean_t last_vdev = (id == (rvd->vdev_children - 1));
 
 	ASSERT(MUTEX_HELD(&spa_namespace_lock));
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
 	ASSERT(vd == vd->vdev_top);
 
 	/*
 	 * Only remove any devices which are empty.
 	 */
 	if (vd->vdev_stat.vs_alloc != 0)
 		return;
 
 	(void) vdev_label_init(vd, 0, VDEV_LABEL_REMOVE);
 
 	if (list_link_active(&vd->vdev_state_dirty_node))
 		vdev_state_clean(vd);
 	if (list_link_active(&vd->vdev_config_dirty_node))
 		vdev_config_clean(vd);
 
 	vdev_free(vd);
 
 	if (last_vdev) {
 		vdev_compact_children(rvd);
 	} else {
 		vd = vdev_alloc_common(spa, id, 0, &vdev_hole_ops);
 		vdev_add_child(rvd, vd);
 	}
 	vdev_config_dirty(rvd);
 
 	/*
 	 * Reassess the health of our root vdev.
 	 */
 	vdev_reopen(rvd);
 }
 
 /*
  * Remove a device from the pool -
  *
  * Removing a device from the vdev namespace requires several steps
  * and can take a significant amount of time.  As a result we use
  * the spa_vdev_config_[enter/exit] functions which allow us to
  * grab and release the spa_config_lock while still holding the namespace
  * lock.  During each step the configuration is synced out.
  */
 
 /*
  * Remove a device from the pool.  Currently, this supports removing only hot
  * spares, slogs, and level 2 ARC devices.
  */
 int
 spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare)
 {
 	vdev_t *vd;
 	metaslab_group_t *mg;
 	nvlist_t **spares, **l2cache, *nv;
 	uint64_t txg = 0;
 	uint_t nspares, nl2cache;
 	int error = 0;
 	boolean_t locked = MUTEX_HELD(&spa_namespace_lock);
 
 	ASSERT(spa_writeable(spa));
 
 	if (!locked)
 		txg = spa_vdev_enter(spa);
 
 	vd = spa_lookup_by_guid(spa, guid, B_FALSE);
 
 	if (spa->spa_spares.sav_vdevs != NULL &&
 	    nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
 	    ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0 &&
 	    (nv = spa_nvlist_lookup_by_guid(spares, nspares, guid)) != NULL) {
 		/*
 		 * Only remove the hot spare if it's not currently in use
 		 * in this pool.
 		 */
 		if (vd == NULL || unspare) {
 			spa_vdev_remove_aux(spa->spa_spares.sav_config,
 			    ZPOOL_CONFIG_SPARES, spares, nspares, nv);
 			spa_load_spares(spa);
 			spa->spa_spares.sav_sync = B_TRUE;
 		} else {
 			error = EBUSY;
 		}
 	} else if (spa->spa_l2cache.sav_vdevs != NULL &&
 	    nvlist_lookup_nvlist_array(spa->spa_l2cache.sav_config,
 	    ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0 &&
 	    (nv = spa_nvlist_lookup_by_guid(l2cache, nl2cache, guid)) != NULL) {
 		/*
 		 * Cache devices can always be removed.
 		 */
 		spa_vdev_remove_aux(spa->spa_l2cache.sav_config,
 		    ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache, nv);
 		spa_load_l2cache(spa);
 		spa->spa_l2cache.sav_sync = B_TRUE;
 	} else if (vd != NULL && vd->vdev_islog) {
 		ASSERT(!locked);
 		ASSERT(vd == vd->vdev_top);
 
 		/*
 		 * XXX - Once we have bp-rewrite this should
 		 * become the common case.
 		 */
 
 		mg = vd->vdev_mg;
 
 		/*
 		 * Stop allocating from this vdev.
 		 */
 		metaslab_group_passivate(mg);
 
 		/*
 		 * Wait for the youngest allocations and frees to sync,
 		 * and then wait for the deferral of those frees to finish.
 		 */
 		spa_vdev_config_exit(spa, NULL,
 		    txg + TXG_CONCURRENT_STATES + TXG_DEFER_SIZE, 0, FTAG);
 
 		/*
 		 * Attempt to evacuate the vdev.
 		 */
 		error = spa_vdev_remove_evacuate(spa, vd);
 
 		txg = spa_vdev_config_enter(spa);
 
 		/*
 		 * If we couldn't evacuate the vdev, unwind.
 		 */
 		if (error) {
 			metaslab_group_activate(mg);
 			return (spa_vdev_exit(spa, NULL, txg, error));
 		}
 
 		/*
 		 * Clean up the vdev namespace.
 		 */
 		spa_vdev_remove_from_namespace(spa, vd);
 
 	} else if (vd != NULL) {
 		/*
 		 * Normal vdevs cannot be removed (yet).
 		 */
 		error = ENOTSUP;
 	} else {
 		/*
 		 * There is no vdev of any kind with the specified guid.
 		 */
 		error = ENOENT;
 	}
 
 	if (!locked)
 		return (spa_vdev_exit(spa, NULL, txg, error));
 
 	return (error);
 }
 
 /*
  * Find any device that's done replacing, or a vdev marked 'unspare' that's
  * current spared, so we can detach it.
  */
 static vdev_t *
 spa_vdev_resilver_done_hunt(vdev_t *vd)
 {
 	vdev_t *newvd, *oldvd;
 	int c;
 
 	for (c = 0; c < vd->vdev_children; c++) {
 		oldvd = spa_vdev_resilver_done_hunt(vd->vdev_child[c]);
 		if (oldvd != NULL)
 			return (oldvd);
 	}
 
 	/*
 	 * Check for a completed replacement.  We always consider the first
 	 * vdev in the list to be the oldest vdev, and the last one to be
 	 * the newest (see spa_vdev_attach() for how that works).  In
 	 * the case where the newest vdev is faulted, we will not automatically
 	 * remove it after a resilver completes.  This is OK as it will require
 	 * user intervention to determine which disk the admin wishes to keep.
 	 */
 	if (vd->vdev_ops == &vdev_replacing_ops) {
 		ASSERT(vd->vdev_children > 1);
 
 		newvd = vd->vdev_child[vd->vdev_children - 1];
 		oldvd = vd->vdev_child[0];
 
 		if (vdev_dtl_empty(newvd, DTL_MISSING) &&
 		    vdev_dtl_empty(newvd, DTL_OUTAGE) &&
 		    !vdev_dtl_required(oldvd))
 			return (oldvd);
 	}
 
 	/*
 	 * Check for a completed resilver with the 'unspare' flag set.
 	 */
 	if (vd->vdev_ops == &vdev_spare_ops) {
 		vdev_t *first = vd->vdev_child[0];
 		vdev_t *last = vd->vdev_child[vd->vdev_children - 1];
 
 		if (last->vdev_unspare) {
 			oldvd = first;
 			newvd = last;
 		} else if (first->vdev_unspare) {
 			oldvd = last;
 			newvd = first;
 		} else {
 			oldvd = NULL;
 		}
 
 		if (oldvd != NULL &&
 		    vdev_dtl_empty(newvd, DTL_MISSING) &&
 		    vdev_dtl_empty(newvd, DTL_OUTAGE) &&
 		    !vdev_dtl_required(oldvd))
 			return (oldvd);
 
 		/*
 		 * If there are more than two spares attached to a disk,
 		 * and those spares are not required, then we want to
 		 * attempt to free them up now so that they can be used
 		 * by other pools.  Once we're back down to a single
 		 * disk+spare, we stop removing them.
 		 */
 		if (vd->vdev_children > 2) {
 			newvd = vd->vdev_child[1];
 
 			if (newvd->vdev_isspare && last->vdev_isspare &&
 			    vdev_dtl_empty(last, DTL_MISSING) &&
 			    vdev_dtl_empty(last, DTL_OUTAGE) &&
 			    !vdev_dtl_required(newvd))
 				return (newvd);
 		}
 	}
 
 	return (NULL);
 }
 
 static void
 spa_vdev_resilver_done(spa_t *spa)
 {
 	vdev_t *vd, *pvd, *ppvd;
 	uint64_t guid, sguid, pguid, ppguid;
 
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 
 	while ((vd = spa_vdev_resilver_done_hunt(spa->spa_root_vdev)) != NULL) {
 		pvd = vd->vdev_parent;
 		ppvd = pvd->vdev_parent;
 		guid = vd->vdev_guid;
 		pguid = pvd->vdev_guid;
 		ppguid = ppvd->vdev_guid;
 		sguid = 0;
 		/*
 		 * If we have just finished replacing a hot spared device, then
 		 * we need to detach the parent's first child (the original hot
 		 * spare) as well.
 		 */
 		if (ppvd->vdev_ops == &vdev_spare_ops && pvd->vdev_id == 0 &&
 		    ppvd->vdev_children == 2) {
 			ASSERT(pvd->vdev_ops == &vdev_replacing_ops);
 			sguid = ppvd->vdev_child[1]->vdev_guid;
 		}
 		spa_config_exit(spa, SCL_ALL, FTAG);
 		if (spa_vdev_detach(spa, guid, pguid, B_TRUE) != 0)
 			return;
 		if (sguid && spa_vdev_detach(spa, sguid, ppguid, B_TRUE) != 0)
 			return;
 		spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 	}
 
 	spa_config_exit(spa, SCL_ALL, FTAG);
 }
 
 /*
  * Update the stored path or FRU for this vdev.
  */
 int
 spa_vdev_set_common(spa_t *spa, uint64_t guid, const char *value,
     boolean_t ispath)
 {
 	vdev_t *vd;
 	boolean_t sync = B_FALSE;
 
 	ASSERT(spa_writeable(spa));
 
 	spa_vdev_state_enter(spa, SCL_ALL);
 
 	if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
 		return (spa_vdev_state_exit(spa, NULL, ENOENT));
 
 	if (!vd->vdev_ops->vdev_op_leaf)
 		return (spa_vdev_state_exit(spa, NULL, ENOTSUP));
 
 	if (ispath) {
 		if (strcmp(value, vd->vdev_path) != 0) {
 			spa_strfree(vd->vdev_path);
 			vd->vdev_path = spa_strdup(value);
 			sync = B_TRUE;
 		}
 	} else {
 		if (vd->vdev_fru == NULL) {
 			vd->vdev_fru = spa_strdup(value);
 			sync = B_TRUE;
 		} else if (strcmp(value, vd->vdev_fru) != 0) {
 			spa_strfree(vd->vdev_fru);
 			vd->vdev_fru = spa_strdup(value);
 			sync = B_TRUE;
 		}
 	}
 
 	return (spa_vdev_state_exit(spa, sync ? vd : NULL, 0));
 }
 
 int
 spa_vdev_setpath(spa_t *spa, uint64_t guid, const char *newpath)
 {
 	return (spa_vdev_set_common(spa, guid, newpath, B_TRUE));
 }
 
 int
 spa_vdev_setfru(spa_t *spa, uint64_t guid, const char *newfru)
 {
 	return (spa_vdev_set_common(spa, guid, newfru, B_FALSE));
 }
 
 /*
  * ==========================================================================
  * SPA Scanning
  * ==========================================================================
  */
 
 int
 spa_scan_stop(spa_t *spa)
 {
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);
 	if (dsl_scan_resilvering(spa->spa_dsl_pool))
 		return (EBUSY);
 	return (dsl_scan_cancel(spa->spa_dsl_pool));
 }
 
 int
 spa_scan(spa_t *spa, pool_scan_func_t func)
 {
 	ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);
 
 	if (func >= POOL_SCAN_FUNCS || func == POOL_SCAN_NONE)
 		return (ENOTSUP);
 
 	/*
 	 * If a resilver was requested, but there is no DTL on a
 	 * writeable leaf device, we have nothing to do.
 	 */
 	if (func == POOL_SCAN_RESILVER &&
 	    !vdev_resilver_needed(spa->spa_root_vdev, NULL, NULL)) {
 		spa_async_request(spa, SPA_ASYNC_RESILVER_DONE);
 		return (0);
 	}
 
 	return (dsl_scan(spa->spa_dsl_pool, func));
 }
 
 /*
  * ==========================================================================
  * SPA async task processing
  * ==========================================================================
  */
 
 static void
 spa_async_remove(spa_t *spa, vdev_t *vd)
 {
 	int c;
 
 	if (vd->vdev_remove_wanted) {
 		vd->vdev_remove_wanted = B_FALSE;
 		vd->vdev_delayed_close = B_FALSE;
 		vdev_set_state(vd, B_FALSE, VDEV_STATE_REMOVED, VDEV_AUX_NONE);
 
 		/*
 		 * We want to clear the stats, but we don't want to do a full
 		 * vdev_clear() as that will cause us to throw away
 		 * degraded/faulted state as well as attempt to reopen the
 		 * device, all of which is a waste.
 		 */
 		vd->vdev_stat.vs_read_errors = 0;
 		vd->vdev_stat.vs_write_errors = 0;
 		vd->vdev_stat.vs_checksum_errors = 0;
 
 		vdev_state_dirty(vd->vdev_top);
 	}
 
 	for (c = 0; c < vd->vdev_children; c++)
 		spa_async_remove(spa, vd->vdev_child[c]);
 }
 
 static void
 spa_async_probe(spa_t *spa, vdev_t *vd)
 {
 	int c;
 
 	if (vd->vdev_probe_wanted) {
 		vd->vdev_probe_wanted = B_FALSE;
 		vdev_reopen(vd);	/* vdev_open() does the actual probe */
 	}
 
 	for (c = 0; c < vd->vdev_children; c++)
 		spa_async_probe(spa, vd->vdev_child[c]);
 }
 
 static void
 spa_async_autoexpand(spa_t *spa, vdev_t *vd)
 {
 	int c;
 
 	if (!spa->spa_autoexpand)
 		return;
 
 	for (c = 0; c < vd->vdev_children; c++) {
 		vdev_t *cvd = vd->vdev_child[c];
 		spa_async_autoexpand(spa, cvd);
 	}
 
 	if (!vd->vdev_ops->vdev_op_leaf || vd->vdev_physpath == NULL)
 		return;
 
 	spa_event_notify(vd->vdev_spa, vd, FM_EREPORT_ZFS_DEVICE_AUTOEXPAND);
 }
 
 static void
 spa_async_thread(spa_t *spa)
 {
 	int tasks, i;
 
 	ASSERT(spa->spa_sync_on);
 
 	mutex_enter(&spa->spa_async_lock);
 	tasks = spa->spa_async_tasks;
 	spa->spa_async_tasks = 0;
 	mutex_exit(&spa->spa_async_lock);
 
 	/*
 	 * See if the config needs to be updated.
 	 */
 	if (tasks & SPA_ASYNC_CONFIG_UPDATE) {
 		uint64_t old_space, new_space;
 
 		mutex_enter(&spa_namespace_lock);
 		old_space = metaslab_class_get_space(spa_normal_class(spa));
 		spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
 		new_space = metaslab_class_get_space(spa_normal_class(spa));
 		mutex_exit(&spa_namespace_lock);
 
 		/*
 		 * If the pool grew as a result of the config update,
 		 * then log an internal history event.
 		 */
 		if (new_space != old_space) {
 			spa_history_log_internal(LOG_POOL_VDEV_ONLINE,
 			    spa, NULL,
 			    "pool '%s' size: %llu(+%llu)",
 			    spa_name(spa), new_space, new_space - old_space);
 		}
 	}
 
 	/*
 	 * See if any devices need to be marked REMOVED.
 	 */
 	if (tasks & SPA_ASYNC_REMOVE) {
 		spa_vdev_state_enter(spa, SCL_NONE);
 		spa_async_remove(spa, spa->spa_root_vdev);
 		for (i = 0; i < spa->spa_l2cache.sav_count; i++)
 			spa_async_remove(spa, spa->spa_l2cache.sav_vdevs[i]);
 		for (i = 0; i < spa->spa_spares.sav_count; i++)
 			spa_async_remove(spa, spa->spa_spares.sav_vdevs[i]);
 		(void) spa_vdev_state_exit(spa, NULL, 0);
 	}
 
 	if ((tasks & SPA_ASYNC_AUTOEXPAND) && !spa_suspended(spa)) {
 		spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
 		spa_async_autoexpand(spa, spa->spa_root_vdev);
 		spa_config_exit(spa, SCL_CONFIG, FTAG);
 	}
 
 	/*
 	 * See if any devices need to be probed.
 	 */
 	if (tasks & SPA_ASYNC_PROBE) {
 		spa_vdev_state_enter(spa, SCL_NONE);
 		spa_async_probe(spa, spa->spa_root_vdev);
 		(void) spa_vdev_state_exit(spa, NULL, 0);
 	}
 
 	/*
 	 * If any devices are done replacing, detach them.
 	 */
 	if (tasks & SPA_ASYNC_RESILVER_DONE)
 		spa_vdev_resilver_done(spa);
 
 	/*
 	 * Kick off a resilver.
 	 */
 	if (tasks & SPA_ASYNC_RESILVER)
 		dsl_resilver_restart(spa->spa_dsl_pool, 0);
 
 	/*
 	 * Let the world know that we're done.
 	 */
 	mutex_enter(&spa->spa_async_lock);
 	spa->spa_async_thread = NULL;
 	cv_broadcast(&spa->spa_async_cv);
 	mutex_exit(&spa->spa_async_lock);
 	thread_exit();
 }
 
 void
 spa_async_suspend(spa_t *spa)
 {
 	mutex_enter(&spa->spa_async_lock);
 	spa->spa_async_suspended++;
 	while (spa->spa_async_thread != NULL)
 		cv_wait(&spa->spa_async_cv, &spa->spa_async_lock);
 	mutex_exit(&spa->spa_async_lock);
 }
 
 void
 spa_async_resume(spa_t *spa)
 {
 	mutex_enter(&spa->spa_async_lock);
 	ASSERT(spa->spa_async_suspended != 0);
 	spa->spa_async_suspended--;
 	mutex_exit(&spa->spa_async_lock);
 }
 
 static void
 spa_async_dispatch(spa_t *spa)
 {
 	mutex_enter(&spa->spa_async_lock);
 	if (spa->spa_async_tasks && !spa->spa_async_suspended &&
 	    spa->spa_async_thread == NULL &&
 	    rootdir != NULL && !vn_is_readonly(rootdir))
 		spa->spa_async_thread = thread_create(NULL, 0,
 		    spa_async_thread, spa, 0, &p0, TS_RUN, maxclsyspri);
 	mutex_exit(&spa->spa_async_lock);
 }
 
 void
 spa_async_request(spa_t *spa, int task)
 {
 	zfs_dbgmsg("spa=%s async request task=%u", spa->spa_name, task);
 	mutex_enter(&spa->spa_async_lock);
 	spa->spa_async_tasks |= task;
 	mutex_exit(&spa->spa_async_lock);
 }
 
 /*
  * ==========================================================================
  * SPA syncing routines
  * ==========================================================================
  */
 
 static int
 bpobj_enqueue_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
 {
 	bpobj_t *bpo = arg;
 	bpobj_enqueue(bpo, bp, tx);
 	return (0);
 }
 
 static int
 spa_free_sync_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
 {
 	zio_t *zio = arg;
 
 	zio_nowait(zio_free_sync(zio, zio->io_spa, dmu_tx_get_txg(tx), bp,
 	    zio->io_flags));
 	return (0);
 }
 
 static void
 spa_sync_nvlist(spa_t *spa, uint64_t obj, nvlist_t *nv, dmu_tx_t *tx)
 {
 	char *packed = NULL;
 	size_t bufsize;
 	size_t nvsize = 0;
 	dmu_buf_t *db;
 
 	VERIFY(nvlist_size(nv, &nvsize, NV_ENCODE_XDR) == 0);
 
 	/*
 	 * Write full (SPA_CONFIG_BLOCKSIZE) blocks of configuration
 	 * information.  This avoids the dbuf_will_dirty() path and
 	 * saves us a pre-read to get data we don't actually care about.
 	 */
 	bufsize = P2ROUNDUP(nvsize, SPA_CONFIG_BLOCKSIZE);
 	packed = vmem_alloc(bufsize, KM_PUSHPAGE);
 
 	VERIFY(nvlist_pack(nv, &packed, &nvsize, NV_ENCODE_XDR,
 	    KM_PUSHPAGE) == 0);
 	bzero(packed + nvsize, bufsize - nvsize);
 
 	dmu_write(spa->spa_meta_objset, obj, 0, bufsize, packed, tx);
 
 	vmem_free(packed, bufsize);
 
 	VERIFY(0 == dmu_bonus_hold(spa->spa_meta_objset, obj, FTAG, &db));
 	dmu_buf_will_dirty(db, tx);
 	*(uint64_t *)db->db_data = nvsize;
 	dmu_buf_rele(db, FTAG);
 }
 
 static void
 spa_sync_aux_dev(spa_t *spa, spa_aux_vdev_t *sav, dmu_tx_t *tx,
     const char *config, const char *entry)
 {
 	nvlist_t *nvroot;
 	nvlist_t **list;
 	int i;
 
 	if (!sav->sav_sync)
 		return;
 
 	/*
 	 * Update the MOS nvlist describing the list of available devices.
 	 * spa_validate_aux() will have already made sure this nvlist is
 	 * valid and the vdevs are labeled appropriately.
 	 */
 	if (sav->sav_object == 0) {
 		sav->sav_object = dmu_object_alloc(spa->spa_meta_objset,
 		    DMU_OT_PACKED_NVLIST, 1 << 14, DMU_OT_PACKED_NVLIST_SIZE,
 		    sizeof (uint64_t), tx);
 		VERIFY(zap_update(spa->spa_meta_objset,
 		    DMU_POOL_DIRECTORY_OBJECT, entry, sizeof (uint64_t), 1,
 		    &sav->sav_object, tx) == 0);
 	}
 
 	VERIFY(nvlist_alloc(&nvroot, NV_UNIQUE_NAME, KM_PUSHPAGE) == 0);
 	if (sav->sav_count == 0) {
 		VERIFY(nvlist_add_nvlist_array(nvroot, config, NULL, 0) == 0);
 	} else {
 		list = kmem_alloc(sav->sav_count * sizeof (void *), KM_PUSHPAGE);
 		for (i = 0; i < sav->sav_count; i++)
 			list[i] = vdev_config_generate(spa, sav->sav_vdevs[i],
 			    B_FALSE, VDEV_CONFIG_L2CACHE);
 		VERIFY(nvlist_add_nvlist_array(nvroot, config, list,
 		    sav->sav_count) == 0);
 		for (i = 0; i < sav->sav_count; i++)
 			nvlist_free(list[i]);
 		kmem_free(list, sav->sav_count * sizeof (void *));
 	}
 
 	spa_sync_nvlist(spa, sav->sav_object, nvroot, tx);
 	nvlist_free(nvroot);
 
 	sav->sav_sync = B_FALSE;
 }
 
 static void
 spa_sync_config_object(spa_t *spa, dmu_tx_t *tx)
 {
 	nvlist_t *config;
 
 	if (list_is_empty(&spa->spa_config_dirty_list))
 		return;
 
 	spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
 
 	config = spa_config_generate(spa, spa->spa_root_vdev,
 	    dmu_tx_get_txg(tx), B_FALSE);
 
 	spa_config_exit(spa, SCL_STATE, FTAG);
 
 	if (spa->spa_config_syncing)
 		nvlist_free(spa->spa_config_syncing);
 	spa->spa_config_syncing = config;
 
 	spa_sync_nvlist(spa, spa->spa_config_object, config, tx);
 }
 
 /*
  * Set zpool properties.
  */
 static void
 spa_sync_props(void *arg1, void *arg2, dmu_tx_t *tx)
 {
 	spa_t *spa = arg1;
 	objset_t *mos = spa->spa_meta_objset;
 	nvlist_t *nvp = arg2;
 	nvpair_t *elem;
 	uint64_t intval;
 	char *strval;
 	zpool_prop_t prop;
 	const char *propname;
 	zprop_type_t proptype;
 
 	mutex_enter(&spa->spa_props_lock);
 
 	elem = NULL;
 	while ((elem = nvlist_next_nvpair(nvp, elem))) {
 		switch (prop = zpool_name_to_prop(nvpair_name(elem))) {
 		case ZPOOL_PROP_VERSION:
 			/*
 			 * Only set version for non-zpool-creation cases
 			 * (set/import). spa_create() needs special care
 			 * for version setting.
 			 */
 			if (tx->tx_txg != TXG_INITIAL) {
 				VERIFY(nvpair_value_uint64(elem,
 				    &intval) == 0);
 				ASSERT(intval <= SPA_VERSION);
 				ASSERT(intval >= spa_version(spa));
 				spa->spa_uberblock.ub_version = intval;
 				vdev_config_dirty(spa->spa_root_vdev);
 			}
 			break;
 
 		case ZPOOL_PROP_ALTROOT:
 			/*
 			 * 'altroot' is a non-persistent property. It should
 			 * have been set temporarily at creation or import time.
 			 */
 			ASSERT(spa->spa_root != NULL);
 			break;
 
 		case ZPOOL_PROP_READONLY:
 		case ZPOOL_PROP_CACHEFILE:
 			/*
 			 * 'readonly' and 'cachefile' are also non-persisitent
 			 * properties.
 			 */
 			break;
 		case ZPOOL_PROP_COMMENT:
 			VERIFY(nvpair_value_string(elem, &strval) == 0);
 			if (spa->spa_comment != NULL)
 				spa_strfree(spa->spa_comment);
 			spa->spa_comment = spa_strdup(strval);
 			/*
 			 * We need to dirty the configuration on all the vdevs
 			 * so that their labels get updated.  It's unnecessary
 			 * to do this for pool creation since the vdev's
 			 * configuratoin has already been dirtied.
 			 */
 			if (tx->tx_txg != TXG_INITIAL)
 				vdev_config_dirty(spa->spa_root_vdev);
 			break;
 		default:
 			/*
 			 * Set pool property values in the poolprops mos object.
 			 */
 			if (spa->spa_pool_props_object == 0) {
 				VERIFY((spa->spa_pool_props_object =
 				    zap_create(mos, DMU_OT_POOL_PROPS,
 				    DMU_OT_NONE, 0, tx)) > 0);
 
 				VERIFY(zap_update(mos,
 				    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_PROPS,
 				    8, 1, &spa->spa_pool_props_object, tx)
 				    == 0);
 			}
 
 			/* normalize the property name */
 			propname = zpool_prop_to_name(prop);
 			proptype = zpool_prop_get_type(prop);
 
 			if (nvpair_type(elem) == DATA_TYPE_STRING) {
 				ASSERT(proptype == PROP_TYPE_STRING);
 				VERIFY(nvpair_value_string(elem, &strval) == 0);
 				VERIFY(zap_update(mos,
 				    spa->spa_pool_props_object, propname,
 				    1, strlen(strval) + 1, strval, tx) == 0);
 
 			} else if (nvpair_type(elem) == DATA_TYPE_UINT64) {
 				VERIFY(nvpair_value_uint64(elem, &intval) == 0);
 
 				if (proptype == PROP_TYPE_INDEX) {
 					const char *unused;
 					VERIFY(zpool_prop_index_to_string(
 					    prop, intval, &unused) == 0);
 				}
 				VERIFY(zap_update(mos,
 				    spa->spa_pool_props_object, propname,
 				    8, 1, &intval, tx) == 0);
 			} else {
 				ASSERT(0); /* not allowed */
 			}
 
 			switch (prop) {
 			case ZPOOL_PROP_DELEGATION:
 				spa->spa_delegation = intval;
 				break;
 			case ZPOOL_PROP_BOOTFS:
 				spa->spa_bootfs = intval;
 				break;
 			case ZPOOL_PROP_FAILUREMODE:
 				spa->spa_failmode = intval;
 				break;
 			case ZPOOL_PROP_AUTOEXPAND:
 				spa->spa_autoexpand = intval;
 				if (tx->tx_txg != TXG_INITIAL)
 					spa_async_request(spa,
 					    SPA_ASYNC_AUTOEXPAND);
 				break;
 			case ZPOOL_PROP_DEDUPDITTO:
 				spa->spa_dedup_ditto = intval;
 				break;
 			default:
 				break;
 			}
 		}
 
 		/* log internal history if this is not a zpool create */
 		if (spa_version(spa) >= SPA_VERSION_ZPOOL_HISTORY &&
 		    tx->tx_txg != TXG_INITIAL) {
 			spa_history_log_internal(LOG_POOL_PROPSET,
 			    spa, tx, "%s %lld %s",
 			    nvpair_name(elem), intval, spa_name(spa));
 		}
 	}
 
 	mutex_exit(&spa->spa_props_lock);
 }
 
 /*
  * Perform one-time upgrade on-disk changes.  spa_version() does not
  * reflect the new version this txg, so there must be no changes this
  * txg to anything that the upgrade code depends on after it executes.
  * Therefore this must be called after dsl_pool_sync() does the sync
  * tasks.
  */
 static void
 spa_sync_upgrades(spa_t *spa, dmu_tx_t *tx)
 {
 	dsl_pool_t *dp = spa->spa_dsl_pool;
 
 	ASSERT(spa->spa_sync_pass == 1);
 
 	if (spa->spa_ubsync.ub_version < SPA_VERSION_ORIGIN &&
 	    spa->spa_uberblock.ub_version >= SPA_VERSION_ORIGIN) {
 		dsl_pool_create_origin(dp, tx);
 
 		/* Keeping the origin open increases spa_minref */
 		spa->spa_minref += 3;
 	}
 
 	if (spa->spa_ubsync.ub_version < SPA_VERSION_NEXT_CLONES &&
 	    spa->spa_uberblock.ub_version >= SPA_VERSION_NEXT_CLONES) {
 		dsl_pool_upgrade_clones(dp, tx);
 	}
 
 	if (spa->spa_ubsync.ub_version < SPA_VERSION_DIR_CLONES &&
 	    spa->spa_uberblock.ub_version >= SPA_VERSION_DIR_CLONES) {
 		dsl_pool_upgrade_dir_clones(dp, tx);
 
 		/* Keeping the freedir open increases spa_minref */
 		spa->spa_minref += 3;
 	}
 }
 
 /*
  * Sync the specified transaction group.  New blocks may be dirtied as
  * part of the process, so we iterate until it converges.
  */
 void
 spa_sync(spa_t *spa, uint64_t txg)
 {
 	dsl_pool_t *dp = spa->spa_dsl_pool;
 	objset_t *mos = spa->spa_meta_objset;
 	bpobj_t *defer_bpo = &spa->spa_deferred_bpobj;
 	bplist_t *free_bpl = &spa->spa_free_bplist[txg & TXG_MASK];
 	vdev_t *rvd = spa->spa_root_vdev;
 	vdev_t *vd;
 	dmu_tx_t *tx;
 	int error;
 	int c;
 
 	VERIFY(spa_writeable(spa));
 
 	/*
 	 * Lock out configuration changes.
 	 */
 	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
 
 	spa->spa_syncing_txg = txg;
 	spa->spa_sync_pass = 0;
 
 	/*
 	 * If there are any pending vdev state changes, convert them
 	 * into config changes that go out with this transaction group.
 	 */
 	spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
 	while (list_head(&spa->spa_state_dirty_list) != NULL) {
 		/*
 		 * We need the write lock here because, for aux vdevs,
 		 * calling vdev_config_dirty() modifies sav_config.
 		 * This is ugly and will become unnecessary when we
 		 * eliminate the aux vdev wart by integrating all vdevs
 		 * into the root vdev tree.
 		 */
 		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
 		spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_WRITER);
 		while ((vd = list_head(&spa->spa_state_dirty_list)) != NULL) {
 			vdev_state_clean(vd);
 			vdev_config_dirty(vd);
 		}
 		spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
 		spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_READER);
 	}
 	spa_config_exit(spa, SCL_STATE, FTAG);
 
 	tx = dmu_tx_create_assigned(dp, txg);
 
 	/*
 	 * If we are upgrading to SPA_VERSION_RAIDZ_DEFLATE this txg,
 	 * set spa_deflate if we have no raid-z vdevs.
 	 */
 	if (spa->spa_ubsync.ub_version < SPA_VERSION_RAIDZ_DEFLATE &&
 	    spa->spa_uberblock.ub_version >= SPA_VERSION_RAIDZ_DEFLATE) {
 		int i;
 
 		for (i = 0; i < rvd->vdev_children; i++) {
 			vd = rvd->vdev_child[i];
 			if (vd->vdev_deflate_ratio != SPA_MINBLOCKSIZE)
 				break;
 		}
 		if (i == rvd->vdev_children) {
 			spa->spa_deflate = TRUE;
 			VERIFY(0 == zap_add(spa->spa_meta_objset,
 			    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
 			    sizeof (uint64_t), 1, &spa->spa_deflate, tx));
 		}
 	}
 
 	/*
 	 * If anything has changed in this txg, or if someone is waiting
 	 * for this txg to sync (eg, spa_vdev_remove()), push the
 	 * deferred frees from the previous txg.  If not, leave them
 	 * alone so that we don't generate work on an otherwise idle
 	 * system.
 	 */
 	if (!txg_list_empty(&dp->dp_dirty_datasets, txg) ||
 	    !txg_list_empty(&dp->dp_dirty_dirs, txg) ||
 	    !txg_list_empty(&dp->dp_sync_tasks, txg) ||
 	    ((dsl_scan_active(dp->dp_scan) ||
 	    txg_sync_waiting(dp)) && !spa_shutting_down(spa))) {
 		zio_t *zio = zio_root(spa, NULL, NULL, 0);
 		VERIFY3U(bpobj_iterate(defer_bpo,
 		    spa_free_sync_cb, zio, tx), ==, 0);
 		VERIFY3U(zio_wait(zio), ==, 0);
 	}
 
 	/*
 	 * Iterate to convergence.
 	 */
 	do {
 		int pass = ++spa->spa_sync_pass;
 
 		spa_sync_config_object(spa, tx);
 		spa_sync_aux_dev(spa, &spa->spa_spares, tx,
 		    ZPOOL_CONFIG_SPARES, DMU_POOL_SPARES);
 		spa_sync_aux_dev(spa, &spa->spa_l2cache, tx,
 		    ZPOOL_CONFIG_L2CACHE, DMU_POOL_L2CACHE);
 		spa_errlog_sync(spa, txg);
 		dsl_pool_sync(dp, txg);
 
 		if (pass <= SYNC_PASS_DEFERRED_FREE) {
 			zio_t *zio = zio_root(spa, NULL, NULL, 0);
 			bplist_iterate(free_bpl, spa_free_sync_cb,
 			    zio, tx);
 			VERIFY(zio_wait(zio) == 0);
 		} else {
 			bplist_iterate(free_bpl, bpobj_enqueue_cb,
 			    defer_bpo, tx);
 		}
 
 		ddt_sync(spa, txg);
 		dsl_scan_sync(dp, tx);
 
 		while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, txg)))
 			vdev_sync(vd, txg);
 
 		if (pass == 1)
 			spa_sync_upgrades(spa, tx);
 
 	} while (dmu_objset_is_dirty(mos, txg));
 
 	/*
 	 * Rewrite the vdev configuration (which includes the uberblock)
 	 * to commit the transaction group.
 	 *
 	 * If there are no dirty vdevs, we sync the uberblock to a few
 	 * random top-level vdevs that are known to be visible in the
 	 * config cache (see spa_vdev_add() for a complete description).
 	 * If there *are* dirty vdevs, sync the uberblock to all vdevs.
 	 */
 	for (;;) {
 		/*
 		 * We hold SCL_STATE to prevent vdev open/close/etc.
 		 * while we're attempting to write the vdev labels.
 		 */
 		spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
 
 		if (list_is_empty(&spa->spa_config_dirty_list)) {
 			vdev_t *svd[SPA_DVAS_PER_BP];
 			int svdcount = 0;
 			int children = rvd->vdev_children;
 			int c0 = spa_get_random(children);
 
 			for (c = 0; c < children; c++) {
 				vd = rvd->vdev_child[(c0 + c) % children];
 				if (vd->vdev_ms_array == 0 || vd->vdev_islog)
 					continue;
 				svd[svdcount++] = vd;
 				if (svdcount == SPA_DVAS_PER_BP)
 					break;
 			}
 			error = vdev_config_sync(svd, svdcount, txg, B_FALSE);
 			if (error != 0)
 				error = vdev_config_sync(svd, svdcount, txg,
 				    B_TRUE);
 		} else {
 			error = vdev_config_sync(rvd->vdev_child,
 			    rvd->vdev_children, txg, B_FALSE);
 			if (error != 0)
 				error = vdev_config_sync(rvd->vdev_child,
 				    rvd->vdev_children, txg, B_TRUE);
 		}
 
 		spa_config_exit(spa, SCL_STATE, FTAG);
 
 		if (error == 0)
 			break;
 		zio_suspend(spa, NULL);
 		zio_resume_wait(spa);
 	}
 	dmu_tx_commit(tx);
 
 	/*
 	 * Clear the dirty config list.
 	 */
 	while ((vd = list_head(&spa->spa_config_dirty_list)) != NULL)
 		vdev_config_clean(vd);
 
 	/*
 	 * Now that the new config has synced transactionally,
 	 * let it become visible to the config cache.
 	 */
 	if (spa->spa_config_syncing != NULL) {
 		spa_config_set(spa, spa->spa_config_syncing);
 		spa->spa_config_txg = txg;
 		spa->spa_config_syncing = NULL;
 	}
 
 	spa->spa_ubsync = spa->spa_uberblock;
 
 	dsl_pool_sync_done(dp, txg);
 
 	/*
 	 * Update usable space statistics.
 	 */
 	while ((vd = txg_list_remove(&spa->spa_vdev_txg_list, TXG_CLEAN(txg))))
 		vdev_sync_done(vd, txg);
 
 	spa_update_dspace(spa);
 
 	/*
 	 * It had better be the case that we didn't dirty anything
 	 * since vdev_config_sync().
 	 */
 	ASSERT(txg_list_empty(&dp->dp_dirty_datasets, txg));
 	ASSERT(txg_list_empty(&dp->dp_dirty_dirs, txg));
 	ASSERT(txg_list_empty(&spa->spa_vdev_txg_list, txg));
 
 	spa->spa_sync_pass = 0;
 
 	spa_config_exit(spa, SCL_CONFIG, FTAG);
 
 	spa_handle_ignored_writes(spa);
 
 	/*
 	 * If any async tasks have been requested, kick them off.
 	 */
 	spa_async_dispatch(spa);
 }
 
 /*
  * Sync all pools.  We don't want to hold the namespace lock across these
  * operations, so we take a reference on the spa_t and drop the lock during the
  * sync.
  */
 void
 spa_sync_allpools(void)
 {
 	spa_t *spa = NULL;
 	mutex_enter(&spa_namespace_lock);
 	while ((spa = spa_next(spa)) != NULL) {
 		if (spa_state(spa) != POOL_STATE_ACTIVE ||
 		    !spa_writeable(spa) || spa_suspended(spa))
 			continue;
 		spa_open_ref(spa, FTAG);
 		mutex_exit(&spa_namespace_lock);
 		txg_wait_synced(spa_get_dsl(spa), 0);
 		mutex_enter(&spa_namespace_lock);
 		spa_close(spa, FTAG);
 	}
 	mutex_exit(&spa_namespace_lock);
 }
 
 /*
  * ==========================================================================
  * Miscellaneous routines
  * ==========================================================================
  */
 
 /*
  * Remove all pools in the system.
  */
 void
 spa_evict_all(void)
 {
 	spa_t *spa;
 
 	/*
 	 * Remove all cached state.  All pools should be closed now,
 	 * so every spa in the AVL tree should be unreferenced.
 	 */
 	mutex_enter(&spa_namespace_lock);
 	while ((spa = spa_next(NULL)) != NULL) {
 		/*
 		 * Stop async tasks.  The async thread may need to detach
 		 * a device that's been replaced, which requires grabbing
 		 * spa_namespace_lock, so we must drop it here.
 		 */
 		spa_open_ref(spa, FTAG);
 		mutex_exit(&spa_namespace_lock);
 		spa_async_suspend(spa);
 		mutex_enter(&spa_namespace_lock);
 		spa_close(spa, FTAG);
 
 		if (spa->spa_state != POOL_STATE_UNINITIALIZED) {
 			spa_unload(spa);
 			spa_deactivate(spa);
 		}
 		spa_remove(spa);
 	}
 	mutex_exit(&spa_namespace_lock);
 }
 
 vdev_t *
 spa_lookup_by_guid(spa_t *spa, uint64_t guid, boolean_t aux)
 {
 	vdev_t *vd;
 	int i;
 
 	if ((vd = vdev_lookup_by_guid(spa->spa_root_vdev, guid)) != NULL)
 		return (vd);
 
 	if (aux) {
 		for (i = 0; i < spa->spa_l2cache.sav_count; i++) {
 			vd = spa->spa_l2cache.sav_vdevs[i];
 			if (vd->vdev_guid == guid)
 				return (vd);
 		}
 
 		for (i = 0; i < spa->spa_spares.sav_count; i++) {
 			vd = spa->spa_spares.sav_vdevs[i];
 			if (vd->vdev_guid == guid)
 				return (vd);
 		}
 	}
 
 	return (NULL);
 }
 
 void
 spa_upgrade(spa_t *spa, uint64_t version)
 {
 	ASSERT(spa_writeable(spa));
 
 	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
 
 	/*
 	 * This should only be called for a non-faulted pool, and since a
 	 * future version would result in an unopenable pool, this shouldn't be
 	 * possible.
 	 */
 	ASSERT(spa->spa_uberblock.ub_version <= SPA_VERSION);
 	ASSERT(version >= spa->spa_uberblock.ub_version);
 
 	spa->spa_uberblock.ub_version = version;
 	vdev_config_dirty(spa->spa_root_vdev);
 
 	spa_config_exit(spa, SCL_ALL, FTAG);
 
 	txg_wait_synced(spa_get_dsl(spa), 0);
 }
 
 boolean_t
 spa_has_spare(spa_t *spa, uint64_t guid)
 {
 	int i;
 	uint64_t spareguid;
 	spa_aux_vdev_t *sav = &spa->spa_spares;
 
 	for (i = 0; i < sav->sav_count; i++)
 		if (sav->sav_vdevs[i]->vdev_guid == guid)
 			return (B_TRUE);
 
 	for (i = 0; i < sav->sav_npending; i++) {
 		if (nvlist_lookup_uint64(sav->sav_pending[i], ZPOOL_CONFIG_GUID,
 		    &spareguid) == 0 && spareguid == guid)
 			return (B_TRUE);
 	}
 
 	return (B_FALSE);
 }
 
 /*
  * Check if a pool has an active shared spare device.
  * Note: reference count of an active spare is 2, as a spare and as a replace
  */
 static boolean_t
 spa_has_active_shared_spare(spa_t *spa)
 {
 	int i, refcnt;
 	uint64_t pool;
 	spa_aux_vdev_t *sav = &spa->spa_spares;
 
 	for (i = 0; i < sav->sav_count; i++) {
 		if (spa_spare_exists(sav->sav_vdevs[i]->vdev_guid, &pool,
 		    &refcnt) && pool != 0ULL && pool == spa_guid(spa) &&
 		    refcnt > 2)
 			return (B_TRUE);
 	}
 
 	return (B_FALSE);
 }
 
 /*
  * Post a FM_EREPORT_ZFS_* event from sys/fm/fs/zfs.h.  The payload will be
  * filled in from the spa and (optionally) the vdev.  This doesn't do anything
  * in the userland libzpool, as we don't want consumers to misinterpret ztest
  * or zdb as real changes.
  */
 void
 spa_event_notify(spa_t *spa, vdev_t *vd, const char *name)
 {
 #ifdef _KERNEL
 	zfs_ereport_post(name, spa, vd, NULL, 0, 0);
 #endif
 }
 
 #if defined(_KERNEL) && defined(HAVE_SPL)
 /* state manipulation functions */
 EXPORT_SYMBOL(spa_open);
 EXPORT_SYMBOL(spa_open_rewind);
 EXPORT_SYMBOL(spa_get_stats);
 EXPORT_SYMBOL(spa_create);
 EXPORT_SYMBOL(spa_import_rootpool);
 EXPORT_SYMBOL(spa_import);
 EXPORT_SYMBOL(spa_tryimport);
 EXPORT_SYMBOL(spa_destroy);
 EXPORT_SYMBOL(spa_export);
 EXPORT_SYMBOL(spa_reset);
 EXPORT_SYMBOL(spa_async_request);
 EXPORT_SYMBOL(spa_async_suspend);
 EXPORT_SYMBOL(spa_async_resume);
 EXPORT_SYMBOL(spa_inject_addref);
 EXPORT_SYMBOL(spa_inject_delref);
 EXPORT_SYMBOL(spa_scan_stat_init);
 EXPORT_SYMBOL(spa_scan_get_stats);
 
 /* device maniion */
 EXPORT_SYMBOL(spa_vdev_add);
 EXPORT_SYMBOL(spa_vdev_attach);
 EXPORT_SYMBOL(spa_vdev_detach);
 EXPORT_SYMBOL(spa_vdev_remove);
 EXPORT_SYMBOL(spa_vdev_setpath);
 EXPORT_SYMBOL(spa_vdev_setfru);
 EXPORT_SYMBOL(spa_vdev_split_mirror);
 
 /* spare statech is global across all pools) */
 EXPORT_SYMBOL(spa_spare_add);
 EXPORT_SYMBOL(spa_spare_remove);
 EXPORT_SYMBOL(spa_spare_exists);
 EXPORT_SYMBOL(spa_spare_activate);
 
 /* L2ARC statech is global across all pools) */
 EXPORT_SYMBOL(spa_l2cache_add);
 EXPORT_SYMBOL(spa_l2cache_remove);
 EXPORT_SYMBOL(spa_l2cache_exists);
 EXPORT_SYMBOL(spa_l2cache_activate);
 EXPORT_SYMBOL(spa_l2cache_drop);
 
 /* scanning */
 EXPORT_SYMBOL(spa_scan);
 EXPORT_SYMBOL(spa_scan_stop);
 
 /* spa syncing */
 EXPORT_SYMBOL(spa_sync); /* only for DMU use */
 EXPORT_SYMBOL(spa_sync_allpools);
 
 /* properties */
 EXPORT_SYMBOL(spa_prop_set);
 EXPORT_SYMBOL(spa_prop_get);
 EXPORT_SYMBOL(spa_prop_clear_bootfs);
 
 /* asynchronous event notification */
 EXPORT_SYMBOL(spa_event_notify);
 #endif