text: /*
   * 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 2010 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
  /*
   * 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/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>
  #include <sys/trim_map.h>
  #include <syslog.h>
  
  #ifdef	_KERNEL
  #include <sys/zone.h>
  #endif	/* _KERNEL */
  
  #include "zfs_prop.h"
  #include "zfs_comutil.h"
  
  enum zti_modes {
  	zti_mode_fixed,			/* value is # of threads (min 1) */
  	zti_mode_online_percent,	/* value is % of online CPUs */
  	zti_mode_tune,			/* fill from zio_taskq_tune_* */
  	zti_mode_null,			/* don't create a taskq */
  	zti_nmodes
  };
  
  #define	ZTI_FIX(n)	{ zti_mode_fixed, (n) }
  #define	ZTI_PCT(n)	{ zti_mode_online_percent, (n) }
  #define	ZTI_TUNE	{ zti_mode_tune, 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] = {
  		"issue", "issue_high", "intr", "intr_high"
  };
  
  /*
   * 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_TUNE,	ZTI_NULL },
  	{ ZTI_TUNE,	ZTI_FIX(5),	ZTI_FIX(8),	ZTI_FIX(5) },
  	{ ZTI_FIX(10),	ZTI_NULL,	ZTI_FIX(10),	ZTI_NULL },
  	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL },
  	{ ZTI_ONE,	ZTI_NULL,	ZTI_ONE,	ZTI_NULL },
  };
  
  enum zti_modes zio_taskq_tune_mode = zti_mode_online_percent;
  uint_t zio_taskq_tune_value = 80;	/* #threads = 80% of # online CPUs */
  
  static dsl_syncfunc_t spa_sync_props;
  static boolean_t spa_has_active_shared_spare(spa_t *spa);
  static 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);
  
  /*
   * ==========================================================================
   * 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_SLEEP) == 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)
  {
  	uint64_t size;
  	uint64_t alloc;
  	uint64_t cap, version;
  	zprop_source_t src = ZPROP_SRC_NONE;
  	spa_config_dirent_t *dp;
  
  	ASSERT(MUTEX_HELD(&spa->spa_props_lock));
  
  	if (spa->spa_root_vdev != 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);
  
  		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,
  		    spa->spa_root_vdev->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_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;
  
  	VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
  
  	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);
  		return (0);
  	}
  
  	/*
  	 * 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_SLEEP);
  				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_SLEEP);
  			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;
  
  	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;
  
  		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_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;
  		}
  
  		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_SLEEP);
  
  	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)
  			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;
  	}
  }
  
  /*
   * ==========================================================================
   * 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));
  }
  
  /*
   * Activate an uninitialized pool.
   */
  static void
  spa_activate(spa_t *spa, int mode)
  {
  	int error;
  	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);
  
  	/* Initialize async I/O context and thread */
  #ifdef LINUX_AIO
  	error = zio_aio_init(spa);
  	if (error)
  		cmn_err(CE_WARN, "error '%i' enabling async I/O for pool '%s'",
  		    error, spa->spa_name);
  #endif
  
  	for (int t = 0; t < ZIO_TYPES; t++) {
  		for (int 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]);
  
  			if (mode == zti_mode_tune) {
  				mode = zio_taskq_tune_mode;
  				value = zio_taskq_tune_value;
  				if (mode == zti_mode_tune)
  					mode = zti_mode_online_percent;
  			}
  
  			switch (mode) {
  			case zti_mode_fixed:
  				ASSERT3U(value, >=, 1);
  				value = MAX(value, 1);
  
  				spa->spa_zio_taskq[t][q] = taskq_create(name,
  				    value, maxclsyspri, 50, INT_MAX,
  				    TASKQ_PREPOPULATE);
  				break;
  
  			case zti_mode_online_percent:
  				spa->spa_zio_taskq[t][q] = taskq_create(name,
  				    value, maxclsyspri, 50, INT_MAX,
  				    TASKQ_PREPOPULATE | TASKQ_THREADS_CPU_PCT);
  				break;
  
  			case zti_mode_null:
  				spa->spa_zio_taskq[t][q] = NULL;
  				break;
  
  			case zti_mode_tune:
  			default:
  				panic("unrecognized mode for "
  				    "zio_taskqs[%u]->zti_nthreads[%u] (%u:%u) "
  				    "in spa_activate()",
  				    t, q, mode, value);
  				break;
  			}
  		}
  	}
  
  	/*
  	 * Start TRIM thread.
  	 */
  	trim_thread_create(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)
  {
  	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);
  
  	/*
  	 * Stop TRIM thread in case spa_unload() wasn't called directly
  	 * before spa_deactivate().
  	 */
  	trim_thread_destroy(spa);
  
  	txg_list_destroy(&spa->spa_vdev_txg_list);
  
  	list_destroy(&spa->spa_config_dirty_list);
  	list_destroy(&spa->spa_state_dirty_list);
  
  	for (int t = 0; t < ZIO_TYPES; t++) {
  		for (int 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;
  		}
  	}
  
  #ifdef LINUX_AIO
  	zio_aio_fini(spa);
  #endif
  
  	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;
  }
  
  /*
   * 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;
  
  	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 (int 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 TRIM thread.
  	 */
  	trim_thread_destroy(spa);
  
  	/*
  	 * 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) {
  		for (i = 0; i < max_ncpus; i++)
  			(void) zio_wait(spa->spa_async_zio_root[i]);
  		kmem_free(spa->spa_async_zio_root, max_ncpus * sizeof (void *));
  		spa->spa_async_zio_root = NULL;
  	}
  
  	/*
  	 * 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_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;
  
  	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_SLEEP);
  	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_SLEEP);
  	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;
  	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_SLEEP);
  	} 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) {
  			if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
  			    pool != 0ULL && l2arc_vdev_present(vd))
  				l2arc_remove_vdev(vd);
  			(void) vdev_close(vd);
  			spa_l2cache_remove(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_SLEEP);
  	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));
  	nvsize = *(uint64_t *)db->db_data;
  	dmu_buf_rele(db, FTAG);
  
  	packed = kmem_alloc(nvsize, KM_SLEEP);
  	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)
  {
  	for (int 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_post_autoreplace(vd->vdev_spa, vd);
  		spa_event_notify(vd->vdev_spa, vd, ESC_ZFS_VDEV_CHECK);
  	}
  }
  
  /*
   * Load the slog device state from the config object since it's possible
   * that the label does not contain the most up-to-date information.
   */
  void
  spa_load_log_state(spa_t *spa, nvlist_t *nv)
  {
  	vdev_t *ovd, *rvd = spa->spa_root_vdev;
  
  	/*
  	 * Load the original root vdev tree from the passed config.
  	 */
  	spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
  	VERIFY(spa_config_parse(spa, &ovd, nv, NULL, 0, VDEV_ALLOC_LOAD) == 0);
  
  	for (int c = 0; c < rvd->vdev_children; c++) {
  		vdev_t *cvd = rvd->vdev_child[c];
  		if (cvd->vdev_islog)
  			vdev_load_log_state(cvd, ovd->vdev_child[c]);
  	}
  	vdev_free(ovd);
  	spa_config_exit(spa, SCL_ALL, FTAG);
  }
  
  /*
   * Check for missing log devices
   */
  int
  spa_check_logs(spa_t *spa)
  {
  	switch (spa->spa_log_state) {
  	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;
  
  	ASSERT(spa_config_held(spa, SCL_ALLOC, RW_WRITER));
  
  	if (!spa_has_slogs(spa))
  		return (B_FALSE);
  
  	for (int 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;
  
  	ASSERT(spa_config_held(spa, SCL_ALLOC, RW_WRITER));
  
  	for (int 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)
  {
  	for (int 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) {
  		verify_ok = B_TRUE;
  		spa->spa_load_txg = spa->spa_uberblock.ub_txg;
  		spa->spa_load_txg_ts = spa->spa_uberblock.ub_timestamp;
  	} 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_SLEEP);
  
  	/* 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;
  	int error;
  	uint64_t pool_guid;
  	nvlist_t *nvl;
  
  	if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID, &pool_guid))
  		return (EINVAL);
  
  	/*
  	 * 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_load_guid = pool_guid;
  
  		if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_SPLIT,
  		    &nvl) == 0) {
  			VERIFY(nvlist_dup(nvl, &spa->spa_config_splitting,
  			    KM_SLEEP) == 0);
  		}
  
  		error = spa_load_impl(spa, pool_guid, config, state, type,
  		    mosconfig, &ereport);
  	}
  
  	spa->spa_minref = refcount_count(&spa->spa_refcount);
  	if (error && 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.
   */
  static 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 config_cache_txg = spa->spa_config_txg;
  	int orig_mode = spa->spa_mode;
  	int parse, i;
  
  	/*
  	 * 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 = kmem_alloc(max_ncpus * sizeof (void *),
  	    KM_SLEEP);
  	for (i = 0; i < max_ncpus; i++) {
  		spa->spa_async_zio_root[i] = 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);
  		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.
  	 */
  	if (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);
  
  
  //			myhostid = zone_get_hostid(NULL);
  
  			/*
  			 * 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);
  
  			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://www.sun.com/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_BPLIST,
  	    &spa->spa_deferred_bplist_obj) != 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);
  
  	/*
  	 * 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);
  
  	/*
  	 * 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);
  
  	if (state != SPA_LOAD_TRYIMPORT) {
  		error = spa_load_verify(spa);
  		if (error)
  			return (spa_vdev_err(rvd, VDEV_AUX_CORRUPT_DATA,
  			    error));
  	}
  
  	/*
  	 * Load the intent log state and check log integrity.  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));
  
  		VERIFY(nvlist_lookup_nvlist(nvconfig, ZPOOL_CONFIG_VDEV_TREE,
  		    &nvroot) == 0);
  		spa_load_log_state(spa, nvroot);
  		nvlist_free(nvconfig);
  
  		if (spa_check_logs(spa)) {
  			*ereport = FM_EREPORT_ZFS_LOG_REPLAY;
  			return (spa_vdev_err(rvd, VDEV_AUX_BAD_LOG, ENXIO));
  		}
  	}
  
  	if (spa_writeable(spa) && (state == SPA_LOAD_RECOVER ||
  	    spa->spa_load_max_txg == UINT64_MAX)) {
  		dmu_tx_t *tx;
  		int need_update = B_FALSE;
  
  		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 spa_load_verbatim is true, trust the current
  		 * in-core spa_config and update the disk labels.
  		 */
  		if (config_cache_txg != spa->spa_config_txg ||
  		    state == SPA_LOAD_IMPORT || spa->spa_load_verbatim ||
  		    state == SPA_LOAD_RECOVER)
  			need_update = B_TRUE;
  
  		for (int 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)
  {
  	spa_unload(spa);
  	spa_deactivate(spa);
  
  	spa->spa_load_max_txg--;
  
  	spa_activate(spa, spa_mode_global);
  	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
  	 */
  	// Don't try to recover from ENOENT errors !
  	while (rewind_error && rewind_error != ENOENT &&
  		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);
  	}
  
  	if (config)
  		spa_rewind_data_to_nvlist(spa, config);
  
  	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;
  	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) {
  		spa_load_state_t state = SPA_LOAD_OPEN;
  		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 (spa->spa_last_open_failed && (policy.zrp_request &
  		    (ZPOOL_NO_REWIND | ZPOOL_NEVER_REWIND))) {
  			if (config != NULL && spa->spa_config)
  				VERIFY(nvlist_dup(spa->spa_config,
  				    config, KM_SLEEP) == 0);
  			spa_deactivate(spa);
  			if (locked)
  				mutex_exit(&spa_namespace_lock);
  			return (spa->spa_last_open_failed);
  		}
  
  		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_SLEEP) == 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 (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) {
  			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;
  			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_SLEEP);
  		for (i = 0; i < oldndevs; i++)
  			VERIFY(nvlist_dup(olddevs[i], &newdevs[i],
  			    KM_SLEEP) == 0);
  		for (i = 0; i < ndevs; i++)
  			VERIFY(nvlist_dup(devs[i], &newdevs[i + oldndevs],
  			    KM_SLEEP) == 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_SLEEP) == 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);
  		if (vd->vdev_isl2cache)
  			spa_l2cache_remove(vd);
  		vdev_clear_stats(vd);
  		(void) vdev_close(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;
  	int i;
  
  	/*
  	 * 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 = kmem_alloc(max_ncpus * sizeof (void *),
  	    KM_SLEEP);
  	for (i = 0; i < max_ncpus; i++) {
  		spa->spa_async_zio_root[i] = 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 (int 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_SLEEP) == 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_SLEEP) == 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 bplist object.  Turn off compression
  	 * because sync-to-convergence takes longer if the blocksize
  	 * keeps changing.
  	 */
  	spa->spa_deferred_bplist_obj = bplist_create(spa->spa_meta_objset,
  	    1 << 14, tx);
  	dmu_object_set_compress(spa->spa_meta_objset,
  	    spa->spa_deferred_bplist_obj, ZIO_COMPRESS_OFF, tx);
  
  	if (zap_add(spa->spa_meta_objset,
  	    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_SYNC_BPLIST,
  	    sizeof (uint64_t), 1, &spa->spa_deferred_bplist_obj, tx) != 0) {
  		cmn_err(CE_PANIC, "failed to add bplist");
  	}
  
  	/*
  	 * 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);
  }
  
  /* ZFSFUSE: not needed */
  #if 0
  /*
   * 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_SLEEP) == 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)
  {
  	for (int 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.
  	 */
  	if ((config = spa_generate_rootconf(devpath, devid, &guid)) == 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_load_verbatim = B_TRUE;
  
  	/*
  	 * 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[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
  
  /*
   * Take a pool and insert it into the namespace as if it had been loaded at
   * boot.
   */
  int
  spa_import_verbatim(const char *pool, nvlist_t *config, nvlist_t *props)
  {
  	spa_t *spa;
  	char *altroot = NULL;
  
  	mutex_enter(&spa_namespace_lock);
  	if (spa_lookup(pool) != NULL) {
  		mutex_exit(&spa_namespace_lock);
  		return (EEXIST);
  	}
  
  	(void) nvlist_lookup_string(props,
  	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
  	spa = spa_add(pool, config, altroot);
  
  	spa->spa_load_verbatim = B_TRUE;
  
  	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);
  }
  
  /*
   * Import a non-root pool into the system.
   */
  int
  spa_import(const char *pool, nvlist_t *config, nvlist_t *props)
  {
  	spa_t *spa;
  	char *altroot = NULL;
  	spa_load_state_t state = SPA_LOAD_IMPORT;
  	zpool_rewind_policy_t policy;
  	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);
  	}
  
  	zpool_get_rewind_policy(config, &policy);
  	if (policy.zrp_request & ZPOOL_DO_REWIND)
  		state = SPA_LOAD_RECOVER;
  
  	/*
  	 * Create and initialize the spa structure.
  	 */
  	(void) nvlist_lookup_string(props,
  	    zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
  	spa = spa_add(pool, config, altroot);
  	spa_activate(spa, spa_mode_global);
  
  	/*
  	 * Don't start async tasks until we know everything is healthy.
  	 */
  	spa_async_suspend(spa);
  
  	/*
  	 * 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 about failing or best txgs
  	 * back to caller
  	 */
  	spa_rewind_data_to_nvlist(spa, config);
  
  	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);
  	}
  
  	/*
  	 * 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_SLEEP) == 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_SLEEP) == 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);
  	}
  
  	spa_async_resume(spa);
  
  	/*
  	 * 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);
  }
  
  
  /*
   * 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"
  
  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_SLEEP);
  
  			/*
  			 * 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_SLEEP);
  
  				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, ESC_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;
  
  	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 (int 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;
  	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;
  
  	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_ADD)) != 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 &&
  		    pvd->vdev_child[1] == oldvd &&
  		    !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)
  			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));
  		else if (pvd->vdev_ops != &vdev_spare_ops &&
  		    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_SLEEP);
  		(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;
  		}
  	}
  
  	/*
  	 * 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, ESC_ZFS_VDEV_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);
  
  	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;
  	vdev_t *rvd = spa->spa_root_vdev;
  	vdev_t *vd, *pvd, *cvd, *tvd;
  	boolean_t unspare = B_FALSE;
  	uint64_t unspare_guid;
  	size_t len;
  	char *vdpath;
  
  	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));
  
  	/*
  	 * If replace_done is specified, only remove this device if it's
  	 * the first child of a replacing vdev.  For the 'spare' vdev, either
  	 * disk can be removed.
  	 */
  	if (replace_done) {
  		if (pvd->vdev_ops == &vdev_replacing_ops) {
  			if (vd->vdev_id != 0)
  				return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));
  		} else if (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 == 1 &&
  	    pvd->vdev_child[0]->vdev_path != NULL &&
  	    pvd->vdev_child[1]->vdev_path != NULL) {
  		ASSERT(pvd->vdev_child[1] == vd);
  		cvd = pvd->vdev_child[0];
  		len = strlen(vd->vdev_path);
  		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);
  		}
  	}
  
  	/*
  	 * 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[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[0];
  
  	/*
  	 * 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);
  	}
  
  	/*
  	 * 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)
  		vdev_remove_parent(cvd);
  
  	/*
  	 * 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 (int 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, ESC_ZFS_VDEV_REMOVE);
  
  	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 *myspa = spa;
  		spa = NULL;
  		mutex_enter(&spa_namespace_lock);
  		while ((spa = spa_next(spa)) != NULL) {
  			if (spa->spa_state != POOL_STATE_ACTIVE)
  				continue;
  			if (spa == myspa)
  				continue;
  			spa_open_ref(spa, FTAG);
  			mutex_exit(&spa_namespace_lock);
  			(void) spa_vdev_remove(spa, unspare_guid,
  			    B_TRUE);
  			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;
  
  	if (!spa_writeable(spa))
  		return (EROFS);
  
  	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_SLEEP);
  	glist = kmem_zalloc(children * sizeof (uint64_t), KM_SLEEP);
  
  	/* 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_SLEEP) == 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_SLEEP) == 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)
  {
  	for (int 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;
  
  	if (count > 1)
  		newdev = kmem_alloc((count - 1) * sizeof (void *), KM_SLEEP);
  
  	for (int i = 0, j = 0; i < count; i++) {
  		if (dev[i] == dev_to_remove)
  			continue;
  		VERIFY(nvlist_dup(dev[i], &newdev[j++], KM_SLEEP) == 0);
  	}
  
  	VERIFY(nvlist_remove(config, name, DATA_TYPE_NVLIST_ARRAY) == 0);
  	VERIFY(nvlist_add_nvlist_array(config, name, newdev, count - 1) == 0);
  
  	for (int 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);
  	}
  }
  
  /*
   * 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);
  
  	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;
  
  	for (int 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.
  	 */
  	if (vd->vdev_ops == &vdev_replacing_ops && vd->vdev_children == 2) {
  		oldvd = vd->vdev_child[0];
  		newvd = vd->vdev_child[1];
  
  		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 && vd->vdev_children == 2) {
  		newvd = vd->vdev_child[0];
  		oldvd = vd->vdev_child[1];
  
  		if (newvd->vdev_unspare &&
  		    vdev_dtl_empty(newvd, DTL_MISSING) &&
  		    vdev_dtl_empty(newvd, DTL_OUTAGE) &&
  		    !vdev_dtl_required(oldvd)) {
  			newvd->vdev_unspare = 0;
  			return (oldvd);
  		}
  	}
  
  	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) {
  			ASSERT(pvd->vdev_ops == &vdev_replacing_ops);
  			ASSERT(ppvd->vdev_children == 2);
  			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;
  
  	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)
  {
  	if (vd->vdev_remove_wanted) {
  		vd->vdev_remove_wanted = 0;
  		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 (int 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)
  {
  	if (vd->vdev_probe_wanted) {
  		vd->vdev_probe_wanted = 0;
  		vdev_reopen(vd);	/* vdev_open() does the actual probe */
  	}
  
  	for (int 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)
  {
  	// sysevent_id_t eid;
  	nvlist_t *attr;
  	char *physpath;
  
  	if (!spa->spa_autoexpand)
  		return;
  
  	for (int 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;
  
  	physpath = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
  	(void) snprintf(physpath, MAXPATHLEN, "/devices%s", vd->vdev_physpath);
  	syslog(LOG_WARNING,"spa_async_autoexpand: would have used %s",physpath);
  
  	/* zfs-fuse : DEV_PHYS_PATH is defined in sysevent/dev.h, and there is no
  	 * sysevent in linux... so nothing for now !
  	VERIFY(nvlist_alloc(&attr, NV_UNIQUE_NAME, KM_SLEEP) == 0);
  	VERIFY(nvlist_add_string(attr, DEV_PHYS_PATH, physpath) == 0);
  
  	(void) ddi_log_sysevent(zfs_dip, SUNW_VENDOR, EC_DEV_STATUS,
  	    ESC_DEV_DLE, attr, &eid, DDI_SLEEP);
  
  	nvlist_free(attr);
  	*/
  	kmem_free(physpath, MAXPATHLEN);
  }
  
  static void
  spa_async_thread(spa_t *spa)
  {
  	int tasks;
  
  	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 (int i = 0; i < spa->spa_l2cache.sav_count; i++)
  			spa_async_remove(spa, spa->spa_l2cache.sav_vdevs[i]);
  		for (int 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 void
  spa_sync_deferred_bplist(spa_t *spa, bplist_t *bpl, dmu_tx_t *tx, uint64_t txg)
  {
  	blkptr_t blk;
  	uint64_t itor = 0;
  	uint8_t c = 1;
  
  	while (bplist_iterate(bpl, &itor, &blk) == 0) {
  		ASSERT(blk.blk_birth < txg);
  		zio_free(spa, txg, &blk);
  	}
  
  	bplist_vacate(bpl, tx);
  
  	/*
  	 * Pre-dirty the first block so we sync to convergence faster.
  	 * (Usually only the first block is needed.)
  	 */
  	dmu_write(bpl->bpl_mos, spa->spa_deferred_bplist_obj, 0, 1, &c, tx);
  }
  
  static void
  spa_sync_free(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,
  	    BP_GET_PSIZE(bp), zio->io_flags));
  }
  
  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 = kmem_alloc(bufsize, KM_SLEEP);
  
  	VERIFY(nvlist_pack(nv, &packed, &nvsize, NV_ENCODE_XDR,
  	    KM_SLEEP) == 0);
  	bzero(packed + nvsize, bufsize - nvsize);
  
  	dmu_write(spa->spa_meta_objset, obj, 0, bufsize, packed, tx);
  
  	kmem_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_SLEEP) == 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_SLEEP);
  		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_CACHEFILE:
  			/*
  			 * 'cachefile' is also a non-persisitent property.
  			 */
  			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;
  				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);
  }
  
  /*
   * 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;
  	bplist_t *defer_bpl = &spa->spa_deferred_bplist;
  	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;
  
  	/*
  	 * 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);
  
  	VERIFY(0 == bplist_open(defer_bpl, mos, spa->spa_deferred_bplist_obj));
  
  	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 (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 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) ||
  	    ((dp->dp_scan->scn_phys.scn_state == DSS_SCANNING ||
  	    txg_sync_waiting(dp)) && !spa_shutting_down(spa)))
  		spa_sync_deferred_bplist(spa, defer_bpl, tx, txg);
  
  	/*
  	 * 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_sync(free_bpl, spa_sync_free, zio, tx);
  			VERIFY(zio_wait(zio) == 0);
  		} else {
  			bplist_sync(free_bpl, bplist_enqueue_cb, defer_bpl, 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);
  
  	} while (dmu_objset_is_dirty(mos, txg));
  
  	ASSERT(list_is_empty(&free_bpl->bpl_queue));
  
  	bplist_close(defer_bpl);
  
  	/*
  	 * 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 (int 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);
  
  		/* On opensolaris in case of error here, the zio is suspended
  		 * and then it waits until it's told to resume its activity.
  		 * Except that here in zfs-fuse nothing will ever be able to
  		 * tell it to resume !
  		 * I have absolutely no idea for now how something can send
  		 * the ioctl to resume it (ZFS_IOC_CLEAR apparently) */
  		if (error == 0 || error == EIO)
  			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));
  	ASSERT(list_is_empty(&defer_bpl->bpl_queue));
  	ASSERT(list_is_empty(&free_bpl->bpl_queue));
  
  	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_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)
  {
  	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 sysevent corresponding to the given event.  The 'name' must be one of
   * the event definitions in sys/sysevent/eventdefs.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)
  {
  #if 0
  	sysevent_t		*ev;
  	sysevent_attr_list_t	*attr = NULL;
  	sysevent_value_t	value;
  	sysevent_id_t		eid;
  
  	ev = sysevent_alloc(EC_ZFS, (char *)name, SUNW_KERN_PUB "zfs",
  	    SE_SLEEP);
  
  	value.value_type = SE_DATA_TYPE_STRING;
  	value.value.sv_string = spa_name(spa);
  	if (sysevent_add_attr(&attr, ZFS_EV_POOL_NAME, &value, SE_SLEEP) != 0)
  		goto done;
  
  	value.value_type = SE_DATA_TYPE_UINT64;
  	value.value.sv_uint64 = spa_guid(spa);
  	if (sysevent_add_attr(&attr, ZFS_EV_POOL_GUID, &value, SE_SLEEP) != 0)
  		goto done;
  
  	if (vd) {
  		value.value_type = SE_DATA_TYPE_UINT64;
  		value.value.sv_uint64 = vd->vdev_guid;
  		if (sysevent_add_attr(&attr, ZFS_EV_VDEV_GUID, &value,
  		    SE_SLEEP) != 0)
  			goto done;
  
  		if (vd->vdev_path) {
  			value.value_type = SE_DATA_TYPE_STRING;
  			value.value.sv_string = vd->vdev_path;
  			if (sysevent_add_attr(&attr, ZFS_EV_VDEV_PATH,
  			    &value, SE_SLEEP) != 0)
  				goto done;
  		}
  	}
  
  	if (sysevent_attach_attributes(ev, attr) != 0)
  		goto done;
  	attr = NULL;
  
  	(void) log_sysevent(ev, SE_SLEEP, &eid);
  
  done:
  	if (attr)
  		sysevent_free_attr(attr);
  	sysevent_free(ev);
  #endif
  }
  