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spa.c

/*
 * 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 2009 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/zio_compress.h>
#include <sys/dmu.h>
#include <sys/dmu_tx.h>
#include <sys/zap.h>
#include <sys/zil.h>
#include <sys/vdev_impl.h>
#include <sys/metaslab.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/sunddi.h>
#include <sys/spa_boot.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_nmodes
};

#define     ZTI_THREAD_FIX(n) { zti_mode_fixed, (n) }
#define     ZTI_THREAD_PCT(n) { zti_mode_online_percent, (n) }
#define     ZTI_THREAD_TUNE         { zti_mode_tune, 0 }

#define     ZTI_THREAD_ONE          ZTI_THREAD_FIX(1)

typedef struct zio_taskq_info {
      const char *zti_name;
      struct {
            enum zti_modes zti_mode;
            uint_t zti_value;
      } zti_nthreads[ZIO_TASKQ_TYPES];
} zio_taskq_info_t;

static const char *const zio_taskq_types[ZIO_TASKQ_TYPES] = {
                        "issue",          "intr"
};

const zio_taskq_info_t zio_taskqs[ZIO_TYPES] = {
      /*                ISSUE             INTR        */
      { "spa_zio_null", { ZTI_THREAD_ONE, ZTI_THREAD_ONE } },
      { "spa_zio_read", { ZTI_THREAD_FIX(8),    ZTI_THREAD_TUNE } },
      { "spa_zio_write",      { ZTI_THREAD_TUNE,      ZTI_THREAD_FIX(8) } },
      { "spa_zio_free", { ZTI_THREAD_ONE, ZTI_THREAD_ONE } },
      { "spa_zio_claim",      { ZTI_THREAD_ONE, ZTI_THREAD_ONE } },
      { "spa_zio_ioctl",      { ZTI_THREAD_ONE, ZTI_THREAD_ONE } },
};

enum zti_modes zio_taskq_tune_mode = zti_mode_online_percent;
uint_t zio_taskq_tune_value = 80;   /* #threads = 80% of # online CPUs */

static void spa_sync_props(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx);
static boolean_t spa_has_active_shared_spare(spa_t *spa);

/*
 * ==========================================================================
 * 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 used;
      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) {
            size = spa_get_space(spa);
            used = spa_get_alloc(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_USED, NULL, used, src);
            spa_prop_add_list(*nvp, ZPOOL_PROP_AVAILABLE, NULL,
                size - used, src);

            cap = (size == 0) ? 0 : (used * 100 / size);
            spa_prop_add_list(*nvp, ZPOOL_PROP_CAPACITY, NULL, cap, 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)
{
      zap_cursor_t zc;
      zap_attribute_t za;
      objset_t *mos = spa->spa_meta_objset;
      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 (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:
                  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_open(strval, DMU_OST_ZFS,
                            DS_MODE_USER | DS_MODE_READONLY, &os))
                              break;

                        /* We don't support gzip bootable datasets */
                        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_close(os);
                  }
                  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;
            }

            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(zfs_metaslab_ops);
      spa->spa_log_class = metaslab_class_create(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++) {
            const zio_taskq_info_t *ztip = &zio_taskqs[t];
            for (int q = 0; q < ZIO_TASKQ_TYPES; q++) {
                  enum zti_modes mode = ztip->zti_nthreads[q].zti_mode;
                  uint_t value = ztip->zti_nthreads[q].zti_value;
                  char name[32];

                  (void) snprintf(name, sizeof (name),
                      "%s_%s", ztip->zti_name, 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_tune:
                  default:
                        panic("unrecognized mode for "
                            "zio_taskqs[%u]->zti_nthreads[%u] (%u:%u) "
                            "in spa_activate()",
                            t, q, mode, value);
                        break;
                  }
            }
      }

      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);

      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++) {
                  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 c, 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 (c = 0; c < children; c++) {
            vdev_t *vd;
            if ((error = spa_config_parse(spa, &vd, child[c], *vdp, c,
                atype)) != 0) {
                  vdev_free(*vdp);
                  *vdp = NULL;
                  return (error);
            }
      }

      ASSERT(*vdp != NULL);

      return (0);
}

/*
 * Opposite of spa_load().
 */
static void
spa_unload(spa_t *spa)
{
      int i;

      ASSERT(MUTEX_HELD(&spa_namespace_lock));

      /*
       * Stop async tasks.
       */
      spa_async_suspend(spa);

      /*
       * Stop syncing.
       */
      if (spa->spa_sync_on) {
            txg_sync_stop(spa->spa_dsl_pool);
            spa->spa_sync_on = B_FALSE;
      }

      /*
       * Wait for any outstanding async I/O to complete.
       */
      if (spa->spa_async_zio_root != NULL) {
            (void) zio_wait(spa->spa_async_zio_root);
            spa->spa_async_zio_root = NULL;
      }

      /*
       * Close the dsl pool.
       */
      if (spa->spa_dsl_pool) {
            dsl_pool_close(spa->spa_dsl_pool);
            spa->spa_dsl_pool = NULL;
      }

      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, B_TRUE, B_FALSE);
      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, size;
      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)) {
                        size = vdev_get_rsize(vd);
                        l2arc_add_vdev(spa, vd,
                            VDEV_LABEL_START_SIZE,
                            size - VDEV_LABEL_START_SIZE);
                  }
            }
      }

      /*
       * 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, B_FALSE, B_TRUE);
      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)
{
      int c;

      for (c = 0; c < vd->vdev_children; c++)
            spa_check_removed(vd->vdev_child[c]);

      if (vd->vdev_ops->vdev_op_leaf && vdev_is_dead(vd)) {
            zfs_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, *nvroot, **child;
      uint64_t is_log;
      uint_t children, c;
      vdev_t *rvd = spa->spa_root_vdev;

      VERIFY(load_nvlist(spa, spa->spa_config_object, &nv) == 0);
      VERIFY(nvlist_lookup_nvlist(nv, ZPOOL_CONFIG_VDEV_TREE, &nvroot) == 0);
      VERIFY(nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
          &child, &children) == 0);

      for (c = 0; c < children; c++) {
            vdev_t *tvd = rvd->vdev_child[c];

            if (nvlist_lookup_uint64(child[c], ZPOOL_CONFIG_IS_LOG,
                &is_log) == 0 && is_log)
                  vdev_load_log_state(tvd, child[c]);
      }
      nvlist_free(nv);
}

/*
 * 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->spa_log_state = SPA_LOG_MISSING;
                  return (1);
            }
            break;
      }
      return (0);
}

/*
 * Load an existing storage pool, using the pool's builtin spa_config as a
 * source of configuration information.
 */
static int
spa_load(spa_t *spa, nvlist_t *config, spa_load_state_t state, int mosconfig)
{
      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;
      uint64_t pool_guid;
      uint64_t version;
      uint64_t autoreplace = 0;
      int orig_mode = spa->spa_mode;
      char *ereport = FM_EREPORT_ZFS_POOL;

      /*
       * 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) ||
          nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID, &pool_guid)) {
            error = EINVAL;
            goto out;
      }

      /*
       * 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, &version) != 0)
            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;
            goto out;
      }

      spa->spa_load_guid = pool_guid;

      /*
       * Create "The Godfather" zio to hold all async IOs
       */
      spa->spa_async_zio_root = zio_root(spa, NULL, NULL,
          ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_GODFATHER);

      /*
       * Parse the configuration into a vdev tree.  We explicitly set the
       * value that will be returned by spa_version() since parsing the
       * configuration requires knowing the version number.
       */
      spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
      spa->spa_ubsync.ub_version = version;
      error = spa_config_parse(spa, &rvd, nvroot, NULL, 0, VDEV_ALLOC_LOAD);
      spa_config_exit(spa, SCL_ALL, FTAG);

      if (error != 0)
            goto out;

      ASSERT(spa->spa_root_vdev == rvd);
      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)
            goto out;

      /*
       * 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.
       */
      spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
      error = vdev_validate(rvd);
      spa_config_exit(spa, SCL_ALL, FTAG);
      if (error != 0)
            goto out;

      if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN) {
            dprintf("spa_load(): rvd->vdev_state <= VDEV_STATE_CANT_OPEN\n");
            error = ENXIO;
            goto out;
      }

      /*
       * 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) {
            dprintf("spa_load(): can't find single valid uberblock\n");
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = ENXIO;
            goto out;
      }

      /*
       * If the pool is newer than the code, we can't open it.
       */
      if (ub->ub_version > SPA_VERSION) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_VERSION_NEWER);
            error = ENOTSUP;
            goto out;
      }

      /*
       * If the vdev guid sum doesn't match the uberblock, we have an
       * incomplete configuration.
       */
      if (rvd->vdev_guid_sum != ub->ub_guid_sum && mosconfig) {
            dprintf("spa_load(): vdev guid sum doesn't match the uberblock\n");
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_BAD_GUID_SUM);
            error = ENXIO;
            goto out;
      }

      /*
       * Initialize internal SPA structures.
       */
      spa->spa_state = POOL_STATE_ACTIVE;
      spa->spa_ubsync = spa->spa_uberblock;
      spa->spa_first_txg = spa_last_synced_txg(spa) + 1;
      error = dsl_pool_open(spa, spa->spa_first_txg, &spa->spa_dsl_pool);
      if (error) {
            dprintf("spa_load(): error %i in dsl_pool_open()\n", error);
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            goto out;
      }
      spa->spa_meta_objset = spa->spa_dsl_pool->dp_meta_objset;

      if (zap_lookup(spa->spa_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CONFIG,
          sizeof (uint64_t), 1, &spa->spa_config_object) != 0) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      if (!mosconfig) {
            nvlist_t *newconfig;
            uint64_t hostid;

            if (load_nvlist(spa, spa->spa_config_object, &newconfig) != 0) {
                  vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  error = EIO;
                  goto out;
            }

            if (!spa_is_root(spa) && nvlist_lookup_uint64(newconfig,
                ZPOOL_CONFIG_HOSTID, &hostid) == 0) {
                  char *hostname;
                  unsigned long myhostid = 0;

                  VERIFY(nvlist_lookup_string(newconfig,
                      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) {
                        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);
                        error = EBADF;
                        goto out;
                  }
            }

            spa_config_set(spa, newconfig);
            spa_unload(spa);
            spa_deactivate(spa);
            spa_activate(spa, orig_mode);

            return (spa_load(spa, newconfig, state, B_TRUE));
      }

      if (zap_lookup(spa->spa_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_SYNC_BPLIST,
          sizeof (uint64_t), 1, &spa->spa_sync_bplist_obj) != 0) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      /*
       * 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 = zap_lookup(spa->spa_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
          sizeof (uint64_t), 1, &spa->spa_deflate);
      if (error != 0 && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      /*
       * Load the persistent error log.  If we have an older pool, this will
       * not be present.
       */
      error = zap_lookup(spa->spa_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ERRLOG_LAST,
          sizeof (uint64_t), 1, &spa->spa_errlog_last);
      if (error != 0 && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      error = zap_lookup(spa->spa_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_ERRLOG_SCRUB,
          sizeof (uint64_t), 1, &spa->spa_errlog_scrub);
      if (error != 0 && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      /*
       * Load the history object.  If we have an older pool, this
       * will not be present.
       */
      error = zap_lookup(spa->spa_meta_objset,
          DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_HISTORY,
          sizeof (uint64_t), 1, &spa->spa_history);
      if (error != 0 && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      /*
       * Load any hot spares for this pool.
       */
      error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_SPARES, sizeof (uint64_t), 1, &spa->spa_spares.sav_object);
      if (error != 0 && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }
      if (error == 0) {
            ASSERT(spa_version(spa) >= SPA_VERSION_SPARES);
            if (load_nvlist(spa, spa->spa_spares.sav_object,
                &spa->spa_spares.sav_config) != 0) {
                  vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  error = EIO;
                  goto out;
            }

            spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
            spa_load_spares(spa);
            spa_config_exit(spa, SCL_ALL, FTAG);
      }

      /*
       * Load any level 2 ARC devices for this pool.
       */
      error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_L2CACHE, sizeof (uint64_t), 1,
          &spa->spa_l2cache.sav_object);
      if (error != 0 && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }
      if (error == 0) {
            ASSERT(spa_version(spa) >= SPA_VERSION_L2CACHE);
            if (load_nvlist(spa, spa->spa_l2cache.sav_object,
                &spa->spa_l2cache.sav_config) != 0) {
                  vdev_set_state(rvd, B_TRUE,
                      VDEV_STATE_CANT_OPEN,
                      VDEV_AUX_CORRUPT_DATA);
                  error = EIO;
                  goto out;
            }

            spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
            spa_load_l2cache(spa);
            spa_config_exit(spa, SCL_ALL, FTAG);
      }

      spa_load_log_state(spa);

      if (spa_check_logs(spa)) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_BAD_LOG);
            error = ENXIO;
            ereport = FM_EREPORT_ZFS_LOG_REPLAY;
            goto out;
      }


      spa->spa_delegation = zpool_prop_default_numeric(ZPOOL_PROP_DELEGATION);

      error = zap_lookup(spa->spa_meta_objset, DMU_POOL_DIRECTORY_OBJECT,
          DMU_POOL_PROPS, sizeof (uint64_t), 1, &spa->spa_pool_props_object);

      if (error && error != ENOENT) {
            vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            error = EIO;
            goto out;
      }

      if (error == 0) {
            (void) zap_lookup(spa->spa_meta_objset,
                spa->spa_pool_props_object,
                zpool_prop_to_name(ZPOOL_PROP_BOOTFS),
                sizeof (uint64_t), 1, &spa->spa_bootfs);
            (void) zap_lookup(spa->spa_meta_objset,
                spa->spa_pool_props_object,
                zpool_prop_to_name(ZPOOL_PROP_AUTOREPLACE),
                sizeof (uint64_t), 1, &autoreplace);
            (void) zap_lookup(spa->spa_meta_objset,
                spa->spa_pool_props_object,
                zpool_prop_to_name(ZPOOL_PROP_DELEGATION),
                sizeof (uint64_t), 1, &spa->spa_delegation);
            (void) zap_lookup(spa->spa_meta_objset,
                spa->spa_pool_props_object,
                zpool_prop_to_name(ZPOOL_PROP_FAILUREMODE),
                sizeof (uint64_t), 1, &spa->spa_failmode);
      }

      /*
       * 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 (autoreplace && state != SPA_LOAD_TRYIMPORT)
            spa_check_removed(spa->spa_root_vdev);

      /*
       * 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) {
            dprintf("spa_load(): one or more toplevel vdevs are faulted\n");
            error = ENXIO;
            goto out;
      }

      if (spa_writeable(spa)) {
            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.
             */
            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_log_state = SPA_LOG_GOOD;
            spa->spa_sync_on = B_TRUE;
            txg_sync_start(spa->spa_dsl_pool);

            /*
             * Wait for all claims to sync.
             */
            txg_wait_synced(spa->spa_dsl_pool, 0);

            /*
             * If the config cache is stale, or we have uninitialized
             * metaslabs (see spa_vdev_add()), then update the config.
             */
            if (config_cache_txg != spa->spa_config_txg ||
                state == SPA_LOAD_IMPORT)
                  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 (vdev_resilver_needed(rvd, NULL, NULL))
                  spa_async_request(spa, SPA_ASYNC_RESILVER);
      }

      error = 0;
out:
      spa->spa_minref = refcount_count(&spa->spa_refcount);
      if (error && error != EBADF)
            zfs_ereport_post(ereport, spa, NULL, NULL, 0, 0);
      if (error)
            dprintf("spa_load(): error %i\n", error);
      spa->spa_load_state = SPA_LOAD_NONE;
      spa->spa_ena = 0;

      return (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 **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_activate(spa, spa_mode_global);

            error = spa_load(spa, spa->spa_config, SPA_LOAD_OPEN, B_FALSE);

            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_root_vdev != NULL)
                        *config = spa_config_generate(spa, NULL, -1ULL,
                            B_TRUE);
                  spa_unload(spa);
                  spa_deactivate(spa);
                  spa->spa_last_open_failed = B_TRUE;
                  if (locked)
                        mutex_exit(&spa_namespace_lock);
                  *spapp = NULL;
                  return (error);
            } else {
                  spa->spa_last_open_failed = B_FALSE;
            }
      }

      spa_open_ref(spa, tag);

      if (locked)
            mutex_exit(&spa_namespace_lock);

      *spapp = spa;

      if (config != NULL)
            *config = spa_config_generate(spa, NULL, -1ULL, B_TRUE);

      return (0);
}

int
spa_open(const char *name, spa_t **spapp, void *tag)
{
      return (spa_open_common(name, spapp, tag, 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_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_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, 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 c, error = 0;
      uint64_t txg = TXG_INITIAL;
      nvlist_t **spares, **l2cache;
      uint_t nspares, nl2cache;
      uint64_t version;

      /*
       * 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, altroot);
      spa_activate(spa, spa_mode_global);

      spa->spa_uberblock.ub_txg = txg - 1;

      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_uberblock.ub_version = version;
      spa->spa_ubsync = spa->spa_uberblock;

      /*
       * Create "The Godfather" zio to hold all async IOs
       */
      spa->spa_async_zio_root = zio_root(spa, NULL, NULL,
          ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE | ZIO_FLAG_GODFATHER);

      /*
       * Create the root vdev.
       */
      spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);

      error = spa_config_parse(spa, &rvd, nvroot, NULL, 0, VDEV_ALLOC_ADD);

      ASSERT(error != 0 || rvd != NULL);
      ASSERT(error != 0 || spa->spa_root_vdev == rvd);

      if (error == 0 && !zfs_allocatable_devs(nvroot))
            error = EINVAL;

      if (error == 0 &&
          (error = vdev_create(rvd, txg, B_FALSE)) == 0 &&
          (error = spa_validate_aux(spa, nvroot, txg,
          VDEV_ALLOC_ADD)) == 0) {
            for (c = 0; c < rvd->vdev_children; c++)
                  vdev_init(rvd->vdev_child[c], txg);
            vdev_config_dirty(rvd);
      }

      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;

      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");
      }

      /* 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_sync_bplist_obj = bplist_create(spa->spa_meta_objset,
          1 << 14, tx);
      dmu_object_set_compress(spa->spa_meta_objset, spa->spa_sync_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_sync_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);
      if (props != NULL) {
            spa_configfile_set(spa, props, B_FALSE);
            spa_sync_props(spa, props, CRED(), 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->spa_minref = refcount_count(&spa->spa_refcount);

      mutex_exit(&spa_namespace_lock);

      return (0);
}

/* ZFSFUSE: not needed */
#if 0
/*
 * Build a "root" vdev for a top level vdev read in from a rootpool
 * device label.
 */
static void
spa_build_rootpool_config(nvlist_t *config)
{
      nvlist_t *nvtop, *nvroot;
      uint64_t pgid;

      /*
       * 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);

      /*
       * 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);
}

/*
 * 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 **);

int
spa_check_rootconf(char *devpath, char *devid, nvlist_t **bestconf,
    uint64_t *besttxg)
{
      nvlist_t *config;
      uint64_t txg;
      int error;

      if (error = vdev_disk_read_rootlabel(devpath, devid, &config))
            return (error);

      VERIFY(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_TXG, &txg) == 0);

      if (bestconf != NULL)
            *bestconf = config;
      else
            nvlist_free(config);
      *besttxg = txg;
      return (0);
}

boolean_t
spa_rootdev_validate(nvlist_t *nv)
{
      uint64_t ival;

      if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_OFFLINE, &ival) == 0 ||
          nvlist_lookup_uint64(nv, ZPOOL_CONFIG_FAULTED, &ival) == 0 ||
          nvlist_lookup_uint64(nv, ZPOOL_CONFIG_REMOVED, &ival) == 0)
            return (B_FALSE);

      return (B_TRUE);
}


/*
 * Given the boot device's physical path or devid, check if the device
 * is in a valid state.  If so, return the configuration from the vdev
 * label.
 */
int
spa_get_rootconf(char *devpath, char *devid, nvlist_t **bestconf)
{
      nvlist_t *conf = NULL;
      uint64_t txg = 0;
      nvlist_t *nvtop, **child;
      char *type;
      char *bootpath = NULL;
      uint_t children, c;
      char *tmp;
      int error;

      if (devpath && ((tmp = strchr(devpath, ' ')) != NULL))
            *tmp = '\0';
      if (error = spa_check_rootconf(devpath, devid, &conf, &txg)) {
            cmn_err(CE_NOTE, "error reading device label");
            return (error);
      }
      if (txg == 0) {
            cmn_err(CE_NOTE, "this device is detached");
            nvlist_free(conf);
            return (EINVAL);
      }

      VERIFY(nvlist_lookup_nvlist(conf, ZPOOL_CONFIG_VDEV_TREE,
          &nvtop) == 0);
      VERIFY(nvlist_lookup_string(nvtop, ZPOOL_CONFIG_TYPE, &type) == 0);

      if (strcmp(type, VDEV_TYPE_DISK) == 0) {
            if (spa_rootdev_validate(nvtop)) {
                  goto out;
            } else {
                  nvlist_free(conf);
                  return (EINVAL);
            }
      }

      ASSERT(strcmp(type, VDEV_TYPE_MIRROR) == 0);

      VERIFY(nvlist_lookup_nvlist_array(nvtop, ZPOOL_CONFIG_CHILDREN,
          &child, &children) == 0);

      /*
       * Go thru vdevs in the mirror to see if the given device
       * has the most recent txg. Only the device with the most
       * recent txg has valid information and should be booted.
       */
      for (c = 0; c < children; c++) {
            char *cdevid, *cpath;
            uint64_t tmptxg;

            cpath = NULL;
            cdevid = NULL;
            (void) nvlist_lookup_string(child[c], ZPOOL_CONFIG_PHYS_PATH,
                &cpath);
            (void) nvlist_lookup_string(child[c], ZPOOL_CONFIG_DEVID,
                &cdevid);
            if (cpath == NULL && cdevid == NULL)
                  return (EINVAL);
            if ((spa_check_rootconf(cpath, cdevid, NULL,
                &tmptxg) == 0) && (tmptxg > txg)) {
                  txg = tmptxg;
                  VERIFY(nvlist_lookup_string(child[c],
                      ZPOOL_CONFIG_PATH, &bootpath) == 0);
            }
      }

      /* Does the best device match the one we've booted from? */
      if (bootpath) {
            cmn_err(CE_NOTE, "try booting from '%s'", bootpath);
            return (EINVAL);
      }
out:
      *bestconf = conf;
      return (0);
}

/*
 * 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)
{
      nvlist_t *conf = NULL;
      char *pname;
      int error;
      spa_t *spa;

      /*
       * Get the vdev pathname and configuation from the most
       * recently updated vdev (highest txg).
       */
      if (error = spa_get_rootconf(devpath, devid, &conf))
            goto msg_out;

      /*
       * Add type "root" vdev to the config.
       */
      spa_build_rootpool_config(conf);

      VERIFY(nvlist_lookup_string(conf, ZPOOL_CONFIG_POOL_NAME, &pname) == 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, NULL);

      spa->spa_is_root = B_TRUE;
      VERIFY(nvlist_dup(conf, &spa->spa_config, 0) == 0);
      mutex_exit(&spa_namespace_lock);

      nvlist_free(conf);
      return (0);

msg_out:
      cmn_err(CE_NOTE, "\n"
          "  ***************************************************  \n"
          "  *  This device is not bootable!                   *  \n"
          "  *  It is either offlined or detached or faulted.  *  \n"
          "  *  Please try to boot from a different device.    *  \n"
          "  ***************************************************  ");

      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, altroot);

      VERIFY(nvlist_dup(config, &spa->spa_config, 0) == 0);

      if (props != NULL)
            spa_configfile_set(spa, props, B_FALSE);

      spa_config_sync(spa, B_FALSE, B_TRUE);

      mutex_exit(&spa_namespace_lock);

      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;
      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 = spa_lookup(pool)) != NULL) {
            mutex_exit(&spa_namespace_lock);
            return (EEXIST);
      }

      /*
       * Create and initialize the spa structure.
       */
      (void) nvlist_lookup_string(props,
          zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
      spa = spa_add(pool, 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.
       */
      error = spa_load(spa, config, SPA_LOAD_IMPORT, B_TRUE);

      spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
      /*
       * Toss any existing sparelist, as it doesn't have any validity
       * anymore, and conflicts with spa_has_spare().
       */
      if (spa->spa_spares.sav_config) {
            nvlist_free(spa->spa_spares.sav_config);
            spa->spa_spares.sav_config = NULL;
            spa_load_spares(spa);
      }
      if (spa->spa_l2cache.sav_config) {
            nvlist_free(spa->spa_l2cache.sav_config);
            spa->spa_l2cache.sav_config = NULL;
            spa_load_l2cache(spa);
      }

      VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
          &nvroot) == 0);
      if (error == 0)
            error = spa_validate_aux(spa, nvroot, -1ULL,
                VDEV_ALLOC_SPARE);
      if (error == 0)
            error = spa_validate_aux(spa, nvroot, -1ULL,
                VDEV_ALLOC_L2CACHE);
      spa_config_exit(spa, SCL_ALL, FTAG);

      if (props != NULL)
            spa_configfile_set(spa, props, B_FALSE);

      if (error != 0 || (props && spa_writeable(spa) &&
          (error = spa_prop_set(spa, props)))) {
            spa_unload(spa);
            spa_deactivate(spa);
            spa_remove(spa);
            mutex_exit(&spa_namespace_lock);
            return (error);
      }

      spa_async_resume(spa);

      /*
       * Override any spares and level 2 cache devices as specified by
       * the user, as these may have correct device names/devids, etc.
       */
      if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES,
          &spares, &nspares) == 0) {
            if (spa->spa_spares.sav_config)
                  VERIFY(nvlist_remove(spa->spa_spares.sav_config,
                      ZPOOL_CONFIG_SPARES, DATA_TYPE_NVLIST_ARRAY) == 0);
            else
                  VERIFY(nvlist_alloc(&spa->spa_spares.sav_config,
                      NV_UNIQUE_NAME, KM_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;
      }

      if (spa_writeable(spa)) {
            /*
             * Update the config cache to include the newly-imported pool.
             */
            spa_config_update_common(spa, SPA_CONFIG_UPDATE_POOL, B_FALSE);
      }

      mutex_exit(&spa_namespace_lock);

      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, 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, tryconfig, SPA_LOAD_TRYIMPORT, 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) + 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;
      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++) {
            tvd = vd->vdev_child[c];
            vdev_remove_child(vd, tvd);
            tvd->vdev_id = rvd->vdev_children;
            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, open_txg;
      vdev_t *rvd = spa->spa_root_vdev;
      vdev_t *oldvd, *newvd, *newrootvd, *pvd, *tvd;
      vdev_ops_t *pvops;
      dmu_tx_t *tx;
      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;
      }

      /*
       * Compare the new device size with the replaceable/attachable
       * device size.
       */
      if (newvd->vdev_psize < vdev_get_rsize(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;
      vdev_add_child(pvd, newvd);

      /*
       * If newvd is smaller than oldvd, but larger than its rsize,
       * the addition of newvd may have decreased our parent's asize.
       */
      pvd->vdev_asize = MIN(pvd->vdev_asize, newvd->vdev_asize);

      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, open_txg].  It will propagate
       * upward when spa_vdev_exit() calls vdev_dtl_reassess().
       */
      open_txg = txg + TXG_CONCURRENT_STATES - 1;

      vdev_dtl_dirty(newvd, DTL_MISSING,
          TXG_INITIAL, open_txg - TXG_INITIAL + 1);

      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);

      (void) spa_vdev_exit(spa, newrootvd, open_txg, 0);

      tx = dmu_tx_create_dd(spa_get_dsl(spa)->dp_mos_dir);
      if (dmu_tx_assign(tx, TXG_WAIT) == 0) {
            spa_history_internal_log(LOG_POOL_VDEV_ATTACH, spa, tx,
                CRED(),  "%s vdev=%s %s vdev=%s",
                replacing && newvd_isspare ? "spare in" :
                replacing ? "replace" : "attach", newvdpath,
                replacing ? "for" : "to", oldvdpath);
            dmu_tx_commit(tx);
      } else {
            dmu_tx_abort(tx);
      }

      spa_strfree(oldvdpath);
      spa_strfree(newvdpath);

      /*
       * Kick off a resilver to update newvd.
       */
      VERIFY3U(spa_scrub(spa, POOL_SCRUB_RESILVER), ==, 0);

      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;

      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 device we just detached was smaller than the others, it may be
       * possible to add metaslabs (i.e. grow the pool).  vdev_metaslab_init()
       * can't fail because the existing metaslabs are already in core, so
       * there's nothing to read from disk.
       */
      VERIFY(vdev_metaslab_init(tvd, txg) == 0);

      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.
       */
      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);

      /*
       * 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);
}

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 *));
}

/*
 * Remove a device from the pool.  Currently, this supports removing only hot
 * spares and level 2 ARC devices.
 */
int
spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare)
{
      vdev_t *vd;
      nvlist_t **spares, **l2cache, *nv;
      uint_t nspares, nl2cache;
      uint64_t txg = 0;
      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) {
            /*
             * Normal vdevs cannot be removed (yet).
             */
            error = ENOTSUP;
      } else {
            /*
             * There is no vdev of any kind with the specified guid.
             */
            error = ENOENT;
      }

      if (!locked)
            return (spa_vdev_exit(spa, NULL, txg, error));

      return (error);
}

/*
 * Find any device that's done replacing, or a vdev marked 'unspare' that's
 * current spared, so we can detach it.
 */
static vdev_t *
spa_vdev_resilver_done_hunt(vdev_t *vd)
{
      vdev_t *newvd, *oldvd;
      int c;

      for (c = 0; c < vd->vdev_children; c++) {
            oldvd = spa_vdev_resilver_done_hunt(vd->vdev_child[c]);
            if (oldvd != NULL)
                  return (oldvd);
      }

      /*
       * Check for a completed replacement.
       */
      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_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_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.  Dirty the vdev configuration,
 * relying on spa_vdev_enter/exit() to synchronize the labels and cache.
 */
int
spa_vdev_set_common(spa_t *spa, uint64_t guid, const char *value,
    boolean_t ispath)
{
      vdev_t *vd;
      uint64_t txg;

      txg = spa_vdev_enter(spa);

      if ((vd = spa_lookup_by_guid(spa, guid, B_TRUE)) == NULL)
            return (spa_vdev_exit(spa, NULL, txg, ENOENT));

      if (!vd->vdev_ops->vdev_op_leaf)
            return (spa_vdev_exit(spa, NULL, txg, ENOTSUP));

      if (ispath) {
            spa_strfree(vd->vdev_path);
            vd->vdev_path = spa_strdup(value);
      } else {
            if (vd->vdev_fru != NULL)
                  spa_strfree(vd->vdev_fru);
            vd->vdev_fru = spa_strdup(value);
      }

      vdev_config_dirty(vd->vdev_top);

      return (spa_vdev_exit(spa, NULL, txg, 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 Scrubbing
 * ==========================================================================
 */

int
spa_scrub(spa_t *spa, pool_scrub_type_t type)
{
      ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);

      if ((uint_t)type >= POOL_SCRUB_TYPES)
            return (ENOTSUP);

      /*
       * If a resilver was requested, but there is no DTL on a
       * writeable leaf device, we have nothing to do.
       */
      if (type == POOL_SCRUB_RESILVER &&
          !vdev_resilver_needed(spa->spa_root_vdev, NULL, NULL)) {
            spa_async_request(spa, SPA_ASYNC_RESILVER_DONE);
            return (0);
      }

      if (type == POOL_SCRUB_EVERYTHING &&
          spa->spa_dsl_pool->dp_scrub_func != SCRUB_FUNC_NONE &&
          spa->spa_dsl_pool->dp_scrub_isresilver)
            return (EBUSY);

      if (type == POOL_SCRUB_EVERYTHING || type == POOL_SCRUB_RESILVER) {
            return (dsl_pool_scrub_clean(spa->spa_dsl_pool));
      } else if (type == POOL_SCRUB_NONE) {
            return (dsl_pool_scrub_cancel(spa->spa_dsl_pool));
      } else {
            return (EINVAL);
      }
}

/*
 * ==========================================================================
 * 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);
            vdev_clear(spa, vd);
            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_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) {
            mutex_enter(&spa_namespace_lock);
            spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
            mutex_exit(&spa_namespace_lock);
      }

      /*
       * See if any devices need to be marked REMOVED.
       */
      if (tasks & SPA_ASYNC_REMOVE) {
            spa_vdev_state_enter(spa);
            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);
      }

      /*
       * See if any devices need to be probed.
       */
      if (tasks & SPA_ASYNC_PROBE) {
            spa_vdev_state_enter(spa);
            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)
            VERIFY(spa_scrub(spa, POOL_SCRUB_RESILVER) == 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)
{
      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_frees(spa_t *spa, uint64_t txg)
{
      bplist_t *bpl = &spa->spa_sync_bplist;
      dmu_tx_t *tx;
      blkptr_t blk;
      uint64_t itor = 0;
      zio_t *zio;
      int error;
      uint8_t c = 1;

      zio = zio_root(spa, NULL, NULL, ZIO_FLAG_CANFAIL);

      while (bplist_iterate(bpl, &itor, &blk) == 0) {
            ASSERT(blk.blk_birth < txg);
            zio_nowait(zio_free(zio, spa, txg, &blk, NULL, NULL,
                ZIO_FLAG_MUSTSUCCEED));
      }

      error = zio_wait(zio);
      ASSERT3U(error, ==, 0);

      tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);
      bplist_vacate(bpl, tx);

      /*
       * Pre-dirty the first block so we sync to convergence faster.
       * (Usually only the first block is needed.)
       */
      dmu_write(spa->spa_meta_objset, spa->spa_sync_bplist_obj, 0, 1, &c, tx);
      dmu_tx_commit(tx);
}

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, B_FALSE, B_TRUE);
            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, cred_t *cr, 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) {
                        objset_t *mos = spa->spa_meta_objset;

                        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;
                  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_internal_log(LOG_POOL_PROPSET,
                      spa, tx, cr, "%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 *bpl = &spa->spa_sync_bplist;
      vdev_t *rvd = spa->spa_root_vdev;
      vdev_t *vd;
      dmu_tx_t *tx;
      int dirty_vdevs;
      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(bpl, mos, spa->spa_sync_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, 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))
            spa_sync_deferred_frees(spa, txg);

      /*
       * Iterate to convergence.
       */
      do {
            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);

            dirty_vdevs = 0;
            while (vd = txg_list_remove(&spa->spa_vdev_txg_list, txg)) {
                  vdev_sync(vd, txg);
                  dirty_vdevs++;
            }

            bplist_sync(bpl, tx);
      } while (dirty_vdevs);

      bplist_close(bpl);

      dprintf("txg %llu passes %d\n", txg, spa->spa_sync_pass);

      /*
       * 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);
                  int c;

                  for (c = 0; c < children; c++) {
                        vd = rvd->vdev_child[(c0 + c) % children];
                        if (vd->vdev_ms_array == 0 || vd->vdev_islog)
                              continue;
                        svd[svdcount++] = vd;
                        if (svdcount == SPA_DVAS_PER_BP)
                              break;
                  }
                  error = vdev_config_sync(svd, svdcount, txg, B_FALSE);
                  if (error != 0)
                        error = vdev_config_sync(svd, svdcount, txg,
                            B_TRUE);
            } else {
                  error = vdev_config_sync(rvd->vdev_child,
                      rvd->vdev_children, txg, B_FALSE);
                  if (error != 0)
                        error = vdev_config_sync(rvd->vdev_child,
                            rvd->vdev_children, txg, B_TRUE);
            }

            spa_config_exit(spa, SCL_STATE, FTAG);

            if (error == 0)
                  break;
            zio_suspend(spa, NULL);
            zio_resume_wait(spa);
      }
      dmu_tx_commit(tx);

      /*
       * Clear the dirty config list.
       */
      while ((vd = list_head(&spa->spa_config_dirty_list)) != NULL)
            vdev_config_clean(vd);

      /*
       * Now that the new config has synced transactionally,
       * let it become visible to the config cache.
       */
      if (spa->spa_config_syncing != NULL) {
            spa_config_set(spa, spa->spa_config_syncing);
            spa->spa_config_txg = txg;
            spa->spa_config_syncing = NULL;
      }

      spa->spa_ubsync = spa->spa_uberblock;

      /*
       * Clean up the ZIL records for the synced txg.
       */
      dsl_pool_zil_clean(dp);

      /*
       * Update usable space statistics.
       */
      while (vd = txg_list_remove(&spa->spa_vdev_txg_list, TXG_CLEAN(txg)))
            vdev_sync_done(vd, txg);

      /*
       * 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(bpl->bpl_queue == NULL);

      spa_config_exit(spa, SCL_CONFIG, FTAG);

      /*
       * 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
}

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