6897693 deduplication can only go so far

[illumos-gate.git] / usr / src / uts / common / fs / zfs / 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/dmu.h>
#include <sys/dmu_tx.h>
#include <sys/zap.h>
#include <sys/zil.h>
#include <sys/ddt.h>
#include <sys/vdev_impl.h>
#include <sys/metaslab.h>
#include <sys/metaslab_impl.h>
#include <sys/uberblock_impl.h>
#include <sys/txg.h>
#include <sys/avl.h>
#include <sys/dmu_traverse.h>
#include <sys/dmu_objset.h>
#include <sys/unique.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_synctask.h>
#include <sys/fs/zfs.h>
#include <sys/arc.h>
#include <sys/callb.h>
#include <sys/systeminfo.h>
#include <sys/sunddi.h>
#include <sys/spa_boot.h>
#include <sys/zfs_ioctl.h>

#ifdef  _KERNEL
#include <sys/zone.h>
#include <sys/bootprops.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 alloc;
        uint64_t cap, version;
        zprop_source_t src = ZPROP_SRC_NONE;
        spa_config_dirent_t *dp;

        ASSERT(MUTEX_HELD(&spa->spa_props_lock));

        if (spa->spa_root_vdev != NULL) {
                alloc = metaslab_class_get_alloc(spa_normal_class(spa));
                size = metaslab_class_get_space(spa_normal_class(spa));
                spa_prop_add_list(*nvp, ZPOOL_PROP_NAME, spa_name(spa), 0, src);
                spa_prop_add_list(*nvp, ZPOOL_PROP_SIZE, NULL, size, src);
                spa_prop_add_list(*nvp, ZPOOL_PROP_ALLOCATED, NULL, alloc, src);
                spa_prop_add_list(*nvp, ZPOOL_PROP_FREE, NULL,
                    size - alloc, src);

                cap = (size == 0) ? 0 : (alloc * 100 / size);
                spa_prop_add_list(*nvp, ZPOOL_PROP_CAPACITY, NULL, cap, src);

                spa_prop_add_list(*nvp, ZPOOL_PROP_DEDUPRATIO, NULL,
                    ddt_get_pool_dedup_ratio(spa), src);

                spa_prop_add_list(*nvp, ZPOOL_PROP_HEALTH, NULL,
                    spa->spa_root_vdev->vdev_state, src);

                version = spa_version(spa);
                if (version == zpool_prop_default_numeric(ZPOOL_PROP_VERSION))
                        src = ZPROP_SRC_DEFAULT;
                else
                        src = ZPROP_SRC_LOCAL;
                spa_prop_add_list(*nvp, ZPOOL_PROP_VERSION, NULL, version, src);
        }

        spa_prop_add_list(*nvp, ZPOOL_PROP_GUID, NULL, spa_guid(spa), src);

        if (spa->spa_root != NULL)
                spa_prop_add_list(*nvp, ZPOOL_PROP_ALTROOT, spa->spa_root,
                    0, ZPROP_SRC_LOCAL);

        if ((dp = list_head(&spa->spa_config_list)) != NULL) {
                if (dp->scd_path == NULL) {
                        spa_prop_add_list(*nvp, ZPOOL_PROP_CACHEFILE,
                            "none", 0, ZPROP_SRC_LOCAL);
                } else if (strcmp(dp->scd_path, spa_config_path) != 0) {
                        spa_prop_add_list(*nvp, ZPOOL_PROP_CACHEFILE,
                            dp->scd_path, 0, ZPROP_SRC_LOCAL);
                }
        }
}

/*
 * Get zpool property values.
 */
int
spa_prop_get(spa_t *spa, nvlist_t **nvp)
{
        objset_t *mos = spa->spa_meta_objset;
        zap_cursor_t zc;
        zap_attribute_t za;
        int err;

        VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);

        mutex_enter(&spa->spa_props_lock);

        /*
         * Get properties from the spa config.
         */
        spa_prop_get_config(spa, nvp);

        /* If no pool property object, no more prop to get. */
        if (spa->spa_pool_props_object == 0) {
                mutex_exit(&spa->spa_props_lock);
                return (0);
        }

        /*
         * Get properties from the MOS pool property object.
         */
        for (zap_cursor_init(&zc, mos, spa->spa_pool_props_object);
            (err = zap_cursor_retrieve(&zc, &za)) == 0;
            zap_cursor_advance(&zc)) {
                uint64_t intval = 0;
                char *strval = NULL;
                zprop_source_t src = ZPROP_SRC_DEFAULT;
                zpool_prop_t prop;

                if ((prop = zpool_name_to_prop(za.za_name)) == ZPROP_INVAL)
                        continue;

                switch (za.za_integer_length) {
                case 8:
                        /* integer property */
                        if (za.za_first_integer !=
                            zpool_prop_default_numeric(prop))
                                src = ZPROP_SRC_LOCAL;

                        if (prop == ZPOOL_PROP_BOOTFS) {
                                dsl_pool_t *dp;
                                dsl_dataset_t *ds = NULL;

                                dp = spa_get_dsl(spa);
                                rw_enter(&dp->dp_config_rwlock, RW_READER);
                                if (err = dsl_dataset_hold_obj(dp,
                                    za.za_first_integer, FTAG, &ds)) {
                                        rw_exit(&dp->dp_config_rwlock);
                                        break;
                                }

                                strval = kmem_alloc(
                                    MAXNAMELEN + strlen(MOS_DIR_NAME) + 1,
                                    KM_SLEEP);
                                dsl_dataset_name(ds, strval);
                                dsl_dataset_rele(ds, FTAG);
                                rw_exit(&dp->dp_config_rwlock);
                        } else {
                                strval = NULL;
                                intval = za.za_first_integer;
                        }

                        spa_prop_add_list(*nvp, prop, strval, intval, src);

                        if (strval != NULL)
                                kmem_free(strval,
                                    MAXNAMELEN + strlen(MOS_DIR_NAME) + 1);

                        break;

                case 1:
                        /* string property */
                        strval = kmem_alloc(za.za_num_integers, KM_SLEEP);
                        err = zap_lookup(mos, spa->spa_pool_props_object,
                            za.za_name, 1, za.za_num_integers, strval);
                        if (err) {
                                kmem_free(strval, za.za_num_integers);
                                break;
                        }
                        spa_prop_add_list(*nvp, prop, strval, 0, src);
                        kmem_free(strval, za.za_num_integers);
                        break;

                default:
                        break;
                }
        }
        zap_cursor_fini(&zc);
        mutex_exit(&spa->spa_props_lock);
out:
        if (err && err != ENOENT) {
                nvlist_free(*nvp);
                *nvp = NULL;
                return (err);
        }

        return (0);
}

/*
 * Validate the given pool properties nvlist and modify the list
 * for the property values to be set.
 */
static int
spa_prop_validate(spa_t *spa, nvlist_t *props)
{
        nvpair_t *elem;
        int error = 0, reset_bootfs = 0;
        uint64_t objnum;

        elem = NULL;
        while ((elem = nvlist_next_nvpair(props, elem)) != NULL) {
                zpool_prop_t prop;
                char *propname, *strval;
                uint64_t intval;
                objset_t *os;
                char *slash;

                propname = nvpair_name(elem);

                if ((prop = zpool_name_to_prop(propname)) == ZPROP_INVAL)
                        return (EINVAL);

                switch (prop) {
                case ZPOOL_PROP_VERSION:
                        error = nvpair_value_uint64(elem, &intval);
                        if (!error &&
                            (intval < spa_version(spa) || intval > SPA_VERSION))
                                error = EINVAL;
                        break;

                case ZPOOL_PROP_DELEGATION:
                case ZPOOL_PROP_AUTOREPLACE:
                case ZPOOL_PROP_LISTSNAPS:
                case ZPOOL_PROP_AUTOEXPAND:
                        error = nvpair_value_uint64(elem, &intval);
                        if (!error && intval > 1)
                                error = EINVAL;
                        break;

                case ZPOOL_PROP_BOOTFS:
                        /*
                         * If the pool version is less than SPA_VERSION_BOOTFS,
                         * or the pool is still being created (version == 0),
                         * the bootfs property cannot be set.
                         */
                        if (spa_version(spa) < SPA_VERSION_BOOTFS) {
                                error = ENOTSUP;
                                break;
                        }

                        /*
                         * Make sure the vdev config is bootable
                         */
                        if (!vdev_is_bootable(spa->spa_root_vdev)) {
                                error = ENOTSUP;
                                break;
                        }

                        reset_bootfs = 1;

                        error = nvpair_value_string(elem, &strval);

                        if (!error) {
                                uint64_t compress;

                                if (strval == NULL || strval[0] == '\0') {
                                        objnum = zpool_prop_default_numeric(
                                            ZPOOL_PROP_BOOTFS);
                                        break;
                                }

                                if (error = dmu_objset_hold(strval, FTAG, &os))
                                        break;

                                /* Must be ZPL and not gzip compressed. */

                                if (dmu_objset_type(os) != DMU_OST_ZFS) {
                                        error = ENOTSUP;
                                } else if ((error = dsl_prop_get_integer(strval,
                                    zfs_prop_to_name(ZFS_PROP_COMPRESSION),
                                    &compress, NULL)) == 0 &&
                                    !BOOTFS_COMPRESS_VALID(compress)) {
                                        error = ENOTSUP;
                                } else {
                                        objnum = dmu_objset_id(os);
                                }
                                dmu_objset_rele(os, FTAG);
                        }
                        break;

                case ZPOOL_PROP_FAILUREMODE:
                        error = nvpair_value_uint64(elem, &intval);
                        if (!error && (intval < ZIO_FAILURE_MODE_WAIT ||
                            intval > ZIO_FAILURE_MODE_PANIC))
                                error = EINVAL;

                        /*
                         * This is a special case which only occurs when
                         * the pool has completely failed. This allows
                         * the user to change the in-core failmode property
                         * without syncing it out to disk (I/Os might
                         * currently be blocked). We do this by returning
                         * EIO to the caller (spa_prop_set) to trick it
                         * into thinking we encountered a property validation
                         * error.
                         */
                        if (!error && spa_suspended(spa)) {
                                spa->spa_failmode = intval;
                                error = EIO;
                        }
                        break;

                case ZPOOL_PROP_CACHEFILE:
                        if ((error = nvpair_value_string(elem, &strval)) != 0)
                                break;

                        if (strval[0] == '\0')
                                break;

                        if (strcmp(strval, "none") == 0)
                                break;

                        if (strval[0] != '/') {
                                error = EINVAL;
                                break;
                        }

                        slash = strrchr(strval, '/');
                        ASSERT(slash != NULL);

                        if (slash[1] == '\0' || strcmp(slash, "/.") == 0 ||
                            strcmp(slash, "/..") == 0)
                                error = EINVAL;
                        break;

                case ZPOOL_PROP_DEDUPDITTO:
                        if (spa_version(spa) < SPA_VERSION_DEDUP)
                                error = ENOTSUP;
                        else
                                error = nvpair_value_uint64(elem, &intval);
                        if (error == 0 &&
                            intval != 0 && intval < ZIO_DEDUPDITTO_MIN)
                                error = EINVAL;
                        break;
                }

                if (error)
                        break;
        }

        if (!error && reset_bootfs) {
                error = nvlist_remove(props,
                    zpool_prop_to_name(ZPOOL_PROP_BOOTFS), DATA_TYPE_STRING);

                if (!error) {
                        error = nvlist_add_uint64(props,
                            zpool_prop_to_name(ZPOOL_PROP_BOOTFS), objnum);
                }
        }

        return (error);
}

void
spa_configfile_set(spa_t *spa, nvlist_t *nvp, boolean_t need_sync)
{
        char *cachefile;
        spa_config_dirent_t *dp;

        if (nvlist_lookup_string(nvp, zpool_prop_to_name(ZPOOL_PROP_CACHEFILE),
            &cachefile) != 0)
                return;

        dp = kmem_alloc(sizeof (spa_config_dirent_t),
            KM_SLEEP);

        if (cachefile[0] == '\0')
                dp->scd_path = spa_strdup(spa_config_path);
        else if (strcmp(cachefile, "none") == 0)
                dp->scd_path = NULL;
        else
                dp->scd_path = spa_strdup(cachefile);

        list_insert_head(&spa->spa_config_list, dp);
        if (need_sync)
                spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);
}

int
spa_prop_set(spa_t *spa, nvlist_t *nvp)
{
        int error;
        nvpair_t *elem;
        boolean_t need_sync = B_FALSE;
        zpool_prop_t prop;

        if ((error = spa_prop_validate(spa, nvp)) != 0)
                return (error);

        elem = NULL;
        while ((elem = nvlist_next_nvpair(nvp, elem)) != NULL) {
                if ((prop = zpool_name_to_prop(
                    nvpair_name(elem))) == ZPROP_INVAL)
                        return (EINVAL);

                if (prop == ZPOOL_PROP_CACHEFILE || prop == ZPOOL_PROP_ALTROOT)
                        continue;

                need_sync = B_TRUE;
                break;
        }

        if (need_sync)
                return (dsl_sync_task_do(spa_get_dsl(spa), NULL, spa_sync_props,
                    spa, nvp, 3));
        else
                return (0);
}

/*
 * If the bootfs property value is dsobj, clear it.
 */
void
spa_prop_clear_bootfs(spa_t *spa, uint64_t dsobj, dmu_tx_t *tx)
{
        if (spa->spa_bootfs == dsobj && spa->spa_pool_props_object != 0) {
                VERIFY(zap_remove(spa->spa_meta_objset,
                    spa->spa_pool_props_object,
                    zpool_prop_to_name(ZPOOL_PROP_BOOTFS), tx) == 0);
                spa->spa_bootfs = 0;
        }
}

/*
 * ==========================================================================
 * SPA state manipulation (open/create/destroy/import/export)
 * ==========================================================================
 */

static int
spa_error_entry_compare(const void *a, const void *b)
{
        spa_error_entry_t *sa = (spa_error_entry_t *)a;
        spa_error_entry_t *sb = (spa_error_entry_t *)b;
        int ret;

        ret = bcmp(&sa->se_bookmark, &sb->se_bookmark,
            sizeof (zbookmark_t));

        if (ret < 0)
                return (-1);
        else if (ret > 0)
                return (1);
        else
                return (0);
}

/*
 * Utility function which retrieves copies of the current logs and
 * re-initializes them in the process.
 */
void
spa_get_errlists(spa_t *spa, avl_tree_t *last, avl_tree_t *scrub)
{
        ASSERT(MUTEX_HELD(&spa->spa_errlist_lock));

        bcopy(&spa->spa_errlist_last, last, sizeof (avl_tree_t));
        bcopy(&spa->spa_errlist_scrub, scrub, sizeof (avl_tree_t));

        avl_create(&spa->spa_errlist_scrub,
            spa_error_entry_compare, sizeof (spa_error_entry_t),
            offsetof(spa_error_entry_t, se_avl));
        avl_create(&spa->spa_errlist_last,
            spa_error_entry_compare, sizeof (spa_error_entry_t),
            offsetof(spa_error_entry_t, se_avl));
}

/*
 * Activate an uninitialized pool.
 */
static void
spa_activate(spa_t *spa, int mode)
{
        ASSERT(spa->spa_state == POOL_STATE_UNINITIALIZED);

        spa->spa_state = POOL_STATE_ACTIVE;
        spa->spa_mode = mode;

        spa->spa_normal_class = metaslab_class_create(spa, zfs_metaslab_ops);
        spa->spa_log_class = metaslab_class_create(spa, zfs_metaslab_ops);

        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;
                }
        }

        metaslab_class_destroy(spa->spa_normal_class);
        spa->spa_normal_class = NULL;

        metaslab_class_destroy(spa->spa_log_class);
        spa->spa_log_class = NULL;

        /*
         * If this was part of an import or the open otherwise failed, we may
         * still have errors left in the queues.  Empty them just in case.
         */
        spa_errlog_drain(spa);

        avl_destroy(&spa->spa_errlist_scrub);
        avl_destroy(&spa->spa_errlist_last);

        spa->spa_state = POOL_STATE_UNINITIALIZED;
}

/*
 * Verify a pool configuration, and construct the vdev tree appropriately.  This
 * will create all the necessary vdevs in the appropriate layout, with each vdev
 * in the CLOSED state.  This will prep the pool before open/creation/import.
 * All vdev validation is done by the vdev_alloc() routine.
 */
static int
spa_config_parse(spa_t *spa, vdev_t **vdp, nvlist_t *nv, vdev_t *parent,
    uint_t id, int atype)
{
        nvlist_t **child;
        uint_t children;
        int error;

        if ((error = vdev_alloc(spa, vdp, nv, parent, id, atype)) != 0)
                return (error);

        if ((*vdp)->vdev_ops->vdev_op_leaf)
                return (0);

        error = nvlist_lookup_nvlist_array(nv, ZPOOL_CONFIG_CHILDREN,
            &child, &children);

        if (error == ENOENT)
                return (0);

        if (error) {
                vdev_free(*vdp);
                *vdp = NULL;
                return (EINVAL);
        }

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

        ASSERT(*vdp != NULL);

        return (0);
}

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

        ASSERT(MUTEX_HELD(&spa_namespace_lock));

        /*
         * Stop 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;
        }

        ddt_unload(spa);

        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);

        /*
         * Drop and purge level 2 cache
         */
        spa_l2cache_drop(spa);

        /*
         * Close all vdevs.
         */
        if (spa->spa_root_vdev)
                vdev_free(spa->spa_root_vdev);
        ASSERT(spa->spa_root_vdev == NULL);

        for (i = 0; i < spa->spa_spares.sav_count; i++)
                vdev_free(spa->spa_spares.sav_vdevs[i]);
        if (spa->spa_spares.sav_vdevs) {
                kmem_free(spa->spa_spares.sav_vdevs,
                    spa->spa_spares.sav_count * sizeof (void *));
                spa->spa_spares.sav_vdevs = NULL;
        }
        if (spa->spa_spares.sav_config) {
                nvlist_free(spa->spa_spares.sav_config);
                spa->spa_spares.sav_config = NULL;
        }
        spa->spa_spares.sav_count = 0;

        for (i = 0; i < spa->spa_l2cache.sav_count; i++)
                vdev_free(spa->spa_l2cache.sav_vdevs[i]);
        if (spa->spa_l2cache.sav_vdevs) {
                kmem_free(spa->spa_l2cache.sav_vdevs,
                    spa->spa_l2cache.sav_count * sizeof (void *));
                spa->spa_l2cache.sav_vdevs = NULL;
        }
        if (spa->spa_l2cache.sav_config) {
                nvlist_free(spa->spa_l2cache.sav_config);
                spa->spa_l2cache.sav_config = NULL;
        }
        spa->spa_l2cache.sav_count = 0;

        spa->spa_async_suspended = 0;

        spa_config_exit(spa, SCL_ALL, FTAG);
}

/*
 * Load (or re-load) the current list of vdevs describing the active spares for
 * this pool.  When this is called, we have some form of basic information in
 * 'spa_spares.sav_config'.  We parse this into vdevs, try to open them, and
 * then re-generate a more complete list including status information.
 */
static void
spa_load_spares(spa_t *spa)
{
        nvlist_t **spares;
        uint_t nspares;
        int i;
        vdev_t *vd, *tvd;

        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);

        /*
         * First, close and free any existing spare vdevs.
         */
        for (i = 0; i < spa->spa_spares.sav_count; i++) {
                vd = spa->spa_spares.sav_vdevs[i];

                /* Undo the call to spa_activate() below */
                if ((tvd = spa_lookup_by_guid(spa, vd->vdev_guid,
                    B_FALSE)) != NULL && tvd->vdev_isspare)
                        spa_spare_remove(tvd);
                vdev_close(vd);
                vdev_free(vd);
        }

        if (spa->spa_spares.sav_vdevs)
                kmem_free(spa->spa_spares.sav_vdevs,
                    spa->spa_spares.sav_count * sizeof (void *));

        if (spa->spa_spares.sav_config == NULL)
                nspares = 0;
        else
                VERIFY(nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
                    ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0);

        spa->spa_spares.sav_count = (int)nspares;
        spa->spa_spares.sav_vdevs = NULL;

        if (nspares == 0)
                return;

        /*
         * Construct the array of vdevs, opening them to get status in the
         * process.   For each spare, there is potentially two different vdev_t
         * structures associated with it: one in the list of spares (used only
         * for basic validation purposes) and one in the active vdev
         * configuration (if it's spared in).  During this phase we open and
         * validate each vdev on the spare list.  If the vdev also exists in the
         * active configuration, then we also mark this vdev as an active spare.
         */
        spa->spa_spares.sav_vdevs = kmem_alloc(nspares * sizeof (void *),
            KM_SLEEP);
        for (i = 0; i < spa->spa_spares.sav_count; i++) {
                VERIFY(spa_config_parse(spa, &vd, spares[i], NULL, 0,
                    VDEV_ALLOC_SPARE) == 0);
                ASSERT(vd != NULL);

                spa->spa_spares.sav_vdevs[i] = vd;

                if ((tvd = spa_lookup_by_guid(spa, vd->vdev_guid,
                    B_FALSE)) != NULL) {
                        if (!tvd->vdev_isspare)
                                spa_spare_add(tvd);

                        /*
                         * We only mark the spare active if we were successfully
                         * able to load the vdev.  Otherwise, importing a pool
                         * with a bad active spare would result in strange
                         * behavior, because multiple pool would think the spare
                         * is actively in use.
                         *
                         * There is a vulnerability here to an equally bizarre
                         * circumstance, where a dead active spare is later
                         * brought back to life (onlined or otherwise).  Given
                         * the rarity of this scenario, and the extra complexity
                         * it adds, we ignore the possibility.
                         */
                        if (!vdev_is_dead(tvd))
                                spa_spare_activate(tvd);
                }

                vd->vdev_top = vd;
                vd->vdev_aux = &spa->spa_spares;

                if (vdev_open(vd) != 0)
                        continue;

                if (vdev_validate_aux(vd) == 0)
                        spa_spare_add(vd);
        }

        /*
         * Recompute the stashed list of spares, with status information
         * this time.
         */
        VERIFY(nvlist_remove(spa->spa_spares.sav_config, ZPOOL_CONFIG_SPARES,
            DATA_TYPE_NVLIST_ARRAY) == 0);

        spares = kmem_alloc(spa->spa_spares.sav_count * sizeof (void *),
            KM_SLEEP);
        for (i = 0; i < spa->spa_spares.sav_count; i++)
                spares[i] = vdev_config_generate(spa,
                    spa->spa_spares.sav_vdevs[i], B_TRUE, 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;
        vdev_t *vd, **oldvdevs, **newvdevs;
        spa_aux_vdev_t *sav = &spa->spa_l2cache;

        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);

        if (sav->sav_config != NULL) {
                VERIFY(nvlist_lookup_nvlist_array(sav->sav_config,
                    ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0);
                newvdevs = kmem_alloc(nl2cache * sizeof (void *), KM_SLEEP);
        } else {
                nl2cache = 0;
        }

        oldvdevs = sav->sav_vdevs;
        oldnvdevs = sav->sav_count;
        sav->sav_vdevs = NULL;
        sav->sav_count = 0;

        /*
         * Process new nvlist of vdevs.
         */
        for (i = 0; i < nl2cache; i++) {
                VERIFY(nvlist_lookup_uint64(l2cache[i], ZPOOL_CONFIG_GUID,
                    &guid) == 0);

                newvdevs[i] = NULL;
                for (j = 0; j < oldnvdevs; j++) {
                        vd = oldvdevs[j];
                        if (vd != NULL && guid == vd->vdev_guid) {
                                /*
                                 * Retain previous vdev for add/remove ops.
                                 */
                                newvdevs[i] = vd;
                                oldvdevs[j] = NULL;
                                break;
                        }
                }

                if (newvdevs[i] == NULL) {
                        /*
                         * Create new vdev
                         */
                        VERIFY(spa_config_parse(spa, &vd, l2cache[i], NULL, 0,
                            VDEV_ALLOC_L2CACHE) == 0);
                        ASSERT(vd != NULL);
                        newvdevs[i] = vd;

                        /*
                         * Commit this vdev as an l2cache device,
                         * even if it fails to open.
                         */
                        spa_l2cache_add(vd);

                        vd->vdev_top = vd;
                        vd->vdev_aux = sav;

                        spa_l2cache_activate(vd);

                        if (vdev_open(vd) != 0)
                                continue;

                        (void) vdev_validate_aux(vd);

                        if (!vdev_is_dead(vd))
                                l2arc_add_vdev(spa, vd);
                }
        }

        /*
         * Purge vdevs that were dropped
         */
        for (i = 0; i < oldnvdevs; i++) {
                uint64_t pool;

                vd = oldvdevs[i];
                if (vd != NULL) {
                        if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
                            pool != 0ULL && l2arc_vdev_present(vd))
                                l2arc_remove_vdev(vd);
                        (void) vdev_close(vd);
                        spa_l2cache_remove(vd);
                }
        }

        if (oldvdevs)
                kmem_free(oldvdevs, oldnvdevs * sizeof (void *));

        if (sav->sav_config == NULL)
                goto out;

        sav->sav_vdevs = newvdevs;
        sav->sav_count = (int)nl2cache;

        /*
         * Recompute the stashed list of l2cache devices, with status
         * information this time.
         */
        VERIFY(nvlist_remove(sav->sav_config, ZPOOL_CONFIG_L2CACHE,
            DATA_TYPE_NVLIST_ARRAY) == 0);

        l2cache = kmem_alloc(sav->sav_count * sizeof (void *), KM_SLEEP);
        for (i = 0; i < sav->sav_count; i++)
                l2cache[i] = vdev_config_generate(spa,
                    sav->sav_vdevs[i], B_TRUE, 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)
{
        for (int c = 0; c < vd->vdev_children; c++)
                spa_check_removed(vd->vdev_child[c]);

        if (vd->vdev_ops->vdev_op_leaf && vdev_is_dead(vd)) {
                zfs_post_autoreplace(vd->vdev_spa, vd);
                spa_event_notify(vd->vdev_spa, vd, ESC_ZFS_VDEV_CHECK);
        }
}

/*
 * Load the slog device state from the config object since it's possible
 * that the label does not contain the most up-to-date information.
 */
void
spa_load_log_state(spa_t *spa, nvlist_t *nv)
{
        vdev_t *ovd, *rvd = spa->spa_root_vdev;

        /*
         * Load the original root vdev tree from the passed config.
         */
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
        VERIFY(spa_config_parse(spa, &ovd, nv, NULL, 0, VDEV_ALLOC_LOAD) == 0);

        for (int c = 0; c < rvd->vdev_children; c++) {
                vdev_t *cvd = rvd->vdev_child[c];
                if (cvd->vdev_islog)
                        vdev_load_log_state(cvd, ovd->vdev_child[c]);
        }
        vdev_free(ovd);
        spa_config_exit(spa, SCL_ALL, FTAG);
}

/*
 * Check for missing log devices
 */
int
spa_check_logs(spa_t *spa)
{
        switch (spa->spa_log_state) {
        case SPA_LOG_MISSING:
                /* need to recheck in case slog has been restored */
        case SPA_LOG_UNKNOWN:
                if (dmu_objset_find(spa->spa_name, zil_check_log_chain, NULL,
                    DS_FIND_CHILDREN)) {
                        spa->spa_log_state = SPA_LOG_MISSING;
                        return (1);
                }
                break;
        }
        return (0);
}

static void
spa_aux_check_removed(spa_aux_vdev_t *sav)
{
        for (int i = 0; i < sav->sav_count; i++)
                spa_check_removed(sav->sav_vdevs[i]);
}

void
spa_claim_notify(zio_t *zio)
{
        spa_t *spa = zio->io_spa;

        if (zio->io_error)
                return;

        mutex_enter(&spa->spa_props_lock);      /* any mutex will do */
        if (spa->spa_claim_max_txg < zio->io_bp->blk_birth)
                spa->spa_claim_max_txg = zio->io_bp->blk_birth;
        mutex_exit(&spa->spa_props_lock);
}

typedef struct spa_load_error {
        uint64_t        sle_metadata_count;
        uint64_t        sle_data_count;
} spa_load_error_t;

static void
spa_load_verify_done(zio_t *zio)
{
        blkptr_t *bp = zio->io_bp;
        spa_load_error_t *sle = zio->io_private;
        dmu_object_type_t type = BP_GET_TYPE(bp);
        int error = zio->io_error;

        if (error) {
                if ((BP_GET_LEVEL(bp) != 0 || dmu_ot[type].ot_metadata) &&
                    type != DMU_OT_INTENT_LOG)
                        atomic_add_64(&sle->sle_metadata_count, 1);
                else
                        atomic_add_64(&sle->sle_data_count, 1);
        }
        zio_data_buf_free(zio->io_data, zio->io_size);
}

/*ARGSUSED*/
static int
spa_load_verify_cb(spa_t *spa, zilog_t *zilog, const blkptr_t *bp,
    const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
{
        if (bp != NULL) {
                zio_t *rio = arg;
                size_t size = BP_GET_PSIZE(bp);
                void *data = zio_data_buf_alloc(size);

                zio_nowait(zio_read(rio, spa, bp, data, size,
                    spa_load_verify_done, rio->io_private, ZIO_PRIORITY_SCRUB,
                    ZIO_FLAG_SPECULATIVE | ZIO_FLAG_CANFAIL |
                    ZIO_FLAG_SCRUB | ZIO_FLAG_RAW, zb));
        }
        return (0);
}

static int
spa_load_verify(spa_t *spa)
{
        zio_t *rio;
        spa_load_error_t sle = { 0 };
        zpool_rewind_policy_t policy;
        boolean_t verify_ok = B_FALSE;
        int error;

        rio = zio_root(spa, NULL, &sle,
            ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE);

        error = traverse_pool(spa, spa_load_verify_cb, rio,
            spa->spa_verify_min_txg);

        (void) zio_wait(rio);

        zpool_get_rewind_policy(spa->spa_config, &policy);

        spa->spa_load_meta_errors = sle.sle_metadata_count;
        spa->spa_load_data_errors = sle.sle_data_count;

        if (!error && sle.sle_metadata_count <= policy.zrp_maxmeta &&
            sle.sle_data_count <= policy.zrp_maxdata) {
                verify_ok = B_TRUE;
                spa->spa_load_txg = spa->spa_uberblock.ub_txg;
                spa->spa_load_txg_ts = spa->spa_uberblock.ub_timestamp;
        }

        if (error) {
                if (error != ENXIO && error != EIO)
                        error = EIO;
                return (error);
        }

        return (verify_ok ? 0 : EIO);
}

/*
 * 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, spa_load_state_t state, int mosconfig)
{
        int error = 0;
        nvlist_t *nvconfig, *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;
        nvlist_t *config = spa->spa_config;

        /*
         * 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) {
                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) {
                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) {
                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_verify_min_txg = spa->spa_extreme_rewind ?
            TXG_INITIAL : spa_last_synced_txg(spa) - TXG_DEFER_SIZE;
        spa->spa_first_txg = spa->spa_last_ubsync_txg ?
            spa->spa_last_ubsync_txg : spa_last_synced_txg(spa) + 1;
        spa->spa_claim_max_txg = spa->spa_first_txg;

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

        if (!mosconfig) {
                uint64_t hostid;

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

                        VERIFY(nvlist_lookup_string(nvconfig,
                            ZPOOL_CONFIG_HOSTNAME, &hostname) == 0);

#ifdef  _KERNEL
                        myhostid = zone_get_hostid(NULL);
#else   /* _KERNEL */
                        /*
                         * We're emulating the system's hostid in userland, so
                         * we can't use zone_get_hostid().
                         */
                        (void) ddi_strtoul(hw_serial, NULL, 10, &myhostid);
#endif  /* _KERNEL */
                        if (hostid != 0 && myhostid != 0 &&
                            hostid != myhostid) {
                                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, nvconfig);
                spa_unload(spa);
                spa_deactivate(spa);
                spa_activate(spa, orig_mode);

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

        if (zap_lookup(spa->spa_meta_objset,
            DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_SYNC_BPLIST,
            sizeof (uint64_t), 1, &spa->spa_deferred_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->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);
                spa->spa_autoreplace = (autoreplace != 0);
                (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);
                (void) zap_lookup(spa->spa_meta_objset,
                    spa->spa_pool_props_object,
                    zpool_prop_to_name(ZPOOL_PROP_AUTOEXPAND),
                    sizeof (uint64_t), 1, &spa->spa_autoexpand);
                (void) zap_lookup(spa->spa_meta_objset,
                    spa->spa_pool_props_object,
                    zpool_prop_to_name(ZPOOL_PROP_DEDUPDITTO),
                    sizeof (uint64_t), 1, &spa->spa_dedup_ditto);
        }

        /*
         * If the 'autoreplace' property is set, then post a resource notifying
         * the ZFS DE that it should not issue any faults for unopenable
         * devices.  We also iterate over the vdevs, and post a sysevent for any
         * unopenable vdevs so that the normal autoreplace handler can take
         * over.
         */
        if (spa->spa_autoreplace && state != SPA_LOAD_TRYIMPORT) {
                spa_check_removed(spa->spa_root_vdev);
                /*
                 * For the import case, this is done in spa_import(), because
                 * at this point we're using the spare definitions from
                 * the MOS config, not necessarily from the userland config.
                 */
                if (state != SPA_LOAD_IMPORT) {
                        spa_aux_check_removed(&spa->spa_spares);
                        spa_aux_check_removed(&spa->spa_l2cache);
                }
        }

        /*
         * Load the vdev state for all toplevel vdevs.
         */
        vdev_load(rvd);

        /*
         * Propagate the leaf DTLs we just loaded all the way up the tree.
         */
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
        vdev_dtl_reassess(rvd, 0, 0, B_FALSE);
        spa_config_exit(spa, SCL_ALL, FTAG);

        /*
         * Check the state of the root vdev.  If it can't be opened, it
         * indicates one or more toplevel vdevs are faulted.
         */
        if (rvd->vdev_state <= VDEV_STATE_CANT_OPEN) {
                error = ENXIO;
                goto out;
        }

        /*
         * Load the DDTs (dedup tables).
         */
        error = ddt_load(spa);
        if (error != 0) {
                vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                    VDEV_AUX_CORRUPT_DATA);
                error = EIO;
                goto out;
        }

        spa_update_dspace(spa);

        if (state != SPA_LOAD_TRYIMPORT) {
                error = spa_load_verify(spa);
                if (error) {
                        vdev_set_state(rvd, B_TRUE, VDEV_STATE_CANT_OPEN,
                            VDEV_AUX_CORRUPT_DATA);
                        goto out;
                }
        }

        /*
         * Load the intent log state and check log integrity.
         */
        VERIFY(nvlist_lookup_nvlist(nvconfig, ZPOOL_CONFIG_VDEV_TREE,
            &nvroot) == 0);
        spa_load_log_state(spa, nvroot);
        nvlist_free(nvconfig);

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

        if (spa_writeable(spa) && (state == SPA_LOAD_RECOVER ||
            spa->spa_load_max_txg == UINT64_MAX)) {
                dmu_tx_t *tx;
                int need_update = B_FALSE;

                ASSERT(state != SPA_LOAD_TRYIMPORT);

                /*
                 * Claim log blocks that haven't been committed yet.
                 * This must all happen in a single txg.
                 * Note: spa_claim_max_txg is updated by spa_claim_notify(),
                 * invoked from zil_claim_log_block()'s i/o done callback.
                 * Price of rollback is that we abandon the log.
                 */
                spa->spa_claiming = B_TRUE;

                tx = dmu_tx_create_assigned(spa_get_dsl(spa),
                    spa_first_txg(spa));
                (void) dmu_objset_find(spa_name(spa),
                    zil_claim, tx, DS_FIND_CHILDREN);
                dmu_tx_commit(tx);

                spa->spa_claiming = B_FALSE;

                spa->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.  We sync up to the highest
                 * claimed log block birth time so that claimed log blocks
                 * don't appear to be from the future.  spa_claim_max_txg
                 * will have been set for us by either zil_check_log_chain()
                 * (invoked from spa_check_logs()) or zil_claim() above.
                 */
                txg_wait_synced(spa->spa_dsl_pool, spa->spa_claim_max_txg);

                /*
                 * If the config cache is stale, or we have uninitialized
                 * metaslabs (see spa_vdev_add()), then update the config.
                 *
                 * If spa_load_verbatim is true, trust the current
                 * in-core spa_config and update the disk labels.
                 */
                if (config_cache_txg != spa->spa_config_txg ||
                    state == SPA_LOAD_IMPORT || spa->spa_load_verbatim ||
                    state == SPA_LOAD_RECOVER)
                        need_update = B_TRUE;

                for (int c = 0; c < rvd->vdev_children; c++)
                        if (rvd->vdev_child[c]->vdev_ms_array == 0)
                                need_update = B_TRUE;

                /*
                 * Update the config cache asychronously in case we're the
                 * root pool, in which case the config cache isn't writable yet.
                 */
                if (need_update)
                        spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE);

                /*
                 * Check all DTLs to see if anything needs resilvering.
                 */
                if (vdev_resilver_needed(rvd, NULL, NULL))
                        spa_async_request(spa, SPA_ASYNC_RESILVER);

                /*
                 * Delete any inconsistent datasets.
                 */
                (void) dmu_objset_find(spa_name(spa),
                    dsl_destroy_inconsistent, NULL, DS_FIND_CHILDREN);

                /*
                 * Clean up any stale temporary dataset userrefs.
                 */
                dsl_pool_clean_tmp_userrefs(spa->spa_dsl_pool);
        }

        error = 0;
out:

        spa->spa_minref = refcount_count(&spa->spa_refcount);
        if (error && error != EBADF)
                zfs_ereport_post(ereport, spa, NULL, NULL, 0, 0);
        spa->spa_load_state = SPA_LOAD_NONE;
        spa->spa_ena = 0;

        return (error);
}

static int
spa_load_retry(spa_t *spa, spa_load_state_t state, int mosconfig)
{
        spa_unload(spa);
        spa_deactivate(spa);

        spa->spa_load_max_txg--;

        spa_activate(spa, spa_mode_global);
        spa_async_suspend(spa);

        return (spa_load(spa, state, mosconfig));
}

static int
spa_load_best(spa_t *spa, spa_load_state_t state, int mosconfig,
    uint64_t max_request, boolean_t extreme)
{
        nvlist_t *config = NULL;
        int load_error, rewind_error;
        uint64_t safe_rollback_txg;
        uint64_t min_txg;

        if (spa->spa_load_txg && state == SPA_LOAD_RECOVER)
                spa->spa_load_max_txg = spa->spa_load_txg;
        else
                spa->spa_load_max_txg = max_request;

        load_error = rewind_error = spa_load(spa, state, mosconfig);
        if (load_error == 0)
                return (0);

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

        spa->spa_last_ubsync_txg = spa->spa_uberblock.ub_txg;
        spa->spa_last_ubsync_txg_ts = spa->spa_uberblock.ub_timestamp;

        /* specific txg requested */
        if (spa->spa_load_max_txg != UINT64_MAX && !extreme) {
                nvlist_free(config);
                return (load_error);
        }

        /* Price of rolling back is discarding txgs, including log */
        if (state == SPA_LOAD_RECOVER)
                spa->spa_log_state = SPA_LOG_CLEAR;

        spa->spa_load_max_txg = spa->spa_uberblock.ub_txg;
        safe_rollback_txg = spa->spa_uberblock.ub_txg - TXG_DEFER_SIZE;

        min_txg = extreme ? TXG_INITIAL : safe_rollback_txg;
        while (rewind_error && (spa->spa_uberblock.ub_txg >= min_txg)) {
                if (spa->spa_load_max_txg < safe_rollback_txg)
                        spa->spa_extreme_rewind = B_TRUE;
                rewind_error = spa_load_retry(spa, state, mosconfig);
        }

        if (config)
                spa_rewind_data_to_nvlist(spa, config);

        spa->spa_extreme_rewind = B_FALSE;
        spa->spa_load_max_txg = UINT64_MAX;

        if (config && (rewind_error || state != SPA_LOAD_RECOVER))
                spa_config_set(spa, config);

        return (state == SPA_LOAD_RECOVER ? rewind_error : load_error);
}

/*
 * Pool Open/Import
 *
 * The import case is identical to an open except that the configuration is sent
 * down from userland, instead of grabbed from the configuration cache.  For the
 * case of an open, the pool configuration will exist in the
 * POOL_STATE_UNINITIALIZED state.
 *
 * The stats information (gen/count/ustats) is used to gather vdev statistics at
 * the same time open the pool, without having to keep around the spa_t in some
 * ambiguous state.
 */
static int
spa_open_common(const char *pool, spa_t **spapp, void *tag, nvlist_t *nvpolicy,
    nvlist_t **config)
{
        spa_t *spa;
        boolean_t norewind;
        boolean_t extreme;
        zpool_rewind_policy_t policy;
        spa_load_state_t state = SPA_LOAD_OPEN;
        int error;
        int locked = B_FALSE;

        *spapp = NULL;

        zpool_get_rewind_policy(nvpolicy, &policy);
        if (policy.zrp_request & ZPOOL_DO_REWIND)
                state = SPA_LOAD_RECOVER;
        norewind = (policy.zrp_request == ZPOOL_NO_REWIND);
        extreme = ((policy.zrp_request & ZPOOL_EXTREME_REWIND) != 0);

        /*
         * 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);

                if (spa->spa_last_open_failed && norewind) {
                        if (config != NULL && spa->spa_config)
                                VERIFY(nvlist_dup(spa->spa_config,
                                    config, KM_SLEEP) == 0);
                        spa_deactivate(spa);
                        if (locked)
                                mutex_exit(&spa_namespace_lock);
                        return (spa->spa_last_open_failed);
                }

                if (state != SPA_LOAD_RECOVER)
                        spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;

                error = spa_load_best(spa, state, B_FALSE, policy.zrp_txg,
                    extreme);

                if (error == EBADF) {
                        /*
                         * If vdev_validate() returns failure (indicated by
                         * EBADF), it indicates that one of the vdevs indicates
                         * that the pool has been exported or destroyed.  If
                         * this is the case, the config cache is out of sync and
                         * we should remove the pool from the namespace.
                         */
                        spa_unload(spa);
                        spa_deactivate(spa);
                        spa_config_sync(spa, B_TRUE, B_TRUE);
                        spa_remove(spa);
                        if (locked)
                                mutex_exit(&spa_namespace_lock);
                        return (ENOENT);
                }

                if (error) {
                        /*
                         * We can't open the pool, but we still have useful
                         * information: the state of each vdev after the
                         * attempted vdev_open().  Return this to the user.
                         */
                        if (config != NULL && spa->spa_config)
                                VERIFY(nvlist_dup(spa->spa_config, config,
                                    KM_SLEEP) == 0);
                        spa_unload(spa);
                        spa_deactivate(spa);
                        spa->spa_last_open_failed = error;
                        if (locked)
                                mutex_exit(&spa_namespace_lock);
                        *spapp = NULL;
                        return (error);
                }

        }

        spa_open_ref(spa, tag);

        spa->spa_last_open_failed = 0;

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

        spa->spa_last_ubsync_txg = 0;
        spa->spa_load_txg = 0;

        if (locked)
                mutex_exit(&spa_namespace_lock);

        *spapp = spa;

        return (0);
}

int
spa_open_rewind(const char *name, spa_t **spapp, void *tag, nvlist_t *policy,
    nvlist_t **config)
{
        return (spa_open_common(name, spapp, tag, policy, config));
}

int
spa_open(const char *name, spa_t **spapp, void *tag)
{
        return (spa_open_common(name, spapp, tag, NULL, NULL));
}

/*
 * Lookup the given spa_t, incrementing the inject count in the process,
 * preventing it from being exported or destroyed.
 */
spa_t *
spa_inject_addref(char *name)
{
        spa_t *spa;

        mutex_enter(&spa_namespace_lock);
        if ((spa = spa_lookup(name)) == NULL) {
                mutex_exit(&spa_namespace_lock);
                return (NULL);
        }
        spa->spa_inject_ref++;
        mutex_exit(&spa_namespace_lock);

        return (spa);
}

void
spa_inject_delref(spa_t *spa)
{
        mutex_enter(&spa_namespace_lock);
        spa->spa_inject_ref--;
        mutex_exit(&spa_namespace_lock);
}

/*
 * Add spares device information to the nvlist.
 */
static void
spa_add_spares(spa_t *spa, nvlist_t *config)
{
        nvlist_t **spares;
        uint_t i, nspares;
        nvlist_t *nvroot;
        uint64_t guid;
        vdev_stat_t *vs;
        uint_t vsc;
        uint64_t pool;

        ASSERT(spa_config_held(spa, SCL_CONFIG, RW_READER));

        if (spa->spa_spares.sav_count == 0)
                return;

        VERIFY(nvlist_lookup_nvlist(config,
            ZPOOL_CONFIG_VDEV_TREE, &nvroot) == 0);
        VERIFY(nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
            ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0);
        if (nspares != 0) {
                VERIFY(nvlist_add_nvlist_array(nvroot,
                    ZPOOL_CONFIG_SPARES, spares, nspares) == 0);
                VERIFY(nvlist_lookup_nvlist_array(nvroot,
                    ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0);

                /*
                 * Go through and find any spares which have since been
                 * repurposed as an active spare.  If this is the case, update
                 * their status appropriately.
                 */
                for (i = 0; i < nspares; i++) {
                        VERIFY(nvlist_lookup_uint64(spares[i],
                            ZPOOL_CONFIG_GUID, &guid) == 0);
                        if (spa_spare_exists(guid, &pool, NULL) &&
                            pool != 0ULL) {
                                VERIFY(nvlist_lookup_uint64_array(
                                    spares[i], ZPOOL_CONFIG_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, NULL, config);

        if (spa != NULL) {
                /*
                 * This still leaves a window of inconsistency where the spares
                 * or l2cache devices could change and the config would be
                 * self-inconsistent.
                 */
                spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

                if (*config != NULL) {
                        VERIFY(nvlist_add_uint64(*config,
                            ZPOOL_CONFIG_ERRCOUNT,
                            spa_get_errlog_size(spa)) == 0);

                        if (spa_suspended(spa))
                                VERIFY(nvlist_add_uint64(*config,
                                    ZPOOL_CONFIG_SUSPENDED,
                                    spa->spa_failmode) == 0);

                        spa_add_spares(spa, *config);
                        spa_add_l2cache(spa, *config);
                }
        }

        /*
         * We want to get the alternate root even for faulted pools, so we cheat
         * and call spa_lookup() directly.
         */
        if (altroot) {
                if (spa == NULL) {
                        mutex_enter(&spa_namespace_lock);
                        spa = spa_lookup(name);
                        if (spa)
                                spa_altroot(spa, altroot, buflen);
                        else
                                altroot[0] = '\0';
                        spa = NULL;
                        mutex_exit(&spa_namespace_lock);
                } else {
                        spa_altroot(spa, altroot, buflen);
                }
        }

        if (spa != NULL) {
                spa_config_exit(spa, SCL_CONFIG, FTAG);
                spa_close(spa, FTAG);
        }

        return (error);
}

/*
 * Validate that the auxiliary device array is well formed.  We must have an
 * array of nvlists, each which describes a valid leaf vdev.  If this is an
 * import (mode is VDEV_ALLOC_SPARE), then we allow corrupted spares to be
 * specified, as long as they are well-formed.
 */
static int
spa_validate_aux_devs(spa_t *spa, nvlist_t *nvroot, uint64_t crtxg, int mode,
    spa_aux_vdev_t *sav, const char *config, uint64_t version,
    vdev_labeltype_t label)
{
        nvlist_t **dev;
        uint_t i, ndev;
        vdev_t *vd;
        int error;

        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);

        /*
         * It's acceptable to have no devs specified.
         */
        if (nvlist_lookup_nvlist_array(nvroot, config, &dev, &ndev) != 0)
                return (0);

        if (ndev == 0)
                return (EINVAL);

        /*
         * Make sure the pool is formatted with a version that supports this
         * device type.
         */
        if (spa_version(spa) < version)
                return (ENOTSUP);

        /*
         * Set the pending device list so we correctly handle device in-use
         * checking.
         */
        sav->sav_pending = dev;
        sav->sav_npending = ndev;

        for (i = 0; i < ndev; i++) {
                if ((error = spa_config_parse(spa, &vd, dev[i], NULL, 0,
                    mode)) != 0)
                        goto out;

                if (!vd->vdev_ops->vdev_op_leaf) {
                        vdev_free(vd);
                        error = EINVAL;
                        goto out;
                }

                /*
                 * The L2ARC currently only supports disk devices in
                 * kernel context.  For user-level testing, we allow it.
                 */
#ifdef _KERNEL
                if ((strcmp(config, ZPOOL_CONFIG_L2CACHE) == 0) &&
                    strcmp(vd->vdev_ops->vdev_op_type, VDEV_TYPE_DISK) != 0) {
                        error = ENOTBLK;
                        goto out;
                }
#endif
                vd->vdev_top = vd;

                if ((error = vdev_open(vd)) == 0 &&
                    (error = vdev_label_init(vd, crtxg, label)) == 0) {
                        VERIFY(nvlist_add_uint64(dev[i], ZPOOL_CONFIG_GUID,
                            vd->vdev_guid) == 0);
                }

                vdev_free(vd);

                if (error &&
                    (mode != VDEV_ALLOC_SPARE && mode != VDEV_ALLOC_L2CACHE))
                        goto out;
                else
                        error = 0;
        }

out:
        sav->sav_pending = NULL;
        sav->sav_npending = 0;
        return (error);
}

static int
spa_validate_aux(spa_t *spa, nvlist_t *nvroot, uint64_t crtxg, int mode)
{
        int error;

        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);

        if ((error = spa_validate_aux_devs(spa, nvroot, crtxg, mode,
            &spa->spa_spares, ZPOOL_CONFIG_SPARES, SPA_VERSION_SPARES,
            VDEV_LABEL_SPARE)) != 0) {
                return (error);
        }

        return (spa_validate_aux_devs(spa, nvroot, crtxg, mode,
            &spa->spa_l2cache, ZPOOL_CONFIG_L2CACHE, SPA_VERSION_L2CACHE,
            VDEV_LABEL_L2CACHE));
}

static void
spa_set_aux_vdevs(spa_aux_vdev_t *sav, nvlist_t **devs, int ndevs,
    const char *config)
{
        int i;

        if (sav->sav_config != NULL) {
                nvlist_t **olddevs;
                uint_t oldndevs;
                nvlist_t **newdevs;

                /*
                 * Generate new dev list by concatentating with the
                 * current dev list.
                 */
                VERIFY(nvlist_lookup_nvlist_array(sav->sav_config, config,
                    &olddevs, &oldndevs) == 0);

                newdevs = kmem_alloc(sizeof (void *) *
                    (ndevs + oldndevs), KM_SLEEP);
                for (i = 0; i < oldndevs; i++)
                        VERIFY(nvlist_dup(olddevs[i], &newdevs[i],
                            KM_SLEEP) == 0);
                for (i = 0; i < ndevs; i++)
                        VERIFY(nvlist_dup(devs[i], &newdevs[i + oldndevs],
                            KM_SLEEP) == 0);

                VERIFY(nvlist_remove(sav->sav_config, config,
                    DATA_TYPE_NVLIST_ARRAY) == 0);

                VERIFY(nvlist_add_nvlist_array(sav->sav_config,
                    config, newdevs, ndevs + oldndevs) == 0);
                for (i = 0; i < oldndevs + ndevs; i++)
                        nvlist_free(newdevs[i]);
                kmem_free(newdevs, (oldndevs + ndevs) * sizeof (void *));
        } else {
                /*
                 * Generate a new dev list.
                 */
                VERIFY(nvlist_alloc(&sav->sav_config, NV_UNIQUE_NAME,
                    KM_SLEEP) == 0);
                VERIFY(nvlist_add_nvlist_array(sav->sav_config, config,
                    devs, ndevs) == 0);
        }
}

/*
 * Stop and drop level 2 ARC devices
 */
void
spa_l2cache_drop(spa_t *spa)
{
        vdev_t *vd;
        int i;
        spa_aux_vdev_t *sav = &spa->spa_l2cache;

        for (i = 0; i < sav->sav_count; i++) {
                uint64_t pool;

                vd = sav->sav_vdevs[i];
                ASSERT(vd != NULL);

                if (spa_l2cache_exists(vd->vdev_guid, &pool) &&
                    pool != 0ULL && l2arc_vdev_present(vd))
                        l2arc_remove_vdev(vd);
                if (vd->vdev_isl2cache)
                        spa_l2cache_remove(vd);
                vdev_clear_stats(vd);
                (void) vdev_close(vd);
        }
}

/*
 * Pool Creation
 */
int
spa_create(const char *pool, nvlist_t *nvroot, nvlist_t *props,
    const char *history_str, nvlist_t *zplprops)
{
        spa_t *spa;
        char *altroot = NULL;
        vdev_t *rvd;
        dsl_pool_t *dp;
        dmu_tx_t *tx;
        int error = 0;
        uint64_t txg = TXG_INITIAL;
        nvlist_t **spares, **l2cache;
        uint_t nspares, nl2cache;
        uint64_t version;

        /*
         * If this pool already exists, return failure.
         */
        mutex_enter(&spa_namespace_lock);
        if (spa_lookup(pool) != NULL) {
                mutex_exit(&spa_namespace_lock);
                return (EEXIST);
        }

        /*
         * Allocate a new spa_t structure.
         */
        (void) nvlist_lookup_string(props,
            zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
        spa = spa_add(pool, NULL, altroot);
        spa_activate(spa, spa_mode_global);

        if (props && (error = spa_prop_validate(spa, props))) {
                spa_deactivate(spa);
                spa_remove(spa);
                mutex_exit(&spa_namespace_lock);
                return (error);
        }

        if (nvlist_lookup_uint64(props, zpool_prop_to_name(ZPOOL_PROP_VERSION),
            &version) != 0)
                version = SPA_VERSION;
        ASSERT(version <= SPA_VERSION);

        spa->spa_first_txg = txg;
        spa->spa_uberblock.ub_txg = txg - 1;
        spa->spa_uberblock.ub_version = version;
        spa->spa_ubsync = spa->spa_uberblock;

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

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

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

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

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

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

        spa_config_exit(spa, SCL_ALL, FTAG);

        if (error != 0) {
                spa_unload(spa);
                spa_deactivate(spa);
                spa_remove(spa);
                mutex_exit(&spa_namespace_lock);
                return (error);
        }

        /*
         * Get the list of spares, if specified.
         */
        if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES,
            &spares, &nspares) == 0) {
                VERIFY(nvlist_alloc(&spa->spa_spares.sav_config, NV_UNIQUE_NAME,
                    KM_SLEEP) == 0);
                VERIFY(nvlist_add_nvlist_array(spa->spa_spares.sav_config,
                    ZPOOL_CONFIG_SPARES, spares, nspares) == 0);
                spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
                spa_load_spares(spa);
                spa_config_exit(spa, SCL_ALL, FTAG);
                spa->spa_spares.sav_sync = B_TRUE;
        }

        /*
         * Get the list of level 2 cache devices, if specified.
         */
        if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_L2CACHE,
            &l2cache, &nl2cache) == 0) {
                VERIFY(nvlist_alloc(&spa->spa_l2cache.sav_config,
                    NV_UNIQUE_NAME, KM_SLEEP) == 0);
                VERIFY(nvlist_add_nvlist_array(spa->spa_l2cache.sav_config,
                    ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache) == 0);
                spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
                spa_load_l2cache(spa);
                spa_config_exit(spa, SCL_ALL, FTAG);
                spa->spa_l2cache.sav_sync = B_TRUE;
        }

        spa->spa_dsl_pool = dp = dsl_pool_create(spa, zplprops, txg);
        spa->spa_meta_objset = dp->dp_meta_objset;

        /*
         * Create DDTs (dedup tables).
         */
        ddt_create(spa);

        spa_update_dspace(spa);

        tx = dmu_tx_create_assigned(dp, txg);

        /*
         * Create the pool config object.
         */
        spa->spa_config_object = dmu_object_alloc(spa->spa_meta_objset,
            DMU_OT_PACKED_NVLIST, SPA_CONFIG_BLOCKSIZE,
            DMU_OT_PACKED_NVLIST_SIZE, sizeof (uint64_t), tx);

        if (zap_add(spa->spa_meta_objset,
            DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_CONFIG,
            sizeof (uint64_t), 1, &spa->spa_config_object, tx) != 0) {
                cmn_err(CE_PANIC, "failed to add pool config");
        }

        /* Newly created pools with the right version are always deflated. */
        if (version >= SPA_VERSION_RAIDZ_DEFLATE) {
                spa->spa_deflate = TRUE;
                if (zap_add(spa->spa_meta_objset,
                    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
                    sizeof (uint64_t), 1, &spa->spa_deflate, tx) != 0) {
                        cmn_err(CE_PANIC, "failed to add deflate");
                }
        }

        /*
         * Create the deferred-free bplist object.  Turn off compression
         * because sync-to-convergence takes longer if the blocksize
         * keeps changing.
         */
        spa->spa_deferred_bplist_obj = bplist_create(spa->spa_meta_objset,
            1 << 14, tx);
        dmu_object_set_compress(spa->spa_meta_objset,
            spa->spa_deferred_bplist_obj, ZIO_COMPRESS_OFF, tx);

        if (zap_add(spa->spa_meta_objset,
            DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_SYNC_BPLIST,
            sizeof (uint64_t), 1, &spa->spa_deferred_bplist_obj, tx) != 0) {
                cmn_err(CE_PANIC, "failed to add bplist");
        }

        /*
         * Create the pool's history object.
         */
        if (version >= SPA_VERSION_ZPOOL_HISTORY)
                spa_history_create_obj(spa, tx);

        /*
         * Set pool properties.
         */
        spa->spa_bootfs = zpool_prop_default_numeric(ZPOOL_PROP_BOOTFS);
        spa->spa_delegation = zpool_prop_default_numeric(ZPOOL_PROP_DELEGATION);
        spa->spa_failmode = zpool_prop_default_numeric(ZPOOL_PROP_FAILUREMODE);
        spa->spa_autoexpand = zpool_prop_default_numeric(ZPOOL_PROP_AUTOEXPAND);

        if (props != NULL) {
                spa_configfile_set(spa, props, B_FALSE);
                spa_sync_props(spa, props, 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_history_log_version(spa, LOG_POOL_CREATE);

        spa->spa_minref = refcount_count(&spa->spa_refcount);

        mutex_exit(&spa_namespace_lock);

        return (0);
}

#ifdef _KERNEL
/*
 * Get the root pool information from the root disk, then import the root pool
 * during the system boot up time.
 */
extern int vdev_disk_read_rootlabel(char *, char *, nvlist_t **);

static nvlist_t *
spa_generate_rootconf(char *devpath, char *devid, uint64_t *guid)
{
        nvlist_t *config;
        nvlist_t *nvtop, *nvroot;
        uint64_t pgid;

        if (vdev_disk_read_rootlabel(devpath, devid, &config) != 0)
                return (NULL);

        /*
         * Add this top-level vdev to the child array.
         */
        VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
            &nvtop) == 0);
        VERIFY(nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_GUID,
            &pgid) == 0);
        VERIFY(nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID, guid) == 0);

        /*
         * Put this pool's top-level vdevs into a root vdev.
         */
        VERIFY(nvlist_alloc(&nvroot, NV_UNIQUE_NAME, KM_SLEEP) == 0);
        VERIFY(nvlist_add_string(nvroot, ZPOOL_CONFIG_TYPE,
            VDEV_TYPE_ROOT) == 0);
        VERIFY(nvlist_add_uint64(nvroot, ZPOOL_CONFIG_ID, 0ULL) == 0);
        VERIFY(nvlist_add_uint64(nvroot, ZPOOL_CONFIG_GUID, pgid) == 0);
        VERIFY(nvlist_add_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
            &nvtop, 1) == 0);

        /*
         * Replace the existing vdev_tree with the new root vdev in
         * this pool's configuration (remove the old, add the new).
         */
        VERIFY(nvlist_add_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, nvroot) == 0);
        nvlist_free(nvroot);
        return (config);
}

/*
 * Walk the vdev tree and see if we can find a device with "better"
 * configuration. A configuration is "better" if the label on that
 * device has a more recent txg.
 */
static void
spa_alt_rootvdev(vdev_t *vd, vdev_t **avd, uint64_t *txg)
{
        for (int c = 0; c < vd->vdev_children; c++)
                spa_alt_rootvdev(vd->vdev_child[c], avd, txg);

        if (vd->vdev_ops->vdev_op_leaf) {
                nvlist_t *label;
                uint64_t label_txg;

                if (vdev_disk_read_rootlabel(vd->vdev_physpath, vd->vdev_devid,
                    &label) != 0)
                        return;

                VERIFY(nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_TXG,
                    &label_txg) == 0);

                /*
                 * Do we have a better boot device?
                 */
                if (label_txg > *txg) {
                        *txg = label_txg;
                        *avd = vd;
                }
                nvlist_free(label);
        }
}

/*
 * Import a root pool.
 *
 * For x86. devpath_list will consist of devid and/or physpath name of
 * the vdev (e.g. "id1,sd@SSEAGATE..." or "/pci@1f,0/ide@d/disk@0,0:a").
 * The GRUB "findroot" command will return the vdev we should boot.
 *
 * For Sparc, devpath_list consists the physpath name of the booting device
 * no matter the rootpool is a single device pool or a mirrored pool.
 * e.g.
 *      "/pci@1f,0/ide@d/disk@0,0:a"
 */
int
spa_import_rootpool(char *devpath, char *devid)
{
        spa_t *spa;
        vdev_t *rvd, *bvd, *avd = NULL;
        nvlist_t *config, *nvtop;
        uint64_t guid, txg;
        char *pname;
        int error;

        /*
         * Read the label from the boot device and generate a configuration.
         */
        config = spa_generate_rootconf(devpath, devid, &guid);
#if defined(_OBP) && defined(_KERNEL)
        if (config == NULL) {
                if (strstr(devpath, "/iscsi/ssd") != NULL) {
                        /* iscsi boot */
                        get_iscsi_bootpath_phy(devpath);
                        config = spa_generate_rootconf(devpath, devid, &guid);
                }
        }
#endif
        if (config == NULL) {
                cmn_err(CE_NOTE, "Can not read the pool label from '%s'",
                    devpath);
                return (EIO);
        }

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

        mutex_enter(&spa_namespace_lock);
        if ((spa = spa_lookup(pname)) != NULL) {
                /*
                 * Remove the existing root pool from the namespace so that we
                 * can replace it with the correct config we just read in.
                 */
                spa_remove(spa);
        }

        spa = spa_add(pname, config, NULL);
        spa->spa_is_root = B_TRUE;
        spa->spa_load_verbatim = B_TRUE;

        /*
         * Build up a vdev tree based on the boot device's label config.
         */
        VERIFY(nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE,
            &nvtop) == 0);
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
        error = spa_config_parse(spa, &rvd, nvtop, NULL, 0,
            VDEV_ALLOC_ROOTPOOL);
        spa_config_exit(spa, SCL_ALL, FTAG);
        if (error) {
                mutex_exit(&spa_namespace_lock);
                nvlist_free(config);
                cmn_err(CE_NOTE, "Can not parse the config for pool '%s'",
                    pname);
                return (error);
        }

        /*
         * Get the boot vdev.
         */
        if ((bvd = vdev_lookup_by_guid(rvd, guid)) == NULL) {
                cmn_err(CE_NOTE, "Can not find the boot vdev for guid %llu",
                    (u_longlong_t)guid);
                error = ENOENT;
                goto out;
        }

        /*
         * Determine if there is a better boot device.
         */
        avd = bvd;
        spa_alt_rootvdev(rvd, &avd, &txg);
        if (avd != bvd) {
                cmn_err(CE_NOTE, "The boot device is 'degraded'. Please "
                    "try booting from '%s'", avd->vdev_path);
                error = EINVAL;
                goto out;
        }

        /*
         * If the boot device is part of a spare vdev then ensure that
         * we're booting off the active spare.
         */
        if (bvd->vdev_parent->vdev_ops == &vdev_spare_ops &&
            !bvd->vdev_isspare) {
                cmn_err(CE_NOTE, "The boot device is currently spared. Please "
                    "try booting from '%s'",
                    bvd->vdev_parent->vdev_child[1]->vdev_path);
                error = EINVAL;
                goto out;
        }

        error = 0;
        spa_history_log_version(spa, LOG_POOL_IMPORT);
out:
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
        vdev_free(rvd);
        spa_config_exit(spa, SCL_ALL, FTAG);
        mutex_exit(&spa_namespace_lock);

        nvlist_free(config);
        return (error);
}

#endif

/*
 * Take a pool and insert it into the namespace as if it had been loaded at
 * boot.
 */
int
spa_import_verbatim(const char *pool, nvlist_t *config, nvlist_t *props)
{
        spa_t *spa;
        zpool_rewind_policy_t policy;
        char *altroot = NULL;

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

        (void) nvlist_lookup_string(props,
            zpool_prop_to_name(ZPOOL_PROP_ALTROOT), &altroot);
        spa = spa_add(pool, config, altroot);

        zpool_get_rewind_policy(config, &policy);
        spa->spa_load_max_txg = policy.zrp_txg;

        spa->spa_load_verbatim = B_TRUE;

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

        spa_config_sync(spa, B_FALSE, B_TRUE);

        mutex_exit(&spa_namespace_lock);
        spa_history_log_version(spa, LOG_POOL_IMPORT);

        return (0);
}

/*
 * Import a non-root pool into the system.
 */
int
spa_import(const char *pool, nvlist_t *config, nvlist_t *props)
{
        spa_t *spa;
        char *altroot = NULL;
        spa_load_state_t state = SPA_LOAD_IMPORT;
        zpool_rewind_policy_t policy;
        int error;
        nvlist_t *nvroot;
        nvlist_t **spares, **l2cache;
        uint_t nspares, nl2cache;

        /*
         * If a pool with this name exists, return failure.
         */
        mutex_enter(&spa_namespace_lock);
        if ((spa = spa_lookup(pool)) != NULL) {
                mutex_exit(&spa_namespace_lock);
                return (EEXIST);
        }

        zpool_get_rewind_policy(config, &policy);
        if (policy.zrp_request & ZPOOL_DO_REWIND)
                state = SPA_LOAD_RECOVER;

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

        /*
         * Don't start async tasks until we know everything is healthy.
         */
        spa_async_suspend(spa);

        /*
         * Pass off the heavy lifting to spa_load().  Pass TRUE for mosconfig
         * because the user-supplied config is actually the one to trust when
         * doing an import.
         */
        if (state != SPA_LOAD_RECOVER)
                spa->spa_last_ubsync_txg = spa->spa_load_txg = 0;
        error = spa_load_best(spa, state, B_TRUE, policy.zrp_txg,
            ((policy.zrp_request & ZPOOL_EXTREME_REWIND) != 0));

        /*
         * Propagate anything learned about failing or best txgs
         * back to caller
         */
        spa_rewind_data_to_nvlist(spa, config);

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

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

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

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

        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;
        }

        /*
         * Check for any removed devices.
         */
        if (spa->spa_autoreplace) {
                spa_aux_check_removed(&spa->spa_spares);
                spa_aux_check_removed(&spa->spa_l2cache);
        }

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

        /*
         * It's possible that the pool was expanded while it was exported.
         * We kick off an async task to handle this for us.
         */
        spa_async_request(spa, SPA_ASYNC_AUTOEXPAND);

        mutex_exit(&spa_namespace_lock);
        spa_history_log_version(spa, LOG_POOL_IMPORT);

        return (0);
}


/*
 * This (illegal) pool name is used when temporarily importing a spa_t in order
 * to get the vdev stats associated with the imported devices.
 */
#define TRYIMPORT_NAME  "$import"

nvlist_t *
spa_tryimport(nvlist_t *tryconfig)
{
        nvlist_t *config = NULL;
        char *poolname;
        spa_t *spa;
        uint64_t state;
        int error;

        if (nvlist_lookup_string(tryconfig, ZPOOL_CONFIG_POOL_NAME, &poolname))
                return (NULL);

        if (nvlist_lookup_uint64(tryconfig, ZPOOL_CONFIG_POOL_STATE, &state))
                return (NULL);

        /*
         * Create and initialize the spa structure.
         */
        mutex_enter(&spa_namespace_lock);
        spa = spa_add(TRYIMPORT_NAME, tryconfig, NULL);
        spa_activate(spa, FREAD);

        /*
         * Pass off the heavy lifting to spa_load().
         * Pass TRUE for mosconfig because the user-supplied config
         * is actually the one to trust when doing an import.
         */
        error = spa_load(spa, SPA_LOAD_TRYIMPORT, 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, id;
        int error;
        vdev_t *rvd = spa->spa_root_vdev;
        vdev_t *vd, *tvd;
        nvlist_t **spares, **l2cache;
        uint_t nspares, nl2cache;

        txg = spa_vdev_enter(spa);

        if ((error = spa_config_parse(spa, &vd, nvroot, NULL, 0,
            VDEV_ALLOC_ADD)) != 0)
                return (spa_vdev_exit(spa, NULL, txg, error));

        spa->spa_pending_vdev = vd;     /* spa_vdev_exit() will clear this */

        if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_SPARES, &spares,
            &nspares) != 0)
                nspares = 0;

        if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_L2CACHE, &l2cache,
            &nl2cache) != 0)
                nl2cache = 0;

        if (vd->vdev_children == 0 && nspares == 0 && nl2cache == 0)
                return (spa_vdev_exit(spa, vd, txg, EINVAL));

        if (vd->vdev_children != 0 &&
            (error = vdev_create(vd, txg, B_FALSE)) != 0)
                return (spa_vdev_exit(spa, vd, txg, error));

        /*
         * We must validate the spares and l2cache devices after checking the
         * children.  Otherwise, vdev_inuse() will blindly overwrite the spare.
         */
        if ((error = spa_validate_aux(spa, nvroot, txg, VDEV_ALLOC_ADD)) != 0)
                return (spa_vdev_exit(spa, vd, txg, error));

        /*
         * Transfer each new top-level vdev from vd to rvd.
         */
        for (int c = 0; c < vd->vdev_children; c++) {

                /*
                 * Set the vdev id to the first hole, if one exists.
                 */
                for (id = 0; id < rvd->vdev_children; id++) {
                        if (rvd->vdev_child[id]->vdev_ishole) {
                                vdev_free(rvd->vdev_child[id]);
                                break;
                        }
                }
                tvd = vd->vdev_child[c];
                vdev_remove_child(vd, tvd);
                tvd->vdev_id = id;
                vdev_add_child(rvd, tvd);
                vdev_config_dirty(tvd);
        }

        if (nspares != 0) {
                spa_set_aux_vdevs(&spa->spa_spares, spares, nspares,
                    ZPOOL_CONFIG_SPARES);
                spa_load_spares(spa);
                spa->spa_spares.sav_sync = B_TRUE;
        }

        if (nl2cache != 0) {
                spa_set_aux_vdevs(&spa->spa_l2cache, l2cache, nl2cache,
                    ZPOOL_CONFIG_L2CACHE);
                spa_load_l2cache(spa);
                spa->spa_l2cache.sav_sync = B_TRUE;
        }

        /*
         * We have to be careful when adding new vdevs to an existing pool.
         * If other threads start allocating from these vdevs before we
         * sync the config cache, and we lose power, then upon reboot we may
         * fail to open the pool because there are DVAs that the config cache
         * can't translate.  Therefore, we first add the vdevs without
         * initializing metaslabs; sync the config cache (via spa_vdev_exit());
         * and then let spa_config_update() initialize the new metaslabs.
         *
         * spa_load() checks for added-but-not-initialized vdevs, so that
         * if we lose power at any point in this sequence, the remaining
         * steps will be completed the next time we load the pool.
         */
        (void) spa_vdev_exit(spa, vd, txg, 0);

        mutex_enter(&spa_namespace_lock);
        spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
        mutex_exit(&spa_namespace_lock);

        return (0);
}

/*
 * Attach a device to a mirror.  The arguments are the path to any device
 * in the mirror, and the nvroot for the new device.  If the path specifies
 * a device that is not mirrored, we automatically insert the mirror vdev.
 *
 * If 'replacing' is specified, the new device is intended to replace the
 * existing device; in this case the two devices are made into their own
 * mirror using the 'replacing' vdev, which is functionally identical to
 * the mirror vdev (it actually reuses all the same ops) but has a few
 * extra rules: you can't attach to it after it's been created, and upon
 * completion of resilvering, the first disk (the one being replaced)
 * is automatically detached.
 */
int
spa_vdev_attach(spa_t *spa, uint64_t guid, nvlist_t *nvroot, int replacing)
{
        uint64_t txg, open_txg;
        vdev_t *rvd = spa->spa_root_vdev;
        vdev_t *oldvd, *newvd, *newrootvd, *pvd, *tvd;
        vdev_ops_t *pvops;
        char *oldvdpath, *newvdpath;
        int newvd_isspare;
        int error;

        txg = spa_vdev_enter(spa);

        oldvd = spa_lookup_by_guid(spa, guid, B_FALSE);

        if (oldvd == NULL)
                return (spa_vdev_exit(spa, NULL, txg, ENODEV));

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

        pvd = oldvd->vdev_parent;

        if ((error = spa_config_parse(spa, &newrootvd, nvroot, NULL, 0,
            VDEV_ALLOC_ADD)) != 0)
                return (spa_vdev_exit(spa, NULL, txg, EINVAL));

        if (newrootvd->vdev_children != 1)
                return (spa_vdev_exit(spa, newrootvd, txg, EINVAL));

        newvd = newrootvd->vdev_child[0];

        if (!newvd->vdev_ops->vdev_op_leaf)
                return (spa_vdev_exit(spa, newrootvd, txg, EINVAL));

        if ((error = vdev_create(newrootvd, txg, replacing)) != 0)
                return (spa_vdev_exit(spa, newrootvd, txg, error));

        /*
         * Spares can't replace logs
         */
        if (oldvd->vdev_top->vdev_islog && newvd->vdev_isspare)
                return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));

        if (!replacing) {
                /*
                 * For attach, the only allowable parent is a mirror or the root
                 * vdev.
                 */
                if (pvd->vdev_ops != &vdev_mirror_ops &&
                    pvd->vdev_ops != &vdev_root_ops)
                        return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));

                pvops = &vdev_mirror_ops;
        } else {
                /*
                 * Active hot spares can only be replaced by inactive hot
                 * spares.
                 */
                if (pvd->vdev_ops == &vdev_spare_ops &&
                    pvd->vdev_child[1] == oldvd &&
                    !spa_has_spare(spa, newvd->vdev_guid))
                        return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));

                /*
                 * If the source is a hot spare, and the parent isn't already a
                 * spare, then we want to create a new hot spare.  Otherwise, we
                 * want to create a replacing vdev.  The user is not allowed to
                 * attach to a spared vdev child unless the 'isspare' state is
                 * the same (spare replaces spare, non-spare replaces
                 * non-spare).
                 */
                if (pvd->vdev_ops == &vdev_replacing_ops)
                        return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
                else if (pvd->vdev_ops == &vdev_spare_ops &&
                    newvd->vdev_isspare != oldvd->vdev_isspare)
                        return (spa_vdev_exit(spa, newrootvd, txg, ENOTSUP));
                else if (pvd->vdev_ops != &vdev_spare_ops &&
                    newvd->vdev_isspare)
                        pvops = &vdev_spare_ops;
                else
                        pvops = &vdev_replacing_ops;
        }

        /*
         * Make sure the new device is big enough.
         */
        if (newvd->vdev_asize < vdev_get_min_asize(oldvd))
                return (spa_vdev_exit(spa, newrootvd, txg, EOVERFLOW));

        /*
         * The new device cannot have a higher alignment requirement
         * than the top-level vdev.
         */
        if (newvd->vdev_ashift > oldvd->vdev_top->vdev_ashift)
                return (spa_vdev_exit(spa, newrootvd, txg, EDOM));

        /*
         * If this is an in-place replacement, update oldvd's path and devid
         * to make it distinguishable from newvd, and unopenable from now on.
         */
        if (strcmp(oldvd->vdev_path, newvd->vdev_path) == 0) {
                spa_strfree(oldvd->vdev_path);
                oldvd->vdev_path = kmem_alloc(strlen(newvd->vdev_path) + 5,
                    KM_SLEEP);
                (void) sprintf(oldvd->vdev_path, "%s/%s",
                    newvd->vdev_path, "old");
                if (oldvd->vdev_devid != NULL) {
                        spa_strfree(oldvd->vdev_devid);
                        oldvd->vdev_devid = NULL;
                }
        }

        /*
         * If the parent is not a mirror, or if we're replacing, insert the new
         * mirror/replacing/spare vdev above oldvd.
         */
        if (pvd->vdev_ops != pvops)
                pvd = vdev_add_parent(oldvd, pvops);

        ASSERT(pvd->vdev_top->vdev_parent == rvd);
        ASSERT(pvd->vdev_ops == pvops);
        ASSERT(oldvd->vdev_parent == pvd);

        /*
         * Extract the new device from its root and add it to pvd.
         */
        vdev_remove_child(newrootvd, newvd);
        newvd->vdev_id = pvd->vdev_children;
        newvd->vdev_crtxg = oldvd->vdev_crtxg;
        vdev_add_child(pvd, newvd);

        tvd = newvd->vdev_top;
        ASSERT(pvd->vdev_top == tvd);
        ASSERT(tvd->vdev_parent == rvd);

        vdev_config_dirty(tvd);

        /*
         * Set newvd's DTL to [TXG_INITIAL, 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);

        spa_history_internal_log(LOG_POOL_VDEV_ATTACH, spa, NULL,
            CRED(),  "%s vdev=%s %s vdev=%s",
            replacing && newvd_isspare ? "spare in" :
            replacing ? "replace" : "attach", newvdpath,
            replacing ? "for" : "to", oldvdpath);

        spa_strfree(oldvdpath);
        spa_strfree(newvdpath);

        /*
         * 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 'autoexpand' property is set on the pool then automatically
         * try to expand the size of the pool. For example if the device we
         * just detached was smaller than the others, it may be possible to
         * add metaslabs (i.e. grow the pool). We need to reopen the vdev
         * first so that we can obtain the updated sizes of the leaf vdevs.
         */
        if (spa->spa_autoexpand) {
                vdev_reopen(tvd);
                vdev_expand(tvd, txg);
        }

        vdev_config_dirty(tvd);

        /*
         * Mark vd's DTL as dirty in this txg.  vdev_dtl_sync() will see that
         * vd->vdev_detached is set and free vd's DTL object in syncing context.
         * But first make sure we're not on any *other* txg's DTL list, to
         * prevent vd from being accessed after it's freed.
         */
        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 *));
}

/*
 * Removing a device from the vdev namespace requires several steps
 * and can take a significant amount of time.  As a result we use
 * the spa_vdev_config_[enter/exit] functions which allow us to
 * grab and release the spa_config_lock while still holding the namespace
 * lock.  During each step the configuration is synced out.
 */

/*
 * Initial phase of device removal - stop future allocations from this device.
 */
void
spa_vdev_remove_start(spa_t *spa, vdev_t *vd)
{
        metaslab_group_t *mg = vd->vdev_mg;

        ASSERT(MUTEX_HELD(&spa_namespace_lock));
        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
        ASSERT(vd == vd->vdev_top);

        /*
         * Remove our vdev from the allocatable vdevs
         */
        if (mg)
                metaslab_class_remove(mg->mg_class, mg);
}

/*
 * Evacuate the device.
 */
int
spa_vdev_remove_evacuate(spa_t *spa, vdev_t *vd)
{
        uint64_t txg;
        int error;

        ASSERT(MUTEX_HELD(&spa_namespace_lock));
        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == 0);
        ASSERT(vd == vd->vdev_top);

        /*
         * Evacuate the device.  We don't hold the config lock as writer
         * since we need to do I/O but we do keep the
         * spa_namespace_lock held.  Once this completes the device
         * should no longer have any blocks allocated on it.
         */
        if (vd->vdev_islog) {
                /*
                 * Evacuate the device.
                 */
                if (error = dmu_objset_find(spa_name(spa),
                    zil_vdev_offline, NULL, DS_FIND_CHILDREN)) {
                        uint64_t txg;

                        txg = spa_vdev_config_enter(spa);
                        metaslab_class_add(spa->spa_log_class,
                            vd->vdev_mg);
                        return (spa_vdev_exit(spa, NULL, txg, error));
                }
                txg_wait_synced(spa_get_dsl(spa), 0);
        }

        /*
         * Remove any remaining MOS metadata associated with the device.
         */
        txg = spa_vdev_config_enter(spa);
        vd->vdev_removing = B_TRUE;
        vdev_dirty(vd, 0, NULL, txg);
        vdev_config_dirty(vd);
        spa_vdev_config_exit(spa, NULL, txg, 0, FTAG);

        return (0);
}

/*
 * Complete the removal by cleaning up the namespace.
 */
void
spa_vdev_remove_done(spa_t *spa, vdev_t *vd)
{
        vdev_t *rvd = spa->spa_root_vdev;
        metaslab_group_t *mg = vd->vdev_mg;
        uint64_t id = vd->vdev_id;
        boolean_t last_vdev = (id == (rvd->vdev_children - 1));

        ASSERT(MUTEX_HELD(&spa_namespace_lock));
        ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
        ASSERT(vd == vd->vdev_top);

        (void) vdev_label_init(vd, 0, VDEV_LABEL_REMOVE);

        if (list_link_active(&vd->vdev_state_dirty_node))
                vdev_state_clean(vd);
        if (list_link_active(&vd->vdev_config_dirty_node))
                vdev_config_clean(vd);

        vdev_free(vd);

        /*
         * It's possible that another thread is trying todo a spa_vdev_add()
         * at the same time we're trying remove it. As a result the
         * added vdev may not have initialized its metaslabs yet.
         */
        if (mg != NULL)
                metaslab_group_destroy(mg);

        if (last_vdev) {
                vdev_compact_children(rvd);
        } else {
                vd = vdev_alloc_common(spa, id, 0, &vdev_hole_ops);
                vdev_add_child(rvd, vd);
        }
        vdev_config_dirty(rvd);

        /*
         * Reassess the health of our root vdev.
         */
        vdev_reopen(rvd);
}

/*
 * Remove a device from the pool.  Currently, this supports removing only hot
 * spares, slogs, and level 2 ARC devices.
 */
int
spa_vdev_remove(spa_t *spa, uint64_t guid, boolean_t unspare)
{
        vdev_t *vd;
        nvlist_t **spares, **l2cache, *nv;
        uint64_t txg = 0;
        uint_t nspares, nl2cache;
        int error = 0;
        boolean_t locked = MUTEX_HELD(&spa_namespace_lock);

        if (!locked)
                txg = spa_vdev_enter(spa);

        vd = spa_lookup_by_guid(spa, guid, B_FALSE);

        if (spa->spa_spares.sav_vdevs != NULL &&
            nvlist_lookup_nvlist_array(spa->spa_spares.sav_config,
            ZPOOL_CONFIG_SPARES, &spares, &nspares) == 0 &&
            (nv = spa_nvlist_lookup_by_guid(spares, nspares, guid)) != NULL) {
                /*
                 * Only remove the hot spare if it's not currently in use
                 * in this pool.
                 */
                if (vd == NULL || unspare) {
                        spa_vdev_remove_aux(spa->spa_spares.sav_config,
                            ZPOOL_CONFIG_SPARES, spares, nspares, nv);
                        spa_load_spares(spa);
                        spa->spa_spares.sav_sync = B_TRUE;
                } else {
                        error = EBUSY;
                }
        } else if (spa->spa_l2cache.sav_vdevs != NULL &&
            nvlist_lookup_nvlist_array(spa->spa_l2cache.sav_config,
            ZPOOL_CONFIG_L2CACHE, &l2cache, &nl2cache) == 0 &&
            (nv = spa_nvlist_lookup_by_guid(l2cache, nl2cache, guid)) != NULL) {
                /*
                 * Cache devices can always be removed.
                 */
                spa_vdev_remove_aux(spa->spa_l2cache.sav_config,
                    ZPOOL_CONFIG_L2CACHE, l2cache, nl2cache, nv);
                spa_load_l2cache(spa);
                spa->spa_l2cache.sav_sync = B_TRUE;
        } else if (vd != NULL && vd->vdev_islog) {
                ASSERT(!locked);
                ASSERT(vd == vd->vdev_top);

                /*
                 * XXX - Once we have bp-rewrite this should
                 * become the common case.
                 */

                /*
                 * 1. Stop allocations
                 * 2. Evacuate the device (i.e. kill off stubby and
                 *    metadata) and wait for it to complete (i.e. sync).
                 * 3. Cleanup the vdev namespace.
                 */
                spa_vdev_remove_start(spa, vd);

                /*
                 * Wait for the youngest allocations and frees to sync,
                 * and then wait for the deferral of those frees to finish.
                 */
                spa_vdev_config_exit(spa, NULL,
                    txg + TXG_CONCURRENT_STATES + TXG_DEFER_SIZE, 0, FTAG);

                if ((error = spa_vdev_remove_evacuate(spa, vd)) != 0)
                        return (error);
                txg = spa_vdev_config_enter(spa);

                spa_vdev_remove_done(spa, vd);

        } else if (vd != NULL) {
                /*
                 * Normal vdevs cannot be removed (yet).
                 */
                error = ENOTSUP;
        } else {
                /*
                 * There is no vdev of any kind with the specified guid.
                 */
                error = ENOENT;
        }

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

        return (error);
}

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

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

        /*
         * Check for a completed replacement.
         */
        if (vd->vdev_ops == &vdev_replacing_ops && vd->vdev_children == 2) {
                oldvd = vd->vdev_child[0];
                newvd = vd->vdev_child[1];

                if (vdev_dtl_empty(newvd, DTL_MISSING) &&
                    !vdev_dtl_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);

                /*
                 * We want to clear the stats, but we don't want to do a full
                 * vdev_clear() as that will cause us to throw away
                 * degraded/faulted state as well as attempt to reopen the
                 * device, all of which is a waste.
                 */
                vd->vdev_stat.vs_read_errors = 0;
                vd->vdev_stat.vs_write_errors = 0;
                vd->vdev_stat.vs_checksum_errors = 0;

                vdev_state_dirty(vd->vdev_top);
        }

        for (int c = 0; c < vd->vdev_children; c++)
                spa_async_remove(spa, vd->vdev_child[c]);
}

static void
spa_async_probe(spa_t *spa, vdev_t *vd)
{
        if (vd->vdev_probe_wanted) {
                vd->vdev_probe_wanted = 0;
                vdev_reopen(vd);        /* vdev_open() does the actual probe */
        }

        for (int c = 0; c < vd->vdev_children; c++)
                spa_async_probe(spa, vd->vdev_child[c]);
}

static void
spa_async_autoexpand(spa_t *spa, vdev_t *vd)
{
        sysevent_id_t eid;
        nvlist_t *attr;
        char *physpath;

        if (!spa->spa_autoexpand)
                return;

        for (int c = 0; c < vd->vdev_children; c++) {
                vdev_t *cvd = vd->vdev_child[c];
                spa_async_autoexpand(spa, cvd);
        }

        if (!vd->vdev_ops->vdev_op_leaf || vd->vdev_physpath == NULL)
                return;

        physpath = kmem_zalloc(MAXPATHLEN, KM_SLEEP);
        (void) snprintf(physpath, MAXPATHLEN, "/devices%s", vd->vdev_physpath);

        VERIFY(nvlist_alloc(&attr, NV_UNIQUE_NAME, KM_SLEEP) == 0);
        VERIFY(nvlist_add_string(attr, DEV_PHYS_PATH, physpath) == 0);

        (void) ddi_log_sysevent(zfs_dip, SUNW_VENDOR, EC_DEV_STATUS,
            ESC_DEV_DLE, attr, &eid, DDI_SLEEP);

        nvlist_free(attr);
        kmem_free(physpath, MAXPATHLEN);
}

static void
spa_async_thread(spa_t *spa)
{
        int tasks;

        ASSERT(spa->spa_sync_on);

        mutex_enter(&spa->spa_async_lock);
        tasks = spa->spa_async_tasks;
        spa->spa_async_tasks = 0;
        mutex_exit(&spa->spa_async_lock);

        /*
         * See if the config needs to be updated.
         */
        if (tasks & SPA_ASYNC_CONFIG_UPDATE) {
                uint64_t old_space, new_space;

                mutex_enter(&spa_namespace_lock);
                old_space = metaslab_class_get_space(spa_normal_class(spa));
                spa_config_update(spa, SPA_CONFIG_UPDATE_POOL);
                new_space = metaslab_class_get_space(spa_normal_class(spa));
                mutex_exit(&spa_namespace_lock);

                /*
                 * If the pool grew as a result of the config update,
                 * then log an internal history event.
                 */
                if (new_space != old_space) {
                        spa_history_internal_log(LOG_POOL_VDEV_ONLINE,
                            spa, NULL, CRED(),
                            "pool '%s' size: %llu(+%llu)",
                            spa_name(spa), new_space, new_space - old_space);
                }
        }

        /*
         * See if any devices need to be marked REMOVED.
         */
        if (tasks & SPA_ASYNC_REMOVE) {
                spa_vdev_state_enter(spa, SCL_NONE);
                spa_async_remove(spa, spa->spa_root_vdev);
                for (int i = 0; i < spa->spa_l2cache.sav_count; i++)
                        spa_async_remove(spa, spa->spa_l2cache.sav_vdevs[i]);
                for (int i = 0; i < spa->spa_spares.sav_count; i++)
                        spa_async_remove(spa, spa->spa_spares.sav_vdevs[i]);
                (void) spa_vdev_state_exit(spa, NULL, 0);
        }

        if ((tasks & SPA_ASYNC_AUTOEXPAND) && !spa_suspended(spa)) {
                spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
                spa_async_autoexpand(spa, spa->spa_root_vdev);
                spa_config_exit(spa, SCL_CONFIG, FTAG);
        }

        /*
         * See if any devices need to be probed.
         */
        if (tasks & SPA_ASYNC_PROBE) {
                spa_vdev_state_enter(spa, SCL_NONE);
                spa_async_probe(spa, spa->spa_root_vdev);
                (void) spa_vdev_state_exit(spa, NULL, 0);
        }

        /*
         * If any devices are done replacing, detach them.
         */
        if (tasks & SPA_ASYNC_RESILVER_DONE)
                spa_vdev_resilver_done(spa);

        /*
         * Kick off a resilver.
         */
        if (tasks & SPA_ASYNC_RESILVER)
                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_bplist(spa_t *spa, bplist_t *bpl, dmu_tx_t *tx, uint64_t txg)
{
        blkptr_t blk;
        uint64_t itor = 0;
        uint8_t c = 1;

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

        bplist_vacate(bpl, tx);

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

static void
spa_sync_free(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
{
        zio_t *zio = arg;

        zio_nowait(zio_free_sync(zio, zio->io_spa, dmu_tx_get_txg(tx), bp,
            zio->io_flags));
}

static void
spa_sync_nvlist(spa_t *spa, uint64_t obj, nvlist_t *nv, dmu_tx_t *tx)
{
        char *packed = NULL;
        size_t bufsize;
        size_t nvsize = 0;
        dmu_buf_t *db;

        VERIFY(nvlist_size(nv, &nvsize, NV_ENCODE_XDR) == 0);

        /*
         * Write full (SPA_CONFIG_BLOCKSIZE) blocks of configuration
         * information.  This avoids the dbuf_will_dirty() path and
         * saves us a pre-read to get data we don't actually care about.
         */
        bufsize = P2ROUNDUP(nvsize, SPA_CONFIG_BLOCKSIZE);
        packed = kmem_alloc(bufsize, KM_SLEEP);

        VERIFY(nvlist_pack(nv, &packed, &nvsize, NV_ENCODE_XDR,
            KM_SLEEP) == 0);
        bzero(packed + nvsize, bufsize - nvsize);

        dmu_write(spa->spa_meta_objset, obj, 0, bufsize, packed, tx);

        kmem_free(packed, bufsize);

        VERIFY(0 == dmu_bonus_hold(spa->spa_meta_objset, obj, FTAG, &db));
        dmu_buf_will_dirty(db, tx);
        *(uint64_t *)db->db_data = nvsize;
        dmu_buf_rele(db, FTAG);
}

static void
spa_sync_aux_dev(spa_t *spa, spa_aux_vdev_t *sav, dmu_tx_t *tx,
    const char *config, const char *entry)
{
        nvlist_t *nvroot;
        nvlist_t **list;
        int i;

        if (!sav->sav_sync)
                return;

        /*
         * Update the MOS nvlist describing the list of available devices.
         * spa_validate_aux() will have already made sure this nvlist is
         * valid and the vdevs are labeled appropriately.
         */
        if (sav->sav_object == 0) {
                sav->sav_object = dmu_object_alloc(spa->spa_meta_objset,
                    DMU_OT_PACKED_NVLIST, 1 << 14, DMU_OT_PACKED_NVLIST_SIZE,
                    sizeof (uint64_t), tx);
                VERIFY(zap_update(spa->spa_meta_objset,
                    DMU_POOL_DIRECTORY_OBJECT, entry, sizeof (uint64_t), 1,
                    &sav->sav_object, tx) == 0);
        }

        VERIFY(nvlist_alloc(&nvroot, NV_UNIQUE_NAME, KM_SLEEP) == 0);
        if (sav->sav_count == 0) {
                VERIFY(nvlist_add_nvlist_array(nvroot, config, NULL, 0) == 0);
        } else {
                list = kmem_alloc(sav->sav_count * sizeof (void *), KM_SLEEP);
                for (i = 0; i < sav->sav_count; i++)
                        list[i] = vdev_config_generate(spa, sav->sav_vdevs[i],
                            B_FALSE, 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) {
                                VERIFY((spa->spa_pool_props_object =
                                    zap_create(mos, DMU_OT_POOL_PROPS,
                                    DMU_OT_NONE, 0, tx)) > 0);

                                VERIFY(zap_update(mos,
                                    DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_PROPS,
                                    8, 1, &spa->spa_pool_props_object, tx)
                                    == 0);
                        }

                        /* normalize the property name */
                        propname = zpool_prop_to_name(prop);
                        proptype = zpool_prop_get_type(prop);

                        if (nvpair_type(elem) == DATA_TYPE_STRING) {
                                ASSERT(proptype == PROP_TYPE_STRING);
                                VERIFY(nvpair_value_string(elem, &strval) == 0);
                                VERIFY(zap_update(mos,
                                    spa->spa_pool_props_object, propname,
                                    1, strlen(strval) + 1, strval, tx) == 0);

                        } else if (nvpair_type(elem) == DATA_TYPE_UINT64) {
                                VERIFY(nvpair_value_uint64(elem, &intval) == 0);

                                if (proptype == PROP_TYPE_INDEX) {
                                        const char *unused;
                                        VERIFY(zpool_prop_index_to_string(
                                            prop, intval, &unused) == 0);
                                }
                                VERIFY(zap_update(mos,
                                    spa->spa_pool_props_object, propname,
                                    8, 1, &intval, tx) == 0);
                        } else {
                                ASSERT(0); /* not allowed */
                        }

                        switch (prop) {
                        case ZPOOL_PROP_DELEGATION:
                                spa->spa_delegation = intval;
                                break;
                        case ZPOOL_PROP_BOOTFS:
                                spa->spa_bootfs = intval;
                                break;
                        case ZPOOL_PROP_FAILUREMODE:
                                spa->spa_failmode = intval;
                                break;
                        case ZPOOL_PROP_AUTOEXPAND:
                                spa->spa_autoexpand = intval;
                                spa_async_request(spa, SPA_ASYNC_AUTOEXPAND);
                                break;
                        case ZPOOL_PROP_DEDUPDITTO:
                                spa->spa_dedup_ditto = intval;
                                break;
                        default:
                                break;
                        }
                }

                /* log internal history if this is not a zpool create */
                if (spa_version(spa) >= SPA_VERSION_ZPOOL_HISTORY &&
                    tx->tx_txg != TXG_INITIAL) {
                        spa_history_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 *defer_bpl = &spa->spa_deferred_bplist;
        bplist_t *free_bpl = &spa->spa_free_bplist[txg & TXG_MASK];
        vdev_t *rvd = spa->spa_root_vdev;
        vdev_t *vd;
        dmu_tx_t *tx;
        int error;

        /*
         * Lock out configuration changes.
         */
        spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);

        spa->spa_syncing_txg = txg;
        spa->spa_sync_pass = 0;

        /*
         * If there are any pending vdev state changes, convert them
         * into config changes that go out with this transaction group.
         */
        spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);
        while (list_head(&spa->spa_state_dirty_list) != NULL) {
                /*
                 * We need the write lock here because, for aux vdevs,
                 * calling vdev_config_dirty() modifies sav_config.
                 * This is ugly and will become unnecessary when we
                 * eliminate the aux vdev wart by integrating all vdevs
                 * into the root vdev tree.
                 */
                spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
                spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_WRITER);
                while ((vd = list_head(&spa->spa_state_dirty_list)) != NULL) {
                        vdev_state_clean(vd);
                        vdev_config_dirty(vd);
                }
                spa_config_exit(spa, SCL_CONFIG | SCL_STATE, FTAG);
                spa_config_enter(spa, SCL_CONFIG | SCL_STATE, FTAG, RW_READER);
        }
        spa_config_exit(spa, SCL_STATE, FTAG);

        VERIFY(0 == bplist_open(defer_bpl, mos, spa->spa_deferred_bplist_obj));

        tx = dmu_tx_create_assigned(dp, txg);

        /*
         * If we are upgrading to SPA_VERSION_RAIDZ_DEFLATE this txg,
         * set spa_deflate if we have no raid-z vdevs.
         */
        if (spa->spa_ubsync.ub_version < SPA_VERSION_RAIDZ_DEFLATE &&
            spa->spa_uberblock.ub_version >= SPA_VERSION_RAIDZ_DEFLATE) {
                int i;

                for (i = 0; i < rvd->vdev_children; i++) {
                        vd = rvd->vdev_child[i];
                        if (vd->vdev_deflate_ratio != SPA_MINBLOCKSIZE)
                                break;
                }
                if (i == rvd->vdev_children) {
                        spa->spa_deflate = TRUE;
                        VERIFY(0 == zap_add(spa->spa_meta_objset,
                            DMU_POOL_DIRECTORY_OBJECT, DMU_POOL_DEFLATE,
                            sizeof (uint64_t), 1, &spa->spa_deflate, tx));
                }
        }

        if (spa->spa_ubsync.ub_version < SPA_VERSION_ORIGIN &&
            spa->spa_uberblock.ub_version >= SPA_VERSION_ORIGIN) {
                dsl_pool_create_origin(dp, tx);

                /* Keeping the origin open increases spa_minref */
                spa->spa_minref += 3;
        }

        if (spa->spa_ubsync.ub_version < SPA_VERSION_NEXT_CLONES &&
            spa->spa_uberblock.ub_version >= SPA_VERSION_NEXT_CLONES) {
                dsl_pool_upgrade_clones(dp, tx);
        }

        /*
         * If anything has changed in this txg, 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_bplist(spa, defer_bpl, tx, txg);

        /*
         * Iterate to convergence.
         */
        do {
                int pass = ++spa->spa_sync_pass;

                spa_sync_config_object(spa, tx);
                spa_sync_aux_dev(spa, &spa->spa_spares, tx,
                    ZPOOL_CONFIG_SPARES, DMU_POOL_SPARES);
                spa_sync_aux_dev(spa, &spa->spa_l2cache, tx,
                    ZPOOL_CONFIG_L2CACHE, DMU_POOL_L2CACHE);
                spa_errlog_sync(spa, txg);
                dsl_pool_sync(dp, txg);

                if (pass <= SYNC_PASS_DEFERRED_FREE) {
                        zio_t *zio = zio_root(spa, NULL, NULL, 0);
                        bplist_sync(free_bpl, spa_sync_free, zio, tx);
                        VERIFY(zio_wait(zio) == 0);
                } else {
                        bplist_sync(free_bpl, bplist_enqueue_cb, defer_bpl, tx);
                }

                ddt_sync(spa, txg);

                while (vd = txg_list_remove(&spa->spa_vdev_txg_list, txg))
                        vdev_sync(vd, txg);

        } while (dmu_objset_is_dirty(mos, txg));

        ASSERT(free_bpl->bpl_queue == NULL);

        bplist_close(defer_bpl);

        /*
         * Rewrite the vdev configuration (which includes the uberblock)
         * to commit the transaction group.
         *
         * If there are no dirty vdevs, we sync the uberblock to a few
         * random top-level vdevs that are known to be visible in the
         * config cache (see spa_vdev_add() for a complete description).
         * If there *are* dirty vdevs, sync the uberblock to all vdevs.
         */
        for (;;) {
                /*
                 * We hold SCL_STATE to prevent vdev open/close/etc.
                 * while we're attempting to write the vdev labels.
                 */
                spa_config_enter(spa, SCL_STATE, FTAG, RW_READER);

                if (list_is_empty(&spa->spa_config_dirty_list)) {
                        vdev_t *svd[SPA_DVAS_PER_BP];
                        int svdcount = 0;
                        int children = rvd->vdev_children;
                        int c0 = spa_get_random(children);

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

                spa_config_exit(spa, SCL_STATE, FTAG);

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

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

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

        spa->spa_ubsync = spa->spa_uberblock;

        dsl_pool_sync_done(dp, txg);

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

        spa_update_dspace(spa);

        /*
         * It had better be the case that we didn't dirty anything
         * since vdev_config_sync().
         */
        ASSERT(txg_list_empty(&dp->dp_dirty_datasets, txg));
        ASSERT(txg_list_empty(&dp->dp_dirty_dirs, txg));
        ASSERT(txg_list_empty(&spa->spa_vdev_txg_list, txg));
        ASSERT(defer_bpl->bpl_queue == NULL);
        ASSERT(free_bpl->bpl_queue == NULL);

        spa->spa_sync_pass = 0;

        spa_config_exit(spa, SCL_CONFIG, FTAG);

        spa_handle_ignored_writes(spa);

        /*
         * If any async tasks have been requested, kick them off.
         */
        spa_async_dispatch(spa);
}

/*
 * Sync all pools.  We don't want to hold the namespace lock across these
 * operations, so we take a reference on the spa_t and drop the lock during the
 * sync.
 */
void
spa_sync_allpools(void)
{
        spa_t *spa = NULL;
        mutex_enter(&spa_namespace_lock);
        while ((spa = spa_next(spa)) != NULL) {
                if (spa_state(spa) != POOL_STATE_ACTIVE || spa_suspended(spa))
                        continue;
                spa_open_ref(spa, FTAG);
                mutex_exit(&spa_namespace_lock);
                txg_wait_synced(spa_get_dsl(spa), 0);
                mutex_enter(&spa_namespace_lock);
                spa_close(spa, FTAG);
        }
        mutex_exit(&spa_namespace_lock);
}

/*
 * ==========================================================================
 * Miscellaneous routines
 * ==========================================================================
 */

/*
 * Remove all pools in the system.
 */
void
spa_evict_all(void)
{
        spa_t *spa;

        /*
         * Remove all cached state.  All pools should be closed now,
         * so every spa in the AVL tree should be unreferenced.
         */
        mutex_enter(&spa_namespace_lock);
        while ((spa = spa_next(NULL)) != NULL) {
                /*
                 * Stop async tasks.  The async thread may need to detach
                 * a device that's been replaced, which requires grabbing
                 * spa_namespace_lock, so we must drop it here.
                 */
                spa_open_ref(spa, FTAG);
                mutex_exit(&spa_namespace_lock);
                spa_async_suspend(spa);
                mutex_enter(&spa_namespace_lock);
                spa_close(spa, FTAG);

                if (spa->spa_state != POOL_STATE_UNINITIALIZED) {
                        spa_unload(spa);
                        spa_deactivate(spa);
                }
                spa_remove(spa);
        }
        mutex_exit(&spa_namespace_lock);
}

vdev_t *
spa_lookup_by_guid(spa_t *spa, uint64_t guid, boolean_t aux)
{
        vdev_t *vd;
        int i;

        if ((vd = vdev_lookup_by_guid(spa->spa_root_vdev, guid)) != NULL)
                return (vd);

        if (aux) {
                for (i = 0; i < spa->spa_l2cache.sav_count; i++) {
                        vd = spa->spa_l2cache.sav_vdevs[i];
                        if (vd->vdev_guid == guid)
                                return (vd);
                }

                for (i = 0; i < spa->spa_spares.sav_count; i++) {
                        vd = spa->spa_spares.sav_vdevs[i];
                        if (vd->vdev_guid == guid)
                                return (vd);
                }
        }

        return (NULL);
}

void
spa_upgrade(spa_t *spa, uint64_t version)
{
        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);

        /*
         * This should only be called for a non-faulted pool, and since a
         * future version would result in an unopenable pool, this shouldn't be
         * possible.
         */
        ASSERT(spa->spa_uberblock.ub_version <= SPA_VERSION);
        ASSERT(version >= spa->spa_uberblock.ub_version);

        spa->spa_uberblock.ub_version = version;
        vdev_config_dirty(spa->spa_root_vdev);

        spa_config_exit(spa, SCL_ALL, FTAG);

        txg_wait_synced(spa_get_dsl(spa), 0);
}

boolean_t
spa_has_spare(spa_t *spa, uint64_t guid)
{
        int i;
        uint64_t spareguid;
        spa_aux_vdev_t *sav = &spa->spa_spares;

        for (i = 0; i < sav->sav_count; i++)
                if (sav->sav_vdevs[i]->vdev_guid == guid)
                        return (B_TRUE);

        for (i = 0; i < sav->sav_npending; i++) {
                if (nvlist_lookup_uint64(sav->sav_pending[i], ZPOOL_CONFIG_GUID,
                    &spareguid) == 0 && spareguid == guid)
                        return (B_TRUE);
        }

        return (B_FALSE);
}

/*
 * Check if a pool has an active shared spare device.
 * Note: reference count of an active spare is 2, as a spare and as a replace
 */
static boolean_t
spa_has_active_shared_spare(spa_t *spa)
{
        int i, refcnt;
        uint64_t pool;
        spa_aux_vdev_t *sav = &spa->spa_spares;

        for (i = 0; i < sav->sav_count; i++) {
                if (spa_spare_exists(sav->sav_vdevs[i]->vdev_guid, &pool,
                    &refcnt) && pool != 0ULL && pool == spa_guid(spa) &&
                    refcnt > 2)
                        return (B_TRUE);
        }

        return (B_FALSE);
}

/*
 * Post a sysevent corresponding to the given event.  The 'name' must be one of
 * the event definitions in sys/sysevent/eventdefs.h.  The payload will be
 * filled in from the spa and (optionally) the vdev.  This doesn't do anything
 * in the userland libzpool, as we don't want consumers to misinterpret ztest
 * or zdb as real changes.
 */
void
spa_event_notify(spa_t *spa, vdev_t *vd, const char *name)
{
#ifdef _KERNEL
        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
}