fs/zfs/vdev.c

	vdev.c revision 0e34b6a7bff4918432f0aa6b1dfaf73ac9df45b1
/*
 * 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 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/zfs_context.h>
#include <sys/fm/fs/zfs.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/dmu.h>
#include <sys/dmu_tx.h>
#include <sys/vdev_impl.h>
#include <sys/uberblock_impl.h>
#include <sys/metaslab.h>
#include <sys/metaslab_impl.h>
#include <sys/space_map.h>
#include <sys/zio.h>
#include <sys/zap.h>
#include <sys/fs/zfs.h>

/*
 * Virtual device management.
 */

static vdev_ops_t *vdev_ops_table[] = {
    &vdev_root_ops,
    &vdev_raidz_ops,
    &vdev_mirror_ops,
    &vdev_replacing_ops,
    &vdev_disk_ops,
    &vdev_file_ops,
    &vdev_missing_ops,
    NULL
};

/*
 * Given a vdev type, return the appropriate ops vector.
 */
static vdev_ops_t *
vdev_getops(const char *type)
{
    vdev_ops_t *ops, **opspp;

    for (opspp = vdev_ops_table; (ops = *opspp) != NULL; opspp++)
        if (strcmp(ops->vdev_op_type, type) == 0)
            break;

    return (ops);
}

/*
 * Default asize function: return the MAX of psize with the asize of
 * all children.  This is what's used by anything other than RAID-Z.
 */
uint64_t
vdev_default_asize(vdev_t *vd, uint64_t psize)
{
    uint64_t asize = P2ROUNDUP(psize, 1ULL << vd->vdev_ashift);
    uint64_t csize;
    uint64_t c;

    for (c = 0; c < vd->vdev_children; c++) {
        csize = vdev_psize_to_asize(vd->vdev_child[c], psize);
        asize = MAX(asize, csize);
    }

    return (asize);
}

/*
 * Get the replaceable or attachable device size.
 * If the parent is a mirror or raidz, the replaceable size is the minimum
 * psize of all its children. For the rest, just return our own psize.
 *
 * e.g.
 *          psize   rsize
 * root         -   -
 *  mirror/raidz    -   -
 *      disk1   20g 20g
 *      disk2   40g 20g
 *  disk3       80g 80g
 */
uint64_t
vdev_get_rsize(vdev_t *vd)
{
    vdev_t *pvd, *cvd;
    uint64_t c, rsize;

    pvd = vd->vdev_parent;

    /*
     * If our parent is NULL or the root, just return our own psize.
     */
    if (pvd == NULL || pvd->vdev_parent == NULL)
        return (vd->vdev_psize);

    rsize = 0;

    for (c = 0; c < pvd->vdev_children; c++) {
        cvd = pvd->vdev_child[c];
        rsize = MIN(rsize - 1, cvd->vdev_psize - 1) + 1;
    }

    return (rsize);
}

vdev_t *
vdev_lookup_top(spa_t *spa, uint64_t vdev)
{
    vdev_t *rvd = spa->spa_root_vdev;

    if (vdev < rvd->vdev_children)
        return (rvd->vdev_child[vdev]);

    return (NULL);
}

vdev_t *
vdev_lookup_by_guid(vdev_t *vd, uint64_t guid)
{
    int c;
    vdev_t *mvd;

    if (vd->vdev_guid == guid)
        return (vd);

    for (c = 0; c < vd->vdev_children; c++)
        if ((mvd = vdev_lookup_by_guid(vd->vdev_child[c], guid)) !=
            NULL)
            return (mvd);

    return (NULL);
}

void
vdev_add_child(vdev_t *pvd, vdev_t *cvd)
{
    size_t oldsize, newsize;
    uint64_t id = cvd->vdev_id;
    vdev_t **newchild;

    ASSERT(spa_config_held(cvd->vdev_spa, RW_WRITER));
    ASSERT(cvd->vdev_parent == NULL);

    cvd->vdev_parent = pvd;

    if (pvd == NULL)
        return;

    ASSERT(id >= pvd->vdev_children || pvd->vdev_child[id] == NULL);

    oldsize = pvd->vdev_children * sizeof (vdev_t *);
    pvd->vdev_children = MAX(pvd->vdev_children, id + 1);
    newsize = pvd->vdev_children * sizeof (vdev_t *);

    newchild = kmem_zalloc(newsize, KM_SLEEP);
    if (pvd->vdev_child != NULL) {
        bcopy(pvd->vdev_child, newchild, oldsize);
        kmem_free(pvd->vdev_child, oldsize);
    }

    pvd->vdev_child = newchild;
    pvd->vdev_child[id] = cvd;

    cvd->vdev_top = (pvd->vdev_top ? pvd->vdev_top: cvd);
    ASSERT(cvd->vdev_top->vdev_parent->vdev_parent == NULL);

    /*
     * Walk up all ancestors to update guid sum.
     */
    for (; pvd != NULL; pvd = pvd->vdev_parent)
        pvd->vdev_guid_sum += cvd->vdev_guid_sum;
}

void
vdev_remove_child(vdev_t *pvd, vdev_t *cvd)
{
    int c;
    uint_t id = cvd->vdev_id;

    ASSERT(cvd->vdev_parent == pvd);

    if (pvd == NULL)
        return;

    ASSERT(id < pvd->vdev_children);
    ASSERT(pvd->vdev_child[id] == cvd);

    pvd->vdev_child[id] = NULL;
    cvd->vdev_parent = NULL;

    for (c = 0; c < pvd->vdev_children; c++)
        if (pvd->vdev_child[c])
            break;

    if (c == pvd->vdev_children) {
        kmem_free(pvd->vdev_child, c * sizeof (vdev_t *));
        pvd->vdev_child = NULL;
        pvd->vdev_children = 0;
    }

    /*
     * Walk up all ancestors to update guid sum.
     */
    for (; pvd != NULL; pvd = pvd->vdev_parent)
        pvd->vdev_guid_sum -= cvd->vdev_guid_sum;
}

/*
 * Remove any holes in the child array.
 */
void
vdev_compact_children(vdev_t *pvd)
{
    vdev_t **newchild, *cvd;
    int oldc = pvd->vdev_children;
    int newc, c;

    ASSERT(spa_config_held(pvd->vdev_spa, RW_WRITER));

    for (c = newc = 0; c < oldc; c++)
        if (pvd->vdev_child[c])
            newc++;

    newchild = kmem_alloc(newc * sizeof (vdev_t *), KM_SLEEP);

    for (c = newc = 0; c < oldc; c++) {
        if ((cvd = pvd->vdev_child[c]) != NULL) {
            newchild[newc] = cvd;
            cvd->vdev_id = newc++;
        }
    }

    kmem_free(pvd->vdev_child, oldc * sizeof (vdev_t *));
    pvd->vdev_child = newchild;
    pvd->vdev_children = newc;
}

/*
 * Allocate and minimally initialize a vdev_t.
 */
static vdev_t *
vdev_alloc_common(spa_t *spa, uint_t id, uint64_t guid, vdev_ops_t *ops)
{
    vdev_t *vd;

    vd = kmem_zalloc(sizeof (vdev_t), KM_SLEEP);

    if (spa->spa_root_vdev == NULL) {
        ASSERT(ops == &vdev_root_ops);
        spa->spa_root_vdev = vd;
    }

    if (guid == 0) {
        if (spa->spa_root_vdev == vd) {
            /*
             * The root vdev's guid will also be the pool guid,
             * which must be unique among all pools.
             */
            while (guid == 0 || spa_guid_exists(guid, 0))
                guid = spa_get_random(-1ULL);
        } else {
            /*
             * Any other vdev's guid must be unique within the pool.
             */
            while (guid == 0 ||
                spa_guid_exists(spa_guid(spa), guid))
                guid = spa_get_random(-1ULL);
        }
        ASSERT(!spa_guid_exists(spa_guid(spa), guid));
    }

    vd->vdev_spa = spa;
    vd->vdev_id = id;
    vd->vdev_guid = guid;
    vd->vdev_guid_sum = guid;
    vd->vdev_ops = ops;
    vd->vdev_state = VDEV_STATE_CLOSED;

    mutex_init(&vd->vdev_dirty_lock, NULL, MUTEX_DEFAULT, NULL);
    mutex_init(&vd->vdev_dtl_lock, NULL, MUTEX_DEFAULT, NULL);
    space_map_create(&vd->vdev_dtl_map, 0, -1ULL, 0, &vd->vdev_dtl_lock);
    space_map_create(&vd->vdev_dtl_scrub, 0, -1ULL, 0, &vd->vdev_dtl_lock);
    txg_list_create(&vd->vdev_ms_list,
        offsetof(struct metaslab, ms_txg_node));
    txg_list_create(&vd->vdev_dtl_list,
        offsetof(struct vdev, vdev_dtl_node));
    vd->vdev_stat.vs_timestamp = gethrtime();

    return (vd);
}

/*
 * Free a vdev_t that has been removed from service.
 */
static void
vdev_free_common(vdev_t *vd)
{
    spa_t *spa = vd->vdev_spa;

    if (vd->vdev_path)
        spa_strfree(vd->vdev_path);
    if (vd->vdev_devid)
        spa_strfree(vd->vdev_devid);

    txg_list_destroy(&vd->vdev_ms_list);
    txg_list_destroy(&vd->vdev_dtl_list);
    mutex_enter(&vd->vdev_dtl_lock);
    space_map_vacate(&vd->vdev_dtl_map, NULL, NULL);
    space_map_destroy(&vd->vdev_dtl_map);
    space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
    space_map_destroy(&vd->vdev_dtl_scrub);
    mutex_exit(&vd->vdev_dtl_lock);
    mutex_destroy(&vd->vdev_dtl_lock);
    mutex_destroy(&vd->vdev_dirty_lock);

    if (vd == spa->spa_root_vdev)
        spa->spa_root_vdev = NULL;

    kmem_free(vd, sizeof (vdev_t));
}

/*
 * Allocate a new vdev.  The 'alloctype' is used to control whether we are
 * creating a new vdev or loading an existing one - the behavior is slightly
 * different for each case.
 */
vdev_t *
vdev_alloc(spa_t *spa, nvlist_t *nv, vdev_t *parent, uint_t id, int alloctype)
{
    vdev_ops_t *ops;
    char *type;
    uint64_t guid = 0, offline = 0;
    vdev_t *vd;

    ASSERT(spa_config_held(spa, RW_WRITER));

    if (nvlist_lookup_string(nv, ZPOOL_CONFIG_TYPE, &type) != 0)
        return (NULL);

    if ((ops = vdev_getops(type)) == NULL)
        return (NULL);

    /*
     * If this is a load, get the vdev guid from the nvlist.
     * Otherwise, vdev_alloc_common() will generate one for us.
     */
    if (alloctype == VDEV_ALLOC_LOAD) {
        uint64_t label_id;

        if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ID, &label_id) ||
            label_id != id)
            return (NULL);

        if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_GUID, &guid) != 0)
            return (NULL);
    }

    vd = vdev_alloc_common(spa, id, guid, ops);

    if (nvlist_lookup_string(nv, ZPOOL_CONFIG_PATH, &vd->vdev_path) == 0)
        vd->vdev_path = spa_strdup(vd->vdev_path);
    if (nvlist_lookup_string(nv, ZPOOL_CONFIG_DEVID, &vd->vdev_devid) == 0)
        vd->vdev_devid = spa_strdup(vd->vdev_devid);

    /*
     * Set the whole_disk property.  If it's not specified, leave the value
     * as -1.
     */
    if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK,
        &vd->vdev_wholedisk) != 0)
        vd->vdev_wholedisk = -1ULL;

    /*
     * Look for the 'not present' flag.  This will only be set if the device
     * was not present at the time of import.
     */
    (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT,
        &vd->vdev_not_present);

    /*
     * If we're a top-level vdev, try to load the allocation parameters.
     */
    if (parent && !parent->vdev_parent && alloctype == VDEV_ALLOC_LOAD) {
        (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY,
            &vd->vdev_ms_array);
        (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT,
            &vd->vdev_ms_shift);
        (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASHIFT,
            &vd->vdev_ashift);
        (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_ASIZE,
            &vd->vdev_asize);
    }

    /*
     * If we're a leaf vdev, try to load the DTL object
     * and the offline state.
     */
    vd->vdev_offline = B_FALSE;
    if (vd->vdev_ops->vdev_op_leaf && alloctype == VDEV_ALLOC_LOAD) {
        (void) nvlist_lookup_uint64(nv, ZPOOL_CONFIG_DTL,
            &vd->vdev_dtl.smo_object);

        if (nvlist_lookup_uint64(nv, ZPOOL_CONFIG_OFFLINE, &offline)
            == 0)
            vd->vdev_offline = offline;
    }

    /*
     * Add ourselves to the parent's list of children.
     */
    vdev_add_child(parent, vd);

    return (vd);
}

void
vdev_free(vdev_t *vd)
{
    int c;

    /*
     * vdev_free() implies closing the vdev first.  This is simpler than
     * trying to ensure complicated semantics for all callers.
     */
    vdev_close(vd);

    /*
     * It's possible to free a vdev that's been added to the dirty
     * list when in the middle of spa_vdev_add().  Handle that case
     * correctly here.
     */
    if (vd->vdev_is_dirty)
        vdev_config_clean(vd);

    /*
     * Free all children.
     */
    for (c = 0; c < vd->vdev_children; c++)
        vdev_free(vd->vdev_child[c]);

    ASSERT(vd->vdev_child == NULL);
    ASSERT(vd->vdev_guid_sum == vd->vdev_guid);

    /*
     * Discard allocation state.
     */
    if (vd == vd->vdev_top)
        vdev_metaslab_fini(vd);

    ASSERT3U(vd->vdev_stat.vs_space, ==, 0);
    ASSERT3U(vd->vdev_stat.vs_alloc, ==, 0);

    /*
     * Remove this vdev from its parent's child list.
     */
    vdev_remove_child(vd->vdev_parent, vd);

    ASSERT(vd->vdev_parent == NULL);

    vdev_free_common(vd);
}

/*
 * Transfer top-level vdev state from svd to tvd.
 */
static void
vdev_top_transfer(vdev_t *svd, vdev_t *tvd)
{
    spa_t *spa = svd->vdev_spa;
    metaslab_t *msp;
    vdev_t *vd;
    int t;

    ASSERT(tvd == tvd->vdev_top);

    tvd->vdev_ms_array = svd->vdev_ms_array;
    tvd->vdev_ms_shift = svd->vdev_ms_shift;
    tvd->vdev_ms_count = svd->vdev_ms_count;

    svd->vdev_ms_array = 0;
    svd->vdev_ms_shift = 0;
    svd->vdev_ms_count = 0;

    tvd->vdev_mg = svd->vdev_mg;
    tvd->vdev_mg->mg_vd = tvd;
    tvd->vdev_ms = svd->vdev_ms;
    tvd->vdev_smo = svd->vdev_smo;

    svd->vdev_mg = NULL;
    svd->vdev_ms = NULL;
    svd->vdev_smo = NULL;

    tvd->vdev_stat.vs_alloc = svd->vdev_stat.vs_alloc;
    tvd->vdev_stat.vs_space = svd->vdev_stat.vs_space;

    svd->vdev_stat.vs_alloc = 0;
    svd->vdev_stat.vs_space = 0;

    for (t = 0; t < TXG_SIZE; t++) {
        while ((msp = txg_list_remove(&svd->vdev_ms_list, t)) != NULL)
            (void) txg_list_add(&tvd->vdev_ms_list, msp, t);
        while ((vd = txg_list_remove(&svd->vdev_dtl_list, t)) != NULL)
            (void) txg_list_add(&tvd->vdev_dtl_list, vd, t);
        if (txg_list_remove_this(&spa->spa_vdev_txg_list, svd, t))
            (void) txg_list_add(&spa->spa_vdev_txg_list, tvd, t);
        tvd->vdev_dirty[t] = svd->vdev_dirty[t];
        svd->vdev_dirty[t] = 0;
    }

    if (svd->vdev_is_dirty) {
        vdev_config_clean(svd);
        vdev_config_dirty(tvd);
    }

    tvd->vdev_reopen_wanted = svd->vdev_reopen_wanted;
    svd->vdev_reopen_wanted = 0;
}

static void
vdev_top_update(vdev_t *tvd, vdev_t *vd)
{
    int c;

    if (vd == NULL)
        return;

    vd->vdev_top = tvd;

    for (c = 0; c < vd->vdev_children; c++)
        vdev_top_update(tvd, vd->vdev_child[c]);
}

/*
 * Add a mirror/replacing vdev above an existing vdev.
 */
vdev_t *
vdev_add_parent(vdev_t *cvd, vdev_ops_t *ops)
{
    spa_t *spa = cvd->vdev_spa;
    vdev_t *pvd = cvd->vdev_parent;
    vdev_t *mvd;

    ASSERT(spa_config_held(spa, RW_WRITER));

    mvd = vdev_alloc_common(spa, cvd->vdev_id, 0, ops);
    vdev_remove_child(pvd, cvd);
    vdev_add_child(pvd, mvd);
    cvd->vdev_id = mvd->vdev_children;
    vdev_add_child(mvd, cvd);
    vdev_top_update(cvd->vdev_top, cvd->vdev_top);

    mvd->vdev_asize = cvd->vdev_asize;
    mvd->vdev_ashift = cvd->vdev_ashift;
    mvd->vdev_state = cvd->vdev_state;

    if (mvd == mvd->vdev_top)
        vdev_top_transfer(cvd, mvd);

    return (mvd);
}

/*
 * Remove a 1-way mirror/replacing vdev from the tree.
 */
void
vdev_remove_parent(vdev_t *cvd)
{
    vdev_t *mvd = cvd->vdev_parent;
    vdev_t *pvd = mvd->vdev_parent;

    ASSERT(spa_config_held(cvd->vdev_spa, RW_WRITER));

    ASSERT(mvd->vdev_children == 1);
    ASSERT(mvd->vdev_ops == &vdev_mirror_ops ||
        mvd->vdev_ops == &vdev_replacing_ops);

    vdev_remove_child(mvd, cvd);
    vdev_remove_child(pvd, mvd);
    cvd->vdev_id = mvd->vdev_id;
    vdev_add_child(pvd, cvd);
    vdev_top_update(cvd->vdev_top, cvd->vdev_top);

    if (cvd == cvd->vdev_top)
        vdev_top_transfer(mvd, cvd);

    ASSERT(mvd->vdev_children == 0);
    vdev_free(mvd);
}

int
vdev_metaslab_init(vdev_t *vd, uint64_t txg)
{
    spa_t *spa = vd->vdev_spa;
    metaslab_class_t *mc = spa_metaslab_class_select(spa);
    uint64_t c;
    uint64_t oldc = vd->vdev_ms_count;
    uint64_t newc = vd->vdev_asize >> vd->vdev_ms_shift;
    space_map_obj_t *smo = vd->vdev_smo;
    metaslab_t **mspp = vd->vdev_ms;
    int ret;

    if (vd->vdev_ms_shift == 0) /* not being allocated from yet */
        return (0);

    dprintf("%s oldc %llu newc %llu\n", vdev_description(vd), oldc, newc);

    ASSERT(oldc <= newc);

    vd->vdev_smo = kmem_zalloc(newc * sizeof (*smo), KM_SLEEP);
    vd->vdev_ms = kmem_zalloc(newc * sizeof (*mspp), KM_SLEEP);
    vd->vdev_ms_count = newc;

    if (vd->vdev_mg == NULL) {
        if (txg == 0) {
            dmu_buf_t *db;
            uint64_t *ms_array;

            ms_array = kmem_zalloc(newc * sizeof (uint64_t),
                KM_SLEEP);

            if ((ret = dmu_read(spa->spa_meta_objset,
                vd->vdev_ms_array, 0,
                newc * sizeof (uint64_t), ms_array)) != 0) {
                kmem_free(ms_array, newc * sizeof (uint64_t));
                goto error;
            }

            for (c = 0; c < newc; c++) {
                if (ms_array[c] == 0)
                    continue;
                if ((ret = dmu_bonus_hold(
                    spa->spa_meta_objset, ms_array[c],
                    FTAG, &db)) != 0) {
                    kmem_free(ms_array,
                        newc * sizeof (uint64_t));
                    goto error;
                }
                ASSERT3U(db->db_size, ==, sizeof (*smo));
                bcopy(db->db_data, &vd->vdev_smo[c],
                    db->db_size);
                ASSERT3U(vd->vdev_smo[c].smo_object, ==,
                    ms_array[c]);
                dmu_buf_rele(db, FTAG);
            }
            kmem_free(ms_array, newc * sizeof (uint64_t));
        }
        vd->vdev_mg = metaslab_group_create(mc, vd);
    }

    for (c = 0; c < oldc; c++) {
        vd->vdev_smo[c] = smo[c];
        vd->vdev_ms[c] = mspp[c];
        mspp[c]->ms_smo = &vd->vdev_smo[c];
    }

    for (c = oldc; c < newc; c++)
        metaslab_init(vd->vdev_mg, &vd->vdev_smo[c], &vd->vdev_ms[c],
            c << vd->vdev_ms_shift, 1ULL << vd->vdev_ms_shift, txg);

    if (oldc != 0) {
        kmem_free(smo, oldc * sizeof (*smo));
        kmem_free(mspp, oldc * sizeof (*mspp));
    }

    return (0);

error:
    /*
     * On error, undo any partial progress we may have made, and restore the
     * old metaslab values.
     */
    kmem_free(vd->vdev_smo, newc * sizeof (*smo));
    kmem_free(vd->vdev_ms, newc * sizeof (*mspp));

    vd->vdev_smo = smo;
    vd->vdev_ms = mspp;
    vd->vdev_ms_count = oldc;

    return (ret);
}

void
vdev_metaslab_fini(vdev_t *vd)
{
    uint64_t m;
    uint64_t count = vd->vdev_ms_count;

    if (vd->vdev_ms != NULL) {
        for (m = 0; m < count; m++)
            metaslab_fini(vd->vdev_ms[m]);
        kmem_free(vd->vdev_ms, count * sizeof (metaslab_t *));
        vd->vdev_ms = NULL;
    }

    if (vd->vdev_smo != NULL) {
        kmem_free(vd->vdev_smo, count * sizeof (space_map_obj_t));
        vd->vdev_smo = NULL;
    }
}

/*
 * Prepare a virtual device for access.
 */
int
vdev_open(vdev_t *vd)
{
    int error;
    vdev_knob_t *vk;
    int c;
    uint64_t osize = 0;
    uint64_t asize, psize;
    uint64_t ashift = -1ULL;

    ASSERT(vd->vdev_state == VDEV_STATE_CLOSED ||
        vd->vdev_state == VDEV_STATE_CANT_OPEN ||
        vd->vdev_state == VDEV_STATE_OFFLINE);

    if (vd->vdev_fault_mode == VDEV_FAULT_COUNT)
        vd->vdev_fault_arg >>= 1;
    else
        vd->vdev_fault_mode = VDEV_FAULT_NONE;

    vd->vdev_stat.vs_aux = VDEV_AUX_NONE;

    for (vk = vdev_knob_next(NULL); vk != NULL; vk = vdev_knob_next(vk)) {
        uint64_t *valp = (uint64_t *)((char *)vd + vk->vk_offset);

        *valp = vk->vk_default;
        *valp = MAX(*valp, vk->vk_min);
        *valp = MIN(*valp, vk->vk_max);
    }

    if (vd->vdev_ops->vdev_op_leaf) {
        vdev_cache_init(vd);
        vdev_queue_init(vd);
        vd->vdev_cache_active = B_TRUE;
    }

    if (vd->vdev_offline) {
        ASSERT(vd->vdev_children == 0);
        vdev_set_state(vd, B_TRUE, VDEV_STATE_OFFLINE, VDEV_AUX_NONE);
        return (ENXIO);
    }

    error = vd->vdev_ops->vdev_op_open(vd, &osize, &ashift);

    if (zio_injection_enabled && error == 0)
        error = zio_handle_device_injection(vd, ENXIO);

    dprintf("%s = %d, osize %llu, state = %d\n",
        vdev_description(vd), error, osize, vd->vdev_state);

    if (error) {
        vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
            vd->vdev_stat.vs_aux);
        return (error);
    }

    vd->vdev_state = VDEV_STATE_HEALTHY;

    for (c = 0; c < vd->vdev_children; c++)
        if (vd->vdev_child[c]->vdev_state != VDEV_STATE_HEALTHY) {
            vdev_set_state(vd, B_TRUE, VDEV_STATE_DEGRADED,
                VDEV_AUX_NONE);
            break;
        }

    osize = P2ALIGN(osize, (uint64_t)sizeof (vdev_label_t));

    if (vd->vdev_children == 0) {
        if (osize < SPA_MINDEVSIZE) {
            vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_TOO_SMALL);
            return (EOVERFLOW);
        }
        psize = osize;
        asize = osize - (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE);
    } else {
        if (osize < SPA_MINDEVSIZE -
            (VDEV_LABEL_START_SIZE + VDEV_LABEL_END_SIZE)) {
            vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_TOO_SMALL);
            return (EOVERFLOW);
        }
        psize = 0;
        asize = osize;
    }

    vd->vdev_psize = psize;

    if (vd->vdev_asize == 0) {
        /*
         * This is the first-ever open, so use the computed values.
         */
        vd->vdev_asize = asize;
        vd->vdev_ashift = ashift;
    } else {
        /*
         * Make sure the alignment requirement hasn't increased.
         */
        if (ashift > vd->vdev_ashift) {
            vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_BAD_LABEL);
            return (EINVAL);
        }

        /*
         * Make sure the device hasn't shrunk.
         */
        if (asize < vd->vdev_asize) {
            vdev_set_state(vd, B_TRUE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_BAD_LABEL);
            return (EINVAL);
        }

        /*
         * If all children are healthy and the asize has increased,
         * then we've experienced dynamic LUN growth.
         */
        if (vd->vdev_state == VDEV_STATE_HEALTHY &&
            asize > vd->vdev_asize) {
            vd->vdev_asize = asize;
        }
    }

    /*
     * If we were able to open a vdev that was marked permanently
     * unavailable, clear that state now.
     */
    if (vd->vdev_not_present)
        vd->vdev_not_present = 0;

    /*
     * This allows the ZFS DE to close cases appropriately.  If a device
     * goes away and later returns, we want to close the associated case.
     * But it's not enough to simply post this only when a device goes from
     * CANT_OPEN -> HEALTHY.  If we reboot the system and the device is
     * back, we also need to close the case (otherwise we will try to replay
     * it).  So we have to post this notifier every time.  Since this only
     * occurs during pool open or error recovery, this should not be an
     * issue.
     */
    zfs_post_ok(vd->vdev_spa, vd);

    return (0);
}

/*
 * Close a virtual device.
 */
void
vdev_close(vdev_t *vd)
{
    vd->vdev_ops->vdev_op_close(vd);

    if (vd->vdev_cache_active) {
        vdev_cache_fini(vd);
        vdev_queue_fini(vd);
        vd->vdev_cache_active = B_FALSE;
    }

    if (vd->vdev_offline)
        vd->vdev_state = VDEV_STATE_OFFLINE;
    else
        vd->vdev_state = VDEV_STATE_CLOSED;
    vd->vdev_stat.vs_aux = VDEV_AUX_NONE;
}

void
vdev_reopen(vdev_t *vd)
{
    spa_t *spa = vd->vdev_spa;
    vdev_t *rvd = spa->spa_root_vdev;
    int c;

    ASSERT(spa_config_held(spa, RW_WRITER));

    if (vd == rvd) {
        for (c = 0; c < rvd->vdev_children; c++)
            vdev_reopen(rvd->vdev_child[c]);
        return;
    }

    /* only valid for top-level vdevs */
    ASSERT3P(vd, ==, vd->vdev_top);

    vdev_close(vd);
    (void) vdev_open(vd);

    /*
     * Reassess root vdev's health.
     */
    rvd->vdev_state = VDEV_STATE_HEALTHY;
    for (c = 0; c < rvd->vdev_children; c++) {
        uint64_t state = rvd->vdev_child[c]->vdev_state;
        rvd->vdev_state = MIN(rvd->vdev_state, state);
    }
}

int
vdev_create(vdev_t *vd, uint64_t txg)
{
    int error;

    /*
     * Normally, partial opens (e.g. of a mirror) are allowed.
     * For a create, however, we want to fail the request if
     * there are any components we can't open.
     */
    error = vdev_open(vd);

    if (error || vd->vdev_state != VDEV_STATE_HEALTHY) {
        vdev_close(vd);
        return (error ? error : ENXIO);
    }

    /*
     * Recursively initialize all labels.
     */
    if ((error = vdev_label_init(vd, txg)) != 0) {
        vdev_close(vd);
        return (error);
    }

    return (0);
}

/*
 * The is the latter half of vdev_create().  It is distinct because it
 * involves initiating transactions in order to do metaslab creation.
 * For creation, we want to try to create all vdevs at once and then undo it
 * if anything fails; this is much harder if we have pending transactions.
 */
void
vdev_init(vdev_t *vd, uint64_t txg)
{
    /*
     * Aim for roughly 200 metaslabs per vdev.
     */
    vd->vdev_ms_shift = highbit(vd->vdev_asize / 200);
    vd->vdev_ms_shift = MAX(vd->vdev_ms_shift, SPA_MAXBLOCKSHIFT);

    /*
     * Initialize the vdev's metaslabs.  This can't fail because
     * there's nothing to read when creating all new metaslabs.
     */
    VERIFY(vdev_metaslab_init(vd, txg) == 0);
}

void
vdev_dirty(vdev_t *vd, uint8_t flags, uint64_t txg)
{
    vdev_t *tvd = vd->vdev_top;

    mutex_enter(&tvd->vdev_dirty_lock);
    if ((tvd->vdev_dirty[txg & TXG_MASK] & flags) != flags) {
        tvd->vdev_dirty[txg & TXG_MASK] |= flags;
        (void) txg_list_add(&tvd->vdev_spa->spa_vdev_txg_list,
            tvd, txg);
    }
    mutex_exit(&tvd->vdev_dirty_lock);
}

void
vdev_dtl_dirty(space_map_t *sm, uint64_t txg, uint64_t size)
{
    mutex_enter(sm->sm_lock);
    if (!space_map_contains(sm, txg, size))
        space_map_add(sm, txg, size);
    mutex_exit(sm->sm_lock);
}

int
vdev_dtl_contains(space_map_t *sm, uint64_t txg, uint64_t size)
{
    int dirty;

    /*
     * Quick test without the lock -- covers the common case that
     * there are no dirty time segments.
     */
    if (sm->sm_space == 0)
        return (0);

    mutex_enter(sm->sm_lock);
    dirty = space_map_contains(sm, txg, size);
    mutex_exit(sm->sm_lock);

    return (dirty);
}

/*
 * Reassess DTLs after a config change or scrub completion.
 */
void
vdev_dtl_reassess(vdev_t *vd, uint64_t txg, uint64_t scrub_txg, int scrub_done)
{
    spa_t *spa = vd->vdev_spa;
    int c;

    ASSERT(spa_config_held(spa, RW_WRITER));

    if (vd->vdev_children == 0) {
        mutex_enter(&vd->vdev_dtl_lock);
        /*
         * We're successfully scrubbed everything up to scrub_txg.
         * Therefore, excise all old DTLs up to that point, then
         * fold in the DTLs for everything we couldn't scrub.
         */
        if (scrub_txg != 0) {
            space_map_excise(&vd->vdev_dtl_map, 0, scrub_txg);
            space_map_union(&vd->vdev_dtl_map, &vd->vdev_dtl_scrub);
        }
        if (scrub_done)
            space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
        mutex_exit(&vd->vdev_dtl_lock);
        if (txg != 0) {
            vdev_t *tvd = vd->vdev_top;
            vdev_dirty(tvd, VDD_DTL, txg);
            (void) txg_list_add(&tvd->vdev_dtl_list, vd, txg);
        }
        return;
    }

    /*
     * Make sure the DTLs are always correct under the scrub lock.
     */
    if (vd == spa->spa_root_vdev)
        mutex_enter(&spa->spa_scrub_lock);

    mutex_enter(&vd->vdev_dtl_lock);
    space_map_vacate(&vd->vdev_dtl_map, NULL, NULL);
    space_map_vacate(&vd->vdev_dtl_scrub, NULL, NULL);
    mutex_exit(&vd->vdev_dtl_lock);

    for (c = 0; c < vd->vdev_children; c++) {
        vdev_t *cvd = vd->vdev_child[c];
        vdev_dtl_reassess(cvd, txg, scrub_txg, scrub_done);
        mutex_enter(&vd->vdev_dtl_lock);
        space_map_union(&vd->vdev_dtl_map, &cvd->vdev_dtl_map);
        space_map_union(&vd->vdev_dtl_scrub, &cvd->vdev_dtl_scrub);
        mutex_exit(&vd->vdev_dtl_lock);
    }

    if (vd == spa->spa_root_vdev)
        mutex_exit(&spa->spa_scrub_lock);
}

static int
vdev_dtl_load(vdev_t *vd)
{
    spa_t *spa = vd->vdev_spa;
    space_map_obj_t *smo = &vd->vdev_dtl;
    dmu_buf_t *db;
    int error;

    ASSERT(vd->vdev_children == 0);

    if (smo->smo_object == 0)
        return (0);

    if ((error = dmu_bonus_hold(spa->spa_meta_objset, smo->smo_object,
        FTAG, &db)) != 0)
        return (error);
    ASSERT3U(db->db_size, ==, sizeof (*smo));
    bcopy(db->db_data, smo, db->db_size);
    dmu_buf_rele(db, FTAG);

    mutex_enter(&vd->vdev_dtl_lock);
    error = space_map_load(&vd->vdev_dtl_map, smo, SM_ALLOC,
        spa->spa_meta_objset, smo->smo_objsize, smo->smo_alloc);
    mutex_exit(&vd->vdev_dtl_lock);

    return (error);
}

void
vdev_dtl_sync(vdev_t *vd, uint64_t txg)
{
    spa_t *spa = vd->vdev_spa;
    space_map_obj_t *smo = &vd->vdev_dtl;
    space_map_t *sm = &vd->vdev_dtl_map;
    space_map_t smsync;
    kmutex_t smlock;
    avl_tree_t *t = &sm->sm_root;
    space_seg_t *ss;
    dmu_buf_t *db;
    dmu_tx_t *tx;

    dprintf("%s in txg %llu pass %d\n",
        vdev_description(vd), (u_longlong_t)txg, spa_sync_pass(spa));

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

    if (vd->vdev_detached) {
        if (smo->smo_object != 0) {
            int err = dmu_object_free(spa->spa_meta_objset,
                smo->smo_object, tx);
            ASSERT3U(err, ==, 0);
            smo->smo_object = 0;
        }
        dmu_tx_commit(tx);
        return;
    }

    if (smo->smo_object == 0) {
        ASSERT(smo->smo_objsize == 0);
        ASSERT(smo->smo_alloc == 0);
        smo->smo_object = dmu_object_alloc(spa->spa_meta_objset,
            DMU_OT_SPACE_MAP, 1 << SPACE_MAP_BLOCKSHIFT,
            DMU_OT_SPACE_MAP_HEADER, sizeof (*smo), tx);
        ASSERT(smo->smo_object != 0);
        vdev_config_dirty(vd->vdev_top);
    }

    VERIFY(0 == dmu_free_range(spa->spa_meta_objset, smo->smo_object,
        0, smo->smo_objsize, tx));

    mutex_init(&smlock, NULL, MUTEX_DEFAULT, NULL);

    space_map_create(&smsync, sm->sm_start, sm->sm_size, sm->sm_shift,
        &smlock);

    mutex_enter(&smlock);

    mutex_enter(&vd->vdev_dtl_lock);
    for (ss = avl_first(t); ss != NULL; ss = AVL_NEXT(t, ss))
        space_map_add(&smsync, ss->ss_start, ss->ss_end - ss->ss_start);
    mutex_exit(&vd->vdev_dtl_lock);

    smo->smo_objsize = 0;
    smo->smo_alloc = smsync.sm_space;

    space_map_sync(&smsync, NULL, smo, SM_ALLOC, spa->spa_meta_objset, tx);
    space_map_destroy(&smsync);

    mutex_exit(&smlock);
    mutex_destroy(&smlock);

    VERIFY(0 == dmu_bonus_hold(spa->spa_meta_objset, smo->smo_object,
        FTAG, &db));
    dmu_buf_will_dirty(db, tx);
    ASSERT3U(db->db_size, ==, sizeof (*smo));
    bcopy(smo, db->db_data, db->db_size);
    dmu_buf_rele(db, FTAG);

    dmu_tx_commit(tx);
}

int
vdev_load(vdev_t *vd)
{
    spa_t *spa = vd->vdev_spa;
    int c, error;
    nvlist_t *label;
    uint64_t guid, state;

    dprintf("loading %s\n", vdev_description(vd));

    /*
     * Recursively load all children.
     */
    for (c = 0; c < vd->vdev_children; c++)
        if ((error = vdev_load(vd->vdev_child[c])) != 0)
            return (error);

    /*
     * If this is a leaf vdev, make sure its agrees with its disk labels.
     */
    if (vd->vdev_ops->vdev_op_leaf) {

        if (vdev_is_dead(vd))
            return (0);

        /*
         * XXX state transitions don't propagate to parent here.
         * Also, merely setting the state isn't sufficient because
         * it's not persistent; a vdev_reopen() would make us
         * forget all about it.
         */
        if ((label = vdev_label_read_config(vd)) == NULL) {
            dprintf("can't load label config\n");
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            return (0);
        }

        if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID,
            &guid) != 0 || guid != spa_guid(spa)) {
            dprintf("bad or missing pool GUID (%llu)\n", guid);
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            nvlist_free(label);
            return (0);
        }

        if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &guid) ||
            guid != vd->vdev_guid) {
            dprintf("bad or missing vdev guid (%llu != %llu)\n",
                guid, vd->vdev_guid);
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            nvlist_free(label);
            return (0);
        }

        /*
         * If we find a vdev with a matching pool guid and vdev guid,
         * but the pool state is not active, it indicates that the user
         * exported or destroyed the pool without affecting the config
         * cache (if / was mounted readonly, for example).  In this
         * case, immediately return EBADF so the caller can remove it
         * from the config.
         */
        if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
            &state)) {
            dprintf("missing pool state\n");
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            nvlist_free(label);
            return (0);
        }

        if (state != POOL_STATE_ACTIVE &&
            (spa->spa_load_state == SPA_LOAD_OPEN ||
            state != POOL_STATE_EXPORTED)) {
            dprintf("pool state not active (%llu)\n", state);
            nvlist_free(label);
            return (EBADF);
        }

        nvlist_free(label);
    }

    /*
     * If this is a top-level vdev, initialize its metaslabs.
     */
    if (vd == vd->vdev_top) {

        if (vd->vdev_ashift == 0 || vd->vdev_asize == 0) {
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            return (0);
        }

        if ((error = vdev_metaslab_init(vd, 0)) != 0) {
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            return (0);
        }
    }

    /*
     * If this is a leaf vdev, load its DTL.
     */
    if (vd->vdev_ops->vdev_op_leaf) {
        error = vdev_dtl_load(vd);
        if (error) {
            dprintf("can't load DTL for %s, error %d\n",
                vdev_description(vd), error);
            vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
            return (0);
        }
    }

    return (0);
}

void
vdev_sync_done(vdev_t *vd, uint64_t txg)
{
    metaslab_t *msp;

    dprintf("%s txg %llu\n", vdev_description(vd), txg);

    while (msp = txg_list_remove(&vd->vdev_ms_list, TXG_CLEAN(txg)))
        metaslab_sync_done(msp, txg);
}

void
vdev_add_sync(vdev_t *vd, uint64_t txg)
{
    spa_t *spa = vd->vdev_spa;
    dmu_tx_t *tx = dmu_tx_create_assigned(spa->spa_dsl_pool, txg);

    ASSERT(vd == vd->vdev_top);

    if (vd->vdev_ms_array == 0)
        vd->vdev_ms_array = dmu_object_alloc(spa->spa_meta_objset,
            DMU_OT_OBJECT_ARRAY, 0, DMU_OT_NONE, 0, tx);

    ASSERT(vd->vdev_ms_array != 0);

    vdev_config_dirty(vd);

    dmu_tx_commit(tx);
}

void
vdev_sync(vdev_t *vd, uint64_t txg)
{
    spa_t *spa = vd->vdev_spa;
    vdev_t *lvd;
    metaslab_t *msp;
    uint8_t *dirtyp = &vd->vdev_dirty[txg & TXG_MASK];
    uint8_t dirty = *dirtyp;

    mutex_enter(&vd->vdev_dirty_lock);
    *dirtyp &= ~(VDD_ALLOC | VDD_FREE | VDD_ADD | VDD_DTL);
    mutex_exit(&vd->vdev_dirty_lock);

    dprintf("%s txg %llu pass %d\n",
        vdev_description(vd), (u_longlong_t)txg, spa_sync_pass(spa));

    if (dirty & VDD_ADD)
        vdev_add_sync(vd, txg);

    while ((msp = txg_list_remove(&vd->vdev_ms_list, txg)) != NULL)
        metaslab_sync(msp, txg);

    while ((lvd = txg_list_remove(&vd->vdev_dtl_list, txg)) != NULL)
        vdev_dtl_sync(lvd, txg);

    (void) txg_list_add(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg));
}

uint64_t
vdev_psize_to_asize(vdev_t *vd, uint64_t psize)
{
    return (vd->vdev_ops->vdev_op_asize(vd, psize));
}

void
vdev_io_start(zio_t *zio)
{
    zio->io_vd->vdev_ops->vdev_op_io_start(zio);
}

void
vdev_io_done(zio_t *zio)
{
    zio->io_vd->vdev_ops->vdev_op_io_done(zio);
}

const char *
vdev_description(vdev_t *vd)
{
    if (vd == NULL || vd->vdev_ops == NULL)
        return ("<unknown>");

    if (vd->vdev_path != NULL)
        return (vd->vdev_path);

    if (vd->vdev_parent == NULL)
        return (spa_name(vd->vdev_spa));

    return (vd->vdev_ops->vdev_op_type);
}

int
vdev_online(spa_t *spa, uint64_t guid)
{
    vdev_t *rvd, *vd;
    uint64_t txg;

    txg = spa_vdev_enter(spa);

    rvd = spa->spa_root_vdev;

    if ((vd = vdev_lookup_by_guid(rvd, guid)) == NULL)
        return (spa_vdev_exit(spa, NULL, txg, ENODEV));

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

    dprintf("ONLINE: %s\n", vdev_description(vd));

    vd->vdev_offline = B_FALSE;
    vd->vdev_tmpoffline = B_FALSE;
    vdev_reopen(vd->vdev_top);

    vdev_config_dirty(vd->vdev_top);

    (void) spa_vdev_exit(spa, NULL, txg, 0);

    VERIFY(spa_scrub(spa, POOL_SCRUB_RESILVER, B_TRUE) == 0);

    return (0);
}

int
vdev_offline(spa_t *spa, uint64_t guid, int istmp)
{
    vdev_t *rvd, *vd;
    uint64_t txg;

    txg = spa_vdev_enter(spa);

    rvd = spa->spa_root_vdev;

    if ((vd = vdev_lookup_by_guid(rvd, guid)) == NULL)
        return (spa_vdev_exit(spa, NULL, txg, ENODEV));

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

    dprintf("OFFLINE: %s\n", vdev_description(vd));

    /* vdev is already offlined, do nothing */
    if (vd->vdev_offline)
        return (spa_vdev_exit(spa, NULL, txg, 0));

    /*
     * If this device's top-level vdev has a non-empty DTL,
     * don't allow the device to be offlined.
     *
     * XXX -- we should make this more precise by allowing the offline
     * as long as the remaining devices don't have any DTL holes.
     */
    if (vd->vdev_top->vdev_dtl_map.sm_space != 0)
        return (spa_vdev_exit(spa, NULL, txg, EBUSY));

    /*
     * Set this device to offline state and reopen its top-level vdev.
     * If this action results in the top-level vdev becoming unusable,
     * undo it and fail the request.
     */
    vd->vdev_offline = B_TRUE;
    vdev_reopen(vd->vdev_top);
    if (vdev_is_dead(vd->vdev_top)) {
        vd->vdev_offline = B_FALSE;
        vdev_reopen(vd->vdev_top);
        return (spa_vdev_exit(spa, NULL, txg, EBUSY));
    }

    vd->vdev_tmpoffline = istmp;
    if (!istmp)
        vdev_config_dirty(vd->vdev_top);

    return (spa_vdev_exit(spa, NULL, txg, 0));
}

/*
 * Clear the error counts associated with this vdev.  Unlike vdev_online() and
 * vdev_offline(), we assume the spa config is locked.  We also clear all
 * children.  If 'vd' is NULL, then the user wants to clear all vdevs.
 */
void
vdev_clear(spa_t *spa, vdev_t *vd)
{
    int c;

    if (vd == NULL)
        vd = spa->spa_root_vdev;

    vd->vdev_stat.vs_read_errors = 0;
    vd->vdev_stat.vs_write_errors = 0;
    vd->vdev_stat.vs_checksum_errors = 0;

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

int
vdev_is_dead(vdev_t *vd)
{
    return (vd->vdev_state <= VDEV_STATE_CANT_OPEN);
}

int
vdev_error_inject(vdev_t *vd, zio_t *zio)
{
    int error = 0;

    if (vd->vdev_fault_mode == VDEV_FAULT_NONE)
        return (0);

    if (((1ULL << zio->io_type) & vd->vdev_fault_mask) == 0)
        return (0);

    switch (vd->vdev_fault_mode) {
    case VDEV_FAULT_RANDOM:
        if (spa_get_random(vd->vdev_fault_arg) == 0)
            error = EIO;
        break;

    case VDEV_FAULT_COUNT:
        if ((int64_t)--vd->vdev_fault_arg <= 0)
            vd->vdev_fault_mode = VDEV_FAULT_NONE;
        error = EIO;
        break;
    }

    if (error != 0) {
        dprintf("returning %d for type %d on %s state %d offset %llx\n",
            error, zio->io_type, vdev_description(vd),
            vd->vdev_state, zio->io_offset);
    }

    return (error);
}

/*
 * Get statistics for the given vdev.
 */
void
vdev_get_stats(vdev_t *vd, vdev_stat_t *vs)
{
    vdev_t *rvd = vd->vdev_spa->spa_root_vdev;
    int c, t;

    mutex_enter(&vd->vdev_stat_lock);
    bcopy(&vd->vdev_stat, vs, sizeof (*vs));
    vs->vs_timestamp = gethrtime() - vs->vs_timestamp;
    vs->vs_state = vd->vdev_state;
    vs->vs_rsize = vdev_get_rsize(vd);
    mutex_exit(&vd->vdev_stat_lock);

    /*
     * If we're getting stats on the root vdev, aggregate the I/O counts
     * over all top-level vdevs (i.e. the direct children of the root).
     */
    if (vd == rvd) {
        for (c = 0; c < rvd->vdev_children; c++) {
            vdev_t *cvd = rvd->vdev_child[c];
            vdev_stat_t *cvs = &cvd->vdev_stat;

            mutex_enter(&vd->vdev_stat_lock);
            for (t = 0; t < ZIO_TYPES; t++) {
                vs->vs_ops[t] += cvs->vs_ops[t];
                vs->vs_bytes[t] += cvs->vs_bytes[t];
            }
            vs->vs_read_errors += cvs->vs_read_errors;
            vs->vs_write_errors += cvs->vs_write_errors;
            vs->vs_checksum_errors += cvs->vs_checksum_errors;
            vs->vs_scrub_examined += cvs->vs_scrub_examined;
            vs->vs_scrub_errors += cvs->vs_scrub_errors;
            mutex_exit(&vd->vdev_stat_lock);
        }
    }
}

void
vdev_stat_update(zio_t *zio)
{
    vdev_t *vd = zio->io_vd;
    vdev_t *pvd;
    uint64_t txg = zio->io_txg;
    vdev_stat_t *vs = &vd->vdev_stat;
    zio_type_t type = zio->io_type;
    int flags = zio->io_flags;

    if (zio->io_error == 0) {
        if (!(flags & ZIO_FLAG_IO_BYPASS)) {
            mutex_enter(&vd->vdev_stat_lock);
            vs->vs_ops[type]++;
            vs->vs_bytes[type] += zio->io_size;
            mutex_exit(&vd->vdev_stat_lock);
        }
        if ((flags & ZIO_FLAG_IO_REPAIR) &&
            zio->io_delegate_list == NULL) {
            mutex_enter(&vd->vdev_stat_lock);
            if (flags & (ZIO_FLAG_SCRUB | ZIO_FLAG_RESILVER))
                vs->vs_scrub_repaired += zio->io_size;
            else
                vs->vs_self_healed += zio->io_size;
            mutex_exit(&vd->vdev_stat_lock);
        }
        return;
    }

    if (flags & ZIO_FLAG_SPECULATIVE)
        return;

    if (!vdev_is_dead(vd)) {
        mutex_enter(&vd->vdev_stat_lock);
        if (type == ZIO_TYPE_READ) {
            if (zio->io_error == ECKSUM)
                vs->vs_checksum_errors++;
            else
                vs->vs_read_errors++;
        }
        if (type == ZIO_TYPE_WRITE)
            vs->vs_write_errors++;
        mutex_exit(&vd->vdev_stat_lock);
    }

    if (type == ZIO_TYPE_WRITE) {
        if (txg == 0 || vd->vdev_children != 0)
            return;
        if (flags & (ZIO_FLAG_SCRUB | ZIO_FLAG_RESILVER)) {
            ASSERT(flags & ZIO_FLAG_IO_REPAIR);
            for (pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
                vdev_dtl_dirty(&pvd->vdev_dtl_scrub, txg, 1);
        }
        if (!(flags & ZIO_FLAG_IO_REPAIR)) {
            vdev_t *tvd = vd->vdev_top;
            if (vdev_dtl_contains(&vd->vdev_dtl_map, txg, 1))
                return;
            vdev_dirty(tvd, VDD_DTL, txg);
            (void) txg_list_add(&tvd->vdev_dtl_list, vd, txg);
            for (pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
                vdev_dtl_dirty(&pvd->vdev_dtl_map, txg, 1);
        }
    }
}

void
vdev_scrub_stat_update(vdev_t *vd, pool_scrub_type_t type, boolean_t complete)
{
    int c;
    vdev_stat_t *vs = &vd->vdev_stat;

    for (c = 0; c < vd->vdev_children; c++)
        vdev_scrub_stat_update(vd->vdev_child[c], type, complete);

    mutex_enter(&vd->vdev_stat_lock);

    if (type == POOL_SCRUB_NONE) {
        /*
         * Update completion and end time.  Leave everything else alone
         * so we can report what happened during the previous scrub.
         */
        vs->vs_scrub_complete = complete;
        vs->vs_scrub_end = gethrestime_sec();
    } else {
        vs->vs_scrub_type = type;
        vs->vs_scrub_complete = 0;
        vs->vs_scrub_examined = 0;
        vs->vs_scrub_repaired = 0;
        vs->vs_scrub_errors = 0;
        vs->vs_scrub_start = gethrestime_sec();
        vs->vs_scrub_end = 0;
    }

    mutex_exit(&vd->vdev_stat_lock);
}

/*
 * Update the in-core space usage stats for this vdev and the root vdev.
 */
void
vdev_space_update(vdev_t *vd, uint64_t space_delta, uint64_t alloc_delta)
{
    ASSERT(vd == vd->vdev_top);

    do {
        mutex_enter(&vd->vdev_stat_lock);
        vd->vdev_stat.vs_space += space_delta;
        vd->vdev_stat.vs_alloc += alloc_delta;
        mutex_exit(&vd->vdev_stat_lock);
    } while ((vd = vd->vdev_parent) != NULL);
}

/*
 * Various knobs to tune a vdev.
 */
static vdev_knob_t vdev_knob[] = {
    {
        "cache_size",
        "size of the read-ahead cache",
        0,
        1ULL << 30,
        10ULL << 20,
        offsetof(struct vdev, vdev_cache.vc_size)
    },
    {
        "cache_bshift",
        "log2 of cache blocksize",
        SPA_MINBLOCKSHIFT,
        SPA_MAXBLOCKSHIFT,
        16,
        offsetof(struct vdev, vdev_cache.vc_bshift)
    },
    {
        "cache_max",
        "largest block size to cache",
        0,
        SPA_MAXBLOCKSIZE,
        1ULL << 14,
        offsetof(struct vdev, vdev_cache.vc_max)
    },
    {
        "min_pending",
        "minimum pending I/Os to the disk",
        1,
        10000,
        2,
        offsetof(struct vdev, vdev_queue.vq_min_pending)
    },
    {
        "max_pending",
        "maximum pending I/Os to the disk",
        1,
        10000,
        35,
        offsetof(struct vdev, vdev_queue.vq_max_pending)
    },
    {
        "scrub_limit",
        "maximum scrub/resilver I/O queue",
        0,
        10000,
        70,
        offsetof(struct vdev, vdev_queue.vq_scrub_limit)
    },
    {
        "agg_limit",
        "maximum size of aggregated I/Os",
        0,
        SPA_MAXBLOCKSIZE,
        SPA_MAXBLOCKSIZE,
        offsetof(struct vdev, vdev_queue.vq_agg_limit)
    },
    {
        "time_shift",
        "deadline = pri + (lbolt >> time_shift)",
        0,
        63,
        4,
        offsetof(struct vdev, vdev_queue.vq_time_shift)
    },
    {
        "ramp_rate",
        "exponential I/O issue ramp-up rate",
        1,
        10000,
        2,
        offsetof(struct vdev, vdev_queue.vq_ramp_rate)
    },
};

vdev_knob_t *
vdev_knob_next(vdev_knob_t *vk)
{
    if (vk == NULL)
        return (vdev_knob);

    if (++vk == vdev_knob + sizeof (vdev_knob) / sizeof (vdev_knob_t))
        return (NULL);

    return (vk);
}

/*
 * Mark a top-level vdev's config as dirty, placing it on the dirty list
 * so that it will be written out next time the vdev configuration is synced.
 * If the root vdev is specified (vdev_top == NULL), dirty all top-level vdevs.
 */
void
vdev_config_dirty(vdev_t *vd)
{
    spa_t *spa = vd->vdev_spa;
    vdev_t *rvd = spa->spa_root_vdev;
    int c;

    if (vd == rvd) {
        for (c = 0; c < rvd->vdev_children; c++)
            vdev_config_dirty(rvd->vdev_child[c]);
    } else {
        ASSERT(vd == vd->vdev_top);

        if (!vd->vdev_is_dirty) {
            list_insert_head(&spa->spa_dirty_list, vd);
            vd->vdev_is_dirty = B_TRUE;
        }
    }
}

void
vdev_config_clean(vdev_t *vd)
{
    ASSERT(vd->vdev_is_dirty);

    list_remove(&vd->vdev_spa->spa_dirty_list, vd);
    vd->vdev_is_dirty = B_FALSE;
}

/*
 * Set a vdev's state.  If this is during an open, we don't update the parent
 * state, because we're in the process of opening children depth-first.
 * Otherwise, we propagate the change to the parent.
 *
 * If this routine places a device in a faulted state, an appropriate ereport is
 * generated.
 */
void
vdev_set_state(vdev_t *vd, boolean_t isopen, vdev_state_t state, vdev_aux_t aux)
{
    uint64_t prev_state;

    if (state == vd->vdev_state) {
        vd->vdev_stat.vs_aux = aux;
        return;
    }

    prev_state = vd->vdev_state;

    vd->vdev_state = state;
    vd->vdev_stat.vs_aux = aux;

    if (state == VDEV_STATE_CANT_OPEN) {
        /*
         * If we fail to open a vdev during an import, we mark it as
         * "not available", which signifies that it was never there to
         * begin with.  Failure to open such a device is not considered
         * an error.
         */
        if (!vd->vdev_not_present &&
            vd != vd->vdev_spa->spa_root_vdev) {
            const char *class;

            switch (aux) {
            case VDEV_AUX_OPEN_FAILED:
                class = FM_EREPORT_ZFS_DEVICE_OPEN_FAILED;
                break;
            case VDEV_AUX_CORRUPT_DATA:
                class = FM_EREPORT_ZFS_DEVICE_CORRUPT_DATA;
                break;
            case VDEV_AUX_NO_REPLICAS:
                class = FM_EREPORT_ZFS_DEVICE_NO_REPLICAS;
                break;
            case VDEV_AUX_BAD_GUID_SUM:
                class = FM_EREPORT_ZFS_DEVICE_BAD_GUID_SUM;
                break;
            case VDEV_AUX_TOO_SMALL:
                class = FM_EREPORT_ZFS_DEVICE_TOO_SMALL;
                break;
            case VDEV_AUX_BAD_LABEL:
                class = FM_EREPORT_ZFS_DEVICE_BAD_LABEL;
                break;
            default:
                class = FM_EREPORT_ZFS_DEVICE_UNKNOWN;
            }

            zfs_ereport_post(class, vd->vdev_spa,
                vd, NULL, prev_state, 0);
        }

        if (vd->vdev_spa->spa_load_state == SPA_LOAD_IMPORT &&
            vd->vdev_ops->vdev_op_leaf)
            vd->vdev_not_present = 1;
    }

    if (isopen)
        return;

    if (vd->vdev_parent != NULL) {
        int c;
        int degraded = 0, faulted = 0;
        int corrupted = 0;
        vdev_t *parent, *child;

        parent = vd->vdev_parent;
        for (c = 0; c < parent->vdev_children; c++) {
            child = parent->vdev_child[c];
            if (child->vdev_state <= VDEV_STATE_CANT_OPEN)
                faulted++;
            else if (child->vdev_state == VDEV_STATE_DEGRADED)
                degraded++;

            if (child->vdev_stat.vs_aux == VDEV_AUX_CORRUPT_DATA)
                corrupted++;
        }

        vd->vdev_parent->vdev_ops->vdev_op_state_change(
            vd->vdev_parent, faulted, degraded);

        /*
         * Root special: if this is a toplevel vdev that cannot be
         * opened due to corrupted metadata, then propagate the root
         * vdev's aux state as 'corrupt' rather than 'insufficient
         * replicas'.
         */
        if (corrupted && vd == vd->vdev_top)
            vdev_set_state(vd->vdev_spa->spa_root_vdev,
                B_FALSE, VDEV_STATE_CANT_OPEN,
                VDEV_AUX_CORRUPT_DATA);
    }
}