vdev_label.c

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/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012 by Delphix. All rights reserved.
 */

#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/dmu.h>
#include <sys/zap.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#include <sys/uberblock_impl.h>
#include <sys/metaslab.h>
#include <sys/zio.h>
#include <sys/dsl_scan.h>
#include <sys/trim_map.h>
#include <sys/fs/zfs.h>

uint64_t
vdev_label_offset(uint64_t psize, int l, uint64_t offset)
{
        ASSERT(offset < sizeof (vdev_label_t));
        ASSERT(P2PHASE_TYPED(psize, sizeof (vdev_label_t), uint64_t) == 0);

        return (offset + l * sizeof (vdev_label_t) + (l < VDEV_LABELS / 2 ?
            0 : psize - VDEV_LABELS * sizeof (vdev_label_t)));
}

int
vdev_label_number(uint64_t psize, uint64_t offset)
{
        int l;

        if (offset >= psize - VDEV_LABEL_END_SIZE) {
                offset -= psize - VDEV_LABEL_END_SIZE;
                offset += (VDEV_LABELS / 2) * sizeof (vdev_label_t);
        }
        l = offset / sizeof (vdev_label_t);
        return (l < VDEV_LABELS ? l : -1);
}

static void
vdev_label_read(zio_t *zio, vdev_t *vd, int l, void *buf, uint64_t offset,
        uint64_t size, zio_done_func_t *done, void *private, int flags)
{
        ASSERT(spa_config_held(zio->io_spa, SCL_STATE_ALL, RW_WRITER) ==
            SCL_STATE_ALL);
        ASSERT(flags & ZIO_FLAG_CONFIG_WRITER);

        zio_nowait(zio_read_phys(zio, vd,
            vdev_label_offset(vd->vdev_psize, l, offset),
            size, buf, ZIO_CHECKSUM_LABEL, done, private,
            ZIO_PRIORITY_SYNC_READ, flags, B_TRUE));
}

static void
vdev_label_write(zio_t *zio, vdev_t *vd, int l, void *buf, uint64_t offset,
        uint64_t size, zio_done_func_t *done, void *private, int flags)
{
        ASSERT(spa_config_held(zio->io_spa, SCL_ALL, RW_WRITER) == SCL_ALL ||
            (spa_config_held(zio->io_spa, SCL_CONFIG | SCL_STATE, RW_READER) ==
            (SCL_CONFIG | SCL_STATE) &&
            dsl_pool_sync_context(spa_get_dsl(zio->io_spa))));
        ASSERT(flags & ZIO_FLAG_CONFIG_WRITER);

        zio_nowait(zio_write_phys(zio, vd,
            vdev_label_offset(vd->vdev_psize, l, offset),
            size, buf, ZIO_CHECKSUM_LABEL, done, private,
            ZIO_PRIORITY_SYNC_WRITE, flags, B_TRUE));
}

nvlist_t *
vdev_config_generate(spa_t *spa, vdev_t *vd, boolean_t getstats,
    vdev_config_flag_t flags)
{
        nvlist_t *nv = NULL;

        VERIFY(nvlist_alloc(&nv, NV_UNIQUE_NAME, KM_SLEEP) == 0);

        VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_TYPE,
            vd->vdev_ops->vdev_op_type) == 0);
        if (!(flags & (VDEV_CONFIG_SPARE | VDEV_CONFIG_L2CACHE)))
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ID, vd->vdev_id)
                    == 0);
        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_GUID, vd->vdev_guid) == 0);

        if (vd->vdev_path != NULL)
                VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_PATH,
                    vd->vdev_path) == 0);

        if (vd->vdev_devid != NULL)
                VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_DEVID,
                    vd->vdev_devid) == 0);

        if (vd->vdev_physpath != NULL)
                VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_PHYS_PATH,
                    vd->vdev_physpath) == 0);

        if (vd->vdev_fru != NULL)
                VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_FRU,
                    vd->vdev_fru) == 0);

        if (vd->vdev_nparity != 0) {
                ASSERT(strcmp(vd->vdev_ops->vdev_op_type,
                    VDEV_TYPE_RAIDZ) == 0);

                /*
                 * Make sure someone hasn't managed to sneak a fancy new vdev
                 * into a crufty old storage pool.
                 */
                ASSERT(vd->vdev_nparity == 1 ||
                    (vd->vdev_nparity <= 2 &&
                    spa_version(spa) >= SPA_VERSION_RAIDZ2) ||
                    (vd->vdev_nparity <= 3 &&
                    spa_version(spa) >= SPA_VERSION_RAIDZ3));

                /*
                 * Note that we'll add the nparity tag even on storage pools
                 * that only support a single parity device -- older software
                 * will just ignore it.
                 */
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_NPARITY,
                    vd->vdev_nparity) == 0);
        }

        if (vd->vdev_wholedisk != -1ULL)
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_WHOLE_DISK,
                    vd->vdev_wholedisk) == 0);

        if (vd->vdev_not_present)
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_NOT_PRESENT, 1) == 0);

        if (vd->vdev_isspare)
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_IS_SPARE, 1) == 0);

        if (!(flags & (VDEV_CONFIG_SPARE | VDEV_CONFIG_L2CACHE)) &&
            vd == vd->vdev_top) {
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_ARRAY,
                    vd->vdev_ms_array) == 0);
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_METASLAB_SHIFT,
                    vd->vdev_ms_shift) == 0);
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ASHIFT,
                    vd->vdev_ashift) == 0);
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ASIZE,
                    vd->vdev_asize) == 0);
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_IS_LOG,
                    vd->vdev_islog) == 0);
                if (vd->vdev_removing)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVING,
                            vd->vdev_removing) == 0);
        }

        if (vd->vdev_dtl_smo.smo_object != 0)
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_DTL,
                    vd->vdev_dtl_smo.smo_object) == 0);

        if (vd->vdev_crtxg)
                VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_CREATE_TXG,
                    vd->vdev_crtxg) == 0);

        if (getstats) {
                vdev_stat_t vs;
                pool_scan_stat_t ps;

                vdev_get_stats(vd, &vs);
                VERIFY(nvlist_add_uint64_array(nv, ZPOOL_CONFIG_VDEV_STATS,
                    (uint64_t *)&vs, sizeof (vs) / sizeof (uint64_t)) == 0);

                /* provide either current or previous scan information */
                if (spa_scan_get_stats(spa, &ps) == 0) {
                        VERIFY(nvlist_add_uint64_array(nv,
                            ZPOOL_CONFIG_SCAN_STATS, (uint64_t *)&ps,
                            sizeof (pool_scan_stat_t) / sizeof (uint64_t))
                            == 0);
                }
        }

        if (!vd->vdev_ops->vdev_op_leaf) {
                nvlist_t **child;
                int c, idx;

                ASSERT(!vd->vdev_ishole);

                child = kmem_alloc(vd->vdev_children * sizeof (nvlist_t *),
                    KM_SLEEP);

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

                        /*
                         * If we're generating an nvlist of removing
                         * vdevs then skip over any device which is
                         * not being removed.
                         */
                        if ((flags & VDEV_CONFIG_REMOVING) &&
                            !cvd->vdev_removing)
                                continue;

                        child[idx++] = vdev_config_generate(spa, cvd,
                            getstats, flags);
                }

                if (idx) {
                        VERIFY(nvlist_add_nvlist_array(nv,
                            ZPOOL_CONFIG_CHILDREN, child, idx) == 0);
                }

                for (c = 0; c < idx; c++)
                        nvlist_free(child[c]);

                kmem_free(child, vd->vdev_children * sizeof (nvlist_t *));

        } else {
                const char *aux = NULL;

                if (vd->vdev_offline && !vd->vdev_tmpoffline)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_OFFLINE,
                            B_TRUE) == 0);
                if (vd->vdev_resilvering)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_RESILVERING,
                            B_TRUE) == 0);
                if (vd->vdev_faulted)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_FAULTED,
                            B_TRUE) == 0);
                if (vd->vdev_degraded)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_DEGRADED,
                            B_TRUE) == 0);
                if (vd->vdev_removed)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_REMOVED,
                            B_TRUE) == 0);
                if (vd->vdev_unspare)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_UNSPARE,
                            B_TRUE) == 0);
                if (vd->vdev_ishole)
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_IS_HOLE,
                            B_TRUE) == 0);

                switch (vd->vdev_stat.vs_aux) {
                case VDEV_AUX_ERR_EXCEEDED:
                        aux = "err_exceeded";
                        break;

                case VDEV_AUX_EXTERNAL:
                        aux = "external";
                        break;
                }

                if (aux != NULL)
                        VERIFY(nvlist_add_string(nv, ZPOOL_CONFIG_AUX_STATE,
                            aux) == 0);

                if (vd->vdev_splitting && vd->vdev_orig_guid != 0LL) {
                        VERIFY(nvlist_add_uint64(nv, ZPOOL_CONFIG_ORIG_GUID,
                            vd->vdev_orig_guid) == 0);
                }
        }

        return (nv);
}

void
vdev_top_config_generate(spa_t *spa, nvlist_t *config)
{
        vdev_t *rvd = spa->spa_root_vdev;
        uint64_t *array;
        uint_t c, idx;

        array = kmem_alloc(rvd->vdev_children * sizeof (uint64_t), KM_SLEEP);

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

                if (tvd->vdev_ishole)
                        array[idx++] = c;
        }

        if (idx) {
                VERIFY(nvlist_add_uint64_array(config, ZPOOL_CONFIG_HOLE_ARRAY,
                    array, idx) == 0);
        }

        VERIFY(nvlist_add_uint64(config, ZPOOL_CONFIG_VDEV_CHILDREN,
            rvd->vdev_children) == 0);

        kmem_free(array, rvd->vdev_children * sizeof (uint64_t));
}

nvlist_t *
vdev_label_read_config(vdev_t *vd, uint64_t txg)
{
        spa_t *spa = vd->vdev_spa;
        nvlist_t *config = NULL;
        vdev_phys_t *vp;
        zio_t *zio;
        uint64_t best_txg = 0;
        int error = 0;
        int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL |
            ZIO_FLAG_SPECULATIVE;

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

        if (!vdev_readable(vd))
                return (NULL);

        vp = zio_buf_alloc(sizeof (vdev_phys_t));

retry:
        for (int l = 0; l < VDEV_LABELS; l++) {
                nvlist_t *label = NULL;

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

                vdev_label_read(zio, vd, l, vp,
                    offsetof(vdev_label_t, vl_vdev_phys),
                    sizeof (vdev_phys_t), NULL, NULL, flags);

                if (zio_wait(zio) == 0 &&
                    nvlist_unpack(vp->vp_nvlist, sizeof (vp->vp_nvlist),
                    &label, 0) == 0) {
                        uint64_t label_txg = 0;

                        /*
                         * Auxiliary vdevs won't have txg values in their
                         * labels and newly added vdevs may not have been
                         * completely initialized so just return the
                         * configuration from the first valid label we
                         * encounter.
                         */
                        error = nvlist_lookup_uint64(label,
                            ZPOOL_CONFIG_POOL_TXG, &label_txg);
                        if ((error || label_txg == 0) && !config) {
                                config = label;
                                break;
                        } else if (label_txg <= txg && label_txg > best_txg) {
                                best_txg = label_txg;
                                nvlist_free(config);
                                config = fnvlist_dup(label);
                        }
                }

                if (label != NULL) {
                        nvlist_free(label);
                        label = NULL;
                }
        }

        if (config == NULL && !(flags & ZIO_FLAG_TRYHARD)) {
                flags |= ZIO_FLAG_TRYHARD;
                goto retry;
        }

        zio_buf_free(vp, sizeof (vdev_phys_t));

        return (config);
}

static boolean_t
vdev_inuse(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason,
    uint64_t *spare_guid, uint64_t *l2cache_guid)
{
        spa_t *spa = vd->vdev_spa;
        uint64_t state, pool_guid, device_guid, txg, spare_pool;
        uint64_t vdtxg = 0;
        nvlist_t *label;

        if (spare_guid)
                *spare_guid = 0ULL;
        if (l2cache_guid)
                *l2cache_guid = 0ULL;

        /*
         * Read the label, if any, and perform some basic sanity checks.
         */
        if ((label = vdev_label_read_config(vd, -1ULL)) == NULL)
                return (B_FALSE);

        (void) nvlist_lookup_uint64(label, ZPOOL_CONFIG_CREATE_TXG,
            &vdtxg);

        if (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_STATE,
            &state) != 0 ||
            nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID,
            &device_guid) != 0) {
                nvlist_free(label);
                return (B_FALSE);
        }

        if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
            (nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID,
            &pool_guid) != 0 ||
            nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_TXG,
            &txg) != 0)) {
                nvlist_free(label);
                return (B_FALSE);
        }

        nvlist_free(label);

        /*
         * Check to see if this device indeed belongs to the pool it claims to
         * be a part of.  The only way this is allowed is if the device is a hot
         * spare (which we check for later on).
         */
        if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
            !spa_guid_exists(pool_guid, device_guid) &&
            !spa_spare_exists(device_guid, NULL, NULL) &&
            !spa_l2cache_exists(device_guid, NULL))
                return (B_FALSE);

        /*
         * If the transaction group is zero, then this an initialized (but
         * unused) label.  This is only an error if the create transaction
         * on-disk is the same as the one we're using now, in which case the
         * user has attempted to add the same vdev multiple times in the same
         * transaction.
         */
        if (state != POOL_STATE_SPARE && state != POOL_STATE_L2CACHE &&
            txg == 0 && vdtxg == crtxg)
                return (B_TRUE);

        /*
         * Check to see if this is a spare device.  We do an explicit check for
         * spa_has_spare() here because it may be on our pending list of spares
         * to add.  We also check if it is an l2cache device.
         */
        if (spa_spare_exists(device_guid, &spare_pool, NULL) ||
            spa_has_spare(spa, device_guid)) {
                if (spare_guid)
                        *spare_guid = device_guid;

                switch (reason) {
                case VDEV_LABEL_CREATE:
                case VDEV_LABEL_L2CACHE:
                        return (B_TRUE);

                case VDEV_LABEL_REPLACE:
                        return (!spa_has_spare(spa, device_guid) ||
                            spare_pool != 0ULL);

                case VDEV_LABEL_SPARE:
                        return (spa_has_spare(spa, device_guid));
                }
        }

        /*
         * Check to see if this is an l2cache device.
         */
        if (spa_l2cache_exists(device_guid, NULL))
                return (B_TRUE);

        /*
         * We can't rely on a pool's state if it's been imported
         * read-only.  Instead we look to see if the pools is marked
         * read-only in the namespace and set the state to active.
         */
        if ((spa = spa_by_guid(pool_guid, device_guid)) != NULL &&
            spa_mode(spa) == FREAD)
                state = POOL_STATE_ACTIVE;

        /*
         * If the device is marked ACTIVE, then this device is in use by another
         * pool on the system.
         */
        return (state == POOL_STATE_ACTIVE);
}

int
vdev_label_init(vdev_t *vd, uint64_t crtxg, vdev_labeltype_t reason)
{
        spa_t *spa = vd->vdev_spa;
        nvlist_t *label;
        vdev_phys_t *vp;
        char *pad2;
        uberblock_t *ub;
        zio_t *zio;
        char *buf;
        size_t buflen;
        int error;
        uint64_t spare_guid, l2cache_guid;
        int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;

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

        for (int c = 0; c < vd->vdev_children; c++)
                if ((error = vdev_label_init(vd->vdev_child[c],
                    crtxg, reason)) != 0)
                        return (error);

        /* Track the creation time for this vdev */
        vd->vdev_crtxg = crtxg;

        if (!vd->vdev_ops->vdev_op_leaf)
                return (0);

        /*
         * Dead vdevs cannot be initialized.
         */
        if (vdev_is_dead(vd))
                return (EIO);

        /*
         * Determine if the vdev is in use.
         */
        if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_SPLIT &&
            vdev_inuse(vd, crtxg, reason, &spare_guid, &l2cache_guid))
                return (EBUSY);

        /*
         * If this is a request to add or replace a spare or l2cache device
         * that is in use elsewhere on the system, then we must update the
         * guid (which was initialized to a random value) to reflect the
         * actual GUID (which is shared between multiple pools).
         */
        if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_L2CACHE &&
            spare_guid != 0ULL) {
                uint64_t guid_delta = spare_guid - vd->vdev_guid;

                vd->vdev_guid += guid_delta;

                for (vdev_t *pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
                        pvd->vdev_guid_sum += guid_delta;

                /*
                 * If this is a replacement, then we want to fallthrough to the
                 * rest of the code.  If we're adding a spare, then it's already
                 * labeled appropriately and we can just return.
                 */
                if (reason == VDEV_LABEL_SPARE)
                        return (0);
                ASSERT(reason == VDEV_LABEL_REPLACE ||
                    reason == VDEV_LABEL_SPLIT);
        }

        if (reason != VDEV_LABEL_REMOVE && reason != VDEV_LABEL_SPARE &&
            l2cache_guid != 0ULL) {
                uint64_t guid_delta = l2cache_guid - vd->vdev_guid;

                vd->vdev_guid += guid_delta;

                for (vdev_t *pvd = vd; pvd != NULL; pvd = pvd->vdev_parent)
                        pvd->vdev_guid_sum += guid_delta;

                /*
                 * If this is a replacement, then we want to fallthrough to the
                 * rest of the code.  If we're adding an l2cache, then it's
                 * already labeled appropriately and we can just return.
                 */
                if (reason == VDEV_LABEL_L2CACHE)
                        return (0);
                ASSERT(reason == VDEV_LABEL_REPLACE);
        }

        /*
         * TRIM the whole thing so that we start with a clean slate.
         * It's just an optimization, so we don't care if it fails.
         * Don't TRIM if removing so that we don't interfere with zpool
         * disaster recovery.
         */
        if (!zfs_notrim && (reason == VDEV_LABEL_CREATE ||
            reason == VDEV_LABEL_SPARE || reason == VDEV_LABEL_L2CACHE))
                zio_wait(zio_trim(NULL, spa, vd, 0, vd->vdev_psize));

        /*
         * Initialize its label.
         */
        vp = zio_buf_alloc(sizeof (vdev_phys_t));
        bzero(vp, sizeof (vdev_phys_t));

        /*
         * Generate a label describing the pool and our top-level vdev.
         * We mark it as being from txg 0 to indicate that it's not
         * really part of an active pool just yet.  The labels will
         * be written again with a meaningful txg by spa_sync().
         */
        if (reason == VDEV_LABEL_SPARE ||
            (reason == VDEV_LABEL_REMOVE && vd->vdev_isspare)) {
                /*
                 * For inactive hot spares, we generate a special label that
                 * identifies as a mutually shared hot spare.  We write the
                 * label if we are adding a hot spare, or if we are removing an
                 * active hot spare (in which case we want to revert the
                 * labels).
                 */
                VERIFY(nvlist_alloc(&label, NV_UNIQUE_NAME, KM_SLEEP) == 0);

                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_VERSION,
                    spa_version(spa)) == 0);
                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_POOL_STATE,
                    POOL_STATE_SPARE) == 0);
                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_GUID,
                    vd->vdev_guid) == 0);
        } else if (reason == VDEV_LABEL_L2CACHE ||
            (reason == VDEV_LABEL_REMOVE && vd->vdev_isl2cache)) {
                /*
                 * For level 2 ARC devices, add a special label.
                 */
                VERIFY(nvlist_alloc(&label, NV_UNIQUE_NAME, KM_SLEEP) == 0);

                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_VERSION,
                    spa_version(spa)) == 0);
                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_POOL_STATE,
                    POOL_STATE_L2CACHE) == 0);
                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_GUID,
                    vd->vdev_guid) == 0);
        } else {
                uint64_t txg = 0ULL;

                if (reason == VDEV_LABEL_SPLIT)
                        txg = spa->spa_uberblock.ub_txg;
                label = spa_config_generate(spa, vd, txg, B_FALSE);

                /*
                 * Add our creation time.  This allows us to detect multiple
                 * vdev uses as described above, and automatically expires if we
                 * fail.
                 */
                VERIFY(nvlist_add_uint64(label, ZPOOL_CONFIG_CREATE_TXG,
                    crtxg) == 0);
        }

        buf = vp->vp_nvlist;
        buflen = sizeof (vp->vp_nvlist);

        error = nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP);
        if (error != 0) {
                nvlist_free(label);
                zio_buf_free(vp, sizeof (vdev_phys_t));
                /* EFAULT means nvlist_pack ran out of room */
                return (error == EFAULT ? ENAMETOOLONG : EINVAL);
        }

        /*
         * Initialize uberblock template.
         */
        ub = zio_buf_alloc(VDEV_UBERBLOCK_RING);
        bzero(ub, VDEV_UBERBLOCK_RING);
        *ub = spa->spa_uberblock;
        ub->ub_txg = 0;

        /* Initialize the 2nd padding area. */
        pad2 = zio_buf_alloc(VDEV_PAD_SIZE);
        bzero(pad2, VDEV_PAD_SIZE);

        /*
         * Write everything in parallel.
         */
retry:
        zio = zio_root(spa, NULL, NULL, flags);

        for (int l = 0; l < VDEV_LABELS; l++) {

                vdev_label_write(zio, vd, l, vp,
                    offsetof(vdev_label_t, vl_vdev_phys),
                    sizeof (vdev_phys_t), NULL, NULL, flags);

                /*
                 * Skip the 1st padding area.
                 * Zero out the 2nd padding area where it might have
                 * left over data from previous filesystem format.
                 */
                vdev_label_write(zio, vd, l, pad2,
                    offsetof(vdev_label_t, vl_pad2),
                    VDEV_PAD_SIZE, NULL, NULL, flags);

                vdev_label_write(zio, vd, l, ub,
                    offsetof(vdev_label_t, vl_uberblock),
                    VDEV_UBERBLOCK_RING, NULL, NULL, flags);
        }

        error = zio_wait(zio);

        if (error != 0 && !(flags & ZIO_FLAG_TRYHARD)) {
                flags |= ZIO_FLAG_TRYHARD;
                goto retry;
        }

        nvlist_free(label);
        zio_buf_free(pad2, VDEV_PAD_SIZE);
        zio_buf_free(ub, VDEV_UBERBLOCK_RING);
        zio_buf_free(vp, sizeof (vdev_phys_t));

        /*
         * If this vdev hasn't been previously identified as a spare, then we
         * mark it as such only if a) we are labeling it as a spare, or b) it
         * exists as a spare elsewhere in the system.  Do the same for
         * level 2 ARC devices.
         */
        if (error == 0 && !vd->vdev_isspare &&
            (reason == VDEV_LABEL_SPARE ||
            spa_spare_exists(vd->vdev_guid, NULL, NULL)))
                spa_spare_add(vd);

        if (error == 0 && !vd->vdev_isl2cache &&
            (reason == VDEV_LABEL_L2CACHE ||
            spa_l2cache_exists(vd->vdev_guid, NULL)))
                spa_l2cache_add(vd);

        return (error);
}

/*
 * ==========================================================================
 * uberblock load/sync
 * ==========================================================================
 */

static int
vdev_uberblock_compare(uberblock_t *ub1, uberblock_t *ub2)
{
        if (ub1->ub_txg < ub2->ub_txg)
                return (-1);
        if (ub1->ub_txg > ub2->ub_txg)
                return (1);

        if (ub1->ub_timestamp < ub2->ub_timestamp)
                return (-1);
        if (ub1->ub_timestamp > ub2->ub_timestamp)
                return (1);

        return (0);
}

struct ubl_cbdata {
        uberblock_t     *ubl_ubbest;    /* Best uberblock */
        vdev_t          *ubl_vd;        /* vdev associated with the above */
};

static void
vdev_uberblock_load_done(zio_t *zio)
{
        vdev_t *vd = zio->io_vd;
        spa_t *spa = zio->io_spa;
        zio_t *rio = zio->io_private;
        uberblock_t *ub = zio->io_data;
        struct ubl_cbdata *cbp = rio->io_private;

        ASSERT3U(zio->io_size, ==, VDEV_UBERBLOCK_SIZE(vd));

        if (zio->io_error == 0 && uberblock_verify(ub) == 0) {
                mutex_enter(&rio->io_lock);
                if (ub->ub_txg <= spa->spa_load_max_txg &&
                    vdev_uberblock_compare(ub, cbp->ubl_ubbest) > 0) {
                        /*
                         * Keep track of the vdev in which this uberblock
                         * was found. We will use this information later
                         * to obtain the config nvlist associated with
                         * this uberblock.
                         */
                        *cbp->ubl_ubbest = *ub;
                        cbp->ubl_vd = vd;
                }
                mutex_exit(&rio->io_lock);
        }

        zio_buf_free(zio->io_data, zio->io_size);
}

static void
vdev_uberblock_load_impl(zio_t *zio, vdev_t *vd, int flags,
    struct ubl_cbdata *cbp)
{
        for (int c = 0; c < vd->vdev_children; c++)
                vdev_uberblock_load_impl(zio, vd->vdev_child[c], flags, cbp);

        if (vd->vdev_ops->vdev_op_leaf && vdev_readable(vd)) {
                for (int l = 0; l < VDEV_LABELS; l++) {
                        for (int n = 0; n < VDEV_UBERBLOCK_COUNT(vd); n++) {
                                vdev_label_read(zio, vd, l,
                                    zio_buf_alloc(VDEV_UBERBLOCK_SIZE(vd)),
                                    VDEV_UBERBLOCK_OFFSET(vd, n),
                                    VDEV_UBERBLOCK_SIZE(vd),
                                    vdev_uberblock_load_done, zio, flags);
                        }
                }
        }
}

void
vdev_uberblock_load(vdev_t *rvd, uberblock_t *ub, nvlist_t **config)
{
        zio_t *zio;
        spa_t *spa = rvd->vdev_spa;
        struct ubl_cbdata cb;
        int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL |
            ZIO_FLAG_SPECULATIVE | ZIO_FLAG_TRYHARD;

        ASSERT(ub);
        ASSERT(config);

        bzero(ub, sizeof (uberblock_t));
        *config = NULL;

        cb.ubl_ubbest = ub;
        cb.ubl_vd = NULL;

        spa_config_enter(spa, SCL_ALL, FTAG, RW_WRITER);
        zio = zio_root(spa, NULL, &cb, flags);
        vdev_uberblock_load_impl(zio, rvd, flags, &cb);
        (void) zio_wait(zio);

        /*
         * It's possible that the best uberblock was discovered on a label
         * that has a configuration which was written in a future txg.
         * Search all labels on this vdev to find the configuration that
         * matches the txg for our uberblock.
         */
        if (cb.ubl_vd != NULL)
                *config = vdev_label_read_config(cb.ubl_vd, ub->ub_txg);
        spa_config_exit(spa, SCL_ALL, FTAG);
}

static void
vdev_uberblock_sync_done(zio_t *zio)
{
        uint64_t *good_writes = zio->io_private;

        if (zio->io_error == 0 && zio->io_vd->vdev_top->vdev_ms_array != 0)
                atomic_add_64(good_writes, 1);
}

static void
vdev_uberblock_sync(zio_t *zio, uberblock_t *ub, vdev_t *vd, int flags)
{
        uberblock_t *ubbuf;
        int n;

        for (int c = 0; c < vd->vdev_children; c++)
                vdev_uberblock_sync(zio, ub, vd->vdev_child[c], flags);

        if (!vd->vdev_ops->vdev_op_leaf)
                return;

        if (!vdev_writeable(vd))
                return;

        n = ub->ub_txg & (VDEV_UBERBLOCK_COUNT(vd) - 1);

        ubbuf = zio_buf_alloc(VDEV_UBERBLOCK_SIZE(vd));
        bzero(ubbuf, VDEV_UBERBLOCK_SIZE(vd));
        *ubbuf = *ub;

        for (int l = 0; l < VDEV_LABELS; l++)
                vdev_label_write(zio, vd, l, ubbuf,
                    VDEV_UBERBLOCK_OFFSET(vd, n), VDEV_UBERBLOCK_SIZE(vd),
                    vdev_uberblock_sync_done, zio->io_private,
                    flags | ZIO_FLAG_DONT_PROPAGATE);

        zio_buf_free(ubbuf, VDEV_UBERBLOCK_SIZE(vd));
}

int
vdev_uberblock_sync_list(vdev_t **svd, int svdcount, uberblock_t *ub, int flags)
{
        spa_t *spa = svd[0]->vdev_spa;
        zio_t *zio;
        uint64_t good_writes = 0;

        zio = zio_root(spa, NULL, &good_writes, flags);

        for (int v = 0; v < svdcount; v++)
                vdev_uberblock_sync(zio, ub, svd[v], flags);

        (void) zio_wait(zio);

        /*
         * Flush the uberblocks to disk.  This ensures that the odd labels
         * are no longer needed (because the new uberblocks and the even
         * labels are safely on disk), so it is safe to overwrite them.
         */
        zio = zio_root(spa, NULL, NULL, flags);

        for (int v = 0; v < svdcount; v++)
                zio_flush(zio, svd[v]);

        (void) zio_wait(zio);

        return (good_writes >= 1 ? 0 : EIO);
}

static void
vdev_label_sync_done(zio_t *zio)
{
        uint64_t *good_writes = zio->io_private;

        if (zio->io_error == 0)
                atomic_add_64(good_writes, 1);
}

static void
vdev_label_sync_top_done(zio_t *zio)
{
        uint64_t *good_writes = zio->io_private;

        if (*good_writes == 0)
                zio->io_error = EIO;

        kmem_free(good_writes, sizeof (uint64_t));
}

static void
vdev_label_sync_ignore_done(zio_t *zio)
{
        kmem_free(zio->io_private, sizeof (uint64_t));
}

static void
vdev_label_sync(zio_t *zio, vdev_t *vd, int l, uint64_t txg, int flags)
{
        nvlist_t *label;
        vdev_phys_t *vp;
        char *buf;
        size_t buflen;

        for (int c = 0; c < vd->vdev_children; c++)
                vdev_label_sync(zio, vd->vdev_child[c], l, txg, flags);

        if (!vd->vdev_ops->vdev_op_leaf)
                return;

        if (!vdev_writeable(vd))
                return;

        /*
         * Generate a label describing the top-level config to which we belong.
         */
        label = spa_config_generate(vd->vdev_spa, vd, txg, B_FALSE);

        vp = zio_buf_alloc(sizeof (vdev_phys_t));
        bzero(vp, sizeof (vdev_phys_t));

        buf = vp->vp_nvlist;
        buflen = sizeof (vp->vp_nvlist);

        if (nvlist_pack(label, &buf, &buflen, NV_ENCODE_XDR, KM_SLEEP) == 0) {
                for (; l < VDEV_LABELS; l += 2) {
                        vdev_label_write(zio, vd, l, vp,
                            offsetof(vdev_label_t, vl_vdev_phys),
                            sizeof (vdev_phys_t),
                            vdev_label_sync_done, zio->io_private,
                            flags | ZIO_FLAG_DONT_PROPAGATE);
                }
        }

        zio_buf_free(vp, sizeof (vdev_phys_t));
        nvlist_free(label);
}

int
vdev_label_sync_list(spa_t *spa, int l, uint64_t txg, int flags)
{
        list_t *dl = &spa->spa_config_dirty_list;
        vdev_t *vd;
        zio_t *zio;
        int error;

        /*
         * Write the new labels to disk.
         */
        zio = zio_root(spa, NULL, NULL, flags);

        for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd)) {
                uint64_t *good_writes = kmem_zalloc(sizeof (uint64_t),
                    KM_SLEEP);

                ASSERT(!vd->vdev_ishole);

                zio_t *vio = zio_null(zio, spa, NULL,
                    (vd->vdev_islog || vd->vdev_aux != NULL) ?
                    vdev_label_sync_ignore_done : vdev_label_sync_top_done,
                    good_writes, flags);
                vdev_label_sync(vio, vd, l, txg, flags);
                zio_nowait(vio);
        }

        error = zio_wait(zio);

        /*
         * Flush the new labels to disk.
         */
        zio = zio_root(spa, NULL, NULL, flags);

        for (vd = list_head(dl); vd != NULL; vd = list_next(dl, vd))
                zio_flush(zio, vd);

        (void) zio_wait(zio);

        return (error);
}

int
vdev_config_sync(vdev_t **svd, int svdcount, uint64_t txg, boolean_t tryhard)
{
        spa_t *spa = svd[0]->vdev_spa;
        uberblock_t *ub = &spa->spa_uberblock;
        vdev_t *vd;
        zio_t *zio;
        int error;
        int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;

        /*
         * Normally, we don't want to try too hard to write every label and
         * uberblock.  If there is a flaky disk, we don't want the rest of the
         * sync process to block while we retry.  But if we can't write a
         * single label out, we should retry with ZIO_FLAG_TRYHARD before
         * bailing out and declaring the pool faulted.
         */
        if (tryhard)
                flags |= ZIO_FLAG_TRYHARD;

        ASSERT(ub->ub_txg <= txg);

        /*
         * If this isn't a resync due to I/O errors,
         * and nothing changed in this transaction group,
         * and the vdev configuration hasn't changed,
         * then there's nothing to do.
         */
        if (ub->ub_txg < txg &&
            uberblock_update(ub, spa->spa_root_vdev, txg) == B_FALSE &&
            list_is_empty(&spa->spa_config_dirty_list))
                return (0);

        if (txg > spa_freeze_txg(spa))
                return (0);

        ASSERT(txg <= spa->spa_final_txg);

        /*
         * Flush the write cache of every disk that's been written to
         * in this transaction group.  This ensures that all blocks
         * written in this txg will be committed to stable storage
         * before any uberblock that references them.
         */
        zio = zio_root(spa, NULL, NULL, flags);

        for (vd = txg_list_head(&spa->spa_vdev_txg_list, TXG_CLEAN(txg)); vd;
            vd = txg_list_next(&spa->spa_vdev_txg_list, vd, TXG_CLEAN(txg)))
                zio_flush(zio, vd);

        (void) zio_wait(zio);

        /*
         * Sync out the even labels (L0, L2) for every dirty vdev.  If the
         * system dies in the middle of this process, that's OK: all of the
         * even labels that made it to disk will be newer than any uberblock,
         * and will therefore be considered invalid.  The odd labels (L1, L3),
         * which have not yet been touched, will still be valid.  We flush
         * the new labels to disk to ensure that all even-label updates
         * are committed to stable storage before the uberblock update.
         */
        if ((error = vdev_label_sync_list(spa, 0, txg, flags)) != 0)
                return (error);

        /*
         * Sync the uberblocks to all vdevs in svd[].
         * If the system dies in the middle of this step, there are two cases
         * to consider, and the on-disk state is consistent either way:
         *
         * (1)  If none of the new uberblocks made it to disk, then the
         *      previous uberblock will be the newest, and the odd labels
         *      (which had not yet been touched) will be valid with respect
         *      to that uberblock.
         *
         * (2)  If one or more new uberblocks made it to disk, then they
         *      will be the newest, and the even labels (which had all
         *      been successfully committed) will be valid with respect
         *      to the new uberblocks.
         */
        if ((error = vdev_uberblock_sync_list(svd, svdcount, ub, flags)) != 0)
                return (error);

        /*
         * Sync out odd labels for every dirty vdev.  If the system dies
         * in the middle of this process, the even labels and the new
         * uberblocks will suffice to open the pool.  The next time
         * the pool is opened, the first thing we'll do -- before any
         * user data is modified -- is mark every vdev dirty so that
         * all labels will be brought up to date.  We flush the new labels
         * to disk to ensure that all odd-label updates are committed to
         * stable storage before the next transaction group begins.
         */
        if ((error = vdev_label_sync_list(spa, 1, txg, flags)) != 0)
                return (error);

        trim_thread_wakeup(spa);

        return (0);
}