fs/zfs/vdev_mirror.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 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
 */

#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/vdev_impl.h>
#include <sys/zio.h>
#include <sys/fs/zfs.h>

/*
 * Virtual device vector for mirroring.
 */

typedef struct mirror_child {
    vdev_t      *mc_vd;
    uint64_t    mc_offset;
    int     mc_error;
    uint8_t     mc_tried;
    uint8_t     mc_skipped;
    uint8_t     mc_speculative;
} mirror_child_t;

typedef struct mirror_map {
    int     mm_children;
    int     mm_replacing;
    int     mm_preferred;
    int     mm_root;
    mirror_child_t  mm_child[1];
} mirror_map_t;

int vdev_mirror_shift = 21;

static void
vdev_mirror_map_free(zio_t *zio)
{
    mirror_map_t *mm = zio->io_vsd;

    kmem_free(mm, offsetof(mirror_map_t, mm_child[mm->mm_children]));
}

static const zio_vsd_ops_t vdev_mirror_vsd_ops = {
    vdev_mirror_map_free,
    zio_vsd_default_cksum_report
};

static mirror_map_t *
vdev_mirror_map_alloc(zio_t *zio)
{
    mirror_map_t *mm = NULL;
    mirror_child_t *mc;
    vdev_t *vd = zio->io_vd;
    int c, d;

    if (vd == NULL) {
        dva_t *dva = zio->io_bp->blk_dva;
        spa_t *spa = zio->io_spa;

        c = BP_GET_NDVAS(zio->io_bp);

        mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
        mm->mm_children = c;
        mm->mm_replacing = B_FALSE;
        mm->mm_preferred = spa_get_random(c);
        mm->mm_root = B_TRUE;

        /*
         * Check the other, lower-index DVAs to see if they're on
         * the same vdev as the child we picked.  If they are, use
         * them since they are likely to have been allocated from
         * the primary metaslab in use at the time, and hence are
         * more likely to have locality with single-copy data.
         */
        for (c = mm->mm_preferred, d = c - 1; d >= 0; d--) {
            if (DVA_GET_VDEV(&dva[d]) == DVA_GET_VDEV(&dva[c]))
                mm->mm_preferred = d;
        }

        for (c = 0; c < mm->mm_children; c++) {
            mc = &mm->mm_child[c];

            mc->mc_vd = vdev_lookup_top(spa, DVA_GET_VDEV(&dva[c]));
            mc->mc_offset = DVA_GET_OFFSET(&dva[c]);
        }
    } else {
        c = vd->vdev_children;

        mm = kmem_zalloc(offsetof(mirror_map_t, mm_child[c]), KM_SLEEP);
        mm->mm_children = c;
        mm->mm_replacing = (vd->vdev_ops == &vdev_replacing_ops ||
            vd->vdev_ops == &vdev_spare_ops);
        mm->mm_preferred = mm->mm_replacing ? 0 :
            (zio->io_offset >> vdev_mirror_shift) % c;
        mm->mm_root = B_FALSE;

        for (c = 0; c < mm->mm_children; c++) {
            mc = &mm->mm_child[c];
            mc->mc_vd = vd->vdev_child[c];
            mc->mc_offset = zio->io_offset;
        }
    }

    zio->io_vsd = mm;
    zio->io_vsd_ops = &vdev_mirror_vsd_ops;
    return (mm);
}

static int
vdev_mirror_open(vdev_t *vd, uint64_t *asize, uint64_t *max_asize,
    uint64_t *ashift)
{
    int numerrors = 0;
    int lasterror = 0;

    if (vd->vdev_children == 0) {
        vd->vdev_stat.vs_aux = VDEV_AUX_BAD_LABEL;
        return (SET_ERROR(EINVAL));
    }

    vdev_open_children(vd);

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

        if (cvd->vdev_open_error) {
            lasterror = cvd->vdev_open_error;
            numerrors++;
            continue;
        }

        *asize = MIN(*asize - 1, cvd->vdev_asize - 1) + 1;
        *max_asize = MIN(*max_asize - 1, cvd->vdev_max_asize - 1) + 1;
        *ashift = MAX(*ashift, cvd->vdev_ashift);
    }

    if (numerrors == vd->vdev_children) {
        vd->vdev_stat.vs_aux = VDEV_AUX_NO_REPLICAS;
        return (lasterror);
    }

    return (0);
}

static void
vdev_mirror_close(vdev_t *vd)
{
    for (int c = 0; c < vd->vdev_children; c++)
        vdev_close(vd->vdev_child[c]);
}

static void
vdev_mirror_child_done(zio_t *zio)
{
    mirror_child_t *mc = zio->io_private;

    mc->mc_error = zio->io_error;
    mc->mc_tried = 1;
    mc->mc_skipped = 0;
}

static void
vdev_mirror_scrub_done(zio_t *zio)
{
    mirror_child_t *mc = zio->io_private;

    if (zio->io_error == 0) {
        zio_t *pio;
        zio_link_t *zl = NULL;

        mutex_enter(&zio->io_lock);
        while ((pio = zio_walk_parents(zio, &zl)) != NULL) {
            mutex_enter(&pio->io_lock);
            ASSERT3U(zio->io_size, >=, pio->io_size);
            bcopy(zio->io_data, pio->io_data, pio->io_size);
            mutex_exit(&pio->io_lock);
        }
        mutex_exit(&zio->io_lock);
    }

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

    mc->mc_error = zio->io_error;
    mc->mc_tried = 1;
    mc->mc_skipped = 0;
}

/*
 * Try to find a child whose DTL doesn't contain the block we want to read.
 * If we can't, try the read on any vdev we haven't already tried.
 */
static int
vdev_mirror_child_select(zio_t *zio)
{
    mirror_map_t *mm = zio->io_vsd;
    mirror_child_t *mc;
    uint64_t txg = zio->io_txg;
    int i, c;

    ASSERT(zio->io_bp == NULL || BP_PHYSICAL_BIRTH(zio->io_bp) == txg);

    /*
     * Try to find a child whose DTL doesn't contain the block to read.
     * If a child is known to be completely inaccessible (indicated by
     * vdev_readable() returning B_FALSE), don't even try.
     */
    for (i = 0, c = mm->mm_preferred; i < mm->mm_children; i++, c++) {
        if (c >= mm->mm_children)
            c = 0;
        mc = &mm->mm_child[c];
        if (mc->mc_tried || mc->mc_skipped)
            continue;
        if (!vdev_readable(mc->mc_vd)) {
            mc->mc_error = SET_ERROR(ENXIO);
            mc->mc_tried = 1;   /* don't even try */
            mc->mc_skipped = 1;
            continue;
        }
        if (!vdev_dtl_contains(mc->mc_vd, DTL_MISSING, txg, 1))
            return (c);
        mc->mc_error = SET_ERROR(ESTALE);
        mc->mc_skipped = 1;
        mc->mc_speculative = 1;
    }

    /*
     * Every device is either missing or has this txg in its DTL.
     * Look for any child we haven't already tried before giving up.
     */
    for (c = 0; c < mm->mm_children; c++)
        if (!mm->mm_child[c].mc_tried)
            return (c);

    /*
     * Every child failed.  There's no place left to look.
     */
    return (-1);
}

static void
vdev_mirror_io_start(zio_t *zio)
{
    mirror_map_t *mm;
    mirror_child_t *mc;
    int c, children;

    mm = vdev_mirror_map_alloc(zio);

    if (zio->io_type == ZIO_TYPE_READ) {
        if ((zio->io_flags & ZIO_FLAG_SCRUB) && !mm->mm_replacing) {
            /*
             * For scrubbing reads we need to allocate a read
             * buffer for each child and issue reads to all
             * children.  If any child succeeds, it will copy its
             * data into zio->io_data in vdev_mirror_scrub_done.
             */
            for (c = 0; c < mm->mm_children; c++) {
                mc = &mm->mm_child[c];
                zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
                    mc->mc_vd, mc->mc_offset,
                    zio_buf_alloc(zio->io_size), zio->io_size,
                    zio->io_type, zio->io_priority, 0,
                    vdev_mirror_scrub_done, mc));
            }
            zio_execute(zio);
            return;
        }
        /*
         * For normal reads just pick one child.
         */
        c = vdev_mirror_child_select(zio);
        children = (c >= 0);
    } else {
        ASSERT(zio->io_type == ZIO_TYPE_WRITE);

        /*
         * Writes go to all children.
         */
        c = 0;
        children = mm->mm_children;
    }

    while (children--) {
        mc = &mm->mm_child[c];
        zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
            mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
            zio->io_type, zio->io_priority, 0,
            vdev_mirror_child_done, mc));
        c++;
    }

    zio_execute(zio);
}

static int
vdev_mirror_worst_error(mirror_map_t *mm)
{
    int error[2] = { 0, 0 };

    for (int c = 0; c < mm->mm_children; c++) {
        mirror_child_t *mc = &mm->mm_child[c];
        int s = mc->mc_speculative;
        error[s] = zio_worst_error(error[s], mc->mc_error);
    }

    return (error[0] ? error[0] : error[1]);
}

static void
vdev_mirror_io_done(zio_t *zio)
{
    mirror_map_t *mm = zio->io_vsd;
    mirror_child_t *mc;
    int c;
    int good_copies = 0;
    int unexpected_errors = 0;

    for (c = 0; c < mm->mm_children; c++) {
        mc = &mm->mm_child[c];

        if (mc->mc_error) {
            if (!mc->mc_skipped)
                unexpected_errors++;
        } else if (mc->mc_tried) {
            good_copies++;
        }
    }

    if (zio->io_type == ZIO_TYPE_WRITE) {
        /*
         * XXX -- for now, treat partial writes as success.
         *
         * Now that we support write reallocation, it would be better
         * to treat partial failure as real failure unless there are
         * no non-degraded top-level vdevs left, and not update DTLs
         * if we intend to reallocate.
         */
        /* XXPOLICY */
        if (good_copies != mm->mm_children) {
            /*
             * Always require at least one good copy.
             *
             * For ditto blocks (io_vd == NULL), require
             * all copies to be good.
             *
             * XXX -- for replacing vdevs, there's no great answer.
             * If the old device is really dead, we may not even
             * be able to access it -- so we only want to
             * require good writes to the new device.  But if
             * the new device turns out to be flaky, we want
             * to be able to detach it -- which requires all
             * writes to the old device to have succeeded.
             */
            if (good_copies == 0 || zio->io_vd == NULL)
                zio->io_error = vdev_mirror_worst_error(mm);
        }
        return;
    }

    ASSERT(zio->io_type == ZIO_TYPE_READ);

    /*
     * If we don't have a good copy yet, keep trying other children.
     */
    /* XXPOLICY */
    if (good_copies == 0 && (c = vdev_mirror_child_select(zio)) != -1) {
        ASSERT(c >= 0 && c < mm->mm_children);
        mc = &mm->mm_child[c];
        zio_vdev_io_redone(zio);
        zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
            mc->mc_vd, mc->mc_offset, zio->io_data, zio->io_size,
            ZIO_TYPE_READ, zio->io_priority, 0,
            vdev_mirror_child_done, mc));
        return;
    }

    /* XXPOLICY */
    if (good_copies == 0) {
        zio->io_error = vdev_mirror_worst_error(mm);
        ASSERT(zio->io_error != 0);
    }

    if (good_copies && spa_writeable(zio->io_spa) &&
        (unexpected_errors ||
        (zio->io_flags & ZIO_FLAG_RESILVER) ||
        ((zio->io_flags & ZIO_FLAG_SCRUB) && mm->mm_replacing))) {
        /*
         * Use the good data we have in hand to repair damaged children.
         */
        for (c = 0; c < mm->mm_children; c++) {
            /*
             * Don't rewrite known good children.
             * Not only is it unnecessary, it could
             * actually be harmful: if the system lost
             * power while rewriting the only good copy,
             * there would be no good copies left!
             */
            mc = &mm->mm_child[c];

            if (mc->mc_error == 0) {
                if (mc->mc_tried)
                    continue;
                if (!(zio->io_flags & ZIO_FLAG_SCRUB) &&
                    !vdev_dtl_contains(mc->mc_vd, DTL_PARTIAL,
                    zio->io_txg, 1))
                    continue;
                mc->mc_error = SET_ERROR(ESTALE);
            }

            zio_nowait(zio_vdev_child_io(zio, zio->io_bp,
                mc->mc_vd, mc->mc_offset,
                zio->io_data, zio->io_size,
                ZIO_TYPE_WRITE, ZIO_PRIORITY_ASYNC_WRITE,
                ZIO_FLAG_IO_REPAIR | (unexpected_errors ?
                ZIO_FLAG_SELF_HEAL : 0), NULL, NULL));
        }
    }
}

static void
vdev_mirror_state_change(vdev_t *vd, int faulted, int degraded)
{
    if (faulted == vd->vdev_children)
        vdev_set_state(vd, B_FALSE, VDEV_STATE_CANT_OPEN,
            VDEV_AUX_NO_REPLICAS);
    else if (degraded + faulted != 0)
        vdev_set_state(vd, B_FALSE, VDEV_STATE_DEGRADED, VDEV_AUX_NONE);
    else
        vdev_set_state(vd, B_FALSE, VDEV_STATE_HEALTHY, VDEV_AUX_NONE);
}

vdev_ops_t vdev_mirror_ops = {
    vdev_mirror_open,
    vdev_mirror_close,
    vdev_default_asize,
    vdev_mirror_io_start,
    vdev_mirror_io_done,
    vdev_mirror_state_change,
    NULL,
    NULL,
    VDEV_TYPE_MIRROR,   /* name of this vdev type */
    B_FALSE         /* not a leaf vdev */
};

vdev_ops_t vdev_replacing_ops = {
    vdev_mirror_open,
    vdev_mirror_close,
    vdev_default_asize,
    vdev_mirror_io_start,
    vdev_mirror_io_done,
    vdev_mirror_state_change,
    NULL,
    NULL,
    VDEV_TYPE_REPLACING,    /* name of this vdev type */
    B_FALSE         /* not a leaf vdev */
};

vdev_ops_t vdev_spare_ops = {
    vdev_mirror_open,
    vdev_mirror_close,
    vdev_default_asize,
    vdev_mirror_io_start,
    vdev_mirror_io_done,
    vdev_mirror_state_change,
    NULL,
    NULL,
    VDEV_TYPE_SPARE,    /* name of this vdev type */
    B_FALSE         /* not a leaf vdev */
};