/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/bio.h>
#include <sys/endian.h>
#include <sys/kernel.h>
#include <sys/kobj.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <geom/geom.h>
#include <geom/geom_dbg.h>
#include "geom/raid/g_raid.h"
#include "g_raid_tr_if.h"

SYSCTL_DECL(_kern_geom_raid_raid1);

#define RAID1_REBUILD_SLAB      (1 << 20) /* One transation in a rebuild */
static int g_raid1_rebuild_slab = RAID1_REBUILD_SLAB;
SYSCTL_UINT(_kern_geom_raid_raid1, OID_AUTO, rebuild_slab_size, CTLFLAG_RWTUN,
    &g_raid1_rebuild_slab, 0,
    "Amount of the disk to rebuild each read/write cycle of the rebuild.");

#define RAID1_REBUILD_FAIR_IO 20 /* use 1/x of the available I/O */
static int g_raid1_rebuild_fair_io = RAID1_REBUILD_FAIR_IO;
SYSCTL_UINT(_kern_geom_raid_raid1, OID_AUTO, rebuild_fair_io, CTLFLAG_RWTUN,
    &g_raid1_rebuild_fair_io, 0,
    "Fraction of the I/O bandwidth to use when disk busy for rebuild.");

#define RAID1_REBUILD_CLUSTER_IDLE 100
static int g_raid1_rebuild_cluster_idle = RAID1_REBUILD_CLUSTER_IDLE;
SYSCTL_UINT(_kern_geom_raid_raid1, OID_AUTO, rebuild_cluster_idle, CTLFLAG_RWTUN,
    &g_raid1_rebuild_cluster_idle, 0,
    "Number of slabs to do each time we trigger a rebuild cycle");

#define RAID1_REBUILD_META_UPDATE 1024 /* update meta data every 1GB or so */
static int g_raid1_rebuild_meta_update = RAID1_REBUILD_META_UPDATE;
SYSCTL_UINT(_kern_geom_raid_raid1, OID_AUTO, rebuild_meta_update, CTLFLAG_RWTUN,
    &g_raid1_rebuild_meta_update, 0,
    "When to update the meta data.");

static MALLOC_DEFINE(M_TR_RAID1, "tr_raid1_data", "GEOM_RAID RAID1 data");

#define TR_RAID1_NONE 0
#define TR_RAID1_REBUILD 1
#define TR_RAID1_RESYNC 2

#define TR_RAID1_F_DOING_SOME   0x1
#define TR_RAID1_F_LOCKED       0x2
#define TR_RAID1_F_ABORT        0x4

struct g_raid_tr_raid1_object {
        struct g_raid_tr_object  trso_base;
        int                      trso_starting;
        int                      trso_stopping;
        int                      trso_type;
        int                      trso_recover_slabs; /* slabs before rest */
        int                      trso_fair_io;
        int                      trso_meta_update;
        int                      trso_flags;
        struct g_raid_subdisk   *trso_failed_sd; /* like per volume */
        void                    *trso_buffer;    /* Buffer space */
        struct bio               trso_bio;
};

static g_raid_tr_taste_t g_raid_tr_taste_raid1;
static g_raid_tr_event_t g_raid_tr_event_raid1;
static g_raid_tr_start_t g_raid_tr_start_raid1;
static g_raid_tr_stop_t g_raid_tr_stop_raid1;
static g_raid_tr_iostart_t g_raid_tr_iostart_raid1;
static g_raid_tr_iodone_t g_raid_tr_iodone_raid1;
static g_raid_tr_kerneldump_t g_raid_tr_kerneldump_raid1;
static g_raid_tr_locked_t g_raid_tr_locked_raid1;
static g_raid_tr_idle_t g_raid_tr_idle_raid1;
static g_raid_tr_free_t g_raid_tr_free_raid1;

static kobj_method_t g_raid_tr_raid1_methods[] = {
        KOBJMETHOD(g_raid_tr_taste,     g_raid_tr_taste_raid1),
        KOBJMETHOD(g_raid_tr_event,     g_raid_tr_event_raid1),
        KOBJMETHOD(g_raid_tr_start,     g_raid_tr_start_raid1),
        KOBJMETHOD(g_raid_tr_stop,      g_raid_tr_stop_raid1),
        KOBJMETHOD(g_raid_tr_iostart,   g_raid_tr_iostart_raid1),
        KOBJMETHOD(g_raid_tr_iodone,    g_raid_tr_iodone_raid1),
        KOBJMETHOD(g_raid_tr_kerneldump, g_raid_tr_kerneldump_raid1),
        KOBJMETHOD(g_raid_tr_locked,    g_raid_tr_locked_raid1),
        KOBJMETHOD(g_raid_tr_idle,      g_raid_tr_idle_raid1),
        KOBJMETHOD(g_raid_tr_free,      g_raid_tr_free_raid1),
        { 0, 0 }
};

static struct g_raid_tr_class g_raid_tr_raid1_class = {
        "RAID1",
        g_raid_tr_raid1_methods,
        sizeof(struct g_raid_tr_raid1_object),
        .trc_enable = 1,
        .trc_priority = 100,
        .trc_accept_unmapped = 1
};

static void g_raid_tr_raid1_rebuild_abort(struct g_raid_tr_object *tr);
static void g_raid_tr_raid1_maybe_rebuild(struct g_raid_tr_object *tr,
    struct g_raid_subdisk *sd);

static int
g_raid_tr_taste_raid1(struct g_raid_tr_object *tr, struct g_raid_volume *vol)
{
        struct g_raid_tr_raid1_object *trs;

        trs = (struct g_raid_tr_raid1_object *)tr;
        if (tr->tro_volume->v_raid_level != G_RAID_VOLUME_RL_RAID1 ||
            (tr->tro_volume->v_raid_level_qualifier != G_RAID_VOLUME_RLQ_R1SM &&
             tr->tro_volume->v_raid_level_qualifier != G_RAID_VOLUME_RLQ_R1MM))
                return (G_RAID_TR_TASTE_FAIL);
        trs->trso_starting = 1;
        return (G_RAID_TR_TASTE_SUCCEED);
}

static int
g_raid_tr_update_state_raid1(struct g_raid_volume *vol,
    struct g_raid_subdisk *sd)
{
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_softc *sc;
        struct g_raid_subdisk *tsd, *bestsd;
        u_int s;
        int i, na, ns;

        sc = vol->v_softc;
        trs = (struct g_raid_tr_raid1_object *)vol->v_tr;
        if (trs->trso_stopping &&
            (trs->trso_flags & TR_RAID1_F_DOING_SOME) == 0)
                s = G_RAID_VOLUME_S_STOPPED;
        else if (trs->trso_starting)
                s = G_RAID_VOLUME_S_STARTING;
        else {
                /* Make sure we have at least one ACTIVE disk. */
                na = g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_ACTIVE);
                if (na == 0) {
                        /*
                         * Critical situation! We have no any active disk!
                         * Choose the best disk we have to make it active.
                         */
                        bestsd = &vol->v_subdisks[0];
                        for (i = 1; i < vol->v_disks_count; i++) {
                                tsd = &vol->v_subdisks[i];
                                if (tsd->sd_state > bestsd->sd_state)
                                        bestsd = tsd;
                                else if (tsd->sd_state == bestsd->sd_state &&
                                    (tsd->sd_state == G_RAID_SUBDISK_S_REBUILD ||
                                     tsd->sd_state == G_RAID_SUBDISK_S_RESYNC) &&
                                    tsd->sd_rebuild_pos > bestsd->sd_rebuild_pos)
                                        bestsd = tsd;
                        }
                        if (bestsd->sd_state >= G_RAID_SUBDISK_S_UNINITIALIZED) {
                                /* We found reasonable candidate. */
                                G_RAID_DEBUG1(1, sc,
                                    "Promote subdisk %s:%d from %s to ACTIVE.",
                                    vol->v_name, bestsd->sd_pos,
                                    g_raid_subdisk_state2str(bestsd->sd_state));
                                g_raid_change_subdisk_state(bestsd,
                                    G_RAID_SUBDISK_S_ACTIVE);
                                g_raid_write_metadata(sc,
                                    vol, bestsd, bestsd->sd_disk);
                        }
                }
                na = g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_ACTIVE);
                ns = g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_STALE) +
                     g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_RESYNC);
                if (na == vol->v_disks_count)
                        s = G_RAID_VOLUME_S_OPTIMAL;
                else if (na + ns == vol->v_disks_count)
                        s = G_RAID_VOLUME_S_SUBOPTIMAL;
                else if (na > 0)
                        s = G_RAID_VOLUME_S_DEGRADED;
                else
                        s = G_RAID_VOLUME_S_BROKEN;
                g_raid_tr_raid1_maybe_rebuild(vol->v_tr, sd);
        }
        if (s != vol->v_state) {
                g_raid_event_send(vol, G_RAID_VOLUME_S_ALIVE(s) ?
                    G_RAID_VOLUME_E_UP : G_RAID_VOLUME_E_DOWN,
                    G_RAID_EVENT_VOLUME);
                g_raid_change_volume_state(vol, s);
                if (!trs->trso_starting && !trs->trso_stopping)
                        g_raid_write_metadata(sc, vol, NULL, NULL);
        }
        return (0);
}

static void
g_raid_tr_raid1_fail_disk(struct g_raid_softc *sc, struct g_raid_subdisk *sd,
    struct g_raid_disk *disk)
{
        /*
         * We don't fail the last disk in the pack, since it still has decent
         * data on it and that's better than failing the disk if it is the root
         * file system.
         *
         * XXX should this be controlled via a tunable?  It makes sense for
         * the volume that has / on it.  I can't think of a case where we'd
         * want the volume to go away on this kind of event.
         */
        if (g_raid_nsubdisks(sd->sd_volume, G_RAID_SUBDISK_S_ACTIVE) == 1 &&
            g_raid_get_subdisk(sd->sd_volume, G_RAID_SUBDISK_S_ACTIVE) == sd)
                return;
        g_raid_fail_disk(sc, sd, disk);
}

static void
g_raid_tr_raid1_rebuild_some(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_subdisk *sd, *good_sd;
        struct bio *bp;

        trs = (struct g_raid_tr_raid1_object *)tr;
        if (trs->trso_flags & TR_RAID1_F_DOING_SOME)
                return;
        sd = trs->trso_failed_sd;
        good_sd = g_raid_get_subdisk(sd->sd_volume, G_RAID_SUBDISK_S_ACTIVE);
        if (good_sd == NULL) {
                g_raid_tr_raid1_rebuild_abort(tr);
                return;
        }
        bp = &trs->trso_bio;
        memset(bp, 0, sizeof(*bp));
        bp->bio_offset = sd->sd_rebuild_pos;
        bp->bio_length = MIN(g_raid1_rebuild_slab,
            sd->sd_size - sd->sd_rebuild_pos);
        bp->bio_data = trs->trso_buffer;
        bp->bio_cmd = BIO_READ;
        bp->bio_cflags = G_RAID_BIO_FLAG_SYNC;
        bp->bio_caller1 = good_sd;
        trs->trso_flags |= TR_RAID1_F_DOING_SOME;
        trs->trso_flags |= TR_RAID1_F_LOCKED;
        g_raid_lock_range(sd->sd_volume,        /* Lock callback starts I/O */
           bp->bio_offset, bp->bio_length, NULL, bp);
}

static void
g_raid_tr_raid1_rebuild_done(struct g_raid_tr_raid1_object *trs)
{
        struct g_raid_volume *vol;
        struct g_raid_subdisk *sd;

        vol = trs->trso_base.tro_volume;
        sd = trs->trso_failed_sd;
        g_raid_write_metadata(vol->v_softc, vol, sd, sd->sd_disk);
        free(trs->trso_buffer, M_TR_RAID1);
        trs->trso_buffer = NULL;
        trs->trso_flags &= ~TR_RAID1_F_DOING_SOME;
        trs->trso_type = TR_RAID1_NONE;
        trs->trso_recover_slabs = 0;
        trs->trso_failed_sd = NULL;
        g_raid_tr_update_state_raid1(vol, NULL);
}

static void
g_raid_tr_raid1_rebuild_finish(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_subdisk *sd;

        trs = (struct g_raid_tr_raid1_object *)tr;
        sd = trs->trso_failed_sd;
        G_RAID_DEBUG1(0, tr->tro_volume->v_softc,
            "Subdisk %s:%d-%s rebuild completed.",
            sd->sd_volume->v_name, sd->sd_pos,
            sd->sd_disk ? g_raid_get_diskname(sd->sd_disk) : "[none]");
        g_raid_change_subdisk_state(sd, G_RAID_SUBDISK_S_ACTIVE);
        sd->sd_rebuild_pos = 0;
        g_raid_tr_raid1_rebuild_done(trs);
}

static void
g_raid_tr_raid1_rebuild_abort(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_subdisk *sd;
        struct g_raid_volume *vol;
        off_t len;

        vol = tr->tro_volume;
        trs = (struct g_raid_tr_raid1_object *)tr;
        sd = trs->trso_failed_sd;
        if (trs->trso_flags & TR_RAID1_F_DOING_SOME) {
                G_RAID_DEBUG1(1, vol->v_softc,
                    "Subdisk %s:%d-%s rebuild is aborting.",
                    sd->sd_volume->v_name, sd->sd_pos,
                    sd->sd_disk ? g_raid_get_diskname(sd->sd_disk) : "[none]");
                trs->trso_flags |= TR_RAID1_F_ABORT;
        } else {
                G_RAID_DEBUG1(0, vol->v_softc,
                    "Subdisk %s:%d-%s rebuild aborted.",
                    sd->sd_volume->v_name, sd->sd_pos,
                    sd->sd_disk ? g_raid_get_diskname(sd->sd_disk) : "[none]");
                trs->trso_flags &= ~TR_RAID1_F_ABORT;
                if (trs->trso_flags & TR_RAID1_F_LOCKED) {
                        trs->trso_flags &= ~TR_RAID1_F_LOCKED;
                        len = MIN(g_raid1_rebuild_slab,
                            sd->sd_size - sd->sd_rebuild_pos);
                        g_raid_unlock_range(tr->tro_volume,
                            sd->sd_rebuild_pos, len);
                }
                g_raid_tr_raid1_rebuild_done(trs);
        }
}

static void
g_raid_tr_raid1_rebuild_start(struct g_raid_tr_object *tr)
{
        struct g_raid_volume *vol;
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_subdisk *sd, *fsd;

        vol = tr->tro_volume;
        trs = (struct g_raid_tr_raid1_object *)tr;
        if (trs->trso_failed_sd) {
                G_RAID_DEBUG1(1, vol->v_softc,
                    "Already rebuild in start rebuild. pos %jd\n",
                    (intmax_t)trs->trso_failed_sd->sd_rebuild_pos);
                return;
        }
        sd = g_raid_get_subdisk(vol, G_RAID_SUBDISK_S_ACTIVE);
        if (sd == NULL) {
                G_RAID_DEBUG1(1, vol->v_softc,
                    "No active disk to rebuild.  night night.");
                return;
        }
        fsd = g_raid_get_subdisk(vol, G_RAID_SUBDISK_S_RESYNC);
        if (fsd == NULL)
                fsd = g_raid_get_subdisk(vol, G_RAID_SUBDISK_S_REBUILD);
        if (fsd == NULL) {
                fsd = g_raid_get_subdisk(vol, G_RAID_SUBDISK_S_STALE);
                if (fsd != NULL) {
                        fsd->sd_rebuild_pos = 0;
                        g_raid_change_subdisk_state(fsd,
                            G_RAID_SUBDISK_S_RESYNC);
                        g_raid_write_metadata(vol->v_softc, vol, fsd, NULL);
                } else {
                        fsd = g_raid_get_subdisk(vol,
                            G_RAID_SUBDISK_S_UNINITIALIZED);
                        if (fsd == NULL)
                                fsd = g_raid_get_subdisk(vol,
                                    G_RAID_SUBDISK_S_NEW);
                        if (fsd != NULL) {
                                fsd->sd_rebuild_pos = 0;
                                g_raid_change_subdisk_state(fsd,
                                    G_RAID_SUBDISK_S_REBUILD);
                                g_raid_write_metadata(vol->v_softc,
                                    vol, fsd, NULL);
                        }
                }
        }
        if (fsd == NULL) {
                G_RAID_DEBUG1(1, vol->v_softc,
                    "No failed disk to rebuild.  night night.");
                return;
        }
        trs->trso_failed_sd = fsd;
        G_RAID_DEBUG1(0, vol->v_softc,
            "Subdisk %s:%d-%s rebuild start at %jd.",
            fsd->sd_volume->v_name, fsd->sd_pos,
            fsd->sd_disk ? g_raid_get_diskname(fsd->sd_disk) : "[none]",
            trs->trso_failed_sd->sd_rebuild_pos);
        trs->trso_type = TR_RAID1_REBUILD;
        trs->trso_buffer = malloc(g_raid1_rebuild_slab, M_TR_RAID1, M_WAITOK);
        trs->trso_meta_update = g_raid1_rebuild_meta_update;
        g_raid_tr_raid1_rebuild_some(tr);
}

static void
g_raid_tr_raid1_maybe_rebuild(struct g_raid_tr_object *tr,
    struct g_raid_subdisk *sd)
{
        struct g_raid_volume *vol;
        struct g_raid_tr_raid1_object *trs;
        int na, nr;

        /*
         * If we're stopping, don't do anything.  If we don't have at least one
         * good disk and one bad disk, we don't do anything.  And if there's a
         * 'good disk' stored in the trs, then we're in progress and we punt.
         * If we make it past all these checks, we need to rebuild.
         */
        vol = tr->tro_volume;
        trs = (struct g_raid_tr_raid1_object *)tr;
        if (trs->trso_stopping)
                return;
        na = g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_ACTIVE);
        nr = g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_REBUILD) +
            g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_RESYNC);
        switch(trs->trso_type) {
        case TR_RAID1_NONE:
                if (na == 0)
                        return;
                if (nr == 0) {
                        nr = g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_NEW) +
                            g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_STALE) +
                            g_raid_nsubdisks(vol, G_RAID_SUBDISK_S_UNINITIALIZED);
                        if (nr == 0)
                                return;
                }
                g_raid_tr_raid1_rebuild_start(tr);
                break;
        case TR_RAID1_REBUILD:
                if (na == 0 || nr == 0 || trs->trso_failed_sd == sd)
                        g_raid_tr_raid1_rebuild_abort(tr);
                break;
        case TR_RAID1_RESYNC:
                break;
        }
}

static int
g_raid_tr_event_raid1(struct g_raid_tr_object *tr,
    struct g_raid_subdisk *sd, u_int event)
{

        g_raid_tr_update_state_raid1(tr->tro_volume, sd);
        return (0);
}

static int
g_raid_tr_start_raid1(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_volume *vol;

        trs = (struct g_raid_tr_raid1_object *)tr;
        vol = tr->tro_volume;
        trs->trso_starting = 0;
        g_raid_tr_update_state_raid1(vol, NULL);
        return (0);
}

static int
g_raid_tr_stop_raid1(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;
        struct g_raid_volume *vol;

        trs = (struct g_raid_tr_raid1_object *)tr;
        vol = tr->tro_volume;
        trs->trso_starting = 0;
        trs->trso_stopping = 1;
        g_raid_tr_update_state_raid1(vol, NULL);
        return (0);
}

/*
 * Select the disk to read from.  Take into account: subdisk state, running
 * error recovery, average disk load, head position and possible cache hits.
 */
#define ABS(x)          (((x) >= 0) ? (x) : (-(x)))
static struct g_raid_subdisk *
g_raid_tr_raid1_select_read_disk(struct g_raid_volume *vol, struct bio *bp,
    u_int mask)
{
        struct g_raid_subdisk *sd, *best;
        int i, prio, bestprio;

        best = NULL;
        bestprio = INT_MAX;
        for (i = 0; i < vol->v_disks_count; i++) {
                sd = &vol->v_subdisks[i];
                if (sd->sd_state != G_RAID_SUBDISK_S_ACTIVE &&
                    ((sd->sd_state != G_RAID_SUBDISK_S_REBUILD &&
                      sd->sd_state != G_RAID_SUBDISK_S_RESYNC) ||
                     bp->bio_offset + bp->bio_length > sd->sd_rebuild_pos))
                        continue;
                if ((mask & (1 << i)) != 0)
                        continue;
                prio = G_RAID_SUBDISK_LOAD(sd);
                prio += min(sd->sd_recovery, 255) << 22;
                prio += (G_RAID_SUBDISK_S_ACTIVE - sd->sd_state) << 16;
                /* If disk head is precisely in position - highly prefer it. */
                if (G_RAID_SUBDISK_POS(sd) == bp->bio_offset)
                        prio -= 2 * G_RAID_SUBDISK_LOAD_SCALE;
                else
                /* If disk head is close to position - prefer it. */
                if (ABS(G_RAID_SUBDISK_POS(sd) - bp->bio_offset) <
                    G_RAID_SUBDISK_TRACK_SIZE)
                        prio -= 1 * G_RAID_SUBDISK_LOAD_SCALE;
                if (prio < bestprio) {
                        best = sd;
                        bestprio = prio;
                }
        }
        return (best);
}

static void
g_raid_tr_iostart_raid1_read(struct g_raid_tr_object *tr, struct bio *bp)
{
        struct g_raid_subdisk *sd;
        struct bio *cbp;

        sd = g_raid_tr_raid1_select_read_disk(tr->tro_volume, bp, 0);
        KASSERT(sd != NULL, ("No active disks in volume %s.",
                tr->tro_volume->v_name));

        cbp = g_clone_bio(bp);
        if (cbp == NULL) {
                g_raid_iodone(bp, ENOMEM);
                return;
        }

        g_raid_subdisk_iostart(sd, cbp);
}

static void
g_raid_tr_iostart_raid1_write(struct g_raid_tr_object *tr, struct bio *bp)
{
        struct g_raid_volume *vol;
        struct g_raid_subdisk *sd;
        struct bio_queue_head queue;
        struct bio *cbp;
        int i;

        vol = tr->tro_volume;

        /*
         * Allocate all bios before sending any request, so we can return
         * ENOMEM in nice and clean way.
         */
        bioq_init(&queue);
        for (i = 0; i < vol->v_disks_count; i++) {
                sd = &vol->v_subdisks[i];
                switch (sd->sd_state) {
                case G_RAID_SUBDISK_S_ACTIVE:
                        break;
                case G_RAID_SUBDISK_S_REBUILD:
                        /*
                         * When rebuilding, only part of this subdisk is
                         * writable, the rest will be written as part of the
                         * that process.
                         */
                        if (bp->bio_offset >= sd->sd_rebuild_pos)
                                continue;
                        break;
                case G_RAID_SUBDISK_S_STALE:
                case G_RAID_SUBDISK_S_RESYNC:
                        /*
                         * Resyncing still writes on the theory that the
                         * resync'd disk is very close and writing it will
                         * keep it that way better if we keep up while
                         * resyncing.
                         */
                        break;
                default:
                        continue;
                }
                cbp = g_clone_bio(bp);
                if (cbp == NULL)
                        goto failure;
                cbp->bio_caller1 = sd;
                bioq_insert_tail(&queue, cbp);
        }
        while ((cbp = bioq_takefirst(&queue)) != NULL) {
                sd = cbp->bio_caller1;
                cbp->bio_caller1 = NULL;
                g_raid_subdisk_iostart(sd, cbp);
        }
        return;
failure:
        while ((cbp = bioq_takefirst(&queue)) != NULL)
                g_destroy_bio(cbp);
        if (bp->bio_error == 0)
                bp->bio_error = ENOMEM;
        g_raid_iodone(bp, bp->bio_error);
}

static void
g_raid_tr_iostart_raid1(struct g_raid_tr_object *tr, struct bio *bp)
{
        struct g_raid_volume *vol;
        struct g_raid_tr_raid1_object *trs;

        vol = tr->tro_volume;
        trs = (struct g_raid_tr_raid1_object *)tr;
        if (vol->v_state != G_RAID_VOLUME_S_OPTIMAL &&
            vol->v_state != G_RAID_VOLUME_S_SUBOPTIMAL &&
            vol->v_state != G_RAID_VOLUME_S_DEGRADED) {
                g_raid_iodone(bp, EIO);
                return;
        }
        /*
         * If we're rebuilding, squeeze in rebuild activity every so often,
         * even when the disk is busy.  Be sure to only count real I/O
         * to the disk.  All 'SPECIAL' I/O is traffic generated to the disk
         * by this module.
         */
        if (trs->trso_failed_sd != NULL &&
            !(bp->bio_cflags & G_RAID_BIO_FLAG_SPECIAL)) {
                /* Make this new or running now round short. */
                trs->trso_recover_slabs = 0;
                if (--trs->trso_fair_io <= 0) {
                        trs->trso_fair_io = g_raid1_rebuild_fair_io;
                        g_raid_tr_raid1_rebuild_some(tr);
                }
        }
        switch (bp->bio_cmd) {
        case BIO_READ:
                g_raid_tr_iostart_raid1_read(tr, bp);
                break;
        case BIO_WRITE:
        case BIO_DELETE:
                g_raid_tr_iostart_raid1_write(tr, bp);
                break;
        case BIO_SPEEDUP:
        case BIO_FLUSH:
                g_raid_tr_flush_common(tr, bp);
                break;
        default:
                KASSERT(1 == 0, ("Invalid command here: %u (volume=%s)",
                    bp->bio_cmd, vol->v_name));
                break;
        }
}

static void
g_raid_tr_iodone_raid1(struct g_raid_tr_object *tr,
    struct g_raid_subdisk *sd, struct bio *bp)
{
        struct bio *cbp;
        struct g_raid_subdisk *nsd;
        struct g_raid_volume *vol;
        struct bio *pbp;
        struct g_raid_tr_raid1_object *trs;
        uintptr_t *mask;
        int error, do_write;

        trs = (struct g_raid_tr_raid1_object *)tr;
        vol = tr->tro_volume;
        if (bp->bio_cflags & G_RAID_BIO_FLAG_SYNC) {
                /*
                 * This operation is part of a rebuild or resync operation.
                 * See what work just got done, then schedule the next bit of
                 * work, if any.  Rebuild/resync is done a little bit at a
                 * time.  Either when a timeout happens, or after we get a
                 * bunch of I/Os to the disk (to make sure an active system
                 * will complete in a sane amount of time).
                 *
                 * We are setup to do differing amounts of work for each of
                 * these cases.  so long as the slabs is smallish (less than
                 * 50 or so, I'd guess, but that's just a WAG), we shouldn't
                 * have any bio starvation issues.  For active disks, we do
                 * 5MB of data, for inactive ones, we do 50MB.
                 */
                if (trs->trso_type == TR_RAID1_REBUILD) {
                        if (bp->bio_cmd == BIO_READ) {
                                /* Immediately abort rebuild, if requested. */
                                if (trs->trso_flags & TR_RAID1_F_ABORT) {
                                        trs->trso_flags &= ~TR_RAID1_F_DOING_SOME;
                                        g_raid_tr_raid1_rebuild_abort(tr);
                                        return;
                                }

                                /* On read error, skip and cross fingers. */
                                if (bp->bio_error != 0) {
                                        G_RAID_LOGREQ(0, bp,
                                            "Read error during rebuild (%d), "
                                            "possible data loss!",
                                            bp->bio_error);
                                        goto rebuild_round_done;
                                }

                                /*
                                 * The read operation finished, queue the
                                 * write and get out.
                                 */
                                G_RAID_LOGREQ(4, bp, "rebuild read done. %d",
                                    bp->bio_error);
                                bp->bio_cmd = BIO_WRITE;
                                bp->bio_cflags = G_RAID_BIO_FLAG_SYNC;
                                G_RAID_LOGREQ(4, bp, "Queueing rebuild write.");
                                g_raid_subdisk_iostart(trs->trso_failed_sd, bp);
                        } else {
                                /*
                                 * The write operation just finished.  Do
                                 * another.  We keep cloning the master bio
                                 * since it has the right buffers allocated to
                                 * it.
                                 */
                                G_RAID_LOGREQ(4, bp,
                                    "rebuild write done. Error %d",
                                    bp->bio_error);
                                nsd = trs->trso_failed_sd;
                                if (bp->bio_error != 0 ||
                                    trs->trso_flags & TR_RAID1_F_ABORT) {
                                        if ((trs->trso_flags &
                                            TR_RAID1_F_ABORT) == 0) {
                                                g_raid_tr_raid1_fail_disk(sd->sd_softc,
                                                    nsd, nsd->sd_disk);
                                        }
                                        trs->trso_flags &= ~TR_RAID1_F_DOING_SOME;
                                        g_raid_tr_raid1_rebuild_abort(tr);
                                        return;
                                }
rebuild_round_done:
                                nsd = trs->trso_failed_sd;
                                trs->trso_flags &= ~TR_RAID1_F_LOCKED;
                                g_raid_unlock_range(sd->sd_volume,
                                    bp->bio_offset, bp->bio_length);
                                nsd->sd_rebuild_pos += bp->bio_length;
                                if (nsd->sd_rebuild_pos >= nsd->sd_size) {
                                        g_raid_tr_raid1_rebuild_finish(tr);
                                        return;
                                }

                                /* Abort rebuild if we are stopping */
                                if (trs->trso_stopping) {
                                        trs->trso_flags &= ~TR_RAID1_F_DOING_SOME;
                                        g_raid_tr_raid1_rebuild_abort(tr);
                                        return;
                                }

                                if (--trs->trso_meta_update <= 0) {
                                        g_raid_write_metadata(vol->v_softc,
                                            vol, nsd, nsd->sd_disk);
                                        trs->trso_meta_update =
                                            g_raid1_rebuild_meta_update;
                                }
                                trs->trso_flags &= ~TR_RAID1_F_DOING_SOME;
                                if (--trs->trso_recover_slabs <= 0)
                                        return;
                                g_raid_tr_raid1_rebuild_some(tr);
                        }
                } else if (trs->trso_type == TR_RAID1_RESYNC) {
                        /*
                         * read good sd, read bad sd in parallel.  when both
                         * done, compare the buffers.  write good to the bad
                         * if different.  do the next bit of work.
                         */
                        panic("Somehow, we think we're doing a resync");
                }
                return;
        }
        pbp = bp->bio_parent;
        pbp->bio_inbed++;
        if (bp->bio_cmd == BIO_READ && bp->bio_error != 0) {
                /*
                 * Read failed on first drive.  Retry the read error on
                 * another disk drive, if available, before erroring out the
                 * read.
                 */
                sd->sd_disk->d_read_errs++;
                G_RAID_LOGREQ(0, bp,
                    "Read error (%d), %d read errors total",
                    bp->bio_error, sd->sd_disk->d_read_errs);

                /*
                 * If there are too many read errors, we move to degraded.
                 * XXX Do we want to FAIL the drive (eg, make the user redo
                 * everything to get it back in sync), or just degrade the
                 * drive, which kicks off a resync?
                 */
                do_write = 1;
                if (sd->sd_disk->d_read_errs > g_raid_read_err_thresh) {
                        g_raid_tr_raid1_fail_disk(sd->sd_softc, sd, sd->sd_disk);
                        if (pbp->bio_children == 1)
                                do_write = 0;
                }

                /*
                 * Find the other disk, and try to do the I/O to it.
                 */
                mask = (uintptr_t *)(&pbp->bio_driver2);
                if (pbp->bio_children == 1) {
                        /* Save original subdisk. */
                        pbp->bio_driver1 = do_write ? sd : NULL;
                        *mask = 0;
                }
                *mask |= 1 << sd->sd_pos;
                nsd = g_raid_tr_raid1_select_read_disk(vol, pbp, *mask);
                if (nsd != NULL && (cbp = g_clone_bio(pbp)) != NULL) {
                        g_destroy_bio(bp);
                        G_RAID_LOGREQ(2, cbp, "Retrying read from %d",
                            nsd->sd_pos);
                        if (pbp->bio_children == 2 && do_write) {
                                sd->sd_recovery++;
                                cbp->bio_caller1 = nsd;
                                pbp->bio_pflags = G_RAID_BIO_FLAG_LOCKED;
                                /* Lock callback starts I/O */
                                g_raid_lock_range(sd->sd_volume,
                                    cbp->bio_offset, cbp->bio_length, pbp, cbp);
                        } else {
                                g_raid_subdisk_iostart(nsd, cbp);
                        }
                        return;
                }
                /*
                 * We can't retry.  Return the original error by falling
                 * through.  This will happen when there's only one good disk.
                 * We don't need to fail the raid, since its actual state is
                 * based on the state of the subdisks.
                 */
                G_RAID_LOGREQ(2, bp, "Couldn't retry read, failing it");
        }
        if (bp->bio_cmd == BIO_READ &&
            bp->bio_error == 0 &&
            pbp->bio_children > 1 &&
            pbp->bio_driver1 != NULL) {
                /*
                 * If it was a read, and bio_children is >1, then we just
                 * recovered the data from the second drive.  We should try to
                 * write that data to the first drive if sector remapping is
                 * enabled.  A write should put the data in a new place on the
                 * disk, remapping the bad sector.  Do we need to do that by
                 * queueing a request to the main worker thread?  It doesn't
                 * affect the return code of this current read, and can be
                 * done at our leisure.  However, to make the code simpler, it
                 * is done synchronously.
                 */
                G_RAID_LOGREQ(3, bp, "Recovered data from other drive");
                cbp = g_clone_bio(pbp);
                if (cbp != NULL) {
                        g_destroy_bio(bp);
                        cbp->bio_cmd = BIO_WRITE;
                        cbp->bio_cflags = G_RAID_BIO_FLAG_REMAP;
                        G_RAID_LOGREQ(2, cbp,
                            "Attempting bad sector remap on failing drive.");
                        g_raid_subdisk_iostart(pbp->bio_driver1, cbp);
                        return;
                }
        }
        if (pbp->bio_pflags & G_RAID_BIO_FLAG_LOCKED) {
                /*
                 * We're done with a recovery, mark the range as unlocked.
                 * For any write errors, we aggressively fail the disk since
                 * there was both a READ and a WRITE error at this location.
                 * Both types of errors generally indicates the drive is on
                 * the verge of total failure anyway.  Better to stop trusting
                 * it now.  However, we need to reset error to 0 in that case
                 * because we're not failing the original I/O which succeeded.
                 */
                if (bp->bio_cmd == BIO_WRITE && bp->bio_error) {
                        G_RAID_LOGREQ(0, bp, "Remap write failed: "
                            "failing subdisk.");
                        g_raid_tr_raid1_fail_disk(sd->sd_softc, sd, sd->sd_disk);
                        bp->bio_error = 0;
                }
                if (pbp->bio_driver1 != NULL) {
                        ((struct g_raid_subdisk *)pbp->bio_driver1)
                            ->sd_recovery--;
                }
                G_RAID_LOGREQ(2, bp, "REMAP done %d.", bp->bio_error);
                g_raid_unlock_range(sd->sd_volume, bp->bio_offset,
                    bp->bio_length);
        }
        if (pbp->bio_cmd != BIO_READ) {
                if (pbp->bio_inbed == 1 || pbp->bio_error != 0)
                        pbp->bio_error = bp->bio_error;
                if (pbp->bio_cmd == BIO_WRITE && bp->bio_error != 0) {
                        G_RAID_LOGREQ(0, bp, "Write failed: failing subdisk.");
                        g_raid_tr_raid1_fail_disk(sd->sd_softc, sd, sd->sd_disk);
                }
                error = pbp->bio_error;
        } else
                error = bp->bio_error;
        g_destroy_bio(bp);
        if (pbp->bio_children == pbp->bio_inbed) {
                pbp->bio_completed = pbp->bio_length;
                g_raid_iodone(pbp, error);
        }
}

static int
g_raid_tr_kerneldump_raid1(struct g_raid_tr_object *tr, void *virtual,
    off_t offset, size_t length)
{
        struct g_raid_volume *vol;
        struct g_raid_subdisk *sd;
        int error, i, ok;

        vol = tr->tro_volume;
        error = 0;
        ok = 0;
        for (i = 0; i < vol->v_disks_count; i++) {
                sd = &vol->v_subdisks[i];
                switch (sd->sd_state) {
                case G_RAID_SUBDISK_S_ACTIVE:
                        break;
                case G_RAID_SUBDISK_S_REBUILD:
                        /*
                         * When rebuilding, only part of this subdisk is
                         * writable, the rest will be written as part of the
                         * that process.
                         */
                        if (offset >= sd->sd_rebuild_pos)
                                continue;
                        break;
                case G_RAID_SUBDISK_S_STALE:
                case G_RAID_SUBDISK_S_RESYNC:
                        /*
                         * Resyncing still writes on the theory that the
                         * resync'd disk is very close and writing it will
                         * keep it that way better if we keep up while
                         * resyncing.
                         */
                        break;
                default:
                        continue;
                }
                error = g_raid_subdisk_kerneldump(sd, virtual, offset, length);
                if (error == 0)
                        ok++;
        }
        return (ok > 0 ? 0 : error);
}

static int
g_raid_tr_locked_raid1(struct g_raid_tr_object *tr, void *argp)
{
        struct bio *bp;
        struct g_raid_subdisk *sd;

        bp = (struct bio *)argp;
        sd = (struct g_raid_subdisk *)bp->bio_caller1;
        g_raid_subdisk_iostart(sd, bp);

        return (0);
}

static int
g_raid_tr_idle_raid1(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;

        trs = (struct g_raid_tr_raid1_object *)tr;
        trs->trso_fair_io = g_raid1_rebuild_fair_io;
        trs->trso_recover_slabs = g_raid1_rebuild_cluster_idle;
        if (trs->trso_type == TR_RAID1_REBUILD)
                g_raid_tr_raid1_rebuild_some(tr);
        return (0);
}

static int
g_raid_tr_free_raid1(struct g_raid_tr_object *tr)
{
        struct g_raid_tr_raid1_object *trs;

        trs = (struct g_raid_tr_raid1_object *)tr;

        if (trs->trso_buffer != NULL) {
                free(trs->trso_buffer, M_TR_RAID1);
                trs->trso_buffer = NULL;
        }
        return (0);
}

G_RAID_TR_DECLARE(raid1, "RAID1");