/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@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/systm.h>
#include <sys/bio.h>
#include <sys/eventhandler.h>
#include <sys/fail.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/reboot.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/sx.h>
#include <sys/sysctl.h>

#include <geom/geom.h>
#include <geom/geom_dbg.h>
#include <geom/geom_disk.h>
#include <geom/mirror/g_mirror.h>

FEATURE(geom_mirror, "GEOM mirroring support");

static MALLOC_DEFINE(M_MIRROR, "mirror_data", "GEOM_MIRROR Data");

SYSCTL_DECL(_kern_geom);
static SYSCTL_NODE(_kern_geom, OID_AUTO, mirror, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "GEOM_MIRROR stuff");
int g_mirror_debug = 0;
SYSCTL_INT(_kern_geom_mirror, OID_AUTO, debug, CTLFLAG_RWTUN, &g_mirror_debug, 0,
    "Debug level");
bool g_launch_mirror_before_timeout = true;
SYSCTL_BOOL(_kern_geom_mirror, OID_AUTO, launch_mirror_before_timeout,
    CTLFLAG_RWTUN, &g_launch_mirror_before_timeout, 0,
    "If false, force gmirror to wait out the full kern.geom.mirror.timeout "
    "before launching mirrors");
static u_int g_mirror_timeout = 4;
SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, timeout, CTLFLAG_RWTUN, &g_mirror_timeout,
    0, "Time to wait on all mirror components");
static u_int g_mirror_idletime = 5;
SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, idletime, CTLFLAG_RWTUN,
    &g_mirror_idletime, 0, "Mark components as clean when idling");
static u_int g_mirror_disconnect_on_failure = 1;
SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, disconnect_on_failure, CTLFLAG_RWTUN,
    &g_mirror_disconnect_on_failure, 0, "Disconnect component on I/O failure.");
static u_int g_mirror_syncreqs = 2;
SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, sync_requests, CTLFLAG_RDTUN,
    &g_mirror_syncreqs, 0, "Parallel synchronization I/O requests.");
static u_int g_mirror_sync_period = 5;
SYSCTL_UINT(_kern_geom_mirror, OID_AUTO, sync_update_period, CTLFLAG_RWTUN,
    &g_mirror_sync_period, 0,
    "Metadata update period during synchronization, in seconds");

#define MSLEEP(ident, mtx, priority, wmesg, timeout)    do {            \
        G_MIRROR_DEBUG(4, "%s: Sleeping %p.", __func__, (ident));       \
        msleep((ident), (mtx), (priority), (wmesg), (timeout));         \
        G_MIRROR_DEBUG(4, "%s: Woken up %p.", __func__, (ident));       \
} while (0)

static eventhandler_tag g_mirror_post_sync = NULL;
static int g_mirror_shutdown = 0;

static g_ctl_destroy_geom_t g_mirror_destroy_geom;
static g_taste_t g_mirror_taste;
static g_init_t g_mirror_init;
static g_fini_t g_mirror_fini;
static g_provgone_t g_mirror_providergone;
static g_resize_t g_mirror_resize;

struct g_class g_mirror_class = {
        .name = G_MIRROR_CLASS_NAME,
        .version = G_VERSION,
        .ctlreq = g_mirror_config,
        .taste = g_mirror_taste,
        .destroy_geom = g_mirror_destroy_geom,
        .init = g_mirror_init,
        .fini = g_mirror_fini,
        .providergone = g_mirror_providergone,
        .resize = g_mirror_resize
};

static void g_mirror_destroy_provider(struct g_mirror_softc *sc);
static int g_mirror_update_disk(struct g_mirror_disk *disk, u_int state);
static void g_mirror_update_device(struct g_mirror_softc *sc, bool force);
static void g_mirror_dumpconf(struct sbuf *sb, const char *indent,
    struct g_geom *gp, struct g_consumer *cp, struct g_provider *pp);
static void g_mirror_timeout_drain(struct g_mirror_softc *sc);
static int g_mirror_refresh_device(struct g_mirror_softc *sc,
    const struct g_provider *pp, const struct g_mirror_metadata *md);
static void g_mirror_sync_reinit(const struct g_mirror_disk *disk,
    struct bio *bp, off_t offset);
static void g_mirror_sync_stop(struct g_mirror_disk *disk, int type);
static void g_mirror_register_request(struct g_mirror_softc *sc,
    struct bio *bp);
static void g_mirror_sync_release(struct g_mirror_softc *sc);

static const char *
g_mirror_disk_state2str(int state)
{

        switch (state) {
        case G_MIRROR_DISK_STATE_NONE:
                return ("NONE");
        case G_MIRROR_DISK_STATE_NEW:
                return ("NEW");
        case G_MIRROR_DISK_STATE_ACTIVE:
                return ("ACTIVE");
        case G_MIRROR_DISK_STATE_STALE:
                return ("STALE");
        case G_MIRROR_DISK_STATE_SYNCHRONIZING:
                return ("SYNCHRONIZING");
        case G_MIRROR_DISK_STATE_DISCONNECTED:
                return ("DISCONNECTED");
        case G_MIRROR_DISK_STATE_DESTROY:
                return ("DESTROY");
        default:
                return ("INVALID");
        }
}

static const char *
g_mirror_device_state2str(int state)
{

        switch (state) {
        case G_MIRROR_DEVICE_STATE_STARTING:
                return ("STARTING");
        case G_MIRROR_DEVICE_STATE_RUNNING:
                return ("RUNNING");
        default:
                return ("INVALID");
        }
}

static const char *
g_mirror_get_diskname(struct g_mirror_disk *disk)
{

        if (disk->d_consumer == NULL || disk->d_consumer->provider == NULL)
                return ("[unknown]");
        return (disk->d_name);
}

/*
 * --- Events handling functions ---
 * Events in geom_mirror are used to maintain disks and device status
 * from one thread to simplify locking.
 */
static void
g_mirror_event_free(struct g_mirror_event *ep)
{

        free(ep, M_MIRROR);
}

static int
g_mirror_event_dispatch(struct g_mirror_event *ep, void *arg, int state,
    int flags)
{
        struct g_mirror_softc *sc;
        struct g_mirror_disk *disk;
        int error;

        G_MIRROR_DEBUG(4, "%s: Sending event %p.", __func__, ep);
        if ((flags & G_MIRROR_EVENT_DEVICE) != 0) {
                disk = NULL;
                sc = arg;
        } else {
                disk = arg;
                sc = disk->d_softc;
        }
        ep->e_disk = disk;
        ep->e_state = state;
        ep->e_flags = flags;
        ep->e_error = 0;
        mtx_lock(&sc->sc_events_mtx);
        TAILQ_INSERT_TAIL(&sc->sc_events, ep, e_next);
        mtx_unlock(&sc->sc_events_mtx);
        G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__, sc);
        mtx_lock(&sc->sc_queue_mtx);
        wakeup(sc);
        mtx_unlock(&sc->sc_queue_mtx);
        if ((flags & G_MIRROR_EVENT_DONTWAIT) != 0)
                return (0);
        G_MIRROR_DEBUG(4, "%s: Sleeping %p.", __func__, ep);
        sx_xunlock(&sc->sc_lock);
        while ((ep->e_flags & G_MIRROR_EVENT_DONE) == 0) {
                mtx_lock(&sc->sc_events_mtx);
                MSLEEP(ep, &sc->sc_events_mtx, PRIBIO | PDROP, "m:event",
                    hz * 5);
        }
        error = ep->e_error;
        g_mirror_event_free(ep);
        sx_xlock(&sc->sc_lock);
        return (error);
}

int
g_mirror_event_send(void *arg, int state, int flags)
{
        struct g_mirror_event *ep;

        ep = malloc(sizeof(*ep), M_MIRROR, M_WAITOK);
        return (g_mirror_event_dispatch(ep, arg, state, flags));
}

static struct g_mirror_event *
g_mirror_event_first(struct g_mirror_softc *sc)
{
        struct g_mirror_event *ep;

        mtx_lock(&sc->sc_events_mtx);
        ep = TAILQ_FIRST(&sc->sc_events);
        mtx_unlock(&sc->sc_events_mtx);
        return (ep);
}

static void
g_mirror_event_remove(struct g_mirror_softc *sc, struct g_mirror_event *ep)
{

        mtx_lock(&sc->sc_events_mtx);
        TAILQ_REMOVE(&sc->sc_events, ep, e_next);
        mtx_unlock(&sc->sc_events_mtx);
}

static void
g_mirror_event_cancel(struct g_mirror_disk *disk)
{
        struct g_mirror_softc *sc;
        struct g_mirror_event *ep, *tmpep;

        sc = disk->d_softc;
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        mtx_lock(&sc->sc_events_mtx);
        TAILQ_FOREACH_SAFE(ep, &sc->sc_events, e_next, tmpep) {
                if ((ep->e_flags & G_MIRROR_EVENT_DEVICE) != 0)
                        continue;
                if (ep->e_disk != disk)
                        continue;
                TAILQ_REMOVE(&sc->sc_events, ep, e_next);
                if ((ep->e_flags & G_MIRROR_EVENT_DONTWAIT) != 0)
                        g_mirror_event_free(ep);
                else {
                        ep->e_error = ECANCELED;
                        wakeup(ep);
                }
        }
        mtx_unlock(&sc->sc_events_mtx);
}

/*
 * Return the number of disks in given state.
 * If state is equal to -1, count all connected disks.
 */
u_int
g_mirror_ndisks(struct g_mirror_softc *sc, int state)
{
        struct g_mirror_disk *disk;
        u_int n = 0;

        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (state == -1 || disk->d_state == state)
                        n++;
        }
        return (n);
}

/*
 * Find a disk in mirror by its disk ID.
 */
static struct g_mirror_disk *
g_mirror_id2disk(struct g_mirror_softc *sc, uint32_t id)
{
        struct g_mirror_disk *disk;

        sx_assert(&sc->sc_lock, SX_XLOCKED);

        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_id == id)
                        return (disk);
        }
        return (NULL);
}

static u_int
g_mirror_nrequests(struct g_mirror_softc *sc, struct g_consumer *cp)
{
        struct bio *bp;
        u_int nreqs = 0;

        mtx_lock(&sc->sc_queue_mtx);
        TAILQ_FOREACH(bp, &sc->sc_queue, bio_queue) {
                if (bp->bio_from == cp)
                        nreqs++;
        }
        mtx_unlock(&sc->sc_queue_mtx);
        return (nreqs);
}

static int
g_mirror_is_busy(struct g_mirror_softc *sc, struct g_consumer *cp)
{

        if (cp->index > 0) {
                G_MIRROR_DEBUG(2,
                    "I/O requests for %s exist, can't destroy it now.",
                    cp->provider->name);
                return (1);
        }
        if (g_mirror_nrequests(sc, cp) > 0) {
                G_MIRROR_DEBUG(2,
                    "I/O requests for %s in queue, can't destroy it now.",
                    cp->provider->name);
                return (1);
        }
        return (0);
}

static void
g_mirror_destroy_consumer(void *arg, int flags __unused)
{
        struct g_consumer *cp;

        g_topology_assert();

        cp = arg;
        G_MIRROR_DEBUG(1, "Consumer %s destroyed.", cp->provider->name);
        g_detach(cp);
        g_destroy_consumer(cp);
}

static void
g_mirror_kill_consumer(struct g_mirror_softc *sc, struct g_consumer *cp)
{
        struct g_provider *pp;
        int retaste_wait;

        g_topology_assert();

        cp->private = NULL;
        if (g_mirror_is_busy(sc, cp))
                return;
        pp = cp->provider;
        retaste_wait = 0;
        if (cp->acw == 1) {
                if ((pp->geom->flags & G_GEOM_WITHER) == 0)
                        retaste_wait = 1;
        }
        G_MIRROR_DEBUG(2, "Access %s r%dw%de%d = %d", pp->name, -cp->acr,
            -cp->acw, -cp->ace, 0);
        if (cp->acr > 0 || cp->acw > 0 || cp->ace > 0)
                g_access(cp, -cp->acr, -cp->acw, -cp->ace);
        if (retaste_wait) {
                /*
                 * After retaste event was send (inside g_access()), we can send
                 * event to detach and destroy consumer.
                 * A class, which has consumer to the given provider connected
                 * will not receive retaste event for the provider.
                 * This is the way how I ignore retaste events when I close
                 * consumers opened for write: I detach and destroy consumer
                 * after retaste event is sent.
                 */
                g_post_event(g_mirror_destroy_consumer, cp, M_WAITOK, NULL);
                return;
        }
        G_MIRROR_DEBUG(1, "Consumer %s destroyed.", pp->name);
        g_detach(cp);
        g_destroy_consumer(cp);
}

static int
g_mirror_connect_disk(struct g_mirror_disk *disk, struct g_provider *pp)
{
        struct g_consumer *cp;
        int error;

        g_topology_assert_not();
        KASSERT(disk->d_consumer == NULL,
            ("Disk already connected (device %s).", disk->d_softc->sc_name));

        g_topology_lock();
        cp = g_new_consumer(disk->d_softc->sc_geom);
        cp->flags |= G_CF_DIRECT_RECEIVE;
        error = g_attach(cp, pp);
        if (error != 0) {
                g_destroy_consumer(cp);
                g_topology_unlock();
                return (error);
        }
        error = g_access(cp, 1, 1, 1);
        if (error != 0) {
                g_detach(cp);
                g_destroy_consumer(cp);
                g_topology_unlock();
                G_MIRROR_DEBUG(0, "Cannot open consumer %s (error=%d).",
                    pp->name, error);
                return (error);
        }
        g_topology_unlock();
        disk->d_consumer = cp;
        disk->d_consumer->private = disk;
        disk->d_consumer->index = 0;

        G_MIRROR_DEBUG(2, "Disk %s connected.", g_mirror_get_diskname(disk));
        return (0);
}

static void
g_mirror_disconnect_consumer(struct g_mirror_softc *sc, struct g_consumer *cp)
{

        g_topology_assert();

        if (cp == NULL)
                return;
        if (cp->provider != NULL)
                g_mirror_kill_consumer(sc, cp);
        else
                g_destroy_consumer(cp);
}

/*
 * Initialize disk. This means allocate memory, create consumer, attach it
 * to the provider and open access (r1w1e1) to it.
 */
static struct g_mirror_disk *
g_mirror_init_disk(struct g_mirror_softc *sc, struct g_provider *pp,
    struct g_mirror_metadata *md, int *errorp)
{
        struct g_mirror_disk *disk;
        int i, error;

        disk = malloc(sizeof(*disk), M_MIRROR, M_NOWAIT | M_ZERO);
        if (disk == NULL) {
                error = ENOMEM;
                goto fail;
        }
        disk->d_softc = sc;
        error = g_mirror_connect_disk(disk, pp);
        if (error != 0)
                goto fail;
        disk->d_id = md->md_did;
        disk->d_state = G_MIRROR_DISK_STATE_NONE;
        disk->d_priority = md->md_priority;
        disk->d_flags = md->md_dflags;
        error = g_getattr("GEOM::candelete", disk->d_consumer, &i);
        if (error == 0 && i != 0)
                disk->d_flags |= G_MIRROR_DISK_FLAG_CANDELETE;
        error = g_getattr("GEOM::rotation_rate", disk->d_consumer,
                &disk->d_rotation_rate);
        if (error)
                disk->d_rotation_rate = DISK_RR_UNKNOWN;
        if (md->md_provider[0] != '\0')
                disk->d_flags |= G_MIRROR_DISK_FLAG_HARDCODED;
        disk->d_sync.ds_consumer = NULL;
        disk->d_sync.ds_offset = md->md_sync_offset;
        disk->d_sync.ds_offset_done = md->md_sync_offset;
        disk->d_sync.ds_update_ts = time_uptime;
        disk->d_genid = md->md_genid;
        disk->d_sync.ds_syncid = md->md_syncid;
        disk->d_init_ndisks = md->md_all;
        disk->d_init_slice = md->md_slice;
        disk->d_init_balance = md->md_balance;
        disk->d_init_mediasize = md->md_mediasize;
        if (errorp != NULL)
                *errorp = 0;
        return (disk);
fail:
        if (errorp != NULL)
                *errorp = error;
        if (disk != NULL)
                free(disk, M_MIRROR);
        return (NULL);
}

static void
g_mirror_destroy_disk(struct g_mirror_disk *disk)
{
        struct g_mirror_softc *sc;

        g_topology_assert_not();
        sc = disk->d_softc;
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        g_topology_lock();
        LIST_REMOVE(disk, d_next);
        g_topology_unlock();
        g_mirror_event_cancel(disk);
        if (sc->sc_hint == disk)
                sc->sc_hint = NULL;
        switch (disk->d_state) {
        case G_MIRROR_DISK_STATE_SYNCHRONIZING:
                g_mirror_sync_stop(disk, 1);
                /* FALLTHROUGH */
        case G_MIRROR_DISK_STATE_NEW:
        case G_MIRROR_DISK_STATE_STALE:
        case G_MIRROR_DISK_STATE_ACTIVE:
                g_topology_lock();
                g_mirror_disconnect_consumer(sc, disk->d_consumer);
                g_topology_unlock();
                free(disk, M_MIRROR);
                break;
        default:
                KASSERT(0 == 1, ("Wrong disk state (%s, %s).",
                    g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
        }
}

static void
g_mirror_free_device(struct g_mirror_softc *sc)
{

        g_topology_assert();

        mtx_destroy(&sc->sc_queue_mtx);
        mtx_destroy(&sc->sc_events_mtx);
        mtx_destroy(&sc->sc_done_mtx);
        sx_destroy(&sc->sc_lock);
        free(sc, M_MIRROR);
}

static void
g_mirror_providergone(struct g_provider *pp)
{
        struct g_mirror_softc *sc = pp->private;

        if ((--sc->sc_refcnt) == 0)
                g_mirror_free_device(sc);
}

static void
g_mirror_destroy_device(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;
        struct g_mirror_event *ep;
        struct g_geom *gp;
        struct g_consumer *cp, *tmpcp;

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        gp = sc->sc_geom;
        if (sc->sc_provider != NULL)
                g_mirror_destroy_provider(sc);
        for (disk = LIST_FIRST(&sc->sc_disks); disk != NULL;
            disk = LIST_FIRST(&sc->sc_disks)) {
                disk->d_flags &= ~G_MIRROR_DISK_FLAG_DIRTY;
                g_mirror_update_metadata(disk);
                g_mirror_destroy_disk(disk);
        }
        while ((ep = g_mirror_event_first(sc)) != NULL) {
                g_mirror_event_remove(sc, ep);
                if ((ep->e_flags & G_MIRROR_EVENT_DONTWAIT) != 0)
                        g_mirror_event_free(ep);
                else {
                        ep->e_error = ECANCELED;
                        ep->e_flags |= G_MIRROR_EVENT_DONE;
                        G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__, ep);
                        mtx_lock(&sc->sc_events_mtx);
                        wakeup(ep);
                        mtx_unlock(&sc->sc_events_mtx);
                }
        }
        g_mirror_timeout_drain(sc);

        g_topology_lock();
        LIST_FOREACH_SAFE(cp, &sc->sc_sync.ds_geom->consumer, consumer, tmpcp) {
                g_mirror_disconnect_consumer(sc, cp);
        }
        g_wither_geom(sc->sc_sync.ds_geom, ENXIO);
        G_MIRROR_DEBUG(0, "Device %s destroyed.", gp->name);
        g_wither_geom(gp, ENXIO);
        sx_xunlock(&sc->sc_lock);
        if ((--sc->sc_refcnt) == 0)
                g_mirror_free_device(sc);
        g_topology_unlock();
}

static void
g_mirror_orphan(struct g_consumer *cp)
{
        struct g_mirror_disk *disk;

        g_topology_assert();

        disk = cp->private;
        if (disk == NULL)
                return;
        disk->d_softc->sc_bump_id |= G_MIRROR_BUMP_SYNCID;
        g_mirror_event_send(disk, G_MIRROR_DISK_STATE_DISCONNECTED,
            G_MIRROR_EVENT_DONTWAIT);
}

/*
 * Function should return the next active disk on the list.
 * It is possible that it will be the same disk as given.
 * If there are no active disks on list, NULL is returned.
 */
static __inline struct g_mirror_disk *
g_mirror_find_next(struct g_mirror_softc *sc, struct g_mirror_disk *disk)
{
        struct g_mirror_disk *dp;

        for (dp = LIST_NEXT(disk, d_next); dp != disk;
            dp = LIST_NEXT(dp, d_next)) {
                if (dp == NULL)
                        dp = LIST_FIRST(&sc->sc_disks);
                if (dp->d_state == G_MIRROR_DISK_STATE_ACTIVE)
                        break;
        }
        if (dp->d_state != G_MIRROR_DISK_STATE_ACTIVE)
                return (NULL);
        return (dp);
}

static struct g_mirror_disk *
g_mirror_get_disk(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;

        if (sc->sc_hint == NULL) {
                sc->sc_hint = LIST_FIRST(&sc->sc_disks);
                if (sc->sc_hint == NULL)
                        return (NULL);
        }
        disk = sc->sc_hint;
        if (disk->d_state != G_MIRROR_DISK_STATE_ACTIVE) {
                disk = g_mirror_find_next(sc, disk);
                if (disk == NULL)
                        return (NULL);
        }
        sc->sc_hint = g_mirror_find_next(sc, disk);
        return (disk);
}

static int
g_mirror_write_metadata(struct g_mirror_disk *disk,
    struct g_mirror_metadata *md)
{
        struct g_mirror_softc *sc;
        struct g_consumer *cp;
        off_t offset, length;
        u_char *sector;
        int error = 0;

        g_topology_assert_not();
        sc = disk->d_softc;
        sx_assert(&sc->sc_lock, SX_LOCKED);

        cp = disk->d_consumer;
        KASSERT(cp != NULL, ("NULL consumer (%s).", sc->sc_name));
        KASSERT(cp->provider != NULL, ("NULL provider (%s).", sc->sc_name));
        KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
            ("Consumer %s closed? (r%dw%de%d).", cp->provider->name, cp->acr,
            cp->acw, cp->ace));
        length = cp->provider->sectorsize;
        offset = cp->provider->mediasize - length;
        sector = malloc((size_t)length, M_MIRROR, M_WAITOK | M_ZERO);
        if (md != NULL &&
            (sc->sc_flags & G_MIRROR_DEVICE_FLAG_WIPE) == 0) {
                /*
                 * Handle the case, when the size of parent provider reduced.
                 */
                if (offset < md->md_mediasize)
                        error = ENOSPC;
                else
                        mirror_metadata_encode(md, sector);
        }
        KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_metadata_write, error);
        if (error == 0)
                error = g_write_data(cp, offset, sector, length);
        free(sector, M_MIRROR);
        if (error != 0) {
                if ((disk->d_flags & G_MIRROR_DISK_FLAG_BROKEN) == 0) {
                        disk->d_flags |= G_MIRROR_DISK_FLAG_BROKEN;
                        G_MIRROR_DEBUG(0, "Cannot write metadata on %s "
                            "(device=%s, error=%d).",
                            g_mirror_get_diskname(disk), sc->sc_name, error);
                } else {
                        G_MIRROR_DEBUG(1, "Cannot write metadata on %s "
                            "(device=%s, error=%d).",
                            g_mirror_get_diskname(disk), sc->sc_name, error);
                }
                if (g_mirror_disconnect_on_failure &&
                    g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) > 1) {
                        sc->sc_bump_id |= G_MIRROR_BUMP_GENID;
                        g_mirror_event_send(disk,
                            G_MIRROR_DISK_STATE_DISCONNECTED,
                            G_MIRROR_EVENT_DONTWAIT);
                }
        }
        return (error);
}

static int
g_mirror_clear_metadata(struct g_mirror_disk *disk)
{
        int error;

        g_topology_assert_not();
        sx_assert(&disk->d_softc->sc_lock, SX_LOCKED);

        if (disk->d_softc->sc_type != G_MIRROR_TYPE_AUTOMATIC)
                return (0);
        error = g_mirror_write_metadata(disk, NULL);
        if (error == 0) {
                G_MIRROR_DEBUG(2, "Metadata on %s cleared.",
                    g_mirror_get_diskname(disk));
        } else {
                G_MIRROR_DEBUG(0,
                    "Cannot clear metadata on disk %s (error=%d).",
                    g_mirror_get_diskname(disk), error);
        }
        return (error);
}

void
g_mirror_fill_metadata(struct g_mirror_softc *sc, struct g_mirror_disk *disk,
    struct g_mirror_metadata *md)
{

        bzero(md, sizeof(*md));
        strlcpy(md->md_magic, G_MIRROR_MAGIC, sizeof(md->md_magic));
        md->md_version = G_MIRROR_VERSION;
        strlcpy(md->md_name, sc->sc_name, sizeof(md->md_name));
        md->md_mid = sc->sc_id;
        md->md_all = sc->sc_ndisks;
        md->md_slice = sc->sc_slice;
        md->md_balance = sc->sc_balance;
        md->md_genid = sc->sc_genid;
        md->md_mediasize = sc->sc_mediasize;
        md->md_sectorsize = sc->sc_sectorsize;
        md->md_mflags = (sc->sc_flags & G_MIRROR_DEVICE_FLAG_MASK);
        if (disk == NULL) {
                md->md_did = arc4random();
        } else {
                md->md_did = disk->d_id;
                md->md_priority = disk->d_priority;
                md->md_syncid = disk->d_sync.ds_syncid;
                md->md_dflags = (disk->d_flags & G_MIRROR_DISK_FLAG_MASK);
                if (disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING)
                        md->md_sync_offset = disk->d_sync.ds_offset_done;
                if ((disk->d_flags & G_MIRROR_DISK_FLAG_HARDCODED) != 0) {
                        strlcpy(md->md_provider,
                            disk->d_consumer->provider->name,
                            sizeof(md->md_provider));
                }
                md->md_provsize = disk->d_consumer->provider->mediasize;
        }
}

void
g_mirror_update_metadata(struct g_mirror_disk *disk)
{
        struct g_mirror_softc *sc;
        struct g_mirror_metadata md;
        int error;

        g_topology_assert_not();
        sc = disk->d_softc;
        sx_assert(&sc->sc_lock, SX_LOCKED);

        if (sc->sc_type != G_MIRROR_TYPE_AUTOMATIC)
                return;
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_WIPE) == 0)
                g_mirror_fill_metadata(sc, disk, &md);
        error = g_mirror_write_metadata(disk, &md);
        if (error == 0) {
                G_MIRROR_DEBUG(2, "Metadata on %s updated.",
                    g_mirror_get_diskname(disk));
        } else {
                G_MIRROR_DEBUG(0,
                    "Cannot update metadata on disk %s (error=%d).",
                    g_mirror_get_diskname(disk), error);
        }
}

static void
g_mirror_bump_syncid(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);
        KASSERT(g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) > 0,
            ("%s called with no active disks (device=%s).", __func__,
            sc->sc_name));

        sc->sc_syncid++;
        G_MIRROR_DEBUG(1, "Device %s: syncid bumped to %u.", sc->sc_name,
            sc->sc_syncid);
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state == G_MIRROR_DISK_STATE_ACTIVE ||
                    disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING) {
                        disk->d_sync.ds_syncid = sc->sc_syncid;
                        g_mirror_update_metadata(disk);
                }
        }
}

static void
g_mirror_bump_genid(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);
        KASSERT(g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) > 0,
            ("%s called with no active disks (device=%s).", __func__,
            sc->sc_name));

        sc->sc_genid++;
        G_MIRROR_DEBUG(1, "Device %s: genid bumped to %u.", sc->sc_name,
            sc->sc_genid);
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state == G_MIRROR_DISK_STATE_ACTIVE ||
                    disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING) {
                        disk->d_genid = sc->sc_genid;
                        g_mirror_update_metadata(disk);
                }
        }
}

static int
g_mirror_idle(struct g_mirror_softc *sc, int acw)
{
        struct g_mirror_disk *disk;
        int timeout;

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        if (sc->sc_provider == NULL)
                return (0);
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_NOFAILSYNC) != 0)
                return (0);
        if (sc->sc_idle)
                return (0);
        if (sc->sc_writes > 0)
                return (0);
        if (acw > 0 || (acw == -1 && sc->sc_provider->acw > 0)) {
                timeout = g_mirror_idletime - (time_uptime - sc->sc_last_write);
                if (!g_mirror_shutdown && timeout > 0)
                        return (timeout);
        }
        sc->sc_idle = 1;
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state != G_MIRROR_DISK_STATE_ACTIVE)
                        continue;
                G_MIRROR_DEBUG(2, "Disk %s (device %s) marked as clean.",
                    g_mirror_get_diskname(disk), sc->sc_name);
                disk->d_flags &= ~G_MIRROR_DISK_FLAG_DIRTY;
                g_mirror_update_metadata(disk);
        }
        return (0);
}

static void
g_mirror_unidle(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_NOFAILSYNC) != 0)
                return;
        sc->sc_idle = 0;
        sc->sc_last_write = time_uptime;
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state != G_MIRROR_DISK_STATE_ACTIVE)
                        continue;
                G_MIRROR_DEBUG(2, "Disk %s (device %s) marked as dirty.",
                    g_mirror_get_diskname(disk), sc->sc_name);
                disk->d_flags |= G_MIRROR_DISK_FLAG_DIRTY;
                g_mirror_update_metadata(disk);
        }
}

static void
g_mirror_done(struct bio *bp)
{
        struct g_mirror_softc *sc;

        sc = bp->bio_from->geom->softc;
        bp->bio_cflags = G_MIRROR_BIO_FLAG_REGULAR;
        mtx_lock(&sc->sc_queue_mtx);
        TAILQ_INSERT_TAIL(&sc->sc_queue, bp, bio_queue);
        mtx_unlock(&sc->sc_queue_mtx);
        wakeup(sc);
}

static void
g_mirror_regular_request_error(struct g_mirror_softc *sc,
    struct g_mirror_disk *disk, struct bio *bp)
{

        if ((bp->bio_cmd == BIO_FLUSH || bp->bio_cmd == BIO_SPEEDUP) &&
            bp->bio_error == EOPNOTSUPP)
                return;

        if ((disk->d_flags & G_MIRROR_DISK_FLAG_BROKEN) == 0) {
                disk->d_flags |= G_MIRROR_DISK_FLAG_BROKEN;
                G_MIRROR_LOGREQ(0, bp, "Request failed (error=%d).",
                    bp->bio_error);
        } else {
                G_MIRROR_LOGREQ(1, bp, "Request failed (error=%d).",
                    bp->bio_error);
        }
        if (g_mirror_disconnect_on_failure &&
            g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) > 1) {
                if (bp->bio_error == ENXIO &&
                    bp->bio_cmd == BIO_READ)
                        sc->sc_bump_id |= G_MIRROR_BUMP_SYNCID;
                else if (bp->bio_error == ENXIO)
                        sc->sc_bump_id |= G_MIRROR_BUMP_SYNCID_NOW;
                else
                        sc->sc_bump_id |= G_MIRROR_BUMP_GENID;
                g_mirror_event_send(disk, G_MIRROR_DISK_STATE_DISCONNECTED,
                    G_MIRROR_EVENT_DONTWAIT);
        }
}

static void
g_mirror_regular_request(struct g_mirror_softc *sc, struct bio *bp)
{
        struct g_mirror_disk *disk;
        struct bio *pbp;

        g_topology_assert_not();
        KASSERT(sc->sc_provider == bp->bio_parent->bio_to,
            ("regular request %p with unexpected origin", bp));

        pbp = bp->bio_parent;
        bp->bio_from->index--;
        if (bp->bio_cmd == BIO_WRITE || bp->bio_cmd == BIO_DELETE)
                sc->sc_writes--;
        disk = bp->bio_from->private;
        if (disk == NULL) {
                g_topology_lock();
                g_mirror_kill_consumer(sc, bp->bio_from);
                g_topology_unlock();
        }

        switch (bp->bio_cmd) {
        case BIO_READ:
                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_regular_request_read,
                    bp->bio_error);
                break;
        case BIO_WRITE:
                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_regular_request_write,
                    bp->bio_error);
                break;
        case BIO_DELETE:
                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_regular_request_delete,
                    bp->bio_error);
                break;
        case BIO_FLUSH:
                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_regular_request_flush,
                    bp->bio_error);
                break;
        case BIO_SPEEDUP:
                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_regular_request_speedup,
                    bp->bio_error);
                break;
        }

        pbp->bio_inbed++;
        KASSERT(pbp->bio_inbed <= pbp->bio_children,
            ("bio_inbed (%u) is bigger than bio_children (%u).", pbp->bio_inbed,
            pbp->bio_children));
        if (bp->bio_error == 0 && pbp->bio_error == 0) {
                G_MIRROR_LOGREQ(3, bp, "Request delivered.");
                g_destroy_bio(bp);
                if (pbp->bio_children == pbp->bio_inbed) {
                        G_MIRROR_LOGREQ(3, pbp, "Request delivered.");
                        pbp->bio_completed = pbp->bio_length;
                        if (pbp->bio_cmd == BIO_WRITE ||
                            pbp->bio_cmd == BIO_DELETE) {
                                TAILQ_REMOVE(&sc->sc_inflight, pbp, bio_queue);
                                /* Release delayed sync requests if possible. */
                                g_mirror_sync_release(sc);
                        }
                        g_io_deliver(pbp, pbp->bio_error);
                }
                return;
        } else if (bp->bio_error != 0) {
                if (pbp->bio_error == 0)
                        pbp->bio_error = bp->bio_error;
                if (disk != NULL)
                        g_mirror_regular_request_error(sc, disk, bp);
                switch (pbp->bio_cmd) {
                case BIO_DELETE:
                case BIO_WRITE:
                case BIO_FLUSH:
                case BIO_SPEEDUP:
                        pbp->bio_inbed--;
                        pbp->bio_children--;
                        break;
                }
        }
        g_destroy_bio(bp);

        switch (pbp->bio_cmd) {
        case BIO_READ:
                if (pbp->bio_inbed < pbp->bio_children)
                        break;

                /*
                 * If there is only one active disk we want to double-check that
                 * it is, in fact, the disk that we already tried.  This is
                 * necessary because we might have just lost a race with a
                 * removal of the tried disk (likely because of the same error)
                 * and the only remaining disk is still viable for a retry.
                 */
                if (g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) == 1 &&
                    disk != NULL &&
                    disk->d_state == G_MIRROR_DISK_STATE_ACTIVE) {
                        g_io_deliver(pbp, pbp->bio_error);
                } else {
                        pbp->bio_error = 0;
                        mtx_lock(&sc->sc_queue_mtx);
                        TAILQ_INSERT_TAIL(&sc->sc_queue, pbp, bio_queue);
                        mtx_unlock(&sc->sc_queue_mtx);
                        G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__, sc);
                        wakeup(sc);
                }
                break;
        case BIO_DELETE:
        case BIO_WRITE:
        case BIO_FLUSH:
        case BIO_SPEEDUP:
                if (pbp->bio_children == 0) {
                        /*
                         * All requests failed.
                         */
                } else if (pbp->bio_inbed < pbp->bio_children) {
                        /* Do nothing. */
                        break;
                } else if (pbp->bio_children == pbp->bio_inbed) {
                        /* Some requests succeeded. */
                        pbp->bio_error = 0;
                        pbp->bio_completed = pbp->bio_length;
                }
                if (pbp->bio_cmd == BIO_WRITE || pbp->bio_cmd == BIO_DELETE) {
                        TAILQ_REMOVE(&sc->sc_inflight, pbp, bio_queue);
                        /* Release delayed sync requests if possible. */
                        g_mirror_sync_release(sc);
                }
                g_io_deliver(pbp, pbp->bio_error);
                break;
        default:
                KASSERT(1 == 0, ("Invalid request: %u.", pbp->bio_cmd));
                break;
        }
}

static void
g_mirror_sync_done(struct bio *bp)
{
        struct g_mirror_softc *sc;

        G_MIRROR_LOGREQ(3, bp, "Synchronization request delivered.");
        sc = bp->bio_from->geom->softc;
        bp->bio_cflags = G_MIRROR_BIO_FLAG_SYNC;
        mtx_lock(&sc->sc_queue_mtx);
        TAILQ_INSERT_TAIL(&sc->sc_queue, bp, bio_queue);
        mtx_unlock(&sc->sc_queue_mtx);
        wakeup(sc);
}

static void
g_mirror_candelete(struct bio *bp)
{
        struct g_mirror_softc *sc;
        struct g_mirror_disk *disk;
        int val;

        sc = bp->bio_to->private;
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_flags & G_MIRROR_DISK_FLAG_CANDELETE)
                        break;
        }
        val = disk != NULL;
        g_handleattr(bp, "GEOM::candelete", &val, sizeof(val));
}

static void
g_mirror_kernel_dump(struct bio *bp)
{
        struct g_mirror_softc *sc;
        struct g_mirror_disk *disk;
        struct bio *cbp;
        struct g_kerneldump *gkd;

        /*
         * We configure dumping to the first component, because this component
         * will be used for reading with 'prefer' balance algorithm.
         * If the component with the highest priority is currently disconnected
         * we will not be able to read the dump after the reboot if it will be
         * connected and synchronized later. Can we do something better?
         */
        sc = bp->bio_to->private;
        disk = LIST_FIRST(&sc->sc_disks);

        gkd = (struct g_kerneldump *)bp->bio_data;
        if (gkd->length > bp->bio_to->mediasize)
                gkd->length = bp->bio_to->mediasize;
        cbp = g_clone_bio(bp);
        if (cbp == NULL) {
                g_io_deliver(bp, ENOMEM);
                return;
        }
        cbp->bio_done = g_std_done;
        g_io_request(cbp, disk->d_consumer);
        G_MIRROR_DEBUG(1, "Kernel dump will go to %s.",
            g_mirror_get_diskname(disk));
}

static void
g_mirror_rotation_rate(struct bio *bp)
{
        struct g_mirror_softc *sc;
        struct g_mirror_disk *disk;
        bool first = true;
        uint16_t rr = DISK_RR_UNKNOWN;

        sc = bp->bio_to->private;
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (first)
                        rr = disk->d_rotation_rate;
                else if (rr != disk->d_rotation_rate) {
                        rr = DISK_RR_UNKNOWN;
                        break;
                }
                first = false;
        }
        g_handleattr(bp, "GEOM::rotation_rate", &rr, sizeof(rr));
}

static void
g_mirror_start(struct bio *bp)
{
        struct g_mirror_softc *sc;

        sc = bp->bio_to->private;
        /*
         * If sc == NULL or there are no valid disks, provider's error
         * should be set and g_mirror_start() should not be called at all.
         */
        KASSERT(sc != NULL && sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING,
            ("Provider's error should be set (error=%d)(mirror=%s).",
            bp->bio_to->error, bp->bio_to->name));
        G_MIRROR_LOGREQ(3, bp, "Request received.");

        switch (bp->bio_cmd) {
        case BIO_READ:
        case BIO_WRITE:
        case BIO_DELETE:
        case BIO_SPEEDUP:
        case BIO_FLUSH:
                break;
        case BIO_GETATTR:
                if (!strcmp(bp->bio_attribute, "GEOM::candelete")) {
                        g_mirror_candelete(bp);
                        return;
                } else if (strcmp("GEOM::kerneldump", bp->bio_attribute) == 0) {
                        g_mirror_kernel_dump(bp);
                        return;
                } else if (!strcmp(bp->bio_attribute, "GEOM::rotation_rate")) {
                        g_mirror_rotation_rate(bp);
                        return;
                }
                /* FALLTHROUGH */
        default:
                g_io_deliver(bp, EOPNOTSUPP);
                return;
        }
        mtx_lock(&sc->sc_queue_mtx);
        if (bp->bio_to->error != 0) {
                mtx_unlock(&sc->sc_queue_mtx);
                g_io_deliver(bp, bp->bio_to->error);
                return;
        }
        TAILQ_INSERT_TAIL(&sc->sc_queue, bp, bio_queue);
        mtx_unlock(&sc->sc_queue_mtx);
        G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__, sc);
        wakeup(sc);
}

/*
 * Return true if the given request is colliding with a in-progress
 * synchronization request.
 */
static bool
g_mirror_sync_collision(struct g_mirror_softc *sc, struct bio *bp)
{
        struct g_mirror_disk *disk;
        struct bio *sbp;
        off_t rstart, rend, sstart, send;
        u_int i;

        if (sc->sc_sync.ds_ndisks == 0)
                return (false);
        rstart = bp->bio_offset;
        rend = bp->bio_offset + bp->bio_length;
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state != G_MIRROR_DISK_STATE_SYNCHRONIZING)
                        continue;
                for (i = 0; i < g_mirror_syncreqs; i++) {
                        sbp = disk->d_sync.ds_bios[i];
                        if (sbp == NULL)
                                continue;
                        sstart = sbp->bio_offset;
                        send = sbp->bio_offset + sbp->bio_length;
                        if (rend > sstart && rstart < send)
                                return (true);
                }
        }
        return (false);
}

/*
 * Return true if the given sync request is colliding with a in-progress regular
 * request.
 */
static bool
g_mirror_regular_collision(struct g_mirror_softc *sc, struct bio *sbp)
{
        off_t rstart, rend, sstart, send;
        struct bio *bp;

        if (sc->sc_sync.ds_ndisks == 0)
                return (false);
        sstart = sbp->bio_offset;
        send = sbp->bio_offset + sbp->bio_length;
        TAILQ_FOREACH(bp, &sc->sc_inflight, bio_queue) {
                rstart = bp->bio_offset;
                rend = bp->bio_offset + bp->bio_length;
                if (rend > sstart && rstart < send)
                        return (true);
        }
        return (false);
}

/*
 * Puts regular request onto delayed queue.
 */
static void
g_mirror_regular_delay(struct g_mirror_softc *sc, struct bio *bp)
{

        G_MIRROR_LOGREQ(2, bp, "Delaying request.");
        TAILQ_INSERT_TAIL(&sc->sc_regular_delayed, bp, bio_queue);
}

/*
 * Puts synchronization request onto delayed queue.
 */
static void
g_mirror_sync_delay(struct g_mirror_softc *sc, struct bio *bp)
{

        G_MIRROR_LOGREQ(2, bp, "Delaying synchronization request.");
        TAILQ_INSERT_TAIL(&sc->sc_sync_delayed, bp, bio_queue);
}

/*
 * Requeue delayed regular requests.
 */
static void
g_mirror_regular_release(struct g_mirror_softc *sc)
{
        struct bio *bp;

        if ((bp = TAILQ_FIRST(&sc->sc_regular_delayed)) == NULL)
                return;
        if (g_mirror_sync_collision(sc, bp))
                return;

        G_MIRROR_DEBUG(2, "Requeuing regular requests after collision.");
        mtx_lock(&sc->sc_queue_mtx);
        TAILQ_CONCAT(&sc->sc_regular_delayed, &sc->sc_queue, bio_queue);
        TAILQ_SWAP(&sc->sc_regular_delayed, &sc->sc_queue, bio, bio_queue);
        mtx_unlock(&sc->sc_queue_mtx);
}

/*
 * Releases delayed sync requests which don't collide anymore with regular
 * requests.
 */
static void
g_mirror_sync_release(struct g_mirror_softc *sc)
{
        struct bio *bp, *bp2;

        TAILQ_FOREACH_SAFE(bp, &sc->sc_sync_delayed, bio_queue, bp2) {
                if (g_mirror_regular_collision(sc, bp))
                        continue;
                TAILQ_REMOVE(&sc->sc_sync_delayed, bp, bio_queue);
                G_MIRROR_LOGREQ(2, bp,
                    "Releasing delayed synchronization request.");
                g_io_request(bp, bp->bio_from);
        }
}

/*
 * Free a synchronization request and clear its slot in the array.
 */
static void
g_mirror_sync_request_free(struct g_mirror_disk *disk, struct bio *bp)
{
        int idx;

        if (disk != NULL && disk->d_sync.ds_bios != NULL) {
                idx = (int)(uintptr_t)bp->bio_caller1;
                KASSERT(disk->d_sync.ds_bios[idx] == bp,
                    ("unexpected sync BIO at %p:%d", disk, idx));
                disk->d_sync.ds_bios[idx] = NULL;
        }
        free(bp->bio_data, M_MIRROR);
        g_destroy_bio(bp);
}

/*
 * Handle synchronization requests.
 * Every synchronization request is a two-step process: first, a read request is
 * sent to the mirror provider via the sync consumer. If that request completes
 * successfully, it is converted to a write and sent to the disk being
 * synchronized. If the write also completes successfully, the synchronization
 * offset is advanced and a new read request is submitted.
 */
static void
g_mirror_sync_request(struct g_mirror_softc *sc, struct bio *bp)
{
        struct g_mirror_disk *disk;
        struct g_mirror_disk_sync *sync;

        KASSERT((bp->bio_cmd == BIO_READ &&
            bp->bio_from->geom == sc->sc_sync.ds_geom) ||
            (bp->bio_cmd == BIO_WRITE && bp->bio_from->geom == sc->sc_geom),
            ("Sync BIO %p with unexpected origin", bp));

        bp->bio_from->index--;
        disk = bp->bio_from->private;
        if (disk == NULL) {
                sx_xunlock(&sc->sc_lock); /* Avoid recursion on sc_lock. */
                g_topology_lock();
                g_mirror_kill_consumer(sc, bp->bio_from);
                g_topology_unlock();
                g_mirror_sync_request_free(NULL, bp);
                sx_xlock(&sc->sc_lock);
                return;
        }

        sync = &disk->d_sync;

        /*
         * Synchronization request.
         */
        switch (bp->bio_cmd) {
        case BIO_READ: {
                struct g_consumer *cp;

                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_sync_request_read,
                    bp->bio_error);

                if (bp->bio_error != 0) {
                        G_MIRROR_LOGREQ(0, bp,
                            "Synchronization request failed (error=%d).",
                            bp->bio_error);

                        /*
                         * The read error will trigger a syncid bump, so there's
                         * no need to do that here.
                         *
                         * The read error handling for regular requests will
                         * retry the read from all active mirrors before passing
                         * the error back up, so there's no need to retry here.
                         */
                        g_mirror_sync_request_free(disk, bp);
                        g_mirror_event_send(disk,
                            G_MIRROR_DISK_STATE_DISCONNECTED,
                            G_MIRROR_EVENT_DONTWAIT);
                        return;
                }
                G_MIRROR_LOGREQ(3, bp,
                    "Synchronization request half-finished.");
                bp->bio_cmd = BIO_WRITE;
                bp->bio_cflags = 0;
                cp = disk->d_consumer;
                KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
                    ("Consumer %s not opened (r%dw%de%d).", cp->provider->name,
                    cp->acr, cp->acw, cp->ace));
                cp->index++;
                g_io_request(bp, cp);
                return;
        }
        case BIO_WRITE: {
                off_t offset;
                int i;

                KFAIL_POINT_ERROR(DEBUG_FP, g_mirror_sync_request_write,
                    bp->bio_error);

                if (bp->bio_error != 0) {
                        G_MIRROR_LOGREQ(0, bp,
                            "Synchronization request failed (error=%d).",
                            bp->bio_error);
                        g_mirror_sync_request_free(disk, bp);
                        sc->sc_bump_id |= G_MIRROR_BUMP_GENID;
                        g_mirror_event_send(disk,
                            G_MIRROR_DISK_STATE_DISCONNECTED,
                            G_MIRROR_EVENT_DONTWAIT);
                        return;
                }
                G_MIRROR_LOGREQ(3, bp, "Synchronization request finished.");
                if (sync->ds_offset >= sc->sc_mediasize ||
                    sync->ds_consumer == NULL ||
                    (sc->sc_flags & G_MIRROR_DEVICE_FLAG_DESTROY) != 0) {
                        /* Don't send more synchronization requests. */
                        sync->ds_inflight--;
                        g_mirror_sync_request_free(disk, bp);
                        if (sync->ds_inflight > 0)
                                return;
                        if (sync->ds_consumer == NULL ||
                            (sc->sc_flags & G_MIRROR_DEVICE_FLAG_DESTROY) != 0) {
                                return;
                        }
                        /* Disk up-to-date, activate it. */
                        g_mirror_event_send(disk, G_MIRROR_DISK_STATE_ACTIVE,
                            G_MIRROR_EVENT_DONTWAIT);
                        return;
                }

                /* Send next synchronization request. */
                g_mirror_sync_reinit(disk, bp, sync->ds_offset);
                sync->ds_offset += bp->bio_length;

                G_MIRROR_LOGREQ(3, bp, "Sending synchronization request.");
                sync->ds_consumer->index++;

                /*
                 * Delay the request if it is colliding with a regular request.
                 */
                if (g_mirror_regular_collision(sc, bp))
                        g_mirror_sync_delay(sc, bp);
                else
                        g_io_request(bp, sync->ds_consumer);

                /* Requeue delayed requests if possible. */
                g_mirror_regular_release(sc);

                /* Find the smallest offset */
                offset = sc->sc_mediasize;
                for (i = 0; i < g_mirror_syncreqs; i++) {
                        bp = sync->ds_bios[i];
                        if (bp != NULL && bp->bio_offset < offset)
                                offset = bp->bio_offset;
                }
                if (g_mirror_sync_period > 0 &&
                    time_uptime - sync->ds_update_ts > g_mirror_sync_period) {
                        sync->ds_offset_done = offset;
                        g_mirror_update_metadata(disk);
                        sync->ds_update_ts = time_uptime;
                }
                return;
        }
        default:
                panic("Invalid I/O request %p", bp);
        }
}

static void
g_mirror_request_prefer(struct g_mirror_softc *sc, struct bio *bp)
{
        struct g_mirror_disk *disk;
        struct g_consumer *cp;
        struct bio *cbp;

        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state == G_MIRROR_DISK_STATE_ACTIVE)
                        break;
        }
        if (disk == NULL) {
                if (bp->bio_error == 0)
                        bp->bio_error = ENXIO;
                g_io_deliver(bp, bp->bio_error);
                return;
        }
        cbp = g_clone_bio(bp);
        if (cbp == NULL) {
                if (bp->bio_error == 0)
                        bp->bio_error = ENOMEM;
                g_io_deliver(bp, bp->bio_error);
                return;
        }
        /*
         * Fill in the component buf structure.
         */
        cp = disk->d_consumer;
        cbp->bio_done = g_mirror_done;
        cbp->bio_to = cp->provider;
        G_MIRROR_LOGREQ(3, cbp, "Sending request.");
        KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
            ("Consumer %s not opened (r%dw%de%d).", cp->provider->name, cp->acr,
            cp->acw, cp->ace));
        cp->index++;
        g_io_request(cbp, cp);
}

static void
g_mirror_request_round_robin(struct g_mirror_softc *sc, struct bio *bp)
{
        struct g_mirror_disk *disk;
        struct g_consumer *cp;
        struct bio *cbp;

        disk = g_mirror_get_disk(sc);
        if (disk == NULL) {
                if (bp->bio_error == 0)
                        bp->bio_error = ENXIO;
                g_io_deliver(bp, bp->bio_error);
                return;
        }
        cbp = g_clone_bio(bp);
        if (cbp == NULL) {
                if (bp->bio_error == 0)
                        bp->bio_error = ENOMEM;
                g_io_deliver(bp, bp->bio_error);
                return;
        }
        /*
         * Fill in the component buf structure.
         */
        cp = disk->d_consumer;
        cbp->bio_done = g_mirror_done;
        cbp->bio_to = cp->provider;
        G_MIRROR_LOGREQ(3, cbp, "Sending request.");
        KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
            ("Consumer %s not opened (r%dw%de%d).", cp->provider->name, cp->acr,
            cp->acw, cp->ace));
        cp->index++;
        g_io_request(cbp, cp);
}

#define TRACK_SIZE  (1 * 1024 * 1024)
#define LOAD_SCALE      256
#define ABS(x)          (((x) >= 0) ? (x) : (-(x)))

static void
g_mirror_request_load(struct g_mirror_softc *sc, struct bio *bp)
{
        struct g_mirror_disk *disk, *dp;
        struct g_consumer *cp;
        struct bio *cbp;
        int prio, best;

        /* Find a disk with the smallest load. */
        disk = NULL;
        best = INT_MAX;
        LIST_FOREACH(dp, &sc->sc_disks, d_next) {
                if (dp->d_state != G_MIRROR_DISK_STATE_ACTIVE)
                        continue;
                prio = dp->load;
                /* If disk head is precisely in position - highly prefer it. */
                if (dp->d_last_offset == bp->bio_offset)
                        prio -= 2 * LOAD_SCALE;
                else
                /* If disk head is close to position - prefer it. */
                if (ABS(dp->d_last_offset - bp->bio_offset) < TRACK_SIZE)
                        prio -= 1 * LOAD_SCALE;
                if (prio <= best) {
                        disk = dp;
                        best = prio;
                }
        }
        KASSERT(disk != NULL, ("NULL disk for %s.", sc->sc_name));
        cbp = g_clone_bio(bp);
        if (cbp == NULL) {
                if (bp->bio_error == 0)
                        bp->bio_error = ENOMEM;
                g_io_deliver(bp, bp->bio_error);
                return;
        }
        /*
         * Fill in the component buf structure.
         */
        cp = disk->d_consumer;
        cbp->bio_done = g_mirror_done;
        cbp->bio_to = cp->provider;
        G_MIRROR_LOGREQ(3, cbp, "Sending request.");
        KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
            ("Consumer %s not opened (r%dw%de%d).", cp->provider->name, cp->acr,
            cp->acw, cp->ace));
        cp->index++;
        /* Remember last head position */
        disk->d_last_offset = bp->bio_offset + bp->bio_length;
        /* Update loads. */
        LIST_FOREACH(dp, &sc->sc_disks, d_next) {
                dp->load = (dp->d_consumer->index * LOAD_SCALE +
                    dp->load * 7) / 8;
        }
        g_io_request(cbp, cp);
}

static void
g_mirror_request_split(struct g_mirror_softc *sc, struct bio *bp)
{
        struct bio_queue queue;
        struct g_mirror_disk *disk;
        struct g_consumer *cp __diagused;
        struct bio *cbp;
        off_t left, mod, offset, slice;
        u_char *data;
        u_int ndisks;

        if (bp->bio_length <= sc->sc_slice) {
                g_mirror_request_round_robin(sc, bp);
                return;
        }
        ndisks = g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE);
        slice = bp->bio_length / ndisks;
        mod = slice % sc->sc_provider->sectorsize;
        if (mod != 0)
                slice += sc->sc_provider->sectorsize - mod;
        /*
         * Allocate all bios before sending any request, so we can
         * return ENOMEM in nice and clean way.
         */
        left = bp->bio_length;
        offset = bp->bio_offset;
        data = bp->bio_data;
        TAILQ_INIT(&queue);
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state != G_MIRROR_DISK_STATE_ACTIVE)
                        continue;
                cbp = g_clone_bio(bp);
                if (cbp == NULL) {
                        while ((cbp = TAILQ_FIRST(&queue)) != NULL) {
                                TAILQ_REMOVE(&queue, cbp, bio_queue);
                                g_destroy_bio(cbp);
                        }
                        if (bp->bio_error == 0)
                                bp->bio_error = ENOMEM;
                        g_io_deliver(bp, bp->bio_error);
                        return;
                }
                TAILQ_INSERT_TAIL(&queue, cbp, bio_queue);
                cbp->bio_done = g_mirror_done;
                cbp->bio_caller1 = disk;
                cbp->bio_to = disk->d_consumer->provider;
                cbp->bio_offset = offset;
                cbp->bio_data = data;
                cbp->bio_length = MIN(left, slice);
                left -= cbp->bio_length;
                if (left == 0)
                        break;
                offset += cbp->bio_length;
                data += cbp->bio_length;
        }
        while ((cbp = TAILQ_FIRST(&queue)) != NULL) {
                TAILQ_REMOVE(&queue, cbp, bio_queue);
                G_MIRROR_LOGREQ(3, cbp, "Sending request.");
                disk = cbp->bio_caller1;
                cbp->bio_caller1 = NULL;
                cp = disk->d_consumer;
                KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
                    ("Consumer %s not opened (r%dw%de%d).", cp->provider->name,
                    cp->acr, cp->acw, cp->ace));
                disk->d_consumer->index++;
                g_io_request(cbp, disk->d_consumer);
        }
}

static void
g_mirror_register_request(struct g_mirror_softc *sc, struct bio *bp)
{
        struct bio_queue queue;
        struct bio *cbp;
        struct g_consumer *cp;
        struct g_mirror_disk *disk;

        sx_assert(&sc->sc_lock, SA_XLOCKED);

        /*
         * To avoid ordering issues, if a write is deferred because of a
         * collision with a sync request, all I/O is deferred until that
         * write is initiated.
         */
        if (bp->bio_from->geom != sc->sc_sync.ds_geom &&
            !TAILQ_EMPTY(&sc->sc_regular_delayed)) {
                g_mirror_regular_delay(sc, bp);
                return;
        }

        switch (bp->bio_cmd) {
        case BIO_READ:
                switch (sc->sc_balance) {
                case G_MIRROR_BALANCE_LOAD:
                        g_mirror_request_load(sc, bp);
                        break;
                case G_MIRROR_BALANCE_PREFER:
                        g_mirror_request_prefer(sc, bp);
                        break;
                case G_MIRROR_BALANCE_ROUND_ROBIN:
                        g_mirror_request_round_robin(sc, bp);
                        break;
                case G_MIRROR_BALANCE_SPLIT:
                        g_mirror_request_split(sc, bp);
                        break;
                }
                return;
        case BIO_WRITE:
        case BIO_DELETE:
                /*
                 * Delay the request if it is colliding with a synchronization
                 * request.
                 */
                if (g_mirror_sync_collision(sc, bp)) {
                        g_mirror_regular_delay(sc, bp);
                        return;
                }

                if (sc->sc_idle)
                        g_mirror_unidle(sc);
                else
                        sc->sc_last_write = time_uptime;

                /*
                 * Bump syncid on first write.
                 */
                if ((sc->sc_bump_id & G_MIRROR_BUMP_SYNCID) != 0) {
                        sc->sc_bump_id &= ~G_MIRROR_BUMP_SYNCID;
                        g_mirror_bump_syncid(sc);
                }

                /*
                 * Allocate all bios before sending any request, so we can
                 * return ENOMEM in nice and clean way.
                 */
                TAILQ_INIT(&queue);
                LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                        switch (disk->d_state) {
                        case G_MIRROR_DISK_STATE_ACTIVE:
                                break;
                        case G_MIRROR_DISK_STATE_SYNCHRONIZING:
                                if (bp->bio_offset >= disk->d_sync.ds_offset)
                                        continue;
                                break;
                        default:
                                continue;
                        }
                        if (bp->bio_cmd == BIO_DELETE &&
                            (disk->d_flags & G_MIRROR_DISK_FLAG_CANDELETE) == 0)
                                continue;
                        cbp = g_clone_bio(bp);
                        if (cbp == NULL) {
                                while ((cbp = TAILQ_FIRST(&queue)) != NULL) {
                                        TAILQ_REMOVE(&queue, cbp, bio_queue);
                                        g_destroy_bio(cbp);
                                }
                                if (bp->bio_error == 0)
                                        bp->bio_error = ENOMEM;
                                g_io_deliver(bp, bp->bio_error);
                                return;
                        }
                        TAILQ_INSERT_TAIL(&queue, cbp, bio_queue);
                        cbp->bio_done = g_mirror_done;
                        cp = disk->d_consumer;
                        cbp->bio_caller1 = cp;
                        cbp->bio_to = cp->provider;
                        KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
                            ("Consumer %s not opened (r%dw%de%d).",
                            cp->provider->name, cp->acr, cp->acw, cp->ace));
                }
                if (TAILQ_EMPTY(&queue)) {
                        KASSERT(bp->bio_cmd == BIO_DELETE,
                            ("No consumers for regular request %p", bp));
                        g_io_deliver(bp, EOPNOTSUPP);
                        return;
                }
                while ((cbp = TAILQ_FIRST(&queue)) != NULL) {
                        G_MIRROR_LOGREQ(3, cbp, "Sending request.");
                        TAILQ_REMOVE(&queue, cbp, bio_queue);
                        cp = cbp->bio_caller1;
                        cbp->bio_caller1 = NULL;
                        cp->index++;
                        sc->sc_writes++;
                        g_io_request(cbp, cp);
                }
                /*
                 * Put request onto inflight queue, so we can check if new
                 * synchronization requests don't collide with it.
                 */
                TAILQ_INSERT_TAIL(&sc->sc_inflight, bp, bio_queue);
                return;
        case BIO_SPEEDUP:
        case BIO_FLUSH:
                TAILQ_INIT(&queue);
                LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                        if (disk->d_state != G_MIRROR_DISK_STATE_ACTIVE)
                                continue;
                        cbp = g_clone_bio(bp);
                        if (cbp == NULL) {
                                while ((cbp = TAILQ_FIRST(&queue)) != NULL) {
                                        TAILQ_REMOVE(&queue, cbp, bio_queue);
                                        g_destroy_bio(cbp);
                                }
                                if (bp->bio_error == 0)
                                        bp->bio_error = ENOMEM;
                                g_io_deliver(bp, bp->bio_error);
                                return;
                        }
                        TAILQ_INSERT_TAIL(&queue, cbp, bio_queue);
                        cbp->bio_done = g_mirror_done;
                        cbp->bio_caller1 = disk;
                        cbp->bio_to = disk->d_consumer->provider;
                }
                KASSERT(!TAILQ_EMPTY(&queue),
                    ("No consumers for regular request %p", bp));
                while ((cbp = TAILQ_FIRST(&queue)) != NULL) {
                        G_MIRROR_LOGREQ(3, cbp, "Sending request.");
                        TAILQ_REMOVE(&queue, cbp, bio_queue);
                        disk = cbp->bio_caller1;
                        cbp->bio_caller1 = NULL;
                        cp = disk->d_consumer;
                        KASSERT(cp->acr >= 1 && cp->acw >= 1 && cp->ace >= 1,
                            ("Consumer %s not opened (r%dw%de%d).", cp->provider->name,
                            cp->acr, cp->acw, cp->ace));
                        cp->index++;
                        g_io_request(cbp, cp);
                }
                break;
        default:
                KASSERT(1 == 0, ("Invalid command here: %u (device=%s)",
                    bp->bio_cmd, sc->sc_name));
                break;
        }
}

static int
g_mirror_can_destroy(struct g_mirror_softc *sc)
{
        struct g_geom *gp;
        struct g_consumer *cp;

        g_topology_assert();
        gp = sc->sc_geom;
        if (gp->softc == NULL)
                return (1);
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_TASTING) != 0)
                return (0);
        LIST_FOREACH(cp, &gp->consumer, consumer) {
                if (g_mirror_is_busy(sc, cp))
                        return (0);
        }
        gp = sc->sc_sync.ds_geom;
        LIST_FOREACH(cp, &gp->consumer, consumer) {
                if (g_mirror_is_busy(sc, cp))
                        return (0);
        }
        G_MIRROR_DEBUG(2, "No I/O requests for %s, it can be destroyed.",
            sc->sc_name);
        return (1);
}

static int
g_mirror_try_destroy(struct g_mirror_softc *sc)
{

        if (sc->sc_rootmount != NULL) {
                G_MIRROR_DEBUG(1, "root_mount_rel[%u] %p", __LINE__,
                    sc->sc_rootmount);
                root_mount_rel(sc->sc_rootmount);
                sc->sc_rootmount = NULL;
        }
        g_topology_lock();
        if (!g_mirror_can_destroy(sc)) {
                g_topology_unlock();
                return (0);
        }
        sc->sc_geom->softc = NULL;
        sc->sc_sync.ds_geom->softc = NULL;
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_DRAIN) != 0) {
                g_topology_unlock();
                G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__,
                    &sc->sc_worker);
                /* Unlock sc_lock here, as it can be destroyed after wakeup. */
                sx_xunlock(&sc->sc_lock);
                wakeup(&sc->sc_worker);
                sc->sc_worker = NULL;
        } else {
                g_topology_unlock();
                g_mirror_destroy_device(sc);
        }
        return (1);
}

/*
 * Worker thread.
 */
static void
g_mirror_worker(void *arg)
{
        struct g_mirror_softc *sc;
        struct g_mirror_event *ep;
        struct bio *bp;
        int timeout;

        sc = arg;
        thread_lock(curthread);
        sched_prio(curthread, PRIBIO);
        thread_unlock(curthread);

        sx_xlock(&sc->sc_lock);
        for (;;) {
                G_MIRROR_DEBUG(5, "%s: Let's see...", __func__);
                /*
                 * First take a look at events.
                 * This is important to handle events before any I/O requests.
                 */
                ep = g_mirror_event_first(sc);
                if (ep != NULL) {
                        g_mirror_event_remove(sc, ep);
                        if ((ep->e_flags & G_MIRROR_EVENT_DEVICE) != 0) {
                                /* Update only device status. */
                                G_MIRROR_DEBUG(3,
                                    "Running event for device %s.",
                                    sc->sc_name);
                                ep->e_error = 0;
                                g_mirror_update_device(sc, true);
                        } else {
                                /* Update disk status. */
                                G_MIRROR_DEBUG(3, "Running event for disk %s.",
                                     g_mirror_get_diskname(ep->e_disk));
                                ep->e_error = g_mirror_update_disk(ep->e_disk,
                                    ep->e_state);
                                if (ep->e_error == 0)
                                        g_mirror_update_device(sc, false);
                        }
                        if ((ep->e_flags & G_MIRROR_EVENT_DONTWAIT) != 0) {
                                KASSERT(ep->e_error == 0,
                                    ("Error cannot be handled."));
                                g_mirror_event_free(ep);
                        } else {
                                ep->e_flags |= G_MIRROR_EVENT_DONE;
                                G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__,
                                    ep);
                                mtx_lock(&sc->sc_events_mtx);
                                wakeup(ep);
                                mtx_unlock(&sc->sc_events_mtx);
                        }
                        if ((sc->sc_flags &
                            G_MIRROR_DEVICE_FLAG_DESTROY) != 0) {
                                if (g_mirror_try_destroy(sc)) {
                                        curthread->td_pflags &= ~TDP_GEOM;
                                        G_MIRROR_DEBUG(1, "Thread exiting.");
                                        kproc_exit(0);
                                }
                        }
                        G_MIRROR_DEBUG(5, "%s: I'm here 1.", __func__);
                        continue;
                }

                /*
                 * Check if we can mark array as CLEAN and if we can't take
                 * how much seconds should we wait.
                 */
                timeout = g_mirror_idle(sc, -1);

                /*
                 * Handle I/O requests.
                 */
                mtx_lock(&sc->sc_queue_mtx);
                bp = TAILQ_FIRST(&sc->sc_queue);
                if (bp != NULL)
                        TAILQ_REMOVE(&sc->sc_queue, bp, bio_queue);
                else {
                        if ((sc->sc_flags &
                            G_MIRROR_DEVICE_FLAG_DESTROY) != 0) {
                                mtx_unlock(&sc->sc_queue_mtx);
                                if (g_mirror_try_destroy(sc)) {
                                        curthread->td_pflags &= ~TDP_GEOM;
                                        G_MIRROR_DEBUG(1, "Thread exiting.");
                                        kproc_exit(0);
                                }
                                mtx_lock(&sc->sc_queue_mtx);
                                if (!TAILQ_EMPTY(&sc->sc_queue)) {
                                        mtx_unlock(&sc->sc_queue_mtx);
                                        continue;
                                }
                        }
                        if (g_mirror_event_first(sc) != NULL) {
                                mtx_unlock(&sc->sc_queue_mtx);
                                continue;
                        }
                        sx_xunlock(&sc->sc_lock);
                        MSLEEP(sc, &sc->sc_queue_mtx, PRIBIO | PDROP, "m:w1",
                            timeout * hz);
                        sx_xlock(&sc->sc_lock);
                        G_MIRROR_DEBUG(5, "%s: I'm here 4.", __func__);
                        continue;
                }
                mtx_unlock(&sc->sc_queue_mtx);

                if (bp->bio_from->geom == sc->sc_sync.ds_geom &&
                    (bp->bio_cflags & G_MIRROR_BIO_FLAG_SYNC) != 0) {
                        /*
                         * Handle completion of the first half (the read) of a
                         * block synchronization operation.
                         */
                        g_mirror_sync_request(sc, bp);
                } else if (bp->bio_to != sc->sc_provider) {
                        if ((bp->bio_cflags & G_MIRROR_BIO_FLAG_REGULAR) != 0)
                                /*
                                 * Handle completion of a regular I/O request.
                                 */
                                g_mirror_regular_request(sc, bp);
                        else if ((bp->bio_cflags & G_MIRROR_BIO_FLAG_SYNC) != 0)
                                /*
                                 * Handle completion of the second half (the
                                 * write) of a block synchronization operation.
                                 */
                                g_mirror_sync_request(sc, bp);
                        else {
                                KASSERT(0,
                                    ("Invalid request cflags=0x%hx to=%s.",
                                    bp->bio_cflags, bp->bio_to->name));
                        }
                } else {
                        /*
                         * Initiate an I/O request.
                         */
                        g_mirror_register_request(sc, bp);
                }
                G_MIRROR_DEBUG(5, "%s: I'm here 9.", __func__);
        }
}

static void
g_mirror_update_idle(struct g_mirror_softc *sc, struct g_mirror_disk *disk)
{

        sx_assert(&sc->sc_lock, SX_LOCKED);

        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_NOFAILSYNC) != 0)
                return;
        if (!sc->sc_idle && (disk->d_flags & G_MIRROR_DISK_FLAG_DIRTY) == 0) {
                G_MIRROR_DEBUG(2, "Disk %s (device %s) marked as dirty.",
                    g_mirror_get_diskname(disk), sc->sc_name);
                disk->d_flags |= G_MIRROR_DISK_FLAG_DIRTY;
        } else if (sc->sc_idle &&
            (disk->d_flags & G_MIRROR_DISK_FLAG_DIRTY) != 0) {
                G_MIRROR_DEBUG(2, "Disk %s (device %s) marked as clean.",
                    g_mirror_get_diskname(disk), sc->sc_name);
                disk->d_flags &= ~G_MIRROR_DISK_FLAG_DIRTY;
        }
}

static void
g_mirror_sync_reinit(const struct g_mirror_disk *disk, struct bio *bp,
    off_t offset)
{
        void *data;
        int idx;

        data = bp->bio_data;
        idx = (int)(uintptr_t)bp->bio_caller1;
        g_reset_bio(bp);

        bp->bio_cmd = BIO_READ;
        bp->bio_data = data;
        bp->bio_done = g_mirror_sync_done;
        bp->bio_from = disk->d_sync.ds_consumer;
        bp->bio_to = disk->d_softc->sc_provider;
        bp->bio_caller1 = (void *)(uintptr_t)idx;
        bp->bio_offset = offset;
        bp->bio_length = MIN(maxphys,
            disk->d_softc->sc_mediasize - bp->bio_offset);
}

static void
g_mirror_sync_start(struct g_mirror_disk *disk)
{
        struct g_mirror_softc *sc;
        struct g_mirror_disk_sync *sync;
        struct g_consumer *cp;
        struct bio *bp;
        int error __diagused, i;

        g_topology_assert_not();
        sc = disk->d_softc;
        sync = &disk->d_sync;
        sx_assert(&sc->sc_lock, SX_LOCKED);

        KASSERT(disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING,
            ("Disk %s is not marked for synchronization.",
            g_mirror_get_diskname(disk)));
        KASSERT(sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING,
            ("Device not in RUNNING state (%s, %u).", sc->sc_name,
            sc->sc_state));

        sx_xunlock(&sc->sc_lock);
        g_topology_lock();
        cp = g_new_consumer(sc->sc_sync.ds_geom);
        cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE;
        error = g_attach(cp, sc->sc_provider);
        KASSERT(error == 0,
            ("Cannot attach to %s (error=%d).", sc->sc_name, error));
        error = g_access(cp, 1, 0, 0);
        KASSERT(error == 0, ("Cannot open %s (error=%d).", sc->sc_name, error));
        g_topology_unlock();
        sx_xlock(&sc->sc_lock);

        G_MIRROR_DEBUG(0, "Device %s: rebuilding provider %s.", sc->sc_name,
            g_mirror_get_diskname(disk));
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_NOFAILSYNC) == 0)
                disk->d_flags |= G_MIRROR_DISK_FLAG_DIRTY;
        KASSERT(sync->ds_consumer == NULL,
            ("Sync consumer already exists (device=%s, disk=%s).",
            sc->sc_name, g_mirror_get_diskname(disk)));

        sync->ds_consumer = cp;
        sync->ds_consumer->private = disk;
        sync->ds_consumer->index = 0;

        /*
         * Allocate memory for synchronization bios and initialize them.
         */
        sync->ds_bios = malloc(sizeof(struct bio *) * g_mirror_syncreqs,
            M_MIRROR, M_WAITOK);
        for (i = 0; i < g_mirror_syncreqs; i++) {
                bp = g_alloc_bio();
                sync->ds_bios[i] = bp;

                bp->bio_data = malloc(maxphys, M_MIRROR, M_WAITOK);
                bp->bio_caller1 = (void *)(uintptr_t)i;
                g_mirror_sync_reinit(disk, bp, sync->ds_offset);
                sync->ds_offset += bp->bio_length;
        }

        /* Increase the number of disks in SYNCHRONIZING state. */
        sc->sc_sync.ds_ndisks++;
        /* Set the number of in-flight synchronization requests. */
        sync->ds_inflight = g_mirror_syncreqs;

        /*
         * Fire off first synchronization requests.
         */
        for (i = 0; i < g_mirror_syncreqs; i++) {
                bp = sync->ds_bios[i];
                G_MIRROR_LOGREQ(3, bp, "Sending synchronization request.");
                sync->ds_consumer->index++;
                /*
                 * Delay the request if it is colliding with a regular request.
                 */
                if (g_mirror_regular_collision(sc, bp))
                        g_mirror_sync_delay(sc, bp);
                else
                        g_io_request(bp, sync->ds_consumer);
        }
}

/*
 * Stop synchronization process.
 * type: 0 - synchronization finished
 *       1 - synchronization stopped
 */
static void
g_mirror_sync_stop(struct g_mirror_disk *disk, int type)
{
        struct g_mirror_softc *sc;
        struct g_consumer *cp;

        g_topology_assert_not();
        sc = disk->d_softc;
        sx_assert(&sc->sc_lock, SX_LOCKED);

        KASSERT(disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING,
            ("Wrong disk state (%s, %s).", g_mirror_get_diskname(disk),
            g_mirror_disk_state2str(disk->d_state)));
        if (disk->d_sync.ds_consumer == NULL)
                return;

        if (type == 0) {
                G_MIRROR_DEBUG(0, "Device %s: rebuilding provider %s finished.",
                    sc->sc_name, g_mirror_get_diskname(disk));
        } else /* if (type == 1) */ {
                G_MIRROR_DEBUG(0, "Device %s: rebuilding provider %s stopped.",
                    sc->sc_name, g_mirror_get_diskname(disk));
        }
        g_mirror_regular_release(sc);
        free(disk->d_sync.ds_bios, M_MIRROR);
        disk->d_sync.ds_bios = NULL;
        cp = disk->d_sync.ds_consumer;
        disk->d_sync.ds_consumer = NULL;
        disk->d_flags &= ~G_MIRROR_DISK_FLAG_DIRTY;
        sc->sc_sync.ds_ndisks--;
        sx_xunlock(&sc->sc_lock); /* Avoid recursion on sc_lock. */
        g_topology_lock();
        g_mirror_kill_consumer(sc, cp);
        g_topology_unlock();
        sx_xlock(&sc->sc_lock);
}

static void
g_mirror_launch_provider(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;
        struct g_provider *pp, *dp;

        sx_assert(&sc->sc_lock, SX_LOCKED);

        g_topology_lock();
        pp = g_new_providerf(sc->sc_geom, "mirror/%s", sc->sc_name);
        pp->flags |= G_PF_DIRECT_RECEIVE;
        pp->mediasize = sc->sc_mediasize;
        pp->sectorsize = sc->sc_sectorsize;
        pp->stripesize = 0;
        pp->stripeoffset = 0;

        /* Splitting of unmapped BIO's could work but isn't implemented now */
        if (sc->sc_balance != G_MIRROR_BALANCE_SPLIT)
                pp->flags |= G_PF_ACCEPT_UNMAPPED;

        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_consumer && disk->d_consumer->provider) {
                        dp = disk->d_consumer->provider;
                        if (dp->stripesize > pp->stripesize) {
                                pp->stripesize = dp->stripesize;
                                pp->stripeoffset = dp->stripeoffset;
                        }
                        /* A provider underneath us doesn't support unmapped */
                        if ((dp->flags & G_PF_ACCEPT_UNMAPPED) == 0) {
                                G_MIRROR_DEBUG(0, "Cancelling unmapped "
                                    "because of %s.", dp->name);
                                pp->flags &= ~G_PF_ACCEPT_UNMAPPED;
                        }
                }
        }
        pp->private = sc;
        sc->sc_refcnt++;
        sc->sc_provider = pp;
        g_error_provider(pp, 0);
        g_topology_unlock();
        G_MIRROR_DEBUG(0, "Device %s launched (%u/%u).", pp->name,
            g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE), sc->sc_ndisks);
        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING)
                        g_mirror_sync_start(disk);
        }
}

static void
g_mirror_destroy_provider(struct g_mirror_softc *sc)
{
        struct g_mirror_disk *disk;
        struct bio *bp;

        g_topology_assert_not();
        KASSERT(sc->sc_provider != NULL, ("NULL provider (device=%s).",
            sc->sc_name));

        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                if (disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING)
                        g_mirror_sync_stop(disk, 1);
        }

        g_topology_lock();
        g_error_provider(sc->sc_provider, ENXIO);
        mtx_lock(&sc->sc_queue_mtx);
        while ((bp = TAILQ_FIRST(&sc->sc_queue)) != NULL) {
                TAILQ_REMOVE(&sc->sc_queue, bp, bio_queue);
                /*
                 * Abort any pending I/O that wasn't generated by us.
                 * Synchronization requests and requests destined for individual
                 * mirror components can be destroyed immediately.
                 */
                if (bp->bio_to == sc->sc_provider &&
                    bp->bio_from->geom != sc->sc_sync.ds_geom) {
                        g_io_deliver(bp, ENXIO);
                } else {
                        if ((bp->bio_cflags & G_MIRROR_BIO_FLAG_SYNC) != 0)
                                free(bp->bio_data, M_MIRROR);
                        g_destroy_bio(bp);
                }
        }
        mtx_unlock(&sc->sc_queue_mtx);
        g_wither_provider(sc->sc_provider, ENXIO);
        sc->sc_provider = NULL;
        G_MIRROR_DEBUG(0, "Device %s: provider destroyed.", sc->sc_name);
        g_topology_unlock();
}

static void
g_mirror_go(void *arg)
{
        struct g_mirror_softc *sc;
        struct g_mirror_event *ep;

        sc = arg;
        G_MIRROR_DEBUG(0, "Force device %s start due to timeout.", sc->sc_name);
        ep = sc->sc_timeout_event;
        sc->sc_timeout_event = NULL;
        g_mirror_event_dispatch(ep, sc, 0,
            G_MIRROR_EVENT_DONTWAIT | G_MIRROR_EVENT_DEVICE);
}

static void
g_mirror_timeout_drain(struct g_mirror_softc *sc)
{
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        callout_drain(&sc->sc_callout);
        g_mirror_event_free(sc->sc_timeout_event);
        sc->sc_timeout_event = NULL;
}

static u_int
g_mirror_determine_state(struct g_mirror_disk *disk)
{
        struct g_mirror_softc *sc;
        u_int state;

        sc = disk->d_softc;
        if (sc->sc_syncid == disk->d_sync.ds_syncid) {
                if ((disk->d_flags &
                    G_MIRROR_DISK_FLAG_SYNCHRONIZING) == 0 &&
                    (g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) == 0 ||
                     (disk->d_flags & G_MIRROR_DISK_FLAG_DIRTY) == 0)) {
                        /* Disk does not need synchronization. */
                        state = G_MIRROR_DISK_STATE_ACTIVE;
                } else {
                        if ((sc->sc_flags &
                             G_MIRROR_DEVICE_FLAG_NOAUTOSYNC) == 0 ||
                            (disk->d_flags &
                             G_MIRROR_DISK_FLAG_FORCE_SYNC) != 0) {
                                /*
                                 * We can start synchronization from
                                 * the stored offset.
                                 */
                                state = G_MIRROR_DISK_STATE_SYNCHRONIZING;
                        } else {
                                state = G_MIRROR_DISK_STATE_STALE;
                        }
                }
        } else if (disk->d_sync.ds_syncid < sc->sc_syncid) {
                /*
                 * Reset all synchronization data for this disk,
                 * because if it even was synchronized, it was
                 * synchronized to disks with different syncid.
                 */
                disk->d_flags |= G_MIRROR_DISK_FLAG_SYNCHRONIZING;
                disk->d_sync.ds_offset = 0;
                disk->d_sync.ds_offset_done = 0;
                disk->d_sync.ds_syncid = sc->sc_syncid;
                if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_NOAUTOSYNC) == 0 ||
                    (disk->d_flags & G_MIRROR_DISK_FLAG_FORCE_SYNC) != 0) {
                        state = G_MIRROR_DISK_STATE_SYNCHRONIZING;
                } else {
                        state = G_MIRROR_DISK_STATE_STALE;
                }
        } else /* if (sc->sc_syncid < disk->d_sync.ds_syncid) */ {
                /*
                 * Not good, NOT GOOD!
                 * It means that mirror was started on stale disks
                 * and more fresh disk just arrive.
                 * If there were writes, mirror is broken, sorry.
                 * I think the best choice here is don't touch
                 * this disk and inform the user loudly.
                 */
                G_MIRROR_DEBUG(0, "Device %s was started before the freshest "
                    "disk (%s) arrives!! It will not be connected to the "
                    "running device.", sc->sc_name,
                    g_mirror_get_diskname(disk));
                g_mirror_destroy_disk(disk);
                state = G_MIRROR_DISK_STATE_NONE;
                /* Return immediately, because disk was destroyed. */
                return (state);
        }
        G_MIRROR_DEBUG(3, "State for %s disk: %s.",
            g_mirror_get_diskname(disk), g_mirror_disk_state2str(state));
        return (state);
}

/*
 * Update device state.
 */
static void
g_mirror_update_device(struct g_mirror_softc *sc, bool force)
{
        struct g_mirror_disk *disk;
        u_int state;

        sx_assert(&sc->sc_lock, SX_XLOCKED);

        switch (sc->sc_state) {
        case G_MIRROR_DEVICE_STATE_STARTING:
            {
                struct g_mirror_disk *pdisk, *tdisk;
                const char *mismatch;
                uintmax_t found, newest;
                u_int dirty, ndisks;

                /* Pre-flight checks */
                LIST_FOREACH_SAFE(disk, &sc->sc_disks, d_next, tdisk) {
                        /*
                         * Confirm we already detected the newest genid.
                         */
                        KASSERT(sc->sc_genid >= disk->d_genid,
                            ("%s: found newer genid %u (sc:%p had %u).", __func__,
                            disk->d_genid, sc, sc->sc_genid));

                        /* Kick out any previously tasted stale components. */
                        if (disk->d_genid < sc->sc_genid) {
                                G_MIRROR_DEBUG(0, "Stale 'genid' field on %s "
                                    "(device %s) (component=%u latest=%u), skipping.",
                                    g_mirror_get_diskname(disk), sc->sc_name,
                                    disk->d_genid, sc->sc_genid);
                                g_mirror_destroy_disk(disk);
                                sc->sc_bump_id |= G_MIRROR_BUMP_SYNCID;
                                continue;
                        }

                        /*
                         * Confirm we already detected the newest syncid.
                         */
                        KASSERT(sc->sc_syncid >= disk->d_sync.ds_syncid,
                            ("%s: found newer syncid %u (sc:%p had %u).",
                             __func__, disk->d_sync.ds_syncid, sc,
                             sc->sc_syncid));

#define DETECT_MISMATCH(field, name) \
                        if (mismatch == NULL &&                                 \
                            disk->d_init_ ## field != sc->sc_ ## field) {       \
                                mismatch = name;                                \
                                found = (intmax_t)disk->d_init_ ## field;       \
                                newest = (intmax_t)sc->sc_ ## field;            \
                        }
                        mismatch = NULL;
                        DETECT_MISMATCH(ndisks, "md_all");
                        DETECT_MISMATCH(balance, "md_balance");
                        DETECT_MISMATCH(slice, "md_slice");
                        DETECT_MISMATCH(mediasize, "md_mediasize");
#undef DETECT_MISMATCH
                        if (mismatch != NULL) {
                                G_MIRROR_DEBUG(0, "Found a mismatching '%s' "
                                    "field on %s (device %s) (found=%ju "
                                    "newest=%ju).", mismatch,
                                    g_mirror_get_diskname(disk), sc->sc_name,
                                    found, newest);
                                g_mirror_destroy_disk(disk);
                                sc->sc_bump_id |= G_MIRROR_BUMP_SYNCID;
                                continue;
                        }
                }

                KASSERT(sc->sc_provider == NULL,
                    ("Non-NULL provider in STARTING state (%s).", sc->sc_name));
                /*
                 * Are we ready? If the timeout (force is true) has expired, and
                 * any disks are present, then yes. If we're permitted to launch
                 * before the timeout has expired and the expected number of
                 * current-generation mirror disks have been tasted, then yes.
                 */
                ndisks = g_mirror_ndisks(sc, -1);
                if ((force && ndisks > 0) ||
                    (g_launch_mirror_before_timeout && ndisks == sc->sc_ndisks)) {
                        ;
                } else if (ndisks == 0) {
                        /*
                         * Disks went down in starting phase, so destroy
                         * device.
                         */
                        g_mirror_timeout_drain(sc);
                        sc->sc_flags |= G_MIRROR_DEVICE_FLAG_DESTROY;
                        G_MIRROR_DEBUG(1, "root_mount_rel[%u] %p", __LINE__,
                            sc->sc_rootmount);
                        root_mount_rel(sc->sc_rootmount);
                        sc->sc_rootmount = NULL;
                        return;
                } else {
                        return;
                }

                /*
                 * Activate all disks with the biggest syncid.
                 */
                if (force) {
                        /*
                         * If 'force' is true, we have been called due to
                         * timeout, so don't bother canceling timeout.
                         */
                        ndisks = 0;
                        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                                if ((disk->d_flags &
                                    G_MIRROR_DISK_FLAG_SYNCHRONIZING) == 0) {
                                        ndisks++;
                                }
                        }
                        if (ndisks == 0) {
                                /* No valid disks found, destroy device. */
                                sc->sc_flags |= G_MIRROR_DEVICE_FLAG_DESTROY;
                                G_MIRROR_DEBUG(1, "root_mount_rel[%u] %p",
                                    __LINE__, sc->sc_rootmount);
                                root_mount_rel(sc->sc_rootmount);
                                sc->sc_rootmount = NULL;
                                return;
                        }
                } else {
                        /* Cancel timeout. */
                        g_mirror_timeout_drain(sc);
                }

                /*
                 * Here we need to look for dirty disks and if all disks
                 * with the biggest syncid are dirty, we have to choose
                 * one with the biggest priority and rebuild the rest.
                 */
                /*
                 * Find the number of dirty disks with the biggest syncid.
                 * Find the number of disks with the biggest syncid.
                 * While here, find a disk with the biggest priority.
                 */
                dirty = ndisks = 0;
                pdisk = NULL;
                LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                        if (disk->d_sync.ds_syncid != sc->sc_syncid)
                                continue;
                        if ((disk->d_flags &
                            G_MIRROR_DISK_FLAG_SYNCHRONIZING) != 0) {
                                continue;
                        }
                        ndisks++;
                        if ((disk->d_flags & G_MIRROR_DISK_FLAG_DIRTY) != 0) {
                                dirty++;
                                if (pdisk == NULL ||
                                    pdisk->d_priority < disk->d_priority) {
                                        pdisk = disk;
                                }
                        }
                }
                if (dirty == 0) {
                        /* No dirty disks at all, great. */
                } else if (dirty == ndisks) {
                        /*
                         * Force synchronization for all dirty disks except one
                         * with the biggest priority.
                         */
                        KASSERT(pdisk != NULL, ("pdisk == NULL"));
                        G_MIRROR_DEBUG(1, "Using disk %s (device %s) as a "
                            "master disk for synchronization.",
                            g_mirror_get_diskname(pdisk), sc->sc_name);
                        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                                if (disk->d_sync.ds_syncid != sc->sc_syncid)
                                        continue;
                                if ((disk->d_flags &
                                    G_MIRROR_DISK_FLAG_SYNCHRONIZING) != 0) {
                                        continue;
                                }
                                KASSERT((disk->d_flags &
                                    G_MIRROR_DISK_FLAG_DIRTY) != 0,
                                    ("Disk %s isn't marked as dirty.",
                                    g_mirror_get_diskname(disk)));
                                /* Skip the disk with the biggest priority. */
                                if (disk == pdisk)
                                        continue;
                                disk->d_sync.ds_syncid = 0;
                        }
                } else if (dirty < ndisks) {
                        /*
                         * Force synchronization for all dirty disks.
                         * We have some non-dirty disks.
                         */
                        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                                if (disk->d_sync.ds_syncid != sc->sc_syncid)
                                        continue;
                                if ((disk->d_flags &
                                    G_MIRROR_DISK_FLAG_SYNCHRONIZING) != 0) {
                                        continue;
                                }
                                if ((disk->d_flags &
                                    G_MIRROR_DISK_FLAG_DIRTY) == 0) {
                                        continue;
                                }
                                disk->d_sync.ds_syncid = 0;
                        }
                }

                /* Reset hint. */
                sc->sc_hint = NULL;
                if (force) {
                        /* Remember to bump syncid on first write. */
                        sc->sc_bump_id |= G_MIRROR_BUMP_SYNCID;
                }
                state = G_MIRROR_DEVICE_STATE_RUNNING;
                G_MIRROR_DEBUG(1, "Device %s state changed from %s to %s.",
                    sc->sc_name, g_mirror_device_state2str(sc->sc_state),
                    g_mirror_device_state2str(state));
                sc->sc_state = state;
                LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                        state = g_mirror_determine_state(disk);
                        g_mirror_event_send(disk, state,
                            G_MIRROR_EVENT_DONTWAIT);
                        if (state == G_MIRROR_DISK_STATE_STALE)
                                sc->sc_bump_id |= G_MIRROR_BUMP_SYNCID;
                }
                break;
            }
        case G_MIRROR_DEVICE_STATE_RUNNING:
                if (g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE) == 0 &&
                    g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_NEW) == 0) {
                        /*
                         * No usable disks, so destroy the device.
                         */
                        sc->sc_flags |= G_MIRROR_DEVICE_FLAG_DESTROY;
                        break;
                } else if (g_mirror_ndisks(sc,
                    G_MIRROR_DISK_STATE_ACTIVE) > 0 &&
                    g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_NEW) == 0) {
                        /*
                         * We have active disks, launch provider if it doesn't
                         * exist.
                         */
                        if (sc->sc_provider == NULL)
                                g_mirror_launch_provider(sc);
                        if (sc->sc_rootmount != NULL) {
                                G_MIRROR_DEBUG(1, "root_mount_rel[%u] %p",
                                    __LINE__, sc->sc_rootmount);
                                root_mount_rel(sc->sc_rootmount);
                                sc->sc_rootmount = NULL;
                        }
                }
                /*
                 * Genid should be bumped immediately, so do it here.
                 */
                if ((sc->sc_bump_id & G_MIRROR_BUMP_GENID) != 0) {
                        sc->sc_bump_id &= ~G_MIRROR_BUMP_GENID;
                        g_mirror_bump_genid(sc);
                }
                if ((sc->sc_bump_id & G_MIRROR_BUMP_SYNCID_NOW) != 0) {
                        sc->sc_bump_id &= ~G_MIRROR_BUMP_SYNCID_NOW;
                        g_mirror_bump_syncid(sc);
                }
                break;
        default:
                KASSERT(1 == 0, ("Wrong device state (%s, %s).",
                    sc->sc_name, g_mirror_device_state2str(sc->sc_state)));
                break;
        }
}

/*
 * Update disk state and device state if needed.
 */
#define DISK_STATE_CHANGED()    G_MIRROR_DEBUG(1,                       \
        "Disk %s state changed from %s to %s (device %s).",             \
        g_mirror_get_diskname(disk),                                    \
        g_mirror_disk_state2str(disk->d_state),                         \
        g_mirror_disk_state2str(state), sc->sc_name)
static int
g_mirror_update_disk(struct g_mirror_disk *disk, u_int state)
{
        struct g_mirror_softc *sc;

        sc = disk->d_softc;
        sx_assert(&sc->sc_lock, SX_XLOCKED);

again:
        G_MIRROR_DEBUG(3, "Changing disk %s state from %s to %s.",
            g_mirror_get_diskname(disk), g_mirror_disk_state2str(disk->d_state),
            g_mirror_disk_state2str(state));
        switch (state) {
        case G_MIRROR_DISK_STATE_NEW:
                /*
                 * Possible scenarios:
                 * 1. New disk arrive.
                 */
                /* Previous state should be NONE. */
                KASSERT(disk->d_state == G_MIRROR_DISK_STATE_NONE,
                    ("Wrong disk state (%s, %s).", g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                DISK_STATE_CHANGED();

                disk->d_state = state;
                g_topology_lock();
                if (LIST_EMPTY(&sc->sc_disks))
                        LIST_INSERT_HEAD(&sc->sc_disks, disk, d_next);
                else {
                        struct g_mirror_disk *dp;

                        LIST_FOREACH(dp, &sc->sc_disks, d_next) {
                                if (disk->d_priority >= dp->d_priority) {
                                        LIST_INSERT_BEFORE(dp, disk, d_next);
                                        dp = NULL;
                                        break;
                                }
                                if (LIST_NEXT(dp, d_next) == NULL)
                                        break;
                        }
                        if (dp != NULL)
                                LIST_INSERT_AFTER(dp, disk, d_next);
                }
                g_topology_unlock();
                G_MIRROR_DEBUG(1, "Device %s: provider %s detected.",
                    sc->sc_name, g_mirror_get_diskname(disk));
                if (sc->sc_state == G_MIRROR_DEVICE_STATE_STARTING)
                        break;
                KASSERT(sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING,
                    ("Wrong device state (%s, %s, %s, %s).", sc->sc_name,
                    g_mirror_device_state2str(sc->sc_state),
                    g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                state = g_mirror_determine_state(disk);
                if (state != G_MIRROR_DISK_STATE_NONE)
                        goto again;
                break;
        case G_MIRROR_DISK_STATE_ACTIVE:
                /*
                 * Possible scenarios:
                 * 1. New disk does not need synchronization.
                 * 2. Synchronization process finished successfully.
                 */
                KASSERT(sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING,
                    ("Wrong device state (%s, %s, %s, %s).", sc->sc_name,
                    g_mirror_device_state2str(sc->sc_state),
                    g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                /* Previous state should be NEW or SYNCHRONIZING. */
                KASSERT(disk->d_state == G_MIRROR_DISK_STATE_NEW ||
                    disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING,
                    ("Wrong disk state (%s, %s).", g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                DISK_STATE_CHANGED();

                if (disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING) {
                        disk->d_flags &= ~G_MIRROR_DISK_FLAG_SYNCHRONIZING;
                        disk->d_flags &= ~G_MIRROR_DISK_FLAG_FORCE_SYNC;
                        g_mirror_sync_stop(disk, 0);
                }
                disk->d_state = state;
                disk->d_sync.ds_offset = 0;
                disk->d_sync.ds_offset_done = 0;
                g_mirror_update_idle(sc, disk);
                g_mirror_update_metadata(disk);
                G_MIRROR_DEBUG(1, "Device %s: provider %s activated.",
                    sc->sc_name, g_mirror_get_diskname(disk));
                break;
        case G_MIRROR_DISK_STATE_STALE:
                /*
                 * Possible scenarios:
                 * 1. Stale disk was connected.
                 */
                /* Previous state should be NEW. */
                KASSERT(disk->d_state == G_MIRROR_DISK_STATE_NEW,
                    ("Wrong disk state (%s, %s).", g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                KASSERT(sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING,
                    ("Wrong device state (%s, %s, %s, %s).", sc->sc_name,
                    g_mirror_device_state2str(sc->sc_state),
                    g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                /*
                 * STALE state is only possible if device is marked
                 * NOAUTOSYNC.
                 */
                KASSERT((sc->sc_flags & G_MIRROR_DEVICE_FLAG_NOAUTOSYNC) != 0,
                    ("Wrong device state (%s, %s, %s, %s).", sc->sc_name,
                    g_mirror_device_state2str(sc->sc_state),
                    g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                DISK_STATE_CHANGED();

                disk->d_flags &= ~G_MIRROR_DISK_FLAG_DIRTY;
                disk->d_state = state;
                g_mirror_update_metadata(disk);
                G_MIRROR_DEBUG(0, "Device %s: provider %s is stale.",
                    sc->sc_name, g_mirror_get_diskname(disk));
                break;
        case G_MIRROR_DISK_STATE_SYNCHRONIZING:
                /*
                 * Possible scenarios:
                 * 1. Disk which needs synchronization was connected.
                 */
                /* Previous state should be NEW. */
                KASSERT(disk->d_state == G_MIRROR_DISK_STATE_NEW,
                    ("Wrong disk state (%s, %s).", g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                KASSERT(sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING,
                    ("Wrong device state (%s, %s, %s, %s).", sc->sc_name,
                    g_mirror_device_state2str(sc->sc_state),
                    g_mirror_get_diskname(disk),
                    g_mirror_disk_state2str(disk->d_state)));
                DISK_STATE_CHANGED();

                if (disk->d_state == G_MIRROR_DISK_STATE_NEW)
                        disk->d_flags &= ~G_MIRROR_DISK_FLAG_DIRTY;
                disk->d_state = state;
                if (sc->sc_provider != NULL) {
                        g_mirror_sync_start(disk);
                        g_mirror_update_metadata(disk);
                }
                break;
        case G_MIRROR_DISK_STATE_DISCONNECTED:
                /*
                 * Possible scenarios:
                 * 1. Device wasn't running yet, but disk disappear.
                 * 2. Disk was active and disapppear.
                 * 3. Disk disappear during synchronization process.
                 */
                if (sc->sc_state == G_MIRROR_DEVICE_STATE_RUNNING) {
                        /*
                         * Previous state should be ACTIVE, STALE or
                         * SYNCHRONIZING.
                         */
                        KASSERT(disk->d_state == G_MIRROR_DISK_STATE_ACTIVE ||
                            disk->d_state == G_MIRROR_DISK_STATE_STALE ||
                            disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING,
                            ("Wrong disk state (%s, %s).",
                            g_mirror_get_diskname(disk),
                            g_mirror_disk_state2str(disk->d_state)));
                } else if (sc->sc_state == G_MIRROR_DEVICE_STATE_STARTING) {
                        /* Previous state should be NEW. */
                        KASSERT(disk->d_state == G_MIRROR_DISK_STATE_NEW,
                            ("Wrong disk state (%s, %s).",
                            g_mirror_get_diskname(disk),
                            g_mirror_disk_state2str(disk->d_state)));
                        /*
                         * Reset bumping syncid if disk disappeared in STARTING
                         * state.
                         */
                        if ((sc->sc_bump_id & G_MIRROR_BUMP_SYNCID) != 0)
                                sc->sc_bump_id &= ~G_MIRROR_BUMP_SYNCID;
#ifdef  INVARIANTS
                } else {
                        KASSERT(1 == 0, ("Wrong device state (%s, %s, %s, %s).",
                            sc->sc_name,
                            g_mirror_device_state2str(sc->sc_state),
                            g_mirror_get_diskname(disk),
                            g_mirror_disk_state2str(disk->d_state)));
#endif
                }
                DISK_STATE_CHANGED();
                G_MIRROR_DEBUG(0, "Device %s: provider %s disconnected.",
                    sc->sc_name, g_mirror_get_diskname(disk));

                g_mirror_destroy_disk(disk);
                break;
        case G_MIRROR_DISK_STATE_DESTROY:
            {
                int error;

                error = g_mirror_clear_metadata(disk);
                if (error != 0) {
                        G_MIRROR_DEBUG(0,
                            "Device %s: failed to clear metadata on %s: %d.",
                            sc->sc_name, g_mirror_get_diskname(disk), error);
                        break;
                }
                DISK_STATE_CHANGED();
                G_MIRROR_DEBUG(0, "Device %s: provider %s destroyed.",
                    sc->sc_name, g_mirror_get_diskname(disk));

                g_mirror_destroy_disk(disk);
                sc->sc_ndisks--;
                LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                        g_mirror_update_metadata(disk);
                }
                break;
            }
        default:
                KASSERT(1 == 0, ("Unknown state (%u).", state));
                break;
        }
        return (0);
}
#undef  DISK_STATE_CHANGED

int
g_mirror_read_metadata(struct g_consumer *cp, struct g_mirror_metadata *md)
{
        struct g_provider *pp;
        u_char *buf;
        int error;

        g_topology_assert();

        error = g_access(cp, 1, 0, 0);
        if (error != 0)
                return (error);
        pp = cp->provider;
        g_topology_unlock();
        /* Metadata are stored on last sector. */
        buf = g_read_data(cp, pp->mediasize - pp->sectorsize, pp->sectorsize,
            &error);
        g_topology_lock();
        g_access(cp, -1, 0, 0);
        if (buf == NULL) {
                G_MIRROR_DEBUG(1, "Cannot read metadata from %s (error=%d).",
                    cp->provider->name, error);
                return (error);
        }

        /* Decode metadata. */
        error = mirror_metadata_decode(buf, md);
        g_free(buf);
        if (strcmp(md->md_magic, G_MIRROR_MAGIC) != 0)
                return (EINVAL);
        if (md->md_version > G_MIRROR_VERSION) {
                G_MIRROR_DEBUG(0,
                    "Kernel module is too old to handle metadata from %s.",
                    cp->provider->name);
                return (EINVAL);
        }
        if (error != 0) {
                G_MIRROR_DEBUG(1, "MD5 metadata hash mismatch for provider %s.",
                    cp->provider->name);
                return (error);
        }

        return (0);
}

static int
g_mirror_check_metadata(struct g_mirror_softc *sc, struct g_provider *pp,
    struct g_mirror_metadata *md)
{

        G_MIRROR_DEBUG(2, "%s: md_did 0x%u disk %s device %s md_all 0x%x "
            "sc_ndisks 0x%x md_slice 0x%x sc_slice 0x%x md_balance 0x%x "
            "sc_balance 0x%x sc_mediasize 0x%jx pp_mediasize 0x%jx "
            "md_sectorsize 0x%x sc_sectorsize 0x%x md_mflags 0x%jx "
            "md_dflags 0x%jx md_syncid 0x%x md_genid 0x%x md_priority 0x%x "
            "sc_state 0x%x.",
            __func__, md->md_did, pp->name, sc->sc_name, md->md_all,
            sc->sc_ndisks, md->md_slice, sc->sc_slice, md->md_balance,
            sc->sc_balance, (uintmax_t)sc->sc_mediasize,
            (uintmax_t)pp->mediasize, md->md_sectorsize, sc->sc_sectorsize,
            (uintmax_t)md->md_mflags, (uintmax_t)md->md_dflags, md->md_syncid,
            md->md_genid, md->md_priority, sc->sc_state);

        if (g_mirror_id2disk(sc, md->md_did) != NULL) {
                G_MIRROR_DEBUG(1, "Disk %s (id=%u) already exists, skipping.",
                    pp->name, md->md_did);
                return (EEXIST);
        }
        if (sc->sc_mediasize > pp->mediasize) {
                G_MIRROR_DEBUG(1,
                    "Invalid size of disk %s (device %s), skipping.", pp->name,
                    sc->sc_name);
                return (EINVAL);
        }
        if (md->md_sectorsize != sc->sc_sectorsize) {
                G_MIRROR_DEBUG(1,
                    "Invalid '%s' field on disk %s (device %s), skipping.",
                    "md_sectorsize", pp->name, sc->sc_name);
                return (EINVAL);
        }
        if ((sc->sc_sectorsize % pp->sectorsize) != 0) {
                G_MIRROR_DEBUG(1,
                    "Invalid sector size of disk %s (device %s), skipping.",
                    pp->name, sc->sc_name);
                return (EINVAL);
        }
        if ((md->md_mflags & ~G_MIRROR_DEVICE_FLAG_MASK) != 0) {
                G_MIRROR_DEBUG(1,
                    "Invalid device flags on disk %s (device %s), skipping.",
                    pp->name, sc->sc_name);
                return (EINVAL);
        }
        if ((md->md_dflags & ~G_MIRROR_DISK_FLAG_MASK) != 0) {
                G_MIRROR_DEBUG(1,
                    "Invalid disk flags on disk %s (device %s), skipping.",
                    pp->name, sc->sc_name);
                return (EINVAL);
        }
        return (0);
}

int
g_mirror_add_disk(struct g_mirror_softc *sc, struct g_provider *pp,
    struct g_mirror_metadata *md)
{
        struct g_mirror_disk *disk;
        int error;

        g_topology_assert_not();
        G_MIRROR_DEBUG(2, "Adding disk %s.", pp->name);

        error = g_mirror_check_metadata(sc, pp, md);
        if (error != 0)
                return (error);

        if (md->md_genid < sc->sc_genid) {
                G_MIRROR_DEBUG(0, "Component %s (device %s) broken, skipping.",
                    pp->name, sc->sc_name);
                return (EINVAL);
        }

        /*
         * If the component disk we're tasting has newer metadata than the
         * STARTING gmirror device, refresh the device from the component.
         */
        error = g_mirror_refresh_device(sc, pp, md);
        if (error != 0)
                return (error);

        disk = g_mirror_init_disk(sc, pp, md, &error);
        if (disk == NULL)
                return (error);
        error = g_mirror_event_send(disk, G_MIRROR_DISK_STATE_NEW,
            G_MIRROR_EVENT_WAIT);
        if (error != 0)
                return (error);
        if (md->md_version < G_MIRROR_VERSION) {
                G_MIRROR_DEBUG(0, "Upgrading metadata on %s (v%d->v%d).",
                    pp->name, md->md_version, G_MIRROR_VERSION);
                g_mirror_update_metadata(disk);
        }
        return (0);
}

static void
g_mirror_destroy_delayed(void *arg, int flag)
{
        struct g_mirror_softc *sc;
        int error;

        if (flag == EV_CANCEL) {
                G_MIRROR_DEBUG(1, "Destroying canceled.");
                return;
        }
        sc = arg;
        g_topology_unlock();
        sx_xlock(&sc->sc_lock);
        KASSERT((sc->sc_flags & G_MIRROR_DEVICE_FLAG_DESTROY) == 0,
            ("DESTROY flag set on %s.", sc->sc_name));
        KASSERT((sc->sc_flags & G_MIRROR_DEVICE_FLAG_CLOSEWAIT) != 0,
            ("CLOSEWAIT flag not set on %s.", sc->sc_name));
        G_MIRROR_DEBUG(1, "Destroying %s (delayed).", sc->sc_name);
        error = g_mirror_destroy(sc, G_MIRROR_DESTROY_SOFT);
        if (error != 0) {
                G_MIRROR_DEBUG(0, "Cannot destroy %s (error=%d).",
                    sc->sc_name, error);
                sx_xunlock(&sc->sc_lock);
        }
        g_topology_lock();
}

static int
g_mirror_access(struct g_provider *pp, int acr, int acw, int ace)
{
        struct g_mirror_softc *sc;
        int error = 0;

        g_topology_assert();
        G_MIRROR_DEBUG(2, "Access request for %s: r%dw%de%d.", pp->name, acr,
            acw, ace);

        sc = pp->private;
        KASSERT(sc != NULL, ("NULL softc (provider=%s).", pp->name));

        g_topology_unlock();
        sx_xlock(&sc->sc_lock);
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_DESTROY) != 0 ||
            (sc->sc_flags & G_MIRROR_DEVICE_FLAG_CLOSEWAIT) != 0 ||
            LIST_EMPTY(&sc->sc_disks)) {
                if (acr > 0 || acw > 0 || ace > 0)
                        error = ENXIO;
                goto end;
        }
        sc->sc_provider_open += acr + acw + ace;
        if (pp->acw + acw == 0)
                g_mirror_idle(sc, 0);
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_CLOSEWAIT) != 0 &&
            sc->sc_provider_open == 0)
                g_post_event(g_mirror_destroy_delayed, sc, M_WAITOK, sc, NULL);
end:
        sx_xunlock(&sc->sc_lock);
        g_topology_lock();
        return (error);
}

static void
g_mirror_reinit_from_metadata(struct g_mirror_softc *sc,
    const struct g_mirror_metadata *md)
{

        sc->sc_genid = md->md_genid;
        sc->sc_syncid = md->md_syncid;

        sc->sc_slice = md->md_slice;
        sc->sc_balance = md->md_balance;
        sc->sc_mediasize = md->md_mediasize;
        sc->sc_ndisks = md->md_all;
        sc->sc_flags &= ~G_MIRROR_DEVICE_FLAG_MASK;
        sc->sc_flags |= (md->md_mflags & G_MIRROR_DEVICE_FLAG_MASK);
}

struct g_geom *
g_mirror_create(struct g_class *mp, const struct g_mirror_metadata *md,
    u_int type)
{
        struct g_mirror_softc *sc;
        struct g_geom *gp;
        int error, timeout;

        g_topology_assert();
        G_MIRROR_DEBUG(1, "Creating device %s (id=%u).", md->md_name,
            md->md_mid);

        /* One disk is minimum. */
        if (md->md_all < 1)
                return (NULL);
        /*
         * Action geom.
         */
        gp = g_new_geom(mp, md->md_name);
        sc = malloc(sizeof(*sc), M_MIRROR, M_WAITOK | M_ZERO);
        gp->start = g_mirror_start;
        gp->orphan = g_mirror_orphan;
        gp->access = g_mirror_access;
        gp->dumpconf = g_mirror_dumpconf;

        sc->sc_type = type;
        sc->sc_id = md->md_mid;
        g_mirror_reinit_from_metadata(sc, md);
        sc->sc_sectorsize = md->md_sectorsize;
        sc->sc_bump_id = 0;
        sc->sc_idle = 1;
        sc->sc_last_write = time_uptime;
        sc->sc_writes = 0;
        sc->sc_refcnt = 1;
        sx_init(&sc->sc_lock, "gmirror:lock");
        TAILQ_INIT(&sc->sc_queue);
        mtx_init(&sc->sc_queue_mtx, "gmirror:queue", NULL, MTX_DEF);
        TAILQ_INIT(&sc->sc_regular_delayed);
        TAILQ_INIT(&sc->sc_inflight);
        TAILQ_INIT(&sc->sc_sync_delayed);
        LIST_INIT(&sc->sc_disks);
        TAILQ_INIT(&sc->sc_events);
        mtx_init(&sc->sc_events_mtx, "gmirror:events", NULL, MTX_DEF);
        callout_init(&sc->sc_callout, 1);
        mtx_init(&sc->sc_done_mtx, "gmirror:done", NULL, MTX_DEF);
        sc->sc_state = G_MIRROR_DEVICE_STATE_STARTING;
        gp->softc = sc;
        sc->sc_geom = gp;
        sc->sc_provider = NULL;
        sc->sc_provider_open = 0;
        /*
         * Synchronization geom.
         */
        gp = g_new_geomf(mp, "%s.sync", md->md_name);
        gp->softc = sc;
        gp->orphan = g_mirror_orphan;
        sc->sc_sync.ds_geom = gp;
        sc->sc_sync.ds_ndisks = 0;
        error = kproc_create(g_mirror_worker, sc, &sc->sc_worker, 0, 0,
            "g_mirror %s", md->md_name);
        if (error != 0) {
                G_MIRROR_DEBUG(1, "Cannot create kernel thread for %s.",
                    sc->sc_name);
                g_destroy_geom(sc->sc_sync.ds_geom);
                g_destroy_geom(sc->sc_geom);
                g_mirror_free_device(sc);
                return (NULL);
        }

        G_MIRROR_DEBUG(1, "Device %s created (%u components, id=%u).",
            sc->sc_name, sc->sc_ndisks, sc->sc_id);

        sc->sc_rootmount = root_mount_hold("GMIRROR");
        G_MIRROR_DEBUG(1, "root_mount_hold %p", sc->sc_rootmount);

        /*
         * Schedule startup timeout.
         */
        timeout = g_mirror_timeout * hz;
        sc->sc_timeout_event = malloc(sizeof(struct g_mirror_event), M_MIRROR,
            M_WAITOK);
        callout_reset(&sc->sc_callout, timeout, g_mirror_go, sc);
        return (sc->sc_geom);
}

int
g_mirror_destroy(struct g_mirror_softc *sc, int how)
{
        struct g_mirror_disk *disk;

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        if (sc->sc_provider_open != 0) {
                switch (how) {
                case G_MIRROR_DESTROY_SOFT:
                        G_MIRROR_DEBUG(1,
                            "Device %s is still open (%d).", sc->sc_name,
                            sc->sc_provider_open);
                        return (EBUSY);
                case G_MIRROR_DESTROY_DELAYED:
                        G_MIRROR_DEBUG(1,
                            "Device %s will be destroyed on last close.",
                            sc->sc_name);
                        LIST_FOREACH(disk, &sc->sc_disks, d_next) {
                                if (disk->d_state ==
                                    G_MIRROR_DISK_STATE_SYNCHRONIZING) {
                                        g_mirror_sync_stop(disk, 1);
                                }
                        }
                        sc->sc_flags |= G_MIRROR_DEVICE_FLAG_CLOSEWAIT;
                        return (EBUSY);
                case G_MIRROR_DESTROY_HARD:
                        G_MIRROR_DEBUG(1, "Device %s is still open, so it "
                            "can't be definitely removed.", sc->sc_name);
                }
        }

        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_DESTROY) != 0) {
                sx_xunlock(&sc->sc_lock);
                return (0);
        }
        sc->sc_flags |= G_MIRROR_DEVICE_FLAG_DESTROY;
        sc->sc_flags |= G_MIRROR_DEVICE_FLAG_DRAIN;
        G_MIRROR_DEBUG(4, "%s: Waking up %p.", __func__, sc);
        sx_xunlock(&sc->sc_lock);
        mtx_lock(&sc->sc_queue_mtx);
        wakeup(sc);
        mtx_unlock(&sc->sc_queue_mtx);
        G_MIRROR_DEBUG(4, "%s: Sleeping %p.", __func__, &sc->sc_worker);
        while (sc->sc_worker != NULL)
                tsleep(&sc->sc_worker, PRIBIO, "m:destroy", hz / 5);
        G_MIRROR_DEBUG(4, "%s: Woken up %p.", __func__, &sc->sc_worker);
        sx_xlock(&sc->sc_lock);
        g_mirror_destroy_device(sc);
        return (0);
}

static void
g_mirror_taste_orphan(struct g_consumer *cp)
{

        KASSERT(1 == 0, ("%s called while tasting %s.", __func__,
            cp->provider->name));
}

static struct g_geom *
g_mirror_taste(struct g_class *mp, struct g_provider *pp, int flags __unused)
{
        struct g_mirror_metadata md;
        struct g_mirror_softc *sc;
        struct g_consumer *cp;
        struct g_geom *gp;
        int error;

        g_topology_assert();
        g_trace(G_T_TOPOLOGY, "%s(%s, %s)", __func__, mp->name, pp->name);
        G_MIRROR_DEBUG(2, "Tasting %s.", pp->name);

        gp = g_new_geom(mp, "mirror:taste");
        /*
         * This orphan function should be never called.
         */
        gp->orphan = g_mirror_taste_orphan;
        cp = g_new_consumer(gp);
        cp->flags |= G_CF_DIRECT_SEND | G_CF_DIRECT_RECEIVE;
        error = g_attach(cp, pp);
        if (error == 0) {
                error = g_mirror_read_metadata(cp, &md);
                g_detach(cp);
        }
        g_destroy_consumer(cp);
        g_destroy_geom(gp);
        if (error != 0)
                return (NULL);
        gp = NULL;

        if (md.md_provider[0] != '\0' &&
            !g_compare_names(md.md_provider, pp->name))
                return (NULL);
        if (md.md_provsize != 0 && md.md_provsize != pp->mediasize)
                return (NULL);
        if ((md.md_dflags & G_MIRROR_DISK_FLAG_INACTIVE) != 0) {
                G_MIRROR_DEBUG(0,
                    "Device %s: provider %s marked as inactive, skipping.",
                    md.md_name, pp->name);
                return (NULL);
        }
        if (g_mirror_debug >= 2)
                mirror_metadata_dump(&md);

        /*
         * Let's check if device already exists.
         */
        sc = NULL;
        LIST_FOREACH(gp, &mp->geom, geom) {
                sc = gp->softc;
                if (sc == NULL)
                        continue;
                if (sc->sc_type != G_MIRROR_TYPE_AUTOMATIC)
                        continue;
                if (sc->sc_sync.ds_geom == gp)
                        continue;
                if (strcmp(md.md_name, sc->sc_name) != 0)
                        continue;
                if (md.md_mid != sc->sc_id) {
                        G_MIRROR_DEBUG(0, "Device %s already configured.",
                            sc->sc_name);
                        return (NULL);
                }
                break;
        }
        if (gp == NULL) {
                gp = g_mirror_create(mp, &md, G_MIRROR_TYPE_AUTOMATIC);
                if (gp == NULL) {
                        G_MIRROR_DEBUG(0, "Cannot create device %s.",
                            md.md_name);
                        return (NULL);
                }
                sc = gp->softc;
        }
        G_MIRROR_DEBUG(1, "Adding disk %s to %s.", pp->name, gp->name);
        g_topology_unlock();
        sx_xlock(&sc->sc_lock);
        sc->sc_flags |= G_MIRROR_DEVICE_FLAG_TASTING;
        error = g_mirror_add_disk(sc, pp, &md);
        sc->sc_flags &= ~G_MIRROR_DEVICE_FLAG_TASTING;
        if (error != 0) {
                G_MIRROR_DEBUG(0, "Cannot add disk %s to %s (error=%d).",
                    pp->name, gp->name, error);
                if (LIST_EMPTY(&sc->sc_disks)) {
                        g_cancel_event(sc);
                        g_mirror_destroy(sc, G_MIRROR_DESTROY_HARD);
                        g_topology_lock();
                        return (NULL);
                }
                gp = NULL;
        }
        if ((sc->sc_flags & G_MIRROR_DEVICE_FLAG_DESTROY) != 0) {
                g_mirror_destroy(sc, G_MIRROR_DESTROY_HARD);
                g_topology_lock();
                return (NULL);
        }
        sx_xunlock(&sc->sc_lock);
        g_topology_lock();
        return (gp);
}

static void
g_mirror_resize(struct g_consumer *cp)
{
        struct g_mirror_disk *disk;

        g_topology_assert();
        g_trace(G_T_TOPOLOGY, "%s(%s)", __func__, cp->provider->name);

        disk = cp->private;
        if (disk == NULL)
                return;
        g_topology_unlock();
        g_mirror_update_metadata(disk);
        g_topology_lock();
}

static int
g_mirror_destroy_geom(struct gctl_req *req __unused,
    struct g_class *mp __unused, struct g_geom *gp)
{
        struct g_mirror_softc *sc;
        int error;

        g_topology_unlock();
        sc = gp->softc;
        sx_xlock(&sc->sc_lock);
        g_cancel_event(sc);
        error = g_mirror_destroy(gp->softc, G_MIRROR_DESTROY_SOFT);
        if (error != 0)
                sx_xunlock(&sc->sc_lock);
        g_topology_lock();
        return (error);
}

static void
g_mirror_dumpconf(struct sbuf *sb, const char *indent, struct g_geom *gp,
    struct g_consumer *cp, struct g_provider *pp)
{
        struct g_mirror_softc *sc;

        g_topology_assert();

        sc = gp->softc;
        if (sc == NULL)
                return;
        /* Skip synchronization geom. */
        if (gp == sc->sc_sync.ds_geom)
                return;
        if (pp != NULL) {
                /* Nothing here. */
        } else if (cp != NULL) {
                struct g_mirror_disk *disk;

                disk = cp->private;
                if (disk == NULL)
                        return;
                sbuf_printf(sb, "%s<ID>%u</ID>\n", indent, (u_int)disk->d_id);
                if (disk->d_state == G_MIRROR_DISK_STATE_SYNCHRONIZING) {
                        sbuf_printf(sb, "%s<Synchronized>", indent);
                        if (disk->d_sync.ds_offset == 0)
                                sbuf_cat(sb, "0%");
                        else
                                sbuf_printf(sb, "%u%%",
                                    (u_int)((disk->d_sync.ds_offset * 100) /
                                    sc->sc_mediasize));
                        sbuf_cat(sb, "</Synchronized>\n");
                        if (disk->d_sync.ds_offset > 0)
                                sbuf_printf(sb, "%s<BytesSynced>%jd"
                                    "</BytesSynced>\n", indent,
                                    (intmax_t)disk->d_sync.ds_offset);
                }
                sbuf_printf(sb, "%s<SyncID>%u</SyncID>\n", indent,
                    disk->d_sync.ds_syncid);
                sbuf_printf(sb, "%s<GenID>%u</GenID>\n", indent,
                    disk->d_genid);
                sbuf_printf(sb, "%s<Flags>", indent);
                if (disk->d_flags == 0)
                        sbuf_cat(sb, "NONE");
                else {
                        int first = 1;

#define ADD_FLAG(flag, name)    do {                                    \
        if ((disk->d_flags & (flag)) != 0) {                            \
                if (!first)                                             \
                        sbuf_cat(sb, ", ");                             \
                else                                                    \
                        first = 0;                                      \
                sbuf_cat(sb, name);                                     \
        }                                                               \
} while (0)
                        ADD_FLAG(G_MIRROR_DISK_FLAG_DIRTY, "DIRTY");
                        ADD_FLAG(G_MIRROR_DISK_FLAG_HARDCODED, "HARDCODED");
                        ADD_FLAG(G_MIRROR_DISK_FLAG_INACTIVE, "INACTIVE");
                        ADD_FLAG(G_MIRROR_DISK_FLAG_SYNCHRONIZING,
                            "SYNCHRONIZING");
                        ADD_FLAG(G_MIRROR_DISK_FLAG_FORCE_SYNC, "FORCE_SYNC");
                        ADD_FLAG(G_MIRROR_DISK_FLAG_BROKEN, "BROKEN");
#undef  ADD_FLAG
                }
                sbuf_cat(sb, "</Flags>\n");
                sbuf_printf(sb, "%s<Priority>%u</Priority>\n", indent,
                    disk->d_priority);
                sbuf_printf(sb, "%s<State>%s</State>\n", indent,
                    g_mirror_disk_state2str(disk->d_state));
        } else {
                sbuf_printf(sb, "%s<Type>", indent);
                switch (sc->sc_type) {
                case G_MIRROR_TYPE_AUTOMATIC:
                        sbuf_cat(sb, "AUTOMATIC");
                        break;
                case G_MIRROR_TYPE_MANUAL:
                        sbuf_cat(sb, "MANUAL");
                        break;
                default:
                        sbuf_cat(sb, "UNKNOWN");
                        break;
                }
                sbuf_cat(sb, "</Type>\n");
                sbuf_printf(sb, "%s<ID>%u</ID>\n", indent, (u_int)sc->sc_id);
                sbuf_printf(sb, "%s<SyncID>%u</SyncID>\n", indent, sc->sc_syncid);
                sbuf_printf(sb, "%s<GenID>%u</GenID>\n", indent, sc->sc_genid);
                sbuf_printf(sb, "%s<Flags>", indent);
                if (sc->sc_flags == 0)
                        sbuf_cat(sb, "NONE");
                else {
                        int first = 1;

#define ADD_FLAG(flag, name)    do {                                    \
        if ((sc->sc_flags & (flag)) != 0) {                             \
                if (!first)                                             \
                        sbuf_cat(sb, ", ");                             \
                else                                                    \
                        first = 0;                                      \
                sbuf_cat(sb, name);                                     \
        }                                                               \
} while (0)
                        ADD_FLAG(G_MIRROR_DEVICE_FLAG_NOFAILSYNC, "NOFAILSYNC");
                        ADD_FLAG(G_MIRROR_DEVICE_FLAG_NOAUTOSYNC, "NOAUTOSYNC");
#undef  ADD_FLAG
                }
                sbuf_cat(sb, "</Flags>\n");
                sbuf_printf(sb, "%s<Slice>%u</Slice>\n", indent,
                    (u_int)sc->sc_slice);
                sbuf_printf(sb, "%s<Balance>%s</Balance>\n", indent,
                    balance_name(sc->sc_balance));
                sbuf_printf(sb, "%s<Components>%u</Components>\n", indent,
                    sc->sc_ndisks);
                sbuf_printf(sb, "%s<State>", indent);
                if (sc->sc_state == G_MIRROR_DEVICE_STATE_STARTING)
                        sbuf_printf(sb, "%s", "STARTING");
                else if (sc->sc_ndisks ==
                    g_mirror_ndisks(sc, G_MIRROR_DISK_STATE_ACTIVE))
                        sbuf_printf(sb, "%s", "COMPLETE");
                else
                        sbuf_printf(sb, "%s", "DEGRADED");
                sbuf_cat(sb, "</State>\n");
        }
}

static void
g_mirror_shutdown_post_sync(void *arg, int howto)
{
        struct g_class *mp;
        struct g_geom *gp, *gp2;
        struct g_mirror_softc *sc;
        int error;

        if ((howto & RB_NOSYNC) != 0)
                return;

        mp = arg;
        g_topology_lock();
        g_mirror_shutdown = 1;
        LIST_FOREACH_SAFE(gp, &mp->geom, geom, gp2) {
                if ((sc = gp->softc) == NULL)
                        continue;
                /* Skip synchronization geom. */
                if (gp == sc->sc_sync.ds_geom)
                        continue;
                g_topology_unlock();
                sx_xlock(&sc->sc_lock);
                g_mirror_idle(sc, -1);
                g_cancel_event(sc);
                error = g_mirror_destroy(sc, G_MIRROR_DESTROY_DELAYED);
                if (error != 0)
                        sx_xunlock(&sc->sc_lock);
                g_topology_lock();
        }
        g_topology_unlock();
}

static void
g_mirror_init(struct g_class *mp)
{

        g_mirror_post_sync = EVENTHANDLER_REGISTER(shutdown_post_sync,
            g_mirror_shutdown_post_sync, mp, SHUTDOWN_PRI_FIRST);
        if (g_mirror_post_sync == NULL)
                G_MIRROR_DEBUG(0, "Warning! Cannot register shutdown event.");
}

static void
g_mirror_fini(struct g_class *mp)
{

        if (g_mirror_post_sync != NULL)
                EVENTHANDLER_DEREGISTER(shutdown_post_sync, g_mirror_post_sync);
}

/*
 * Refresh the mirror device's metadata when gmirror encounters a newer
 * generation as the individual components are being added to the mirror set.
 */
static int
g_mirror_refresh_device(struct g_mirror_softc *sc, const struct g_provider *pp,
    const struct g_mirror_metadata *md)
{

        g_topology_assert_not();
        sx_assert(&sc->sc_lock, SX_XLOCKED);

        KASSERT(sc->sc_genid <= md->md_genid,
            ("%s: attempted to refresh from stale component %s (device %s) "
            "(%u < %u).", __func__, pp->name, sc->sc_name, md->md_genid,
            sc->sc_genid));

        if (sc->sc_genid > md->md_genid || (sc->sc_genid == md->md_genid &&
            sc->sc_syncid >= md->md_syncid))
                return (0);

        G_MIRROR_DEBUG(0, "Found newer version for device %s (genid: curr=%u "
            "new=%u; syncid: curr=%u new=%u; ndisks: curr=%u new=%u; "
            "provider=%s).", sc->sc_name, sc->sc_genid, md->md_genid,
            sc->sc_syncid, md->md_syncid, sc->sc_ndisks, md->md_all, pp->name);

        if (sc->sc_state != G_MIRROR_DEVICE_STATE_STARTING) {
                /* Probable data corruption detected */
                G_MIRROR_DEBUG(0, "Cannot refresh metadata in %s state "
                    "(device=%s genid=%u). A stale mirror device was launched.",
                    g_mirror_device_state2str(sc->sc_state), sc->sc_name,
                    sc->sc_genid);
                return (EINVAL);
        }

        /* Update softc */
        g_mirror_reinit_from_metadata(sc, md);

        G_MIRROR_DEBUG(1, "Refresh device %s (id=%u, state=%s) from disk %s "
            "(genid=%u syncid=%u md_all=%u).", sc->sc_name, md->md_mid,
            g_mirror_device_state2str(sc->sc_state), pp->name, md->md_genid,
            md->md_syncid, (unsigned)md->md_all);

        return (0);
}

DECLARE_GEOM_CLASS(g_mirror_class, g_mirror);
MODULE_VERSION(geom_mirror, 0);