/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2002 Poul-Henning Kamp
 * Copyright (c) 2002 Networks Associates Technology, Inc.
 * Copyright (c) 2013 The FreeBSD Foundation
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Poul-Henning Kamp
 * and NAI Labs, the Security Research Division of Network Associates, Inc.
 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
 * DARPA CHATS research program.
 *
 * Portions of this software were developed by Konstantin Belousov
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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.
 * 3. The names of the authors may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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/kernel.h>
#include <sys/malloc.h>
#include <sys/bio.h>
#include <sys/ktr.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/stack.h>
#include <sys/stdarg.h>
#include <sys/sysctl.h>
#include <sys/vmem.h>
#include <machine/stack.h>

#include <sys/errno.h>
#include <geom/geom.h>
#include <geom/geom_int.h>
#include <sys/devicestat.h>

#include <vm/uma.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_map.h>

#define KTR_GEOM_ENABLED \
    ((KTR_COMPILE & KTR_GEOM) != 0 && (ktr_mask & KTR_GEOM) != 0)

static int      g_io_transient_map_bio(struct bio *bp);

static struct g_bioq g_bio_run_down;
static struct g_bioq g_bio_run_up;

static u_long nomem_count;
static u_long pause_count;

/*
 * Pace is a hint that we've had some trouble recently allocating
 * bios, so we should back off trying to send I/O down the stack
 * a bit to let the problem resolve. When pacing, we also turn
 * off direct dispatch to also reduce memory pressure from I/Os
 * there, at the expxense of some added latency while the memory
 * pressures exist. See g_io_schedule_down() for more details
 * and limitations.
 */
static volatile u_int __read_mostly pace;

static uma_zone_t __read_mostly biozone;

#include <machine/atomic.h>

static void
g_bioq_lock(struct g_bioq *bq)
{

        mtx_lock(&bq->bio_queue_lock);
}

static void
g_bioq_unlock(struct g_bioq *bq)
{

        mtx_unlock(&bq->bio_queue_lock);
}

#if 0
static void
g_bioq_destroy(struct g_bioq *bq)
{

        mtx_destroy(&bq->bio_queue_lock);
}
#endif

static void
g_bioq_init(struct g_bioq *bq)
{

        TAILQ_INIT(&bq->bio_queue);
        mtx_init(&bq->bio_queue_lock, "bio queue", NULL, MTX_DEF);
}

static struct bio *
g_bioq_first(struct g_bioq *bq)
{
        struct bio *bp;

        bp = TAILQ_FIRST(&bq->bio_queue);
        if (bp != NULL) {
                KASSERT((bp->bio_flags & BIO_ONQUEUE),
                    ("Bio not on queue bp=%p target %p", bp, bq));
                bp->bio_flags &= ~BIO_ONQUEUE;
                TAILQ_REMOVE(&bq->bio_queue, bp, bio_queue);
                bq->bio_queue_length--;
        }
        return (bp);
}

struct bio *
g_new_bio(void)
{
        struct bio *bp;

        bp = uma_zalloc(biozone, M_NOWAIT | M_ZERO);
#ifdef KTR
        if (KTR_GEOM_ENABLED) {
                struct stack st;

                CTR1(KTR_GEOM, "g_new_bio(): %p", bp);
                stack_save(&st);
                CTRSTACK(KTR_GEOM, &st, 3);
        }
#endif
        return (bp);
}

struct bio *
g_alloc_bio(void)
{
        struct bio *bp;

        bp = uma_zalloc(biozone, M_WAITOK | M_ZERO);
#ifdef KTR
        if (KTR_GEOM_ENABLED) {
                struct stack st;

                CTR1(KTR_GEOM, "g_alloc_bio(): %p", bp);
                stack_save(&st);
                CTRSTACK(KTR_GEOM, &st, 3);
        }
#endif
        return (bp);
}

void
g_destroy_bio(struct bio *bp)
{
#ifdef KTR
        if (KTR_GEOM_ENABLED) {
                struct stack st;

                CTR1(KTR_GEOM, "g_destroy_bio(): %p", bp);
                stack_save(&st);
                CTRSTACK(KTR_GEOM, &st, 3);
        }
#endif
        uma_zfree(biozone, bp);
}

struct bio *
g_clone_bio(struct bio *bp)
{
        struct bio *bp2;

        bp2 = uma_zalloc(biozone, M_NOWAIT | M_ZERO);
        if (bp2 != NULL) {
                bp2->bio_parent = bp;
                bp2->bio_cmd = bp->bio_cmd;
                /*
                 *  BIO_ORDERED flag may be used by disk drivers to enforce
                 *  ordering restrictions, so this flag needs to be cloned.
                 *  BIO_UNMAPPED, BIO_VLIST, and BIO_SWAP should be inherited,
                 *  to properly indicate which way the buffer is passed.
                 *  Other bio flags are not suitable for cloning.
                 */
                bp2->bio_flags = bp->bio_flags &
                    (BIO_ORDERED | BIO_UNMAPPED | BIO_VLIST | BIO_SWAP);
                bp2->bio_length = bp->bio_length;
                bp2->bio_offset = bp->bio_offset;
                bp2->bio_data = bp->bio_data;
                bp2->bio_ma = bp->bio_ma;
                bp2->bio_ma_n = bp->bio_ma_n;
                bp2->bio_ma_offset = bp->bio_ma_offset;
                bp2->bio_attribute = bp->bio_attribute;
                if (bp->bio_cmd == BIO_ZONE)
                        bcopy(&bp->bio_zone, &bp2->bio_zone,
                            sizeof(bp->bio_zone));
#if defined(BUF_TRACKING) || defined(FULL_BUF_TRACKING)
                bp2->bio_track_bp = bp->bio_track_bp;
#endif
                bp->bio_children++;
        }
#ifdef KTR
        if (KTR_GEOM_ENABLED) {
                struct stack st;

                CTR2(KTR_GEOM, "g_clone_bio(%p): %p", bp, bp2);
                stack_save(&st);
                CTRSTACK(KTR_GEOM, &st, 3);
        }
#endif
        return(bp2);
}

struct bio *
g_duplicate_bio(struct bio *bp)
{
        struct bio *bp2;

        bp2 = uma_zalloc(biozone, M_WAITOK | M_ZERO);
        bp2->bio_flags = bp->bio_flags & (BIO_UNMAPPED | BIO_VLIST | BIO_SWAP);
        bp2->bio_parent = bp;
        bp2->bio_cmd = bp->bio_cmd;
        bp2->bio_length = bp->bio_length;
        bp2->bio_offset = bp->bio_offset;
        bp2->bio_data = bp->bio_data;
        bp2->bio_ma = bp->bio_ma;
        bp2->bio_ma_n = bp->bio_ma_n;
        bp2->bio_ma_offset = bp->bio_ma_offset;
        bp2->bio_attribute = bp->bio_attribute;
        bp->bio_children++;
#ifdef KTR
        if (KTR_GEOM_ENABLED) {
                struct stack st;

                CTR2(KTR_GEOM, "g_duplicate_bio(%p): %p", bp, bp2);
                stack_save(&st);
                CTRSTACK(KTR_GEOM, &st, 3);
        }
#endif
        return(bp2);
}

void
g_reset_bio(struct bio *bp)
{

        bzero(bp, sizeof(*bp));
}

void
g_io_init(void)
{

        g_bioq_init(&g_bio_run_down);
        g_bioq_init(&g_bio_run_up);
        biozone = uma_zcreate("g_bio", sizeof(struct bio),
            NULL, NULL,
            NULL, NULL,
            0, 0);
}

int
g_io_getattr(const char *attr, struct g_consumer *cp, int *len, void *ptr)
{
        struct bio *bp;
        int error;

        g_trace(G_T_BIO, "bio_getattr(%s)", attr);
        bp = g_alloc_bio();
        bp->bio_cmd = BIO_GETATTR;
        bp->bio_done = NULL;
        bp->bio_attribute = attr;
        bp->bio_length = *len;
        bp->bio_data = ptr;
        g_io_request(bp, cp);
        error = biowait(bp, "ggetattr");
        *len = bp->bio_completed;
        g_destroy_bio(bp);
        return (error);
}

int
g_io_zonecmd(struct disk_zone_args *zone_args, struct g_consumer *cp)
{
        struct bio *bp;
        int error;

        g_trace(G_T_BIO, "bio_zone(%d)", zone_args->zone_cmd);
        bp = g_alloc_bio();
        bp->bio_cmd = BIO_ZONE;
        bp->bio_done = NULL;
        /*
         * XXX KDM need to handle report zone data.
         */
        bcopy(zone_args, &bp->bio_zone, sizeof(*zone_args));
        if (zone_args->zone_cmd == DISK_ZONE_REPORT_ZONES)
                bp->bio_length =
                    zone_args->zone_params.report.entries_allocated *
                    sizeof(struct disk_zone_rep_entry);
        else
                bp->bio_length = 0;

        g_io_request(bp, cp);
        error = biowait(bp, "gzone");
        bcopy(&bp->bio_zone, zone_args, sizeof(*zone_args));
        g_destroy_bio(bp);
        return (error);
}

/*
 * Send a BIO_SPEEDUP down the stack. This is used to tell the lower layers that
 * the upper layers have detected a resource shortage. The lower layers are
 * advised to stop delaying I/O that they might be holding for performance
 * reasons and to schedule it (non-trims) or complete it successfully (trims) as
 * quickly as it can. bio_length is the amount of the shortage.  This call
 * should be non-blocking. bio_resid is used to communicate back if the lower
 * layers couldn't find bio_length worth of I/O to schedule or discard. A length
 * of 0 means to do as much as you can (schedule the h/w queues full, discard
 * all trims). flags are a hint from the upper layers to the lower layers what
 * operation should be done.
 */
int
g_io_speedup(off_t shortage, u_int flags, size_t *resid, struct g_consumer *cp)
{
        struct bio *bp;
        int error;

        KASSERT((flags & (BIO_SPEEDUP_TRIM | BIO_SPEEDUP_WRITE)) != 0,
            ("Invalid flags passed to g_io_speedup: %#x", flags));
        g_trace(G_T_BIO, "bio_speedup(%s, %jd, %#x)", cp->provider->name,
            (intmax_t)shortage, flags);
        bp = g_new_bio();
        if (bp == NULL)
                return (ENOMEM);
        bp->bio_cmd = BIO_SPEEDUP;
        bp->bio_length = shortage;
        bp->bio_done = NULL;
        bp->bio_flags |= flags;
        g_io_request(bp, cp);
        error = biowait(bp, "gflush");
        *resid = bp->bio_resid;
        g_destroy_bio(bp);
        return (error);
}

int
g_io_flush(struct g_consumer *cp)
{
        struct bio *bp;
        int error;

        g_trace(G_T_BIO, "bio_flush(%s)", cp->provider->name);
        bp = g_alloc_bio();
        bp->bio_cmd = BIO_FLUSH;
        bp->bio_flags |= BIO_ORDERED;
        bp->bio_done = NULL;
        bp->bio_attribute = NULL;
        bp->bio_offset = cp->provider->mediasize;
        bp->bio_length = 0;
        bp->bio_data = NULL;
        g_io_request(bp, cp);
        error = biowait(bp, "gflush");
        g_destroy_bio(bp);
        return (error);
}

static int
g_io_check(struct bio *bp)
{
        struct g_consumer *cp;
        struct g_provider *pp;
        off_t excess;
        int error;

        biotrack(bp, __func__);

        cp = bp->bio_from;
        pp = bp->bio_to;

        /* Fail if access counters dont allow the operation */
        switch(bp->bio_cmd) {
        case BIO_READ:
        case BIO_GETATTR:
                if (cp->acr == 0)
                        return (EPERM);
                break;
        case BIO_WRITE:
        case BIO_DELETE:
        case BIO_SPEEDUP:
        case BIO_FLUSH:
                if (cp->acw == 0)
                        return (EPERM);
                break;
        case BIO_ZONE:
                if ((bp->bio_zone.zone_cmd == DISK_ZONE_REPORT_ZONES) ||
                    (bp->bio_zone.zone_cmd == DISK_ZONE_GET_PARAMS)) {
                        if (cp->acr == 0)
                                return (EPERM);
                } else if (cp->acw == 0)
                        return (EPERM);
                break;
        default:
                return (EPERM);
        }
        /* if provider is marked for error, don't disturb. */
        if (pp->error)
                return (pp->error);
        if (cp->flags & G_CF_ORPHAN)
                return (ENXIO);

        switch(bp->bio_cmd) {
        case BIO_READ:
        case BIO_WRITE:
        case BIO_DELETE:
                /* Zero sectorsize or mediasize is probably a lack of media. */
                if (pp->sectorsize == 0 || pp->mediasize == 0)
                        return (ENXIO);
                /* Reject I/O not on sector boundary */
                if (bp->bio_offset % pp->sectorsize)
                        return (EINVAL);
                /* Reject I/O not integral sector long */
                if (bp->bio_length % pp->sectorsize)
                        return (EINVAL);
                /* Reject requests before or past the end of media. */
                if (bp->bio_offset < 0)
                        return (EIO);
                if (bp->bio_offset > pp->mediasize)
                        return (EIO);

                /* Truncate requests to the end of providers media. */
                excess = bp->bio_offset + bp->bio_length;
                if (excess > bp->bio_to->mediasize) {
                        KASSERT((bp->bio_flags & BIO_UNMAPPED) == 0 ||
                            round_page(bp->bio_ma_offset +
                            bp->bio_length) / PAGE_SIZE == bp->bio_ma_n,
                            ("excess bio %p too short", bp));
                        excess -= bp->bio_to->mediasize;
                        bp->bio_length -= excess;
                        if ((bp->bio_flags & BIO_UNMAPPED) != 0) {
                                bp->bio_ma_n = round_page(bp->bio_ma_offset +
                                    bp->bio_length) / PAGE_SIZE;
                        }
                        if (excess > 0)
                                CTR3(KTR_GEOM, "g_down truncated bio "
                                    "%p provider %s by %d", bp,
                                    bp->bio_to->name, excess);
                }

                /* Deliver zero length transfers right here. */
                if (bp->bio_length == 0) {
                        CTR2(KTR_GEOM, "g_down terminated 0-length "
                            "bp %p provider %s", bp, bp->bio_to->name);
                        return (0);
                }

                if ((bp->bio_flags & BIO_UNMAPPED) != 0 &&
                    (bp->bio_to->flags & G_PF_ACCEPT_UNMAPPED) == 0 &&
                    (bp->bio_cmd == BIO_READ || bp->bio_cmd == BIO_WRITE)) {
                        if ((error = g_io_transient_map_bio(bp)) >= 0)
                                return (error);
                }
                break;
        default:
                break;
        }
        return (EJUSTRETURN);
}

void
g_io_request(struct bio *bp, struct g_consumer *cp)
{
        struct g_provider *pp;
        int direct, error, first;
        uint8_t cmd;

        biotrack(bp, __func__);

        KASSERT(cp != NULL, ("NULL cp in g_io_request"));
        KASSERT(bp != NULL, ("NULL bp in g_io_request"));
        pp = cp->provider;
        KASSERT(pp != NULL, ("consumer not attached in g_io_request"));
#ifdef DIAGNOSTIC
        KASSERT(bp->bio_driver1 == NULL,
            ("bio_driver1 used by the consumer (geom %s)", cp->geom->name));
        KASSERT(bp->bio_driver2 == NULL,
            ("bio_driver2 used by the consumer (geom %s)", cp->geom->name));
        KASSERT(bp->bio_pflags == 0,
            ("bio_pflags used by the consumer (geom %s)", cp->geom->name));
        /*
         * Remember consumer's private fields, so we can detect if they were
         * modified by the provider.
         */
        bp->_bio_caller1 = bp->bio_caller1;
        bp->_bio_caller2 = bp->bio_caller2;
        bp->_bio_cflags = bp->bio_cflags;
#endif

        cmd = bp->bio_cmd;
        if (cmd == BIO_READ || cmd == BIO_WRITE || cmd == BIO_GETATTR) {
                KASSERT(bp->bio_data != NULL,
                    ("NULL bp->data in g_io_request(cmd=%hu)", bp->bio_cmd));
        }
        if (cmd == BIO_DELETE || cmd == BIO_FLUSH || cmd == BIO_SPEEDUP) {
                KASSERT(bp->bio_data == NULL,
                    ("non-NULL bp->data in g_io_request(cmd=%hu)",
                    bp->bio_cmd));
        }
        if (cmd == BIO_READ || cmd == BIO_WRITE || cmd == BIO_DELETE) {
                KASSERT(bp->bio_offset % cp->provider->sectorsize == 0,
                    ("wrong offset %jd for sectorsize %u",
                    bp->bio_offset, cp->provider->sectorsize));
                KASSERT(bp->bio_length % cp->provider->sectorsize == 0,
                    ("wrong length %jd for sectorsize %u",
                    bp->bio_length, cp->provider->sectorsize));
        }

        g_trace(G_T_BIO, "bio_request(%p) from %p(%s) to %p(%s) cmd %d",
            bp, cp, cp->geom->name, pp, pp->name, bp->bio_cmd);

        bp->bio_from = cp;
        bp->bio_to = pp;
        bp->bio_error = 0;
        bp->bio_completed = 0;

        KASSERT(!(bp->bio_flags & BIO_ONQUEUE),
            ("Bio already on queue bp=%p", bp));

        if ((g_collectstats & G_STATS_CONSUMERS) != 0 ||
            ((g_collectstats & G_STATS_PROVIDERS) != 0 && pp->stat != NULL))
                binuptime(&bp->bio_t0);
        else
                getbinuptime(&bp->bio_t0);
        if (g_collectstats & G_STATS_CONSUMERS)
                devstat_start_transaction_bio_t0(cp->stat, bp);
        if (g_collectstats & G_STATS_PROVIDERS)
                devstat_start_transaction_bio_t0(pp->stat, bp);
#ifdef INVARIANTS
        atomic_add_int(&cp->nstart, 1);
#endif

        direct = (cp->flags & G_CF_DIRECT_SEND) != 0 &&
            (pp->flags & G_PF_DIRECT_RECEIVE) != 0 &&
            curthread != g_down_td &&
            ((pp->flags & G_PF_ACCEPT_UNMAPPED) != 0 ||
            (bp->bio_flags & BIO_UNMAPPED) == 0 || THREAD_CAN_SLEEP()) &&
            pace == 0;
        if (direct) {
                /* Block direct execution if less then half of stack left. */
                size_t  st, su;
                GET_STACK_USAGE(st, su);
                if (su * 2 > st)
                        direct = 0;
        }

        if (direct) {
                error = g_io_check(bp);
                if (error >= 0) {
                        CTR3(KTR_GEOM, "g_io_request g_io_check on bp %p "
                            "provider %s returned %d", bp, bp->bio_to->name,
                            error);
                        g_io_deliver(bp, error);
                        return;
                }
                bp->bio_to->geom->start(bp);
        } else {
                g_bioq_lock(&g_bio_run_down);
                first = TAILQ_EMPTY(&g_bio_run_down.bio_queue);
                TAILQ_INSERT_TAIL(&g_bio_run_down.bio_queue, bp, bio_queue);
                bp->bio_flags |= BIO_ONQUEUE;
                g_bio_run_down.bio_queue_length++;
                g_bioq_unlock(&g_bio_run_down);
                /* Pass it on down. */
                if (first)
                        wakeup(&g_wait_down);
        }
}

void
g_io_deliver(struct bio *bp, int error)
{
        struct bintime now;
        struct g_consumer *cp;
        struct g_provider *pp;
        struct mtx *mtxp;
        int direct, first;

        biotrack(bp, __func__);

        KASSERT(bp != NULL, ("NULL bp in g_io_deliver"));
        pp = bp->bio_to;
        KASSERT(pp != NULL, ("NULL bio_to in g_io_deliver"));
        cp = bp->bio_from;
        if (cp == NULL) {
                bp->bio_error = error;
                bp->bio_done(bp);
                return;
        }
        KASSERT(cp != NULL, ("NULL bio_from in g_io_deliver"));
        KASSERT(cp->geom != NULL, ("NULL bio_from->geom in g_io_deliver"));
#ifdef DIAGNOSTIC
        /*
         * Some classes - GJournal in particular - can modify bio's
         * private fields while the bio is in transit; G_GEOM_VOLATILE_BIO
         * flag means it's an expected behaviour for that particular geom.
         */
        if ((cp->geom->flags & G_GEOM_VOLATILE_BIO) == 0) {
                KASSERT(bp->bio_caller1 == bp->_bio_caller1,
                    ("bio_caller1 used by the provider %s", pp->name));
                KASSERT(bp->bio_caller2 == bp->_bio_caller2,
                    ("bio_caller2 used by the provider %s", pp->name));
                KASSERT(bp->bio_cflags == bp->_bio_cflags,
                    ("bio_cflags used by the provider %s", pp->name));
        }
#endif
        KASSERT(bp->bio_completed >= 0, ("bio_completed can't be less than 0"));
        KASSERT(bp->bio_completed <= bp->bio_length,
            ("bio_completed can't be greater than bio_length"));

        g_trace(G_T_BIO,
"g_io_deliver(%p) from %p(%s) to %p(%s) cmd %d error %d off %jd len %jd",
            bp, cp, cp->geom->name, pp, pp->name, bp->bio_cmd, error,
            (intmax_t)bp->bio_offset, (intmax_t)bp->bio_length);

        KASSERT(!(bp->bio_flags & BIO_ONQUEUE),
            ("Bio already on queue bp=%p", bp));

        /*
         * XXX: next two doesn't belong here
         */
        bp->bio_bcount = bp->bio_length;
        bp->bio_resid = bp->bio_bcount - bp->bio_completed;

        direct = (pp->flags & G_PF_DIRECT_SEND) &&
                 (cp->flags & G_CF_DIRECT_RECEIVE) &&
                 curthread != g_up_td;
        if (direct) {
                /* Block direct execution if less then half of stack left. */
                size_t  st, su;
                GET_STACK_USAGE(st, su);
                if (su * 2 > st)
                        direct = 0;
        }

        /*
         * The statistics collection is lockless, as such, but we
         * can not update one instance of the statistics from more
         * than one thread at a time, so grab the lock first.
         */
        if ((g_collectstats & G_STATS_CONSUMERS) != 0 ||
            ((g_collectstats & G_STATS_PROVIDERS) != 0 && pp->stat != NULL))
                binuptime(&now);
        mtxp = mtx_pool_find(mtxpool_sleep, pp);
        mtx_lock(mtxp);
        if (g_collectstats & G_STATS_PROVIDERS)
                devstat_end_transaction_bio_bt(pp->stat, bp, &now);
        if (g_collectstats & G_STATS_CONSUMERS)
                devstat_end_transaction_bio_bt(cp->stat, bp, &now);
#ifdef INVARIANTS
        cp->nend++;
#endif
        mtx_unlock(mtxp);

        if (error != ENOMEM) {
                bp->bio_error = error;
                if (direct) {
                        biodone(bp);
                } else {
                        g_bioq_lock(&g_bio_run_up);
                        first = TAILQ_EMPTY(&g_bio_run_up.bio_queue);
                        TAILQ_INSERT_TAIL(&g_bio_run_up.bio_queue, bp, bio_queue);
                        bp->bio_flags |= BIO_ONQUEUE;
                        g_bio_run_up.bio_queue_length++;
                        g_bioq_unlock(&g_bio_run_up);
                        if (first)
                                wakeup(&g_wait_up);
                }
                return;
        }

        if (bootverbose)
                printf("ENOMEM %p on %p(%s)\n", bp, pp, pp->name);
        atomic_add_long(&nomem_count, 1);       /* Rare event, but no locks held */
        bp->bio_children = 0;
        bp->bio_inbed = 0;
        bp->bio_driver1 = NULL;
        bp->bio_driver2 = NULL;
        bp->bio_pflags = 0;
        g_io_request(bp, cp);
        pace = 1;
        return;
}

SYSCTL_DECL(_kern_geom);

static long transient_maps;
SYSCTL_LONG(_kern_geom, OID_AUTO, transient_maps, CTLFLAG_RD,
    &transient_maps, 0,
    "Total count of the transient mapping requests");
u_int transient_map_retries = 10;
SYSCTL_UINT(_kern_geom, OID_AUTO, transient_map_retries, CTLFLAG_RW,
    &transient_map_retries, 0,
    "Max count of retries used before giving up on creating transient map");
int transient_map_hard_failures;
SYSCTL_INT(_kern_geom, OID_AUTO, transient_map_hard_failures, CTLFLAG_RD,
    &transient_map_hard_failures, 0,
    "Failures to establish the transient mapping due to retry attempts "
    "exhausted");
int transient_map_soft_failures;
SYSCTL_INT(_kern_geom, OID_AUTO, transient_map_soft_failures, CTLFLAG_RD,
    &transient_map_soft_failures, 0,
    "Count of retried failures to establish the transient mapping");
int inflight_transient_maps;
SYSCTL_INT(_kern_geom, OID_AUTO, inflight_transient_maps, CTLFLAG_RD,
    &inflight_transient_maps, 0,
    "Current count of the active transient maps");
SYSCTL_ULONG(_kern_geom, OID_AUTO, nomem_count, CTLFLAG_RD,
    &nomem_count, 0,
    "Total count of requests completed with status of ENOMEM");
SYSCTL_ULONG(_kern_geom, OID_AUTO, pause_count, CTLFLAG_RD,
    &pause_count, 0,
    "Total count of requests stalled due to low memory in g_down");

static int
g_io_transient_map_bio(struct bio *bp)
{
        vm_offset_t addr;
        long size;
        u_int retried;

        KASSERT(unmapped_buf_allowed, ("unmapped disabled"));

        size = round_page(bp->bio_ma_offset + bp->bio_length);
        KASSERT(size / PAGE_SIZE == bp->bio_ma_n, ("Bio too short %p", bp));
        addr = 0;
        retried = 0;
        atomic_add_long(&transient_maps, 1);
retry:
        if (vmem_alloc(transient_arena, size, M_BESTFIT | M_NOWAIT, &addr)) {
                if (transient_map_retries != 0 &&
                    retried >= transient_map_retries) {
                        CTR2(KTR_GEOM, "g_down cannot map bp %p provider %s",
                            bp, bp->bio_to->name);
                        atomic_add_int(&transient_map_hard_failures, 1);
                        return (EDEADLK/* XXXKIB */);
                } else {
                        /*
                         * Naive attempt to quisce the I/O to get more
                         * in-flight requests completed and defragment
                         * the transient_arena.
                         */
                        CTR3(KTR_GEOM, "g_down retrymap bp %p provider %s r %d",
                            bp, bp->bio_to->name, retried);
                        pause("g_d_tra", hz / 10);
                        retried++;
                        atomic_add_int(&transient_map_soft_failures, 1);
                        goto retry;
                }
        }
        atomic_add_int(&inflight_transient_maps, 1);
        pmap_qenter((vm_offset_t)addr, bp->bio_ma, OFF_TO_IDX(size));
        bp->bio_data = (caddr_t)addr + bp->bio_ma_offset;
        bp->bio_flags |= BIO_TRANSIENT_MAPPING;
        bp->bio_flags &= ~BIO_UNMAPPED;
        return (EJUSTRETURN);
}

void
g_io_schedule_down(struct thread *tp __unused)
{
        struct bio *bp;
        int error;

        for(;;) {
                g_bioq_lock(&g_bio_run_down);
                bp = g_bioq_first(&g_bio_run_down);
                if (bp == NULL) {
                        CTR0(KTR_GEOM, "g_down going to sleep");
                        msleep(&g_wait_down, &g_bio_run_down.bio_queue_lock,
                            PRIBIO | PDROP, "-", 0);
                        continue;
                }
                CTR0(KTR_GEOM, "g_down has work to do");
                g_bioq_unlock(&g_bio_run_down);
                biotrack(bp, __func__);
                if (pace != 0) {
                        /*
                         * There has been at least one memory allocation failure
                         * since the last I/O completed. Pause 1ms to give the
                         * system a chance to free up memory. Pause time is not
                         * scaled to the number of I/O failures since they tend
                         * to cluster and the number is not predictive of how
                         * long a pause is needed.
                         *
                         * Older versions had a longer pause, which limited the
                         * IOPS to 10, which prolonged memory shortages that could
                         * be alleviated by I/O completing since it eliminated
                         * direct dispatch as well.
                         *
                         * XXX This pacing is really lame. It needs to be solved
                         * by other methods. This is OK only because the worst
                         * case scenario is so rare. In the worst case scenario
                         * all memory is tied up waiting for I/O to complete
                         * which can never happen since we can't allocate bios
                         * for that I/O.
                         */
                        CTR0(KTR_GEOM, "g_down pacing self");
                        pause_count++;          /* g_down has only one thread */
                        pause_sbt("g_down", SBT_1MS, 0, 0);
                        pace = 0;
                }
                CTR2(KTR_GEOM, "g_down processing bp %p provider %s", bp,
                    bp->bio_to->name);
                error = g_io_check(bp);
                if (error >= 0) {
                        CTR3(KTR_GEOM, "g_down g_io_check on bp %p provider "
                            "%s returned %d", bp, bp->bio_to->name, error);
                        g_io_deliver(bp, error);
                        continue;
                }
                THREAD_NO_SLEEPING();
                CTR4(KTR_GEOM, "g_down starting bp %p provider %s off %ld "
                    "len %ld", bp, bp->bio_to->name, bp->bio_offset,
                    bp->bio_length);
                bp->bio_to->geom->start(bp);
                THREAD_SLEEPING_OK();
        }
}

void
g_io_schedule_up(struct thread *tp __unused)
{
        struct bio *bp;

        for(;;) {
                g_bioq_lock(&g_bio_run_up);
                bp = g_bioq_first(&g_bio_run_up);
                if (bp == NULL) {
                        CTR0(KTR_GEOM, "g_up going to sleep");
                        msleep(&g_wait_up, &g_bio_run_up.bio_queue_lock,
                            PRIBIO | PDROP, "-", 0);
                        continue;
                }
                g_bioq_unlock(&g_bio_run_up);
                THREAD_NO_SLEEPING();
                CTR4(KTR_GEOM, "g_up biodone bp %p provider %s off "
                    "%jd len %ld", bp, bp->bio_to->name,
                    bp->bio_offset, bp->bio_length);
                biodone(bp);
                THREAD_SLEEPING_OK();
        }
}

void *
g_read_data(struct g_consumer *cp, off_t offset, off_t length, int *error)
{
        struct bio *bp;
        void *ptr;
        int errorc;

        KASSERT(length > 0 && length >= cp->provider->sectorsize &&
            length <= maxphys, ("g_read_data(): invalid length %jd",
            (intmax_t)length));

        bp = g_alloc_bio();
        bp->bio_cmd = BIO_READ;
        bp->bio_done = NULL;
        bp->bio_offset = offset;
        bp->bio_length = length;
        ptr = g_malloc(length, M_WAITOK);
        bp->bio_data = ptr;
        g_io_request(bp, cp);
        errorc = biowait(bp, "gread");
        if (errorc == 0 && bp->bio_completed != length)
                errorc = EIO;
        if (error != NULL)
                *error = errorc;
        g_destroy_bio(bp);
        if (errorc) {
                g_free(ptr);
                ptr = NULL;
        }
        return (ptr);
}

/*
 * A read function for use by ffs_sbget when used by GEOM-layer routines.
 */
int
g_use_g_read_data(void *devfd, off_t loc, void **bufp, int size)
{
        struct g_consumer *cp;

        KASSERT(*bufp == NULL,
            ("g_use_g_read_data: non-NULL *bufp %p\n", *bufp));

        cp = (struct g_consumer *)devfd;
        /*
         * Take care not to issue an invalid I/O request. The offset of
         * the superblock candidate must be multiples of the provider's
         * sector size, otherwise an FFS can't exist on the provider
         * anyway.
         */
        if (loc % cp->provider->sectorsize != 0)
                return (ENOENT);
        *bufp = g_read_data(cp, loc, size, NULL);
        if (*bufp == NULL)
                return (ENOENT);
        return (0);
}

int
g_write_data(struct g_consumer *cp, off_t offset, void *ptr, off_t length)
{
        struct bio *bp;
        int error;

        KASSERT(length > 0 && length >= cp->provider->sectorsize &&
            length <= maxphys, ("g_write_data(): invalid length %jd",
            (intmax_t)length));

        bp = g_alloc_bio();
        bp->bio_cmd = BIO_WRITE;
        bp->bio_done = NULL;
        bp->bio_offset = offset;
        bp->bio_length = length;
        bp->bio_data = ptr;
        g_io_request(bp, cp);
        error = biowait(bp, "gwrite");
        if (error == 0 && bp->bio_completed != length)
                error = EIO;
        g_destroy_bio(bp);
        return (error);
}

/*
 * A write function for use by ffs_sbput when used by GEOM-layer routines.
 */
int
g_use_g_write_data(void *devfd, off_t loc, void *buf, int size)
{

        return (g_write_data((struct g_consumer *)devfd, loc, buf, size));
}

int
g_delete_data(struct g_consumer *cp, off_t offset, off_t length)
{
        struct bio *bp;
        int error;

        KASSERT(length > 0 && length >= cp->provider->sectorsize,
            ("g_delete_data(): invalid length %jd", (intmax_t)length));

        bp = g_alloc_bio();
        bp->bio_cmd = BIO_DELETE;
        bp->bio_done = NULL;
        bp->bio_offset = offset;
        bp->bio_length = length;
        bp->bio_data = NULL;
        g_io_request(bp, cp);
        error = biowait(bp, "gdelete");
        if (error == 0 && bp->bio_completed != length)
                error = EIO;
        g_destroy_bio(bp);
        return (error);
}

void
g_print_bio(const char *prefix, const struct bio *bp, const char *fmtsuffix,
    ...)
{
#ifndef PRINTF_BUFR_SIZE
#define PRINTF_BUFR_SIZE 64
#endif
        char bufr[PRINTF_BUFR_SIZE];
        struct sbuf sb, *sbp __unused;
        va_list ap;

        sbp = sbuf_new(&sb, bufr, sizeof(bufr), SBUF_FIXEDLEN);
        KASSERT(sbp != NULL, ("sbuf_new misused?"));

        sbuf_set_drain(&sb, sbuf_printf_drain, NULL);

        sbuf_cat(&sb, prefix);
        g_format_bio(&sb, bp);

        va_start(ap, fmtsuffix);
        sbuf_vprintf(&sb, fmtsuffix, ap);
        va_end(ap);

        sbuf_nl_terminate(&sb);

        sbuf_finish(&sb);
        sbuf_delete(&sb);
}

void
g_format_bio(struct sbuf *sb, const struct bio *bp)
{
        const char *pname, *cmd = NULL;

        if (bp->bio_to != NULL)
                pname = bp->bio_to->name;
        else if (bp->bio_parent != NULL && bp->bio_parent->bio_to != NULL)
                pname = bp->bio_parent->bio_to->name;
        else
                pname = "[unknown]";

        switch (bp->bio_cmd) {
        case BIO_GETATTR:
                cmd = "GETATTR";
                sbuf_printf(sb, "%s[%s(attr=%s)]", pname, cmd,
                    bp->bio_attribute);
                return;
        case BIO_FLUSH:
                cmd = "FLUSH";
                sbuf_printf(sb, "%s[%s]", pname, cmd);
                return;
        case BIO_ZONE: {
                char *subcmd = NULL;
                cmd = "ZONE";
                switch (bp->bio_zone.zone_cmd) {
                case DISK_ZONE_OPEN:
                        subcmd = "OPEN";
                        break;
                case DISK_ZONE_CLOSE:
                        subcmd = "CLOSE";
                        break;
                case DISK_ZONE_FINISH:
                        subcmd = "FINISH";
                        break;
                case DISK_ZONE_RWP:
                        subcmd = "RWP";
                        break;
                case DISK_ZONE_REPORT_ZONES:
                        subcmd = "REPORT ZONES";
                        break;
                case DISK_ZONE_GET_PARAMS:
                        subcmd = "GET PARAMS";
                        break;
                default:
                        subcmd = "UNKNOWN";
                        break;
                }
                sbuf_printf(sb, "%s[%s,%s]", pname, cmd, subcmd);
                return;
        }
        case BIO_READ:
                cmd = "READ";
                break;
        case BIO_WRITE:
                cmd = "WRITE";
                break;
        case BIO_DELETE:
                cmd = "DELETE";
                break;
        default:
                cmd = "UNKNOWN";
                sbuf_printf(sb, "%s[%s()]", pname, cmd);
                return;
        }
        sbuf_printf(sb, "%s[%s(offset=%jd, length=%jd)]", pname, cmd,
            (intmax_t)bp->bio_offset, (intmax_t)bp->bio_length);
}