fs/zfs/dmu.c

	dmu.c revision 98579b20de8e05c5117968705a18979f8b75b863
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/dmu.h>
#include <sys/dmu_impl.h>
#include <sys/dmu_tx.h>
#include <sys/dbuf.h>
#include <sys/dnode.h>
#include <sys/zfs_context.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_traverse.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_synctask.h>
#include <sys/dmu_zfetch.h>
#include <sys/zfs_ioctl.h>
#include <sys/zap.h>
#include <sys/zio_checksum.h>

const dmu_object_type_info_t dmu_ot[DMU_OT_NUMTYPES] = {
    {   byteswap_uint8_array,   TRUE,   "unallocated"       },
    {   zap_byteswap,       TRUE,   "object directory"  },
    {   byteswap_uint64_array,  TRUE,   "object array"      },
    {   byteswap_uint8_array,   TRUE,   "packed nvlist"     },
    {   byteswap_uint64_array,  TRUE,   "packed nvlist size"    },
    {   byteswap_uint64_array,  TRUE,   "bplist"        },
    {   byteswap_uint64_array,  TRUE,   "bplist header"     },
    {   byteswap_uint64_array,  TRUE,   "SPA space map header"  },
    {   byteswap_uint64_array,  TRUE,   "SPA space map"     },
    {   byteswap_uint64_array,  TRUE,   "ZIL intent log"    },
    {   dnode_buf_byteswap, TRUE,   "DMU dnode"     },
    {   dmu_objset_byteswap,    TRUE,   "DMU objset"        },
    {   byteswap_uint64_array,  TRUE,   "DSL directory"     },
    {   zap_byteswap,       TRUE,   "DSL directory child map"},
    {   zap_byteswap,       TRUE,   "DSL dataset snap map"  },
    {   zap_byteswap,       TRUE,   "DSL props"     },
    {   byteswap_uint64_array,  TRUE,   "DSL dataset"       },
    {   zfs_znode_byteswap, TRUE,   "ZFS znode"     },
    {   zfs_acl_byteswap,   TRUE,   "ZFS ACL"       },
    {   byteswap_uint8_array,   FALSE,  "ZFS plain file"    },
    {   zap_byteswap,       TRUE,   "ZFS directory"     },
    {   zap_byteswap,       TRUE,   "ZFS master node"   },
    {   zap_byteswap,       TRUE,   "ZFS delete queue"  },
    {   byteswap_uint8_array,   FALSE,  "zvol object"       },
    {   zap_byteswap,       TRUE,   "zvol prop"     },
    {   byteswap_uint8_array,   FALSE,  "other uint8[]"     },
    {   byteswap_uint64_array,  FALSE,  "other uint64[]"    },
    {   zap_byteswap,       TRUE,   "other ZAP"     },
    {   zap_byteswap,       TRUE,   "persistent error log"  },
};

int
dmu_buf_hold(objset_t *os, uint64_t object, uint64_t offset,
    void *tag, dmu_buf_t **dbp)
{
    dnode_t *dn;
    uint64_t blkid;
    dmu_buf_impl_t *db;
    int err;

    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);
    blkid = dbuf_whichblock(dn, offset);
    rw_enter(&dn->dn_struct_rwlock, RW_READER);
    db = dbuf_hold(dn, blkid, tag);
    rw_exit(&dn->dn_struct_rwlock);
    if (db == NULL) {
        err = EIO;
    } else {
        err = dbuf_read(db, NULL, DB_RF_CANFAIL);
        if (err) {
            dbuf_rele(db, tag);
            db = NULL;
        }
    }

    dnode_rele(dn, FTAG);
    *dbp = &db->db;
    return (err);
}

int
dmu_bonus_max(void)
{
    return (DN_MAX_BONUSLEN);
}

/*
 * returns ENOENT, EIO, or 0.
 */
int
dmu_bonus_hold(objset_t *os, uint64_t object, void *tag, dmu_buf_t **dbp)
{
    dnode_t *dn;
    int err, count;
    dmu_buf_impl_t *db;

    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);

    rw_enter(&dn->dn_struct_rwlock, RW_READER);
    if (dn->dn_bonus == NULL) {
        rw_exit(&dn->dn_struct_rwlock);
        rw_enter(&dn->dn_struct_rwlock, RW_WRITER);
        if (dn->dn_bonus == NULL)
            dn->dn_bonus = dbuf_create_bonus(dn);
    }
    db = dn->dn_bonus;
    rw_exit(&dn->dn_struct_rwlock);
    mutex_enter(&db->db_mtx);
    count = refcount_add(&db->db_holds, tag);
    mutex_exit(&db->db_mtx);
    if (count == 1)
        dnode_add_ref(dn, db);
    dnode_rele(dn, FTAG);

    VERIFY(0 == dbuf_read(db, NULL, DB_RF_MUST_SUCCEED));

    *dbp = &db->db;
    return (0);
}

/*
 * Note: longer-term, we should modify all of the dmu_buf_*() interfaces
 * to take a held dnode rather than <os, object> -- the lookup is wasteful,
 * and can induce severe lock contention when writing to several files
 * whose dnodes are in the same block.
 */
static int
dmu_buf_hold_array_by_dnode(dnode_t *dn, uint64_t offset,
    uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
{
    dmu_buf_t **dbp;
    uint64_t blkid, nblks, i;
    uint32_t flags;
    int err;
    zio_t *zio;

    ASSERT(length <= DMU_MAX_ACCESS);

    flags = DB_RF_CANFAIL | DB_RF_NEVERWAIT;
    if (length > zfetch_array_rd_sz)
        flags |= DB_RF_NOPREFETCH;

    rw_enter(&dn->dn_struct_rwlock, RW_READER);
    if (dn->dn_datablkshift) {
        int blkshift = dn->dn_datablkshift;
        nblks = (P2ROUNDUP(offset+length, 1ULL<<blkshift) -
            P2ALIGN(offset, 1ULL<<blkshift)) >> blkshift;
    } else {
        ASSERT3U(offset + length, <=, dn->dn_datablksz);
        nblks = 1;
    }
    dbp = kmem_zalloc(sizeof (dmu_buf_t *) * nblks, KM_SLEEP);

    zio = zio_root(dn->dn_objset->os_spa, NULL, NULL, TRUE);
    blkid = dbuf_whichblock(dn, offset);
    for (i = 0; i < nblks; i++) {
        dmu_buf_impl_t *db = dbuf_hold(dn, blkid+i, tag);
        if (db == NULL) {
            rw_exit(&dn->dn_struct_rwlock);
            dmu_buf_rele_array(dbp, nblks, tag);
            zio_nowait(zio);
            return (EIO);
        }
        /* initiate async i/o */
        if (read) {
            rw_exit(&dn->dn_struct_rwlock);
            (void) dbuf_read(db, zio, flags);
            rw_enter(&dn->dn_struct_rwlock, RW_READER);
        }
        dbp[i] = &db->db;
    }
    rw_exit(&dn->dn_struct_rwlock);

    /* wait for async i/o */
    err = zio_wait(zio);
    if (err) {
        dmu_buf_rele_array(dbp, nblks, tag);
        return (err);
    }

    /* wait for other io to complete */
    if (read) {
        for (i = 0; i < nblks; i++) {
            dmu_buf_impl_t *db = (dmu_buf_impl_t *)dbp[i];
            mutex_enter(&db->db_mtx);
            while (db->db_state == DB_READ ||
                db->db_state == DB_FILL)
                cv_wait(&db->db_changed, &db->db_mtx);
            if (db->db_state == DB_UNCACHED)
                err = EIO;
            mutex_exit(&db->db_mtx);
            if (err) {
                dmu_buf_rele_array(dbp, nblks, tag);
                return (err);
            }
        }
    }

    *numbufsp = nblks;
    *dbpp = dbp;
    return (0);
}

int
dmu_buf_hold_array(objset_t *os, uint64_t object, uint64_t offset,
    uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
{
    dnode_t *dn;
    int err;

    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);

    err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
        numbufsp, dbpp);

    dnode_rele(dn, FTAG);

    return (err);
}

int
dmu_buf_hold_array_by_bonus(dmu_buf_t *db, uint64_t offset,
    uint64_t length, int read, void *tag, int *numbufsp, dmu_buf_t ***dbpp)
{
    dnode_t *dn = ((dmu_buf_impl_t *)db)->db_dnode;
    int err;

    err = dmu_buf_hold_array_by_dnode(dn, offset, length, read, tag,
        numbufsp, dbpp);

    return (err);
}

void
dmu_buf_rele_array(dmu_buf_t **dbp_fake, int numbufs, void *tag)
{
    int i;
    dmu_buf_impl_t **dbp = (dmu_buf_impl_t **)dbp_fake;

    if (numbufs == 0)
        return;

    for (i = 0; i < numbufs; i++) {
        if (dbp[i])
            dbuf_rele(dbp[i], tag);
    }

    kmem_free(dbp, sizeof (dmu_buf_t *) * numbufs);
}

void
dmu_prefetch(objset_t *os, uint64_t object, uint64_t offset, uint64_t len)
{
    dnode_t *dn;
    uint64_t blkid;
    int nblks, i, err;

    if (len == 0) {  /* they're interested in the bonus buffer */
        dn = os->os->os_meta_dnode;

        if (object == 0 || object >= DN_MAX_OBJECT)
            return;

        rw_enter(&dn->dn_struct_rwlock, RW_READER);
        blkid = dbuf_whichblock(dn, object * sizeof (dnode_phys_t));
        dbuf_prefetch(dn, blkid);
        rw_exit(&dn->dn_struct_rwlock);
        return;
    }

    /*
     * XXX - Note, if the dnode for the requested object is not
     * already cached, we will do a *synchronous* read in the
     * dnode_hold() call.  The same is true for any indirects.
     */
    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err != 0)
        return;

    rw_enter(&dn->dn_struct_rwlock, RW_READER);
    if (dn->dn_datablkshift) {
        int blkshift = dn->dn_datablkshift;
        nblks = (P2ROUNDUP(offset+len, 1<<blkshift) -
            P2ALIGN(offset, 1<<blkshift)) >> blkshift;
    } else {
        nblks = (offset < dn->dn_datablksz);
    }

    if (nblks != 0) {
        blkid = dbuf_whichblock(dn, offset);
        for (i = 0; i < nblks; i++)
            dbuf_prefetch(dn, blkid+i);
    }

    rw_exit(&dn->dn_struct_rwlock);

    dnode_rele(dn, FTAG);
}

int
dmu_free_range(objset_t *os, uint64_t object, uint64_t offset,
    uint64_t size, dmu_tx_t *tx)
{
    dnode_t *dn;
    int err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);
    ASSERT(offset < UINT64_MAX);
    ASSERT(size == -1ULL || size <= UINT64_MAX - offset);
    dnode_free_range(dn, offset, size, tx);
    dnode_rele(dn, FTAG);
    return (0);
}

int
dmu_read(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
    void *buf)
{
    dnode_t *dn;
    dmu_buf_t **dbp;
    int numbufs, i, err;

    /*
     * Deal with odd block sizes, where there can't be data past the
     * first block.
     */
    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);
    if (dn->dn_datablkshift == 0) {
        int newsz = offset > dn->dn_datablksz ? 0 :
            MIN(size, dn->dn_datablksz - offset);
        bzero((char *)buf + newsz, size - newsz);
        size = newsz;
    }
    dnode_rele(dn, FTAG);

    while (size > 0) {
        uint64_t mylen = MIN(size, DMU_MAX_ACCESS / 2);
        int err;

        /*
         * NB: we could do this block-at-a-time, but it's nice
         * to be reading in parallel.
         */
        err = dmu_buf_hold_array(os, object, offset, mylen,
            TRUE, FTAG, &numbufs, &dbp);
        if (err)
            return (err);

        for (i = 0; i < numbufs; i++) {
            int tocpy;
            int bufoff;
            dmu_buf_t *db = dbp[i];

            ASSERT(size > 0);

            bufoff = offset - db->db_offset;
            tocpy = (int)MIN(db->db_size - bufoff, size);

            bcopy((char *)db->db_data + bufoff, buf, tocpy);

            offset += tocpy;
            size -= tocpy;
            buf = (char *)buf + tocpy;
        }
        dmu_buf_rele_array(dbp, numbufs, FTAG);
    }
    return (0);
}

void
dmu_write(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
    const void *buf, dmu_tx_t *tx)
{
    dmu_buf_t **dbp;
    int numbufs, i;

    if (size == 0)
        return;

    VERIFY(0 == dmu_buf_hold_array(os, object, offset, size,
        FALSE, FTAG, &numbufs, &dbp));

    for (i = 0; i < numbufs; i++) {
        int tocpy;
        int bufoff;
        dmu_buf_t *db = dbp[i];

        ASSERT(size > 0);

        bufoff = offset - db->db_offset;
        tocpy = (int)MIN(db->db_size - bufoff, size);

        ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);

        if (tocpy == db->db_size)
            dmu_buf_will_fill(db, tx);
        else
            dmu_buf_will_dirty(db, tx);

        bcopy(buf, (char *)db->db_data + bufoff, tocpy);

        if (tocpy == db->db_size)
            dmu_buf_fill_done(db, tx);

        offset += tocpy;
        size -= tocpy;
        buf = (char *)buf + tocpy;
    }
    dmu_buf_rele_array(dbp, numbufs, FTAG);
}

#ifdef _KERNEL
int
dmu_write_uio(objset_t *os, uint64_t object, uint64_t offset, uint64_t size,
    uio_t *uio, dmu_tx_t *tx)
{
    dmu_buf_t **dbp;
    int numbufs, i;
    int err = 0;

    if (size == 0)
        return (0);

    err = dmu_buf_hold_array(os, object, offset, size,
        FALSE, FTAG, &numbufs, &dbp);
    if (err)
        return (err);

    for (i = 0; i < numbufs; i++) {
        int tocpy;
        int bufoff;
        dmu_buf_t *db = dbp[i];

        ASSERT(size > 0);

        bufoff = offset - db->db_offset;
        tocpy = (int)MIN(db->db_size - bufoff, size);

        ASSERT(i == 0 || i == numbufs-1 || tocpy == db->db_size);

        if (tocpy == db->db_size)
            dmu_buf_will_fill(db, tx);
        else
            dmu_buf_will_dirty(db, tx);

        /*
         * XXX uiomove could block forever (eg. nfs-backed
         * pages).  There needs to be a uiolockdown() function
         * to lock the pages in memory, so that uiomove won't
         * block.
         */
        err = uiomove((char *)db->db_data + bufoff, tocpy,
            UIO_WRITE, uio);

        if (tocpy == db->db_size)
            dmu_buf_fill_done(db, tx);

        if (err)
            break;

        offset += tocpy;
        size -= tocpy;
    }
    dmu_buf_rele_array(dbp, numbufs, FTAG);
    return (err);
}
#endif

/*
 * XXX move send/recv stuff to its own new file!
 */

struct backuparg {
    dmu_replay_record_t *drr;
    vnode_t *vp;
    objset_t *os;
    zio_cksum_t zc;
    int err;
};

static int
dump_bytes(struct backuparg *ba, void *buf, int len)
{
    ssize_t resid; /* have to get resid to get detailed errno */
    ASSERT3U(len % 8, ==, 0);

    fletcher_4_incremental_native(buf, len, &ba->zc);
    ba->err = vn_rdwr(UIO_WRITE, ba->vp,
        (caddr_t)buf, len,
        0, UIO_SYSSPACE, FAPPEND, RLIM64_INFINITY, CRED(), &resid);
    return (ba->err);
}

static int
dump_free(struct backuparg *ba, uint64_t object, uint64_t offset,
    uint64_t length)
{
    /* write a FREE record */
    bzero(ba->drr, sizeof (dmu_replay_record_t));
    ba->drr->drr_type = DRR_FREE;
    ba->drr->drr_u.drr_free.drr_object = object;
    ba->drr->drr_u.drr_free.drr_offset = offset;
    ba->drr->drr_u.drr_free.drr_length = length;

    if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
        return (EINTR);
    return (0);
}

static int
dump_data(struct backuparg *ba, dmu_object_type_t type,
    uint64_t object, uint64_t offset, int blksz, void *data)
{
    /* write a DATA record */
    bzero(ba->drr, sizeof (dmu_replay_record_t));
    ba->drr->drr_type = DRR_WRITE;
    ba->drr->drr_u.drr_write.drr_object = object;
    ba->drr->drr_u.drr_write.drr_type = type;
    ba->drr->drr_u.drr_write.drr_offset = offset;
    ba->drr->drr_u.drr_write.drr_length = blksz;

    if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
        return (EINTR);
    if (dump_bytes(ba, data, blksz))
        return (EINTR);
    return (0);
}

static int
dump_freeobjects(struct backuparg *ba, uint64_t firstobj, uint64_t numobjs)
{
    /* write a FREEOBJECTS record */
    bzero(ba->drr, sizeof (dmu_replay_record_t));
    ba->drr->drr_type = DRR_FREEOBJECTS;
    ba->drr->drr_u.drr_freeobjects.drr_firstobj = firstobj;
    ba->drr->drr_u.drr_freeobjects.drr_numobjs = numobjs;

    if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
        return (EINTR);
    return (0);
}

static int
dump_dnode(struct backuparg *ba, uint64_t object, dnode_phys_t *dnp)
{
    if (dnp == NULL || dnp->dn_type == DMU_OT_NONE)
        return (dump_freeobjects(ba, object, 1));

    /* write an OBJECT record */
    bzero(ba->drr, sizeof (dmu_replay_record_t));
    ba->drr->drr_type = DRR_OBJECT;
    ba->drr->drr_u.drr_object.drr_object = object;
    ba->drr->drr_u.drr_object.drr_type = dnp->dn_type;
    ba->drr->drr_u.drr_object.drr_bonustype = dnp->dn_bonustype;
    ba->drr->drr_u.drr_object.drr_blksz =
        dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT;
    ba->drr->drr_u.drr_object.drr_bonuslen = dnp->dn_bonuslen;
    ba->drr->drr_u.drr_object.drr_checksum = dnp->dn_checksum;
    ba->drr->drr_u.drr_object.drr_compress = dnp->dn_compress;

    if (dump_bytes(ba, ba->drr, sizeof (dmu_replay_record_t)))
        return (EINTR);

    if (dump_bytes(ba, DN_BONUS(dnp), P2ROUNDUP(dnp->dn_bonuslen, 8)))
        return (EINTR);

    /* free anything past the end of the file */
    if (dump_free(ba, object, (dnp->dn_maxblkid + 1) *
        (dnp->dn_datablkszsec << SPA_MINBLOCKSHIFT), -1ULL))
        return (EINTR);
    if (ba->err)
        return (EINTR);
    return (0);
}

#define BP_SPAN(dnp, level) \
    (((uint64_t)dnp->dn_datablkszsec) << (SPA_MINBLOCKSHIFT + \
    (level) * (dnp->dn_indblkshift - SPA_BLKPTRSHIFT)))

static int
backup_cb(traverse_blk_cache_t *bc, spa_t *spa, void *arg)
{
    struct backuparg *ba = arg;
    uint64_t object = bc->bc_bookmark.zb_object;
    int level = bc->bc_bookmark.zb_level;
    uint64_t blkid = bc->bc_bookmark.zb_blkid;
    blkptr_t *bp = bc->bc_blkptr.blk_birth ? &bc->bc_blkptr : NULL;
    dmu_object_type_t type = bp ? BP_GET_TYPE(bp) : DMU_OT_NONE;
    void *data = bc->bc_data;
    int err = 0;

    if (issig(JUSTLOOKING) && issig(FORREAL))
        return (EINTR);

    ASSERT(data || bp == NULL);

    if (bp == NULL && object == 0) {
        uint64_t span = BP_SPAN(bc->bc_dnode, level);
        uint64_t dnobj = (blkid * span) >> DNODE_SHIFT;
        err = dump_freeobjects(ba, dnobj, span >> DNODE_SHIFT);
    } else if (bp == NULL) {
        uint64_t span = BP_SPAN(bc->bc_dnode, level);
        err = dump_free(ba, object, blkid * span, span);
    } else if (data && level == 0 && type == DMU_OT_DNODE) {
        dnode_phys_t *blk = data;
        int i;
        int blksz = BP_GET_LSIZE(bp);

        for (i = 0; i < blksz >> DNODE_SHIFT; i++) {
            uint64_t dnobj =
                (blkid << (DNODE_BLOCK_SHIFT - DNODE_SHIFT)) + i;
            err = dump_dnode(ba, dnobj, blk+i);
            if (err)
                break;
        }
    } else if (level == 0 &&
        type != DMU_OT_DNODE && type != DMU_OT_OBJSET) {
        int blksz = BP_GET_LSIZE(bp);
        if (data == NULL) {
            uint32_t aflags = ARC_WAIT;
            arc_buf_t *abuf;
            zbookmark_t zb;

            zb.zb_objset = ba->os->os->os_dsl_dataset->ds_object;
            zb.zb_object = object;
            zb.zb_level = level;
            zb.zb_blkid = blkid;
            (void) arc_read(NULL, spa, bp,
                dmu_ot[type].ot_byteswap, arc_getbuf_func, &abuf,
                ZIO_PRIORITY_ASYNC_READ, ZIO_FLAG_MUSTSUCCEED,
                &aflags, &zb);

            if (abuf) {
                err = dump_data(ba, type, object, blkid * blksz,
                    blksz, abuf->b_data);
                (void) arc_buf_remove_ref(abuf, &abuf);
            }
        } else {
            err = dump_data(ba, type, object, blkid * blksz,
                blksz, data);
        }
    }

    ASSERT(err == 0 || err == EINTR);
    return (err);
}

int
dmu_sendbackup(objset_t *tosnap, objset_t *fromsnap, vnode_t *vp)
{
    dsl_dataset_t *ds = tosnap->os->os_dsl_dataset;
    dsl_dataset_t *fromds = fromsnap ? fromsnap->os->os_dsl_dataset : NULL;
    dmu_replay_record_t *drr;
    struct backuparg ba;
    int err;

    /* tosnap must be a snapshot */
    if (ds->ds_phys->ds_next_snap_obj == 0)
        return (EINVAL);

    /* fromsnap must be an earlier snapshot from the same fs as tosnap */
    if (fromds && (ds->ds_dir != fromds->ds_dir ||
        fromds->ds_phys->ds_creation_txg >=
        ds->ds_phys->ds_creation_txg))
        return (EXDEV);

    drr = kmem_zalloc(sizeof (dmu_replay_record_t), KM_SLEEP);
    drr->drr_type = DRR_BEGIN;
    drr->drr_u.drr_begin.drr_magic = DMU_BACKUP_MAGIC;
    drr->drr_u.drr_begin.drr_version = DMU_BACKUP_VERSION;
    drr->drr_u.drr_begin.drr_creation_time =
        ds->ds_phys->ds_creation_time;
    drr->drr_u.drr_begin.drr_type = tosnap->os->os_phys->os_type;
    drr->drr_u.drr_begin.drr_toguid = ds->ds_phys->ds_guid;
    if (fromds)
        drr->drr_u.drr_begin.drr_fromguid = fromds->ds_phys->ds_guid;
    dsl_dataset_name(ds, drr->drr_u.drr_begin.drr_toname);

    ba.drr = drr;
    ba.vp = vp;
    ba.os = tosnap;
    ZIO_SET_CHECKSUM(&ba.zc, 0, 0, 0, 0);

    if (dump_bytes(&ba, drr, sizeof (dmu_replay_record_t))) {
        kmem_free(drr, sizeof (dmu_replay_record_t));
        return (ba.err);
    }

    err = traverse_dsl_dataset(ds,
        fromds ? fromds->ds_phys->ds_creation_txg : 0,
        ADVANCE_PRE | ADVANCE_HOLES | ADVANCE_DATA | ADVANCE_NOLOCK,
        backup_cb, &ba);

    if (err) {
        if (err == EINTR && ba.err)
            err = ba.err;
        return (err);
    }

    bzero(drr, sizeof (dmu_replay_record_t));
    drr->drr_type = DRR_END;
    drr->drr_u.drr_end.drr_checksum = ba.zc;

    if (dump_bytes(&ba, drr, sizeof (dmu_replay_record_t)))
        return (ba.err);

    kmem_free(drr, sizeof (dmu_replay_record_t));

    return (0);
}

struct restorearg {
    int err;
    int byteswap;
    vnode_t *vp;
    char *buf;
    uint64_t voff;
    int buflen; /* number of valid bytes in buf */
    int bufoff; /* next offset to read */
    int bufsize; /* amount of memory allocated for buf */
    zio_cksum_t zc;
};

/* ARGSUSED */
static int
replay_incremental_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
    dsl_dataset_t *ds = arg1;
    struct drr_begin *drrb = arg2;
    const char *snapname;
    int err;
    uint64_t val;

    /* must already be a snapshot of this fs */
    if (ds->ds_phys->ds_prev_snap_obj == 0)
        return (ENODEV);

    /* most recent snapshot must match fromguid */
    if (ds->ds_prev->ds_phys->ds_guid != drrb->drr_fromguid)
        return (ENODEV);
    /* must not have any changes since most recent snapshot */
    if (ds->ds_phys->ds_bp.blk_birth >
        ds->ds_prev->ds_phys->ds_creation_txg)
        return (ETXTBSY);

    /* new snapshot name must not exist */
    snapname = strrchr(drrb->drr_toname, '@');
    if (snapname == NULL)
        return (EEXIST);

    snapname++;
    err = zap_lookup(ds->ds_dir->dd_pool->dp_meta_objset,
        ds->ds_phys->ds_snapnames_zapobj, snapname, 8, 1, &val);
    if (err == 0)
        return (EEXIST);
    if (err != ENOENT)
        return (err);

    return (0);
}

/* ARGSUSED */
static void
replay_incremental_sync(void *arg1, void *arg2, dmu_tx_t *tx)
{
    dsl_dataset_t *ds = arg1;
    dmu_buf_will_dirty(ds->ds_dbuf, tx);
    ds->ds_phys->ds_flags |= DS_FLAG_INCONSISTENT;
}

/* ARGSUSED */
static int
replay_full_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
    dsl_dir_t *dd = arg1;
    struct drr_begin *drrb = arg2;
    objset_t *mos = dd->dd_pool->dp_meta_objset;
    char *cp;
    uint64_t val;
    int err;

    cp = strchr(drrb->drr_toname, '@');
    *cp = '\0';
    err = zap_lookup(mos, dd->dd_phys->dd_child_dir_zapobj,
        strrchr(drrb->drr_toname, '/') + 1,
        sizeof (uint64_t), 1, &val);
    *cp = '@';

    if (err != ENOENT)
        return (err ? err : EEXIST);

    return (0);
}

static void
replay_full_sync(void *arg1, void *arg2, dmu_tx_t *tx)
{
    dsl_dir_t *dd = arg1;
    struct drr_begin *drrb = arg2;
    char *cp;
    dsl_dataset_t *ds;
    uint64_t dsobj;

    cp = strchr(drrb->drr_toname, '@');
    *cp = '\0';
    dsobj = dsl_dataset_create_sync(dd, strrchr(drrb->drr_toname, '/') + 1,
        NULL, tx);
    *cp = '@';

    VERIFY(0 == dsl_dataset_open_obj(dd->dd_pool, dsobj, NULL,
        DS_MODE_EXCLUSIVE, FTAG, &ds));

    (void) dmu_objset_create_impl(dsl_dataset_get_spa(ds),
        ds, drrb->drr_type, tx);

    dmu_buf_will_dirty(ds->ds_dbuf, tx);
    ds->ds_phys->ds_flags |= DS_FLAG_INCONSISTENT;

    dsl_dataset_close(ds, DS_MODE_EXCLUSIVE, FTAG);
}

static int
replay_end_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
    objset_t *os = arg1;
    struct drr_begin *drrb = arg2;
    char *snapname;

    /* XXX verify that drr_toname is in dd */

    snapname = strchr(drrb->drr_toname, '@');
    if (snapname == NULL)
        return (EINVAL);
    snapname++;

    return (dsl_dataset_snapshot_check(os, snapname, tx));
}

static void
replay_end_sync(void *arg1, void *arg2, dmu_tx_t *tx)
{
    objset_t *os = arg1;
    struct drr_begin *drrb = arg2;
    char *snapname;
    dsl_dataset_t *ds, *hds;

    snapname = strchr(drrb->drr_toname, '@') + 1;

    dsl_dataset_snapshot_sync(os, snapname, tx);

    /* set snapshot's creation time and guid */
    hds = os->os->os_dsl_dataset;
    VERIFY(0 == dsl_dataset_open_obj(hds->ds_dir->dd_pool,
        hds->ds_phys->ds_prev_snap_obj, NULL,
        DS_MODE_PRIMARY | DS_MODE_READONLY | DS_MODE_INCONSISTENT,
        FTAG, &ds));

    dmu_buf_will_dirty(ds->ds_dbuf, tx);
    ds->ds_phys->ds_creation_time = drrb->drr_creation_time;
    ds->ds_phys->ds_guid = drrb->drr_toguid;
    ds->ds_phys->ds_flags &= ~DS_FLAG_INCONSISTENT;

    dsl_dataset_close(ds, DS_MODE_PRIMARY, FTAG);

    dmu_buf_will_dirty(hds->ds_dbuf, tx);
    hds->ds_phys->ds_flags &= ~DS_FLAG_INCONSISTENT;
}

void *
restore_read(struct restorearg *ra, int len)
{
    void *rv;

    /* some things will require 8-byte alignment, so everything must */
    ASSERT3U(len % 8, ==, 0);

    while (ra->buflen - ra->bufoff < len) {
        ssize_t resid;
        int leftover = ra->buflen - ra->bufoff;

        (void) memmove(ra->buf, ra->buf + ra->bufoff, leftover);
        ra->err = vn_rdwr(UIO_READ, ra->vp,
            (caddr_t)ra->buf + leftover, ra->bufsize - leftover,
            ra->voff, UIO_SYSSPACE, FAPPEND,
            RLIM64_INFINITY, CRED(), &resid);

        ra->voff += ra->bufsize - leftover - resid;
        ra->buflen = ra->bufsize - resid;
        ra->bufoff = 0;
        if (resid == ra->bufsize - leftover)
            ra->err = EINVAL;
        if (ra->err)
            return (NULL);
        /* Could compute checksum here? */
    }

    ASSERT3U(ra->bufoff % 8, ==, 0);
    ASSERT3U(ra->buflen - ra->bufoff, >=, len);
    rv = ra->buf + ra->bufoff;
    ra->bufoff += len;
    if (ra->byteswap)
        fletcher_4_incremental_byteswap(rv, len, &ra->zc);
    else
        fletcher_4_incremental_native(rv, len, &ra->zc);
    return (rv);
}

static void
backup_byteswap(dmu_replay_record_t *drr)
{
#define DO64(X) (drr->drr_u.X = BSWAP_64(drr->drr_u.X))
#define DO32(X) (drr->drr_u.X = BSWAP_32(drr->drr_u.X))
    drr->drr_type = BSWAP_32(drr->drr_type);
    switch (drr->drr_type) {
    case DRR_BEGIN:
        DO64(drr_begin.drr_magic);
        DO64(drr_begin.drr_version);
        DO64(drr_begin.drr_creation_time);
        DO32(drr_begin.drr_type);
        DO64(drr_begin.drr_toguid);
        DO64(drr_begin.drr_fromguid);
        break;
    case DRR_OBJECT:
        DO64(drr_object.drr_object);
        /* DO64(drr_object.drr_allocation_txg); */
        DO32(drr_object.drr_type);
        DO32(drr_object.drr_bonustype);
        DO32(drr_object.drr_blksz);
        DO32(drr_object.drr_bonuslen);
        break;
    case DRR_FREEOBJECTS:
        DO64(drr_freeobjects.drr_firstobj);
        DO64(drr_freeobjects.drr_numobjs);
        break;
    case DRR_WRITE:
        DO64(drr_write.drr_object);
        DO32(drr_write.drr_type);
        DO64(drr_write.drr_offset);
        DO64(drr_write.drr_length);
        break;
    case DRR_FREE:
        DO64(drr_free.drr_object);
        DO64(drr_free.drr_offset);
        DO64(drr_free.drr_length);
        break;
    case DRR_END:
        DO64(drr_end.drr_checksum.zc_word[0]);
        DO64(drr_end.drr_checksum.zc_word[1]);
        DO64(drr_end.drr_checksum.zc_word[2]);
        DO64(drr_end.drr_checksum.zc_word[3]);
        break;
    }
#undef DO64
#undef DO32
}

static int
restore_object(struct restorearg *ra, objset_t *os, struct drr_object *drro)
{
    int err;
    dmu_tx_t *tx;

    err = dmu_object_info(os, drro->drr_object, NULL);

    if (err != 0 && err != ENOENT)
        return (EINVAL);

    if (drro->drr_type == DMU_OT_NONE ||
        drro->drr_type >= DMU_OT_NUMTYPES ||
        drro->drr_bonustype >= DMU_OT_NUMTYPES ||
        drro->drr_checksum >= ZIO_CHECKSUM_FUNCTIONS ||
        drro->drr_compress >= ZIO_COMPRESS_FUNCTIONS ||
        P2PHASE(drro->drr_blksz, SPA_MINBLOCKSIZE) ||
        drro->drr_blksz < SPA_MINBLOCKSIZE ||
        drro->drr_blksz > SPA_MAXBLOCKSIZE ||
        drro->drr_bonuslen > DN_MAX_BONUSLEN) {
        return (EINVAL);
    }

    tx = dmu_tx_create(os);

    if (err == ENOENT) {
        /* currently free, want to be allocated */
        dmu_tx_hold_bonus(tx, DMU_NEW_OBJECT);
        dmu_tx_hold_write(tx, DMU_NEW_OBJECT, 0, 1);
        err = dmu_tx_assign(tx, TXG_WAIT);
        if (err) {
            dmu_tx_abort(tx);
            return (err);
        }
        err = dmu_object_claim(os, drro->drr_object,
            drro->drr_type, drro->drr_blksz,
            drro->drr_bonustype, drro->drr_bonuslen, tx);
    } else {
        /* currently allocated, want to be allocated */
        dmu_tx_hold_bonus(tx, drro->drr_object);
        /*
         * We may change blocksize, so need to
         * hold_write
         */
        dmu_tx_hold_write(tx, drro->drr_object, 0, 1);
        err = dmu_tx_assign(tx, TXG_WAIT);
        if (err) {
            dmu_tx_abort(tx);
            return (err);
        }

        err = dmu_object_reclaim(os, drro->drr_object,
            drro->drr_type, drro->drr_blksz,
            drro->drr_bonustype, drro->drr_bonuslen, tx);
    }
    if (err) {
        dmu_tx_commit(tx);
        return (EINVAL);
    }

    dmu_object_set_checksum(os, drro->drr_object, drro->drr_checksum, tx);
    dmu_object_set_compress(os, drro->drr_object, drro->drr_compress, tx);

    if (drro->drr_bonuslen) {
        dmu_buf_t *db;
        void *data;
        VERIFY(0 == dmu_bonus_hold(os, drro->drr_object, FTAG, &db));
        dmu_buf_will_dirty(db, tx);

        ASSERT3U(db->db_size, ==, drro->drr_bonuslen);
        data = restore_read(ra, P2ROUNDUP(db->db_size, 8));
        if (data == NULL) {
            dmu_tx_commit(tx);
            return (ra->err);
        }
        bcopy(data, db->db_data, db->db_size);
        if (ra->byteswap) {
            dmu_ot[drro->drr_bonustype].ot_byteswap(db->db_data,
                drro->drr_bonuslen);
        }
        dmu_buf_rele(db, FTAG);
    }
    dmu_tx_commit(tx);
    return (0);
}

/* ARGSUSED */
static int
restore_freeobjects(struct restorearg *ra, objset_t *os,
    struct drr_freeobjects *drrfo)
{
    uint64_t obj;

    if (drrfo->drr_firstobj + drrfo->drr_numobjs < drrfo->drr_firstobj)
        return (EINVAL);

    for (obj = drrfo->drr_firstobj;
        obj < drrfo->drr_firstobj + drrfo->drr_numobjs; obj++) {
        dmu_tx_t *tx;
        int err;

        if (dmu_object_info(os, obj, NULL) != 0)
            continue;

        tx = dmu_tx_create(os);
        dmu_tx_hold_bonus(tx, obj);
        err = dmu_tx_assign(tx, TXG_WAIT);
        if (err) {
            dmu_tx_abort(tx);
            return (err);
        }
        err = dmu_object_free(os, obj, tx);
        dmu_tx_commit(tx);
        if (err && err != ENOENT)
            return (EINVAL);
    }
    return (0);
}

static int
restore_write(struct restorearg *ra, objset_t *os,
    struct drr_write *drrw)
{
    dmu_tx_t *tx;
    void *data;
    int err;

    if (drrw->drr_offset + drrw->drr_length < drrw->drr_offset ||
        drrw->drr_type >= DMU_OT_NUMTYPES)
        return (EINVAL);

    data = restore_read(ra, drrw->drr_length);
    if (data == NULL)
        return (ra->err);

    if (dmu_object_info(os, drrw->drr_object, NULL) != 0)
        return (EINVAL);

    tx = dmu_tx_create(os);

    dmu_tx_hold_write(tx, drrw->drr_object,
        drrw->drr_offset, drrw->drr_length);
    err = dmu_tx_assign(tx, TXG_WAIT);
    if (err) {
        dmu_tx_abort(tx);
        return (err);
    }
    if (ra->byteswap)
        dmu_ot[drrw->drr_type].ot_byteswap(data, drrw->drr_length);
    dmu_write(os, drrw->drr_object,
        drrw->drr_offset, drrw->drr_length, data, tx);
    dmu_tx_commit(tx);
    return (0);
}

/* ARGSUSED */
static int
restore_free(struct restorearg *ra, objset_t *os,
    struct drr_free *drrf)
{
    dmu_tx_t *tx;
    int err;

    if (drrf->drr_length != -1ULL &&
        drrf->drr_offset + drrf->drr_length < drrf->drr_offset)
        return (EINVAL);

    if (dmu_object_info(os, drrf->drr_object, NULL) != 0)
        return (EINVAL);

    tx = dmu_tx_create(os);

    dmu_tx_hold_free(tx, drrf->drr_object,
        drrf->drr_offset, drrf->drr_length);
    err = dmu_tx_assign(tx, TXG_WAIT);
    if (err) {
        dmu_tx_abort(tx);
        return (err);
    }
    err = dmu_free_range(os, drrf->drr_object,
        drrf->drr_offset, drrf->drr_length, tx);
    dmu_tx_commit(tx);
    return (err);
}

int
dmu_recvbackup(char *tosnap, struct drr_begin *drrb, uint64_t *sizep,
    boolean_t force, vnode_t *vp, uint64_t voffset)
{
    struct restorearg ra;
    dmu_replay_record_t *drr;
    char *cp;
    objset_t *os = NULL;
    zio_cksum_t pzc;

    bzero(&ra, sizeof (ra));
    ra.vp = vp;
    ra.voff = voffset;
    ra.bufsize = 1<<20;
    ra.buf = kmem_alloc(ra.bufsize, KM_SLEEP);

    if (drrb->drr_magic == DMU_BACKUP_MAGIC) {
        ra.byteswap = FALSE;
    } else if (drrb->drr_magic == BSWAP_64(DMU_BACKUP_MAGIC)) {
        ra.byteswap = TRUE;
    } else {
        ra.err = EINVAL;
        goto out;
    }

    /*
     * NB: this assumes that struct drr_begin will be the largest in
     * dmu_replay_record_t's drr_u, and thus we don't need to pad it
     * with zeros to make it the same length as we wrote out.
     */
    ((dmu_replay_record_t *)ra.buf)->drr_type = DRR_BEGIN;
    ((dmu_replay_record_t *)ra.buf)->drr_pad = 0;
    ((dmu_replay_record_t *)ra.buf)->drr_u.drr_begin = *drrb;
    if (ra.byteswap) {
        fletcher_4_incremental_byteswap(ra.buf,
            sizeof (dmu_replay_record_t), &ra.zc);
    } else {
        fletcher_4_incremental_native(ra.buf,
            sizeof (dmu_replay_record_t), &ra.zc);
    }
    (void) strcpy(drrb->drr_toname, tosnap); /* for the sync funcs */

    if (ra.byteswap) {
        drrb->drr_magic = BSWAP_64(drrb->drr_magic);
        drrb->drr_version = BSWAP_64(drrb->drr_version);
        drrb->drr_creation_time = BSWAP_64(drrb->drr_creation_time);
        drrb->drr_type = BSWAP_32(drrb->drr_type);
        drrb->drr_toguid = BSWAP_64(drrb->drr_toguid);
        drrb->drr_fromguid = BSWAP_64(drrb->drr_fromguid);
    }

    ASSERT3U(drrb->drr_magic, ==, DMU_BACKUP_MAGIC);

    if (drrb->drr_version != DMU_BACKUP_VERSION ||
        drrb->drr_type >= DMU_OST_NUMTYPES ||
        strchr(drrb->drr_toname, '@') == NULL) {
        ra.err = EINVAL;
        goto out;
    }

    /*
     * Process the begin in syncing context.
     */
    if (drrb->drr_fromguid) {
        /* incremental backup */
        dsl_dataset_t *ds = NULL;

        cp = strchr(tosnap, '@');
        *cp = '\0';
        ra.err = dsl_dataset_open(tosnap, DS_MODE_EXCLUSIVE, FTAG, &ds);
        *cp = '@';
        if (ra.err)
            goto out;

        /*
         * Only do the rollback if the most recent snapshot
         * matches the incremental source
         */
        if (force) {
            if (ds->ds_prev->ds_phys->ds_guid !=
                drrb->drr_fromguid) {
                dsl_dataset_close(ds, DS_MODE_EXCLUSIVE, FTAG);
                return (ENODEV);
            }
            (void) dsl_dataset_rollback(ds);
        }
        ra.err = dsl_sync_task_do(ds->ds_dir->dd_pool,
            replay_incremental_check, replay_incremental_sync,
            ds, drrb, 1);
        dsl_dataset_close(ds, DS_MODE_EXCLUSIVE, FTAG);
    } else {
        /* full backup */
        dsl_dir_t *dd = NULL;
        const char *tail;

        /* can't restore full backup into topmost fs, for now */
        if (strrchr(drrb->drr_toname, '/') == NULL) {
            ra.err = EINVAL;
            goto out;
        }

        cp = strchr(tosnap, '@');
        *cp = '\0';
        ra.err = dsl_dir_open(tosnap, FTAG, &dd, &tail);
        *cp = '@';
        if (ra.err)
            goto out;
        if (tail == NULL) {
            ra.err = EEXIST;
            goto out;
        }

        ra.err = dsl_sync_task_do(dd->dd_pool, replay_full_check,
            replay_full_sync, dd, drrb, 5);
        dsl_dir_close(dd, FTAG);
    }
    if (ra.err)
        goto out;

    /*
     * Open the objset we are modifying.
     */

    cp = strchr(tosnap, '@');
    *cp = '\0';
    ra.err = dmu_objset_open(tosnap, DMU_OST_ANY,
        DS_MODE_PRIMARY | DS_MODE_INCONSISTENT, &os);
    *cp = '@';
    ASSERT3U(ra.err, ==, 0);

    /*
     * Read records and process them.
     */
    pzc = ra.zc;
    while (ra.err == 0 &&
        NULL != (drr = restore_read(&ra, sizeof (*drr)))) {
        if (issig(JUSTLOOKING) && issig(FORREAL)) {
            ra.err = EINTR;
            goto out;
        }

        if (ra.byteswap)
            backup_byteswap(drr);

        switch (drr->drr_type) {
        case DRR_OBJECT:
        {
            /*
             * We need to make a copy of the record header,
             * because restore_{object,write} may need to
             * restore_read(), which will invalidate drr.
             */
            struct drr_object drro = drr->drr_u.drr_object;
            ra.err = restore_object(&ra, os, &drro);
            break;
        }
        case DRR_FREEOBJECTS:
        {
            struct drr_freeobjects drrfo =
                drr->drr_u.drr_freeobjects;
            ra.err = restore_freeobjects(&ra, os, &drrfo);
            break;
        }
        case DRR_WRITE:
        {
            struct drr_write drrw = drr->drr_u.drr_write;
            ra.err = restore_write(&ra, os, &drrw);
            break;
        }
        case DRR_FREE:
        {
            struct drr_free drrf = drr->drr_u.drr_free;
            ra.err = restore_free(&ra, os, &drrf);
            break;
        }
        case DRR_END:
        {
            struct drr_end drre = drr->drr_u.drr_end;
            /*
             * We compare against the *previous* checksum
             * value, because the stored checksum is of
             * everything before the DRR_END record.
             */
            if (drre.drr_checksum.zc_word[0] != 0 &&
                ((drre.drr_checksum.zc_word[0] - pzc.zc_word[0]) |
                (drre.drr_checksum.zc_word[1] - pzc.zc_word[1]) |
                (drre.drr_checksum.zc_word[2] - pzc.zc_word[2]) |
                (drre.drr_checksum.zc_word[3] - pzc.zc_word[3]))) {
                ra.err = ECKSUM;
                goto out;
            }

            ra.err = dsl_sync_task_do(dmu_objset_ds(os)->
                ds_dir->dd_pool, replay_end_check, replay_end_sync,
                os, drrb, 3);
            goto out;
        }
        default:
            ra.err = EINVAL;
            goto out;
        }
        pzc = ra.zc;
    }

out:
    if (os)
        dmu_objset_close(os);

    /*
     * Make sure we don't rollback/destroy unless we actually
     * processed the begin properly.  'os' will only be set if this
     * is the case.
     */
    if (ra.err && os && tosnap && strchr(tosnap, '@')) {
        /*
         * rollback or destroy what we created, so we don't
         * leave it in the restoring state.
         */
        dsl_dataset_t *ds;
        int err;

        cp = strchr(tosnap, '@');
        *cp = '\0';
        err = dsl_dataset_open(tosnap,
            DS_MODE_EXCLUSIVE | DS_MODE_INCONSISTENT,
            FTAG, &ds);
        if (err == 0) {
            txg_wait_synced(ds->ds_dir->dd_pool, 0);
            if (drrb->drr_fromguid) {
                /* incremental: rollback to most recent snap */
                (void) dsl_dataset_rollback(ds);
                dsl_dataset_close(ds, DS_MODE_EXCLUSIVE, FTAG);
            } else {
                /* full: destroy whole fs */
                dsl_dataset_close(ds, DS_MODE_EXCLUSIVE, FTAG);
                (void) dsl_dataset_destroy(tosnap);
            }
        }
        *cp = '@';
    }

    kmem_free(ra.buf, ra.bufsize);
    if (sizep)
        *sizep = ra.voff;
    return (ra.err);
}

typedef struct {
    uint64_t    txg;
    dmu_buf_impl_t  *db;
    dmu_sync_cb_t   *done;
    void        *arg;
} dmu_sync_cbin_t;

typedef union {
    dmu_sync_cbin_t data;
    blkptr_t    blk;
} dmu_sync_cbarg_t;

/* ARGSUSED */
static void
dmu_sync_done(zio_t *zio, arc_buf_t *buf, void *varg)
{
    dmu_sync_cbin_t *in = (dmu_sync_cbin_t *)varg;
    dmu_buf_impl_t *db = in->db;
    uint64_t txg = in->txg;
    dmu_sync_cb_t *done = in->done;
    void *arg = in->arg;
    blkptr_t *blk = (blkptr_t *)varg;

    if (!BP_IS_HOLE(zio->io_bp)) {
        zio->io_bp->blk_fill = 1;
        BP_SET_TYPE(zio->io_bp, db->db_dnode->dn_type);
        BP_SET_LEVEL(zio->io_bp, 0);
    }

    *blk = *zio->io_bp; /* structure assignment */

    mutex_enter(&db->db_mtx);
    ASSERT(db->db_d.db_overridden_by[txg&TXG_MASK] == IN_DMU_SYNC);
    db->db_d.db_overridden_by[txg&TXG_MASK] = blk;
    cv_broadcast(&db->db_changed);
    mutex_exit(&db->db_mtx);

    if (done)
        done(&(db->db), arg);
}

/*
 * Intent log support: sync the block associated with db to disk.
 * N.B. and XXX: the caller is responsible for making sure that the
 * data isn't changing while dmu_sync() is writing it.
 *
 * Return values:
 *
 *  EEXIST: this txg has already been synced, so there's nothing to to.
 *      The caller should not log the write.
 *
 *  ENOENT: the block was dbuf_free_range()'d, so there's nothing to do.
 *      The caller should not log the write.
 *
 *  EALREADY: this block is already in the process of being synced.
 *      The caller should track its progress (somehow).
 *
 *  EINPROGRESS: the IO has been initiated.
 *      The caller should log this blkptr in the callback.
 *
 *  0: completed.  Sets *bp to the blkptr just written.
 *      The caller should log this blkptr immediately.
 */
int
dmu_sync(zio_t *pio, dmu_buf_t *db_fake,
    blkptr_t *bp, uint64_t txg, dmu_sync_cb_t *done, void *arg)
{
    dmu_buf_impl_t *db = (dmu_buf_impl_t *)db_fake;
    objset_impl_t *os = db->db_objset;
    dsl_pool_t *dp = os->os_dsl_dataset->ds_dir->dd_pool;
    tx_state_t *tx = &dp->dp_tx;
    dmu_sync_cbin_t *in;
    blkptr_t *blk;
    zbookmark_t zb;
    uint32_t arc_flag;
    int err;

    ASSERT(BP_IS_HOLE(bp));
    ASSERT(txg != 0);


    dprintf("dmu_sync txg=%llu, s,o,q %llu %llu %llu\n",
        txg, tx->tx_synced_txg, tx->tx_open_txg, tx->tx_quiesced_txg);

    /*
     * XXX - would be nice if we could do this without suspending...
     */
    txg_suspend(dp);

    /*
     * If this txg already synced, there's nothing to do.
     */
    if (txg <= tx->tx_synced_txg) {
        txg_resume(dp);
        /*
         * If we're running ziltest, we need the blkptr regardless.
         */
        if (txg > spa_freeze_txg(dp->dp_spa)) {
            /* if db_blkptr == NULL, this was an empty write */
            if (db->db_blkptr)
                *bp = *db->db_blkptr; /* structure assignment */
            return (0);
        }
        return (EEXIST);
    }

    mutex_enter(&db->db_mtx);

    blk = db->db_d.db_overridden_by[txg&TXG_MASK];
    if (blk == IN_DMU_SYNC) {
        /*
         * We have already issued a sync write for this buffer.
         */
        mutex_exit(&db->db_mtx);
        txg_resume(dp);
        return (EALREADY);
    } else if (blk != NULL) {
        /*
         * This buffer had already been synced.  It could not
         * have been dirtied since, or we would have cleared blk.
         */
        *bp = *blk; /* structure assignment */
        mutex_exit(&db->db_mtx);
        txg_resume(dp);
        return (0);
    }

    if (txg == tx->tx_syncing_txg) {
        while (db->db_data_pending) {
            /*
             * IO is in-progress.  Wait for it to finish.
             * XXX - would be nice to be able to somehow "attach"
             * this zio to the parent zio passed in.
             */
            cv_wait(&db->db_changed, &db->db_mtx);
            if (!db->db_data_pending &&
                db->db_blkptr && BP_IS_HOLE(db->db_blkptr)) {
                /*
                 * IO was compressed away
                 */
                *bp = *db->db_blkptr; /* structure assignment */
                mutex_exit(&db->db_mtx);
                txg_resume(dp);
                return (0);
            }
            ASSERT(db->db_data_pending ||
                (db->db_blkptr && db->db_blkptr->blk_birth == txg));
        }

        if (db->db_blkptr && db->db_blkptr->blk_birth == txg) {
            /*
             * IO is already completed.
             */
            *bp = *db->db_blkptr; /* structure assignment */
            mutex_exit(&db->db_mtx);
            txg_resume(dp);
            return (0);
        }
    }

    if (db->db_d.db_data_old[txg&TXG_MASK] == NULL) {
        /*
         * This dbuf isn't dirty, must have been free_range'd.
         * There's no need to log writes to freed blocks, so we're done.
         */
        mutex_exit(&db->db_mtx);
        txg_resume(dp);
        return (ENOENT);
    }

    ASSERT(db->db_d.db_overridden_by[txg&TXG_MASK] == NULL);
    db->db_d.db_overridden_by[txg&TXG_MASK] = IN_DMU_SYNC;
    /*
     * XXX - a little ugly to stash the blkptr in the callback
     * buffer.  We always need to make sure the following is true:
     * ASSERT(sizeof(blkptr_t) >= sizeof(dmu_sync_cbin_t));
     */
    in = kmem_alloc(sizeof (blkptr_t), KM_SLEEP);
    in->db = db;
    in->txg = txg;
    in->done = done;
    in->arg = arg;
    mutex_exit(&db->db_mtx);
    txg_resume(dp);

    arc_flag = pio == NULL ? ARC_WAIT : ARC_NOWAIT;
    zb.zb_objset = os->os_dsl_dataset->ds_object;
    zb.zb_object = db->db.db_object;
    zb.zb_level = db->db_level;
    zb.zb_blkid = db->db_blkid;
    err = arc_write(pio, os->os_spa,
        zio_checksum_select(db->db_dnode->dn_checksum, os->os_checksum),
        zio_compress_select(db->db_dnode->dn_compress, os->os_compress),
        dmu_get_replication_level(os->os_spa, &zb, db->db_dnode->dn_type),
        txg, bp, db->db_d.db_data_old[txg&TXG_MASK], dmu_sync_done, in,
        ZIO_PRIORITY_SYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, arc_flag, &zb);
    ASSERT(err == 0);

    return (arc_flag == ARC_NOWAIT ? EINPROGRESS : 0);
}

uint64_t
dmu_object_max_nonzero_offset(objset_t *os, uint64_t object)
{
    dnode_t *dn;

    /* XXX assumes dnode_hold will not get an i/o error */
    (void) dnode_hold(os->os, object, FTAG, &dn);
    uint64_t rv = dnode_max_nonzero_offset(dn);
    dnode_rele(dn, FTAG);
    return (rv);
}

int
dmu_object_set_blocksize(objset_t *os, uint64_t object, uint64_t size, int ibs,
    dmu_tx_t *tx)
{
    dnode_t *dn;
    int err;

    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);
    err = dnode_set_blksz(dn, size, ibs, tx);
    dnode_rele(dn, FTAG);
    return (err);
}

void
dmu_object_set_checksum(objset_t *os, uint64_t object, uint8_t checksum,
    dmu_tx_t *tx)
{
    dnode_t *dn;

    /* XXX assumes dnode_hold will not get an i/o error */
    (void) dnode_hold(os->os, object, FTAG, &dn);
    ASSERT(checksum < ZIO_CHECKSUM_FUNCTIONS);
    dn->dn_checksum = checksum;
    dnode_setdirty(dn, tx);
    dnode_rele(dn, FTAG);
}

void
dmu_object_set_compress(objset_t *os, uint64_t object, uint8_t compress,
    dmu_tx_t *tx)
{
    dnode_t *dn;

    /* XXX assumes dnode_hold will not get an i/o error */
    (void) dnode_hold(os->os, object, FTAG, &dn);
    ASSERT(compress < ZIO_COMPRESS_FUNCTIONS);
    dn->dn_compress = compress;
    dnode_setdirty(dn, tx);
    dnode_rele(dn, FTAG);
}

/*
 * XXX - eventually, this should take into account per-dataset (or
 *       even per-object?) user requests for higher levels of replication.
 */
int
dmu_get_replication_level(spa_t *spa, zbookmark_t *zb, dmu_object_type_t ot)
{
    int ncopies = 1;

    if (dmu_ot[ot].ot_metadata)
        ncopies++;
    if (zb->zb_level != 0)
        ncopies++;
    if (zb->zb_objset == 0 && zb->zb_object == 0)
        ncopies++;
    return (MIN(ncopies, spa_max_replication(spa)));
}

int
dmu_offset_next(objset_t *os, uint64_t object, boolean_t hole, uint64_t *off)
{
    dnode_t *dn;
    int i, err;

    err = dnode_hold(os->os, object, FTAG, &dn);
    if (err)
        return (err);
    /*
     * Sync any current changes before
     * we go trundling through the block pointers.
     */
    for (i = 0; i < TXG_SIZE; i++) {
        if (list_link_active(&dn->dn_dirty_link[i]))
            break;
    }
    if (i != TXG_SIZE) {
        dnode_rele(dn, FTAG);
        txg_wait_synced(dmu_objset_pool(os), 0);
        err = dnode_hold(os->os, object, FTAG, &dn);
        if (err)
            return (err);
    }

    err = dnode_next_offset(dn, hole, off, 1, 1);
    dnode_rele(dn, FTAG);

    return (err);
}

void
dmu_object_info_from_dnode(dnode_t *dn, dmu_object_info_t *doi)
{
    rw_enter(&dn->dn_struct_rwlock, RW_READER);
    mutex_enter(&dn->dn_mtx);

    doi->doi_data_block_size = dn->dn_datablksz;
    doi->doi_metadata_block_size = dn->dn_indblkshift ?
        1ULL << dn->dn_indblkshift : 0;
    doi->doi_indirection = dn->dn_nlevels;
    doi->doi_checksum = dn->dn_checksum;
    doi->doi_compress = dn->dn_compress;
    doi->doi_physical_blks = (DN_USED_BYTES(dn->dn_phys) +
        SPA_MINBLOCKSIZE/2) >> SPA_MINBLOCKSHIFT;
    doi->doi_max_block_offset = dn->dn_phys->dn_maxblkid;
    doi->doi_type = dn->dn_type;
    doi->doi_bonus_size = dn->dn_bonuslen;
    doi->doi_bonus_type = dn->dn_bonustype;

    mutex_exit(&dn->dn_mtx);
    rw_exit(&dn->dn_struct_rwlock);
}

/*
 * Get information on a DMU object.
 * If doi is NULL, just indicates whether the object exists.
 */
int
dmu_object_info(objset_t *os, uint64_t object, dmu_object_info_t *doi)
{
    dnode_t *dn;
    int err = dnode_hold(os->os, object, FTAG, &dn);

    if (err)
        return (err);

    if (doi != NULL)
        dmu_object_info_from_dnode(dn, doi);

    dnode_rele(dn, FTAG);
    return (0);
}

/*
 * As above, but faster; can be used when you have a held dbuf in hand.
 */
void
dmu_object_info_from_db(dmu_buf_t *db, dmu_object_info_t *doi)
{
    dmu_object_info_from_dnode(((dmu_buf_impl_t *)db)->db_dnode, doi);
}

/*
 * Faster still when you only care about the size.
 * This is specifically optimized for zfs_getattr().
 */
void
dmu_object_size_from_db(dmu_buf_t *db, uint32_t *blksize, u_longlong_t *nblk512)
{
    dnode_t *dn = ((dmu_buf_impl_t *)db)->db_dnode;

    *blksize = dn->dn_datablksz;
    /* add 1 for dnode space */
    *nblk512 = ((DN_USED_BYTES(dn->dn_phys) + SPA_MINBLOCKSIZE/2) >>
        SPA_MINBLOCKSHIFT) + 1;
}

/*
 * Given a bookmark, return the name of the dataset, object, and range in
 * human-readable format.
 */
int
spa_bookmark_name(spa_t *spa, zbookmark_t *zb, char *dsname, size_t dslen,
    char *objname, size_t objlen, char *range, size_t rangelen)
{
    dsl_pool_t *dp;
    dsl_dataset_t *ds = NULL;
    objset_t *os = NULL;
    dnode_t *dn = NULL;
    int err, shift;

    if (dslen < MAXNAMELEN || objlen < 32 || rangelen < 64)
        return (ENOSPC);

    dp = spa_get_dsl(spa);
    if (zb->zb_objset != 0) {
        rw_enter(&dp->dp_config_rwlock, RW_READER);
        err = dsl_dataset_open_obj(dp, zb->zb_objset,
            NULL, DS_MODE_NONE, FTAG, &ds);
        if (err) {
            rw_exit(&dp->dp_config_rwlock);
            return (err);
        }
        dsl_dataset_name(ds, dsname);
        dsl_dataset_close(ds, DS_MODE_NONE, FTAG);
        rw_exit(&dp->dp_config_rwlock);

        err = dmu_objset_open(dsname, DMU_OST_ANY, DS_MODE_NONE, &os);
        if (err)
            goto out;

    } else {
        dsl_dataset_name(NULL, dsname);
        os = dp->dp_meta_objset;
    }


    if (zb->zb_object == DMU_META_DNODE_OBJECT) {
        (void) strncpy(objname, "mdn", objlen);
    } else {
        (void) snprintf(objname, objlen, "%lld",
            (longlong_t)zb->zb_object);
    }

    err = dnode_hold(os->os, zb->zb_object, FTAG, &dn);
    if (err)
        goto out;

    shift = (dn->dn_datablkshift?dn->dn_datablkshift:SPA_MAXBLOCKSHIFT) +
        zb->zb_level * (dn->dn_indblkshift - SPA_BLKPTRSHIFT);
    (void) snprintf(range, rangelen, "%llu-%llu",
        (u_longlong_t)(zb->zb_blkid << shift),
        (u_longlong_t)((zb->zb_blkid+1) << shift));

out:
    if (dn)
        dnode_rele(dn, FTAG);
    if (os && os != dp->dp_meta_objset)
        dmu_objset_close(os);
    return (err);
}

void
byteswap_uint64_array(void *vbuf, size_t size)
{
    uint64_t *buf = vbuf;
    size_t count = size >> 3;
    int i;

    ASSERT((size & 7) == 0);

    for (i = 0; i < count; i++)
        buf[i] = BSWAP_64(buf[i]);
}

void
byteswap_uint32_array(void *vbuf, size_t size)
{
    uint32_t *buf = vbuf;
    size_t count = size >> 2;
    int i;

    ASSERT((size & 3) == 0);

    for (i = 0; i < count; i++)
        buf[i] = BSWAP_32(buf[i]);
}

void
byteswap_uint16_array(void *vbuf, size_t size)
{
    uint16_t *buf = vbuf;
    size_t count = size >> 1;
    int i;

    ASSERT((size & 1) == 0);

    for (i = 0; i < count; i++)
        buf[i] = BSWAP_16(buf[i]);
}

/* ARGSUSED */
void
byteswap_uint8_array(void *vbuf, size_t size)
{
}

void
dmu_init(void)
{
    dbuf_init();
    dnode_init();
    arc_init();
}

void
dmu_fini(void)
{
    arc_fini();
    dnode_fini();
    dbuf_fini();
}