Rebase master to b121

[mirror_zfs.git] / module / zfs / dmu_objset.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/cred.h>
#include <sys/zfs_context.h>
#include <sys/dmu_objset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_pool.h>
#include <sys/dsl_synctask.h>
#include <sys/dsl_deleg.h>
#include <sys/dnode.h>
#include <sys/dbuf.h>
#include <sys/zvol.h>
#include <sys/dmu_tx.h>
#include <sys/zio_checksum.h>
#include <sys/zap.h>
#include <sys/zil.h>
#include <sys/dmu_impl.h>
#include <sys/zfs_ioctl.h>

spa_t *
dmu_objset_spa(objset_t *os)
{
        return (os->os->os_spa);
}

zilog_t *
dmu_objset_zil(objset_t *os)
{
        return (os->os->os_zil);
}

dsl_pool_t *
dmu_objset_pool(objset_t *os)
{
        dsl_dataset_t *ds;

        if ((ds = os->os->os_dsl_dataset) != NULL && ds->ds_dir)
                return (ds->ds_dir->dd_pool);
        else
                return (spa_get_dsl(os->os->os_spa));
}

dsl_dataset_t *
dmu_objset_ds(objset_t *os)
{
        return (os->os->os_dsl_dataset);
}

dmu_objset_type_t
dmu_objset_type(objset_t *os)
{
        return (os->os->os_phys->os_type);
}

void
dmu_objset_name(objset_t *os, char *buf)
{
        dsl_dataset_name(os->os->os_dsl_dataset, buf);
}

uint64_t
dmu_objset_id(objset_t *os)
{
        dsl_dataset_t *ds = os->os->os_dsl_dataset;

        return (ds ? ds->ds_object : 0);
}

static void
checksum_changed_cb(void *arg, uint64_t newval)
{
        objset_impl_t *osi = arg;

        /*
         * Inheritance should have been done by now.
         */
        ASSERT(newval != ZIO_CHECKSUM_INHERIT);

        osi->os_checksum = zio_checksum_select(newval, ZIO_CHECKSUM_ON_VALUE);
}

static void
compression_changed_cb(void *arg, uint64_t newval)
{
        objset_impl_t *osi = arg;

        /*
         * Inheritance and range checking should have been done by now.
         */
        ASSERT(newval != ZIO_COMPRESS_INHERIT);

        osi->os_compress = zio_compress_select(newval, ZIO_COMPRESS_ON_VALUE);
}

static void
copies_changed_cb(void *arg, uint64_t newval)
{
        objset_impl_t *osi = arg;

        /*
         * Inheritance and range checking should have been done by now.
         */
        ASSERT(newval > 0);
        ASSERT(newval <= spa_max_replication(osi->os_spa));

        osi->os_copies = newval;
}

static void
primary_cache_changed_cb(void *arg, uint64_t newval)
{
        objset_impl_t *osi = arg;

        /*
         * Inheritance and range checking should have been done by now.
         */
        ASSERT(newval == ZFS_CACHE_ALL || newval == ZFS_CACHE_NONE ||
            newval == ZFS_CACHE_METADATA);

        osi->os_primary_cache = newval;
}

static void
secondary_cache_changed_cb(void *arg, uint64_t newval)
{
        objset_impl_t *osi = arg;

        /*
         * Inheritance and range checking should have been done by now.
         */
        ASSERT(newval == ZFS_CACHE_ALL || newval == ZFS_CACHE_NONE ||
            newval == ZFS_CACHE_METADATA);

        osi->os_secondary_cache = newval;
}

void
dmu_objset_byteswap(void *buf, size_t size)
{
        objset_phys_t *osp = buf;

        ASSERT(size == OBJSET_OLD_PHYS_SIZE || size == sizeof (objset_phys_t));
        dnode_byteswap(&osp->os_meta_dnode);
        byteswap_uint64_array(&osp->os_zil_header, sizeof (zil_header_t));
        osp->os_type = BSWAP_64(osp->os_type);
        osp->os_flags = BSWAP_64(osp->os_flags);
        if (size == sizeof (objset_phys_t)) {
                dnode_byteswap(&osp->os_userused_dnode);
                dnode_byteswap(&osp->os_groupused_dnode);
        }
}

int
dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    objset_impl_t **osip)
{
        objset_impl_t *osi;
        int i, err;

        ASSERT(ds == NULL || MUTEX_HELD(&ds->ds_opening_lock));

        osi = kmem_zalloc(sizeof (objset_impl_t), KM_SLEEP);
        osi->os.os = osi;
        osi->os_dsl_dataset = ds;
        osi->os_spa = spa;
        osi->os_rootbp = bp;
        if (!BP_IS_HOLE(osi->os_rootbp)) {
                uint32_t aflags = ARC_WAIT;
                zbookmark_t zb;
                zb.zb_objset = ds ? ds->ds_object : 0;
                zb.zb_object = 0;
                zb.zb_level = -1;
                zb.zb_blkid = 0;
                if (DMU_OS_IS_L2CACHEABLE(osi))
                        aflags |= ARC_L2CACHE;

                dprintf_bp(osi->os_rootbp, "reading %s", "");
                /*
                 * NB: when bprewrite scrub can change the bp,
                 * and this is called from dmu_objset_open_ds_os, the bp
                 * could change, and we'll need a lock.
                 */
                err = arc_read_nolock(NULL, spa, osi->os_rootbp,
                    arc_getbuf_func, &osi->os_phys_buf,
                    ZIO_PRIORITY_SYNC_READ, ZIO_FLAG_CANFAIL, &aflags, &zb);
                if (err) {
                        kmem_free(osi, sizeof (objset_impl_t));
                        /* convert checksum errors into IO errors */
                        if (err == ECKSUM)
                                err = EIO;
                        return (err);
                }

                /* Increase the blocksize if we are permitted. */
                if (spa_version(spa) >= SPA_VERSION_USERSPACE &&
                    arc_buf_size(osi->os_phys_buf) < sizeof (objset_phys_t)) {
                        arc_buf_t *buf = arc_buf_alloc(spa,
                            sizeof (objset_phys_t), &osi->os_phys_buf,
                            ARC_BUFC_METADATA);
                        bzero(buf->b_data, sizeof (objset_phys_t));
                        bcopy(osi->os_phys_buf->b_data, buf->b_data,
                            arc_buf_size(osi->os_phys_buf));
                        (void) arc_buf_remove_ref(osi->os_phys_buf,
                            &osi->os_phys_buf);
                        osi->os_phys_buf = buf;
                }

                osi->os_phys = osi->os_phys_buf->b_data;
                osi->os_flags = osi->os_phys->os_flags;
        } else {
                int size = spa_version(spa) >= SPA_VERSION_USERSPACE ?
                    sizeof (objset_phys_t) : OBJSET_OLD_PHYS_SIZE;
                osi->os_phys_buf = arc_buf_alloc(spa, size,
                    &osi->os_phys_buf, ARC_BUFC_METADATA);
                osi->os_phys = osi->os_phys_buf->b_data;
                bzero(osi->os_phys, size);
        }

        /*
         * Note: the changed_cb will be called once before the register
         * func returns, thus changing the checksum/compression from the
         * default (fletcher2/off).  Snapshots don't need to know about
         * checksum/compression/copies.
         */
        if (ds) {
                err = dsl_prop_register(ds, "primarycache",
                    primary_cache_changed_cb, osi);
                if (err == 0)
                        err = dsl_prop_register(ds, "secondarycache",
                            secondary_cache_changed_cb, osi);
                if (!dsl_dataset_is_snapshot(ds)) {
                        if (err == 0)
                                err = dsl_prop_register(ds, "checksum",
                                    checksum_changed_cb, osi);
                        if (err == 0)
                                err = dsl_prop_register(ds, "compression",
                                    compression_changed_cb, osi);
                        if (err == 0)
                                err = dsl_prop_register(ds, "copies",
                                    copies_changed_cb, osi);
                }
                if (err) {
                        VERIFY(arc_buf_remove_ref(osi->os_phys_buf,
                            &osi->os_phys_buf) == 1);
                        kmem_free(osi, sizeof (objset_impl_t));
                        return (err);
                }
        } else if (ds == NULL) {
                /* It's the meta-objset. */
                osi->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
                osi->os_compress = ZIO_COMPRESS_LZJB;
                osi->os_copies = spa_max_replication(spa);
                osi->os_primary_cache = ZFS_CACHE_ALL;
                osi->os_secondary_cache = ZFS_CACHE_ALL;
        }

        osi->os_zil_header = osi->os_phys->os_zil_header;
        osi->os_zil = zil_alloc(&osi->os, &osi->os_zil_header);

        for (i = 0; i < TXG_SIZE; i++) {
                list_create(&osi->os_dirty_dnodes[i], sizeof (dnode_t),
                    offsetof(dnode_t, dn_dirty_link[i]));
                list_create(&osi->os_free_dnodes[i], sizeof (dnode_t),
                    offsetof(dnode_t, dn_dirty_link[i]));
        }
        list_create(&osi->os_dnodes, sizeof (dnode_t),
            offsetof(dnode_t, dn_link));
        list_create(&osi->os_downgraded_dbufs, sizeof (dmu_buf_impl_t),
            offsetof(dmu_buf_impl_t, db_link));

        mutex_init(&osi->os_lock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&osi->os_obj_lock, NULL, MUTEX_DEFAULT, NULL);
        mutex_init(&osi->os_user_ptr_lock, NULL, MUTEX_DEFAULT, NULL);

        osi->os_meta_dnode = dnode_special_open(osi,
            &osi->os_phys->os_meta_dnode, DMU_META_DNODE_OBJECT);
        if (arc_buf_size(osi->os_phys_buf) >= sizeof (objset_phys_t)) {
                osi->os_userused_dnode = dnode_special_open(osi,
                    &osi->os_phys->os_userused_dnode, DMU_USERUSED_OBJECT);
                osi->os_groupused_dnode = dnode_special_open(osi,
                    &osi->os_phys->os_groupused_dnode, DMU_GROUPUSED_OBJECT);
        }

        /*
         * We should be the only thread trying to do this because we
         * have ds_opening_lock
         */
        if (ds) {
                VERIFY(NULL == dsl_dataset_set_user_ptr(ds, osi,
                    dmu_objset_evict));
        }

        *osip = osi;
        return (0);
}

static int
dmu_objset_open_ds_os(dsl_dataset_t *ds, objset_t *os, dmu_objset_type_t type)
{
        objset_impl_t *osi;

        mutex_enter(&ds->ds_opening_lock);
        osi = dsl_dataset_get_user_ptr(ds);
        if (osi == NULL) {
                int err;

                err = dmu_objset_open_impl(dsl_dataset_get_spa(ds),
                    ds, &ds->ds_phys->ds_bp, &osi);
                if (err) {
                        mutex_exit(&ds->ds_opening_lock);
                        return (err);
                }
        }
        mutex_exit(&ds->ds_opening_lock);

        os->os = osi;
        os->os_mode = DS_MODE_NOHOLD;

        if (type != DMU_OST_ANY && type != os->os->os_phys->os_type)
                return (EINVAL);
        return (0);
}

int
dmu_objset_open_ds(dsl_dataset_t *ds, dmu_objset_type_t type, objset_t **osp)
{
        objset_t *os;
        int err;

        os = kmem_alloc(sizeof (objset_t), KM_SLEEP);
        err = dmu_objset_open_ds_os(ds, os, type);
        if (err)
                kmem_free(os, sizeof (objset_t));
        else
                *osp = os;
        return (err);
}

/* called from zpl */
int
dmu_objset_open(const char *name, dmu_objset_type_t type, int mode,
    objset_t **osp)
{
        objset_t *os;
        dsl_dataset_t *ds;
        int err;

        ASSERT(DS_MODE_TYPE(mode) == DS_MODE_USER ||
            DS_MODE_TYPE(mode) == DS_MODE_OWNER);

        os = kmem_alloc(sizeof (objset_t), KM_SLEEP);
        if (DS_MODE_TYPE(mode) == DS_MODE_USER)
                err = dsl_dataset_hold(name, os, &ds);
        else
                err = dsl_dataset_own(name, mode, os, &ds);
        if (err) {
                kmem_free(os, sizeof (objset_t));
                return (err);
        }

        err = dmu_objset_open_ds_os(ds, os, type);
        if (err) {
                if (DS_MODE_TYPE(mode) == DS_MODE_USER)
                        dsl_dataset_rele(ds, os);
                else
                        dsl_dataset_disown(ds, os);
                kmem_free(os, sizeof (objset_t));
        } else {
                os->os_mode = mode;
                *osp = os;
        }
        return (err);
}

void
dmu_objset_close(objset_t *os)
{
        ASSERT(DS_MODE_TYPE(os->os_mode) == DS_MODE_USER ||
            DS_MODE_TYPE(os->os_mode) == DS_MODE_OWNER ||
            DS_MODE_TYPE(os->os_mode) == DS_MODE_NOHOLD);

        if (DS_MODE_TYPE(os->os_mode) == DS_MODE_USER)
                dsl_dataset_rele(os->os->os_dsl_dataset, os);
        else if (DS_MODE_TYPE(os->os_mode) == DS_MODE_OWNER)
                dsl_dataset_disown(os->os->os_dsl_dataset, os);
        kmem_free(os, sizeof (objset_t));
}

int
dmu_objset_evict_dbufs(objset_t *os)
{
        objset_impl_t *osi = os->os;
        dnode_t *dn;

        mutex_enter(&osi->os_lock);

        /* process the mdn last, since the other dnodes have holds on it */
        list_remove(&osi->os_dnodes, osi->os_meta_dnode);
        list_insert_tail(&osi->os_dnodes, osi->os_meta_dnode);

        /*
         * Find the first dnode with holds.  We have to do this dance
         * because dnode_add_ref() only works if you already have a
         * hold.  If there are no holds then it has no dbufs so OK to
         * skip.
         */
        for (dn = list_head(&osi->os_dnodes);
            dn && !dnode_add_ref(dn, FTAG);
            dn = list_next(&osi->os_dnodes, dn))
                continue;

        while (dn) {
                dnode_t *next_dn = dn;

                do {
                        next_dn = list_next(&osi->os_dnodes, next_dn);
                } while (next_dn && !dnode_add_ref(next_dn, FTAG));

                mutex_exit(&osi->os_lock);
                dnode_evict_dbufs(dn);
                dnode_rele(dn, FTAG);
                mutex_enter(&osi->os_lock);
                dn = next_dn;
        }
        mutex_exit(&osi->os_lock);
        return (list_head(&osi->os_dnodes) != osi->os_meta_dnode);
}

void
dmu_objset_evict(dsl_dataset_t *ds, void *arg)
{
        objset_impl_t *osi = arg;
        objset_t os;
        int i;

        for (i = 0; i < TXG_SIZE; i++) {
                ASSERT(list_head(&osi->os_dirty_dnodes[i]) == NULL);
                ASSERT(list_head(&osi->os_free_dnodes[i]) == NULL);
        }

        if (ds) {
                if (!dsl_dataset_is_snapshot(ds)) {
                        VERIFY(0 == dsl_prop_unregister(ds, "checksum",
                            checksum_changed_cb, osi));
                        VERIFY(0 == dsl_prop_unregister(ds, "compression",
                            compression_changed_cb, osi));
                        VERIFY(0 == dsl_prop_unregister(ds, "copies",
                            copies_changed_cb, osi));
                }
                VERIFY(0 == dsl_prop_unregister(ds, "primarycache",
                    primary_cache_changed_cb, osi));
                VERIFY(0 == dsl_prop_unregister(ds, "secondarycache",
                    secondary_cache_changed_cb, osi));
        }

        /*
         * We should need only a single pass over the dnode list, since
         * nothing can be added to the list at this point.
         */
        os.os = osi;
        (void) dmu_objset_evict_dbufs(&os);

        dnode_special_close(osi->os_meta_dnode);
        if (osi->os_userused_dnode) {
                dnode_special_close(osi->os_userused_dnode);
                dnode_special_close(osi->os_groupused_dnode);
        }
        zil_free(osi->os_zil);

        ASSERT3P(list_head(&osi->os_dnodes), ==, NULL);

        VERIFY(arc_buf_remove_ref(osi->os_phys_buf, &osi->os_phys_buf) == 1);
        mutex_destroy(&osi->os_lock);
        mutex_destroy(&osi->os_obj_lock);
        mutex_destroy(&osi->os_user_ptr_lock);
        kmem_free(osi, sizeof (objset_impl_t));
}

/* called from dsl for meta-objset */
objset_impl_t *
dmu_objset_create_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
    dmu_objset_type_t type, dmu_tx_t *tx)
{
        objset_impl_t *osi;
        dnode_t *mdn;

        ASSERT(dmu_tx_is_syncing(tx));
        if (ds)
                mutex_enter(&ds->ds_opening_lock);
        VERIFY(0 == dmu_objset_open_impl(spa, ds, bp, &osi));
        if (ds)
                mutex_exit(&ds->ds_opening_lock);
        mdn = osi->os_meta_dnode;

        dnode_allocate(mdn, DMU_OT_DNODE, 1 << DNODE_BLOCK_SHIFT,
            DN_MAX_INDBLKSHIFT, DMU_OT_NONE, 0, tx);

        /*
         * We don't want to have to increase the meta-dnode's nlevels
         * later, because then we could do it in quescing context while
         * we are also accessing it in open context.
         *
         * This precaution is not necessary for the MOS (ds == NULL),
         * because the MOS is only updated in syncing context.
         * This is most fortunate: the MOS is the only objset that
         * needs to be synced multiple times as spa_sync() iterates
         * to convergence, so minimizing its dn_nlevels matters.
         */
        if (ds != NULL) {
                int levels = 1;

                /*
                 * Determine the number of levels necessary for the meta-dnode
                 * to contain DN_MAX_OBJECT dnodes.
                 */
                while ((uint64_t)mdn->dn_nblkptr << (mdn->dn_datablkshift +
                    (levels - 1) * (mdn->dn_indblkshift - SPA_BLKPTRSHIFT)) <
                    DN_MAX_OBJECT * sizeof (dnode_phys_t))
                        levels++;

                mdn->dn_next_nlevels[tx->tx_txg & TXG_MASK] =
                    mdn->dn_nlevels = levels;
        }

        ASSERT(type != DMU_OST_NONE);
        ASSERT(type != DMU_OST_ANY);
        ASSERT(type < DMU_OST_NUMTYPES);
        osi->os_phys->os_type = type;
        if (dmu_objset_userused_enabled(osi)) {
                osi->os_phys->os_flags |= OBJSET_FLAG_USERACCOUNTING_COMPLETE;
                osi->os_flags = osi->os_phys->os_flags;
        }

        dsl_dataset_dirty(ds, tx);

        return (osi);
}

struct oscarg {
        void (*userfunc)(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx);
        void *userarg;
        dsl_dataset_t *clone_parent;
        const char *lastname;
        dmu_objset_type_t type;
        uint64_t flags;
};

/*ARGSUSED*/
static int
dmu_objset_create_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
        dsl_dir_t *dd = arg1;
        struct oscarg *oa = arg2;
        objset_t *mos = dd->dd_pool->dp_meta_objset;
        int err;
        uint64_t ddobj;

        err = zap_lookup(mos, dd->dd_phys->dd_child_dir_zapobj,
            oa->lastname, sizeof (uint64_t), 1, &ddobj);
        if (err != ENOENT)
                return (err ? err : EEXIST);

        if (oa->clone_parent != NULL) {
                /*
                 * You can't clone across pools.
                 */
                if (oa->clone_parent->ds_dir->dd_pool != dd->dd_pool)
                        return (EXDEV);

                /*
                 * You can only clone snapshots, not the head datasets.
                 */
                if (oa->clone_parent->ds_phys->ds_num_children == 0)
                        return (EINVAL);
        }

        return (0);
}

static void
dmu_objset_create_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
        dsl_dir_t *dd = arg1;
        struct oscarg *oa = arg2;
        dsl_dataset_t *ds;
        blkptr_t *bp;
        uint64_t dsobj;

        ASSERT(dmu_tx_is_syncing(tx));

        dsobj = dsl_dataset_create_sync(dd, oa->lastname,
            oa->clone_parent, oa->flags, cr, tx);

        VERIFY(0 == dsl_dataset_hold_obj(dd->dd_pool, dsobj, FTAG, &ds));
        bp = dsl_dataset_get_blkptr(ds);
        if (BP_IS_HOLE(bp)) {
                objset_impl_t *osi;

                /* This is an empty dmu_objset; not a clone. */
                osi = dmu_objset_create_impl(dsl_dataset_get_spa(ds),
                    ds, bp, oa->type, tx);

                if (oa->userfunc)
                        oa->userfunc(&osi->os, oa->userarg, cr, tx);
        }

        spa_history_internal_log(LOG_DS_CREATE, dd->dd_pool->dp_spa,
            tx, cr, "dataset = %llu", dsobj);

        dsl_dataset_rele(ds, FTAG);
}

int
dmu_objset_create(const char *name, dmu_objset_type_t type,
    objset_t *clone_parent, uint64_t flags,
    void (*func)(objset_t *os, void *arg, cred_t *cr, dmu_tx_t *tx), void *arg)
{
        dsl_dir_t *pdd;
        const char *tail;
        int err = 0;
        struct oscarg oa = { 0 };

        ASSERT(strchr(name, '@') == NULL);
        err = dsl_dir_open(name, FTAG, &pdd, &tail);
        if (err)
                return (err);
        if (tail == NULL) {
                dsl_dir_close(pdd, FTAG);
                return (EEXIST);
        }

        dprintf("name=%s\n", name);

        oa.userfunc = func;
        oa.userarg = arg;
        oa.lastname = tail;
        oa.type = type;
        oa.flags = flags;

        if (clone_parent != NULL) {
                /*
                 * You can't clone to a different type.
                 */
                if (clone_parent->os->os_phys->os_type != type) {
                        dsl_dir_close(pdd, FTAG);
                        return (EINVAL);
                }
                oa.clone_parent = clone_parent->os->os_dsl_dataset;
        }
        err = dsl_sync_task_do(pdd->dd_pool, dmu_objset_create_check,
            dmu_objset_create_sync, pdd, &oa, 5);
        dsl_dir_close(pdd, FTAG);
        return (err);
}

int
dmu_objset_destroy(const char *name, boolean_t defer)
{
        objset_t *os;
        int error;

        /*
         * If it looks like we'll be able to destroy it, and there's
         * an unplayed replay log sitting around, destroy the log.
         * It would be nicer to do this in dsl_dataset_destroy_sync(),
         * but the replay log objset is modified in open context.
         */
        error = dmu_objset_open(name, DMU_OST_ANY,
            DS_MODE_OWNER|DS_MODE_READONLY|DS_MODE_INCONSISTENT, &os);
        if (error == 0) {
                dsl_dataset_t *ds = os->os->os_dsl_dataset;
                zil_destroy(dmu_objset_zil(os), B_FALSE);

                error = dsl_dataset_destroy(ds, os, defer);
                /*
                 * dsl_dataset_destroy() closes the ds.
                 */
                kmem_free(os, sizeof (objset_t));
        }

        return (error);
}

/*
 * This will close the objset.
 */
int
dmu_objset_rollback(objset_t *os)
{
        int err;
        dsl_dataset_t *ds;

        ds = os->os->os_dsl_dataset;

        if (!dsl_dataset_tryown(ds, TRUE, os)) {
                dmu_objset_close(os);
                return (EBUSY);
        }

        err = dsl_dataset_rollback(ds, os->os->os_phys->os_type);

        /*
         * NB: we close the objset manually because the rollback
         * actually implicitly called dmu_objset_evict(), thus freeing
         * the objset_impl_t.
         */
        dsl_dataset_disown(ds, os);
        kmem_free(os, sizeof (objset_t));
        return (err);
}

struct snaparg {
        dsl_sync_task_group_t *dstg;
        char *snapname;
        char failed[MAXPATHLEN];
        boolean_t checkperms;
        nvlist_t *props;
};

static int
snapshot_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
        objset_t *os = arg1;
        struct snaparg *sn = arg2;

        /* The props have already been checked by zfs_check_userprops(). */

        return (dsl_dataset_snapshot_check(os->os->os_dsl_dataset,
            sn->snapname, tx));
}

static void
snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
        objset_t *os = arg1;
        dsl_dataset_t *ds = os->os->os_dsl_dataset;
        struct snaparg *sn = arg2;

        dsl_dataset_snapshot_sync(ds, sn->snapname, cr, tx);

        if (sn->props)
                dsl_props_set_sync(ds->ds_prev, sn->props, cr, tx);
}

static int
dmu_objset_snapshot_one(char *name, void *arg)
{
        struct snaparg *sn = arg;
        objset_t *os;
        int err;

        (void) strcpy(sn->failed, name);

        /*
         * Check permissions only when requested.  This only applies when
         * doing a recursive snapshot.  The permission checks for the starting
         * dataset have already been performed in zfs_secpolicy_snapshot()
         */
        if (sn->checkperms == B_TRUE &&
            (err = zfs_secpolicy_snapshot_perms(name, CRED())))
                return (err);

        err = dmu_objset_open(name, DMU_OST_ANY, DS_MODE_USER, &os);
        if (err != 0)
                return (err);

        /* If the objset is in an inconsistent state, return busy */
        if (os->os->os_dsl_dataset->ds_phys->ds_flags & DS_FLAG_INCONSISTENT) {
                dmu_objset_close(os);
                return (EBUSY);
        }

        /*
         * NB: we need to wait for all in-flight changes to get to disk,
         * so that we snapshot those changes.  zil_suspend does this as
         * a side effect.
         */
        err = zil_suspend(dmu_objset_zil(os));
        if (err == 0) {
                dsl_sync_task_create(sn->dstg, snapshot_check,
                    snapshot_sync, os, sn, 3);
        } else {
                dmu_objset_close(os);
        }

        return (err);
}

int
dmu_objset_snapshot(char *fsname, char *snapname,
    nvlist_t *props, boolean_t recursive)
{
        dsl_sync_task_t *dst;
        struct snaparg sn;
        spa_t *spa;
        int err;

        (void) strcpy(sn.failed, fsname);

        err = spa_open(fsname, &spa, FTAG);
        if (err)
                return (err);

        sn.dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
        sn.snapname = snapname;
        sn.props = props;

        if (recursive) {
                sn.checkperms = B_TRUE;
                err = dmu_objset_find(fsname,
                    dmu_objset_snapshot_one, &sn, DS_FIND_CHILDREN);
        } else {
                sn.checkperms = B_FALSE;
                err = dmu_objset_snapshot_one(fsname, &sn);
        }

        if (err == 0)
                err = dsl_sync_task_group_wait(sn.dstg);

        for (dst = list_head(&sn.dstg->dstg_tasks); dst;
            dst = list_next(&sn.dstg->dstg_tasks, dst)) {
                objset_t *os = dst->dst_arg1;
                dsl_dataset_t *ds = os->os->os_dsl_dataset;
                if (dst->dst_err)
                        dsl_dataset_name(ds, sn.failed);
                zil_resume(dmu_objset_zil(os));
                dmu_objset_close(os);
        }

        if (err)
                (void) strcpy(fsname, sn.failed);
        dsl_sync_task_group_destroy(sn.dstg);
        spa_close(spa, FTAG);
        return (err);
}

static void
dmu_objset_sync_dnodes(list_t *list, list_t *newlist, dmu_tx_t *tx)
{
        dnode_t *dn;

        while (dn = list_head(list)) {
                ASSERT(dn->dn_object != DMU_META_DNODE_OBJECT);
                ASSERT(dn->dn_dbuf->db_data_pending);
                /*
                 * Initialize dn_zio outside dnode_sync() because the
                 * meta-dnode needs to set it ouside dnode_sync().
                 */
                dn->dn_zio = dn->dn_dbuf->db_data_pending->dr_zio;
                ASSERT(dn->dn_zio);

                ASSERT3U(dn->dn_nlevels, <=, DN_MAX_LEVELS);
                list_remove(list, dn);

                if (newlist) {
                        (void) dnode_add_ref(dn, newlist);
                        list_insert_tail(newlist, dn);
                }

                dnode_sync(dn, tx);
        }
}

/* ARGSUSED */
static void
ready(zio_t *zio, arc_buf_t *abuf, void *arg)
{
        blkptr_t *bp = zio->io_bp;
        blkptr_t *bp_orig = &zio->io_bp_orig;
        objset_impl_t *os = arg;
        dnode_phys_t *dnp = &os->os_phys->os_meta_dnode;

        ASSERT(bp == os->os_rootbp);
        ASSERT(BP_GET_TYPE(bp) == DMU_OT_OBJSET);
        ASSERT(BP_GET_LEVEL(bp) == 0);

        /*
         * Update rootbp fill count: it should be the number of objects
         * allocated in the object set (not counting the "special"
         * objects that are stored in the objset_phys_t -- the meta
         * dnode and user/group accounting objects).
         */
        bp->blk_fill = 0;
        for (int i = 0; i < dnp->dn_nblkptr; i++)
                bp->blk_fill += dnp->dn_blkptr[i].blk_fill;

        if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
                ASSERT(DVA_EQUAL(BP_IDENTITY(bp), BP_IDENTITY(bp_orig)));
        } else {
                if (zio->io_bp_orig.blk_birth == os->os_synctx->tx_txg)
                        (void) dsl_dataset_block_kill(os->os_dsl_dataset,
                            &zio->io_bp_orig, zio, os->os_synctx);
                dsl_dataset_block_born(os->os_dsl_dataset, bp, os->os_synctx);
        }
}

/* called from dsl */
void
dmu_objset_sync(objset_impl_t *os, zio_t *pio, dmu_tx_t *tx)
{
        int txgoff;
        zbookmark_t zb;
        writeprops_t wp = { 0 };
        zio_t *zio;
        list_t *list;
        list_t *newlist = NULL;
        dbuf_dirty_record_t *dr;

        dprintf_ds(os->os_dsl_dataset, "txg=%llu\n", tx->tx_txg);

        ASSERT(dmu_tx_is_syncing(tx));
        /* XXX the write_done callback should really give us the tx... */
        os->os_synctx = tx;

        if (os->os_dsl_dataset == NULL) {
                /*
                 * This is the MOS.  If we have upgraded,
                 * spa_max_replication() could change, so reset
                 * os_copies here.
                 */
                os->os_copies = spa_max_replication(os->os_spa);
        }

        /*
         * Create the root block IO
         */
        zb.zb_objset = os->os_dsl_dataset ? os->os_dsl_dataset->ds_object : 0;
        zb.zb_object = 0;
        zb.zb_level = -1;       /* for block ordering; it's level 0 on disk */
        zb.zb_blkid = 0;

        wp.wp_type = DMU_OT_OBJSET;
        wp.wp_level = 0;        /* on-disk BP level; see above */
        wp.wp_copies = os->os_copies;
        wp.wp_oschecksum = os->os_checksum;
        wp.wp_oscompress = os->os_compress;

        if (BP_IS_OLDER(os->os_rootbp, tx->tx_txg)) {
                (void) dsl_dataset_block_kill(os->os_dsl_dataset,
                    os->os_rootbp, pio, tx);
        }

        arc_release(os->os_phys_buf, &os->os_phys_buf);

        zio = arc_write(pio, os->os_spa, &wp, DMU_OS_IS_L2CACHEABLE(os),
            tx->tx_txg, os->os_rootbp, os->os_phys_buf, ready, NULL, os,
            ZIO_PRIORITY_ASYNC_WRITE, ZIO_FLAG_MUSTSUCCEED, &zb);

        /*
         * Sync special dnodes - the parent IO for the sync is the root block
         */
        os->os_meta_dnode->dn_zio = zio;
        dnode_sync(os->os_meta_dnode, tx);

        os->os_phys->os_flags = os->os_flags;

        if (os->os_userused_dnode &&
            os->os_userused_dnode->dn_type != DMU_OT_NONE) {
                os->os_userused_dnode->dn_zio = zio;
                dnode_sync(os->os_userused_dnode, tx);
                os->os_groupused_dnode->dn_zio = zio;
                dnode_sync(os->os_groupused_dnode, tx);
        }

        txgoff = tx->tx_txg & TXG_MASK;

        if (dmu_objset_userused_enabled(os)) {
                newlist = &os->os_synced_dnodes;
                /*
                 * We must create the list here because it uses the
                 * dn_dirty_link[] of this txg.
                 */
                list_create(newlist, sizeof (dnode_t),
                    offsetof(dnode_t, dn_dirty_link[txgoff]));
        }

        dmu_objset_sync_dnodes(&os->os_free_dnodes[txgoff], newlist, tx);
        dmu_objset_sync_dnodes(&os->os_dirty_dnodes[txgoff], newlist, tx);

        list = &os->os_meta_dnode->dn_dirty_records[txgoff];
        while (dr = list_head(list)) {
                ASSERT(dr->dr_dbuf->db_level == 0);
                list_remove(list, dr);
                if (dr->dr_zio)
                        zio_nowait(dr->dr_zio);
        }
        /*
         * Free intent log blocks up to this tx.
         */
        zil_sync(os->os_zil, tx);
        os->os_phys->os_zil_header = os->os_zil_header;
        zio_nowait(zio);
}

static objset_used_cb_t *used_cbs[DMU_OST_NUMTYPES];

void
dmu_objset_register_type(dmu_objset_type_t ost, objset_used_cb_t *cb)
{
        used_cbs[ost] = cb;
}

boolean_t
dmu_objset_userused_enabled(objset_impl_t *os)
{
        return (spa_version(os->os_spa) >= SPA_VERSION_USERSPACE &&
            used_cbs[os->os_phys->os_type] &&
            os->os_userused_dnode);
}

void
dmu_objset_do_userquota_callbacks(objset_impl_t *os, dmu_tx_t *tx)
{
        dnode_t *dn;
        list_t *list = &os->os_synced_dnodes;
        static const char zerobuf[DN_MAX_BONUSLEN] = {0};

        ASSERT(list_head(list) == NULL || dmu_objset_userused_enabled(os));

        while (dn = list_head(list)) {
                dmu_object_type_t bonustype;

                ASSERT(!DMU_OBJECT_IS_SPECIAL(dn->dn_object));
                ASSERT(dn->dn_oldphys);
                ASSERT(dn->dn_phys->dn_type == DMU_OT_NONE ||
                    dn->dn_phys->dn_flags &
                    DNODE_FLAG_USERUSED_ACCOUNTED);

                /* Allocate the user/groupused objects if necessary. */
                if (os->os_userused_dnode->dn_type == DMU_OT_NONE) {
                        VERIFY(0 == zap_create_claim(&os->os,
                            DMU_USERUSED_OBJECT,
                            DMU_OT_USERGROUP_USED, DMU_OT_NONE, 0, tx));
                        VERIFY(0 == zap_create_claim(&os->os,
                            DMU_GROUPUSED_OBJECT,
                            DMU_OT_USERGROUP_USED, DMU_OT_NONE, 0, tx));
                }

                /*
                 * If the object was not previously
                 * accounted, pretend that it was free.
                 */
                if (!(dn->dn_oldphys->dn_flags &
                    DNODE_FLAG_USERUSED_ACCOUNTED)) {
                        bzero(dn->dn_oldphys, sizeof (dnode_phys_t));
                }

                /*
                 * If the object was freed, use the previous bonustype.
                 */
                bonustype = dn->dn_phys->dn_bonustype ?
                    dn->dn_phys->dn_bonustype : dn->dn_oldphys->dn_bonustype;
                ASSERT(dn->dn_phys->dn_type != 0 ||
                    (bcmp(DN_BONUS(dn->dn_phys), zerobuf,
                    DN_MAX_BONUSLEN) == 0 &&
                    DN_USED_BYTES(dn->dn_phys) == 0));
                ASSERT(dn->dn_oldphys->dn_type != 0 ||
                    (bcmp(DN_BONUS(dn->dn_oldphys), zerobuf,
                    DN_MAX_BONUSLEN) == 0 &&
                    DN_USED_BYTES(dn->dn_oldphys) == 0));
                used_cbs[os->os_phys->os_type](&os->os, bonustype,
                    DN_BONUS(dn->dn_oldphys), DN_BONUS(dn->dn_phys),
                    DN_USED_BYTES(dn->dn_oldphys),
                    DN_USED_BYTES(dn->dn_phys), tx);

                /*
                 * The mutex is needed here for interlock with dnode_allocate.
                 */
                mutex_enter(&dn->dn_mtx);
                zio_buf_free(dn->dn_oldphys, sizeof (dnode_phys_t));
                dn->dn_oldphys = NULL;
                mutex_exit(&dn->dn_mtx);

                list_remove(list, dn);
                dnode_rele(dn, list);
        }
}

boolean_t
dmu_objset_userspace_present(objset_t *os)
{
        return (os->os->os_phys->os_flags &
            OBJSET_FLAG_USERACCOUNTING_COMPLETE);
}

int
dmu_objset_userspace_upgrade(objset_t *os)
{
        uint64_t obj;
        int err = 0;

        if (dmu_objset_userspace_present(os))
                return (0);
        if (!dmu_objset_userused_enabled(os->os))
                return (ENOTSUP);
        if (dmu_objset_is_snapshot(os))
                return (EINVAL);

        /*
         * We simply need to mark every object dirty, so that it will be
         * synced out and now accounted.  If this is called
         * concurrently, or if we already did some work before crashing,
         * that's fine, since we track each object's accounted state
         * independently.
         */

        for (obj = 0; err == 0; err = dmu_object_next(os, &obj, FALSE, 0)) {
                dmu_tx_t *tx;
                dmu_buf_t *db;
                int objerr;

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

                objerr = dmu_bonus_hold(os, obj, FTAG, &db);
                if (objerr)
                        continue;
                tx = dmu_tx_create(os);
                dmu_tx_hold_bonus(tx, obj);
                objerr = dmu_tx_assign(tx, TXG_WAIT);
                if (objerr) {
                        dmu_tx_abort(tx);
                        continue;
                }
                dmu_buf_will_dirty(db, tx);
                dmu_buf_rele(db, FTAG);
                dmu_tx_commit(tx);
        }

        os->os->os_flags |= OBJSET_FLAG_USERACCOUNTING_COMPLETE;
        txg_wait_synced(dmu_objset_pool(os), 0);
        return (0);
}

void
dmu_objset_space(objset_t *os, uint64_t *refdbytesp, uint64_t *availbytesp,
    uint64_t *usedobjsp, uint64_t *availobjsp)
{
        dsl_dataset_space(os->os->os_dsl_dataset, refdbytesp, availbytesp,
            usedobjsp, availobjsp);
}

uint64_t
dmu_objset_fsid_guid(objset_t *os)
{
        return (dsl_dataset_fsid_guid(os->os->os_dsl_dataset));
}

void
dmu_objset_fast_stat(objset_t *os, dmu_objset_stats_t *stat)
{
        stat->dds_type = os->os->os_phys->os_type;
        if (os->os->os_dsl_dataset)
                dsl_dataset_fast_stat(os->os->os_dsl_dataset, stat);
}

void
dmu_objset_stats(objset_t *os, nvlist_t *nv)
{
        ASSERT(os->os->os_dsl_dataset ||
            os->os->os_phys->os_type == DMU_OST_META);

        if (os->os->os_dsl_dataset != NULL)
                dsl_dataset_stats(os->os->os_dsl_dataset, nv);

        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_TYPE,
            os->os->os_phys->os_type);
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USERACCOUNTING,
            dmu_objset_userspace_present(os));
}

int
dmu_objset_is_snapshot(objset_t *os)
{
        if (os->os->os_dsl_dataset != NULL)
                return (dsl_dataset_is_snapshot(os->os->os_dsl_dataset));
        else
                return (B_FALSE);
}

int
dmu_snapshot_realname(objset_t *os, char *name, char *real, int maxlen,
    boolean_t *conflict)
{
        dsl_dataset_t *ds = os->os->os_dsl_dataset;
        uint64_t ignored;

        if (ds->ds_phys->ds_snapnames_zapobj == 0)
                return (ENOENT);

        return (zap_lookup_norm(ds->ds_dir->dd_pool->dp_meta_objset,
            ds->ds_phys->ds_snapnames_zapobj, name, 8, 1, &ignored, MT_FIRST,
            real, maxlen, conflict));
}

int
dmu_snapshot_list_next(objset_t *os, int namelen, char *name,
    uint64_t *idp, uint64_t *offp, boolean_t *case_conflict)
{
        dsl_dataset_t *ds = os->os->os_dsl_dataset;
        zap_cursor_t cursor;
        zap_attribute_t attr;

        if (ds->ds_phys->ds_snapnames_zapobj == 0)
                return (ENOENT);

        zap_cursor_init_serialized(&cursor,
            ds->ds_dir->dd_pool->dp_meta_objset,
            ds->ds_phys->ds_snapnames_zapobj, *offp);

        if (zap_cursor_retrieve(&cursor, &attr) != 0) {
                zap_cursor_fini(&cursor);
                return (ENOENT);
        }

        if (strlen(attr.za_name) + 1 > namelen) {
                zap_cursor_fini(&cursor);
                return (ENAMETOOLONG);
        }

        (void) strcpy(name, attr.za_name);
        if (idp)
                *idp = attr.za_first_integer;
        if (case_conflict)
                *case_conflict = attr.za_normalization_conflict;
        zap_cursor_advance(&cursor);
        *offp = zap_cursor_serialize(&cursor);
        zap_cursor_fini(&cursor);

        return (0);
}

int
dmu_dir_list_next(objset_t *os, int namelen, char *name,
    uint64_t *idp, uint64_t *offp)
{
        dsl_dir_t *dd = os->os->os_dsl_dataset->ds_dir;
        zap_cursor_t cursor;
        zap_attribute_t attr;

        /* there is no next dir on a snapshot! */
        if (os->os->os_dsl_dataset->ds_object !=
            dd->dd_phys->dd_head_dataset_obj)
                return (ENOENT);

        zap_cursor_init_serialized(&cursor,
            dd->dd_pool->dp_meta_objset,
            dd->dd_phys->dd_child_dir_zapobj, *offp);

        if (zap_cursor_retrieve(&cursor, &attr) != 0) {
                zap_cursor_fini(&cursor);
                return (ENOENT);
        }

        if (strlen(attr.za_name) + 1 > namelen) {
                zap_cursor_fini(&cursor);
                return (ENAMETOOLONG);
        }

        (void) strcpy(name, attr.za_name);
        if (idp)
                *idp = attr.za_first_integer;
        zap_cursor_advance(&cursor);
        *offp = zap_cursor_serialize(&cursor);
        zap_cursor_fini(&cursor);

        return (0);
}

struct findarg {
        int (*func)(char *, void *);
        void *arg;
};

/* ARGSUSED */
static int
findfunc(spa_t *spa, uint64_t dsobj, const char *dsname, void *arg)
{
        struct findarg *fa = arg;
        return (fa->func((char *)dsname, fa->arg));
}

/*
 * Find all objsets under name, and for each, call 'func(child_name, arg)'.
 * Perhaps change all callers to use dmu_objset_find_spa()?
 */
int
dmu_objset_find(char *name, int func(char *, void *), void *arg, int flags)
{
        struct findarg fa;
        fa.func = func;
        fa.arg = arg;
        return (dmu_objset_find_spa(NULL, name, findfunc, &fa, flags));
}

/*
 * Find all objsets under name, call func on each
 */
int
dmu_objset_find_spa(spa_t *spa, const char *name,
    int func(spa_t *, uint64_t, const char *, void *), void *arg, int flags)
{
        dsl_dir_t *dd;
        dsl_pool_t *dp;
        dsl_dataset_t *ds;
        zap_cursor_t zc;
        zap_attribute_t *attr;
        char *child;
        uint64_t thisobj;
        int err;

        if (name == NULL)
                name = spa_name(spa);
        err = dsl_dir_open_spa(spa, name, FTAG, &dd, NULL);
        if (err)
                return (err);

        /* Don't visit hidden ($MOS & $ORIGIN) objsets. */
        if (dd->dd_myname[0] == '$') {
                dsl_dir_close(dd, FTAG);
                return (0);
        }

        thisobj = dd->dd_phys->dd_head_dataset_obj;
        attr = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
        dp = dd->dd_pool;

        /*
         * Iterate over all children.
         */
        if (flags & DS_FIND_CHILDREN) {
                for (zap_cursor_init(&zc, dp->dp_meta_objset,
                    dd->dd_phys->dd_child_dir_zapobj);
                    zap_cursor_retrieve(&zc, attr) == 0;
                    (void) zap_cursor_advance(&zc)) {
                        ASSERT(attr->za_integer_length == sizeof (uint64_t));
                        ASSERT(attr->za_num_integers == 1);

                        child = kmem_alloc(MAXPATHLEN, KM_SLEEP);
                        (void) strcpy(child, name);
                        (void) strcat(child, "/");
                        (void) strcat(child, attr->za_name);
                        err = dmu_objset_find_spa(spa, child, func, arg, flags);
                        kmem_free(child, MAXPATHLEN);
                        if (err)
                                break;
                }
                zap_cursor_fini(&zc);

                if (err) {
                        dsl_dir_close(dd, FTAG);
                        kmem_free(attr, sizeof (zap_attribute_t));
                        return (err);
                }
        }

        /*
         * Iterate over all snapshots.
         */
        if (flags & DS_FIND_SNAPSHOTS) {
                if (!dsl_pool_sync_context(dp))
                        rw_enter(&dp->dp_config_rwlock, RW_READER);
                err = dsl_dataset_hold_obj(dp, thisobj, FTAG, &ds);
                if (!dsl_pool_sync_context(dp))
                        rw_exit(&dp->dp_config_rwlock);

                if (err == 0) {
                        uint64_t snapobj = ds->ds_phys->ds_snapnames_zapobj;
                        dsl_dataset_rele(ds, FTAG);

                        for (zap_cursor_init(&zc, dp->dp_meta_objset, snapobj);
                            zap_cursor_retrieve(&zc, attr) == 0;
                            (void) zap_cursor_advance(&zc)) {
                                ASSERT(attr->za_integer_length ==
                                    sizeof (uint64_t));
                                ASSERT(attr->za_num_integers == 1);

                                child = kmem_alloc(MAXPATHLEN, KM_SLEEP);
                                (void) strcpy(child, name);
                                (void) strcat(child, "@");
                                (void) strcat(child, attr->za_name);
                                err = func(spa, attr->za_first_integer,
                                    child, arg);
                                kmem_free(child, MAXPATHLEN);
                                if (err)
                                        break;
                        }
                        zap_cursor_fini(&zc);
                }
        }

        dsl_dir_close(dd, FTAG);
        kmem_free(attr, sizeof (zap_attribute_t));

        if (err)
                return (err);

        /*
         * Apply to self if appropriate.
         */
        err = func(spa, thisobj, name, arg);
        return (err);
}

/* ARGSUSED */
int
dmu_objset_prefetch(char *name, void *arg)
{
        dsl_dataset_t *ds;

        if (dsl_dataset_hold(name, FTAG, &ds))
                return (0);

        if (!BP_IS_HOLE(&ds->ds_phys->ds_bp)) {
                mutex_enter(&ds->ds_opening_lock);
                if (!dsl_dataset_get_user_ptr(ds)) {
                        uint32_t aflags = ARC_NOWAIT | ARC_PREFETCH;
                        zbookmark_t zb;

                        zb.zb_objset = ds->ds_object;
                        zb.zb_object = 0;
                        zb.zb_level = -1;
                        zb.zb_blkid = 0;

                        (void) arc_read_nolock(NULL, dsl_dataset_get_spa(ds),
                            &ds->ds_phys->ds_bp, NULL, NULL,
                            ZIO_PRIORITY_ASYNC_READ,
                            ZIO_FLAG_CANFAIL | ZIO_FLAG_SPECULATIVE,
                            &aflags, &zb);
                }
                mutex_exit(&ds->ds_opening_lock);
        }

        dsl_dataset_rele(ds, FTAG);
        return (0);
}

void
dmu_objset_set_user(objset_t *os, void *user_ptr)
{
        ASSERT(MUTEX_HELD(&os->os->os_user_ptr_lock));
        os->os->os_user_ptr = user_ptr;
}

void *
dmu_objset_get_user(objset_t *os)
{
        ASSERT(MUTEX_HELD(&os->os->os_user_ptr_lock));
        return (os->os->os_user_ptr);
}