Optimize RAIDZ expansion

[zfs.git] / module / zfs / dsl_dataset.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 https://opensource.org/licenses/CDDL-1.0.
 * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2011, 2020 by Delphix. All rights reserved.
 * Copyright (c) 2014, Joyent, Inc. All rights reserved.
 * Copyright (c) 2014 RackTop Systems.
 * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
 * Copyright (c) 2016 Actifio, Inc. All rights reserved.
 * Copyright 2016, OmniTI Computer Consulting, Inc. All rights reserved.
 * Copyright 2017 Nexenta Systems, Inc.
 * Copyright (c) 2019, Klara Inc.
 * Copyright (c) 2019, Allan Jude
 * Copyright (c) 2020 The FreeBSD Foundation [1]
 *
 * [1] Portions of this software were developed by Allan Jude
 *     under sponsorship from the FreeBSD Foundation.
 */

#include <sys/dmu_objset.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_synctask.h>
#include <sys/dmu_traverse.h>
#include <sys/dmu_impl.h>
#include <sys/dmu_tx.h>
#include <sys/arc.h>
#include <sys/zio.h>
#include <sys/zap.h>
#include <sys/zfeature.h>
#include <sys/unique.h>
#include <sys/zfs_context.h>
#include <sys/zfs_ioctl.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/vdev.h>
#include <sys/zfs_znode.h>
#include <sys/zfs_onexit.h>
#include <sys/zvol.h>
#include <sys/dsl_scan.h>
#include <sys/dsl_deadlist.h>
#include <sys/dsl_destroy.h>
#include <sys/dsl_userhold.h>
#include <sys/dsl_bookmark.h>
#include <sys/policy.h>
#include <sys/dmu_send.h>
#include <sys/dmu_recv.h>
#include <sys/zio_compress.h>
#include <zfs_fletcher.h>
#include <sys/zio_checksum.h>
#include <sys/brt.h>

/*
 * The SPA supports block sizes up to 16MB.  However, very large blocks
 * can have an impact on i/o latency (e.g. tying up a spinning disk for
 * ~300ms), and also potentially on the memory allocator.  Therefore,
 * we did not allow the recordsize to be set larger than zfs_max_recordsize
 * (former default: 1MB).  Larger blocks could be created by changing this
 * tunable, and pools with larger blocks could always be imported and used,
 * regardless of this setting.
 *
 * We do, however, still limit it by default to 1M on x86_32, because Linux's
 * 3/1 memory split doesn't leave much room for 16M chunks.
 */
#ifdef _ILP32
uint_t zfs_max_recordsize =  1 * 1024 * 1024;
#else
uint_t zfs_max_recordsize = 16 * 1024 * 1024;
#endif
static int zfs_allow_redacted_dataset_mount = 0;

int zfs_snapshot_history_enabled = 1;

#define SWITCH64(x, y) \
        { \
                uint64_t __tmp = (x); \
                (x) = (y); \
                (y) = __tmp; \
        }

#define DS_REF_MAX      (1ULL << 62)

static void dsl_dataset_set_remap_deadlist_object(dsl_dataset_t *ds,
    uint64_t obj, dmu_tx_t *tx);
static void dsl_dataset_unset_remap_deadlist_object(dsl_dataset_t *ds,
    dmu_tx_t *tx);

static void unload_zfeature(dsl_dataset_t *ds, spa_feature_t f);

extern uint_t spa_asize_inflation;

static zil_header_t zero_zil;

/*
 * Figure out how much of this delta should be propagated to the dsl_dir
 * layer.  If there's a refreservation, that space has already been
 * partially accounted for in our ancestors.
 */
static int64_t
parent_delta(dsl_dataset_t *ds, int64_t delta)
{
        dsl_dataset_phys_t *ds_phys;
        uint64_t old_bytes, new_bytes;

        if (ds->ds_reserved == 0)
                return (delta);

        ds_phys = dsl_dataset_phys(ds);
        old_bytes = MAX(ds_phys->ds_unique_bytes, ds->ds_reserved);
        new_bytes = MAX(ds_phys->ds_unique_bytes + delta, ds->ds_reserved);

        ASSERT3U(ABS((int64_t)(new_bytes - old_bytes)), <=, ABS(delta));
        return (new_bytes - old_bytes);
}

void
dsl_dataset_block_born(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;
        int used = bp_get_dsize_sync(spa, bp);
        int compressed = BP_GET_PSIZE(bp);
        int uncompressed = BP_GET_UCSIZE(bp);
        int64_t delta;
        spa_feature_t f;

        dprintf_bp(bp, "ds=%p", ds);

        ASSERT(dmu_tx_is_syncing(tx));
        /* It could have been compressed away to nothing */
        if (BP_IS_HOLE(bp) || BP_IS_REDACTED(bp))
                return;
        ASSERT(BP_GET_TYPE(bp) != DMU_OT_NONE);
        ASSERT(DMU_OT_IS_VALID(BP_GET_TYPE(bp)));
        if (ds == NULL) {
                dsl_pool_mos_diduse_space(tx->tx_pool,
                    used, compressed, uncompressed);
                return;
        }

        ASSERT3U(BP_GET_LOGICAL_BIRTH(bp), >,
            dsl_dataset_phys(ds)->ds_prev_snap_txg);
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
        mutex_enter(&ds->ds_lock);
        delta = parent_delta(ds, used);
        dsl_dataset_phys(ds)->ds_referenced_bytes += used;
        dsl_dataset_phys(ds)->ds_compressed_bytes += compressed;
        dsl_dataset_phys(ds)->ds_uncompressed_bytes += uncompressed;
        dsl_dataset_phys(ds)->ds_unique_bytes += used;

        if (BP_GET_LSIZE(bp) > SPA_OLD_MAXBLOCKSIZE) {
                ds->ds_feature_activation[SPA_FEATURE_LARGE_BLOCKS] =
                    (void *)B_TRUE;
        }


        f = zio_checksum_to_feature(BP_GET_CHECKSUM(bp));
        if (f != SPA_FEATURE_NONE) {
                ASSERT3S(spa_feature_table[f].fi_type, ==,
                    ZFEATURE_TYPE_BOOLEAN);
                ds->ds_feature_activation[f] = (void *)B_TRUE;
        }

        f = zio_compress_to_feature(BP_GET_COMPRESS(bp));
        if (f != SPA_FEATURE_NONE) {
                ASSERT3S(spa_feature_table[f].fi_type, ==,
                    ZFEATURE_TYPE_BOOLEAN);
                ds->ds_feature_activation[f] = (void *)B_TRUE;
        }

        /*
         * Track block for livelist, but ignore embedded blocks because
         * they do not need to be freed.
         */
        if (dsl_deadlist_is_open(&ds->ds_dir->dd_livelist) &&
            BP_GET_LOGICAL_BIRTH(bp) > ds->ds_dir->dd_origin_txg &&
            !(BP_IS_EMBEDDED(bp))) {
                ASSERT(dsl_dir_is_clone(ds->ds_dir));
                ASSERT(spa_feature_is_enabled(spa,
                    SPA_FEATURE_LIVELIST));
                bplist_append(&ds->ds_dir->dd_pending_allocs, bp);
        }

        mutex_exit(&ds->ds_lock);
        dsl_dir_diduse_transfer_space(ds->ds_dir, delta,
            compressed, uncompressed, used,
            DD_USED_REFRSRV, DD_USED_HEAD, tx);
}

/*
 * Called when the specified segment has been remapped, and is thus no
 * longer referenced in the head dataset.  The vdev must be indirect.
 *
 * If the segment is referenced by a snapshot, put it on the remap deadlist.
 * Otherwise, add this segment to the obsolete spacemap.
 */
void
dsl_dataset_block_remapped(dsl_dataset_t *ds, uint64_t vdev, uint64_t offset,
    uint64_t size, uint64_t birth, dmu_tx_t *tx)
{
        spa_t *spa = ds->ds_dir->dd_pool->dp_spa;

        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(birth <= tx->tx_txg);
        ASSERT(!ds->ds_is_snapshot);

        if (birth > dsl_dataset_phys(ds)->ds_prev_snap_txg) {
                spa_vdev_indirect_mark_obsolete(spa, vdev, offset, size, tx);
        } else {
                blkptr_t fakebp;
                dva_t *dva = &fakebp.blk_dva[0];

                ASSERT(ds != NULL);

                mutex_enter(&ds->ds_remap_deadlist_lock);
                if (!dsl_dataset_remap_deadlist_exists(ds)) {
                        dsl_dataset_create_remap_deadlist(ds, tx);
                }
                mutex_exit(&ds->ds_remap_deadlist_lock);

                BP_ZERO(&fakebp);
                BP_SET_LOGICAL_BIRTH(&fakebp, birth);
                DVA_SET_VDEV(dva, vdev);
                DVA_SET_OFFSET(dva, offset);
                DVA_SET_ASIZE(dva, size);
                dsl_deadlist_insert(&ds->ds_remap_deadlist, &fakebp, B_FALSE,
                    tx);
        }
}

int
dsl_dataset_block_kill(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx,
    boolean_t async)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;

        int used = bp_get_dsize_sync(spa, bp);
        int compressed = BP_GET_PSIZE(bp);
        int uncompressed = BP_GET_UCSIZE(bp);

        if (BP_IS_HOLE(bp) || BP_IS_REDACTED(bp))
                return (0);

        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(BP_GET_LOGICAL_BIRTH(bp) <= tx->tx_txg);

        if (ds == NULL) {
                dsl_free(tx->tx_pool, tx->tx_txg, bp);
                dsl_pool_mos_diduse_space(tx->tx_pool,
                    -used, -compressed, -uncompressed);
                return (used);
        }
        ASSERT3P(tx->tx_pool, ==, ds->ds_dir->dd_pool);

        ASSERT(!ds->ds_is_snapshot);
        dmu_buf_will_dirty(ds->ds_dbuf, tx);

        /*
         * Track block for livelist, but ignore embedded blocks because
         * they do not need to be freed.
         */
        if (dsl_deadlist_is_open(&ds->ds_dir->dd_livelist) &&
            BP_GET_LOGICAL_BIRTH(bp) > ds->ds_dir->dd_origin_txg &&
            !(BP_IS_EMBEDDED(bp))) {
                ASSERT(dsl_dir_is_clone(ds->ds_dir));
                ASSERT(spa_feature_is_enabled(spa,
                    SPA_FEATURE_LIVELIST));
                bplist_append(&ds->ds_dir->dd_pending_frees, bp);
        }

        if (BP_GET_LOGICAL_BIRTH(bp) > dsl_dataset_phys(ds)->ds_prev_snap_txg) {
                int64_t delta;

                /*
                 * Put blocks that would create IO on the pool's deadlist for
                 * dsl_process_async_destroys() to find. This is to prevent
                 * zio_free() from creating a ZIO_TYPE_FREE IO for them, which
                 * are very heavy and can lead to out-of-memory conditions if
                 * something tries to free millions of blocks on the same txg.
                 */
                boolean_t defer = spa_version(spa) >= SPA_VERSION_DEADLISTS &&
                    (BP_IS_GANG(bp) || BP_GET_DEDUP(bp) ||
                    brt_maybe_exists(spa, bp));

                if (defer) {
                        dprintf_bp(bp, "putting on free list: %s", "");
                        bpobj_enqueue(&ds->ds_dir->dd_pool->dp_free_bpobj,
                            bp, B_FALSE, tx);
                } else {
                        dprintf_bp(bp, "freeing ds=%llu",
                            (u_longlong_t)ds->ds_object);
                        dsl_free(tx->tx_pool, tx->tx_txg, bp);
                }

                mutex_enter(&ds->ds_lock);
                ASSERT(dsl_dataset_phys(ds)->ds_unique_bytes >= used ||
                    !DS_UNIQUE_IS_ACCURATE(ds));
                delta = parent_delta(ds, -used);
                dsl_dataset_phys(ds)->ds_unique_bytes -= used;
                mutex_exit(&ds->ds_lock);

                dsl_dir_diduse_transfer_space(ds->ds_dir,
                    delta, -compressed, -uncompressed, -used,
                    DD_USED_REFRSRV, DD_USED_HEAD, tx);

                if (defer)
                        dsl_dir_diduse_space(tx->tx_pool->dp_free_dir,
                            DD_USED_HEAD, used, compressed, uncompressed, tx);
        } else {
                dprintf_bp(bp, "putting on dead list: %s", "");
                if (async) {
                        /*
                         * We are here as part of zio's write done callback,
                         * which means we're a zio interrupt thread.  We can't
                         * call dsl_deadlist_insert() now because it may block
                         * waiting for I/O.  Instead, put bp on the deferred
                         * queue and let dsl_pool_sync() finish the job.
                         */
                        bplist_append(&ds->ds_pending_deadlist, bp);
                } else {
                        dsl_deadlist_insert(&ds->ds_deadlist, bp, B_FALSE, tx);
                }
                ASSERT3U(ds->ds_prev->ds_object, ==,
                    dsl_dataset_phys(ds)->ds_prev_snap_obj);
                ASSERT(dsl_dataset_phys(ds->ds_prev)->ds_num_children > 0);
                /* if (logical birth > prev prev snap txg) prev unique += bs */
                if (dsl_dataset_phys(ds->ds_prev)->ds_next_snap_obj ==
                    ds->ds_object && BP_GET_LOGICAL_BIRTH(bp) >
                    dsl_dataset_phys(ds->ds_prev)->ds_prev_snap_txg) {
                        dmu_buf_will_dirty(ds->ds_prev->ds_dbuf, tx);
                        mutex_enter(&ds->ds_prev->ds_lock);
                        dsl_dataset_phys(ds->ds_prev)->ds_unique_bytes += used;
                        mutex_exit(&ds->ds_prev->ds_lock);
                }
                if (BP_GET_LOGICAL_BIRTH(bp) > ds->ds_dir->dd_origin_txg) {
                        dsl_dir_transfer_space(ds->ds_dir, used,
                            DD_USED_HEAD, DD_USED_SNAP, tx);
                }
        }

        dsl_bookmark_block_killed(ds, bp, tx);

        mutex_enter(&ds->ds_lock);
        ASSERT3U(dsl_dataset_phys(ds)->ds_referenced_bytes, >=, used);
        dsl_dataset_phys(ds)->ds_referenced_bytes -= used;
        ASSERT3U(dsl_dataset_phys(ds)->ds_compressed_bytes, >=, compressed);
        dsl_dataset_phys(ds)->ds_compressed_bytes -= compressed;
        ASSERT3U(dsl_dataset_phys(ds)->ds_uncompressed_bytes, >=, uncompressed);
        dsl_dataset_phys(ds)->ds_uncompressed_bytes -= uncompressed;
        mutex_exit(&ds->ds_lock);

        return (used);
}

struct feature_type_uint64_array_arg {
        uint64_t length;
        uint64_t *array;
};

static void
unload_zfeature(dsl_dataset_t *ds, spa_feature_t f)
{
        switch (spa_feature_table[f].fi_type) {
        case ZFEATURE_TYPE_BOOLEAN:
                break;
        case ZFEATURE_TYPE_UINT64_ARRAY:
        {
                struct feature_type_uint64_array_arg *ftuaa = ds->ds_feature[f];
                kmem_free(ftuaa->array, ftuaa->length * sizeof (uint64_t));
                kmem_free(ftuaa, sizeof (*ftuaa));
                break;
        }
        default:
                panic("Invalid zfeature type %d", spa_feature_table[f].fi_type);
        }
}

static int
load_zfeature(objset_t *mos, dsl_dataset_t *ds, spa_feature_t f)
{
        int err = 0;
        switch (spa_feature_table[f].fi_type) {
        case ZFEATURE_TYPE_BOOLEAN:
                err = zap_contains(mos, ds->ds_object,
                    spa_feature_table[f].fi_guid);
                if (err == 0) {
                        ds->ds_feature[f] = (void *)B_TRUE;
                } else {
                        ASSERT3U(err, ==, ENOENT);
                        err = 0;
                }
                break;
        case ZFEATURE_TYPE_UINT64_ARRAY:
        {
                uint64_t int_size, num_int;
                uint64_t *data;
                err = zap_length(mos, ds->ds_object,
                    spa_feature_table[f].fi_guid, &int_size, &num_int);
                if (err != 0) {
                        ASSERT3U(err, ==, ENOENT);
                        err = 0;
                        break;
                }
                ASSERT3U(int_size, ==, sizeof (uint64_t));
                data = kmem_alloc(int_size * num_int, KM_SLEEP);
                VERIFY0(zap_lookup(mos, ds->ds_object,
                    spa_feature_table[f].fi_guid, int_size, num_int, data));
                struct feature_type_uint64_array_arg *ftuaa =
                    kmem_alloc(sizeof (*ftuaa), KM_SLEEP);
                ftuaa->length = num_int;
                ftuaa->array = data;
                ds->ds_feature[f] = ftuaa;
                break;
        }
        default:
                panic("Invalid zfeature type %d", spa_feature_table[f].fi_type);
        }
        return (err);
}

/*
 * We have to release the fsid synchronously or we risk that a subsequent
 * mount of the same dataset will fail to unique_insert the fsid.  This
 * failure would manifest itself as the fsid of this dataset changing
 * between mounts which makes NFS clients quite unhappy.
 */
static void
dsl_dataset_evict_sync(void *dbu)
{
        dsl_dataset_t *ds = dbu;

        ASSERT(ds->ds_owner == NULL);

        unique_remove(ds->ds_fsid_guid);
}

static void
dsl_dataset_evict_async(void *dbu)
{
        dsl_dataset_t *ds = dbu;

        ASSERT(ds->ds_owner == NULL);

        ds->ds_dbuf = NULL;

        if (ds->ds_objset != NULL)
                dmu_objset_evict(ds->ds_objset);

        if (ds->ds_prev) {
                dsl_dataset_rele(ds->ds_prev, ds);
                ds->ds_prev = NULL;
        }

        dsl_bookmark_fini_ds(ds);

        bplist_destroy(&ds->ds_pending_deadlist);
        if (dsl_deadlist_is_open(&ds->ds_deadlist))
                dsl_deadlist_close(&ds->ds_deadlist);
        if (dsl_deadlist_is_open(&ds->ds_remap_deadlist))
                dsl_deadlist_close(&ds->ds_remap_deadlist);
        if (ds->ds_dir)
                dsl_dir_async_rele(ds->ds_dir, ds);

        ASSERT(!list_link_active(&ds->ds_synced_link));

        for (spa_feature_t f = 0; f < SPA_FEATURES; f++) {
                if (dsl_dataset_feature_is_active(ds, f))
                        unload_zfeature(ds, f);
        }

        list_destroy(&ds->ds_prop_cbs);
        mutex_destroy(&ds->ds_lock);
        mutex_destroy(&ds->ds_opening_lock);
        mutex_destroy(&ds->ds_sendstream_lock);
        mutex_destroy(&ds->ds_remap_deadlist_lock);
        zfs_refcount_destroy(&ds->ds_longholds);
        rrw_destroy(&ds->ds_bp_rwlock);

        kmem_free(ds, sizeof (dsl_dataset_t));
}

int
dsl_dataset_get_snapname(dsl_dataset_t *ds)
{
        dsl_dataset_phys_t *headphys;
        int err;
        dmu_buf_t *headdbuf;
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        objset_t *mos = dp->dp_meta_objset;

        if (ds->ds_snapname[0])
                return (0);
        if (dsl_dataset_phys(ds)->ds_next_snap_obj == 0)
                return (0);

        err = dmu_bonus_hold(mos, dsl_dir_phys(ds->ds_dir)->dd_head_dataset_obj,
            FTAG, &headdbuf);
        if (err != 0)
                return (err);
        headphys = headdbuf->db_data;
        err = zap_value_search(dp->dp_meta_objset,
            headphys->ds_snapnames_zapobj, ds->ds_object, 0, ds->ds_snapname,
            sizeof (ds->ds_snapname));
        if (err != 0 && zfs_recover == B_TRUE) {
                err = 0;
                (void) snprintf(ds->ds_snapname, sizeof (ds->ds_snapname),
                    "SNAPOBJ=%llu-ERR=%d",
                    (unsigned long long)ds->ds_object, err);
        }
        dmu_buf_rele(headdbuf, FTAG);
        return (err);
}

int
dsl_dataset_snap_lookup(dsl_dataset_t *ds, const char *name, uint64_t *value)
{
        objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
        uint64_t snapobj = dsl_dataset_phys(ds)->ds_snapnames_zapobj;
        matchtype_t mt = 0;
        int err;

        if (dsl_dataset_phys(ds)->ds_flags & DS_FLAG_CI_DATASET)
                mt = MT_NORMALIZE;

        err = zap_lookup_norm(mos, snapobj, name, 8, 1,
            value, mt, NULL, 0, NULL);
        if (err == ENOTSUP && (mt & MT_NORMALIZE))
                err = zap_lookup(mos, snapobj, name, 8, 1, value);
        return (err);
}

int
dsl_dataset_snap_remove(dsl_dataset_t *ds, const char *name, dmu_tx_t *tx,
    boolean_t adj_cnt)
{
        objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
        uint64_t snapobj = dsl_dataset_phys(ds)->ds_snapnames_zapobj;
        matchtype_t mt = 0;
        int err;

        dsl_dir_snap_cmtime_update(ds->ds_dir, tx);

        if (dsl_dataset_phys(ds)->ds_flags & DS_FLAG_CI_DATASET)
                mt = MT_NORMALIZE;

        err = zap_remove_norm(mos, snapobj, name, mt, tx);
        if (err == ENOTSUP && (mt & MT_NORMALIZE))
                err = zap_remove(mos, snapobj, name, tx);

        if (err == 0 && adj_cnt)
                dsl_fs_ss_count_adjust(ds->ds_dir, -1,
                    DD_FIELD_SNAPSHOT_COUNT, tx);

        return (err);
}

boolean_t
dsl_dataset_try_add_ref(dsl_pool_t *dp, dsl_dataset_t *ds, const void *tag)
{
        dmu_buf_t *dbuf = ds->ds_dbuf;
        boolean_t result = B_FALSE;

        if (dbuf != NULL && dmu_buf_try_add_ref(dbuf, dp->dp_meta_objset,
            ds->ds_object, DMU_BONUS_BLKID, tag)) {

                if (ds == dmu_buf_get_user(dbuf))
                        result = B_TRUE;
                else
                        dmu_buf_rele(dbuf, tag);
        }

        return (result);
}

int
dsl_dataset_hold_obj(dsl_pool_t *dp, uint64_t dsobj, const void *tag,
    dsl_dataset_t **dsp)
{
        objset_t *mos = dp->dp_meta_objset;
        dmu_buf_t *dbuf;
        dsl_dataset_t *ds;
        int err;
        dmu_object_info_t doi;

        ASSERT(dsl_pool_config_held(dp));

        err = dmu_bonus_hold(mos, dsobj, tag, &dbuf);
        if (err != 0)
                return (err);

        /* Make sure dsobj has the correct object type. */
        dmu_object_info_from_db(dbuf, &doi);
        if (doi.doi_bonus_type != DMU_OT_DSL_DATASET) {
                dmu_buf_rele(dbuf, tag);
                return (SET_ERROR(EINVAL));
        }

        ds = dmu_buf_get_user(dbuf);
        if (ds == NULL) {
                dsl_dataset_t *winner = NULL;

                ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
                ds->ds_dbuf = dbuf;
                ds->ds_object = dsobj;
                ds->ds_is_snapshot = dsl_dataset_phys(ds)->ds_num_children != 0;
                list_link_init(&ds->ds_synced_link);

                err = dsl_dir_hold_obj(dp, dsl_dataset_phys(ds)->ds_dir_obj,
                    NULL, ds, &ds->ds_dir);
                if (err != 0) {
                        kmem_free(ds, sizeof (dsl_dataset_t));
                        dmu_buf_rele(dbuf, tag);
                        return (err);
                }

                mutex_init(&ds->ds_lock, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&ds->ds_opening_lock, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&ds->ds_sendstream_lock, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&ds->ds_remap_deadlist_lock,
                    NULL, MUTEX_DEFAULT, NULL);
                rrw_init(&ds->ds_bp_rwlock, B_FALSE);
                zfs_refcount_create(&ds->ds_longholds);

                bplist_create(&ds->ds_pending_deadlist);

                list_create(&ds->ds_sendstreams, sizeof (dmu_sendstatus_t),
                    offsetof(dmu_sendstatus_t, dss_link));

                list_create(&ds->ds_prop_cbs, sizeof (dsl_prop_cb_record_t),
                    offsetof(dsl_prop_cb_record_t, cbr_ds_node));

                if (doi.doi_type == DMU_OTN_ZAP_METADATA) {
                        spa_feature_t f;

                        for (f = 0; f < SPA_FEATURES; f++) {
                                if (!(spa_feature_table[f].fi_flags &
                                    ZFEATURE_FLAG_PER_DATASET))
                                        continue;
                                err = load_zfeature(mos, ds, f);
                        }
                }

                if (!ds->ds_is_snapshot) {
                        ds->ds_snapname[0] = '\0';
                        if (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0) {
                                err = dsl_dataset_hold_obj(dp,
                                    dsl_dataset_phys(ds)->ds_prev_snap_obj,
                                    ds, &ds->ds_prev);
                        }
                        if (err != 0)
                                goto after_dsl_bookmark_fini;
                        err = dsl_bookmark_init_ds(ds);
                } else {
                        if (zfs_flags & ZFS_DEBUG_SNAPNAMES)
                                err = dsl_dataset_get_snapname(ds);
                        if (err == 0 &&
                            dsl_dataset_phys(ds)->ds_userrefs_obj != 0) {
                                err = zap_count(
                                    ds->ds_dir->dd_pool->dp_meta_objset,
                                    dsl_dataset_phys(ds)->ds_userrefs_obj,
                                    &ds->ds_userrefs);
                        }
                }

                if (err == 0 && !ds->ds_is_snapshot) {
                        err = dsl_prop_get_int_ds(ds,
                            zfs_prop_to_name(ZFS_PROP_REFRESERVATION),
                            &ds->ds_reserved);
                        if (err == 0) {
                                err = dsl_prop_get_int_ds(ds,
                                    zfs_prop_to_name(ZFS_PROP_REFQUOTA),
                                    &ds->ds_quota);
                        }
                } else {
                        ds->ds_reserved = ds->ds_quota = 0;
                }

                if (err == 0 && ds->ds_dir->dd_crypto_obj != 0 &&
                    ds->ds_is_snapshot &&
                    zap_contains(mos, dsobj, DS_FIELD_IVSET_GUID) != 0) {
                        dp->dp_spa->spa_errata =
                            ZPOOL_ERRATA_ZOL_8308_ENCRYPTION;
                }

                if (err == 0) {
                        err = dsl_deadlist_open(&ds->ds_deadlist,
                            mos, dsl_dataset_phys(ds)->ds_deadlist_obj);
                }
                if (err == 0) {
                        uint64_t remap_deadlist_obj =
                            dsl_dataset_get_remap_deadlist_object(ds);
                        if (remap_deadlist_obj != 0) {
                                err = dsl_deadlist_open(&ds->ds_remap_deadlist,
                                    mos, remap_deadlist_obj);
                        }
                }

                dmu_buf_init_user(&ds->ds_dbu, dsl_dataset_evict_sync,
                    dsl_dataset_evict_async, &ds->ds_dbuf);
                if (err == 0)
                        winner = dmu_buf_set_user_ie(dbuf, &ds->ds_dbu);

                if (err != 0 || winner != NULL) {
                        if (dsl_deadlist_is_open(&ds->ds_deadlist))
                                dsl_deadlist_close(&ds->ds_deadlist);
                        if (dsl_deadlist_is_open(&ds->ds_remap_deadlist))
                                dsl_deadlist_close(&ds->ds_remap_deadlist);
                        dsl_bookmark_fini_ds(ds);
after_dsl_bookmark_fini:
                        if (ds->ds_prev)
                                dsl_dataset_rele(ds->ds_prev, ds);
                        dsl_dir_rele(ds->ds_dir, ds);
                        for (spa_feature_t f = 0; f < SPA_FEATURES; f++) {
                                if (dsl_dataset_feature_is_active(ds, f))
                                        unload_zfeature(ds, f);
                        }

                        list_destroy(&ds->ds_prop_cbs);
                        list_destroy(&ds->ds_sendstreams);
                        bplist_destroy(&ds->ds_pending_deadlist);
                        mutex_destroy(&ds->ds_lock);
                        mutex_destroy(&ds->ds_opening_lock);
                        mutex_destroy(&ds->ds_sendstream_lock);
                        mutex_destroy(&ds->ds_remap_deadlist_lock);
                        zfs_refcount_destroy(&ds->ds_longholds);
                        rrw_destroy(&ds->ds_bp_rwlock);
                        kmem_free(ds, sizeof (dsl_dataset_t));
                        if (err != 0) {
                                dmu_buf_rele(dbuf, tag);
                                return (err);
                        }
                        ds = winner;
                } else {
                        ds->ds_fsid_guid =
                            unique_insert(dsl_dataset_phys(ds)->ds_fsid_guid);
                        if (ds->ds_fsid_guid !=
                            dsl_dataset_phys(ds)->ds_fsid_guid) {
                                zfs_dbgmsg("ds_fsid_guid changed from "
                                    "%llx to %llx for pool %s dataset id %llu",
                                    (long long)
                                    dsl_dataset_phys(ds)->ds_fsid_guid,
                                    (long long)ds->ds_fsid_guid,
                                    spa_name(dp->dp_spa),
                                    (u_longlong_t)dsobj);
                        }
                }
        }

        ASSERT3P(ds->ds_dbuf, ==, dbuf);
        ASSERT3P(dsl_dataset_phys(ds), ==, dbuf->db_data);
        ASSERT(dsl_dataset_phys(ds)->ds_prev_snap_obj != 0 ||
            spa_version(dp->dp_spa) < SPA_VERSION_ORIGIN ||
            dp->dp_origin_snap == NULL || ds == dp->dp_origin_snap);
        *dsp = ds;

        return (0);
}

int
dsl_dataset_create_key_mapping(dsl_dataset_t *ds)
{
        dsl_dir_t *dd = ds->ds_dir;

        if (dd->dd_crypto_obj == 0)
                return (0);

        return (spa_keystore_create_mapping(dd->dd_pool->dp_spa,
            ds, ds, &ds->ds_key_mapping));
}

int
dsl_dataset_hold_obj_flags(dsl_pool_t *dp, uint64_t dsobj,
    ds_hold_flags_t flags, const void *tag, dsl_dataset_t **dsp)
{
        int err;

        err = dsl_dataset_hold_obj(dp, dsobj, tag, dsp);
        if (err != 0)
                return (err);

        ASSERT3P(*dsp, !=, NULL);

        if (flags & DS_HOLD_FLAG_DECRYPT) {
                err = dsl_dataset_create_key_mapping(*dsp);
                if (err != 0)
                        dsl_dataset_rele(*dsp, tag);
        }

        return (err);
}

int
dsl_dataset_hold_flags(dsl_pool_t *dp, const char *name, ds_hold_flags_t flags,
    const void *tag, dsl_dataset_t **dsp)
{
        dsl_dir_t *dd;
        const char *snapname;
        uint64_t obj;
        int err = 0;
        dsl_dataset_t *ds;

        err = dsl_dir_hold(dp, name, FTAG, &dd, &snapname);
        if (err != 0)
                return (err);

        ASSERT(dsl_pool_config_held(dp));
        obj = dsl_dir_phys(dd)->dd_head_dataset_obj;
        if (obj != 0)
                err = dsl_dataset_hold_obj_flags(dp, obj, flags, tag, &ds);
        else
                err = SET_ERROR(ENOENT);

        /* we may be looking for a snapshot */
        if (err == 0 && snapname != NULL) {
                dsl_dataset_t *snap_ds;

                if (*snapname++ != '@') {
                        dsl_dataset_rele_flags(ds, flags, tag);
                        dsl_dir_rele(dd, FTAG);
                        return (SET_ERROR(ENOENT));
                }

                dprintf("looking for snapshot '%s'\n", snapname);
                err = dsl_dataset_snap_lookup(ds, snapname, &obj);
                if (err == 0) {
                        err = dsl_dataset_hold_obj_flags(dp, obj, flags, tag,
                            &snap_ds);
                }
                dsl_dataset_rele_flags(ds, flags, tag);

                if (err == 0) {
                        mutex_enter(&snap_ds->ds_lock);
                        if (snap_ds->ds_snapname[0] == 0)
                                (void) strlcpy(snap_ds->ds_snapname, snapname,
                                    sizeof (snap_ds->ds_snapname));
                        mutex_exit(&snap_ds->ds_lock);
                        ds = snap_ds;
                }
        }
        if (err == 0)
                *dsp = ds;
        dsl_dir_rele(dd, FTAG);
        return (err);
}

int
dsl_dataset_hold(dsl_pool_t *dp, const char *name, const void *tag,
    dsl_dataset_t **dsp)
{
        return (dsl_dataset_hold_flags(dp, name, 0, tag, dsp));
}

static int
dsl_dataset_own_obj_impl(dsl_pool_t *dp, uint64_t dsobj, ds_hold_flags_t flags,
    const void *tag, boolean_t override, dsl_dataset_t **dsp)
{
        int err = dsl_dataset_hold_obj_flags(dp, dsobj, flags, tag, dsp);
        if (err != 0)
                return (err);
        if (!dsl_dataset_tryown(*dsp, tag, override)) {
                dsl_dataset_rele_flags(*dsp, flags, tag);
                *dsp = NULL;
                return (SET_ERROR(EBUSY));
        }
        return (0);
}


int
dsl_dataset_own_obj(dsl_pool_t *dp, uint64_t dsobj, ds_hold_flags_t flags,
    const void *tag, dsl_dataset_t **dsp)
{
        return (dsl_dataset_own_obj_impl(dp, dsobj, flags, tag, B_FALSE, dsp));
}

int
dsl_dataset_own_obj_force(dsl_pool_t *dp, uint64_t dsobj,
    ds_hold_flags_t flags, const void *tag, dsl_dataset_t **dsp)
{
        return (dsl_dataset_own_obj_impl(dp, dsobj, flags, tag, B_TRUE, dsp));
}

static int
dsl_dataset_own_impl(dsl_pool_t *dp, const char *name, ds_hold_flags_t flags,
    const void *tag, boolean_t override, dsl_dataset_t **dsp)
{
        int err = dsl_dataset_hold_flags(dp, name, flags, tag, dsp);
        if (err != 0)
                return (err);
        if (!dsl_dataset_tryown(*dsp, tag, override)) {
                dsl_dataset_rele_flags(*dsp, flags, tag);
                return (SET_ERROR(EBUSY));
        }
        return (0);
}

int
dsl_dataset_own_force(dsl_pool_t *dp, const char *name, ds_hold_flags_t flags,
    const void *tag, dsl_dataset_t **dsp)
{
        return (dsl_dataset_own_impl(dp, name, flags, tag, B_TRUE, dsp));
}

int
dsl_dataset_own(dsl_pool_t *dp, const char *name, ds_hold_flags_t flags,
    const void *tag, dsl_dataset_t **dsp)
{
        return (dsl_dataset_own_impl(dp, name, flags, tag, B_FALSE, dsp));
}

/*
 * See the comment above dsl_pool_hold() for details.  In summary, a long
 * hold is used to prevent destruction of a dataset while the pool hold
 * is dropped, allowing other concurrent operations (e.g. spa_sync()).
 *
 * The dataset and pool must be held when this function is called.  After it
 * is called, the pool hold may be released while the dataset is still held
 * and accessed.
 */
void
dsl_dataset_long_hold(dsl_dataset_t *ds, const void *tag)
{
        ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
        (void) zfs_refcount_add(&ds->ds_longholds, tag);
}

void
dsl_dataset_long_rele(dsl_dataset_t *ds, const void *tag)
{
        (void) zfs_refcount_remove(&ds->ds_longholds, tag);
}

/* Return B_TRUE if there are any long holds on this dataset. */
boolean_t
dsl_dataset_long_held(dsl_dataset_t *ds)
{
        return (!zfs_refcount_is_zero(&ds->ds_longholds));
}

void
dsl_dataset_name(dsl_dataset_t *ds, char *name)
{
        if (ds == NULL) {
                (void) strlcpy(name, "mos", ZFS_MAX_DATASET_NAME_LEN);
        } else {
                dsl_dir_name(ds->ds_dir, name);
                VERIFY0(dsl_dataset_get_snapname(ds));
                if (ds->ds_snapname[0]) {
                        VERIFY3U(strlcat(name, "@", ZFS_MAX_DATASET_NAME_LEN),
                            <, ZFS_MAX_DATASET_NAME_LEN);
                        /*
                         * We use a "recursive" mutex so that we
                         * can call dprintf_ds() with ds_lock held.
                         */
                        if (!MUTEX_HELD(&ds->ds_lock)) {
                                mutex_enter(&ds->ds_lock);
                                VERIFY3U(strlcat(name, ds->ds_snapname,
                                    ZFS_MAX_DATASET_NAME_LEN), <,
                                    ZFS_MAX_DATASET_NAME_LEN);
                                mutex_exit(&ds->ds_lock);
                        } else {
                                VERIFY3U(strlcat(name, ds->ds_snapname,
                                    ZFS_MAX_DATASET_NAME_LEN), <,
                                    ZFS_MAX_DATASET_NAME_LEN);
                        }
                }
        }
}

int
dsl_dataset_namelen(dsl_dataset_t *ds)
{
        VERIFY0(dsl_dataset_get_snapname(ds));
        mutex_enter(&ds->ds_lock);
        int len = strlen(ds->ds_snapname);
        mutex_exit(&ds->ds_lock);
        /* add '@' if ds is a snap */
        if (len > 0)
                len++;
        len += dsl_dir_namelen(ds->ds_dir);
        return (len);
}

void
dsl_dataset_rele(dsl_dataset_t *ds, const void *tag)
{
        dmu_buf_rele(ds->ds_dbuf, tag);
}

void
dsl_dataset_remove_key_mapping(dsl_dataset_t *ds)
{
        dsl_dir_t *dd = ds->ds_dir;

        if (dd == NULL || dd->dd_crypto_obj == 0)
                return;

        (void) spa_keystore_remove_mapping(dd->dd_pool->dp_spa,
            ds->ds_object, ds);
}

void
dsl_dataset_rele_flags(dsl_dataset_t *ds, ds_hold_flags_t flags,
    const void *tag)
{
        if (flags & DS_HOLD_FLAG_DECRYPT)
                dsl_dataset_remove_key_mapping(ds);

        dsl_dataset_rele(ds, tag);
}

void
dsl_dataset_disown(dsl_dataset_t *ds, ds_hold_flags_t flags, const void *tag)
{
        ASSERT3P(ds->ds_owner, ==, tag);
        ASSERT(ds->ds_dbuf != NULL);

        mutex_enter(&ds->ds_lock);
        ds->ds_owner = NULL;
        mutex_exit(&ds->ds_lock);
        dsl_dataset_long_rele(ds, tag);
        dsl_dataset_rele_flags(ds, flags, tag);
}

boolean_t
dsl_dataset_tryown(dsl_dataset_t *ds, const void *tag, boolean_t override)
{
        boolean_t gotit = FALSE;

        ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
        mutex_enter(&ds->ds_lock);
        if (ds->ds_owner == NULL && (override || !(DS_IS_INCONSISTENT(ds) ||
            (dsl_dataset_feature_is_active(ds,
            SPA_FEATURE_REDACTED_DATASETS) &&
            !zfs_allow_redacted_dataset_mount)))) {
                ds->ds_owner = tag;
                dsl_dataset_long_hold(ds, tag);
                gotit = TRUE;
        }
        mutex_exit(&ds->ds_lock);
        return (gotit);
}

boolean_t
dsl_dataset_has_owner(dsl_dataset_t *ds)
{
        boolean_t rv;
        mutex_enter(&ds->ds_lock);
        rv = (ds->ds_owner != NULL);
        mutex_exit(&ds->ds_lock);
        return (rv);
}

static boolean_t
zfeature_active(spa_feature_t f, void *arg)
{
        switch (spa_feature_table[f].fi_type) {
        case ZFEATURE_TYPE_BOOLEAN: {
                boolean_t val = (boolean_t)(uintptr_t)arg;
                ASSERT(val == B_FALSE || val == B_TRUE);
                return (val);
        }
        case ZFEATURE_TYPE_UINT64_ARRAY:
                /*
                 * In this case, arg is a uint64_t array.  The feature is active
                 * if the array is non-null.
                 */
                return (arg != NULL);
        default:
                panic("Invalid zfeature type %d", spa_feature_table[f].fi_type);
                return (B_FALSE);
        }
}

boolean_t
dsl_dataset_feature_is_active(dsl_dataset_t *ds, spa_feature_t f)
{
        return (zfeature_active(f, ds->ds_feature[f]));
}

/*
 * The buffers passed out by this function are references to internal buffers;
 * they should not be freed by callers of this function, and they should not be
 * used after the dataset has been released.
 */
boolean_t
dsl_dataset_get_uint64_array_feature(dsl_dataset_t *ds, spa_feature_t f,
    uint64_t *outlength, uint64_t **outp)
{
        VERIFY(spa_feature_table[f].fi_type & ZFEATURE_TYPE_UINT64_ARRAY);
        if (!dsl_dataset_feature_is_active(ds, f)) {
                return (B_FALSE);
        }
        struct feature_type_uint64_array_arg *ftuaa = ds->ds_feature[f];
        *outp = ftuaa->array;
        *outlength = ftuaa->length;
        return (B_TRUE);
}

void
dsl_dataset_activate_feature(uint64_t dsobj, spa_feature_t f, void *arg,
    dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;
        objset_t *mos = dmu_tx_pool(tx)->dp_meta_objset;
        uint64_t zero = 0;

        VERIFY(spa_feature_table[f].fi_flags & ZFEATURE_FLAG_PER_DATASET);

        spa_feature_incr(spa, f, tx);
        dmu_object_zapify(mos, dsobj, DMU_OT_DSL_DATASET, tx);

        switch (spa_feature_table[f].fi_type) {
        case ZFEATURE_TYPE_BOOLEAN:
                ASSERT3S((boolean_t)(uintptr_t)arg, ==, B_TRUE);
                VERIFY0(zap_add(mos, dsobj, spa_feature_table[f].fi_guid,
                    sizeof (zero), 1, &zero, tx));
                break;
        case ZFEATURE_TYPE_UINT64_ARRAY:
        {
                struct feature_type_uint64_array_arg *ftuaa = arg;
                VERIFY0(zap_add(mos, dsobj, spa_feature_table[f].fi_guid,
                    sizeof (uint64_t), ftuaa->length, ftuaa->array, tx));
                break;
        }
        default:
                panic("Invalid zfeature type %d", spa_feature_table[f].fi_type);
        }
}

static void
dsl_dataset_deactivate_feature_impl(dsl_dataset_t *ds, spa_feature_t f,
    dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;
        objset_t *mos = dmu_tx_pool(tx)->dp_meta_objset;
        uint64_t dsobj = ds->ds_object;

        VERIFY(spa_feature_table[f].fi_flags & ZFEATURE_FLAG_PER_DATASET);

        VERIFY0(zap_remove(mos, dsobj, spa_feature_table[f].fi_guid, tx));
        spa_feature_decr(spa, f, tx);
        ds->ds_feature[f] = NULL;
}

void
dsl_dataset_deactivate_feature(dsl_dataset_t *ds, spa_feature_t f, dmu_tx_t *tx)
{
        unload_zfeature(ds, f);
        dsl_dataset_deactivate_feature_impl(ds, f, tx);
}

uint64_t
dsl_dataset_create_sync_dd(dsl_dir_t *dd, dsl_dataset_t *origin,
    dsl_crypto_params_t *dcp, uint64_t flags, dmu_tx_t *tx)
{
        dsl_pool_t *dp = dd->dd_pool;
        dmu_buf_t *dbuf;
        dsl_dataset_phys_t *dsphys;
        uint64_t dsobj;
        objset_t *mos = dp->dp_meta_objset;

        if (origin == NULL)
                origin = dp->dp_origin_snap;

        ASSERT(origin == NULL || origin->ds_dir->dd_pool == dp);
        ASSERT(origin == NULL || dsl_dataset_phys(origin)->ds_num_children > 0);
        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(dsl_dir_phys(dd)->dd_head_dataset_obj == 0);

        dsobj = dmu_object_alloc(mos, DMU_OT_DSL_DATASET, 0,
            DMU_OT_DSL_DATASET, sizeof (dsl_dataset_phys_t), tx);
        VERIFY0(dmu_bonus_hold(mos, dsobj, FTAG, &dbuf));
        dmu_buf_will_dirty(dbuf, tx);
        dsphys = dbuf->db_data;
        memset(dsphys, 0, sizeof (dsl_dataset_phys_t));
        dsphys->ds_dir_obj = dd->dd_object;
        dsphys->ds_flags = flags;
        dsphys->ds_fsid_guid = unique_create();
        (void) random_get_pseudo_bytes((void*)&dsphys->ds_guid,
            sizeof (dsphys->ds_guid));
        dsphys->ds_snapnames_zapobj =
            zap_create_norm(mos, U8_TEXTPREP_TOUPPER, DMU_OT_DSL_DS_SNAP_MAP,
            DMU_OT_NONE, 0, tx);
        dsphys->ds_creation_time = gethrestime_sec();
        dsphys->ds_creation_txg = tx->tx_txg == TXG_INITIAL ? 1 : tx->tx_txg;

        if (origin == NULL) {
                dsphys->ds_deadlist_obj = dsl_deadlist_alloc(mos, tx);
        } else {
                dsl_dataset_t *ohds; /* head of the origin snapshot */

                dsphys->ds_prev_snap_obj = origin->ds_object;
                dsphys->ds_prev_snap_txg =
                    dsl_dataset_phys(origin)->ds_creation_txg;
                dsphys->ds_referenced_bytes =
                    dsl_dataset_phys(origin)->ds_referenced_bytes;
                dsphys->ds_compressed_bytes =
                    dsl_dataset_phys(origin)->ds_compressed_bytes;
                dsphys->ds_uncompressed_bytes =
                    dsl_dataset_phys(origin)->ds_uncompressed_bytes;
                rrw_enter(&origin->ds_bp_rwlock, RW_READER, FTAG);
                dsphys->ds_bp = dsl_dataset_phys(origin)->ds_bp;
                rrw_exit(&origin->ds_bp_rwlock, FTAG);

                /*
                 * Inherit flags that describe the dataset's contents
                 * (INCONSISTENT) or properties (Case Insensitive).
                 */
                dsphys->ds_flags |= dsl_dataset_phys(origin)->ds_flags &
                    (DS_FLAG_INCONSISTENT | DS_FLAG_CI_DATASET);

                for (spa_feature_t f = 0; f < SPA_FEATURES; f++) {
                        if (zfeature_active(f, origin->ds_feature[f])) {
                                dsl_dataset_activate_feature(dsobj, f,
                                    origin->ds_feature[f], tx);
                        }
                }

                dmu_buf_will_dirty(origin->ds_dbuf, tx);
                dsl_dataset_phys(origin)->ds_num_children++;

                VERIFY0(dsl_dataset_hold_obj(dp,
                    dsl_dir_phys(origin->ds_dir)->dd_head_dataset_obj,
                    FTAG, &ohds));
                dsphys->ds_deadlist_obj = dsl_deadlist_clone(&ohds->ds_deadlist,
                    dsphys->ds_prev_snap_txg, dsphys->ds_prev_snap_obj, tx);
                dsl_dataset_rele(ohds, FTAG);

                if (spa_version(dp->dp_spa) >= SPA_VERSION_NEXT_CLONES) {
                        if (dsl_dataset_phys(origin)->ds_next_clones_obj == 0) {
                                dsl_dataset_phys(origin)->ds_next_clones_obj =
                                    zap_create(mos,
                                    DMU_OT_NEXT_CLONES, DMU_OT_NONE, 0, tx);
                        }
                        VERIFY0(zap_add_int(mos,
                            dsl_dataset_phys(origin)->ds_next_clones_obj,
                            dsobj, tx));
                }

                dmu_buf_will_dirty(dd->dd_dbuf, tx);
                dsl_dir_phys(dd)->dd_origin_obj = origin->ds_object;
                if (spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
                        if (dsl_dir_phys(origin->ds_dir)->dd_clones == 0) {
                                dmu_buf_will_dirty(origin->ds_dir->dd_dbuf, tx);
                                dsl_dir_phys(origin->ds_dir)->dd_clones =
                                    zap_create(mos,
                                    DMU_OT_DSL_CLONES, DMU_OT_NONE, 0, tx);
                        }
                        VERIFY0(zap_add_int(mos,
                            dsl_dir_phys(origin->ds_dir)->dd_clones,
                            dsobj, tx));
                }
        }

        /* handle encryption */
        dsl_dataset_create_crypt_sync(dsobj, dd, origin, dcp, tx);

        if (spa_version(dp->dp_spa) >= SPA_VERSION_UNIQUE_ACCURATE)
                dsphys->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;

        dmu_buf_rele(dbuf, FTAG);

        dmu_buf_will_dirty(dd->dd_dbuf, tx);
        dsl_dir_phys(dd)->dd_head_dataset_obj = dsobj;

        return (dsobj);
}

static void
dsl_dataset_zero_zil(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        objset_t *os;

        VERIFY0(dmu_objset_from_ds(ds, &os));
        if (memcmp(&os->os_zil_header, &zero_zil, sizeof (zero_zil)) != 0) {
                dsl_pool_t *dp = ds->ds_dir->dd_pool;
                zio_t *zio;

                memset(&os->os_zil_header, 0, sizeof (os->os_zil_header));
                if (os->os_encrypted)
                        os->os_next_write_raw[tx->tx_txg & TXG_MASK] = B_TRUE;

                zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
                dsl_dataset_sync(ds, zio, tx);
                VERIFY0(zio_wait(zio));
                dsl_dataset_sync_done(ds, tx);
        }
}

uint64_t
dsl_dataset_create_sync(dsl_dir_t *pdd, const char *lastname,
    dsl_dataset_t *origin, uint64_t flags, cred_t *cr,
    dsl_crypto_params_t *dcp, dmu_tx_t *tx)
{
        dsl_pool_t *dp = pdd->dd_pool;
        uint64_t dsobj, ddobj;
        dsl_dir_t *dd;

        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(lastname[0] != '@');
        /*
         * Filesystems will eventually have their origin set to dp_origin_snap,
         * but that's taken care of in dsl_dataset_create_sync_dd. When
         * creating a filesystem, this function is called with origin equal to
         * NULL.
         */
        if (origin != NULL)
                ASSERT3P(origin, !=, dp->dp_origin_snap);

        ddobj = dsl_dir_create_sync(dp, pdd, lastname, tx);
        VERIFY0(dsl_dir_hold_obj(dp, ddobj, lastname, FTAG, &dd));

        dsobj = dsl_dataset_create_sync_dd(dd, origin, dcp,
            flags & ~DS_CREATE_FLAG_NODIRTY, tx);

        dsl_deleg_set_create_perms(dd, tx, cr);

        /*
         * If we are creating a clone and the livelist feature is enabled,
         * add the entry DD_FIELD_LIVELIST to ZAP.
         */
        if (origin != NULL &&
            spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_LIVELIST)) {
                objset_t *mos = dd->dd_pool->dp_meta_objset;
                dsl_dir_zapify(dd, tx);
                uint64_t obj = dsl_deadlist_alloc(mos, tx);
                VERIFY0(zap_add(mos, dd->dd_object, DD_FIELD_LIVELIST,
                    sizeof (uint64_t), 1, &obj, tx));
                spa_feature_incr(dp->dp_spa, SPA_FEATURE_LIVELIST, tx);
        }

        /*
         * Since we're creating a new node we know it's a leaf, so we can
         * initialize the counts if the limit feature is active.
         */
        if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_FS_SS_LIMIT)) {
                uint64_t cnt = 0;
                objset_t *os = dd->dd_pool->dp_meta_objset;

                dsl_dir_zapify(dd, tx);
                VERIFY0(zap_add(os, dd->dd_object, DD_FIELD_FILESYSTEM_COUNT,
                    sizeof (cnt), 1, &cnt, tx));
                VERIFY0(zap_add(os, dd->dd_object, DD_FIELD_SNAPSHOT_COUNT,
                    sizeof (cnt), 1, &cnt, tx));
        }

        dsl_dir_rele(dd, FTAG);

        /*
         * If we are creating a clone, make sure we zero out any stale
         * data from the origin snapshots zil header.
         */
        if (origin != NULL && !(flags & DS_CREATE_FLAG_NODIRTY)) {
                dsl_dataset_t *ds;

                VERIFY0(dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
                dsl_dataset_zero_zil(ds, tx);
                dsl_dataset_rele(ds, FTAG);
        }

        return (dsobj);
}

/*
 * The unique space in the head dataset can be calculated by subtracting
 * the space used in the most recent snapshot, that is still being used
 * in this file system, from the space currently in use.  To figure out
 * the space in the most recent snapshot still in use, we need to take
 * the total space used in the snapshot and subtract out the space that
 * has been freed up since the snapshot was taken.
 */
void
dsl_dataset_recalc_head_uniq(dsl_dataset_t *ds)
{
        uint64_t mrs_used;
        uint64_t dlused, dlcomp, dluncomp;

        ASSERT(!ds->ds_is_snapshot);

        if (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0)
                mrs_used = dsl_dataset_phys(ds->ds_prev)->ds_referenced_bytes;
        else
                mrs_used = 0;

        dsl_deadlist_space(&ds->ds_deadlist, &dlused, &dlcomp, &dluncomp);

        ASSERT3U(dlused, <=, mrs_used);
        dsl_dataset_phys(ds)->ds_unique_bytes =
            dsl_dataset_phys(ds)->ds_referenced_bytes - (mrs_used - dlused);

        if (spa_version(ds->ds_dir->dd_pool->dp_spa) >=
            SPA_VERSION_UNIQUE_ACCURATE)
                dsl_dataset_phys(ds)->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;
}

void
dsl_dataset_remove_from_next_clones(dsl_dataset_t *ds, uint64_t obj,
    dmu_tx_t *tx)
{
        objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
        uint64_t count __maybe_unused;
        int err;

        ASSERT(dsl_dataset_phys(ds)->ds_num_children >= 2);
        err = zap_remove_int(mos, dsl_dataset_phys(ds)->ds_next_clones_obj,
            obj, tx);
        /*
         * The err should not be ENOENT, but a bug in a previous version
         * of the code could cause upgrade_clones_cb() to not set
         * ds_next_snap_obj when it should, leading to a missing entry.
         * If we knew that the pool was created after
         * SPA_VERSION_NEXT_CLONES, we could assert that it isn't
         * ENOENT.  However, at least we can check that we don't have
         * too many entries in the next_clones_obj even after failing to
         * remove this one.
         */
        if (err != ENOENT)
                VERIFY0(err);
        ASSERT0(zap_count(mos, dsl_dataset_phys(ds)->ds_next_clones_obj,
            &count));
        ASSERT3U(count, <=, dsl_dataset_phys(ds)->ds_num_children - 2);
}


blkptr_t *
dsl_dataset_get_blkptr(dsl_dataset_t *ds)
{
        return (&dsl_dataset_phys(ds)->ds_bp);
}

spa_t *
dsl_dataset_get_spa(dsl_dataset_t *ds)
{
        return (ds->ds_dir->dd_pool->dp_spa);
}

void
dsl_dataset_dirty(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        dsl_pool_t *dp;

        if (ds == NULL) /* this is the meta-objset */
                return;

        ASSERT(ds->ds_objset != NULL);

        if (dsl_dataset_phys(ds)->ds_next_snap_obj != 0)
                panic("dirtying snapshot!");

        /* Must not dirty a dataset in the same txg where it got snapshotted. */
        ASSERT3U(tx->tx_txg, >, dsl_dataset_phys(ds)->ds_prev_snap_txg);

        dp = ds->ds_dir->dd_pool;
        if (txg_list_add(&dp->dp_dirty_datasets, ds, tx->tx_txg)) {
                objset_t *os = ds->ds_objset;

                /* up the hold count until we can be written out */
                dmu_buf_add_ref(ds->ds_dbuf, ds);

                /* if this dataset is encrypted, grab a reference to the DCK */
                if (ds->ds_dir->dd_crypto_obj != 0 &&
                    !os->os_raw_receive &&
                    !os->os_next_write_raw[tx->tx_txg & TXG_MASK]) {
                        ASSERT3P(ds->ds_key_mapping, !=, NULL);
                        key_mapping_add_ref(ds->ds_key_mapping, ds);
                }
        }
}

static int
dsl_dataset_snapshot_reserve_space(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        uint64_t asize;

        if (!dmu_tx_is_syncing(tx))
                return (0);

        /*
         * If there's an fs-only reservation, any blocks that might become
         * owned by the snapshot dataset must be accommodated by space
         * outside of the reservation.
         */
        ASSERT(ds->ds_reserved == 0 || DS_UNIQUE_IS_ACCURATE(ds));
        asize = MIN(dsl_dataset_phys(ds)->ds_unique_bytes, ds->ds_reserved);
        if (asize > dsl_dir_space_available(ds->ds_dir, NULL, 0, TRUE))
                return (SET_ERROR(ENOSPC));

        /*
         * Propagate any reserved space for this snapshot to other
         * snapshot checks in this sync group.
         */
        if (asize > 0)
                dsl_dir_willuse_space(ds->ds_dir, asize, tx);

        return (0);
}

int
dsl_dataset_snapshot_check_impl(dsl_dataset_t *ds, const char *snapname,
    dmu_tx_t *tx, boolean_t recv, uint64_t cnt, cred_t *cr, proc_t *proc)
{
        int error;
        uint64_t value;

        ds->ds_trysnap_txg = tx->tx_txg;

        if (!dmu_tx_is_syncing(tx))
                return (0);

        /*
         * We don't allow multiple snapshots of the same txg.  If there
         * is already one, try again.
         */
        if (dsl_dataset_phys(ds)->ds_prev_snap_txg >= tx->tx_txg)
                return (SET_ERROR(EAGAIN));

        /*
         * Check for conflicting snapshot name.
         */
        error = dsl_dataset_snap_lookup(ds, snapname, &value);
        if (error == 0)
                return (SET_ERROR(EEXIST));
        if (error != ENOENT)
                return (error);

        /*
         * We don't allow taking snapshots of inconsistent datasets, such as
         * those into which we are currently receiving.  However, if we are
         * creating this snapshot as part of a receive, this check will be
         * executed atomically with respect to the completion of the receive
         * itself but prior to the clearing of DS_FLAG_INCONSISTENT; in this
         * case we ignore this, knowing it will be fixed up for us shortly in
         * dmu_recv_end_sync().
         */
        if (!recv && DS_IS_INCONSISTENT(ds))
                return (SET_ERROR(EBUSY));

        /*
         * Skip the check for temporary snapshots or if we have already checked
         * the counts in dsl_dataset_snapshot_check. This means we really only
         * check the count here when we're receiving a stream.
         */
        if (cnt != 0 && cr != NULL) {
                error = dsl_fs_ss_limit_check(ds->ds_dir, cnt,
                    ZFS_PROP_SNAPSHOT_LIMIT, NULL, cr, proc);
                if (error != 0)
                        return (error);
        }

        error = dsl_dataset_snapshot_reserve_space(ds, tx);
        if (error != 0)
                return (error);

        return (0);
}

int
dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_snapshot_arg_t *ddsa = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        nvpair_t *pair;
        int rv = 0;

        /*
         * Pre-compute how many total new snapshots will be created for each
         * level in the tree and below. This is needed for validating the
         * snapshot limit when either taking a recursive snapshot or when
         * taking multiple snapshots.
         *
         * The problem is that the counts are not actually adjusted when
         * we are checking, only when we finally sync. For a single snapshot,
         * this is easy, the count will increase by 1 at each node up the tree,
         * but its more complicated for the recursive/multiple snapshot case.
         *
         * The dsl_fs_ss_limit_check function does recursively check the count
         * at each level up the tree but since it is validating each snapshot
         * independently we need to be sure that we are validating the complete
         * count for the entire set of snapshots. We do this by rolling up the
         * counts for each component of the name into an nvlist and then
         * checking each of those cases with the aggregated count.
         *
         * This approach properly handles not only the recursive snapshot
         * case (where we get all of those on the ddsa_snaps list) but also
         * the sibling case (e.g. snapshot a/b and a/c so that we will also
         * validate the limit on 'a' using a count of 2).
         *
         * We validate the snapshot names in the third loop and only report
         * name errors once.
         */
        if (dmu_tx_is_syncing(tx)) {
                char *nm;
                nvlist_t *cnt_track = NULL;
                cnt_track = fnvlist_alloc();

                nm = kmem_alloc(MAXPATHLEN, KM_SLEEP);

                /* Rollup aggregated counts into the cnt_track list */
                for (pair = nvlist_next_nvpair(ddsa->ddsa_snaps, NULL);
                    pair != NULL;
                    pair = nvlist_next_nvpair(ddsa->ddsa_snaps, pair)) {
                        char *pdelim;
                        uint64_t val;

                        (void) strlcpy(nm, nvpair_name(pair), MAXPATHLEN);
                        pdelim = strchr(nm, '@');
                        if (pdelim == NULL)
                                continue;
                        *pdelim = '\0';

                        do {
                                if (nvlist_lookup_uint64(cnt_track, nm,
                                    &val) == 0) {
                                        /* update existing entry */
                                        fnvlist_add_uint64(cnt_track, nm,
                                            val + 1);
                                } else {
                                        /* add to list */
                                        fnvlist_add_uint64(cnt_track, nm, 1);
                                }

                                pdelim = strrchr(nm, '/');
                                if (pdelim != NULL)
                                        *pdelim = '\0';
                        } while (pdelim != NULL);
                }

                kmem_free(nm, MAXPATHLEN);

                /* Check aggregated counts at each level */
                for (pair = nvlist_next_nvpair(cnt_track, NULL);
                    pair != NULL; pair = nvlist_next_nvpair(cnt_track, pair)) {
                        int error = 0;
                        const char *name;
                        uint64_t cnt = 0;
                        dsl_dataset_t *ds;

                        name = nvpair_name(pair);
                        cnt = fnvpair_value_uint64(pair);
                        ASSERT(cnt > 0);

                        error = dsl_dataset_hold(dp, name, FTAG, &ds);
                        if (error == 0) {
                                error = dsl_fs_ss_limit_check(ds->ds_dir, cnt,
                                    ZFS_PROP_SNAPSHOT_LIMIT, NULL,
                                    ddsa->ddsa_cr, ddsa->ddsa_proc);
                                dsl_dataset_rele(ds, FTAG);
                        }

                        if (error != 0) {
                                if (ddsa->ddsa_errors != NULL)
                                        fnvlist_add_int32(ddsa->ddsa_errors,
                                            name, error);
                                rv = error;
                                /* only report one error for this check */
                                break;
                        }
                }
                nvlist_free(cnt_track);
        }

        for (pair = nvlist_next_nvpair(ddsa->ddsa_snaps, NULL);
            pair != NULL; pair = nvlist_next_nvpair(ddsa->ddsa_snaps, pair)) {
                int error = 0;
                dsl_dataset_t *ds;
                const char *name, *atp = NULL;
                char dsname[ZFS_MAX_DATASET_NAME_LEN];

                name = nvpair_name(pair);
                if (strlen(name) >= ZFS_MAX_DATASET_NAME_LEN)
                        error = SET_ERROR(ENAMETOOLONG);
                if (error == 0) {
                        atp = strchr(name, '@');
                        if (atp == NULL)
                                error = SET_ERROR(EINVAL);
                        if (error == 0)
                                (void) strlcpy(dsname, name, atp - name + 1);
                }
                if (error == 0)
                        error = dsl_dataset_hold(dp, dsname, FTAG, &ds);
                if (error == 0) {
                        /* passing 0/NULL skips dsl_fs_ss_limit_check */
                        error = dsl_dataset_snapshot_check_impl(ds,
                            atp + 1, tx, B_FALSE, 0, NULL, NULL);
                        dsl_dataset_rele(ds, FTAG);
                }

                if (error != 0) {
                        if (ddsa->ddsa_errors != NULL) {
                                fnvlist_add_int32(ddsa->ddsa_errors,
                                    name, error);
                        }
                        rv = error;
                }
        }

        return (rv);
}

void
dsl_dataset_snapshot_sync_impl(dsl_dataset_t *ds, const char *snapname,
    dmu_tx_t *tx)
{
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        dmu_buf_t *dbuf;
        dsl_dataset_phys_t *dsphys;
        uint64_t dsobj, crtxg;
        objset_t *mos = dp->dp_meta_objset;
        objset_t *os __maybe_unused;

        ASSERT(RRW_WRITE_HELD(&dp->dp_config_rwlock));

        /*
         * If we are on an old pool, the zil must not be active, in which
         * case it will be zeroed.  Usually zil_suspend() accomplishes this.
         */
        ASSERT(spa_version(dmu_tx_pool(tx)->dp_spa) >= SPA_VERSION_FAST_SNAP ||
            dmu_objset_from_ds(ds, &os) != 0 ||
            memcmp(&os->os_phys->os_zil_header, &zero_zil,
            sizeof (zero_zil)) == 0);

        /* Should not snapshot a dirty dataset. */
        ASSERT(!txg_list_member(&ds->ds_dir->dd_pool->dp_dirty_datasets,
            ds, tx->tx_txg));

        dsl_fs_ss_count_adjust(ds->ds_dir, 1, DD_FIELD_SNAPSHOT_COUNT, tx);

        /*
         * The origin's ds_creation_txg has to be < TXG_INITIAL
         */
        if (strcmp(snapname, ORIGIN_DIR_NAME) == 0)
                crtxg = 1;
        else
                crtxg = tx->tx_txg;

        dsobj = dmu_object_alloc(mos, DMU_OT_DSL_DATASET, 0,
            DMU_OT_DSL_DATASET, sizeof (dsl_dataset_phys_t), tx);
        VERIFY0(dmu_bonus_hold(mos, dsobj, FTAG, &dbuf));
        dmu_buf_will_dirty(dbuf, tx);
        dsphys = dbuf->db_data;
        memset(dsphys, 0, sizeof (dsl_dataset_phys_t));
        dsphys->ds_dir_obj = ds->ds_dir->dd_object;
        dsphys->ds_fsid_guid = unique_create();
        (void) random_get_pseudo_bytes((void*)&dsphys->ds_guid,
            sizeof (dsphys->ds_guid));
        dsphys->ds_prev_snap_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
        dsphys->ds_prev_snap_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
        dsphys->ds_next_snap_obj = ds->ds_object;
        dsphys->ds_num_children = 1;
        dsphys->ds_creation_time = gethrestime_sec();
        dsphys->ds_creation_txg = crtxg;
        dsphys->ds_deadlist_obj = dsl_dataset_phys(ds)->ds_deadlist_obj;
        dsphys->ds_referenced_bytes = dsl_dataset_phys(ds)->ds_referenced_bytes;
        dsphys->ds_compressed_bytes = dsl_dataset_phys(ds)->ds_compressed_bytes;
        dsphys->ds_uncompressed_bytes =
            dsl_dataset_phys(ds)->ds_uncompressed_bytes;
        dsphys->ds_flags = dsl_dataset_phys(ds)->ds_flags;
        rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
        dsphys->ds_bp = dsl_dataset_phys(ds)->ds_bp;
        rrw_exit(&ds->ds_bp_rwlock, FTAG);
        dmu_buf_rele(dbuf, FTAG);

        for (spa_feature_t f = 0; f < SPA_FEATURES; f++) {
                if (zfeature_active(f, ds->ds_feature[f])) {
                        dsl_dataset_activate_feature(dsobj, f,
                            ds->ds_feature[f], tx);
                }
        }

        ASSERT3U(ds->ds_prev != 0, ==,
            dsl_dataset_phys(ds)->ds_prev_snap_obj != 0);
        if (ds->ds_prev) {
                uint64_t next_clones_obj =
                    dsl_dataset_phys(ds->ds_prev)->ds_next_clones_obj;
                ASSERT(dsl_dataset_phys(ds->ds_prev)->ds_next_snap_obj ==
                    ds->ds_object ||
                    dsl_dataset_phys(ds->ds_prev)->ds_num_children > 1);
                if (dsl_dataset_phys(ds->ds_prev)->ds_next_snap_obj ==
                    ds->ds_object) {
                        dmu_buf_will_dirty(ds->ds_prev->ds_dbuf, tx);
                        ASSERT3U(dsl_dataset_phys(ds)->ds_prev_snap_txg, ==,
                            dsl_dataset_phys(ds->ds_prev)->ds_creation_txg);
                        dsl_dataset_phys(ds->ds_prev)->ds_next_snap_obj = dsobj;
                } else if (next_clones_obj != 0) {
                        dsl_dataset_remove_from_next_clones(ds->ds_prev,
                            dsphys->ds_next_snap_obj, tx);
                        VERIFY0(zap_add_int(mos,
                            next_clones_obj, dsobj, tx));
                }
        }

        /*
         * If we have a reference-reservation on this dataset, we will
         * need to increase the amount of refreservation being charged
         * since our unique space is going to zero.
         */
        if (ds->ds_reserved) {
                int64_t delta;
                ASSERT(DS_UNIQUE_IS_ACCURATE(ds));
                delta = MIN(dsl_dataset_phys(ds)->ds_unique_bytes,
                    ds->ds_reserved);
                dsl_dir_diduse_space(ds->ds_dir, DD_USED_REFRSRV,
                    delta, 0, 0, tx);
        }

        dmu_buf_will_dirty(ds->ds_dbuf, tx);
        dsl_dataset_phys(ds)->ds_deadlist_obj =
            dsl_deadlist_clone(&ds->ds_deadlist, UINT64_MAX,
            dsl_dataset_phys(ds)->ds_prev_snap_obj, tx);
        dsl_deadlist_close(&ds->ds_deadlist);
        VERIFY0(dsl_deadlist_open(&ds->ds_deadlist, mos,
            dsl_dataset_phys(ds)->ds_deadlist_obj));
        dsl_deadlist_add_key(&ds->ds_deadlist,
            dsl_dataset_phys(ds)->ds_prev_snap_txg, tx);
        dsl_bookmark_snapshotted(ds, tx);

        if (dsl_dataset_remap_deadlist_exists(ds)) {
                uint64_t remap_deadlist_obj =
                    dsl_dataset_get_remap_deadlist_object(ds);
                /*
                 * Move the remap_deadlist to the snapshot.  The head
                 * will create a new remap deadlist on demand, from
                 * dsl_dataset_block_remapped().
                 */
                dsl_dataset_unset_remap_deadlist_object(ds, tx);
                dsl_deadlist_close(&ds->ds_remap_deadlist);

                dmu_object_zapify(mos, dsobj, DMU_OT_DSL_DATASET, tx);
                VERIFY0(zap_add(mos, dsobj, DS_FIELD_REMAP_DEADLIST,
                    sizeof (remap_deadlist_obj), 1, &remap_deadlist_obj, tx));
        }

        /*
         * Create a ivset guid for this snapshot if the dataset is
         * encrypted. This may be overridden by a raw receive. A
         * previous implementation of this code did not have this
         * field as part of the on-disk format for ZFS encryption
         * (see errata #4). As part of the remediation for this
         * issue, we ask the user to enable the bookmark_v2 feature
         * which is now a dependency of the encryption feature. We
         * use this as a heuristic to determine when the user has
         * elected to correct any datasets created with the old code.
         * As a result, we only do this step if the bookmark_v2
         * feature is enabled, which limits the number of states a
         * given pool / dataset can be in with regards to terms of
         * correcting the issue.
         */
        if (ds->ds_dir->dd_crypto_obj != 0 &&
            spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_BOOKMARK_V2)) {
                uint64_t ivset_guid = unique_create();

                dmu_object_zapify(mos, dsobj, DMU_OT_DSL_DATASET, tx);
                VERIFY0(zap_add(mos, dsobj, DS_FIELD_IVSET_GUID,
                    sizeof (ivset_guid), 1, &ivset_guid, tx));
        }

        ASSERT3U(dsl_dataset_phys(ds)->ds_prev_snap_txg, <, tx->tx_txg);
        dsl_dataset_phys(ds)->ds_prev_snap_obj = dsobj;
        dsl_dataset_phys(ds)->ds_prev_snap_txg = crtxg;
        dsl_dataset_phys(ds)->ds_unique_bytes = 0;

        if (spa_version(dp->dp_spa) >= SPA_VERSION_UNIQUE_ACCURATE)
                dsl_dataset_phys(ds)->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;

        VERIFY0(zap_add(mos, dsl_dataset_phys(ds)->ds_snapnames_zapobj,
            snapname, 8, 1, &dsobj, tx));

        if (ds->ds_prev)
                dsl_dataset_rele(ds->ds_prev, ds);
        VERIFY0(dsl_dataset_hold_obj(dp,
            dsl_dataset_phys(ds)->ds_prev_snap_obj, ds, &ds->ds_prev));

        dsl_scan_ds_snapshotted(ds, tx);

        dsl_dir_snap_cmtime_update(ds->ds_dir, tx);

        if (zfs_snapshot_history_enabled)
                spa_history_log_internal_ds(ds->ds_prev, "snapshot", tx, " ");
}

void
dsl_dataset_snapshot_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_snapshot_arg_t *ddsa = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        nvpair_t *pair;

        for (pair = nvlist_next_nvpair(ddsa->ddsa_snaps, NULL);
            pair != NULL; pair = nvlist_next_nvpair(ddsa->ddsa_snaps, pair)) {
                dsl_dataset_t *ds;
                const char *name, *atp;
                char dsname[ZFS_MAX_DATASET_NAME_LEN];

                name = nvpair_name(pair);
                atp = strchr(name, '@');
                (void) strlcpy(dsname, name, atp - name + 1);
                VERIFY0(dsl_dataset_hold(dp, dsname, FTAG, &ds));

                dsl_dataset_snapshot_sync_impl(ds, atp + 1, tx);
                if (ddsa->ddsa_props != NULL) {
                        dsl_props_set_sync_impl(ds->ds_prev,
                            ZPROP_SRC_LOCAL, ddsa->ddsa_props, tx);
                }
                dsl_dataset_rele(ds, FTAG);
        }
}

/*
 * The snapshots must all be in the same pool.
 * All-or-nothing: if there are any failures, nothing will be modified.
 */
int
dsl_dataset_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t *errors)
{
        dsl_dataset_snapshot_arg_t ddsa;
        nvpair_t *pair;
        boolean_t needsuspend;
        int error;
        spa_t *spa;
        const char *firstname;
        nvlist_t *suspended = NULL;

        pair = nvlist_next_nvpair(snaps, NULL);
        if (pair == NULL)
                return (0);
        firstname = nvpair_name(pair);

        error = spa_open(firstname, &spa, FTAG);
        if (error != 0)
                return (error);
        needsuspend = (spa_version(spa) < SPA_VERSION_FAST_SNAP);
        spa_close(spa, FTAG);

        if (needsuspend) {
                suspended = fnvlist_alloc();
                for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
                    pair = nvlist_next_nvpair(snaps, pair)) {
                        char fsname[ZFS_MAX_DATASET_NAME_LEN];
                        const char *snapname = nvpair_name(pair);
                        const char *atp;
                        void *cookie;

                        atp = strchr(snapname, '@');
                        if (atp == NULL) {
                                error = SET_ERROR(EINVAL);
                                break;
                        }
                        (void) strlcpy(fsname, snapname, atp - snapname + 1);

                        error = zil_suspend(fsname, &cookie);
                        if (error != 0)
                                break;
                        fnvlist_add_uint64(suspended, fsname,
                            (uintptr_t)cookie);
                }
        }

        ddsa.ddsa_snaps = snaps;
        ddsa.ddsa_props = props;
        ddsa.ddsa_errors = errors;
        ddsa.ddsa_cr = CRED();
        ddsa.ddsa_proc = curproc;

        if (error == 0) {
                error = dsl_sync_task(firstname, dsl_dataset_snapshot_check,
                    dsl_dataset_snapshot_sync, &ddsa,
                    fnvlist_num_pairs(snaps) * 3, ZFS_SPACE_CHECK_NORMAL);
        }

        if (suspended != NULL) {
                for (pair = nvlist_next_nvpair(suspended, NULL); pair != NULL;
                    pair = nvlist_next_nvpair(suspended, pair)) {
                        zil_resume((void *)(uintptr_t)
                            fnvpair_value_uint64(pair));
                }
                fnvlist_free(suspended);
        }

        if (error == 0) {
                for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
                    pair = nvlist_next_nvpair(snaps, pair)) {
                        zvol_create_minor(nvpair_name(pair));
                }
        }

        return (error);
}

typedef struct dsl_dataset_snapshot_tmp_arg {
        const char *ddsta_fsname;
        const char *ddsta_snapname;
        minor_t ddsta_cleanup_minor;
        const char *ddsta_htag;
} dsl_dataset_snapshot_tmp_arg_t;

static int
dsl_dataset_snapshot_tmp_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_snapshot_tmp_arg_t *ddsta = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds;
        int error;

        error = dsl_dataset_hold(dp, ddsta->ddsta_fsname, FTAG, &ds);
        if (error != 0)
                return (error);

        /* NULL cred means no limit check for tmp snapshot */
        error = dsl_dataset_snapshot_check_impl(ds, ddsta->ddsta_snapname,
            tx, B_FALSE, 0, NULL, NULL);
        if (error != 0) {
                dsl_dataset_rele(ds, FTAG);
                return (error);
        }

        if (spa_version(dp->dp_spa) < SPA_VERSION_USERREFS) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(ENOTSUP));
        }
        error = dsl_dataset_user_hold_check_one(NULL, ddsta->ddsta_htag,
            B_TRUE, tx);
        if (error != 0) {
                dsl_dataset_rele(ds, FTAG);
                return (error);
        }

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

static void
dsl_dataset_snapshot_tmp_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_snapshot_tmp_arg_t *ddsta = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds = NULL;

        VERIFY0(dsl_dataset_hold(dp, ddsta->ddsta_fsname, FTAG, &ds));

        dsl_dataset_snapshot_sync_impl(ds, ddsta->ddsta_snapname, tx);
        dsl_dataset_user_hold_sync_one(ds->ds_prev, ddsta->ddsta_htag,
            ddsta->ddsta_cleanup_minor, gethrestime_sec(), tx);
        dsl_destroy_snapshot_sync_impl(ds->ds_prev, B_TRUE, tx);

        dsl_dataset_rele(ds, FTAG);
}

int
dsl_dataset_snapshot_tmp(const char *fsname, const char *snapname,
    minor_t cleanup_minor, const char *htag)
{
        dsl_dataset_snapshot_tmp_arg_t ddsta;
        int error;
        spa_t *spa;
        boolean_t needsuspend;
        void *cookie;

        ddsta.ddsta_fsname = fsname;
        ddsta.ddsta_snapname = snapname;
        ddsta.ddsta_cleanup_minor = cleanup_minor;
        ddsta.ddsta_htag = htag;

        error = spa_open(fsname, &spa, FTAG);
        if (error != 0)
                return (error);
        needsuspend = (spa_version(spa) < SPA_VERSION_FAST_SNAP);
        spa_close(spa, FTAG);

        if (needsuspend) {
                error = zil_suspend(fsname, &cookie);
                if (error != 0)
                        return (error);
        }

        error = dsl_sync_task(fsname, dsl_dataset_snapshot_tmp_check,
            dsl_dataset_snapshot_tmp_sync, &ddsta, 3, ZFS_SPACE_CHECK_RESERVED);

        if (needsuspend)
                zil_resume(cookie);
        return (error);
}

/* Nonblocking dataset sync. Assumes dataset:objset is always 1:1 */
void
dsl_dataset_sync(dsl_dataset_t *ds, zio_t *rio, dmu_tx_t *tx)
{
        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(ds->ds_objset != NULL);
        ASSERT(dsl_dataset_phys(ds)->ds_next_snap_obj == 0);

        /*
         * in case we had to change ds_fsid_guid when we opened it,
         * sync it out now.
         */
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
        dsl_dataset_phys(ds)->ds_fsid_guid = ds->ds_fsid_guid;

        if (ds->ds_resume_bytes[tx->tx_txg & TXG_MASK] != 0) {
                VERIFY0(zap_update(tx->tx_pool->dp_meta_objset,
                    ds->ds_object, DS_FIELD_RESUME_OBJECT, 8, 1,
                    &ds->ds_resume_object[tx->tx_txg & TXG_MASK], tx));
                VERIFY0(zap_update(tx->tx_pool->dp_meta_objset,
                    ds->ds_object, DS_FIELD_RESUME_OFFSET, 8, 1,
                    &ds->ds_resume_offset[tx->tx_txg & TXG_MASK], tx));
                VERIFY0(zap_update(tx->tx_pool->dp_meta_objset,
                    ds->ds_object, DS_FIELD_RESUME_BYTES, 8, 1,
                    &ds->ds_resume_bytes[tx->tx_txg & TXG_MASK], tx));
                ds->ds_resume_object[tx->tx_txg & TXG_MASK] = 0;
                ds->ds_resume_offset[tx->tx_txg & TXG_MASK] = 0;
                ds->ds_resume_bytes[tx->tx_txg & TXG_MASK] = 0;
        }

        dmu_objset_sync(ds->ds_objset, rio, tx);
}

/*
 * Check if the percentage of blocks shared between the clone and the
 * snapshot (as opposed to those that are clone only) is below a certain
 * threshold
 */
static boolean_t
dsl_livelist_should_disable(dsl_dataset_t *ds)
{
        uint64_t used, referenced;
        int percent_shared;

        used = dsl_dir_get_usedds(ds->ds_dir);
        referenced = dsl_get_referenced(ds);
        if (referenced == 0)
                return (B_FALSE);
        percent_shared = (100 * (referenced - used)) / referenced;
        if (percent_shared <= zfs_livelist_min_percent_shared)
                return (B_TRUE);
        return (B_FALSE);
}

/*
 *  Check if it is possible to combine two livelist entries into one.
 *  This is the case if the combined number of 'live' blkptrs (ALLOCs that
 *  don't have a matching FREE) is under the maximum sublist size.
 *  We check this by subtracting twice the total number of frees from the total
 *  number of blkptrs. FREEs are counted twice because each FREE blkptr
 *  will cancel out an ALLOC blkptr when the livelist is processed.
 */
static boolean_t
dsl_livelist_should_condense(dsl_deadlist_entry_t *first,
    dsl_deadlist_entry_t *next)
{
        uint64_t total_free = first->dle_bpobj.bpo_phys->bpo_num_freed +
            next->dle_bpobj.bpo_phys->bpo_num_freed;
        uint64_t total_entries = first->dle_bpobj.bpo_phys->bpo_num_blkptrs +
            next->dle_bpobj.bpo_phys->bpo_num_blkptrs;
        if ((total_entries - (2 * total_free)) < zfs_livelist_max_entries)
                return (B_TRUE);
        return (B_FALSE);
}

typedef struct try_condense_arg {
        spa_t *spa;
        dsl_dataset_t *ds;
} try_condense_arg_t;

/*
 * Iterate over the livelist entries, searching for a pair to condense.
 * A nonzero return value means stop, 0 means keep looking.
 */
static int
dsl_livelist_try_condense(void *arg, dsl_deadlist_entry_t *first)
{
        try_condense_arg_t *tca = arg;
        spa_t *spa = tca->spa;
        dsl_dataset_t *ds = tca->ds;
        dsl_deadlist_t *ll = &ds->ds_dir->dd_livelist;
        dsl_deadlist_entry_t *next;

        /* The condense thread has not yet been created at import */
        if (spa->spa_livelist_condense_zthr == NULL)
                return (1);

        /* A condense is already in progress */
        if (spa->spa_to_condense.ds != NULL)
                return (1);

        next = AVL_NEXT(&ll->dl_tree, &first->dle_node);
        /* The livelist has only one entry - don't condense it */
        if (next == NULL)
                return (1);

        /* Next is the newest entry - don't condense it */
        if (AVL_NEXT(&ll->dl_tree, &next->dle_node) == NULL)
                return (1);

        /* This pair is not ready to condense but keep looking */
        if (!dsl_livelist_should_condense(first, next))
                return (0);

        /*
         * Add a ref to prevent the dataset from being evicted while
         * the condense zthr or synctask are running. Ref will be
         * released at the end of the condense synctask
         */
        dmu_buf_add_ref(ds->ds_dbuf, spa);

        spa->spa_to_condense.ds = ds;
        spa->spa_to_condense.first = first;
        spa->spa_to_condense.next = next;
        spa->spa_to_condense.syncing = B_FALSE;
        spa->spa_to_condense.cancelled = B_FALSE;

        zthr_wakeup(spa->spa_livelist_condense_zthr);
        return (1);
}

static void
dsl_flush_pending_livelist(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        dsl_dir_t *dd = ds->ds_dir;
        spa_t *spa = ds->ds_dir->dd_pool->dp_spa;
        dsl_deadlist_entry_t *last = dsl_deadlist_last(&dd->dd_livelist);

        /* Check if we need to add a new sub-livelist */
        if (last == NULL) {
                /* The livelist is empty */
                dsl_deadlist_add_key(&dd->dd_livelist,
                    tx->tx_txg - 1, tx);
        } else if (spa_sync_pass(spa) == 1) {
                /*
                 * Check if the newest entry is full. If it is, make a new one.
                 * We only do this once per sync because we could overfill a
                 * sublist in one sync pass and don't want to add another entry
                 * for a txg that is already represented. This ensures that
                 * blkptrs born in the same txg are stored in the same sublist.
                 */
                bpobj_t bpobj = last->dle_bpobj;
                uint64_t all = bpobj.bpo_phys->bpo_num_blkptrs;
                uint64_t free = bpobj.bpo_phys->bpo_num_freed;
                uint64_t alloc = all - free;
                if (alloc > zfs_livelist_max_entries) {
                        dsl_deadlist_add_key(&dd->dd_livelist,
                            tx->tx_txg - 1, tx);
                }
        }

        /* Insert each entry into the on-disk livelist */
        bplist_iterate(&dd->dd_pending_allocs,
            dsl_deadlist_insert_alloc_cb, &dd->dd_livelist, tx);
        bplist_iterate(&dd->dd_pending_frees,
            dsl_deadlist_insert_free_cb, &dd->dd_livelist, tx);

        /* Attempt to condense every pair of adjacent entries */
        try_condense_arg_t arg = {
            .spa = spa,
            .ds = ds
        };
        dsl_deadlist_iterate(&dd->dd_livelist, dsl_livelist_try_condense,
            &arg);
}

void
dsl_dataset_sync_done(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        objset_t *os = ds->ds_objset;

        bplist_iterate(&ds->ds_pending_deadlist,
            dsl_deadlist_insert_alloc_cb, &ds->ds_deadlist, tx);

        if (dsl_deadlist_is_open(&ds->ds_dir->dd_livelist)) {
                dsl_flush_pending_livelist(ds, tx);
                if (dsl_livelist_should_disable(ds)) {
                        dsl_dir_remove_livelist(ds->ds_dir, tx, B_TRUE);
                }
        }

        dsl_bookmark_sync_done(ds, tx);

        multilist_destroy(&os->os_synced_dnodes);

        if (os->os_encrypted)
                os->os_next_write_raw[tx->tx_txg & TXG_MASK] = B_FALSE;
        else
                ASSERT0(os->os_next_write_raw[tx->tx_txg & TXG_MASK]);

        for (spa_feature_t f = 0; f < SPA_FEATURES; f++) {
                if (zfeature_active(f,
                    ds->ds_feature_activation[f])) {
                        if (zfeature_active(f, ds->ds_feature[f]))
                                continue;
                        dsl_dataset_activate_feature(ds->ds_object, f,
                            ds->ds_feature_activation[f], tx);
                        ds->ds_feature[f] = ds->ds_feature_activation[f];
                }
        }

        ASSERT(!dmu_objset_is_dirty(os, dmu_tx_get_txg(tx)));
}

int
get_clones_stat_impl(dsl_dataset_t *ds, nvlist_t *val)
{
        uint64_t count = 0;
        objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
        zap_cursor_t zc;
        zap_attribute_t *za;

        ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));

        /*
         * There may be missing entries in ds_next_clones_obj
         * due to a bug in a previous version of the code.
         * Only trust it if it has the right number of entries.
         */
        if (dsl_dataset_phys(ds)->ds_next_clones_obj != 0) {
                VERIFY0(zap_count(mos, dsl_dataset_phys(ds)->ds_next_clones_obj,
                    &count));
        }
        if (count != dsl_dataset_phys(ds)->ds_num_children - 1) {
                return (SET_ERROR(ENOENT));
        }

        za = zap_attribute_alloc();
        for (zap_cursor_init(&zc, mos,
            dsl_dataset_phys(ds)->ds_next_clones_obj);
            zap_cursor_retrieve(&zc, za) == 0;
            zap_cursor_advance(&zc)) {
                dsl_dataset_t *clone;
                char buf[ZFS_MAX_DATASET_NAME_LEN];
                VERIFY0(dsl_dataset_hold_obj(ds->ds_dir->dd_pool,
                    za->za_first_integer, FTAG, &clone));
                dsl_dir_name(clone->ds_dir, buf);
                fnvlist_add_boolean(val, buf);
                dsl_dataset_rele(clone, FTAG);
        }
        zap_cursor_fini(&zc);
        zap_attribute_free(za);
        return (0);
}

void
get_clones_stat(dsl_dataset_t *ds, nvlist_t *nv)
{
        nvlist_t *propval = fnvlist_alloc();
        nvlist_t *val = fnvlist_alloc();

        if (get_clones_stat_impl(ds, val) == 0) {
                fnvlist_add_nvlist(propval, ZPROP_VALUE, val);
                fnvlist_add_nvlist(nv, zfs_prop_to_name(ZFS_PROP_CLONES),
                    propval);
        }

        nvlist_free(val);
        nvlist_free(propval);
}

static char *
get_receive_resume_token_impl(dsl_dataset_t *ds)
{
        if (!dsl_dataset_has_resume_receive_state(ds))
                return (NULL);

        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        char *str;
        void *packed;
        uint8_t *compressed;
        uint64_t val;
        nvlist_t *token_nv = fnvlist_alloc();
        size_t packed_size, compressed_size;

        if (zap_lookup(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_FROMGUID, sizeof (val), 1, &val) == 0) {
                fnvlist_add_uint64(token_nv, "fromguid", val);
        }
        if (zap_lookup(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_OBJECT, sizeof (val), 1, &val) == 0) {
                fnvlist_add_uint64(token_nv, "object", val);
        }
        if (zap_lookup(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_OFFSET, sizeof (val), 1, &val) == 0) {
                fnvlist_add_uint64(token_nv, "offset", val);
        }
        if (zap_lookup(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_BYTES, sizeof (val), 1, &val) == 0) {
                fnvlist_add_uint64(token_nv, "bytes", val);
        }
        if (zap_lookup(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_TOGUID, sizeof (val), 1, &val) == 0) {
                fnvlist_add_uint64(token_nv, "toguid", val);
        }
        char buf[MAXNAMELEN];
        if (zap_lookup(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_TONAME, 1, sizeof (buf), buf) == 0) {
                fnvlist_add_string(token_nv, "toname", buf);
        }
        if (zap_contains(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_LARGEBLOCK) == 0) {
                fnvlist_add_boolean(token_nv, "largeblockok");
        }
        if (zap_contains(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_EMBEDOK) == 0) {
                fnvlist_add_boolean(token_nv, "embedok");
        }
        if (zap_contains(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_COMPRESSOK) == 0) {
                fnvlist_add_boolean(token_nv, "compressok");
        }
        if (zap_contains(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_RAWOK) == 0) {
                fnvlist_add_boolean(token_nv, "rawok");
        }
        if (dsl_dataset_feature_is_active(ds,
            SPA_FEATURE_REDACTED_DATASETS)) {
                uint64_t num_redact_snaps = 0;
                uint64_t *redact_snaps = NULL;
                VERIFY3B(dsl_dataset_get_uint64_array_feature(ds,
                    SPA_FEATURE_REDACTED_DATASETS, &num_redact_snaps,
                    &redact_snaps), ==, B_TRUE);
                fnvlist_add_uint64_array(token_nv, "redact_snaps",
                    redact_snaps, num_redact_snaps);
        }
        if (zap_contains(dp->dp_meta_objset, ds->ds_object,
            DS_FIELD_RESUME_REDACT_BOOKMARK_SNAPS) == 0) {
                uint64_t num_redact_snaps = 0, int_size = 0;
                uint64_t *redact_snaps = NULL;
                VERIFY0(zap_length(dp->dp_meta_objset, ds->ds_object,
                    DS_FIELD_RESUME_REDACT_BOOKMARK_SNAPS, &int_size,
                    &num_redact_snaps));
                ASSERT3U(int_size, ==, sizeof (uint64_t));

                redact_snaps = kmem_alloc(int_size * num_redact_snaps,
                    KM_SLEEP);
                VERIFY0(zap_lookup(dp->dp_meta_objset, ds->ds_object,
                    DS_FIELD_RESUME_REDACT_BOOKMARK_SNAPS, int_size,
                    num_redact_snaps, redact_snaps));
                fnvlist_add_uint64_array(token_nv, "book_redact_snaps",
                    redact_snaps, num_redact_snaps);
                kmem_free(redact_snaps, int_size * num_redact_snaps);
        }
        packed = fnvlist_pack(token_nv, &packed_size);
        fnvlist_free(token_nv);
        compressed = kmem_alloc(packed_size, KM_SLEEP);

        /* Call compress function directly to avoid hole detection. */
        abd_t pabd, cabd;
        abd_get_from_buf_struct(&pabd, packed, packed_size);
        abd_get_from_buf_struct(&cabd, compressed, packed_size);
        compressed_size = zfs_gzip_compress(&pabd, &cabd,
            packed_size, packed_size, 6);
        abd_free(&cabd);
        abd_free(&pabd);

        zio_cksum_t cksum;
        fletcher_4_native_varsize(compressed, compressed_size, &cksum);

        size_t alloc_size = compressed_size * 2 + 1;
        str = kmem_alloc(alloc_size, KM_SLEEP);
        for (int i = 0; i < compressed_size; i++) {
                size_t offset = i * 2;
                (void) snprintf(str + offset, alloc_size - offset,
            "%02x", compressed[i]);
        }
        str[compressed_size * 2] = '\0';
        char *propval = kmem_asprintf("%u-%llx-%llx-%s",
            ZFS_SEND_RESUME_TOKEN_VERSION,
            (longlong_t)cksum.zc_word[0],
            (longlong_t)packed_size, str);
        kmem_free(packed, packed_size);
        kmem_free(str, alloc_size);
        kmem_free(compressed, packed_size);
        return (propval);
}

/*
 * Returns a string that represents the receive resume state token. It should
 * be freed with strfree(). NULL is returned if no resume state is present.
 */
char *
get_receive_resume_token(dsl_dataset_t *ds)
{
        /*
         * A failed "newfs" (e.g. full) resumable receive leaves
         * the stats set on this dataset.  Check here for the prop.
         */
        char *token = get_receive_resume_token_impl(ds);
        if (token != NULL)
                return (token);
        /*
         * A failed incremental resumable receive leaves the
         * stats set on our child named "%recv".  Check the child
         * for the prop.
         */
        /* 6 extra bytes for /%recv */
        char name[ZFS_MAX_DATASET_NAME_LEN + 6];
        dsl_dataset_t *recv_ds;
        dsl_dataset_name(ds, name);
        if (strlcat(name, "/", sizeof (name)) < sizeof (name) &&
            strlcat(name, recv_clone_name, sizeof (name)) < sizeof (name) &&
            dsl_dataset_hold(ds->ds_dir->dd_pool, name, FTAG, &recv_ds) == 0) {
                token = get_receive_resume_token_impl(recv_ds);
                dsl_dataset_rele(recv_ds, FTAG);
        }
        return (token);
}

uint64_t
dsl_get_refratio(dsl_dataset_t *ds)
{
        uint64_t ratio = dsl_dataset_phys(ds)->ds_compressed_bytes == 0 ? 100 :
            (dsl_dataset_phys(ds)->ds_uncompressed_bytes * 100 /
            dsl_dataset_phys(ds)->ds_compressed_bytes);
        return (ratio);
}

uint64_t
dsl_get_logicalreferenced(dsl_dataset_t *ds)
{
        return (dsl_dataset_phys(ds)->ds_uncompressed_bytes);
}

uint64_t
dsl_get_compressratio(dsl_dataset_t *ds)
{
        if (ds->ds_is_snapshot) {
                return (dsl_get_refratio(ds));
        } else {
                dsl_dir_t *dd = ds->ds_dir;
                mutex_enter(&dd->dd_lock);
                uint64_t val = dsl_dir_get_compressratio(dd);
                mutex_exit(&dd->dd_lock);
                return (val);
        }
}

uint64_t
dsl_get_used(dsl_dataset_t *ds)
{
        if (ds->ds_is_snapshot) {
                return (dsl_dataset_phys(ds)->ds_unique_bytes);
        } else {
                dsl_dir_t *dd = ds->ds_dir;
                mutex_enter(&dd->dd_lock);
                uint64_t val = dsl_dir_get_used(dd);
                mutex_exit(&dd->dd_lock);
                return (val);
        }
}

uint64_t
dsl_get_creation(dsl_dataset_t *ds)
{
        return (dsl_dataset_phys(ds)->ds_creation_time);
}

uint64_t
dsl_get_creationtxg(dsl_dataset_t *ds)
{
        return (dsl_dataset_phys(ds)->ds_creation_txg);
}

uint64_t
dsl_get_refquota(dsl_dataset_t *ds)
{
        return (ds->ds_quota);
}

uint64_t
dsl_get_refreservation(dsl_dataset_t *ds)
{
        return (ds->ds_reserved);
}

uint64_t
dsl_get_guid(dsl_dataset_t *ds)
{
        return (dsl_dataset_phys(ds)->ds_guid);
}

uint64_t
dsl_get_unique(dsl_dataset_t *ds)
{
        return (dsl_dataset_phys(ds)->ds_unique_bytes);
}

uint64_t
dsl_get_objsetid(dsl_dataset_t *ds)
{
        return (ds->ds_object);
}

uint64_t
dsl_get_userrefs(dsl_dataset_t *ds)
{
        return (ds->ds_userrefs);
}

uint64_t
dsl_get_defer_destroy(dsl_dataset_t *ds)
{
        return (DS_IS_DEFER_DESTROY(ds) ? 1 : 0);
}

uint64_t
dsl_get_referenced(dsl_dataset_t *ds)
{
        return (dsl_dataset_phys(ds)->ds_referenced_bytes);
}

uint64_t
dsl_get_numclones(dsl_dataset_t *ds)
{
        ASSERT(ds->ds_is_snapshot);
        return (dsl_dataset_phys(ds)->ds_num_children - 1);
}

uint64_t
dsl_get_inconsistent(dsl_dataset_t *ds)
{
        return ((dsl_dataset_phys(ds)->ds_flags & DS_FLAG_INCONSISTENT) ?
            1 : 0);
}

uint64_t
dsl_get_redacted(dsl_dataset_t *ds)
{
        return (dsl_dataset_feature_is_active(ds,
            SPA_FEATURE_REDACTED_DATASETS));
}

uint64_t
dsl_get_available(dsl_dataset_t *ds)
{
        uint64_t refdbytes = dsl_get_referenced(ds);
        uint64_t availbytes = dsl_dir_space_available(ds->ds_dir,
            NULL, 0, TRUE);
        if (ds->ds_reserved > dsl_dataset_phys(ds)->ds_unique_bytes) {
                availbytes +=
                    ds->ds_reserved - dsl_dataset_phys(ds)->ds_unique_bytes;
        }
        if (ds->ds_quota != 0) {
                /*
                 * Adjust available bytes according to refquota
                 */
                if (refdbytes < ds->ds_quota) {
                        availbytes = MIN(availbytes,
                            ds->ds_quota - refdbytes);
                } else {
                        availbytes = 0;
                }
        }
        return (availbytes);
}

int
dsl_get_written(dsl_dataset_t *ds, uint64_t *written)
{
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        dsl_dataset_t *prev;
        int err = dsl_dataset_hold_obj(dp,
            dsl_dataset_phys(ds)->ds_prev_snap_obj, FTAG, &prev);
        if (err == 0) {
                uint64_t comp, uncomp;
                err = dsl_dataset_space_written(prev, ds, written,
                    &comp, &uncomp);
                dsl_dataset_rele(prev, FTAG);
        }
        return (err);
}

/*
 * 'snap' should be a buffer of size ZFS_MAX_DATASET_NAME_LEN.
 */
int
dsl_get_prev_snap(dsl_dataset_t *ds, char *snap)
{
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        if (ds->ds_prev != NULL && ds->ds_prev != dp->dp_origin_snap) {
                dsl_dataset_name(ds->ds_prev, snap);
                return (0);
        } else {
                return (SET_ERROR(ENOENT));
        }
}

void
dsl_get_redact_snaps(dsl_dataset_t *ds, nvlist_t *propval)
{
        uint64_t nsnaps;
        uint64_t *snaps;
        if (dsl_dataset_get_uint64_array_feature(ds,
            SPA_FEATURE_REDACTED_DATASETS, &nsnaps, &snaps)) {
                fnvlist_add_uint64_array(propval, ZPROP_VALUE, snaps,
                    nsnaps);
        }
}

/*
 * Returns the mountpoint property and source for the given dataset in the value
 * and source buffers. The value buffer must be at least as large as MAXPATHLEN
 * and the source buffer as least as large a ZFS_MAX_DATASET_NAME_LEN.
 * Returns 0 on success and an error on failure.
 */
int
dsl_get_mountpoint(dsl_dataset_t *ds, const char *dsname, char *value,
    char *source)
{
        int error;
        dsl_pool_t *dp = ds->ds_dir->dd_pool;

        /* Retrieve the mountpoint value stored in the zap object */
        error = dsl_prop_get_ds(ds, zfs_prop_to_name(ZFS_PROP_MOUNTPOINT), 1,
            ZAP_MAXVALUELEN, value, source);
        if (error != 0) {
                return (error);
        }

        /*
         * Process the dsname and source to find the full mountpoint string.
         * Can be skipped for 'legacy' or 'none'.
         */
        if (value[0] == '/') {
                char *buf = kmem_alloc(ZAP_MAXVALUELEN, KM_SLEEP);
                char *root = buf;
                const char *relpath;

                /*
                 * If we inherit the mountpoint, even from a dataset
                 * with a received value, the source will be the path of
                 * the dataset we inherit from. If source is
                 * ZPROP_SOURCE_VAL_RECVD, the received value is not
                 * inherited.
                 */
                if (strcmp(source, ZPROP_SOURCE_VAL_RECVD) == 0) {
                        relpath = "";
                } else {
                        ASSERT0(strncmp(dsname, source, strlen(source)));
                        relpath = dsname + strlen(source);
                        if (relpath[0] == '/')
                                relpath++;
                }

                spa_altroot(dp->dp_spa, root, ZAP_MAXVALUELEN);

                /*
                 * Special case an alternate root of '/'. This will
                 * avoid having multiple leading slashes in the
                 * mountpoint path.
                 */
                if (strcmp(root, "/") == 0)
                        root++;

                /*
                 * If the mountpoint is '/' then skip over this
                 * if we are obtaining either an alternate root or
                 * an inherited mountpoint.
                 */
                char *mnt = value;
                if (value[1] == '\0' && (root[0] != '\0' ||
                    relpath[0] != '\0'))
                        mnt = value + 1;

                mnt = kmem_strdup(mnt);

                if (relpath[0] == '\0') {
                        (void) snprintf(value, ZAP_MAXVALUELEN, "%s%s",
                            root, mnt);
                } else {
                        (void) snprintf(value, ZAP_MAXVALUELEN, "%s%s%s%s",
                            root, mnt, relpath[0] == '@' ? "" : "/",
                            relpath);
                }
                kmem_free(buf, ZAP_MAXVALUELEN);
                kmem_strfree(mnt);
        }

        return (0);
}

void
dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
{
        dsl_pool_t *dp __maybe_unused = ds->ds_dir->dd_pool;

        ASSERT(dsl_pool_config_held(dp));

        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFRATIO,
            dsl_get_refratio(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_LOGICALREFERENCED,
            dsl_get_logicalreferenced(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_COMPRESSRATIO,
            dsl_get_compressratio(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USED,
            dsl_get_used(ds));

        if (ds->ds_is_snapshot) {
                get_clones_stat(ds, nv);
        } else {
                char buf[ZFS_MAX_DATASET_NAME_LEN];
                if (dsl_get_prev_snap(ds, buf) == 0)
                        dsl_prop_nvlist_add_string(nv, ZFS_PROP_PREV_SNAP,
                            buf);
                dsl_dir_stats(ds->ds_dir, nv);
        }

        nvlist_t *propval = fnvlist_alloc();
        dsl_get_redact_snaps(ds, propval);
        fnvlist_add_nvlist(nv, zfs_prop_to_name(ZFS_PROP_REDACT_SNAPS),
            propval);
        nvlist_free(propval);

        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_AVAILABLE,
            dsl_get_available(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFERENCED,
            dsl_get_referenced(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_CREATION,
            dsl_get_creation(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_CREATETXG,
            dsl_get_creationtxg(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFQUOTA,
            dsl_get_refquota(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFRESERVATION,
            dsl_get_refreservation(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_GUID,
            dsl_get_guid(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_UNIQUE,
            dsl_get_unique(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_OBJSETID,
            dsl_get_objsetid(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USERREFS,
            dsl_get_userrefs(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_DEFER_DESTROY,
            dsl_get_defer_destroy(ds));
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_SNAPSHOTS_CHANGED,
            dsl_dir_snap_cmtime(ds->ds_dir).tv_sec);
        dsl_dataset_crypt_stats(ds, nv);

        if (dsl_dataset_phys(ds)->ds_prev_snap_obj != 0) {
                uint64_t written;
                if (dsl_get_written(ds, &written) == 0) {
                        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_WRITTEN,
                            written);
                }
        }

        if (!dsl_dataset_is_snapshot(ds)) {
                char *token = get_receive_resume_token(ds);
                if (token != NULL) {
                        dsl_prop_nvlist_add_string(nv,
                            ZFS_PROP_RECEIVE_RESUME_TOKEN, token);
                        kmem_strfree(token);
                }
        }
}

void
dsl_dataset_fast_stat(dsl_dataset_t *ds, dmu_objset_stats_t *stat)
{
        dsl_pool_t *dp __maybe_unused = ds->ds_dir->dd_pool;
        ASSERT(dsl_pool_config_held(dp));

        stat->dds_creation_txg = dsl_get_creationtxg(ds);
        stat->dds_inconsistent = dsl_get_inconsistent(ds);
        stat->dds_guid = dsl_get_guid(ds);
        stat->dds_redacted = dsl_get_redacted(ds);
        stat->dds_origin[0] = '\0';
        if (ds->ds_is_snapshot) {
                stat->dds_is_snapshot = B_TRUE;
                stat->dds_num_clones = dsl_get_numclones(ds);
        } else {
                stat->dds_is_snapshot = B_FALSE;
                stat->dds_num_clones = 0;

                if (dsl_dir_is_clone(ds->ds_dir)) {
                        dsl_dir_get_origin(ds->ds_dir, stat->dds_origin);
                }
        }
}

uint64_t
dsl_dataset_fsid_guid(dsl_dataset_t *ds)
{
        return (ds->ds_fsid_guid);
}

void
dsl_dataset_space(dsl_dataset_t *ds,
    uint64_t *refdbytesp, uint64_t *availbytesp,
    uint64_t *usedobjsp, uint64_t *availobjsp)
{
        *refdbytesp = dsl_dataset_phys(ds)->ds_referenced_bytes;
        *availbytesp = dsl_dir_space_available(ds->ds_dir, NULL, 0, TRUE);
        if (ds->ds_reserved > dsl_dataset_phys(ds)->ds_unique_bytes)
                *availbytesp +=
                    ds->ds_reserved - dsl_dataset_phys(ds)->ds_unique_bytes;
        if (ds->ds_quota != 0) {
                /*
                 * Adjust available bytes according to refquota
                 */
                if (*refdbytesp < ds->ds_quota)
                        *availbytesp = MIN(*availbytesp,
                            ds->ds_quota - *refdbytesp);
                else
                        *availbytesp = 0;
        }
        rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
        *usedobjsp = BP_GET_FILL(&dsl_dataset_phys(ds)->ds_bp);
        rrw_exit(&ds->ds_bp_rwlock, FTAG);
        *availobjsp = DN_MAX_OBJECT - *usedobjsp;
}

boolean_t
dsl_dataset_modified_since_snap(dsl_dataset_t *ds, dsl_dataset_t *snap)
{
        dsl_pool_t *dp __maybe_unused = ds->ds_dir->dd_pool;
        uint64_t birth;

        ASSERT(dsl_pool_config_held(dp));
        if (snap == NULL)
                return (B_FALSE);
        rrw_enter(&ds->ds_bp_rwlock, RW_READER, FTAG);
        birth = BP_GET_LOGICAL_BIRTH(dsl_dataset_get_blkptr(ds));
        rrw_exit(&ds->ds_bp_rwlock, FTAG);
        if (birth > dsl_dataset_phys(snap)->ds_creation_txg) {
                objset_t *os, *os_snap;
                /*
                 * It may be that only the ZIL differs, because it was
                 * reset in the head.  Don't count that as being
                 * modified.
                 */
                if (dmu_objset_from_ds(ds, &os) != 0)
                        return (B_TRUE);
                if (dmu_objset_from_ds(snap, &os_snap) != 0)
                        return (B_TRUE);
                return (memcmp(&os->os_phys->os_meta_dnode,
                    &os_snap->os_phys->os_meta_dnode,
                    sizeof (os->os_phys->os_meta_dnode)) != 0);
        }
        return (B_FALSE);
}

static int
dsl_dataset_rename_snapshot_check_impl(dsl_pool_t *dp,
    dsl_dataset_t *hds, void *arg)
{
        (void) dp;
        dsl_dataset_rename_snapshot_arg_t *ddrsa = arg;
        int error;
        uint64_t val;

        error = dsl_dataset_snap_lookup(hds, ddrsa->ddrsa_oldsnapname, &val);
        if (error != 0) {
                /* ignore nonexistent snapshots */
                return (error == ENOENT ? 0 : error);
        }

        /* new name should not exist */
        error = dsl_dataset_snap_lookup(hds, ddrsa->ddrsa_newsnapname, &val);
        if (error == 0)
                error = SET_ERROR(EEXIST);
        else if (error == ENOENT)
                error = 0;

        /* dataset name + 1 for the "@" + the new snapshot name must fit */
        if (dsl_dir_namelen(hds->ds_dir) + 1 +
            strlen(ddrsa->ddrsa_newsnapname) >= ZFS_MAX_DATASET_NAME_LEN)
                error = SET_ERROR(ENAMETOOLONG);

        return (error);
}

int
dsl_dataset_rename_snapshot_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_rename_snapshot_arg_t *ddrsa = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *hds;
        int error;

        error = dsl_dataset_hold(dp, ddrsa->ddrsa_fsname, FTAG, &hds);
        if (error != 0)
                return (error);

        if (ddrsa->ddrsa_recursive) {
                error = dmu_objset_find_dp(dp, hds->ds_dir->dd_object,
                    dsl_dataset_rename_snapshot_check_impl, ddrsa,
                    DS_FIND_CHILDREN);
        } else {
                error = dsl_dataset_rename_snapshot_check_impl(dp, hds, ddrsa);
        }
        dsl_dataset_rele(hds, FTAG);
        return (error);
}

static int
dsl_dataset_rename_snapshot_sync_impl(dsl_pool_t *dp,
    dsl_dataset_t *hds, void *arg)
{
        dsl_dataset_rename_snapshot_arg_t *ddrsa = arg;
        dsl_dataset_t *ds;
        uint64_t val;
        dmu_tx_t *tx = ddrsa->ddrsa_tx;
        char *oldname, *newname;
        int error;

        error = dsl_dataset_snap_lookup(hds, ddrsa->ddrsa_oldsnapname, &val);
        ASSERT(error == 0 || error == ENOENT);
        if (error == ENOENT) {
                /* ignore nonexistent snapshots */
                return (0);
        }

        VERIFY0(dsl_dataset_hold_obj(dp, val, FTAG, &ds));

        /* log before we change the name */
        spa_history_log_internal_ds(ds, "rename", tx,
            "-> @%s", ddrsa->ddrsa_newsnapname);

        VERIFY0(dsl_dataset_snap_remove(hds, ddrsa->ddrsa_oldsnapname, tx,
            B_FALSE));
        mutex_enter(&ds->ds_lock);
        (void) strlcpy(ds->ds_snapname, ddrsa->ddrsa_newsnapname,
            sizeof (ds->ds_snapname));
        mutex_exit(&ds->ds_lock);
        VERIFY0(zap_add(dp->dp_meta_objset,
            dsl_dataset_phys(hds)->ds_snapnames_zapobj,
            ds->ds_snapname, 8, 1, &ds->ds_object, tx));

        oldname = kmem_asprintf("%s@%s", ddrsa->ddrsa_fsname,
            ddrsa->ddrsa_oldsnapname);
        newname = kmem_asprintf("%s@%s", ddrsa->ddrsa_fsname,
            ddrsa->ddrsa_newsnapname);
        zvol_rename_minors(dp->dp_spa, oldname, newname, B_TRUE);
        kmem_strfree(oldname);
        kmem_strfree(newname);

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

void
dsl_dataset_rename_snapshot_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_rename_snapshot_arg_t *ddrsa = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *hds = NULL;

        VERIFY0(dsl_dataset_hold(dp, ddrsa->ddrsa_fsname, FTAG, &hds));
        ddrsa->ddrsa_tx = tx;
        if (ddrsa->ddrsa_recursive) {
                VERIFY0(dmu_objset_find_dp(dp, hds->ds_dir->dd_object,
                    dsl_dataset_rename_snapshot_sync_impl, ddrsa,
                    DS_FIND_CHILDREN));
        } else {
                VERIFY0(dsl_dataset_rename_snapshot_sync_impl(dp, hds, ddrsa));
        }
        dsl_dataset_rele(hds, FTAG);
}

int
dsl_dataset_rename_snapshot(const char *fsname,
    const char *oldsnapname, const char *newsnapname, boolean_t recursive)
{
        dsl_dataset_rename_snapshot_arg_t ddrsa;

        ddrsa.ddrsa_fsname = fsname;
        ddrsa.ddrsa_oldsnapname = oldsnapname;
        ddrsa.ddrsa_newsnapname = newsnapname;
        ddrsa.ddrsa_recursive = recursive;

        return (dsl_sync_task(fsname, dsl_dataset_rename_snapshot_check,
            dsl_dataset_rename_snapshot_sync, &ddrsa,
            1, ZFS_SPACE_CHECK_RESERVED));
}

/*
 * If we're doing an ownership handoff, we need to make sure that there is
 * only one long hold on the dataset.  We're not allowed to change anything here
 * so we don't permanently release the long hold or regular hold here.  We want
 * to do this only when syncing to avoid the dataset unexpectedly going away
 * when we release the long hold.
 */
static int
dsl_dataset_handoff_check(dsl_dataset_t *ds, void *owner, dmu_tx_t *tx)
{
        boolean_t held = B_FALSE;

        if (!dmu_tx_is_syncing(tx))
                return (0);

        dsl_dir_t *dd = ds->ds_dir;
        mutex_enter(&dd->dd_activity_lock);
        uint64_t holds = zfs_refcount_count(&ds->ds_longholds) -
            (owner != NULL ? 1 : 0);
        /*
         * The value of dd_activity_waiters can chance as soon as we drop the
         * lock, but we're fine with that; new waiters coming in or old
         * waiters leaving doesn't cause problems, since we're going to cancel
         * waiters later anyway. The goal of this check is to verify that no
         * non-waiters have long-holds, and all new long-holds will be
         * prevented because we're holding the pool config as writer.
         */
        if (holds != dd->dd_activity_waiters)
                held = B_TRUE;
        mutex_exit(&dd->dd_activity_lock);

        if (held)
                return (SET_ERROR(EBUSY));

        return (0);
}

int
dsl_dataset_rollback_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_rollback_arg_t *ddra = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds;
        int64_t unused_refres_delta;
        int error;

        error = dsl_dataset_hold(dp, ddra->ddra_fsname, FTAG, &ds);
        if (error != 0)
                return (error);

        /* must not be a snapshot */
        if (ds->ds_is_snapshot) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(EINVAL));
        }

        /* must have a most recent snapshot */
        if (dsl_dataset_phys(ds)->ds_prev_snap_txg < TXG_INITIAL) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(ESRCH));
        }

        /*
         * No rollback to a snapshot created in the current txg, because
         * the rollback may dirty the dataset and create blocks that are
         * not reachable from the rootbp while having a birth txg that
         * falls into the snapshot's range.
         */
        if (dmu_tx_is_syncing(tx) &&
            dsl_dataset_phys(ds)->ds_prev_snap_txg >= tx->tx_txg) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(EAGAIN));
        }

        /*
         * If the expected target snapshot is specified, then check that
         * the latest snapshot is it.
         */
        if (ddra->ddra_tosnap != NULL) {
                dsl_dataset_t *snapds;

                /* Check if the target snapshot exists at all. */
                error = dsl_dataset_hold(dp, ddra->ddra_tosnap, FTAG, &snapds);
                if (error != 0) {
                        /*
                         * ESRCH is used to signal that the target snapshot does
                         * not exist, while ENOENT is used to report that
                         * the rolled back dataset does not exist.
                         * ESRCH is also used to cover other cases where the
                         * target snapshot is not related to the dataset being
                         * rolled back such as being in a different pool.
                         */
                        if (error == ENOENT || error == EXDEV)
                                error = SET_ERROR(ESRCH);
                        dsl_dataset_rele(ds, FTAG);
                        return (error);
                }
                ASSERT(snapds->ds_is_snapshot);

                /* Check if the snapshot is the latest snapshot indeed. */
                if (snapds != ds->ds_prev) {
                        /*
                         * Distinguish between the case where the only problem
                         * is intervening snapshots (EEXIST) vs the snapshot
                         * not being a valid target for rollback (ESRCH).
                         */
                        if (snapds->ds_dir == ds->ds_dir ||
                            (dsl_dir_is_clone(ds->ds_dir) &&
                            dsl_dir_phys(ds->ds_dir)->dd_origin_obj ==
                            snapds->ds_object)) {
                                error = SET_ERROR(EEXIST);
                        } else {
                                error = SET_ERROR(ESRCH);
                        }
                        dsl_dataset_rele(snapds, FTAG);
                        dsl_dataset_rele(ds, FTAG);
                        return (error);
                }
                dsl_dataset_rele(snapds, FTAG);
        }

        /* must not have any bookmarks after the most recent snapshot */
        if (dsl_bookmark_latest_txg(ds) >
            dsl_dataset_phys(ds)->ds_prev_snap_txg) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(EEXIST));
        }

        error = dsl_dataset_handoff_check(ds, ddra->ddra_owner, tx);
        if (error != 0) {
                dsl_dataset_rele(ds, FTAG);
                return (error);
        }

        /*
         * Check if the snap we are rolling back to uses more than
         * the refquota.
         */
        if (ds->ds_quota != 0 &&
            dsl_dataset_phys(ds->ds_prev)->ds_referenced_bytes > ds->ds_quota) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(EDQUOT));
        }

        /*
         * When we do the clone swap, we will temporarily use more space
         * due to the refreservation (the head will no longer have any
         * unique space, so the entire amount of the refreservation will need
         * to be free).  We will immediately destroy the clone, freeing
         * this space, but the freeing happens over many txg's.
         */
        unused_refres_delta = (int64_t)MIN(ds->ds_reserved,
            dsl_dataset_phys(ds)->ds_unique_bytes);

        if (unused_refres_delta > 0 &&
            unused_refres_delta >
            dsl_dir_space_available(ds->ds_dir, NULL, 0, TRUE)) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(ENOSPC));
        }

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

void
dsl_dataset_rollback_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_rollback_arg_t *ddra = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds, *clone;
        uint64_t cloneobj;
        char namebuf[ZFS_MAX_DATASET_NAME_LEN];

        VERIFY0(dsl_dataset_hold(dp, ddra->ddra_fsname, FTAG, &ds));

        dsl_dataset_name(ds->ds_prev, namebuf);
        fnvlist_add_string(ddra->ddra_result, "target", namebuf);

        cloneobj = dsl_dataset_create_sync(ds->ds_dir, "%rollback",
            ds->ds_prev, DS_CREATE_FLAG_NODIRTY, kcred, NULL, tx);

        VERIFY0(dsl_dataset_hold_obj(dp, cloneobj, FTAG, &clone));

        dsl_dataset_clone_swap_sync_impl(clone, ds, tx);
        dsl_dataset_zero_zil(ds, tx);

        dsl_destroy_head_sync_impl(clone, tx);

        dsl_dataset_rele(clone, FTAG);
        dsl_dataset_rele(ds, FTAG);
}

/*
 * Rolls back the given filesystem or volume to the most recent snapshot.
 * The name of the most recent snapshot will be returned under key "target"
 * in the result nvlist.
 *
 * If owner != NULL:
 * - The existing dataset MUST be owned by the specified owner at entry
 * - Upon return, dataset will still be held by the same owner, whether we
 *   succeed or not.
 *
 * This mode is required any time the existing filesystem is mounted.  See
 * notes above zfs_suspend_fs() for further details.
 */
int
dsl_dataset_rollback(const char *fsname, const char *tosnap, void *owner,
    nvlist_t *result)
{
        dsl_dataset_rollback_arg_t ddra;

        ddra.ddra_fsname = fsname;
        ddra.ddra_tosnap = tosnap;
        ddra.ddra_owner = owner;
        ddra.ddra_result = result;

        return (dsl_sync_task(fsname, dsl_dataset_rollback_check,
            dsl_dataset_rollback_sync, &ddra,
            1, ZFS_SPACE_CHECK_RESERVED));
}

struct promotenode {
        list_node_t link;
        dsl_dataset_t *ds;
};

static int snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep);
static int promote_hold(dsl_dataset_promote_arg_t *ddpa, dsl_pool_t *dp,
    const void *tag);
static void promote_rele(dsl_dataset_promote_arg_t *ddpa, const void *tag);

int
dsl_dataset_promote_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_promote_arg_t *ddpa = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *hds;
        struct promotenode *snap;
        int err;
        uint64_t unused;
        uint64_t ss_mv_cnt;
        size_t max_snap_len;
        boolean_t conflicting_snaps;

        err = promote_hold(ddpa, dp, FTAG);
        if (err != 0)
                return (err);

        hds = ddpa->ddpa_clone;
        max_snap_len = MAXNAMELEN - strlen(ddpa->ddpa_clonename) - 1;

        if (dsl_dataset_phys(hds)->ds_flags & DS_FLAG_NOPROMOTE) {
                promote_rele(ddpa, FTAG);
                return (SET_ERROR(EXDEV));
        }

        snap = list_head(&ddpa->shared_snaps);
        if (snap == NULL) {
                err = SET_ERROR(ENOENT);
                goto out;
        }
        dsl_dataset_t *const origin_ds = snap->ds;

        /*
         * Encrypted clones share a DSL Crypto Key with their origin's dsl dir.
         * When doing a promote we must make sure the encryption root for
         * both the target and the target's origin does not change to avoid
         * needing to rewrap encryption keys
         */
        err = dsl_dataset_promote_crypt_check(hds->ds_dir, origin_ds->ds_dir);
        if (err != 0)
                goto out;

        /*
         * Compute and check the amount of space to transfer.  Since this is
         * so expensive, don't do the preliminary check.
         */
        if (!dmu_tx_is_syncing(tx)) {
                promote_rele(ddpa, FTAG);
                return (0);
        }

        /* compute origin's new unique space */
        snap = list_tail(&ddpa->clone_snaps);
        ASSERT(snap != NULL);
        ASSERT3U(dsl_dataset_phys(snap->ds)->ds_prev_snap_obj, ==,
            origin_ds->ds_object);
        dsl_deadlist_space_range(&snap->ds->ds_deadlist,
            dsl_dataset_phys(origin_ds)->ds_prev_snap_txg, UINT64_MAX,
            &ddpa->unique, &unused, &unused);

        /*
         * Walk the snapshots that we are moving
         *
         * Compute space to transfer.  Consider the incremental changes
         * to used by each snapshot:
         * (my used) = (prev's used) + (blocks born) - (blocks killed)
         * So each snapshot gave birth to:
         * (blocks born) = (my used) - (prev's used) + (blocks killed)
         * So a sequence would look like:
         * (uN - u(N-1) + kN) + ... + (u1 - u0 + k1) + (u0 - 0 + k0)
         * Which simplifies to:
         * uN + kN + kN-1 + ... + k1 + k0
         * Note however, if we stop before we reach the ORIGIN we get:
         * uN + kN + kN-1 + ... + kM - uM-1
         */
        conflicting_snaps = B_FALSE;
        ss_mv_cnt = 0;
        ddpa->used = dsl_dataset_phys(origin_ds)->ds_referenced_bytes;
        ddpa->comp = dsl_dataset_phys(origin_ds)->ds_compressed_bytes;
        ddpa->uncomp = dsl_dataset_phys(origin_ds)->ds_uncompressed_bytes;
        for (snap = list_head(&ddpa->shared_snaps); snap;
            snap = list_next(&ddpa->shared_snaps, snap)) {
                uint64_t val, dlused, dlcomp, dluncomp;
                dsl_dataset_t *ds = snap->ds;

                ss_mv_cnt++;

                /*
                 * If there are long holds, we won't be able to evict
                 * the objset.
                 */
                if (dsl_dataset_long_held(ds)) {
                        err = SET_ERROR(EBUSY);
                        goto out;
                }

                /* Check that the snapshot name does not conflict */
                VERIFY0(dsl_dataset_get_snapname(ds));
                if (strlen(ds->ds_snapname) >= max_snap_len) {
                        err = SET_ERROR(ENAMETOOLONG);
                        goto out;
                }
                err = dsl_dataset_snap_lookup(hds, ds->ds_snapname, &val);
                if (err == 0) {
                        fnvlist_add_boolean(ddpa->err_ds,
                            snap->ds->ds_snapname);
                        conflicting_snaps = B_TRUE;
                } else if (err != ENOENT) {
                        goto out;
                }

                /* The very first snapshot does not have a deadlist */
                if (dsl_dataset_phys(ds)->ds_prev_snap_obj == 0)
                        continue;

                dsl_deadlist_space(&ds->ds_deadlist,
                    &dlused, &dlcomp, &dluncomp);
                ddpa->used += dlused;
                ddpa->comp += dlcomp;
                ddpa->uncomp += dluncomp;
        }

        /*
         * Check that bookmarks that are being transferred don't have
         * name conflicts.
         */
        for (dsl_bookmark_node_t *dbn = avl_first(&origin_ds->ds_bookmarks);
            dbn != NULL && dbn->dbn_phys.zbm_creation_txg <=
            dsl_dataset_phys(origin_ds)->ds_creation_txg;
            dbn = AVL_NEXT(&origin_ds->ds_bookmarks, dbn)) {
                if (strlen(dbn->dbn_name) >= max_snap_len) {
                        err = SET_ERROR(ENAMETOOLONG);
                        goto out;
                }
                zfs_bookmark_phys_t bm;
                err = dsl_bookmark_lookup_impl(ddpa->ddpa_clone,
                    dbn->dbn_name, &bm);

                if (err == 0) {
                        fnvlist_add_boolean(ddpa->err_ds, dbn->dbn_name);
                        conflicting_snaps = B_TRUE;
                } else if (err == ESRCH) {
                        err = 0;
                }
                if (err != 0) {
                        goto out;
                }
        }

        /*
         * In order to return the full list of conflicting snapshots, we check
         * whether there was a conflict after traversing all of them.
         */
        if (conflicting_snaps) {
                err = SET_ERROR(EEXIST);
                goto out;
        }

        /*
         * If we are a clone of a clone then we never reached ORIGIN,
         * so we need to subtract out the clone origin's used space.
         */
        if (ddpa->origin_origin) {
                ddpa->used -=
                    dsl_dataset_phys(ddpa->origin_origin)->ds_referenced_bytes;
                ddpa->comp -=
                    dsl_dataset_phys(ddpa->origin_origin)->ds_compressed_bytes;
                ddpa->uncomp -=
                    dsl_dataset_phys(ddpa->origin_origin)->
                    ds_uncompressed_bytes;
        }

        /* Check that there is enough space and limit headroom here */
        err = dsl_dir_transfer_possible(origin_ds->ds_dir, hds->ds_dir,
            0, ss_mv_cnt, ddpa->used, ddpa->cr, ddpa->proc);
        if (err != 0)
                goto out;

        /*
         * Compute the amounts of space that will be used by snapshots
         * after the promotion (for both origin and clone).  For each,
         * it is the amount of space that will be on all of their
         * deadlists (that was not born before their new origin).
         */
        if (dsl_dir_phys(hds->ds_dir)->dd_flags & DD_FLAG_USED_BREAKDOWN) {
                uint64_t space;

                /*
                 * Note, typically this will not be a clone of a clone,
                 * so dd_origin_txg will be < TXG_INITIAL, so
                 * these snaplist_space() -> dsl_deadlist_space_range()
                 * calls will be fast because they do not have to
                 * iterate over all bps.
                 */
                snap = list_head(&ddpa->origin_snaps);
                if (snap == NULL) {
                        err = SET_ERROR(ENOENT);
                        goto out;
                }
                err = snaplist_space(&ddpa->shared_snaps,
                    snap->ds->ds_dir->dd_origin_txg, &ddpa->cloneusedsnap);
                if (err != 0)
                        goto out;

                err = snaplist_space(&ddpa->clone_snaps,
                    snap->ds->ds_dir->dd_origin_txg, &space);
                if (err != 0)
                        goto out;
                ddpa->cloneusedsnap += space;
        }
        if (dsl_dir_phys(origin_ds->ds_dir)->dd_flags &
            DD_FLAG_USED_BREAKDOWN) {
                err = snaplist_space(&ddpa->origin_snaps,
                    dsl_dataset_phys(origin_ds)->ds_creation_txg,
                    &ddpa->originusedsnap);
                if (err != 0)
                        goto out;
        }

out:
        promote_rele(ddpa, FTAG);
        return (err);
}

void
dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_promote_arg_t *ddpa = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *hds;
        struct promotenode *snap;
        dsl_dataset_t *origin_ds;
        dsl_dataset_t *origin_head;
        dsl_dir_t *dd;
        dsl_dir_t *odd = NULL;
        uint64_t oldnext_obj;
        int64_t delta;

        ASSERT(nvlist_empty(ddpa->err_ds));

        VERIFY0(promote_hold(ddpa, dp, FTAG));
        hds = ddpa->ddpa_clone;

        ASSERT0(dsl_dataset_phys(hds)->ds_flags & DS_FLAG_NOPROMOTE);

        snap = list_head(&ddpa->shared_snaps);
        origin_ds = snap->ds;
        dd = hds->ds_dir;

        snap = list_head(&ddpa->origin_snaps);
        origin_head = snap->ds;

        /*
         * We need to explicitly open odd, since origin_ds's dd will be
         * changing.
         */
        VERIFY0(dsl_dir_hold_obj(dp, origin_ds->ds_dir->dd_object,
            NULL, FTAG, &odd));

        dsl_dataset_promote_crypt_sync(hds->ds_dir, odd, tx);

        /* change origin's next snap */
        dmu_buf_will_dirty(origin_ds->ds_dbuf, tx);
        oldnext_obj = dsl_dataset_phys(origin_ds)->ds_next_snap_obj;
        snap = list_tail(&ddpa->clone_snaps);
        ASSERT3U(dsl_dataset_phys(snap->ds)->ds_prev_snap_obj, ==,
            origin_ds->ds_object);
        dsl_dataset_phys(origin_ds)->ds_next_snap_obj = snap->ds->ds_object;

        /* change the origin's next clone */
        if (dsl_dataset_phys(origin_ds)->ds_next_clones_obj) {
                dsl_dataset_remove_from_next_clones(origin_ds,
                    snap->ds->ds_object, tx);
                VERIFY0(zap_add_int(dp->dp_meta_objset,
                    dsl_dataset_phys(origin_ds)->ds_next_clones_obj,
                    oldnext_obj, tx));
        }

        /* change origin */
        dmu_buf_will_dirty(dd->dd_dbuf, tx);
        ASSERT3U(dsl_dir_phys(dd)->dd_origin_obj, ==, origin_ds->ds_object);
        dsl_dir_phys(dd)->dd_origin_obj = dsl_dir_phys(odd)->dd_origin_obj;
        dd->dd_origin_txg = origin_head->ds_dir->dd_origin_txg;
        dmu_buf_will_dirty(odd->dd_dbuf, tx);
        dsl_dir_phys(odd)->dd_origin_obj = origin_ds->ds_object;
        origin_head->ds_dir->dd_origin_txg =
            dsl_dataset_phys(origin_ds)->ds_creation_txg;

        /* change dd_clone entries */
        if (spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
                VERIFY0(zap_remove_int(dp->dp_meta_objset,
                    dsl_dir_phys(odd)->dd_clones, hds->ds_object, tx));
                VERIFY0(zap_add_int(dp->dp_meta_objset,
                    dsl_dir_phys(ddpa->origin_origin->ds_dir)->dd_clones,
                    hds->ds_object, tx));

                VERIFY0(zap_remove_int(dp->dp_meta_objset,
                    dsl_dir_phys(ddpa->origin_origin->ds_dir)->dd_clones,
                    origin_head->ds_object, tx));
                if (dsl_dir_phys(dd)->dd_clones == 0) {
                        dsl_dir_phys(dd)->dd_clones =
                            zap_create(dp->dp_meta_objset, DMU_OT_DSL_CLONES,
                            DMU_OT_NONE, 0, tx);
                }
                VERIFY0(zap_add_int(dp->dp_meta_objset,
                    dsl_dir_phys(dd)->dd_clones, origin_head->ds_object, tx));
        }

        /*
         * Move bookmarks to this dir.
         */
        dsl_bookmark_node_t *dbn_next;
        for (dsl_bookmark_node_t *dbn = avl_first(&origin_head->ds_bookmarks);
            dbn != NULL && dbn->dbn_phys.zbm_creation_txg <=
            dsl_dataset_phys(origin_ds)->ds_creation_txg;
            dbn = dbn_next) {
                dbn_next = AVL_NEXT(&origin_head->ds_bookmarks, dbn);

                avl_remove(&origin_head->ds_bookmarks, dbn);
                VERIFY0(zap_remove(dp->dp_meta_objset,
                    origin_head->ds_bookmarks_obj, dbn->dbn_name, tx));

                dsl_bookmark_node_add(hds, dbn, tx);
        }

        dsl_bookmark_next_changed(hds, origin_ds, tx);

        /* move snapshots to this dir */
        for (snap = list_head(&ddpa->shared_snaps); snap;
            snap = list_next(&ddpa->shared_snaps, snap)) {
                dsl_dataset_t *ds = snap->ds;

                /*
                 * Property callbacks are registered to a particular
                 * dsl_dir.  Since ours is changing, evict the objset
                 * so that they will be unregistered from the old dsl_dir.
                 */
                if (ds->ds_objset) {
                        dmu_objset_evict(ds->ds_objset);
                        ds->ds_objset = NULL;
                }

                /* move snap name entry */
                VERIFY0(dsl_dataset_get_snapname(ds));
                VERIFY0(dsl_dataset_snap_remove(origin_head,
                    ds->ds_snapname, tx, B_TRUE));
                VERIFY0(zap_add(dp->dp_meta_objset,
                    dsl_dataset_phys(hds)->ds_snapnames_zapobj, ds->ds_snapname,
                    8, 1, &ds->ds_object, tx));
                dsl_fs_ss_count_adjust(hds->ds_dir, 1,
                    DD_FIELD_SNAPSHOT_COUNT, tx);

                /* change containing dsl_dir */
                dmu_buf_will_dirty(ds->ds_dbuf, tx);
                ASSERT3U(dsl_dataset_phys(ds)->ds_dir_obj, ==, odd->dd_object);
                dsl_dataset_phys(ds)->ds_dir_obj = dd->dd_object;
                ASSERT3P(ds->ds_dir, ==, odd);
                dsl_dir_rele(ds->ds_dir, ds);
                VERIFY0(dsl_dir_hold_obj(dp, dd->dd_object,
                    NULL, ds, &ds->ds_dir));

                /* move any clone references */
                if (dsl_dataset_phys(ds)->ds_next_clones_obj &&
                    spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
                        zap_cursor_t zc;
                        zap_attribute_t *za = zap_attribute_alloc();

                        for (zap_cursor_init(&zc, dp->dp_meta_objset,
                            dsl_dataset_phys(ds)->ds_next_clones_obj);
                            zap_cursor_retrieve(&zc, za) == 0;
                            zap_cursor_advance(&zc)) {
                                dsl_dataset_t *cnds;
                                uint64_t o;

                                if (za->za_first_integer == oldnext_obj) {
                                        /*
                                         * We've already moved the
                                         * origin's reference.
                                         */
                                        continue;
                                }

                                VERIFY0(dsl_dataset_hold_obj(dp,
                                    za->za_first_integer, FTAG, &cnds));
                                o = dsl_dir_phys(cnds->ds_dir)->
                                    dd_head_dataset_obj;

                                VERIFY0(zap_remove_int(dp->dp_meta_objset,
                                    dsl_dir_phys(odd)->dd_clones, o, tx));
                                VERIFY0(zap_add_int(dp->dp_meta_objset,
                                    dsl_dir_phys(dd)->dd_clones, o, tx));
                                dsl_dataset_rele(cnds, FTAG);
                        }
                        zap_cursor_fini(&zc);
                        zap_attribute_free(za);
                }

                ASSERT(!dsl_prop_hascb(ds));
        }

        /*
         * Change space accounting.
         * Note, pa->*usedsnap and dd_used_breakdown[SNAP] will either
         * both be valid, or both be 0 (resulting in delta == 0).  This
         * is true for each of {clone,origin} independently.
         */

        delta = ddpa->cloneusedsnap -
            dsl_dir_phys(dd)->dd_used_breakdown[DD_USED_SNAP];
        ASSERT3S(delta, >=, 0);
        ASSERT3U(ddpa->used, >=, delta);
        dsl_dir_diduse_space(dd, DD_USED_SNAP, delta, 0, 0, tx);
        dsl_dir_diduse_space(dd, DD_USED_HEAD,
            ddpa->used - delta, ddpa->comp, ddpa->uncomp, tx);

        delta = ddpa->originusedsnap -
            dsl_dir_phys(odd)->dd_used_breakdown[DD_USED_SNAP];
        ASSERT3S(delta, <=, 0);
        ASSERT3U(ddpa->used, >=, -delta);
        dsl_dir_diduse_space(odd, DD_USED_SNAP, delta, 0, 0, tx);
        dsl_dir_diduse_space(odd, DD_USED_HEAD,
            -ddpa->used - delta, -ddpa->comp, -ddpa->uncomp, tx);

        dsl_dataset_phys(origin_ds)->ds_unique_bytes = ddpa->unique;

        /*
         * Since livelists are specific to a clone's origin txg, they
         * are no longer accurate. Destroy the livelist from the clone being
         * promoted. If the origin dataset is a clone, destroy its livelist
         * as well.
         */
        dsl_dir_remove_livelist(dd, tx, B_TRUE);
        dsl_dir_remove_livelist(odd, tx, B_TRUE);

        /* log history record */
        spa_history_log_internal_ds(hds, "promote", tx, " ");

        dsl_dir_rele(odd, FTAG);

        /*
         * Transfer common error blocks from old head to new head, before
         * calling promote_rele() on ddpa since we need to dereference
         * origin_head and hds.
         */
        if (spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_HEAD_ERRLOG)) {
                uint64_t old_head = origin_head->ds_object;
                uint64_t new_head = hds->ds_object;
                spa_swap_errlog(dp->dp_spa, new_head, old_head, tx);
        }

        promote_rele(ddpa, FTAG);
}

/*
 * Make a list of dsl_dataset_t's for the snapshots between first_obj
 * (exclusive) and last_obj (inclusive).  The list will be in reverse
 * order (last_obj will be the list_head()).  If first_obj == 0, do all
 * snapshots back to this dataset's origin.
 */
static int
snaplist_make(dsl_pool_t *dp,
    uint64_t first_obj, uint64_t last_obj, list_t *l, const void *tag)
{
        uint64_t obj = last_obj;

        list_create(l, sizeof (struct promotenode),
            offsetof(struct promotenode, link));

        while (obj != first_obj) {
                dsl_dataset_t *ds;
                struct promotenode *snap;
                int err;

                err = dsl_dataset_hold_obj(dp, obj, tag, &ds);
                ASSERT(err != ENOENT);
                if (err != 0)
                        return (err);

                if (first_obj == 0)
                        first_obj = dsl_dir_phys(ds->ds_dir)->dd_origin_obj;

                snap = kmem_alloc(sizeof (*snap), KM_SLEEP);
                snap->ds = ds;
                list_insert_tail(l, snap);
                obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
        }

        return (0);
}

static int
snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep)
{
        struct promotenode *snap;

        *spacep = 0;
        for (snap = list_head(l); snap; snap = list_next(l, snap)) {
                uint64_t used, comp, uncomp;
                dsl_deadlist_space_range(&snap->ds->ds_deadlist,
                    mintxg, UINT64_MAX, &used, &comp, &uncomp);
                *spacep += used;
        }
        return (0);
}

static void
snaplist_destroy(list_t *l, const void *tag)
{
        struct promotenode *snap;

        if (l == NULL || !list_link_active(&l->list_head))
                return;

        while ((snap = list_remove_tail(l)) != NULL) {
                dsl_dataset_rele(snap->ds, tag);
                kmem_free(snap, sizeof (*snap));
        }
        list_destroy(l);
}

static int
promote_hold(dsl_dataset_promote_arg_t *ddpa, dsl_pool_t *dp, const void *tag)
{
        int error;
        dsl_dir_t *dd;
        struct promotenode *snap;

        error = dsl_dataset_hold(dp, ddpa->ddpa_clonename, tag,
            &ddpa->ddpa_clone);
        if (error != 0)
                return (error);
        dd = ddpa->ddpa_clone->ds_dir;

        if (ddpa->ddpa_clone->ds_is_snapshot ||
            !dsl_dir_is_clone(dd)) {
                dsl_dataset_rele(ddpa->ddpa_clone, tag);
                return (SET_ERROR(EINVAL));
        }

        error = snaplist_make(dp, 0, dsl_dir_phys(dd)->dd_origin_obj,
            &ddpa->shared_snaps, tag);
        if (error != 0)
                goto out;

        error = snaplist_make(dp, 0, ddpa->ddpa_clone->ds_object,
            &ddpa->clone_snaps, tag);
        if (error != 0)
                goto out;

        snap = list_head(&ddpa->shared_snaps);
        ASSERT3U(snap->ds->ds_object, ==, dsl_dir_phys(dd)->dd_origin_obj);
        error = snaplist_make(dp, dsl_dir_phys(dd)->dd_origin_obj,
            dsl_dir_phys(snap->ds->ds_dir)->dd_head_dataset_obj,
            &ddpa->origin_snaps, tag);
        if (error != 0)
                goto out;

        if (dsl_dir_phys(snap->ds->ds_dir)->dd_origin_obj != 0) {
                error = dsl_dataset_hold_obj(dp,
                    dsl_dir_phys(snap->ds->ds_dir)->dd_origin_obj,
                    tag, &ddpa->origin_origin);
                if (error != 0)
                        goto out;
        }
out:
        if (error != 0)
                promote_rele(ddpa, tag);
        return (error);
}

static void
promote_rele(dsl_dataset_promote_arg_t *ddpa, const void *tag)
{
        snaplist_destroy(&ddpa->shared_snaps, tag);
        snaplist_destroy(&ddpa->clone_snaps, tag);
        snaplist_destroy(&ddpa->origin_snaps, tag);
        if (ddpa->origin_origin != NULL)
                dsl_dataset_rele(ddpa->origin_origin, tag);
        dsl_dataset_rele(ddpa->ddpa_clone, tag);
}

/*
 * Promote a clone.
 *
 * If it fails due to a conflicting snapshot name, "conflsnap" will be filled
 * in with the name.  (It must be at least ZFS_MAX_DATASET_NAME_LEN bytes long.)
 */
int
dsl_dataset_promote(const char *name, char *conflsnap)
{
        dsl_dataset_promote_arg_t ddpa = { 0 };
        uint64_t numsnaps;
        int error;
        nvpair_t *snap_pair;
        objset_t *os;

        /*
         * We will modify space proportional to the number of
         * snapshots.  Compute numsnaps.
         */
        error = dmu_objset_hold(name, FTAG, &os);
        if (error != 0)
                return (error);
        error = zap_count(dmu_objset_pool(os)->dp_meta_objset,
            dsl_dataset_phys(dmu_objset_ds(os))->ds_snapnames_zapobj,
            &numsnaps);
        dmu_objset_rele(os, FTAG);
        if (error != 0)
                return (error);

        ddpa.ddpa_clonename = name;
        ddpa.err_ds = fnvlist_alloc();
        ddpa.cr = CRED();
        ddpa.proc = curproc;

        error = dsl_sync_task(name, dsl_dataset_promote_check,
            dsl_dataset_promote_sync, &ddpa,
            2 + numsnaps, ZFS_SPACE_CHECK_RESERVED);

        /*
         * Return the first conflicting snapshot found.
         */
        snap_pair = nvlist_next_nvpair(ddpa.err_ds, NULL);
        if (snap_pair != NULL && conflsnap != NULL)
                (void) strlcpy(conflsnap, nvpair_name(snap_pair),
                    ZFS_MAX_DATASET_NAME_LEN);

        fnvlist_free(ddpa.err_ds);
        return (error);
}

int
dsl_dataset_clone_swap_check_impl(dsl_dataset_t *clone,
    dsl_dataset_t *origin_head, boolean_t force, void *owner, dmu_tx_t *tx)
{
        /*
         * "slack" factor for received datasets with refquota set on them.
         * See the bottom of this function for details on its use.
         */
        uint64_t refquota_slack = (uint64_t)DMU_MAX_ACCESS *
            spa_asize_inflation;
        int64_t unused_refres_delta;

        /* they should both be heads */
        if (clone->ds_is_snapshot ||
            origin_head->ds_is_snapshot)
                return (SET_ERROR(EINVAL));

        /* if we are not forcing, the branch point should be just before them */
        if (!force && clone->ds_prev != origin_head->ds_prev)
                return (SET_ERROR(EINVAL));

        /* clone should be the clone (unless they are unrelated) */
        if (clone->ds_prev != NULL &&
            clone->ds_prev != clone->ds_dir->dd_pool->dp_origin_snap &&
            origin_head->ds_dir != clone->ds_prev->ds_dir)
                return (SET_ERROR(EINVAL));

        /* the clone should be a child of the origin */
        if (clone->ds_dir->dd_parent != origin_head->ds_dir)
                return (SET_ERROR(EINVAL));

        /* origin_head shouldn't be modified unless 'force' */
        if (!force &&
            dsl_dataset_modified_since_snap(origin_head, origin_head->ds_prev))
                return (SET_ERROR(ETXTBSY));

        /* origin_head should have no long holds (e.g. is not mounted) */
        if (dsl_dataset_handoff_check(origin_head, owner, tx))
                return (SET_ERROR(EBUSY));

        /* check amount of any unconsumed refreservation */
        unused_refres_delta =
            (int64_t)MIN(origin_head->ds_reserved,
            dsl_dataset_phys(origin_head)->ds_unique_bytes) -
            (int64_t)MIN(origin_head->ds_reserved,
            dsl_dataset_phys(clone)->ds_unique_bytes);

        if (unused_refres_delta > 0 &&
            unused_refres_delta >
            dsl_dir_space_available(origin_head->ds_dir, NULL, 0, TRUE))
                return (SET_ERROR(ENOSPC));

        /*
         * The clone can't be too much over the head's refquota.
         *
         * To ensure that the entire refquota can be used, we allow one
         * transaction to exceed the refquota.  Therefore, this check
         * needs to also allow for the space referenced to be more than the
         * refquota.  The maximum amount of space that one transaction can use
         * on disk is DMU_MAX_ACCESS * spa_asize_inflation.  Allowing this
         * overage ensures that we are able to receive a filesystem that
         * exceeds the refquota on the source system.
         *
         * So that overage is the refquota_slack we use below.
         */
        if (origin_head->ds_quota != 0 &&
            dsl_dataset_phys(clone)->ds_referenced_bytes >
            origin_head->ds_quota + refquota_slack)
                return (SET_ERROR(EDQUOT));

        return (0);
}

static void
dsl_dataset_swap_remap_deadlists(dsl_dataset_t *clone,
    dsl_dataset_t *origin, dmu_tx_t *tx)
{
        uint64_t clone_remap_dl_obj, origin_remap_dl_obj;
        dsl_pool_t *dp = dmu_tx_pool(tx);

        ASSERT(dsl_pool_sync_context(dp));

        clone_remap_dl_obj = dsl_dataset_get_remap_deadlist_object(clone);
        origin_remap_dl_obj = dsl_dataset_get_remap_deadlist_object(origin);

        if (clone_remap_dl_obj != 0) {
                dsl_deadlist_close(&clone->ds_remap_deadlist);
                dsl_dataset_unset_remap_deadlist_object(clone, tx);
        }
        if (origin_remap_dl_obj != 0) {
                dsl_deadlist_close(&origin->ds_remap_deadlist);
                dsl_dataset_unset_remap_deadlist_object(origin, tx);
        }

        if (clone_remap_dl_obj != 0) {
                dsl_dataset_set_remap_deadlist_object(origin,
                    clone_remap_dl_obj, tx);
                VERIFY0(dsl_deadlist_open(&origin->ds_remap_deadlist,
                    dp->dp_meta_objset, clone_remap_dl_obj));
        }
        if (origin_remap_dl_obj != 0) {
                dsl_dataset_set_remap_deadlist_object(clone,
                    origin_remap_dl_obj, tx);
                VERIFY0(dsl_deadlist_open(&clone->ds_remap_deadlist,
                    dp->dp_meta_objset, origin_remap_dl_obj));
        }
}

void
dsl_dataset_clone_swap_sync_impl(dsl_dataset_t *clone,
    dsl_dataset_t *origin_head, dmu_tx_t *tx)
{
        dsl_pool_t *dp = dmu_tx_pool(tx);
        int64_t unused_refres_delta;

        ASSERT(clone->ds_reserved == 0);
        /*
         * NOTE: On DEBUG kernels there could be a race between this and
         * the check function if spa_asize_inflation is adjusted...
         */
        ASSERT(origin_head->ds_quota == 0 ||
            dsl_dataset_phys(clone)->ds_unique_bytes <= origin_head->ds_quota +
            DMU_MAX_ACCESS * spa_asize_inflation);
        ASSERT3P(clone->ds_prev, ==, origin_head->ds_prev);

        dsl_dir_cancel_waiters(origin_head->ds_dir);

        /*
         * Swap per-dataset feature flags.
         */
        for (spa_feature_t f = 0; f < SPA_FEATURES; f++) {
                if (!(spa_feature_table[f].fi_flags &
                    ZFEATURE_FLAG_PER_DATASET)) {
                        ASSERT(!dsl_dataset_feature_is_active(clone, f));
                        ASSERT(!dsl_dataset_feature_is_active(origin_head, f));
                        continue;
                }

                boolean_t clone_inuse = dsl_dataset_feature_is_active(clone, f);
                void *clone_feature = clone->ds_feature[f];
                boolean_t origin_head_inuse =
                    dsl_dataset_feature_is_active(origin_head, f);
                void *origin_head_feature = origin_head->ds_feature[f];

                if (clone_inuse)
                        dsl_dataset_deactivate_feature_impl(clone, f, tx);
                if (origin_head_inuse)
                        dsl_dataset_deactivate_feature_impl(origin_head, f, tx);

                if (clone_inuse) {
                        dsl_dataset_activate_feature(origin_head->ds_object, f,
                            clone_feature, tx);
                        origin_head->ds_feature[f] = clone_feature;
                }
                if (origin_head_inuse) {
                        dsl_dataset_activate_feature(clone->ds_object, f,
                            origin_head_feature, tx);
                        clone->ds_feature[f] = origin_head_feature;
                }
        }

        dmu_buf_will_dirty(clone->ds_dbuf, tx);
        dmu_buf_will_dirty(origin_head->ds_dbuf, tx);

        if (clone->ds_objset != NULL) {
                dmu_objset_evict(clone->ds_objset);
                clone->ds_objset = NULL;
        }

        if (origin_head->ds_objset != NULL) {
                dmu_objset_evict(origin_head->ds_objset);
                origin_head->ds_objset = NULL;
        }

        unused_refres_delta =
            (int64_t)MIN(origin_head->ds_reserved,
            dsl_dataset_phys(origin_head)->ds_unique_bytes) -
            (int64_t)MIN(origin_head->ds_reserved,
            dsl_dataset_phys(clone)->ds_unique_bytes);

        /*
         * Reset origin's unique bytes.
         */
        {
                dsl_dataset_t *origin = clone->ds_prev;
                uint64_t comp, uncomp;

                dmu_buf_will_dirty(origin->ds_dbuf, tx);
                dsl_deadlist_space_range(&clone->ds_deadlist,
                    dsl_dataset_phys(origin)->ds_prev_snap_txg, UINT64_MAX,
                    &dsl_dataset_phys(origin)->ds_unique_bytes, &comp, &uncomp);
        }

        /* swap blkptrs */
        {
                rrw_enter(&clone->ds_bp_rwlock, RW_WRITER, FTAG);
                rrw_enter(&origin_head->ds_bp_rwlock, RW_WRITER, FTAG);
                blkptr_t tmp;
                tmp = dsl_dataset_phys(origin_head)->ds_bp;
                dsl_dataset_phys(origin_head)->ds_bp =
                    dsl_dataset_phys(clone)->ds_bp;
                dsl_dataset_phys(clone)->ds_bp = tmp;
                rrw_exit(&origin_head->ds_bp_rwlock, FTAG);
                rrw_exit(&clone->ds_bp_rwlock, FTAG);
        }

        /* set dd_*_bytes */
        {
                int64_t dused, dcomp, duncomp;
                uint64_t cdl_used, cdl_comp, cdl_uncomp;
                uint64_t odl_used, odl_comp, odl_uncomp;

                ASSERT3U(dsl_dir_phys(clone->ds_dir)->
                    dd_used_breakdown[DD_USED_SNAP], ==, 0);

                dsl_deadlist_space(&clone->ds_deadlist,
                    &cdl_used, &cdl_comp, &cdl_uncomp);
                dsl_deadlist_space(&origin_head->ds_deadlist,
                    &odl_used, &odl_comp, &odl_uncomp);

                dused = dsl_dataset_phys(clone)->ds_referenced_bytes +
                    cdl_used -
                    (dsl_dataset_phys(origin_head)->ds_referenced_bytes +
                    odl_used);
                dcomp = dsl_dataset_phys(clone)->ds_compressed_bytes +
                    cdl_comp -
                    (dsl_dataset_phys(origin_head)->ds_compressed_bytes +
                    odl_comp);
                duncomp = dsl_dataset_phys(clone)->ds_uncompressed_bytes +
                    cdl_uncomp -
                    (dsl_dataset_phys(origin_head)->ds_uncompressed_bytes +
                    odl_uncomp);

                dsl_dir_diduse_space(origin_head->ds_dir, DD_USED_HEAD,
                    dused, dcomp, duncomp, tx);
                dsl_dir_diduse_space(clone->ds_dir, DD_USED_HEAD,
                    -dused, -dcomp, -duncomp, tx);

                /*
                 * The difference in the space used by snapshots is the
                 * difference in snapshot space due to the head's
                 * deadlist (since that's the only thing that's
                 * changing that affects the snapused).
                 */
                dsl_deadlist_space_range(&clone->ds_deadlist,
                    origin_head->ds_dir->dd_origin_txg, UINT64_MAX,
                    &cdl_used, &cdl_comp, &cdl_uncomp);
                dsl_deadlist_space_range(&origin_head->ds_deadlist,
                    origin_head->ds_dir->dd_origin_txg, UINT64_MAX,
                    &odl_used, &odl_comp, &odl_uncomp);
                dsl_dir_transfer_space(origin_head->ds_dir, cdl_used - odl_used,
                    DD_USED_HEAD, DD_USED_SNAP, tx);
        }

        /* swap ds_*_bytes */
        SWITCH64(dsl_dataset_phys(origin_head)->ds_referenced_bytes,
            dsl_dataset_phys(clone)->ds_referenced_bytes);
        SWITCH64(dsl_dataset_phys(origin_head)->ds_compressed_bytes,
            dsl_dataset_phys(clone)->ds_compressed_bytes);
        SWITCH64(dsl_dataset_phys(origin_head)->ds_uncompressed_bytes,
            dsl_dataset_phys(clone)->ds_uncompressed_bytes);
        SWITCH64(dsl_dataset_phys(origin_head)->ds_unique_bytes,
            dsl_dataset_phys(clone)->ds_unique_bytes);

        /* apply any parent delta for change in unconsumed refreservation */
        dsl_dir_diduse_space(origin_head->ds_dir, DD_USED_REFRSRV,
            unused_refres_delta, 0, 0, tx);

        /*
         * Swap deadlists.
         */
        dsl_deadlist_close(&clone->ds_deadlist);
        dsl_deadlist_close(&origin_head->ds_deadlist);
        SWITCH64(dsl_dataset_phys(origin_head)->ds_deadlist_obj,
            dsl_dataset_phys(clone)->ds_deadlist_obj);
        VERIFY0(dsl_deadlist_open(&clone->ds_deadlist, dp->dp_meta_objset,
            dsl_dataset_phys(clone)->ds_deadlist_obj));
        VERIFY0(dsl_deadlist_open(&origin_head->ds_deadlist, dp->dp_meta_objset,
            dsl_dataset_phys(origin_head)->ds_deadlist_obj));
        dsl_dataset_swap_remap_deadlists(clone, origin_head, tx);

        /*
         * If there is a bookmark at the origin, its "next dataset" is
         * changing, so we need to reset its FBN.
         */
        dsl_bookmark_next_changed(origin_head, origin_head->ds_prev, tx);

        dsl_scan_ds_clone_swapped(origin_head, clone, tx);

        /*
         * Destroy any livelists associated with the clone or the origin,
         * since after the swap the corresponding livelists are no longer
         * valid.
         */
        dsl_dir_remove_livelist(clone->ds_dir, tx, B_TRUE);
        dsl_dir_remove_livelist(origin_head->ds_dir, tx, B_TRUE);

        spa_history_log_internal_ds(clone, "clone swap", tx,
            "parent=%s", origin_head->ds_dir->dd_myname);
}

/*
 * Given a pool name and a dataset object number in that pool,
 * return the name of that dataset.
 */
int
dsl_dsobj_to_dsname(char *pname, uint64_t obj, char *buf)
{
        dsl_pool_t *dp;
        dsl_dataset_t *ds;
        int error;

        error = dsl_pool_hold(pname, FTAG, &dp);
        if (error != 0)
                return (error);

        error = dsl_dataset_hold_obj(dp, obj, FTAG, &ds);
        if (error == 0) {
                dsl_dataset_name(ds, buf);
                dsl_dataset_rele(ds, FTAG);
        }
        dsl_pool_rele(dp, FTAG);

        return (error);
}

int
dsl_dataset_check_quota(dsl_dataset_t *ds, boolean_t check_quota,
    uint64_t asize, uint64_t inflight, uint64_t *used, uint64_t *ref_rsrv)
{
        int error = 0;

        ASSERT3S(asize, >, 0);

        /*
         * *ref_rsrv is the portion of asize that will come from any
         * unconsumed refreservation space.
         */
        *ref_rsrv = 0;

        mutex_enter(&ds->ds_lock);
        /*
         * Make a space adjustment for reserved bytes.
         */
        if (ds->ds_reserved > dsl_dataset_phys(ds)->ds_unique_bytes) {
                ASSERT3U(*used, >=,
                    ds->ds_reserved - dsl_dataset_phys(ds)->ds_unique_bytes);
                *used -=
                    (ds->ds_reserved - dsl_dataset_phys(ds)->ds_unique_bytes);
                *ref_rsrv =
                    asize - MIN(asize, parent_delta(ds, asize + inflight));
        }

        if (!check_quota || ds->ds_quota == 0) {
                mutex_exit(&ds->ds_lock);
                return (0);
        }
        /*
         * If they are requesting more space, and our current estimate
         * is over quota, they get to try again unless the actual
         * on-disk is over quota and there are no pending changes (which
         * may free up space for us).
         */
        if (dsl_dataset_phys(ds)->ds_referenced_bytes + inflight >=
            ds->ds_quota) {
                if (inflight > 0 ||
                    dsl_dataset_phys(ds)->ds_referenced_bytes < ds->ds_quota)
                        error = SET_ERROR(ERESTART);
                else
                        error = SET_ERROR(EDQUOT);
        }
        mutex_exit(&ds->ds_lock);

        return (error);
}

typedef struct dsl_dataset_set_qr_arg {
        const char *ddsqra_name;
        zprop_source_t ddsqra_source;
        uint64_t ddsqra_value;
} dsl_dataset_set_qr_arg_t;


static int
dsl_dataset_set_refquota_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_set_qr_arg_t *ddsqra = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds;
        int error;
        uint64_t newval;

        if (spa_version(dp->dp_spa) < SPA_VERSION_REFQUOTA)
                return (SET_ERROR(ENOTSUP));

        error = dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds);
        if (error != 0)
                return (error);

        if (ds->ds_is_snapshot) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(EINVAL));
        }

        error = dsl_prop_predict(ds->ds_dir,
            zfs_prop_to_name(ZFS_PROP_REFQUOTA),
            ddsqra->ddsqra_source, ddsqra->ddsqra_value, &newval);
        if (error != 0) {
                dsl_dataset_rele(ds, FTAG);
                return (error);
        }

        if (newval == 0) {
                dsl_dataset_rele(ds, FTAG);
                return (0);
        }

        if (newval < dsl_dataset_phys(ds)->ds_referenced_bytes ||
            newval < ds->ds_reserved) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(ENOSPC));
        }

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

static void
dsl_dataset_set_refquota_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_set_qr_arg_t *ddsqra = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds = NULL;
        uint64_t newval;

        VERIFY0(dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds));

        dsl_prop_set_sync_impl(ds,
            zfs_prop_to_name(ZFS_PROP_REFQUOTA),
            ddsqra->ddsqra_source, sizeof (ddsqra->ddsqra_value), 1,
            &ddsqra->ddsqra_value, tx);

        VERIFY0(dsl_prop_get_int_ds(ds,
            zfs_prop_to_name(ZFS_PROP_REFQUOTA), &newval));

        if (ds->ds_quota != newval) {
                dmu_buf_will_dirty(ds->ds_dbuf, tx);
                ds->ds_quota = newval;
        }
        dsl_dataset_rele(ds, FTAG);
}

int
dsl_dataset_set_refquota(const char *dsname, zprop_source_t source,
    uint64_t refquota)
{
        dsl_dataset_set_qr_arg_t ddsqra;

        ddsqra.ddsqra_name = dsname;
        ddsqra.ddsqra_source = source;
        ddsqra.ddsqra_value = refquota;

        return (dsl_sync_task(dsname, dsl_dataset_set_refquota_check,
            dsl_dataset_set_refquota_sync, &ddsqra, 0,
            ZFS_SPACE_CHECK_EXTRA_RESERVED));
}

static int
dsl_dataset_set_refreservation_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_set_qr_arg_t *ddsqra = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds;
        int error;
        uint64_t newval, unique;

        if (spa_version(dp->dp_spa) < SPA_VERSION_REFRESERVATION)
                return (SET_ERROR(ENOTSUP));

        error = dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds);
        if (error != 0)
                return (error);

        if (ds->ds_is_snapshot) {
                dsl_dataset_rele(ds, FTAG);
                return (SET_ERROR(EINVAL));
        }

        error = dsl_prop_predict(ds->ds_dir,
            zfs_prop_to_name(ZFS_PROP_REFRESERVATION),
            ddsqra->ddsqra_source, ddsqra->ddsqra_value, &newval);
        if (error != 0) {
                dsl_dataset_rele(ds, FTAG);
                return (error);
        }

        /*
         * If we are doing the preliminary check in open context, the
         * space estimates may be inaccurate.
         */
        if (!dmu_tx_is_syncing(tx)) {
                dsl_dataset_rele(ds, FTAG);
                return (0);
        }

        mutex_enter(&ds->ds_lock);
        if (!DS_UNIQUE_IS_ACCURATE(ds))
                dsl_dataset_recalc_head_uniq(ds);
        unique = dsl_dataset_phys(ds)->ds_unique_bytes;
        mutex_exit(&ds->ds_lock);

        if (MAX(unique, newval) > MAX(unique, ds->ds_reserved)) {
                uint64_t delta = MAX(unique, newval) -
                    MAX(unique, ds->ds_reserved);

                if (delta >
                    dsl_dir_space_available(ds->ds_dir, NULL, 0, B_TRUE) ||
                    (ds->ds_quota > 0 && newval > ds->ds_quota)) {
                        dsl_dataset_rele(ds, FTAG);
                        return (SET_ERROR(ENOSPC));
                }
        }

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

void
dsl_dataset_set_refreservation_sync_impl(dsl_dataset_t *ds,
    zprop_source_t source, uint64_t value, dmu_tx_t *tx)
{
        uint64_t newval;
        uint64_t unique;
        int64_t delta;

        dsl_prop_set_sync_impl(ds, zfs_prop_to_name(ZFS_PROP_REFRESERVATION),
            source, sizeof (value), 1, &value, tx);

        VERIFY0(dsl_prop_get_int_ds(ds,
            zfs_prop_to_name(ZFS_PROP_REFRESERVATION), &newval));

        dmu_buf_will_dirty(ds->ds_dbuf, tx);
        mutex_enter(&ds->ds_dir->dd_lock);
        mutex_enter(&ds->ds_lock);
        ASSERT(DS_UNIQUE_IS_ACCURATE(ds));
        unique = dsl_dataset_phys(ds)->ds_unique_bytes;
        delta = MAX(0, (int64_t)(newval - unique)) -
            MAX(0, (int64_t)(ds->ds_reserved - unique));
        ds->ds_reserved = newval;
        mutex_exit(&ds->ds_lock);

        dsl_dir_diduse_space(ds->ds_dir, DD_USED_REFRSRV, delta, 0, 0, tx);
        mutex_exit(&ds->ds_dir->dd_lock);
}

static void
dsl_dataset_set_refreservation_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_set_qr_arg_t *ddsqra = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds = NULL;

        VERIFY0(dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds));
        dsl_dataset_set_refreservation_sync_impl(ds,
            ddsqra->ddsqra_source, ddsqra->ddsqra_value, tx);
        dsl_dataset_rele(ds, FTAG);
}

int
dsl_dataset_set_refreservation(const char *dsname, zprop_source_t source,
    uint64_t refreservation)
{
        dsl_dataset_set_qr_arg_t ddsqra;

        ddsqra.ddsqra_name = dsname;
        ddsqra.ddsqra_source = source;
        ddsqra.ddsqra_value = refreservation;

        return (dsl_sync_task(dsname, dsl_dataset_set_refreservation_check,
            dsl_dataset_set_refreservation_sync, &ddsqra, 0,
            ZFS_SPACE_CHECK_EXTRA_RESERVED));
}

typedef struct dsl_dataset_set_compression_arg {
        const char *ddsca_name;
        zprop_source_t ddsca_source;
        uint64_t ddsca_value;
} dsl_dataset_set_compression_arg_t;

static int
dsl_dataset_set_compression_check(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_set_compression_arg_t *ddsca = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);

        uint64_t compval = ZIO_COMPRESS_ALGO(ddsca->ddsca_value);
        spa_feature_t f = zio_compress_to_feature(compval);

        if (f == SPA_FEATURE_NONE)
                return (SET_ERROR(EINVAL));

        if (!spa_feature_is_enabled(dp->dp_spa, f))
                return (SET_ERROR(ENOTSUP));

        return (0);
}

static void
dsl_dataset_set_compression_sync(void *arg, dmu_tx_t *tx)
{
        dsl_dataset_set_compression_arg_t *ddsca = arg;
        dsl_pool_t *dp = dmu_tx_pool(tx);
        dsl_dataset_t *ds = NULL;

        uint64_t compval = ZIO_COMPRESS_ALGO(ddsca->ddsca_value);
        spa_feature_t f = zio_compress_to_feature(compval);
        ASSERT3S(f, !=, SPA_FEATURE_NONE);
        ASSERT3S(spa_feature_table[f].fi_type, ==, ZFEATURE_TYPE_BOOLEAN);

        VERIFY0(dsl_dataset_hold(dp, ddsca->ddsca_name, FTAG, &ds));
        if (zfeature_active(f, ds->ds_feature[f]) != B_TRUE) {
                ds->ds_feature_activation[f] = (void *)B_TRUE;
                dsl_dataset_activate_feature(ds->ds_object, f,
                    ds->ds_feature_activation[f], tx);
                ds->ds_feature[f] = ds->ds_feature_activation[f];
        }
        dsl_dataset_rele(ds, FTAG);
}

int
dsl_dataset_set_compression(const char *dsname, zprop_source_t source,
    uint64_t compression)
{
        dsl_dataset_set_compression_arg_t ddsca;

        /*
         * The sync task is only required for zstd in order to activate
         * the feature flag when the property is first set.
         */
        if (ZIO_COMPRESS_ALGO(compression) != ZIO_COMPRESS_ZSTD)
                return (0);

        ddsca.ddsca_name = dsname;
        ddsca.ddsca_source = source;
        ddsca.ddsca_value = compression;

        return (dsl_sync_task(dsname, dsl_dataset_set_compression_check,
            dsl_dataset_set_compression_sync, &ddsca, 0,
            ZFS_SPACE_CHECK_EXTRA_RESERVED));
}

/*
 * Return (in *usedp) the amount of space referenced by "new" that was not
 * referenced at the time the bookmark corresponds to.  "New" may be a
 * snapshot or a head.  The bookmark must be before new, in
 * new's filesystem (or its origin) -- caller verifies this.
 *
 * The written space is calculated by considering two components:  First, we
 * ignore any freed space, and calculate the written as new's used space
 * minus old's used space.  Next, we add in the amount of space that was freed
 * between the two time points, thus reducing new's used space relative to
 * old's. Specifically, this is the space that was born before
 * zbm_creation_txg, and freed before new (ie. on new's deadlist or a
 * previous deadlist).
 *
 * space freed                         [---------------------]
 * snapshots                       ---O-------O--------O-------O------
 *                                         bookmark           new
 *
 * Note, the bookmark's zbm_*_bytes_refd must be valid, but if the HAS_FBN
 * flag is not set, we will calculate the freed_before_next based on the
 * next snapshot's deadlist, rather than using zbm_*_freed_before_next_snap.
 */
static int
dsl_dataset_space_written_impl(zfs_bookmark_phys_t *bmp,
    dsl_dataset_t *new, uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
{
        int err = 0;
        dsl_pool_t *dp = new->ds_dir->dd_pool;

        ASSERT(dsl_pool_config_held(dp));
        if (dsl_dataset_is_snapshot(new)) {
                ASSERT3U(bmp->zbm_creation_txg, <,
                    dsl_dataset_phys(new)->ds_creation_txg);
        }

        *usedp = 0;
        *usedp += dsl_dataset_phys(new)->ds_referenced_bytes;
        *usedp -= bmp->zbm_referenced_bytes_refd;

        *compp = 0;
        *compp += dsl_dataset_phys(new)->ds_compressed_bytes;
        *compp -= bmp->zbm_compressed_bytes_refd;

        *uncompp = 0;
        *uncompp += dsl_dataset_phys(new)->ds_uncompressed_bytes;
        *uncompp -= bmp->zbm_uncompressed_bytes_refd;

        dsl_dataset_t *snap = new;

        while (dsl_dataset_phys(snap)->ds_prev_snap_txg >
            bmp->zbm_creation_txg) {
                uint64_t used, comp, uncomp;

                dsl_deadlist_space_range(&snap->ds_deadlist,
                    0, bmp->zbm_creation_txg,
                    &used, &comp, &uncomp);
                *usedp += used;
                *compp += comp;
                *uncompp += uncomp;

                uint64_t snapobj = dsl_dataset_phys(snap)->ds_prev_snap_obj;
                if (snap != new)
                        dsl_dataset_rele(snap, FTAG);
                err = dsl_dataset_hold_obj(dp, snapobj, FTAG, &snap);
                if (err != 0)
                        break;
        }

        /*
         * We might not have the FBN if we are calculating written from
         * a snapshot (because we didn't know the correct "next" snapshot
         * until now).
         */
        if (bmp->zbm_flags & ZBM_FLAG_HAS_FBN) {
                *usedp += bmp->zbm_referenced_freed_before_next_snap;
                *compp += bmp->zbm_compressed_freed_before_next_snap;
                *uncompp += bmp->zbm_uncompressed_freed_before_next_snap;
        } else {
                ASSERT3U(dsl_dataset_phys(snap)->ds_prev_snap_txg, ==,
                    bmp->zbm_creation_txg);
                uint64_t used, comp, uncomp;
                dsl_deadlist_space(&snap->ds_deadlist, &used, &comp, &uncomp);
                *usedp += used;
                *compp += comp;
                *uncompp += uncomp;
        }
        if (snap != new)
                dsl_dataset_rele(snap, FTAG);
        return (err);
}

/*
 * Return (in *usedp) the amount of space written in new that was not
 * present at the time the bookmark corresponds to.  New may be a
 * snapshot or the head.  Old must be a bookmark before new, in
 * new's filesystem (or its origin) -- caller verifies this.
 */
int
dsl_dataset_space_written_bookmark(zfs_bookmark_phys_t *bmp,
    dsl_dataset_t *new, uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
{
        if (!(bmp->zbm_flags & ZBM_FLAG_HAS_FBN))
                return (SET_ERROR(ENOTSUP));
        return (dsl_dataset_space_written_impl(bmp, new,
            usedp, compp, uncompp));
}

/*
 * Return (in *usedp) the amount of space written in new that is not
 * present in oldsnap.  New may be a snapshot or the head.  Old must be
 * a snapshot before new, in new's filesystem (or its origin).  If not then
 * fail and return EINVAL.
 */
int
dsl_dataset_space_written(dsl_dataset_t *oldsnap, dsl_dataset_t *new,
    uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
{
        if (!dsl_dataset_is_before(new, oldsnap, 0))
                return (SET_ERROR(EINVAL));

        zfs_bookmark_phys_t zbm = { 0 };
        dsl_dataset_phys_t *dsp = dsl_dataset_phys(oldsnap);
        zbm.zbm_guid = dsp->ds_guid;
        zbm.zbm_creation_txg = dsp->ds_creation_txg;
        zbm.zbm_creation_time = dsp->ds_creation_time;
        zbm.zbm_referenced_bytes_refd = dsp->ds_referenced_bytes;
        zbm.zbm_compressed_bytes_refd = dsp->ds_compressed_bytes;
        zbm.zbm_uncompressed_bytes_refd = dsp->ds_uncompressed_bytes;

        /*
         * If oldsnap is the origin (or origin's origin, ...) of new,
         * we can't easily calculate the effective FBN.  Therefore,
         * we do not set ZBM_FLAG_HAS_FBN, so that the _impl will calculate
         * it relative to the correct "next": the next snapshot towards "new",
         * rather than the next snapshot in oldsnap's dsl_dir.
         */
        return (dsl_dataset_space_written_impl(&zbm, new,
            usedp, compp, uncompp));
}

/*
 * Return (in *usedp) the amount of space that will be reclaimed if firstsnap,
 * lastsnap, and all snapshots in between are deleted.
 *
 * blocks that would be freed            [---------------------------]
 * snapshots                       ---O-------O--------O-------O--------O
 *                                        firstsnap        lastsnap
 *
 * This is the set of blocks that were born after the snap before firstsnap,
 * (birth > firstsnap->prev_snap_txg) and died before the snap after the
 * last snap (ie, is on lastsnap->ds_next->ds_deadlist or an earlier deadlist).
 * We calculate this by iterating over the relevant deadlists (from the snap
 * after lastsnap, backward to the snap after firstsnap), summing up the
 * space on the deadlist that was born after the snap before firstsnap.
 */
int
dsl_dataset_space_wouldfree(dsl_dataset_t *firstsnap,
    dsl_dataset_t *lastsnap,
    uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
{
        int err = 0;
        uint64_t snapobj;
        dsl_pool_t *dp = firstsnap->ds_dir->dd_pool;

        ASSERT(firstsnap->ds_is_snapshot);
        ASSERT(lastsnap->ds_is_snapshot);

        /*
         * Check that the snapshots are in the same dsl_dir, and firstsnap
         * is before lastsnap.
         */
        if (firstsnap->ds_dir != lastsnap->ds_dir ||
            dsl_dataset_phys(firstsnap)->ds_creation_txg >
            dsl_dataset_phys(lastsnap)->ds_creation_txg)
                return (SET_ERROR(EINVAL));

        *usedp = *compp = *uncompp = 0;

        snapobj = dsl_dataset_phys(lastsnap)->ds_next_snap_obj;
        while (snapobj != firstsnap->ds_object) {
                dsl_dataset_t *ds;
                uint64_t used, comp, uncomp;

                err = dsl_dataset_hold_obj(dp, snapobj, FTAG, &ds);
                if (err != 0)
                        break;

                dsl_deadlist_space_range(&ds->ds_deadlist,
                    dsl_dataset_phys(firstsnap)->ds_prev_snap_txg, UINT64_MAX,
                    &used, &comp, &uncomp);
                *usedp += used;
                *compp += comp;
                *uncompp += uncomp;

                snapobj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
                ASSERT3U(snapobj, !=, 0);
                dsl_dataset_rele(ds, FTAG);
        }
        return (err);
}

/*
 * Return TRUE if 'earlier' is an earlier snapshot in 'later's timeline.
 * For example, they could both be snapshots of the same filesystem, and
 * 'earlier' is before 'later'.  Or 'earlier' could be the origin of
 * 'later's filesystem.  Or 'earlier' could be an older snapshot in the origin's
 * filesystem.  Or 'earlier' could be the origin's origin.
 *
 * If non-zero, earlier_txg is used instead of earlier's ds_creation_txg.
 */
boolean_t
dsl_dataset_is_before(dsl_dataset_t *later, dsl_dataset_t *earlier,
    uint64_t earlier_txg)
{
        dsl_pool_t *dp = later->ds_dir->dd_pool;
        int error;
        boolean_t ret;

        ASSERT(dsl_pool_config_held(dp));
        ASSERT(earlier->ds_is_snapshot || earlier_txg != 0);

        if (earlier_txg == 0)
                earlier_txg = dsl_dataset_phys(earlier)->ds_creation_txg;

        if (later->ds_is_snapshot &&
            earlier_txg >= dsl_dataset_phys(later)->ds_creation_txg)
                return (B_FALSE);

        if (later->ds_dir == earlier->ds_dir)
                return (B_TRUE);

        /*
         * We check dd_origin_obj explicitly here rather than using
         * dsl_dir_is_clone() so that we will return TRUE if "earlier"
         * is $ORIGIN@$ORIGIN.  dsl_dataset_space_written() depends on
         * this behavior.
         */
        if (dsl_dir_phys(later->ds_dir)->dd_origin_obj == 0)
                return (B_FALSE);

        dsl_dataset_t *origin;
        error = dsl_dataset_hold_obj(dp,
            dsl_dir_phys(later->ds_dir)->dd_origin_obj, FTAG, &origin);
        if (error != 0)
                return (B_FALSE);
        if (dsl_dataset_phys(origin)->ds_creation_txg == earlier_txg &&
            origin->ds_dir == earlier->ds_dir) {
                dsl_dataset_rele(origin, FTAG);
                return (B_TRUE);
        }
        ret = dsl_dataset_is_before(origin, earlier, earlier_txg);
        dsl_dataset_rele(origin, FTAG);
        return (ret);
}

void
dsl_dataset_zapify(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
        dmu_object_zapify(mos, ds->ds_object, DMU_OT_DSL_DATASET, tx);
}

boolean_t
dsl_dataset_is_zapified(dsl_dataset_t *ds)
{
        dmu_object_info_t doi;

        dmu_object_info_from_db(ds->ds_dbuf, &doi);
        return (doi.doi_type == DMU_OTN_ZAP_METADATA);
}

boolean_t
dsl_dataset_has_resume_receive_state(dsl_dataset_t *ds)
{
        return (dsl_dataset_is_zapified(ds) &&
            zap_contains(ds->ds_dir->dd_pool->dp_meta_objset,
            ds->ds_object, DS_FIELD_RESUME_TOGUID) == 0);
}

uint64_t
dsl_dataset_get_remap_deadlist_object(dsl_dataset_t *ds)
{
        uint64_t remap_deadlist_obj;
        int err;

        if (!dsl_dataset_is_zapified(ds))
                return (0);

        err = zap_lookup(ds->ds_dir->dd_pool->dp_meta_objset, ds->ds_object,
            DS_FIELD_REMAP_DEADLIST, sizeof (remap_deadlist_obj), 1,
            &remap_deadlist_obj);

        if (err != 0) {
                VERIFY3S(err, ==, ENOENT);
                return (0);
        }

        ASSERT(remap_deadlist_obj != 0);
        return (remap_deadlist_obj);
}

boolean_t
dsl_dataset_remap_deadlist_exists(dsl_dataset_t *ds)
{
        EQUIV(dsl_deadlist_is_open(&ds->ds_remap_deadlist),
            dsl_dataset_get_remap_deadlist_object(ds) != 0);
        return (dsl_deadlist_is_open(&ds->ds_remap_deadlist));
}

static void
dsl_dataset_set_remap_deadlist_object(dsl_dataset_t *ds, uint64_t obj,
    dmu_tx_t *tx)
{
        ASSERT(obj != 0);
        dsl_dataset_zapify(ds, tx);
        VERIFY0(zap_add(ds->ds_dir->dd_pool->dp_meta_objset, ds->ds_object,
            DS_FIELD_REMAP_DEADLIST, sizeof (obj), 1, &obj, tx));
}

static void
dsl_dataset_unset_remap_deadlist_object(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        VERIFY0(zap_remove(ds->ds_dir->dd_pool->dp_meta_objset,
            ds->ds_object, DS_FIELD_REMAP_DEADLIST, tx));
}

void
dsl_dataset_destroy_remap_deadlist(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        uint64_t remap_deadlist_object;
        spa_t *spa = ds->ds_dir->dd_pool->dp_spa;

        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(dsl_dataset_remap_deadlist_exists(ds));

        remap_deadlist_object = ds->ds_remap_deadlist.dl_object;
        dsl_deadlist_close(&ds->ds_remap_deadlist);
        dsl_deadlist_free(spa_meta_objset(spa), remap_deadlist_object, tx);
        dsl_dataset_unset_remap_deadlist_object(ds, tx);
        spa_feature_decr(spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
}

void
dsl_dataset_create_remap_deadlist(dsl_dataset_t *ds, dmu_tx_t *tx)
{
        uint64_t remap_deadlist_obj;
        spa_t *spa = ds->ds_dir->dd_pool->dp_spa;

        ASSERT(dmu_tx_is_syncing(tx));
        ASSERT(MUTEX_HELD(&ds->ds_remap_deadlist_lock));
        /*
         * Currently we only create remap deadlists when there are indirect
         * vdevs with referenced mappings.
         */
        ASSERT(spa_feature_is_active(spa, SPA_FEATURE_DEVICE_REMOVAL));

        remap_deadlist_obj = dsl_deadlist_clone(
            &ds->ds_deadlist, UINT64_MAX,
            dsl_dataset_phys(ds)->ds_prev_snap_obj, tx);
        dsl_dataset_set_remap_deadlist_object(ds,
            remap_deadlist_obj, tx);
        VERIFY0(dsl_deadlist_open(&ds->ds_remap_deadlist, spa_meta_objset(spa),
            remap_deadlist_obj));
        spa_feature_incr(spa, SPA_FEATURE_OBSOLETE_COUNTS, tx);
}

void
dsl_dataset_activate_redaction(dsl_dataset_t *ds, uint64_t *redact_snaps,
    uint64_t num_redact_snaps, dmu_tx_t *tx)
{
        uint64_t dsobj = ds->ds_object;
        struct feature_type_uint64_array_arg *ftuaa =
            kmem_zalloc(sizeof (*ftuaa), KM_SLEEP);
        ftuaa->length = (int64_t)num_redact_snaps;
        if (num_redact_snaps > 0) {
                ftuaa->array = kmem_alloc(num_redact_snaps * sizeof (uint64_t),
                    KM_SLEEP);
                memcpy(ftuaa->array, redact_snaps, num_redact_snaps *
                    sizeof (uint64_t));
        }
        dsl_dataset_activate_feature(dsobj, SPA_FEATURE_REDACTED_DATASETS,
            ftuaa, tx);
        ds->ds_feature[SPA_FEATURE_REDACTED_DATASETS] = ftuaa;
}

/*
 * Find and return (in *oldest_dsobj) the oldest snapshot of the dsobj
 * dataset whose birth time is >= min_txg.
 */
int
dsl_dataset_oldest_snapshot(spa_t *spa, uint64_t head_ds, uint64_t min_txg,
    uint64_t *oldest_dsobj)
{
        dsl_dataset_t *ds;
        dsl_pool_t *dp = spa->spa_dsl_pool;

        int error = dsl_dataset_hold_obj(dp, head_ds, FTAG, &ds);
        if (error != 0)
                return (error);

        uint64_t prev_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
        uint64_t prev_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;

        while (prev_obj != 0 && min_txg < prev_obj_txg) {
                dsl_dataset_rele(ds, FTAG);
                if ((error = dsl_dataset_hold_obj(dp, prev_obj,
                    FTAG, &ds)) != 0)
                        return (error);
                prev_obj_txg = dsl_dataset_phys(ds)->ds_prev_snap_txg;
                prev_obj = dsl_dataset_phys(ds)->ds_prev_snap_obj;
        }
        *oldest_dsobj = ds->ds_object;
        dsl_dataset_rele(ds, FTAG);
        return (0);
}

ZFS_MODULE_PARAM(zfs, zfs_, max_recordsize, UINT, ZMOD_RW,
        "Max allowed record size");

ZFS_MODULE_PARAM(zfs, zfs_, allow_redacted_dataset_mount, INT, ZMOD_RW,
        "Allow mounting of redacted datasets");

ZFS_MODULE_PARAM(zfs, zfs_, snapshot_history_enabled, INT, ZMOD_RW,
        "Include snapshot events in pool history/events");

EXPORT_SYMBOL(dsl_dataset_hold);
EXPORT_SYMBOL(dsl_dataset_hold_flags);
EXPORT_SYMBOL(dsl_dataset_hold_obj);
EXPORT_SYMBOL(dsl_dataset_hold_obj_flags);
EXPORT_SYMBOL(dsl_dataset_own);
EXPORT_SYMBOL(dsl_dataset_own_obj);
EXPORT_SYMBOL(dsl_dataset_name);
EXPORT_SYMBOL(dsl_dataset_rele);
EXPORT_SYMBOL(dsl_dataset_rele_flags);
EXPORT_SYMBOL(dsl_dataset_disown);
EXPORT_SYMBOL(dsl_dataset_tryown);
EXPORT_SYMBOL(dsl_dataset_create_sync);
EXPORT_SYMBOL(dsl_dataset_create_sync_dd);
EXPORT_SYMBOL(dsl_dataset_snapshot_check);
EXPORT_SYMBOL(dsl_dataset_snapshot_sync);
EXPORT_SYMBOL(dsl_dataset_promote);
EXPORT_SYMBOL(dsl_dataset_user_hold);
EXPORT_SYMBOL(dsl_dataset_user_release);
EXPORT_SYMBOL(dsl_dataset_get_holds);
EXPORT_SYMBOL(dsl_dataset_get_blkptr);
EXPORT_SYMBOL(dsl_dataset_get_spa);
EXPORT_SYMBOL(dsl_dataset_modified_since_snap);
EXPORT_SYMBOL(dsl_dataset_space_written);
EXPORT_SYMBOL(dsl_dataset_space_wouldfree);
EXPORT_SYMBOL(dsl_dataset_sync);
EXPORT_SYMBOL(dsl_dataset_block_born);
EXPORT_SYMBOL(dsl_dataset_block_kill);
EXPORT_SYMBOL(dsl_dataset_dirty);
EXPORT_SYMBOL(dsl_dataset_stats);
EXPORT_SYMBOL(dsl_dataset_fast_stat);
EXPORT_SYMBOL(dsl_dataset_space);
EXPORT_SYMBOL(dsl_dataset_fsid_guid);
EXPORT_SYMBOL(dsl_dsobj_to_dsname);
EXPORT_SYMBOL(dsl_dataset_check_quota);
EXPORT_SYMBOL(dsl_dataset_clone_swap_check_impl);
EXPORT_SYMBOL(dsl_dataset_clone_swap_sync_impl);