Illumos #3006
[zfs.git] / module / zfs / dsl_dataset.c
index 0fe7eb5..c1a029b 100644 (file)
@@ -19,8 +19,9 @@
  * CDDL HEADER END
  */
 /*
- * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
- * Use is subject to license terms.
+ * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2012, Joyent, Inc. All rights reserved.
  */
 
 #include <sys/dmu_objset.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/zfs_znode.h>
-#include <sys/sunddi.h>
+#include <sys/zfs_onexit.h>
+#include <sys/zvol.h>
+#include <sys/dsl_scan.h>
+#include <sys/dsl_deadlist.h>
 
 static char *dsl_reaper = "the grim reaper";
 
 static dsl_checkfunc_t dsl_dataset_destroy_begin_check;
 static dsl_syncfunc_t dsl_dataset_destroy_begin_sync;
-static dsl_checkfunc_t dsl_dataset_rollback_check;
-static dsl_syncfunc_t dsl_dataset_rollback_sync;
 static dsl_syncfunc_t dsl_dataset_set_reservation_sync;
 
+#define        SWITCH64(x, y) \
+       { \
+               uint64_t __tmp = (x); \
+               (x) = (y); \
+               (y) = __tmp; \
+       }
+
 #define        DS_REF_MAX      (1ULL << 62)
 
 #define        DSL_DEADLIST_BLOCKSIZE  SPA_MAXBLOCKSIZE
@@ -76,37 +87,34 @@ parent_delta(dsl_dataset_t *ds, int64_t delta)
 }
 
 void
-dsl_dataset_block_born(dsl_dataset_t *ds, blkptr_t *bp, dmu_tx_t *tx)
+dsl_dataset_block_born(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx)
 {
-       int used = bp_get_dasize(tx->tx_pool->dp_spa, bp);
-       int compressed = BP_GET_PSIZE(bp);
-       int uncompressed = BP_GET_UCSIZE(bp);
+       int used, compressed, uncompressed;
        int64_t delta;
 
-       dprintf_bp(bp, "born, ds=%p\n", ds);
+       used = bp_get_dsize_sync(tx->tx_pool->dp_spa, bp);
+       compressed = BP_GET_PSIZE(bp);
+       uncompressed = BP_GET_UCSIZE(bp);
+
+       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))
                return;
        ASSERT(BP_GET_TYPE(bp) != DMU_OT_NONE);
-       ASSERT3U(BP_GET_TYPE(bp), <, DMU_OT_NUMTYPES);
+       ASSERT(DMU_OT_IS_VALID(BP_GET_TYPE(bp)));
        if (ds == NULL) {
-               /*
-                * Account for the meta-objset space in its placeholder
-                * dsl_dir.
-                */
-               ASSERT3U(compressed, ==, uncompressed); /* it's all metadata */
-               dsl_dir_diduse_space(tx->tx_pool->dp_mos_dir, DD_USED_HEAD,
-                   used, compressed, uncompressed, tx);
-               dsl_dir_dirty(tx->tx_pool->dp_mos_dir, tx);
+               dsl_pool_mos_diduse_space(tx->tx_pool,
+                   used, compressed, uncompressed);
                return;
        }
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
+
        mutex_enter(&ds->ds_dir->dd_lock);
        mutex_enter(&ds->ds_lock);
        delta = parent_delta(ds, used);
-       ds->ds_phys->ds_used_bytes += used;
+       ds->ds_phys->ds_referenced_bytes += used;
        ds->ds_phys->ds_compressed_bytes += compressed;
        ds->ds_phys->ds_uncompressed_bytes += uncompressed;
        ds->ds_phys->ds_unique_bytes += used;
@@ -119,33 +127,26 @@ dsl_dataset_block_born(dsl_dataset_t *ds, blkptr_t *bp, dmu_tx_t *tx)
 }
 
 int
-dsl_dataset_block_kill(dsl_dataset_t *ds, blkptr_t *bp, zio_t *pio,
-    dmu_tx_t *tx)
+dsl_dataset_block_kill(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx,
+    boolean_t async)
 {
-       int used = bp_get_dasize(tx->tx_pool->dp_spa, bp);
-       int compressed = BP_GET_PSIZE(bp);
-       int uncompressed = BP_GET_UCSIZE(bp);
+       int used, compressed, uncompressed;
 
-       ASSERT(pio != NULL);
-       ASSERT(dmu_tx_is_syncing(tx));
-       /* No block pointer => nothing to free */
        if (BP_IS_HOLE(bp))
                return (0);
 
+       ASSERT(dmu_tx_is_syncing(tx));
+       ASSERT(bp->blk_birth <= tx->tx_txg);
+
+       used = bp_get_dsize_sync(tx->tx_pool->dp_spa, bp);
+       compressed = BP_GET_PSIZE(bp);
+       uncompressed = BP_GET_UCSIZE(bp);
+
        ASSERT(used > 0);
        if (ds == NULL) {
-               int err;
-               /*
-                * Account for the meta-objset space in its placeholder
-                * dataset.
-                */
-               err = dsl_free(pio, tx->tx_pool,
-                   tx->tx_txg, bp, NULL, NULL, ARC_NOWAIT);
-               ASSERT(err == 0);
-
-               dsl_dir_diduse_space(tx->tx_pool->dp_mos_dir, DD_USED_HEAD,
-                   -used, -compressed, -uncompressed, tx);
-               dsl_dir_dirty(tx->tx_pool->dp_mos_dir, tx);
+               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);
@@ -154,13 +155,10 @@ dsl_dataset_block_kill(dsl_dataset_t *ds, blkptr_t *bp, zio_t *pio,
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
 
        if (bp->blk_birth > ds->ds_phys->ds_prev_snap_txg) {
-               int err;
                int64_t delta;
 
-               dprintf_bp(bp, "freeing: %s", "");
-               err = dsl_free(pio, tx->tx_pool,
-                   tx->tx_txg, bp, NULL, NULL, ARC_NOWAIT);
-               ASSERT(err == 0);
+               dprintf_bp(bp, "freeing ds=%llu", ds->ds_object);
+               dsl_free(tx->tx_pool, tx->tx_txg, bp);
 
                mutex_enter(&ds->ds_dir->dd_lock);
                mutex_enter(&ds->ds_lock);
@@ -176,7 +174,18 @@ dsl_dataset_block_kill(dsl_dataset_t *ds, blkptr_t *bp, zio_t *pio,
                mutex_exit(&ds->ds_dir->dd_lock);
        } else {
                dprintf_bp(bp, "putting on dead list: %s", "");
-               VERIFY(0 == bplist_enqueue(&ds->ds_deadlist, bp, tx));
+               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, tx);
+               }
                ASSERT3U(ds->ds_prev->ds_object, ==,
                    ds->ds_phys->ds_prev_snap_obj);
                ASSERT(ds->ds_prev->ds_phys->ds_num_children > 0);
@@ -189,14 +198,14 @@ dsl_dataset_block_kill(dsl_dataset_t *ds, blkptr_t *bp, zio_t *pio,
                        ds->ds_prev->ds_phys->ds_unique_bytes += used;
                        mutex_exit(&ds->ds_prev->ds_lock);
                }
-               if (bp->blk_birth > ds->ds_origin_txg) {
+               if (bp->blk_birth > ds->ds_dir->dd_origin_txg) {
                        dsl_dir_transfer_space(ds->ds_dir, used,
                            DD_USED_HEAD, DD_USED_SNAP, tx);
                }
        }
        mutex_enter(&ds->ds_lock);
-       ASSERT3U(ds->ds_phys->ds_used_bytes, >=, used);
-       ds->ds_phys->ds_used_bytes -= used;
+       ASSERT3U(ds->ds_phys->ds_referenced_bytes, >=, used);
+       ds->ds_phys->ds_referenced_bytes -= used;
        ASSERT3U(ds->ds_phys->ds_compressed_bytes, >=, compressed);
        ds->ds_phys->ds_compressed_bytes -= compressed;
        ASSERT3U(ds->ds_phys->ds_uncompressed_bytes, >=, uncompressed);
@@ -230,9 +239,15 @@ dsl_dataset_prev_snap_txg(dsl_dataset_t *ds)
 }
 
 boolean_t
-dsl_dataset_block_freeable(dsl_dataset_t *ds, uint64_t blk_birth)
+dsl_dataset_block_freeable(dsl_dataset_t *ds, const blkptr_t *bp,
+    uint64_t blk_birth)
 {
-       return (blk_birth > dsl_dataset_prev_snap_txg(ds));
+       if (blk_birth <= dsl_dataset_prev_snap_txg(ds))
+               return (B_FALSE);
+
+       ddt_prefetch(dsl_dataset_get_spa(ds), bp);
+
+       return (B_TRUE);
 }
 
 /* ARGSUSED */
@@ -243,27 +258,31 @@ dsl_dataset_evict(dmu_buf_t *db, void *dsv)
 
        ASSERT(ds->ds_owner == NULL || DSL_DATASET_IS_DESTROYED(ds));
 
-       dprintf_ds(ds, "evicting %s\n", "");
-
        unique_remove(ds->ds_fsid_guid);
 
-       if (ds->ds_user_ptr != NULL)
-               ds->ds_user_evict_func(ds, ds->ds_user_ptr);
+       if (ds->ds_objset != NULL)
+               dmu_objset_evict(ds->ds_objset);
 
        if (ds->ds_prev) {
                dsl_dataset_drop_ref(ds->ds_prev, ds);
                ds->ds_prev = NULL;
        }
 
-       bplist_close(&ds->ds_deadlist);
+       bplist_destroy(&ds->ds_pending_deadlist);
+       if (db != NULL) {
+               dsl_deadlist_close(&ds->ds_deadlist);
+       } else {
+               ASSERT(ds->ds_deadlist.dl_dbuf == NULL);
+               ASSERT(!ds->ds_deadlist.dl_oldfmt);
+       }
        if (ds->ds_dir)
                dsl_dir_close(ds->ds_dir, ds);
 
        ASSERT(!list_link_active(&ds->ds_synced_link));
 
        mutex_destroy(&ds->ds_lock);
+       mutex_destroy(&ds->ds_recvlock);
        mutex_destroy(&ds->ds_opening_lock);
-       mutex_destroy(&ds->ds_deadlist.bpl_lock);
        rw_destroy(&ds->ds_rwlock);
        cv_destroy(&ds->ds_exclusive_cv);
 
@@ -295,7 +314,7 @@ dsl_dataset_get_snapname(dsl_dataset_t *ds)
        return (err);
 }
 
-static int
+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;
@@ -323,6 +342,8 @@ dsl_dataset_snap_remove(dsl_dataset_t *ds, char *name, dmu_tx_t *tx)
        matchtype_t mt;
        int err;
 
+       dsl_dir_snap_cmtime_update(ds->ds_dir);
+
        if (ds->ds_phys->ds_flags & DS_FLAG_CI_DATASET)
                mt = MT_FIRST;
        else
@@ -342,6 +363,7 @@ dsl_dataset_get_ref(dsl_pool_t *dp, uint64_t dsobj, void *tag,
        dmu_buf_t *dbuf;
        dsl_dataset_t *ds;
        int err;
+       dmu_object_info_t doi;
 
        ASSERT(RW_LOCK_HELD(&dp->dp_config_rwlock) ||
            dsl_pool_sync_context(dp));
@@ -349,38 +371,49 @@ dsl_dataset_get_ref(dsl_pool_t *dp, uint64_t dsobj, void *tag,
        err = dmu_bonus_hold(mos, dsobj, tag, &dbuf);
        if (err)
                return (err);
+
+       /* Make sure dsobj has the correct object type. */
+       dmu_object_info_from_db(dbuf, &doi);
+       if (doi.doi_type != DMU_OT_DSL_DATASET)
+               return (EINVAL);
+
        ds = dmu_buf_get_user(dbuf);
        if (ds == NULL) {
-               dsl_dataset_t *winner;
+               dsl_dataset_t *winner = NULL;
 
-               ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
+               ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_PUSHPAGE);
                ds->ds_dbuf = dbuf;
                ds->ds_object = dsobj;
                ds->ds_phys = dbuf->db_data;
+               list_link_init(&ds->ds_synced_link);
 
                mutex_init(&ds->ds_lock, NULL, MUTEX_DEFAULT, NULL);
+               mutex_init(&ds->ds_recvlock, NULL, MUTEX_DEFAULT, NULL);
                mutex_init(&ds->ds_opening_lock, NULL, MUTEX_DEFAULT, NULL);
-               mutex_init(&ds->ds_deadlist.bpl_lock, NULL, MUTEX_DEFAULT,
-                   NULL);
-               rw_init(&ds->ds_rwlock, 0, 0, 0);
+               mutex_init(&ds->ds_sendstream_lock, NULL, MUTEX_DEFAULT, NULL);
+
+               rw_init(&ds->ds_rwlock, NULL, RW_DEFAULT, NULL);
                cv_init(&ds->ds_exclusive_cv, NULL, CV_DEFAULT, NULL);
 
-               err = bplist_open(&ds->ds_deadlist,
+               bplist_create(&ds->ds_pending_deadlist);
+               dsl_deadlist_open(&ds->ds_deadlist,
                    mos, ds->ds_phys->ds_deadlist_obj);
+
+               list_create(&ds->ds_sendstreams, sizeof (dmu_sendarg_t),
+                   offsetof(dmu_sendarg_t, dsa_link));
+
                if (err == 0) {
                        err = dsl_dir_open_obj(dp,
                            ds->ds_phys->ds_dir_obj, NULL, ds, &ds->ds_dir);
                }
                if (err) {
-                       /*
-                        * we don't really need to close the blist if we
-                        * just opened it.
-                        */
                        mutex_destroy(&ds->ds_lock);
+                       mutex_destroy(&ds->ds_recvlock);
                        mutex_destroy(&ds->ds_opening_lock);
-                       mutex_destroy(&ds->ds_deadlist.bpl_lock);
                        rw_destroy(&ds->ds_rwlock);
                        cv_destroy(&ds->ds_exclusive_cv);
+                       bplist_destroy(&ds->ds_pending_deadlist);
+                       dsl_deadlist_close(&ds->ds_deadlist);
                        kmem_free(ds, sizeof (dsl_dataset_t));
                        dmu_buf_rele(dbuf, tag);
                        return (err);
@@ -393,21 +426,15 @@ dsl_dataset_get_ref(dsl_pool_t *dp, uint64_t dsobj, void *tag,
                                    ds->ds_phys->ds_prev_snap_obj,
                                    ds, &ds->ds_prev);
                        }
-
-                       if (err == 0 && dsl_dir_is_clone(ds->ds_dir)) {
-                               dsl_dataset_t *origin;
-
-                               err = dsl_dataset_hold_obj(dp,
-                                   ds->ds_dir->dd_phys->dd_origin_obj,
-                                   FTAG, &origin);
-                               if (err == 0) {
-                                       ds->ds_origin_txg =
-                                           origin->ds_phys->ds_creation_txg;
-                                       dsl_dataset_rele(origin, FTAG);
-                               }
+               } else {
+                       if (zfs_flags & ZFS_DEBUG_SNAPNAMES)
+                               err = dsl_dataset_get_snapname(ds);
+                       if (err == 0 && ds->ds_phys->ds_userrefs_obj != 0) {
+                               err = zap_count(
+                                   ds->ds_dir->dd_pool->dp_meta_objset,
+                                   ds->ds_phys->ds_userrefs_obj,
+                                   &ds->ds_userrefs);
                        }
-               } else if (zfs_flags & ZFS_DEBUG_SNAPNAMES) {
-                       err = dsl_dataset_get_snapname(ds);
                }
 
                if (err == 0 && !dsl_dataset_is_snapshot(ds)) {
@@ -443,13 +470,14 @@ dsl_dataset_get_ref(dsl_pool_t *dp, uint64_t dsobj, void *tag,
                            dsl_dataset_evict);
                }
                if (err || winner) {
-                       bplist_close(&ds->ds_deadlist);
+                       bplist_destroy(&ds->ds_pending_deadlist);
+                       dsl_deadlist_close(&ds->ds_deadlist);
                        if (ds->ds_prev)
                                dsl_dataset_drop_ref(ds->ds_prev, ds);
                        dsl_dir_close(ds->ds_dir, ds);
                        mutex_destroy(&ds->ds_lock);
+                       mutex_destroy(&ds->ds_recvlock);
                        mutex_destroy(&ds->ds_opening_lock);
-                       mutex_destroy(&ds->ds_deadlist.bpl_lock);
                        rw_destroy(&ds->ds_rwlock);
                        cv_destroy(&ds->ds_exclusive_cv);
                        kmem_free(ds, sizeof (dsl_dataset_t));
@@ -519,7 +547,15 @@ dsl_dataset_hold_ref(dsl_dataset_t *ds, void *tag)
                        rw_enter(&dp->dp_config_rwlock, RW_READER);
                        return (ENOENT);
                }
+               /*
+                * The dp_config_rwlock lives above the ds_lock. And
+                * we need to check DSL_DATASET_IS_DESTROYED() while
+                * holding the ds_lock, so we have to drop and reacquire
+                * the ds_lock here.
+                */
+               mutex_exit(&ds->ds_lock);
                rw_enter(&dp->dp_config_rwlock, RW_READER);
+               mutex_enter(&ds->ds_lock);
        }
        mutex_exit(&ds->ds_lock);
        return (0);
@@ -537,17 +573,14 @@ dsl_dataset_hold_obj(dsl_pool_t *dp, uint64_t dsobj, void *tag,
 }
 
 int
-dsl_dataset_own_obj(dsl_pool_t *dp, uint64_t dsobj, int flags, void *owner,
-    dsl_dataset_t **dsp)
+dsl_dataset_own_obj(dsl_pool_t *dp, uint64_t dsobj, boolean_t inconsistentok,
+    void *tag, dsl_dataset_t **dsp)
 {
-       int err = dsl_dataset_hold_obj(dp, dsobj, owner, dsp);
-
-       ASSERT(DS_MODE_TYPE(flags) != DS_MODE_USER);
-
+       int err = dsl_dataset_hold_obj(dp, dsobj, tag, dsp);
        if (err)
                return (err);
-       if (!dsl_dataset_tryown(*dsp, DS_MODE_IS_INCONSISTENT(flags), owner)) {
-               dsl_dataset_rele(*dsp, owner);
+       if (!dsl_dataset_tryown(*dsp, inconsistentok, tag)) {
+               dsl_dataset_rele(*dsp, tag);
                *dsp = NULL;
                return (EBUSY);
        }
@@ -614,18 +647,14 @@ out:
 }
 
 int
-dsl_dataset_own(const char *name, int flags, void *owner, dsl_dataset_t **dsp)
+dsl_dataset_own(const char *name, boolean_t inconsistentok,
+    void *tag, dsl_dataset_t **dsp)
 {
-       int err = dsl_dataset_hold(name, owner, dsp);
+       int err = dsl_dataset_hold(name, tag, dsp);
        if (err)
                return (err);
-       if ((*dsp)->ds_phys->ds_num_children > 0 &&
-           !DS_MODE_IS_READONLY(flags)) {
-               dsl_dataset_rele(*dsp, owner);
-               return (EROFS);
-       }
-       if (!dsl_dataset_tryown(*dsp, DS_MODE_IS_INCONSISTENT(flags), owner)) {
-               dsl_dataset_rele(*dsp, owner);
+       if (!dsl_dataset_tryown(*dsp, inconsistentok, tag)) {
+               dsl_dataset_rele(*dsp, tag);
                return (EBUSY);
        }
        return (0);
@@ -697,9 +726,9 @@ dsl_dataset_rele(dsl_dataset_t *ds, void *tag)
 }
 
 void
-dsl_dataset_disown(dsl_dataset_t *ds, void *owner)
+dsl_dataset_disown(dsl_dataset_t *ds, void *tag)
 {
-       ASSERT((ds->ds_owner == owner && ds->ds_dbuf) ||
+       ASSERT((ds->ds_owner == tag && ds->ds_dbuf) ||
            (DSL_DATASET_IS_DESTROYED(ds) && ds->ds_dbuf == NULL));
 
        mutex_enter(&ds->ds_lock);
@@ -710,20 +739,20 @@ dsl_dataset_disown(dsl_dataset_t *ds, void *owner)
        }
        mutex_exit(&ds->ds_lock);
        if (ds->ds_dbuf)
-               dsl_dataset_drop_ref(ds, owner);
+               dsl_dataset_drop_ref(ds, tag);
        else
-               dsl_dataset_evict(ds->ds_dbuf, ds);
+               dsl_dataset_evict(NULL, ds);
 }
 
 boolean_t
-dsl_dataset_tryown(dsl_dataset_t *ds, boolean_t inconsistentok, void *owner)
+dsl_dataset_tryown(dsl_dataset_t *ds, boolean_t inconsistentok, void *tag)
 {
        boolean_t gotit = FALSE;
 
        mutex_enter(&ds->ds_lock);
        if (ds->ds_owner == NULL &&
            (!DS_IS_INCONSISTENT(ds) || inconsistentok)) {
-               ds->ds_owner = owner;
+               ds->ds_owner = tag;
                if (!dsl_pool_sync_context(ds->ds_dir->dd_pool))
                        rw_exit(&ds->ds_rwlock);
                gotit = TRUE;
@@ -774,15 +803,17 @@ dsl_dataset_create_sync_dd(dsl_dir_t *dd, dsl_dataset_t *origin,
            DMU_OT_NONE, 0, tx);
        dsphys->ds_creation_time = gethrestime_sec();
        dsphys->ds_creation_txg = tx->tx_txg == TXG_INITIAL ? 1 : tx->tx_txg;
-       dsphys->ds_deadlist_obj =
-           bplist_create(mos, DSL_DEADLIST_BLOCKSIZE, tx);
 
-       if (origin) {
+       if (origin == NULL) {
+               dsphys->ds_deadlist_obj = dsl_deadlist_alloc(mos, tx);
+       } else {
+               dsl_dataset_t *ohds;
+
                dsphys->ds_prev_snap_obj = origin->ds_object;
                dsphys->ds_prev_snap_txg =
                    origin->ds_phys->ds_creation_txg;
-               dsphys->ds_used_bytes =
-                   origin->ds_phys->ds_used_bytes;
+               dsphys->ds_referenced_bytes =
+                   origin->ds_phys->ds_referenced_bytes;
                dsphys->ds_compressed_bytes =
                    origin->ds_phys->ds_compressed_bytes;
                dsphys->ds_uncompressed_bytes =
@@ -793,6 +824,12 @@ dsl_dataset_create_sync_dd(dsl_dir_t *dd, dsl_dataset_t *origin,
                dmu_buf_will_dirty(origin->ds_dbuf, tx);
                origin->ds_phys->ds_num_children++;
 
+               VERIFY3U(0, ==, dsl_dataset_hold_obj(dp,
+                   origin->ds_dir->dd_phys->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 (origin->ds_phys->ds_next_clones_obj == 0) {
                                origin->ds_phys->ds_next_clones_obj =
@@ -806,6 +843,16 @@ dsl_dataset_create_sync_dd(dsl_dir_t *dd, dsl_dataset_t *origin,
 
                dmu_buf_will_dirty(dd->dd_dbuf, tx);
                dd->dd_phys->dd_origin_obj = origin->ds_object;
+               if (spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
+                       if (origin->ds_dir->dd_phys->dd_clones == 0) {
+                               dmu_buf_will_dirty(origin->ds_dir->dd_dbuf, tx);
+                               origin->ds_dir->dd_phys->dd_clones =
+                                   zap_create(mos,
+                                   DMU_OT_DSL_CLONES, DMU_OT_NONE, 0, tx);
+                       }
+                       VERIFY3U(0, ==, zap_add_int(mos,
+                           origin->ds_dir->dd_phys->dd_clones, dsobj, tx));
+               }
        }
 
        if (spa_version(dp->dp_spa) >= SPA_VERSION_UNIQUE_ACCURATE)
@@ -838,86 +885,144 @@ dsl_dataset_create_sync(dsl_dir_t *pdd, const char *lastname,
 
        dsl_dir_close(dd, FTAG);
 
-       return (dsobj);
-}
-
-struct destroyarg {
-       dsl_sync_task_group_t *dstg;
-       char *snapname;
-       char *failed;
-};
-
-static int
-dsl_snapshot_destroy_one(char *name, void *arg)
-{
-       struct destroyarg *da = arg;
-       dsl_dataset_t *ds;
-       char *cp;
-       int err;
+       /*
+        * If we are creating a clone, make sure we zero out any stale
+        * data from the origin snapshots zil header.
+        */
+       if (origin != NULL) {
+               dsl_dataset_t *ds;
+               objset_t *os;
 
-       (void) strcat(name, "@");
-       (void) strcat(name, da->snapname);
-       err = dsl_dataset_own(name, DS_MODE_READONLY | DS_MODE_INCONSISTENT,
-           da->dstg, &ds);
-       cp = strchr(name, '@');
-       *cp = '\0';
-       if (err == 0) {
-               dsl_dataset_make_exclusive(ds, da->dstg);
-               if (ds->ds_user_ptr) {
-                       ds->ds_user_evict_func(ds, ds->ds_user_ptr);
-                       ds->ds_user_ptr = NULL;
-               }
-               dsl_sync_task_create(da->dstg, dsl_dataset_destroy_check,
-                   dsl_dataset_destroy_sync, ds, da->dstg, 0);
-       } else if (err == ENOENT) {
-               err = 0;
-       } else {
-               (void) strcpy(da->failed, name);
+               VERIFY3U(0, ==, dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds));
+               VERIFY3U(0, ==, dmu_objset_from_ds(ds, &os));
+               bzero(&os->os_zil_header, sizeof (os->os_zil_header));
+               dsl_dataset_dirty(ds, tx);
+               dsl_dataset_rele(ds, FTAG);
        }
-       return (err);
+
+       return (dsobj);
 }
 
 /*
- * Destroy 'snapname' in all descendants of 'fsname'.
+ * The snapshots must all be in the same pool.
  */
-#pragma weak dmu_snapshots_destroy = dsl_snapshots_destroy
 int
-dsl_snapshots_destroy(char *fsname, char *snapname)
+dmu_snapshots_destroy_nvl(nvlist_t *snaps, boolean_t defer, char *failed)
 {
        int err;
-       struct destroyarg da;
        dsl_sync_task_t *dst;
        spa_t *spa;
+       nvpair_t *pair;
+       dsl_sync_task_group_t *dstg;
 
-       err = spa_open(fsname, &spa, FTAG);
+       pair = nvlist_next_nvpair(snaps, NULL);
+       if (pair == NULL)
+               return (0);
+
+       err = spa_open(nvpair_name(pair), &spa, FTAG);
        if (err)
                return (err);
-       da.dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
-       da.snapname = snapname;
-       da.failed = fsname;
+       dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
+
+       for (pair = nvlist_next_nvpair(snaps, NULL); pair != NULL;
+           pair = nvlist_next_nvpair(snaps, pair)) {
+               dsl_dataset_t *ds;
 
-       err = dmu_objset_find(fsname,
-           dsl_snapshot_destroy_one, &da, DS_FIND_CHILDREN);
+               err = dsl_dataset_own(nvpair_name(pair), B_TRUE, dstg, &ds);
+               if (err == 0) {
+                       struct dsl_ds_destroyarg *dsda;
+
+                       dsl_dataset_make_exclusive(ds, dstg);
+                       dsda = kmem_zalloc(sizeof (struct dsl_ds_destroyarg),
+                           KM_SLEEP);
+                       dsda->ds = ds;
+                       dsda->defer = defer;
+                       dsl_sync_task_create(dstg, dsl_dataset_destroy_check,
+                           dsl_dataset_destroy_sync, dsda, dstg, 0);
+               } else if (err == ENOENT) {
+                       err = 0;
+               } else {
+                       (void) strcpy(failed, nvpair_name(pair));
+                       break;
+               }
+       }
 
        if (err == 0)
-               err = dsl_sync_task_group_wait(da.dstg);
+               err = dsl_sync_task_group_wait(dstg);
+
+       for (dst = list_head(&dstg->dstg_tasks); dst;
+           dst = list_next(&dstg->dstg_tasks, dst)) {
+               struct dsl_ds_destroyarg *dsda = dst->dst_arg1;
+               dsl_dataset_t *ds = dsda->ds;
 
-       for (dst = list_head(&da.dstg->dstg_tasks); dst;
-           dst = list_next(&da.dstg->dstg_tasks, dst)) {
-               dsl_dataset_t *ds = dst->dst_arg1;
                /*
                 * Return the file system name that triggered the error
                 */
                if (dst->dst_err) {
-                       dsl_dataset_name(ds, fsname);
-                       *strchr(fsname, '@') = '\0';
+                       dsl_dataset_name(ds, failed);
                }
-               dsl_dataset_disown(ds, da.dstg);
+               ASSERT3P(dsda->rm_origin, ==, NULL);
+               dsl_dataset_disown(ds, dstg);
+               kmem_free(dsda, sizeof (struct dsl_ds_destroyarg));
        }
 
-       dsl_sync_task_group_destroy(da.dstg);
+       dsl_sync_task_group_destroy(dstg);
        spa_close(spa, FTAG);
        return (err);
+
+}
+
+static boolean_t
+dsl_dataset_might_destroy_origin(dsl_dataset_t *ds)
+{
+       boolean_t might_destroy = B_FALSE;
+
+       mutex_enter(&ds->ds_lock);
+       if (ds->ds_phys->ds_num_children == 2 && ds->ds_userrefs == 0 &&
+           DS_IS_DEFER_DESTROY(ds))
+               might_destroy = B_TRUE;
+       mutex_exit(&ds->ds_lock);
+
+       return (might_destroy);
+}
+
+/*
+ * If we're removing a clone, and these three conditions are true:
+ *     1) the clone's origin has no other children
+ *     2) the clone's origin has no user references
+ *     3) the clone's origin has been marked for deferred destruction
+ * Then, prepare to remove the origin as part of this sync task group.
+ */
+static int
+dsl_dataset_origin_rm_prep(struct dsl_ds_destroyarg *dsda, void *tag)
+{
+       dsl_dataset_t *ds = dsda->ds;
+       dsl_dataset_t *origin = ds->ds_prev;
+
+       if (dsl_dataset_might_destroy_origin(origin)) {
+               char *name;
+               int namelen;
+               int error;
+
+               namelen = dsl_dataset_namelen(origin) + 1;
+               name = kmem_alloc(namelen, KM_SLEEP);
+               dsl_dataset_name(origin, name);
+#ifdef _KERNEL
+               error = zfs_unmount_snap(name, NULL);
+               if (error) {
+                       kmem_free(name, namelen);
+                       return (error);
+               }
+#endif
+               error = dsl_dataset_own(name, B_TRUE, tag, &origin);
+               kmem_free(name, namelen);
+               if (error)
+                       return (error);
+               dsda->rm_origin = origin;
+               dsl_dataset_make_exclusive(origin, tag);
+       }
+
+       return (0);
 }
 
 /*
@@ -925,161 +1030,149 @@ dsl_snapshots_destroy(char *fsname, char *snapname)
  * ds will be closed and caller can no longer dereference it.
  */
 int
-dsl_dataset_destroy(dsl_dataset_t *ds, void *tag)
+dsl_dataset_destroy(dsl_dataset_t *ds, void *tag, boolean_t defer)
 {
        int err;
        dsl_sync_task_group_t *dstg;
        objset_t *os;
        dsl_dir_t *dd;
        uint64_t obj;
+       struct dsl_ds_destroyarg dsda = { 0 };
+       dsl_dataset_t *dummy_ds;
+
+       dsda.ds = ds;
 
        if (dsl_dataset_is_snapshot(ds)) {
                /* Destroying a snapshot is simpler */
                dsl_dataset_make_exclusive(ds, tag);
 
-               if (ds->ds_user_ptr) {
-                       ds->ds_user_evict_func(ds, ds->ds_user_ptr);
-                       ds->ds_user_ptr = NULL;
-               }
+               dsda.defer = defer;
                err = dsl_sync_task_do(ds->ds_dir->dd_pool,
                    dsl_dataset_destroy_check, dsl_dataset_destroy_sync,
-                   ds, tag, 0);
+                   &dsda, tag, 0);
+               ASSERT3P(dsda.rm_origin, ==, NULL);
+               goto out;
+       } else if (defer) {
+               err = EINVAL;
                goto out;
        }
 
        dd = ds->ds_dir;
+       dummy_ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
+       dummy_ds->ds_dir = dd;
+       dummy_ds->ds_object = ds->ds_object;
 
-       /*
-        * Check for errors and mark this ds as inconsistent, in
-        * case we crash while freeing the objects.
-        */
-       err = dsl_sync_task_do(dd->dd_pool, dsl_dataset_destroy_begin_check,
-           dsl_dataset_destroy_begin_sync, ds, NULL, 0);
-       if (err)
-               goto out;
+       if (!spa_feature_is_enabled(dsl_dataset_get_spa(ds),
+           &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY])) {
+               /*
+                * Check for errors and mark this ds as inconsistent, in
+                * case we crash while freeing the objects.
+                */
+               err = dsl_sync_task_do(dd->dd_pool,
+                   dsl_dataset_destroy_begin_check,
+                   dsl_dataset_destroy_begin_sync, ds, NULL, 0);
+               if (err)
+                       goto out_free;
 
-       err = dmu_objset_open_ds(ds, DMU_OST_ANY, &os);
-       if (err)
-               goto out;
+               err = dmu_objset_from_ds(ds, &os);
+               if (err)
+                       goto out_free;
 
-       /*
-        * remove the objects in open context, so that we won't
-        * have too much to do in syncing context.
-        */
-       for (obj = 0; err == 0; err = dmu_object_next(os, &obj, FALSE,
-           ds->ds_phys->ds_prev_snap_txg)) {
                /*
-                * Ignore errors, if there is not enough disk space
-                * we will deal with it in dsl_dataset_destroy_sync().
+                * Remove all objects while in the open context so that
+                * there is less work to do in the syncing context.
                 */
-               (void) dmu_free_object(os, obj);
-       }
-
-       /*
-        * We need to sync out all in-flight IO before we try to evict
-        * (the dataset evict func is trying to clear the cached entries
-        * for this dataset in the ARC).
-        */
-       txg_wait_synced(dd->dd_pool, 0);
+               for (obj = 0; err == 0; err = dmu_object_next(os, &obj, FALSE,
+                   ds->ds_phys->ds_prev_snap_txg)) {
+                       /*
+                        * Ignore errors, if there is not enough disk space
+                        * we will deal with it in dsl_dataset_destroy_sync().
+                        */
+                       (void) dmu_free_object(os, obj);
+               }
+               if (err != ESRCH)
+                       goto out_free;
 
-       /*
-        * If we managed to free all the objects in open
-        * context, the user space accounting should be zero.
-        */
-       if (ds->ds_phys->ds_bp.blk_fill == 0 &&
-           dmu_objset_userused_enabled(os->os)) {
-               uint64_t count;
+               /*
+                * Sync out all in-flight IO.
+                */
+               txg_wait_synced(dd->dd_pool, 0);
 
-               ASSERT(zap_count(os, DMU_USERUSED_OBJECT, &count) != 0 ||
-                   count == 0);
-               ASSERT(zap_count(os, DMU_GROUPUSED_OBJECT, &count) != 0 ||
-                   count == 0);
+               /*
+                * If we managed to free all the objects in open
+                * context, the user space accounting should be zero.
+                */
+               if (ds->ds_phys->ds_bp.blk_fill == 0 &&
+                   dmu_objset_userused_enabled(os)) {
+                       ASSERTV(uint64_t count);
+
+                       ASSERT(zap_count(os, DMU_USERUSED_OBJECT,
+                           &count) != 0 || count == 0);
+                       ASSERT(zap_count(os, DMU_GROUPUSED_OBJECT,
+                           &count) != 0 || count == 0);
+               }
        }
 
-       dmu_objset_close(os);
-       if (err != ESRCH)
-               goto out;
-
        rw_enter(&dd->dd_pool->dp_config_rwlock, RW_READER);
        err = dsl_dir_open_obj(dd->dd_pool, dd->dd_object, NULL, FTAG, &dd);
        rw_exit(&dd->dd_pool->dp_config_rwlock);
 
        if (err)
-               goto out;
-
-       if (ds->ds_user_ptr) {
-               /*
-                * We need to sync out all in-flight IO before we try
-                * to evict (the dataset evict func is trying to clear
-                * the cached entries for this dataset in the ARC).
-                */
-               txg_wait_synced(dd->dd_pool, 0);
-       }
+               goto out_free;
 
        /*
         * Blow away the dsl_dir + head dataset.
         */
        dsl_dataset_make_exclusive(ds, tag);
-       if (ds->ds_user_ptr) {
-               ds->ds_user_evict_func(ds, ds->ds_user_ptr);
-               ds->ds_user_ptr = NULL;
-       }
-       dstg = dsl_sync_task_group_create(ds->ds_dir->dd_pool);
-       dsl_sync_task_create(dstg, dsl_dataset_destroy_check,
-           dsl_dataset_destroy_sync, ds, tag, 0);
-       dsl_sync_task_create(dstg, dsl_dir_destroy_check,
-           dsl_dir_destroy_sync, dd, FTAG, 0);
-       err = dsl_sync_task_group_wait(dstg);
-       dsl_sync_task_group_destroy(dstg);
+       /*
+        * If we're removing a clone, we might also need to remove its
+        * origin.
+        */
+       do {
+               dsda.need_prep = B_FALSE;
+               if (dsl_dir_is_clone(dd)) {
+                       err = dsl_dataset_origin_rm_prep(&dsda, tag);
+                       if (err) {
+                               dsl_dir_close(dd, FTAG);
+                               goto out_free;
+                       }
+               }
+
+               dstg = dsl_sync_task_group_create(ds->ds_dir->dd_pool);
+               dsl_sync_task_create(dstg, dsl_dataset_destroy_check,
+                   dsl_dataset_destroy_sync, &dsda, tag, 0);
+               dsl_sync_task_create(dstg, dsl_dir_destroy_check,
+                   dsl_dir_destroy_sync, dummy_ds, FTAG, 0);
+               err = dsl_sync_task_group_wait(dstg);
+               dsl_sync_task_group_destroy(dstg);
+
+               /*
+                * We could be racing against 'zfs release' or 'zfs destroy -d'
+                * on the origin snap, in which case we can get EBUSY if we
+                * needed to destroy the origin snap but were not ready to
+                * do so.
+                */
+               if (dsda.need_prep) {
+                       ASSERT(err == EBUSY);
+                       ASSERT(dsl_dir_is_clone(dd));
+                       ASSERT(dsda.rm_origin == NULL);
+               }
+       } while (dsda.need_prep);
+
+       if (dsda.rm_origin != NULL)
+               dsl_dataset_disown(dsda.rm_origin, tag);
+
        /* if it is successful, dsl_dir_destroy_sync will close the dd */
        if (err)
                dsl_dir_close(dd, FTAG);
+
+out_free:
+       kmem_free(dummy_ds, sizeof (dsl_dataset_t));
 out:
        dsl_dataset_disown(ds, tag);
        return (err);
 }
 
-int
-dsl_dataset_rollback(dsl_dataset_t *ds, dmu_objset_type_t ost)
-{
-       int err;
-
-       ASSERT(ds->ds_owner);
-
-       dsl_dataset_make_exclusive(ds, ds->ds_owner);
-       err = dsl_sync_task_do(ds->ds_dir->dd_pool,
-           dsl_dataset_rollback_check, dsl_dataset_rollback_sync,
-           ds, &ost, 0);
-       /* drop exclusive access */
-       mutex_enter(&ds->ds_lock);
-       rw_exit(&ds->ds_rwlock);
-       cv_broadcast(&ds->ds_exclusive_cv);
-       mutex_exit(&ds->ds_lock);
-       return (err);
-}
-
-void *
-dsl_dataset_set_user_ptr(dsl_dataset_t *ds,
-    void *p, dsl_dataset_evict_func_t func)
-{
-       void *old;
-
-       mutex_enter(&ds->ds_lock);
-       old = ds->ds_user_ptr;
-       if (old == NULL) {
-               ds->ds_user_ptr = p;
-               ds->ds_user_evict_func = func;
-       }
-       mutex_exit(&ds->ds_lock);
-       return (old);
-}
-
-void *
-dsl_dataset_get_user_ptr(dsl_dataset_t *ds)
-{
-       return (ds->ds_user_ptr);
-}
-
 blkptr_t *
 dsl_dataset_get_blkptr(dsl_dataset_t *ds)
 {
@@ -1113,7 +1206,7 @@ dsl_dataset_dirty(dsl_dataset_t *ds, dmu_tx_t *tx)
        if (ds == NULL) /* this is the meta-objset */
                return;
 
-       ASSERT(ds->ds_user_ptr != NULL);
+       ASSERT(ds->ds_objset != NULL);
 
        if (ds->ds_phys->ds_next_snap_obj != 0)
                panic("dirtying snapshot!");
@@ -1126,6 +1219,19 @@ dsl_dataset_dirty(dsl_dataset_t *ds, dmu_tx_t *tx)
        }
 }
 
+boolean_t
+dsl_dataset_is_dirty(dsl_dataset_t *ds)
+{
+       int t;
+
+       for (t = 0; t < TXG_SIZE; t++) {
+               if (txg_list_member(&ds->ds_dir->dd_pool->dp_dirty_datasets,
+                   ds, t))
+                       return (B_TRUE);
+       }
+       return (B_FALSE);
+}
+
 /*
  * 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
@@ -1140,62 +1246,51 @@ dsl_dataset_recalc_head_uniq(dsl_dataset_t *ds)
        uint64_t mrs_used;
        uint64_t dlused, dlcomp, dluncomp;
 
-       ASSERT(ds->ds_object == ds->ds_dir->dd_phys->dd_head_dataset_obj);
+       ASSERT(!dsl_dataset_is_snapshot(ds));
 
        if (ds->ds_phys->ds_prev_snap_obj != 0)
-               mrs_used = ds->ds_prev->ds_phys->ds_used_bytes;
+               mrs_used = ds->ds_prev->ds_phys->ds_referenced_bytes;
        else
                mrs_used = 0;
 
-       VERIFY(0 == bplist_space(&ds->ds_deadlist, &dlused, &dlcomp,
-           &dluncomp));
+       dsl_deadlist_space(&ds->ds_deadlist, &dlused, &dlcomp, &dluncomp);
 
        ASSERT3U(dlused, <=, mrs_used);
        ds->ds_phys->ds_unique_bytes =
-           ds->ds_phys->ds_used_bytes - (mrs_used - dlused);
+           ds->ds_phys->ds_referenced_bytes - (mrs_used - dlused);
 
-       if (!DS_UNIQUE_IS_ACCURATE(ds) &&
-           spa_version(ds->ds_dir->dd_pool->dp_spa) >=
+       if (spa_version(ds->ds_dir->dd_pool->dp_spa) >=
            SPA_VERSION_UNIQUE_ACCURATE)
                ds->ds_phys->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;
 }
 
-static uint64_t
-dsl_dataset_unique(dsl_dataset_t *ds)
-{
-       if (!DS_UNIQUE_IS_ACCURATE(ds) && !dsl_dataset_is_snapshot(ds))
-               dsl_dataset_recalc_head_uniq(ds);
-
-       return (ds->ds_phys->ds_unique_bytes);
-}
-
 struct killarg {
        dsl_dataset_t *ds;
-       zio_t *zio;
        dmu_tx_t *tx;
 };
 
 /* ARGSUSED */
 static int
-kill_blkptr(spa_t *spa, blkptr_t *bp, const zbookmark_t *zb,
-    const dnode_phys_t *dnp, void *arg)
+kill_blkptr(spa_t *spa, zilog_t *zilog, const blkptr_t *bp, arc_buf_t *pbuf,
+    const zbookmark_t *zb, const dnode_phys_t *dnp, void *arg)
 {
        struct killarg *ka = arg;
+       dmu_tx_t *tx = ka->tx;
 
        if (bp == NULL)
                return (0);
 
-       if ((zb->zb_level == -1ULL && zb->zb_blkid != 0) ||
-           (zb->zb_object != 0 && dnp == NULL)) {
+       if (zb->zb_level == ZB_ZIL_LEVEL) {
+               ASSERT(zilog != NULL);
                /*
                 * It's a block in the intent log.  It has no
                 * accounting, so just free it.
                 */
-               VERIFY3U(0, ==, dsl_free(ka->zio, ka->tx->tx_pool,
-                   ka->tx->tx_txg, bp, NULL, NULL, ARC_NOWAIT));
+               dsl_free(ka->tx->tx_pool, ka->tx->tx_txg, bp);
        } else {
+               ASSERT(zilog == NULL);
                ASSERT3U(bp->blk_birth, >, ka->ds->ds_phys->ds_prev_snap_txg);
-               (void) dsl_dataset_block_kill(ka->ds, bp, ka->zio, ka->tx);
+               (void) dsl_dataset_block_kill(ka->ds, bp, tx, B_FALSE);
        }
 
        return (0);
@@ -1203,200 +1298,113 @@ kill_blkptr(spa_t *spa, blkptr_t *bp, const zbookmark_t *zb,
 
 /* ARGSUSED */
 static int
-dsl_dataset_rollback_check(void *arg1, void *arg2, dmu_tx_t *tx)
+dsl_dataset_destroy_begin_check(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
-       dmu_objset_type_t *ost = arg2;
-
-       /*
-        * We can only roll back to emptyness if it is a ZPL objset.
-        */
-       if (*ost != DMU_OST_ZFS && ds->ds_phys->ds_prev_snap_txg == 0)
-               return (EINVAL);
+       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       uint64_t count;
+       int err;
 
        /*
-        * This must not be a snapshot.
+        * Can't delete a head dataset if there are snapshots of it.
+        * (Except if the only snapshots are from the branch we cloned
+        * from.)
         */
-       if (ds->ds_phys->ds_next_snap_obj != 0)
-               return (EINVAL);
+       if (ds->ds_prev != NULL &&
+           ds->ds_prev->ds_phys->ds_next_snap_obj == ds->ds_object)
+               return (EBUSY);
 
        /*
-        * If we made changes this txg, traverse_dataset won't find
-        * them.  Try again.
+        * This is really a dsl_dir thing, but check it here so that
+        * we'll be less likely to leave this dataset inconsistent &
+        * nearly destroyed.
         */
-       if (ds->ds_phys->ds_bp.blk_birth >= tx->tx_txg)
-               return (EAGAIN);
+       err = zap_count(mos, ds->ds_dir->dd_phys->dd_child_dir_zapobj, &count);
+       if (err)
+               return (err);
+       if (count != 0)
+               return (EEXIST);
 
        return (0);
 }
 
 /* ARGSUSED */
 static void
-dsl_dataset_rollback_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
+dsl_dataset_destroy_begin_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
-       dmu_objset_type_t *ost = arg2;
-       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       dsl_pool_t *dp = ds->ds_dir->dd_pool;
 
+       /* Mark it as inconsistent on-disk, in case we crash */
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
+       ds->ds_phys->ds_flags |= DS_FLAG_INCONSISTENT;
 
-       if (ds->ds_user_ptr != NULL) {
-               /*
-                * We need to make sure that the objset_impl_t is reopened after
-                * we do the rollback, otherwise it will have the wrong
-                * objset_phys_t.  Normally this would happen when this
-                * dataset-open is closed, thus causing the
-                * dataset to be immediately evicted.  But when doing "zfs recv
-                * -F", we reopen the objset before that, so that there is no
-                * window where the dataset is closed and inconsistent.
-                */
-               ds->ds_user_evict_func(ds, ds->ds_user_ptr);
-               ds->ds_user_ptr = NULL;
-       }
-
-       /* Transfer space that was freed since last snap back to the head. */
-       {
-               uint64_t used;
+       spa_history_log_internal(LOG_DS_DESTROY_BEGIN, dp->dp_spa, tx,
+           "dataset = %llu", ds->ds_object);
+}
 
-               VERIFY(0 == bplist_space_birthrange(&ds->ds_deadlist,
-                   ds->ds_origin_txg, UINT64_MAX, &used));
-               dsl_dir_transfer_space(ds->ds_dir, used,
-                   DD_USED_SNAP, DD_USED_HEAD, tx);
-       }
+static int
+dsl_dataset_origin_check(struct dsl_ds_destroyarg *dsda, void *tag,
+    dmu_tx_t *tx)
+{
+       dsl_dataset_t *ds = dsda->ds;
+       dsl_dataset_t *ds_prev = ds->ds_prev;
 
-       /* Zero out the deadlist. */
-       bplist_close(&ds->ds_deadlist);
-       bplist_destroy(mos, ds->ds_phys->ds_deadlist_obj, tx);
-       ds->ds_phys->ds_deadlist_obj =
-           bplist_create(mos, DSL_DEADLIST_BLOCKSIZE, tx);
-       VERIFY(0 == bplist_open(&ds->ds_deadlist, mos,
-           ds->ds_phys->ds_deadlist_obj));
+       if (dsl_dataset_might_destroy_origin(ds_prev)) {
+               struct dsl_ds_destroyarg ndsda = {0};
 
-       {
                /*
-                * Free blkptrs that we gave birth to - this covers
-                * claimed but not played log blocks too.
+                * If we're not prepared to remove the origin, don't remove
+                * the clone either.
                 */
-               zio_t *zio;
-               struct killarg ka;
+               if (dsda->rm_origin == NULL) {
+                       dsda->need_prep = B_TRUE;
+                       return (EBUSY);
+               }
 
-               zio = zio_root(tx->tx_pool->dp_spa, NULL, NULL,
-                   ZIO_FLAG_MUSTSUCCEED);
-               ka.ds = ds;
-               ka.zio = zio;
-               ka.tx = tx;
-               (void) traverse_dataset(ds, ds->ds_phys->ds_prev_snap_txg,
-                   TRAVERSE_POST, kill_blkptr, &ka);
-               (void) zio_wait(zio);
+               ndsda.ds = ds_prev;
+               ndsda.is_origin_rm = B_TRUE;
+               return (dsl_dataset_destroy_check(&ndsda, tag, tx));
        }
 
-       ASSERT(!DS_UNIQUE_IS_ACCURATE(ds) || ds->ds_phys->ds_unique_bytes == 0);
-
-       if (ds->ds_prev && ds->ds_prev != ds->ds_dir->dd_pool->dp_origin_snap) {
-               /* Change our contents to that of the prev snapshot */
-
-               ASSERT3U(ds->ds_prev->ds_object, ==,
-                   ds->ds_phys->ds_prev_snap_obj);
-               ASSERT3U(ds->ds_phys->ds_used_bytes, <=,
-                   ds->ds_prev->ds_phys->ds_used_bytes);
-
-               ds->ds_phys->ds_bp = ds->ds_prev->ds_phys->ds_bp;
-               ds->ds_phys->ds_used_bytes =
-                   ds->ds_prev->ds_phys->ds_used_bytes;
-               ds->ds_phys->ds_compressed_bytes =
-                   ds->ds_prev->ds_phys->ds_compressed_bytes;
-               ds->ds_phys->ds_uncompressed_bytes =
-                   ds->ds_prev->ds_phys->ds_uncompressed_bytes;
-               ds->ds_phys->ds_flags = ds->ds_prev->ds_phys->ds_flags;
-
-               if (ds->ds_prev->ds_phys->ds_next_snap_obj == ds->ds_object) {
-                       dmu_buf_will_dirty(ds->ds_prev->ds_dbuf, tx);
-                       ds->ds_prev->ds_phys->ds_unique_bytes = 0;
-               }
-       } else {
-               objset_impl_t *osi;
-
-               ASSERT3U(ds->ds_phys->ds_used_bytes, ==, 0);
-               ASSERT3U(ds->ds_phys->ds_compressed_bytes, ==, 0);
-               ASSERT3U(ds->ds_phys->ds_uncompressed_bytes, ==, 0);
-
-               bzero(&ds->ds_phys->ds_bp, sizeof (blkptr_t));
-               ds->ds_phys->ds_flags = 0;
-               ds->ds_phys->ds_unique_bytes = 0;
-               if (spa_version(ds->ds_dir->dd_pool->dp_spa) >=
-                   SPA_VERSION_UNIQUE_ACCURATE)
-                       ds->ds_phys->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;
-
-               osi = dmu_objset_create_impl(ds->ds_dir->dd_pool->dp_spa, ds,
-                   &ds->ds_phys->ds_bp, *ost, tx);
-#ifdef _KERNEL
-               zfs_create_fs(&osi->os, kcred, NULL, tx);
-#endif
-       }
-
-       spa_history_internal_log(LOG_DS_ROLLBACK, ds->ds_dir->dd_pool->dp_spa,
-           tx, cr, "dataset = %llu", ds->ds_object);
-}
-
-/* ARGSUSED */
-static int
-dsl_dataset_destroy_begin_check(void *arg1, void *arg2, dmu_tx_t *tx)
-{
-       dsl_dataset_t *ds = arg1;
-       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
-       uint64_t count;
-       int err;
-
-       /*
-        * Can't delete a head dataset if there are snapshots of it.
-        * (Except if the only snapshots are from the branch we cloned
-        * from.)
-        */
-       if (ds->ds_prev != NULL &&
-           ds->ds_prev->ds_phys->ds_next_snap_obj == ds->ds_object)
-               return (EINVAL);
-
        /*
-        * This is really a dsl_dir thing, but check it here so that
-        * we'll be less likely to leave this dataset inconsistent &
-        * nearly destroyed.
+        * If we're not going to remove the origin after all,
+        * undo the open context setup.
         */
-       err = zap_count(mos, ds->ds_dir->dd_phys->dd_child_dir_zapobj, &count);
-       if (err)
-               return (err);
-       if (count != 0)
-               return (EEXIST);
+       if (dsda->rm_origin != NULL) {
+               dsl_dataset_disown(dsda->rm_origin, tag);
+               dsda->rm_origin = NULL;
+       }
 
        return (0);
 }
 
-/* ARGSUSED */
-static void
-dsl_dataset_destroy_begin_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
-{
-       dsl_dataset_t *ds = arg1;
-       dsl_pool_t *dp = ds->ds_dir->dd_pool;
-
-       /* Mark it as inconsistent on-disk, in case we crash */
-       dmu_buf_will_dirty(ds->ds_dbuf, tx);
-       ds->ds_phys->ds_flags |= DS_FLAG_INCONSISTENT;
-
-       spa_history_internal_log(LOG_DS_DESTROY_BEGIN, dp->dp_spa, tx,
-           cr, "dataset = %llu", ds->ds_object);
-}
-
+/*
+ * If you add new checks here, you may need to add
+ * additional checks to the "temporary" case in
+ * snapshot_check() in dmu_objset.c.
+ */
 /* ARGSUSED */
 int
 dsl_dataset_destroy_check(void *arg1, void *arg2, dmu_tx_t *tx)
 {
-       dsl_dataset_t *ds = arg1;
+       struct dsl_ds_destroyarg *dsda = arg1;
+       dsl_dataset_t *ds = dsda->ds;
 
        /* we have an owner hold, so noone else can destroy us */
        ASSERT(!DSL_DATASET_IS_DESTROYED(ds));
 
-       /* Can't delete a branch point. */
-       if (ds->ds_phys->ds_num_children > 1)
-               return (EEXIST);
+       /*
+        * Only allow deferred destroy on pools that support it.
+        * NOTE: deferred destroy is only supported on snapshots.
+        */
+       if (dsda->defer) {
+               if (spa_version(ds->ds_dir->dd_pool->dp_spa) <
+                   SPA_VERSION_USERREFS)
+                       return (ENOTSUP);
+               ASSERT(dsl_dataset_is_snapshot(ds));
+               return (0);
+       }
 
        /*
         * Can't delete a head dataset if there are snapshots of it.
@@ -1405,7 +1413,7 @@ dsl_dataset_destroy_check(void *arg1, void *arg2, dmu_tx_t *tx)
         */
        if (ds->ds_prev != NULL &&
            ds->ds_prev->ds_phys->ds_next_snap_obj == ds->ds_object)
-               return (EINVAL);
+               return (EBUSY);
 
        /*
         * If we made changes this txg, traverse_dsl_dataset won't find
@@ -1414,6 +1422,31 @@ dsl_dataset_destroy_check(void *arg1, void *arg2, dmu_tx_t *tx)
        if (ds->ds_phys->ds_bp.blk_birth >= tx->tx_txg)
                return (EAGAIN);
 
+       if (dsl_dataset_is_snapshot(ds)) {
+               /*
+                * If this snapshot has an elevated user reference count,
+                * we can't destroy it yet.
+                */
+               if (ds->ds_userrefs > 0 && !dsda->releasing)
+                       return (EBUSY);
+
+               mutex_enter(&ds->ds_lock);
+               /*
+                * Can't delete a branch point. However, if we're destroying
+                * a clone and removing its origin due to it having a user
+                * hold count of 0 and having been marked for deferred destroy,
+                * it's OK for the origin to have a single clone.
+                */
+               if (ds->ds_phys->ds_num_children >
+                   (dsda->is_origin_rm ? 2 : 1)) {
+                       mutex_exit(&ds->ds_lock);
+                       return (EEXIST);
+               }
+               mutex_exit(&ds->ds_lock);
+       } else if (dsl_dir_is_clone(ds->ds_dir)) {
+               return (dsl_dataset_origin_check(dsda, arg2, tx));
+       }
+
        /* XXX we should do some i/o error checking... */
        return (0);
 }
@@ -1458,24 +1491,183 @@ dsl_dataset_drain_refs(dsl_dataset_t *ds, void *tag)
        cv_destroy(&arg.cv);
 }
 
-void
-dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
+static void
+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;
+       int err;
+       ASSERTV(uint64_t count);
+
+       ASSERT(ds->ds_phys->ds_num_children >= 2);
+       err = zap_remove_int(mos, ds->ds_phys->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);
+       }
+       ASSERT3U(0, ==, zap_count(mos, ds->ds_phys->ds_next_clones_obj,
+           &count));
+       ASSERT3U(count, <=, ds->ds_phys->ds_num_children - 2);
+}
+
+static void
+dsl_dataset_remove_clones_key(dsl_dataset_t *ds, uint64_t mintxg, dmu_tx_t *tx)
+{
+       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       zap_cursor_t zc;
+       zap_attribute_t za;
+
+       /*
+        * If it is the old version, dd_clones doesn't exist so we can't
+        * find the clones, but deadlist_remove_key() is a no-op so it
+        * doesn't matter.
+        */
+       if (ds->ds_dir->dd_phys->dd_clones == 0)
+               return;
+
+       for (zap_cursor_init(&zc, mos, ds->ds_dir->dd_phys->dd_clones);
+           zap_cursor_retrieve(&zc, &za) == 0;
+           zap_cursor_advance(&zc)) {
+               dsl_dataset_t *clone;
+
+               VERIFY3U(0, ==, dsl_dataset_hold_obj(ds->ds_dir->dd_pool,
+                   za.za_first_integer, FTAG, &clone));
+               if (clone->ds_dir->dd_origin_txg > mintxg) {
+                       dsl_deadlist_remove_key(&clone->ds_deadlist,
+                           mintxg, tx);
+                       dsl_dataset_remove_clones_key(clone, mintxg, tx);
+               }
+               dsl_dataset_rele(clone, FTAG);
+       }
+       zap_cursor_fini(&zc);
+}
+
+struct process_old_arg {
+       dsl_dataset_t *ds;
+       dsl_dataset_t *ds_prev;
+       boolean_t after_branch_point;
+       zio_t *pio;
+       uint64_t used, comp, uncomp;
+};
+
+static int
+process_old_cb(void *arg, const blkptr_t *bp, dmu_tx_t *tx)
+{
+       struct process_old_arg *poa = arg;
+       dsl_pool_t *dp = poa->ds->ds_dir->dd_pool;
+
+       if (bp->blk_birth <= poa->ds->ds_phys->ds_prev_snap_txg) {
+               dsl_deadlist_insert(&poa->ds->ds_deadlist, bp, tx);
+               if (poa->ds_prev && !poa->after_branch_point &&
+                   bp->blk_birth >
+                   poa->ds_prev->ds_phys->ds_prev_snap_txg) {
+                       poa->ds_prev->ds_phys->ds_unique_bytes +=
+                           bp_get_dsize_sync(dp->dp_spa, bp);
+               }
+       } else {
+               poa->used += bp_get_dsize_sync(dp->dp_spa, bp);
+               poa->comp += BP_GET_PSIZE(bp);
+               poa->uncomp += BP_GET_UCSIZE(bp);
+               dsl_free_sync(poa->pio, dp, tx->tx_txg, bp);
+       }
+       return (0);
+}
+
+static void
+process_old_deadlist(dsl_dataset_t *ds, dsl_dataset_t *ds_prev,
+    dsl_dataset_t *ds_next, boolean_t after_branch_point, dmu_tx_t *tx)
+{
+       struct process_old_arg poa = { 0 };
+       dsl_pool_t *dp = ds->ds_dir->dd_pool;
+       objset_t *mos = dp->dp_meta_objset;
+
+       ASSERT(ds->ds_deadlist.dl_oldfmt);
+       ASSERT(ds_next->ds_deadlist.dl_oldfmt);
+
+       poa.ds = ds;
+       poa.ds_prev = ds_prev;
+       poa.after_branch_point = after_branch_point;
+       poa.pio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
+       VERIFY3U(0, ==, bpobj_iterate(&ds_next->ds_deadlist.dl_bpobj,
+           process_old_cb, &poa, tx));
+       VERIFY0(zio_wait(poa.pio));
+       ASSERT3U(poa.used, ==, ds->ds_phys->ds_unique_bytes);
+
+       /* change snapused */
+       dsl_dir_diduse_space(ds->ds_dir, DD_USED_SNAP,
+           -poa.used, -poa.comp, -poa.uncomp, tx);
+
+       /* swap next's deadlist to our deadlist */
+       dsl_deadlist_close(&ds->ds_deadlist);
+       dsl_deadlist_close(&ds_next->ds_deadlist);
+       SWITCH64(ds_next->ds_phys->ds_deadlist_obj,
+           ds->ds_phys->ds_deadlist_obj);
+       dsl_deadlist_open(&ds->ds_deadlist, mos, ds->ds_phys->ds_deadlist_obj);
+       dsl_deadlist_open(&ds_next->ds_deadlist, mos,
+           ds_next->ds_phys->ds_deadlist_obj);
+}
+
+static int
+old_synchronous_dataset_destroy(dsl_dataset_t *ds, dmu_tx_t *tx)
 {
-       dsl_dataset_t *ds = arg1;
-       zio_t *zio;
        int err;
+       struct killarg ka;
+
+       /*
+        * Free everything that we point to (that's born after
+        * the previous snapshot, if we are a clone)
+        *
+        * NB: this should be very quick, because we already
+        * freed all the objects in open context.
+        */
+       ka.ds = ds;
+       ka.tx = tx;
+       err = traverse_dataset(ds,
+           ds->ds_phys->ds_prev_snap_txg, TRAVERSE_POST,
+           kill_blkptr, &ka);
+       ASSERT0(err);
+       ASSERT(!DS_UNIQUE_IS_ACCURATE(ds) || ds->ds_phys->ds_unique_bytes == 0);
+
+       return (err);
+}
+
+void
+dsl_dataset_destroy_sync(void *arg1, void *tag, dmu_tx_t *tx)
+{
+       struct dsl_ds_destroyarg *dsda = arg1;
+       dsl_dataset_t *ds = dsda->ds;
+       int err = 0;
        int after_branch_point = FALSE;
        dsl_pool_t *dp = ds->ds_dir->dd_pool;
        objset_t *mos = dp->dp_meta_objset;
        dsl_dataset_t *ds_prev = NULL;
+       boolean_t wont_destroy;
        uint64_t obj;
 
-       ASSERT(ds->ds_owner);
-       ASSERT3U(ds->ds_phys->ds_num_children, <=, 1);
+       wont_destroy = (dsda->defer &&
+           (ds->ds_userrefs > 0 || ds->ds_phys->ds_num_children > 1));
+
+       ASSERT(ds->ds_owner || wont_destroy);
+       ASSERT(dsda->defer || ds->ds_phys->ds_num_children <= 1);
        ASSERT(ds->ds_prev == NULL ||
            ds->ds_prev->ds_phys->ds_next_snap_obj != ds->ds_object);
        ASSERT3U(ds->ds_phys->ds_bp.blk_birth, <=, tx->tx_txg);
 
+       if (wont_destroy) {
+               ASSERT(spa_version(dp->dp_spa) >= SPA_VERSION_USERREFS);
+               dmu_buf_will_dirty(ds->ds_dbuf, tx);
+               ds->ds_phys->ds_flags |= DS_FLAG_DEFER_DESTROY;
+               return;
+       }
+
        /* signal any waiters that this dataset is going away */
        mutex_enter(&ds->ds_lock);
        ds->ds_owner = dsl_reaper;
@@ -1484,14 +1676,21 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
 
        /* Remove our reservation */
        if (ds->ds_reserved != 0) {
-               uint64_t val = 0;
-               dsl_dataset_set_reservation_sync(ds, &val, cr, tx);
-               ASSERT3U(ds->ds_reserved, ==, 0);
+               dsl_prop_setarg_t psa;
+               uint64_t value = 0;
+
+               dsl_prop_setarg_init_uint64(&psa, "refreservation",
+                   (ZPROP_SRC_NONE | ZPROP_SRC_LOCAL | ZPROP_SRC_RECEIVED),
+                   &value);
+               psa.psa_effective_value = 0;    /* predict default value */
+
+               dsl_dataset_set_reservation_sync(ds, &psa, tx);
+               ASSERT0(ds->ds_reserved);
        }
 
        ASSERT(RW_WRITE_HELD(&dp->dp_config_rwlock));
 
-       dsl_pool_ds_destroyed(ds, tx);
+       dsl_scan_ds_destroyed(ds, tx);
 
        obj = ds->ds_object;
 
@@ -1508,8 +1707,7 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
                dmu_buf_will_dirty(ds_prev->ds_dbuf, tx);
                if (after_branch_point &&
                    ds_prev->ds_phys->ds_next_clones_obj != 0) {
-                       VERIFY3U(0, ==, zap_remove_int(mos,
-                           ds_prev->ds_phys->ds_next_clones_obj, obj, tx));
+                       remove_from_next_clones(ds_prev, obj, tx);
                        if (ds->ds_phys->ds_next_snap_obj != 0) {
                                VERIFY(0 == zap_add_int(mos,
                                    ds_prev->ds_phys->ds_next_clones_obj,
@@ -1521,26 +1719,36 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
                        /* This clone is toast. */
                        ASSERT(ds_prev->ds_phys->ds_num_children > 1);
                        ds_prev->ds_phys->ds_num_children--;
+
+                       /*
+                        * If the clone's origin has no other clones, no
+                        * user holds, and has been marked for deferred
+                        * deletion, then we should have done the necessary
+                        * destroy setup for it.
+                        */
+                       if (ds_prev->ds_phys->ds_num_children == 1 &&
+                           ds_prev->ds_userrefs == 0 &&
+                           DS_IS_DEFER_DESTROY(ds_prev)) {
+                               ASSERT3P(dsda->rm_origin, !=, NULL);
+                       } else {
+                               ASSERT3P(dsda->rm_origin, ==, NULL);
+                       }
                } else if (!after_branch_point) {
                        ds_prev->ds_phys->ds_next_snap_obj =
                            ds->ds_phys->ds_next_snap_obj;
                }
        }
 
-       zio = zio_root(dp->dp_spa, NULL, NULL, ZIO_FLAG_MUSTSUCCEED);
-
-       if (ds->ds_phys->ds_next_snap_obj != 0) {
-               blkptr_t bp;
+       if (dsl_dataset_is_snapshot(ds)) {
                dsl_dataset_t *ds_next;
-               uint64_t itor = 0;
                uint64_t old_unique;
-               int64_t used = 0, compressed = 0, uncompressed = 0;
+               uint64_t used = 0, comp = 0, uncomp = 0;
 
                VERIFY(0 == dsl_dataset_hold_obj(dp,
                    ds->ds_phys->ds_next_snap_obj, FTAG, &ds_next));
                ASSERT3U(ds_next->ds_phys->ds_prev_snap_obj, ==, obj);
 
-               old_unique = dsl_dataset_unique(ds_next);
+               old_unique = ds_next->ds_phys->ds_unique_bytes;
 
                dmu_buf_will_dirty(ds_next->ds_dbuf, tx);
                ds_next->ds_phys->ds_prev_snap_obj =
@@ -1550,53 +1758,49 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
                ASSERT3U(ds->ds_phys->ds_prev_snap_txg, ==,
                    ds_prev ? ds_prev->ds_phys->ds_creation_txg : 0);
 
-               /*
-                * Transfer to our deadlist (which will become next's
-                * new deadlist) any entries from next's current
-                * deadlist which were born before prev, and free the
-                * other entries.
-                *
-                * XXX we're doing this long task with the config lock held
-                */
-               while (bplist_iterate(&ds_next->ds_deadlist, &itor, &bp) == 0) {
-                       if (bp.blk_birth <= ds->ds_phys->ds_prev_snap_txg) {
-                               VERIFY(0 == bplist_enqueue(&ds->ds_deadlist,
-                                   &bp, tx));
-                               if (ds_prev && !after_branch_point &&
-                                   bp.blk_birth >
-                                   ds_prev->ds_phys->ds_prev_snap_txg) {
-                                       ds_prev->ds_phys->ds_unique_bytes +=
-                                           bp_get_dasize(dp->dp_spa, &bp);
-                               }
-                       } else {
-                               used += bp_get_dasize(dp->dp_spa, &bp);
-                               compressed += BP_GET_PSIZE(&bp);
-                               uncompressed += BP_GET_UCSIZE(&bp);
-                               /* XXX check return value? */
-                               (void) dsl_free(zio, dp, tx->tx_txg,
-                                   &bp, NULL, NULL, ARC_NOWAIT);
-                       }
-               }
 
-               ASSERT3U(used, ==, ds->ds_phys->ds_unique_bytes);
+               if (ds_next->ds_deadlist.dl_oldfmt) {
+                       process_old_deadlist(ds, ds_prev, ds_next,
+                           after_branch_point, tx);
+               } else {
+                       /* Adjust prev's unique space. */
+                       if (ds_prev && !after_branch_point) {
+                               dsl_deadlist_space_range(&ds_next->ds_deadlist,
+                                   ds_prev->ds_phys->ds_prev_snap_txg,
+                                   ds->ds_phys->ds_prev_snap_txg,
+                                   &used, &comp, &uncomp);
+                               ds_prev->ds_phys->ds_unique_bytes += used;
+                       }
 
-               /* change snapused */
-               dsl_dir_diduse_space(ds->ds_dir, DD_USED_SNAP,
-                   -used, -compressed, -uncompressed, tx);
+                       /* Adjust snapused. */
+                       dsl_deadlist_space_range(&ds_next->ds_deadlist,
+                           ds->ds_phys->ds_prev_snap_txg, UINT64_MAX,
+                           &used, &comp, &uncomp);
+                       dsl_dir_diduse_space(ds->ds_dir, DD_USED_SNAP,
+                           -used, -comp, -uncomp, tx);
+
+                       /* Move blocks to be freed to pool's free list. */
+                       dsl_deadlist_move_bpobj(&ds_next->ds_deadlist,
+                           &dp->dp_free_bpobj, ds->ds_phys->ds_prev_snap_txg,
+                           tx);
+                       dsl_dir_diduse_space(tx->tx_pool->dp_free_dir,
+                           DD_USED_HEAD, used, comp, uncomp, tx);
+
+                       /* Merge our deadlist into next's and free it. */
+                       dsl_deadlist_merge(&ds_next->ds_deadlist,
+                           ds->ds_phys->ds_deadlist_obj, tx);
+               }
+               dsl_deadlist_close(&ds->ds_deadlist);
+               dsl_deadlist_free(mos, ds->ds_phys->ds_deadlist_obj, tx);
 
-               /* free next's deadlist */
-               bplist_close(&ds_next->ds_deadlist);
-               bplist_destroy(mos, ds_next->ds_phys->ds_deadlist_obj, tx);
+               /* Collapse range in clone heads */
+               dsl_dataset_remove_clones_key(ds,
+                   ds->ds_phys->ds_creation_txg, tx);
 
-               /* set next's deadlist to our deadlist */
-               bplist_close(&ds->ds_deadlist);
-               ds_next->ds_phys->ds_deadlist_obj =
-                   ds->ds_phys->ds_deadlist_obj;
-               VERIFY(0 == bplist_open(&ds_next->ds_deadlist, mos,
-                   ds_next->ds_phys->ds_deadlist_obj));
-               ds->ds_phys->ds_deadlist_obj = 0;
+               if (dsl_dataset_is_snapshot(ds_next)) {
+                       dsl_dataset_t *ds_nextnext;
+                       dsl_dataset_t *hds;
 
-               if (ds_next->ds_phys->ds_next_snap_obj != 0) {
                        /*
                         * Update next's unique to include blocks which
                         * were previously shared by only this snapshot
@@ -1605,25 +1809,26 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
                         * died after the next snap and before the one
                         * after that (ie. be on the snap after next's
                         * deadlist).
-                        *
-                        * XXX we're doing this long task with the
-                        * config lock held
                         */
-                       dsl_dataset_t *ds_after_next;
-                       uint64_t space;
-
                        VERIFY(0 == dsl_dataset_hold_obj(dp,
                            ds_next->ds_phys->ds_next_snap_obj,
-                           FTAG, &ds_after_next));
-
-                       VERIFY(0 ==
-                           bplist_space_birthrange(&ds_after_next->ds_deadlist,
+                           FTAG, &ds_nextnext));
+                       dsl_deadlist_space_range(&ds_nextnext->ds_deadlist,
                            ds->ds_phys->ds_prev_snap_txg,
-                           ds->ds_phys->ds_creation_txg, &space));
-                       ds_next->ds_phys->ds_unique_bytes += space;
-
-                       dsl_dataset_rele(ds_after_next, FTAG);
+                           ds->ds_phys->ds_creation_txg,
+                           &used, &comp, &uncomp);
+                       ds_next->ds_phys->ds_unique_bytes += used;
+                       dsl_dataset_rele(ds_nextnext, FTAG);
                        ASSERT3P(ds_next->ds_prev, ==, NULL);
+
+                       /* Collapse range in this head. */
+                       VERIFY3U(0, ==, dsl_dataset_hold_obj(dp,
+                           ds->ds_dir->dd_phys->dd_head_dataset_obj,
+                           FTAG, &hds));
+                       dsl_deadlist_remove_key(&hds->ds_deadlist,
+                           ds->ds_phys->ds_creation_txg, tx);
+                       dsl_dataset_rele(hds, FTAG);
+
                } else {
                        ASSERT3P(ds_next->ds_prev, ==, ds);
                        dsl_dataset_drop_ref(ds_next->ds_prev, ds_next);
@@ -1655,38 +1860,77 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
                }
                dsl_dataset_rele(ds_next, FTAG);
        } else {
+               zfeature_info_t *async_destroy =
+                   &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY];
+               objset_t *os;
+
                /*
                 * There's no next snapshot, so this is a head dataset.
                 * Destroy the deadlist.  Unless it's a clone, the
                 * deadlist should be empty.  (If it's a clone, it's
                 * safe to ignore the deadlist contents.)
                 */
-               struct killarg ka;
-
-               ASSERT(after_branch_point || bplist_empty(&ds->ds_deadlist));
-               bplist_close(&ds->ds_deadlist);
-               bplist_destroy(mos, ds->ds_phys->ds_deadlist_obj, tx);
+               dsl_deadlist_close(&ds->ds_deadlist);
+               dsl_deadlist_free(mos, ds->ds_phys->ds_deadlist_obj, tx);
                ds->ds_phys->ds_deadlist_obj = 0;
 
-               /*
-                * Free everything that we point to (that's born after
-                * the previous snapshot, if we are a clone)
-                *
-                * NB: this should be very quick, because we already
-                * freed all the objects in open context.
-                */
-               ka.ds = ds;
-               ka.zio = zio;
-               ka.tx = tx;
-               err = traverse_dataset(ds, ds->ds_phys->ds_prev_snap_txg,
-                   TRAVERSE_POST, kill_blkptr, &ka);
-               ASSERT3U(err, ==, 0);
-               ASSERT(!DS_UNIQUE_IS_ACCURATE(ds) ||
-                   ds->ds_phys->ds_unique_bytes == 0);
+               VERIFY3U(0, ==, dmu_objset_from_ds(ds, &os));
+
+               if (!spa_feature_is_enabled(dp->dp_spa, async_destroy)) {
+                       err = old_synchronous_dataset_destroy(ds, tx);
+               } else {
+                       /*
+                        * Move the bptree into the pool's list of trees to
+                        * clean up and update space accounting information.
+                        */
+                       uint64_t used, comp, uncomp;
+
+                       zil_destroy_sync(dmu_objset_zil(os), tx);
+
+                       if (!spa_feature_is_active(dp->dp_spa, async_destroy)) {
+                               spa_feature_incr(dp->dp_spa, async_destroy, tx);
+                               dp->dp_bptree_obj = bptree_alloc(mos, tx);
+                               VERIFY(zap_add(mos,
+                                   DMU_POOL_DIRECTORY_OBJECT,
+                                   DMU_POOL_BPTREE_OBJ, sizeof (uint64_t), 1,
+                                   &dp->dp_bptree_obj, tx) == 0);
+                       }
+
+                       used = ds->ds_dir->dd_phys->dd_used_bytes;
+                       comp = ds->ds_dir->dd_phys->dd_compressed_bytes;
+                       uncomp = ds->ds_dir->dd_phys->dd_uncompressed_bytes;
+
+                       ASSERT(!DS_UNIQUE_IS_ACCURATE(ds) ||
+                           ds->ds_phys->ds_unique_bytes == used);
+
+                       bptree_add(mos, dp->dp_bptree_obj,
+                           &ds->ds_phys->ds_bp, ds->ds_phys->ds_prev_snap_txg,
+                           used, comp, uncomp, tx);
+                       dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD,
+                           -used, -comp, -uncomp, tx);
+                       dsl_dir_diduse_space(dp->dp_free_dir, DD_USED_HEAD,
+                           used, comp, uncomp, tx);
+               }
+
+               if (ds->ds_prev != NULL) {
+                       if (spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
+                               VERIFY3U(0, ==, zap_remove_int(mos,
+                                   ds->ds_prev->ds_dir->dd_phys->dd_clones,
+                                   ds->ds_object, tx));
+                       }
+                       dsl_dataset_rele(ds->ds_prev, ds);
+                       ds->ds_prev = ds_prev = NULL;
+               }
        }
 
-       err = zio_wait(zio);
-       ASSERT3U(err, ==, 0);
+       /*
+        * This must be done after the dsl_traverse(), because it will
+        * re-open the objset.
+        */
+       if (ds->ds_objset) {
+               dmu_objset_evict(ds->ds_objset);
+               ds->ds_objset = NULL;
+       }
 
        if (ds->ds_dir->dd_phys->dd_head_dataset_obj == ds->ds_object) {
                /* Erase the link in the dir */
@@ -1708,7 +1952,7 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
 
                        err = dsl_dataset_snap_lookup(ds_head,
                            ds->ds_snapname, &val);
-                       ASSERT3U(err, ==, 0);
+                       ASSERT0(err);
                        ASSERT3U(val, ==, obj);
                }
 #endif
@@ -1721,11 +1965,11 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
                dsl_dataset_rele(ds_prev, FTAG);
 
        spa_prop_clear_bootfs(dp->dp_spa, ds->ds_object, tx);
-       spa_history_internal_log(LOG_DS_DESTROY, dp->dp_spa, tx,
-           cr, "dataset = %llu", ds->ds_object);
+       spa_history_log_internal(LOG_DS_DESTROY, dp->dp_spa, tx,
+           "dataset = %llu", ds->ds_object);
 
        if (ds->ds_phys->ds_next_clones_obj != 0) {
-               uint64_t count;
+               ASSERTV(uint64_t count);
                ASSERT(0 == zap_count(mos,
                    ds->ds_phys->ds_next_clones_obj, &count) && count == 0);
                VERIFY(0 == dmu_object_free(mos,
@@ -1733,10 +1977,22 @@ dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
        }
        if (ds->ds_phys->ds_props_obj != 0)
                VERIFY(0 == zap_destroy(mos, ds->ds_phys->ds_props_obj, tx));
+       if (ds->ds_phys->ds_userrefs_obj != 0)
+               VERIFY(0 == zap_destroy(mos, ds->ds_phys->ds_userrefs_obj, tx));
        dsl_dir_close(ds->ds_dir, ds);
        ds->ds_dir = NULL;
        dsl_dataset_drain_refs(ds, tag);
        VERIFY(0 == dmu_object_free(mos, obj, tx));
+
+       if (dsda->rm_origin) {
+               /*
+                * Remove the origin of the clone we just destroyed.
+                */
+               struct dsl_ds_destroyarg ndsda = {0};
+
+               ndsda.ds = dsda->rm_origin;
+               dsl_dataset_destroy_sync(&ndsda, tag, tx);
+       }
 }
 
 static int
@@ -1752,8 +2008,9 @@ dsl_dataset_snapshot_reserve_space(dsl_dataset_t *ds, dmu_tx_t *tx)
         * owned by the snapshot dataset must be accommodated by space
         * outside of the reservation.
         */
-       asize = MIN(dsl_dataset_unique(ds), ds->ds_reserved);
-       if (asize > dsl_dir_space_available(ds->ds_dir, NULL, 0, FALSE))
+       ASSERT(ds->ds_reserved == 0 || DS_UNIQUE_IS_ACCURATE(ds));
+       asize = MIN(ds->ds_phys->ds_unique_bytes, ds->ds_reserved);
+       if (asize > dsl_dir_space_available(ds->ds_dir, NULL, 0, TRUE))
                return (ENOSPC);
 
        /*
@@ -1766,7 +2023,6 @@ dsl_dataset_snapshot_reserve_space(dsl_dataset_t *ds, dmu_tx_t *tx)
        return (0);
 }
 
-/* ARGSUSED */
 int
 dsl_dataset_snapshot_check(void *arg1, void *arg2, dmu_tx_t *tx)
 {
@@ -1807,7 +2063,7 @@ dsl_dataset_snapshot_check(void *arg1, void *arg2, dmu_tx_t *tx)
 }
 
 void
-dsl_dataset_snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
+dsl_dataset_snapshot_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
        const char *snapname = arg2;
@@ -1845,7 +2101,7 @@ dsl_dataset_snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
        dsphys->ds_creation_time = gethrestime_sec();
        dsphys->ds_creation_txg = crtxg;
        dsphys->ds_deadlist_obj = ds->ds_phys->ds_deadlist_obj;
-       dsphys->ds_used_bytes = ds->ds_phys->ds_used_bytes;
+       dsphys->ds_referenced_bytes = ds->ds_phys->ds_referenced_bytes;
        dsphys->ds_compressed_bytes = ds->ds_phys->ds_compressed_bytes;
        dsphys->ds_uncompressed_bytes = ds->ds_phys->ds_uncompressed_bytes;
        dsphys->ds_flags = ds->ds_phys->ds_flags;
@@ -1865,8 +2121,8 @@ dsl_dataset_snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
                            ds->ds_prev->ds_phys->ds_creation_txg);
                        ds->ds_prev->ds_phys->ds_next_snap_obj = dsobj;
                } else if (next_clones_obj != 0) {
-                       VERIFY3U(0, ==, zap_remove_int(mos,
-                           next_clones_obj, dsphys->ds_next_snap_obj, tx));
+                       remove_from_next_clones(ds->ds_prev,
+                           dsphys->ds_next_snap_obj, tx);
                        VERIFY3U(0, ==, zap_add_int(mos,
                            next_clones_obj, dsobj, tx));
                }
@@ -1878,25 +2134,31 @@ dsl_dataset_snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
         * since our unique space is going to zero.
         */
        if (ds->ds_reserved) {
-               int64_t add = MIN(dsl_dataset_unique(ds), ds->ds_reserved);
+               int64_t delta;
+               ASSERT(DS_UNIQUE_IS_ACCURATE(ds));
+               delta = MIN(ds->ds_phys->ds_unique_bytes, ds->ds_reserved);
                dsl_dir_diduse_space(ds->ds_dir, DD_USED_REFRSRV,
-                   add, 0, 0, tx);
+                   delta, 0, 0, tx);
        }
 
-       bplist_close(&ds->ds_deadlist);
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
+       zfs_dbgmsg("taking snapshot %s@%s/%llu; newkey=%llu",
+           ds->ds_dir->dd_myname, snapname, dsobj,
+           ds->ds_phys->ds_prev_snap_txg);
+       ds->ds_phys->ds_deadlist_obj = dsl_deadlist_clone(&ds->ds_deadlist,
+           UINT64_MAX, ds->ds_phys->ds_prev_snap_obj, tx);
+       dsl_deadlist_close(&ds->ds_deadlist);
+       dsl_deadlist_open(&ds->ds_deadlist, mos, ds->ds_phys->ds_deadlist_obj);
+       dsl_deadlist_add_key(&ds->ds_deadlist,
+           ds->ds_phys->ds_prev_snap_txg, tx);
+
        ASSERT3U(ds->ds_phys->ds_prev_snap_txg, <, tx->tx_txg);
        ds->ds_phys->ds_prev_snap_obj = dsobj;
        ds->ds_phys->ds_prev_snap_txg = crtxg;
        ds->ds_phys->ds_unique_bytes = 0;
        if (spa_version(dp->dp_spa) >= SPA_VERSION_UNIQUE_ACCURATE)
                ds->ds_phys->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;
-       ds->ds_phys->ds_deadlist_obj =
-           bplist_create(mos, DSL_DEADLIST_BLOCKSIZE, tx);
-       VERIFY(0 == bplist_open(&ds->ds_deadlist, mos,
-           ds->ds_phys->ds_deadlist_obj));
 
-       dprintf("snap '%s' -> obj %llu\n", snapname, dsobj);
        err = zap_add(mos, ds->ds_phys->ds_snapnames_zapobj,
            snapname, 8, 1, &dsobj, tx);
        ASSERT(err == 0);
@@ -1906,9 +2168,11 @@ dsl_dataset_snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
        VERIFY(0 == dsl_dataset_get_ref(dp,
            ds->ds_phys->ds_prev_snap_obj, ds, &ds->ds_prev));
 
-       dsl_pool_ds_snapshotted(ds, tx);
+       dsl_scan_ds_snapshotted(ds, tx);
 
-       spa_history_internal_log(LOG_DS_SNAPSHOT, dp->dp_spa, tx, cr,
+       dsl_dir_snap_cmtime_update(ds->ds_dir);
+
+       spa_history_log_internal(LOG_DS_SNAPSHOT, dp->dp_spa, tx,
            "dataset = %llu", dsobj);
 }
 
@@ -1916,7 +2180,7 @@ void
 dsl_dataset_sync(dsl_dataset_t *ds, zio_t *zio, dmu_tx_t *tx)
 {
        ASSERT(dmu_tx_is_syncing(tx));
-       ASSERT(ds->ds_user_ptr != NULL);
+       ASSERT(ds->ds_objset != NULL);
        ASSERT(ds->ds_phys->ds_next_snap_obj == 0);
 
        /*
@@ -1926,14 +2190,74 @@ dsl_dataset_sync(dsl_dataset_t *ds, zio_t *zio, dmu_tx_t *tx)
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
        ds->ds_phys->ds_fsid_guid = ds->ds_fsid_guid;
 
-       dsl_dir_dirty(ds->ds_dir, tx);
-       dmu_objset_sync(ds->ds_user_ptr, zio, tx);
+       dmu_objset_sync(ds->ds_objset, zio, tx);
+}
+
+static void
+get_clones_stat(dsl_dataset_t *ds, nvlist_t *nv)
+{
+       uint64_t count = 0;
+       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       zap_cursor_t zc;
+       zap_attribute_t za;
+       nvlist_t *propval;
+       nvlist_t *val;
+
+       rw_enter(&ds->ds_dir->dd_pool->dp_config_rwlock, RW_READER);
+       VERIFY(nvlist_alloc(&propval, NV_UNIQUE_NAME, KM_SLEEP) == 0);
+       VERIFY(nvlist_alloc(&val, NV_UNIQUE_NAME, KM_SLEEP) == 0);
+
+       /*
+        * There may me 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 (ds->ds_phys->ds_next_clones_obj != 0) {
+               ASSERT3U(0, ==, zap_count(mos, ds->ds_phys->ds_next_clones_obj,
+                   &count));
+       }
+       if (count != ds->ds_phys->ds_num_children - 1) {
+               goto fail;
+       }
+       for (zap_cursor_init(&zc, mos, ds->ds_phys->ds_next_clones_obj);
+           zap_cursor_retrieve(&zc, &za) == 0;
+           zap_cursor_advance(&zc)) {
+               dsl_dataset_t *clone;
+               char buf[ZFS_MAXNAMELEN];
+               /*
+                * Even though we hold the dp_config_rwlock, the dataset
+                * may fail to open, returning ENOENT.  If there is a
+                * thread concurrently attempting to destroy this
+                * dataset, it will have the ds_rwlock held for
+                * RW_WRITER.  Our call to dsl_dataset_hold_obj() ->
+                * dsl_dataset_hold_ref() will fail its
+                * rw_tryenter(&ds->ds_rwlock, RW_READER), drop the
+                * dp_config_rwlock, and wait for the destroy progress
+                * and signal ds_exclusive_cv.  If the destroy was
+                * successful, we will see that
+                * DSL_DATASET_IS_DESTROYED(), and return ENOENT.
+                */
+               if (dsl_dataset_hold_obj(ds->ds_dir->dd_pool,
+                   za.za_first_integer, FTAG, &clone) != 0)
+                       continue;
+               dsl_dir_name(clone->ds_dir, buf);
+               VERIFY(nvlist_add_boolean(val, buf) == 0);
+               dsl_dataset_rele(clone, FTAG);
+       }
+       zap_cursor_fini(&zc);
+       VERIFY(nvlist_add_nvlist(propval, ZPROP_VALUE, val) == 0);
+       VERIFY(nvlist_add_nvlist(nv, zfs_prop_to_name(ZFS_PROP_CLONES),
+           propval) == 0);
+fail:
+       nvlist_free(val);
+       nvlist_free(propval);
+       rw_exit(&ds->ds_dir->dd_pool->dp_config_rwlock);
 }
 
 void
 dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
 {
-       uint64_t refd, avail, uobjs, aobjs;
+       uint64_t refd, avail, uobjs, aobjs, ratio;
 
        dsl_dir_stats(ds->ds_dir, nv);
 
@@ -1951,6 +2275,40 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
            ds->ds_reserved);
        dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_GUID,
            ds->ds_phys->ds_guid);
+       dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_UNIQUE,
+           ds->ds_phys->ds_unique_bytes);
+       dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_OBJSETID,
+           ds->ds_object);
+       dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USERREFS,
+           ds->ds_userrefs);
+       dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_DEFER_DESTROY,
+           DS_IS_DEFER_DESTROY(ds) ? 1 : 0);
+
+       if (ds->ds_phys->ds_prev_snap_obj != 0) {
+               uint64_t written, comp, uncomp;
+               dsl_pool_t *dp = ds->ds_dir->dd_pool;
+               dsl_dataset_t *prev;
+               int err;
+
+               rw_enter(&dp->dp_config_rwlock, RW_READER);
+               err = dsl_dataset_hold_obj(dp,
+                   ds->ds_phys->ds_prev_snap_obj, FTAG, &prev);
+               rw_exit(&dp->dp_config_rwlock);
+               if (err == 0) {
+                       err = dsl_dataset_space_written(prev, ds, &written,
+                           &comp, &uncomp);
+                       dsl_dataset_rele(prev, FTAG);
+                       if (err == 0) {
+                               dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_WRITTEN,
+                                   written);
+                       }
+               }
+       }
+
+       ratio = ds->ds_phys->ds_compressed_bytes == 0 ? 100 :
+           (ds->ds_phys->ds_uncompressed_bytes * 100 /
+           ds->ds_phys->ds_compressed_bytes);
+       dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFRATIO, ratio);
 
        if (ds->ds_phys->ds_next_snap_obj) {
                /*
@@ -1959,10 +2317,9 @@ dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
                 */
                dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USED,
                    ds->ds_phys->ds_unique_bytes);
-               dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_COMPRESSRATIO,
-                   ds->ds_phys->ds_compressed_bytes == 0 ? 100 :
-                   (ds->ds_phys->ds_uncompressed_bytes * 100 /
-                   ds->ds_phys->ds_compressed_bytes));
+               dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_COMPRESSRATIO, ratio);
+
+               get_clones_stat(ds, nv);
        }
 }
 
@@ -2006,7 +2363,7 @@ dsl_dataset_space(dsl_dataset_t *ds,
     uint64_t *refdbytesp, uint64_t *availbytesp,
     uint64_t *usedobjsp, uint64_t *availobjsp)
 {
-       *refdbytesp = ds->ds_phys->ds_used_bytes;
+       *refdbytesp = ds->ds_phys->ds_referenced_bytes;
        *availbytesp = dsl_dir_space_available(ds->ds_dir, NULL, 0, TRUE);
        if (ds->ds_reserved > ds->ds_phys->ds_unique_bytes)
                *availbytesp += ds->ds_reserved - ds->ds_phys->ds_unique_bytes;
@@ -2027,15 +2384,28 @@ dsl_dataset_space(dsl_dataset_t *ds,
 boolean_t
 dsl_dataset_modified_since_lastsnap(dsl_dataset_t *ds)
 {
-       dsl_pool_t *dp = ds->ds_dir->dd_pool;
+       ASSERTV(dsl_pool_t *dp = ds->ds_dir->dd_pool);
 
        ASSERT(RW_LOCK_HELD(&dp->dp_config_rwlock) ||
            dsl_pool_sync_context(dp));
        if (ds->ds_prev == NULL)
                return (B_FALSE);
        if (ds->ds_phys->ds_bp.blk_birth >
-           ds->ds_prev->ds_phys->ds_creation_txg)
-               return (B_TRUE);
+           ds->ds_prev->ds_phys->ds_creation_txg) {
+               objset_t *os, *os_prev;
+               /*
+                * 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(ds->ds_prev, &os_prev) != 0)
+                       return (B_TRUE);
+               return (bcmp(&os->os_phys->os_meta_dnode,
+                   &os_prev->os_phys->os_meta_dnode,
+                   sizeof (os->os_phys->os_meta_dnode)) != 0);
+       }
        return (B_FALSE);
 }
 
@@ -2072,8 +2442,7 @@ dsl_dataset_snapshot_rename_check(void *arg1, void *arg2, dmu_tx_t *tx)
 }
 
 static void
-dsl_dataset_snapshot_rename_sync(void *arg1, void *arg2,
-    cred_t *cr, dmu_tx_t *tx)
+dsl_dataset_snapshot_rename_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
        const char *newsnapname = arg2;
@@ -2089,16 +2458,16 @@ dsl_dataset_snapshot_rename_sync(void *arg1, void *arg2,
 
        VERIFY(0 == dsl_dataset_get_snapname(ds));
        err = dsl_dataset_snap_remove(hds, ds->ds_snapname, tx);
-       ASSERT3U(err, ==, 0);
+       ASSERT0(err);
        mutex_enter(&ds->ds_lock);
        (void) strcpy(ds->ds_snapname, newsnapname);
        mutex_exit(&ds->ds_lock);
        err = zap_add(mos, hds->ds_phys->ds_snapnames_zapobj,
            ds->ds_snapname, 8, 1, &ds->ds_object, tx);
-       ASSERT3U(err, ==, 0);
+       ASSERT0(err);
 
-       spa_history_internal_log(LOG_DS_RENAME, dd->dd_pool->dp_spa, tx,
-           cr, "dataset = %llu", ds->ds_object);
+       spa_history_log_internal(LOG_DS_RENAME, dd->dd_pool->dp_spa, tx,
+           "dataset = %llu", ds->ds_object);
        dsl_dataset_rele(hds, FTAG);
 }
 
@@ -2110,43 +2479,36 @@ struct renamesnaparg {
 };
 
 static int
-dsl_snapshot_rename_one(char *name, void *arg)
+dsl_snapshot_rename_one(const char *name, void *arg)
 {
        struct renamesnaparg *ra = arg;
        dsl_dataset_t *ds = NULL;
-       char *cp;
+       char *snapname;
        int err;
 
-       cp = name + strlen(name);
-       *cp = '@';
-       (void) strcpy(cp + 1, ra->oldsnap);
+       snapname = kmem_asprintf("%s@%s", name, ra->oldsnap);
+       (void) strlcpy(ra->failed, snapname, sizeof (ra->failed));
 
        /*
         * For recursive snapshot renames the parent won't be changing
         * so we just pass name for both the to/from argument.
         */
-       err = zfs_secpolicy_rename_perms(name, name, CRED());
-       if (err == ENOENT) {
-               return (0);
-       } else if (err) {
-               (void) strcpy(ra->failed, name);
-               return (err);
+       err = zfs_secpolicy_rename_perms(snapname, snapname, CRED());
+       if (err != 0) {
+               strfree(snapname);
+               return (err == ENOENT ? 0 : err);
        }
 
 #ifdef _KERNEL
        /*
         * For all filesystems undergoing rename, we'll need to unmount it.
         */
-       (void) zfs_unmount_snap(name, NULL);
+       (void) zfs_unmount_snap(snapname, NULL);
 #endif
-       err = dsl_dataset_hold(name, ra->dstg, &ds);
-       *cp = '\0';
-       if (err == ENOENT) {
-               return (0);
-       } else if (err) {
-               (void) strcpy(ra->failed, name);
-               return (err);
-       }
+       err = dsl_dataset_hold(snapname, ra->dstg, &ds);
+       strfree(snapname);
+       if (err != 0)
+               return (err == ENOENT ? 0 : err);
 
        dsl_sync_task_create(ra->dstg, dsl_dataset_snapshot_rename_check,
            dsl_dataset_snapshot_rename_sync, ds, ra->newsnap, 0);
@@ -2162,7 +2524,7 @@ dsl_recursive_rename(char *oldname, const char *newname)
        dsl_sync_task_t *dst;
        spa_t *spa;
        char *cp, *fsname = spa_strdup(oldname);
-       int len = strlen(oldname);
+       int len = strlen(oldname) + 1;
 
        /* truncate the snapshot name to get the fsname */
        cp = strchr(fsname, '@');
@@ -2170,7 +2532,7 @@ dsl_recursive_rename(char *oldname, const char *newname)
 
        err = spa_open(fsname, &spa, FTAG);
        if (err) {
-               kmem_free(fsname, len + 1);
+               kmem_free(fsname, len);
                return (err);
        }
        ra = kmem_alloc(sizeof (struct renamesnaparg), KM_SLEEP);
@@ -2182,7 +2544,7 @@ dsl_recursive_rename(char *oldname, const char *newname)
 
        err = dmu_objset_find(fsname, dsl_snapshot_rename_one, ra,
            DS_FIND_CHILDREN);
-       kmem_free(fsname, len + 1);
+       kmem_free(fsname, len);
 
        if (err == 0) {
                err = dsl_sync_task_group_wait(ra->dstg);
@@ -2193,14 +2555,15 @@ dsl_recursive_rename(char *oldname, const char *newname)
                dsl_dataset_t *ds = dst->dst_arg1;
                if (dst->dst_err) {
                        dsl_dir_name(ds->ds_dir, ra->failed);
-                       (void) strcat(ra->failed, "@");
-                       (void) strcat(ra->failed, ra->newsnap);
+                       (void) strlcat(ra->failed, "@", sizeof (ra->failed));
+                       (void) strlcat(ra->failed, ra->newsnap,
+                           sizeof (ra->failed));
                }
                dsl_dataset_rele(ds, ra->dstg);
        }
 
        if (err)
-               (void) strcpy(oldname, ra->failed);
+               (void) strlcpy(oldname, ra->failed, sizeof (ra->failed));
 
        dsl_sync_task_group_destroy(ra->dstg);
        kmem_free(ra, sizeof (struct renamesnaparg));
@@ -2209,7 +2572,7 @@ dsl_recursive_rename(char *oldname, const char *newname)
 }
 
 static int
-dsl_valid_rename(char *oldname, void *arg)
+dsl_valid_rename(const char *oldname, void *arg)
 {
        int delta = *(int *)arg;
 
@@ -2231,12 +2594,7 @@ dsl_dataset_rename(char *oldname, const char *newname, boolean_t recursive)
        err = dsl_dir_open(oldname, FTAG, &dd, &tail);
        if (err)
                return (err);
-       /*
-        * If there are more than 2 references there may be holds
-        * hanging around that haven't been cleared out yet.
-        */
-       if (dmu_buf_refcount(dd->dd_dbuf) > 2)
-               txg_wait_synced(dd->dd_pool, 0);
+
        if (tail == NULL) {
                int delta = strlen(newname) - strlen(oldname);
 
@@ -2245,13 +2603,14 @@ dsl_dataset_rename(char *oldname, const char *newname, boolean_t recursive)
                        err = dmu_objset_find(oldname, dsl_valid_rename,
                            &delta, DS_FIND_CHILDREN | DS_FIND_SNAPSHOTS);
 
-               if (!err)
+               if (err == 0)
                        err = dsl_dir_rename(dd, newname);
                dsl_dir_close(dd, FTAG);
                return (err);
        }
+
        if (tail[0] != '@') {
-               /* the name ended in a nonexistant component */
+               /* the name ended in a nonexistent component */
                dsl_dir_close(dd, FTAG);
                return (ENOENT);
        }
@@ -2290,13 +2649,13 @@ struct promotenode {
 
 struct promotearg {
        list_t shared_snaps, origin_snaps, clone_snaps;
-       dsl_dataset_t *origin_origin, *origin_head;
+       dsl_dataset_t *origin_origin;
        uint64_t used, comp, uncomp, unique, cloneusedsnap, originusedsnap;
+       char *err_ds;
 };
 
 static int snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep);
 
-/* ARGSUSED */
 static int
 dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
 {
@@ -2305,6 +2664,7 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
        struct promotenode *snap = list_head(&pa->shared_snaps);
        dsl_dataset_t *origin_ds = snap->ds;
        int err;
+       uint64_t unused;
 
        /* Check that it is a real clone */
        if (!dsl_dir_is_clone(hds->ds_dir))
@@ -2320,10 +2680,9 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
        /* compute origin's new unique space */
        snap = list_tail(&pa->clone_snaps);
        ASSERT3U(snap->ds->ds_phys->ds_prev_snap_obj, ==, origin_ds->ds_object);
-       err = bplist_space_birthrange(&snap->ds->ds_deadlist,
-           origin_ds->ds_phys->ds_prev_snap_txg, UINT64_MAX, &pa->unique);
-       if (err)
-               return (err);
+       dsl_deadlist_space_range(&snap->ds->ds_deadlist,
+           origin_ds->ds_phys->ds_prev_snap_txg, UINT64_MAX,
+           &pa->unique, &unused, &unused);
 
        /*
         * Walk the snapshots that we are moving
@@ -2340,7 +2699,7 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
         * Note however, if we stop before we reach the ORIGIN we get:
         * uN + kN + kN-1 + ... + kM - uM-1
         */
-       pa->used = origin_ds->ds_phys->ds_used_bytes;
+       pa->used = origin_ds->ds_phys->ds_referenced_bytes;
        pa->comp = origin_ds->ds_phys->ds_compressed_bytes;
        pa->uncomp = origin_ds->ds_phys->ds_uncompressed_bytes;
        for (snap = list_head(&pa->shared_snaps); snap;
@@ -2351,18 +2710,19 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
                /* Check that the snapshot name does not conflict */
                VERIFY(0 == dsl_dataset_get_snapname(ds));
                err = dsl_dataset_snap_lookup(hds, ds->ds_snapname, &val);
-               if (err == 0)
-                       return (EEXIST);
+               if (err == 0) {
+                       err = EEXIST;
+                       goto out;
+               }
                if (err != ENOENT)
-                       return (err);
+                       goto out;
 
                /* The very first snapshot does not have a deadlist */
                if (ds->ds_phys->ds_prev_snap_obj == 0)
                        continue;
 
-               if (err = bplist_space(&ds->ds_deadlist,
-                   &dlused, &dlcomp, &dluncomp))
-                       return (err);
+               dsl_deadlist_space(&ds->ds_deadlist,
+                   &dlused, &dlcomp, &dluncomp);
                pa->used += dlused;
                pa->comp += dlcomp;
                pa->uncomp += dluncomp;
@@ -2373,7 +2733,7 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
         * so we need to subtract out the clone origin's used space.
         */
        if (pa->origin_origin) {
-               pa->used -= pa->origin_origin->ds_phys->ds_used_bytes;
+               pa->used -= pa->origin_origin->ds_phys->ds_referenced_bytes;
                pa->comp -= pa->origin_origin->ds_phys->ds_compressed_bytes;
                pa->uncomp -= pa->origin_origin->ds_phys->ds_uncompressed_bytes;
        }
@@ -2395,19 +2755,19 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
 
                /*
                 * Note, typically this will not be a clone of a clone,
-                * so snap->ds->ds_origin_txg will be < TXG_INITIAL, so
-                * these snaplist_space() -> bplist_space_birthrange()
+                * 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(&pa->origin_snaps);
                err = snaplist_space(&pa->shared_snaps,
-                   snap->ds->ds_origin_txg, &pa->cloneusedsnap);
+                   snap->ds->ds_dir->dd_origin_txg, &pa->cloneusedsnap);
                if (err)
                        return (err);
 
                err = snaplist_space(&pa->clone_snaps,
-                   snap->ds->ds_origin_txg, &space);
+                   snap->ds->ds_dir->dd_origin_txg, &space);
                if (err)
                        return (err);
                pa->cloneusedsnap += space;
@@ -2420,10 +2780,13 @@ dsl_dataset_promote_check(void *arg1, void *arg2, dmu_tx_t *tx)
        }
 
        return (0);
-}
+out:
+       pa->err_ds =  snap->ds->ds_snapname;
+       return (err);
+}
 
 static void
-dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
+dsl_dataset_promote_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *hds = arg1;
        struct promotearg *pa = arg2;
@@ -2457,9 +2820,7 @@ dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
 
        /* change the origin's next clone */
        if (origin_ds->ds_phys->ds_next_clones_obj) {
-               VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
-                   origin_ds->ds_phys->ds_next_clones_obj,
-                   origin_ds->ds_phys->ds_next_snap_obj, tx));
+               remove_from_next_clones(origin_ds, snap->ds->ds_object, tx);
                VERIFY3U(0, ==, zap_add_int(dp->dp_meta_objset,
                    origin_ds->ds_phys->ds_next_clones_obj,
                    oldnext_obj, tx));
@@ -2469,10 +2830,31 @@ dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
        dmu_buf_will_dirty(dd->dd_dbuf, tx);
        ASSERT3U(dd->dd_phys->dd_origin_obj, ==, origin_ds->ds_object);
        dd->dd_phys->dd_origin_obj = odd->dd_phys->dd_origin_obj;
-       hds->ds_origin_txg = origin_head->ds_origin_txg;
+       dd->dd_origin_txg = origin_head->ds_dir->dd_origin_txg;
        dmu_buf_will_dirty(odd->dd_dbuf, tx);
        odd->dd_phys->dd_origin_obj = origin_ds->ds_object;
-       origin_head->ds_origin_txg = origin_ds->ds_phys->ds_creation_txg;
+       origin_head->ds_dir->dd_origin_txg =
+           origin_ds->ds_phys->ds_creation_txg;
+
+       /* change dd_clone entries */
+       if (spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
+               VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
+                   odd->dd_phys->dd_clones, hds->ds_object, tx));
+               VERIFY3U(0, ==, zap_add_int(dp->dp_meta_objset,
+                   pa->origin_origin->ds_dir->dd_phys->dd_clones,
+                   hds->ds_object, tx));
+
+               VERIFY3U(0, ==, zap_remove_int(dp->dp_meta_objset,
+                   pa->origin_origin->ds_dir->dd_phys->dd_clones,
+                   origin_head->ds_object, tx));
+               if (dd->dd_phys->dd_clones == 0) {
+                       dd->dd_phys->dd_clones = zap_create(dp->dp_meta_objset,
+                           DMU_OT_DSL_CLONES, DMU_OT_NONE, 0, tx);
+               }
+               VERIFY3U(0, ==, zap_add_int(dp->dp_meta_objset,
+                   dd->dd_phys->dd_clones, origin_head->ds_object, tx));
+
+       }
 
        /* move snapshots to this dir */
        for (snap = list_head(&pa->shared_snaps); snap;
@@ -2480,9 +2862,9 @@ dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
                dsl_dataset_t *ds = snap->ds;
 
                /* unregister props as dsl_dir is changing */
-               if (ds->ds_user_ptr) {
-                       ds->ds_user_evict_func(ds, ds->ds_user_ptr);
-                       ds->ds_user_ptr = NULL;
+               if (ds->ds_objset) {
+                       dmu_objset_evict(ds->ds_objset);
+                       ds->ds_objset = NULL;
                }
                /* move snap name entry */
                VERIFY(0 == dsl_dataset_get_snapname(ds));
@@ -2491,6 +2873,7 @@ dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
                VERIFY(0 == zap_add(dp->dp_meta_objset,
                    hds->ds_phys->ds_snapnames_zapobj, ds->ds_snapname,
                    8, 1, &ds->ds_object, tx));
+
                /* change containing dsl_dir */
                dmu_buf_will_dirty(ds->ds_dbuf, tx);
                ASSERT3U(ds->ds_phys->ds_dir_obj, ==, odd->dd_object);
@@ -2500,7 +2883,41 @@ dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
                VERIFY(0 == dsl_dir_open_obj(dp, dd->dd_object,
                    NULL, ds, &ds->ds_dir));
 
-               ASSERT3U(dsl_prop_numcb(ds), ==, 0);
+               /* move any clone references */
+               if (ds->ds_phys->ds_next_clones_obj &&
+                   spa_version(dp->dp_spa) >= SPA_VERSION_DIR_CLONES) {
+                       zap_cursor_t zc;
+                       zap_attribute_t za;
+
+                       for (zap_cursor_init(&zc, dp->dp_meta_objset,
+                           ds->ds_phys->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;
+                               }
+
+                               VERIFY3U(0, ==, dsl_dataset_hold_obj(dp,
+                                   za.za_first_integer, FTAG, &cnds));
+                               o = cnds->ds_dir->dd_phys->dd_head_dataset_obj;
+
+                               VERIFY3U(zap_remove_int(dp->dp_meta_objset,
+                                   odd->dd_phys->dd_clones, o, tx), ==, 0);
+                               VERIFY3U(zap_add_int(dp->dp_meta_objset,
+                                   dd->dd_phys->dd_clones, o, tx), ==, 0);
+                               dsl_dataset_rele(cnds, FTAG);
+                       }
+                       zap_cursor_fini(&zc);
+               }
+
+               ASSERT0(dsl_prop_numcb(ds));
        }
 
        /*
@@ -2529,8 +2946,8 @@ dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
        origin_ds->ds_phys->ds_unique_bytes = pa->unique;
 
        /* log history record */
-       spa_history_internal_log(LOG_DS_PROMOTE, dd->dd_pool->dp_spa, tx,
-           cr, "dataset = %llu", hds->ds_object);
+       spa_history_log_internal(LOG_DS_PROMOTE, dd->dd_pool->dp_spa, tx,
+           "dataset = %llu", hds->ds_object);
 
        dsl_dir_close(odd, FTAG);
 }
@@ -2595,11 +3012,9 @@ snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep)
 
        *spacep = 0;
        for (snap = list_head(l); snap; snap = list_next(l, snap)) {
-               uint64_t used;
-               int err = bplist_space_birthrange(&snap->ds->ds_deadlist,
-                   mintxg, UINT64_MAX, &used);
-               if (err)
-                       return (err);
+               uint64_t used, comp, uncomp;
+               dsl_deadlist_space_range(&snap->ds->ds_deadlist,
+                   mintxg, UINT64_MAX, &used, &comp, &uncomp);
                *spacep += used;
        }
        return (0);
@@ -2634,16 +3049,17 @@ snaplist_destroy(list_t *l, boolean_t own)
  * NULL, indicating that the clone is not a clone of a clone).
  */
 int
-dsl_dataset_promote(const char *name)
+dsl_dataset_promote(const char *name, char *conflsnap)
 {
        dsl_dataset_t *ds;
        dsl_dir_t *dd;
        dsl_pool_t *dp;
        dmu_object_info_t doi;
-       struct promotearg pa = { 0 };
+       struct promotearg pa;
        struct promotenode *snap;
        int err;
 
+       bzero(&pa, sizeof(struct promotearg));
        err = dsl_dataset_hold(name, FTAG, &ds);
        if (err)
                return (err);
@@ -2686,10 +3102,10 @@ dsl_dataset_promote(const char *name)
        if (err != 0)
                goto out;
 
-       if (dsl_dir_is_clone(snap->ds->ds_dir)) {
-               err = dsl_dataset_own_obj(dp,
+       if (snap->ds->ds_dir->dd_phys->dd_origin_obj != 0) {
+               err = dsl_dataset_hold_obj(dp,
                    snap->ds->ds_dir->dd_phys->dd_origin_obj,
-                   0, FTAG, &pa.origin_origin);
+                   FTAG, &pa.origin_origin);
                if (err != 0)
                        goto out;
        }
@@ -2705,14 +3121,16 @@ out:
        if (err == 0) {
                err = dsl_sync_task_do(dp, dsl_dataset_promote_check,
                    dsl_dataset_promote_sync, ds, &pa,
-                   2 + 2 * doi.doi_physical_blks);
+                   2 + 2 * doi.doi_physical_blocks_512);
+               if (err && pa.err_ds && conflsnap)
+                       (void) strncpy(conflsnap, pa.err_ds, MAXNAMELEN);
        }
 
        snaplist_destroy(&pa.shared_snaps, B_TRUE);
        snaplist_destroy(&pa.clone_snaps, B_FALSE);
        snaplist_destroy(&pa.origin_snaps, B_FALSE);
        if (pa.origin_origin)
-               dsl_dataset_disown(pa.origin_origin, FTAG);
+               dsl_dataset_rele(pa.origin_origin, FTAG);
        dsl_dataset_rele(ds, FTAG);
        return (err);
 }
@@ -2739,9 +3157,11 @@ dsl_dataset_clone_swap_check(void *arg1, void *arg2, dmu_tx_t *tx)
        if (csa->cds->ds_prev != csa->ohds->ds_prev)
                return (EINVAL);
 
-       /* cds should be the clone */
-       if (csa->cds->ds_prev->ds_phys->ds_next_snap_obj !=
-           csa->ohds->ds_object)
+       /* cds should be the clone (unless they are unrelated) */
+       if (csa->cds->ds_prev != NULL &&
+           csa->cds->ds_prev != csa->cds->ds_dir->dd_pool->dp_origin_snap &&
+           csa->ohds->ds_object !=
+           csa->cds->ds_prev->ds_phys->ds_next_snap_obj)
                return (EINVAL);
 
        /* the clone should be a child of the origin */
@@ -2764,38 +3184,49 @@ dsl_dataset_clone_swap_check(void *arg1, void *arg2, dmu_tx_t *tx)
            dsl_dir_space_available(csa->ohds->ds_dir, NULL, 0, TRUE))
                return (ENOSPC);
 
+       if (csa->ohds->ds_quota != 0 &&
+           csa->cds->ds_phys->ds_unique_bytes > csa->ohds->ds_quota)
+               return (EDQUOT);
+
        return (0);
 }
 
 /* ARGSUSED */
 static void
-dsl_dataset_clone_swap_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
+dsl_dataset_clone_swap_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        struct cloneswaparg *csa = arg1;
        dsl_pool_t *dp = csa->cds->ds_dir->dd_pool;
 
        ASSERT(csa->cds->ds_reserved == 0);
-       ASSERT(csa->cds->ds_quota == csa->ohds->ds_quota);
+       ASSERT(csa->ohds->ds_quota == 0 ||
+           csa->cds->ds_phys->ds_unique_bytes <= csa->ohds->ds_quota);
 
        dmu_buf_will_dirty(csa->cds->ds_dbuf, tx);
        dmu_buf_will_dirty(csa->ohds->ds_dbuf, tx);
-       dmu_buf_will_dirty(csa->cds->ds_prev->ds_dbuf, tx);
 
-       if (csa->cds->ds_user_ptr != NULL) {
-               csa->cds->ds_user_evict_func(csa->cds, csa->cds->ds_user_ptr);
-               csa->cds->ds_user_ptr = NULL;
+       if (csa->cds->ds_objset != NULL) {
+               dmu_objset_evict(csa->cds->ds_objset);
+               csa->cds->ds_objset = NULL;
        }
 
-       if (csa->ohds->ds_user_ptr != NULL) {
-               csa->ohds->ds_user_evict_func(csa->ohds,
-                   csa->ohds->ds_user_ptr);
-               csa->ohds->ds_user_ptr = NULL;
+       if (csa->ohds->ds_objset != NULL) {
+               dmu_objset_evict(csa->ohds->ds_objset);
+               csa->ohds->ds_objset = NULL;
        }
 
-       /* reset origin's unique bytes */
-       VERIFY(0 == bplist_space_birthrange(&csa->cds->ds_deadlist,
-           csa->cds->ds_prev->ds_phys->ds_prev_snap_txg, UINT64_MAX,
-           &csa->cds->ds_prev->ds_phys->ds_unique_bytes));
+       /*
+        * Reset origin's unique bytes, if it exists.
+        */
+       if (csa->cds->ds_prev) {
+               dsl_dataset_t *origin = csa->cds->ds_prev;
+               uint64_t comp, uncomp;
+
+               dmu_buf_will_dirty(origin->ds_dbuf, tx);
+               dsl_deadlist_space_range(&csa->cds->ds_deadlist,
+                   origin->ds_phys->ds_prev_snap_txg, UINT64_MAX,
+                   &origin->ds_phys->ds_unique_bytes, &comp, &uncomp);
+       }
 
        /* swap blkptrs */
        {
@@ -2814,13 +3245,13 @@ dsl_dataset_clone_swap_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
                ASSERT3U(csa->cds->ds_dir->dd_phys->
                    dd_used_breakdown[DD_USED_SNAP], ==, 0);
 
-               VERIFY(0 == bplist_space(&csa->cds->ds_deadlist, &cdl_used,
-                   &cdl_comp, &cdl_uncomp));
-               VERIFY(0 == bplist_space(&csa->ohds->ds_deadlist, &odl_used,
-                   &odl_comp, &odl_uncomp));
+               dsl_deadlist_space(&csa->cds->ds_deadlist,
+                   &cdl_used, &cdl_comp, &cdl_uncomp);
+               dsl_deadlist_space(&csa->ohds->ds_deadlist,
+                   &odl_used, &odl_comp, &odl_uncomp);
 
-               dused = csa->cds->ds_phys->ds_used_bytes + cdl_used -
-                   (csa->ohds->ds_phys->ds_used_bytes + odl_used);
+               dused = csa->cds->ds_phys->ds_referenced_bytes + cdl_used -
+                   (csa->ohds->ds_phys->ds_referenced_bytes + odl_used);
                dcomp = csa->cds->ds_phys->ds_compressed_bytes + cdl_comp -
                    (csa->ohds->ds_phys->ds_compressed_bytes + odl_comp);
                duncomp = csa->cds->ds_phys->ds_uncompressed_bytes +
@@ -2838,24 +3269,19 @@ dsl_dataset_clone_swap_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
                 * deadlist (since that's the only thing that's
                 * changing that affects the snapused).
                 */
-               VERIFY(0 == bplist_space_birthrange(&csa->cds->ds_deadlist,
-                   csa->ohds->ds_origin_txg, UINT64_MAX, &cdl_used));
-               VERIFY(0 == bplist_space_birthrange(&csa->ohds->ds_deadlist,
-                   csa->ohds->ds_origin_txg, UINT64_MAX, &odl_used));
+               dsl_deadlist_space_range(&csa->cds->ds_deadlist,
+                   csa->ohds->ds_dir->dd_origin_txg, UINT64_MAX,
+                   &cdl_used, &cdl_comp, &cdl_uncomp);
+               dsl_deadlist_space_range(&csa->ohds->ds_deadlist,
+                   csa->ohds->ds_dir->dd_origin_txg, UINT64_MAX,
+                   &odl_used, &odl_comp, &odl_uncomp);
                dsl_dir_transfer_space(csa->ohds->ds_dir, cdl_used - odl_used,
                    DD_USED_HEAD, DD_USED_SNAP, tx);
        }
 
-#define        SWITCH64(x, y) \
-       { \
-               uint64_t __tmp = (x); \
-               (x) = (y); \
-               (y) = __tmp; \
-       }
-
        /* swap ds_*_bytes */
-       SWITCH64(csa->ohds->ds_phys->ds_used_bytes,
-           csa->cds->ds_phys->ds_used_bytes);
+       SWITCH64(csa->ohds->ds_phys->ds_referenced_bytes,
+           csa->cds->ds_phys->ds_referenced_bytes);
        SWITCH64(csa->ohds->ds_phys->ds_compressed_bytes,
            csa->cds->ds_phys->ds_compressed_bytes);
        SWITCH64(csa->ohds->ds_phys->ds_uncompressed_bytes,
@@ -2867,22 +3293,26 @@ dsl_dataset_clone_swap_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
        dsl_dir_diduse_space(csa->ohds->ds_dir, DD_USED_REFRSRV,
            csa->unused_refres_delta, 0, 0, tx);
 
-       /* swap deadlists */
-       bplist_close(&csa->cds->ds_deadlist);
-       bplist_close(&csa->ohds->ds_deadlist);
+       /*
+        * Swap deadlists.
+        */
+       dsl_deadlist_close(&csa->cds->ds_deadlist);
+       dsl_deadlist_close(&csa->ohds->ds_deadlist);
        SWITCH64(csa->ohds->ds_phys->ds_deadlist_obj,
            csa->cds->ds_phys->ds_deadlist_obj);
-       VERIFY(0 == bplist_open(&csa->cds->ds_deadlist, dp->dp_meta_objset,
-           csa->cds->ds_phys->ds_deadlist_obj));
-       VERIFY(0 == bplist_open(&csa->ohds->ds_deadlist, dp->dp_meta_objset,
-           csa->ohds->ds_phys->ds_deadlist_obj));
+       dsl_deadlist_open(&csa->cds->ds_deadlist, dp->dp_meta_objset,
+           csa->cds->ds_phys->ds_deadlist_obj);
+       dsl_deadlist_open(&csa->ohds->ds_deadlist, dp->dp_meta_objset,
+           csa->ohds->ds_phys->ds_deadlist_obj);
 
-       dsl_pool_ds_clone_swapped(csa->ohds, csa->cds, tx);
+       dsl_scan_ds_clone_swapped(csa->ohds, csa->cds, tx);
 }
 
 /*
- * Swap 'clone' with its origin head file system.  Used at the end
- * of "online recv" to swizzle the file system to the new version.
+ * Swap 'clone' with its origin head datasets.  Used at the end of "zfs
+ * recv" into an existing fs to swizzle the file system to the new
+ * version, and by "zfs rollback".  Can also be used to swap two
+ * independent head datasets if neither has any snapshots.
  */
 int
 dsl_dataset_clone_swap(dsl_dataset_t *clone, dsl_dataset_t *origin_head,
@@ -2894,9 +3324,14 @@ dsl_dataset_clone_swap(dsl_dataset_t *clone, dsl_dataset_t *origin_head,
        ASSERT(clone->ds_owner);
        ASSERT(origin_head->ds_owner);
 retry:
-       /* Need exclusive access for the swap */
-       rw_enter(&clone->ds_rwlock, RW_WRITER);
-       if (!rw_tryenter(&origin_head->ds_rwlock, RW_WRITER)) {
+       /*
+        * Need exclusive access for the swap. If we're swapping these
+        * datasets back after an error, we already hold the locks.
+        */
+       if (!RW_WRITE_HELD(&clone->ds_rwlock))
+               rw_enter(&clone->ds_rwlock, RW_WRITER);
+       if (!RW_WRITE_HELD(&origin_head->ds_rwlock) &&
+           !rw_tryenter(&origin_head->ds_rwlock, RW_WRITER)) {
                rw_exit(&clone->ds_rwlock);
                rw_enter(&origin_head->ds_rwlock, RW_WRITER);
                if (!rw_tryenter(&clone->ds_rwlock, RW_WRITER)) {
@@ -2975,11 +3410,14 @@ dsl_dataset_check_quota(dsl_dataset_t *ds, boolean_t check_quota,
         * on-disk is over quota and there are no pending changes (which
         * may free up space for us).
         */
-       if (ds->ds_phys->ds_used_bytes + inflight >= ds->ds_quota) {
-               if (inflight > 0 || ds->ds_phys->ds_used_bytes < ds->ds_quota)
+       if (ds->ds_phys->ds_referenced_bytes + inflight >= ds->ds_quota) {
+               if (inflight > 0 ||
+                   ds->ds_phys->ds_referenced_bytes < ds->ds_quota)
                        error = ERESTART;
                else
                        error = EDQUOT;
+
+               DMU_TX_STAT_BUMP(dmu_tx_quota);
        }
        mutex_exit(&ds->ds_lock);
 
@@ -2991,62 +3429,66 @@ static int
 dsl_dataset_set_quota_check(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
-       uint64_t *quotap = arg2;
-       uint64_t new_quota = *quotap;
+       dsl_prop_setarg_t *psa = arg2;
+       int err;
 
        if (spa_version(ds->ds_dir->dd_pool->dp_spa) < SPA_VERSION_REFQUOTA)
                return (ENOTSUP);
 
-       if (new_quota == 0)
+       if ((err = dsl_prop_predict_sync(ds->ds_dir, psa)) != 0)
+               return (err);
+
+       if (psa->psa_effective_value == 0)
                return (0);
 
-       if (new_quota < ds->ds_phys->ds_used_bytes ||
-           new_quota < ds->ds_reserved)
+       if (psa->psa_effective_value < ds->ds_phys->ds_referenced_bytes ||
+           psa->psa_effective_value < ds->ds_reserved)
                return (ENOSPC);
 
        return (0);
 }
 
-/* ARGSUSED */
+extern void dsl_prop_set_sync(void *, void *, dmu_tx_t *);
+
 void
-dsl_dataset_set_quota_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
+dsl_dataset_set_quota_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
-       uint64_t *quotap = arg2;
-       uint64_t new_quota = *quotap;
-
-       dmu_buf_will_dirty(ds->ds_dbuf, tx);
-
-       ds->ds_quota = new_quota;
+       dsl_prop_setarg_t *psa = arg2;
+       uint64_t effective_value = psa->psa_effective_value;
 
-       dsl_prop_set_uint64_sync(ds->ds_dir, "refquota", new_quota, cr, tx);
+       dsl_prop_set_sync(ds, psa, tx);
+       DSL_PROP_CHECK_PREDICTION(ds->ds_dir, psa);
 
-       spa_history_internal_log(LOG_DS_REFQUOTA, ds->ds_dir->dd_pool->dp_spa,
-           tx, cr, "%lld dataset = %llu ",
-           (longlong_t)new_quota, ds->ds_object);
+       if (ds->ds_quota != effective_value) {
+               dmu_buf_will_dirty(ds->ds_dbuf, tx);
+               ds->ds_quota = effective_value;
+       }
 }
 
 int
-dsl_dataset_set_quota(const char *dsname, uint64_t quota)
+dsl_dataset_set_quota(const char *dsname, zprop_source_t source, uint64_t quota)
 {
        dsl_dataset_t *ds;
+       dsl_prop_setarg_t psa;
        int err;
 
+       dsl_prop_setarg_init_uint64(&psa, "refquota", source, &quota);
+
        err = dsl_dataset_hold(dsname, FTAG, &ds);
        if (err)
                return (err);
 
-       if (quota != ds->ds_quota) {
-               /*
-                * If someone removes a file, then tries to set the quota, we
-                * want to make sure the file freeing takes effect.
-                */
-               txg_wait_open(ds->ds_dir->dd_pool, 0);
+       /*
+        * If someone removes a file, then tries to set the quota, we
+        * want to make sure the file freeing takes effect.
+        */
+       txg_wait_open(ds->ds_dir->dd_pool, 0);
+
+       err = dsl_sync_task_do(ds->ds_dir->dd_pool,
+           dsl_dataset_set_quota_check, dsl_dataset_set_quota_sync,
+           ds, &psa, 0);
 
-               err = dsl_sync_task_do(ds->ds_dir->dd_pool,
-                   dsl_dataset_set_quota_check, dsl_dataset_set_quota_sync,
-                   ds, &quota, 0);
-       }
        dsl_dataset_rele(ds, FTAG);
        return (err);
 }
@@ -3055,9 +3497,10 @@ static int
 dsl_dataset_set_reservation_check(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
-       uint64_t *reservationp = arg2;
-       uint64_t new_reservation = *reservationp;
+       dsl_prop_setarg_t *psa = arg2;
+       uint64_t effective_value;
        uint64_t unique;
+       int err;
 
        if (spa_version(ds->ds_dir->dd_pool->dp_spa) <
            SPA_VERSION_REFRESERVATION)
@@ -3066,6 +3509,11 @@ dsl_dataset_set_reservation_check(void *arg1, void *arg2, dmu_tx_t *tx)
        if (dsl_dataset_is_snapshot(ds))
                return (EINVAL);
 
+       if ((err = dsl_prop_predict_sync(ds->ds_dir, psa)) != 0)
+               return (err);
+
+       effective_value = psa->psa_effective_value;
+
        /*
         * If we are doing the preliminary check in open context, the
         * space estimates may be inaccurate.
@@ -3074,67 +3522,846 @@ dsl_dataset_set_reservation_check(void *arg1, void *arg2, dmu_tx_t *tx)
                return (0);
 
        mutex_enter(&ds->ds_lock);
-       unique = dsl_dataset_unique(ds);
+       if (!DS_UNIQUE_IS_ACCURATE(ds))
+               dsl_dataset_recalc_head_uniq(ds);
+       unique = ds->ds_phys->ds_unique_bytes;
        mutex_exit(&ds->ds_lock);
 
-       if (MAX(unique, new_reservation) > MAX(unique, ds->ds_reserved)) {
-               uint64_t delta = MAX(unique, new_reservation) -
+       if (MAX(unique, effective_value) > MAX(unique, ds->ds_reserved)) {
+               uint64_t delta = MAX(unique, effective_value) -
                    MAX(unique, ds->ds_reserved);
 
                if (delta > dsl_dir_space_available(ds->ds_dir, NULL, 0, TRUE))
                        return (ENOSPC);
                if (ds->ds_quota > 0 &&
-                   new_reservation > ds->ds_quota)
+                   effective_value > ds->ds_quota)
                        return (ENOSPC);
        }
 
        return (0);
 }
 
-/* ARGSUSED */
 static void
-dsl_dataset_set_reservation_sync(void *arg1, void *arg2, cred_t *cr,
-    dmu_tx_t *tx)
+dsl_dataset_set_reservation_sync(void *arg1, void *arg2, dmu_tx_t *tx)
 {
        dsl_dataset_t *ds = arg1;
-       uint64_t *reservationp = arg2;
-       uint64_t new_reservation = *reservationp;
+       dsl_prop_setarg_t *psa = arg2;
+       uint64_t effective_value = psa->psa_effective_value;
        uint64_t unique;
        int64_t delta;
 
+       dsl_prop_set_sync(ds, psa, tx);
+       DSL_PROP_CHECK_PREDICTION(ds->ds_dir, psa);
+
        dmu_buf_will_dirty(ds->ds_dbuf, tx);
 
        mutex_enter(&ds->ds_dir->dd_lock);
        mutex_enter(&ds->ds_lock);
-       unique = dsl_dataset_unique(ds);
-       delta = MAX(0, (int64_t)(new_reservation - unique)) -
+       ASSERT(DS_UNIQUE_IS_ACCURATE(ds));
+       unique = ds->ds_phys->ds_unique_bytes;
+       delta = MAX(0, (int64_t)(effective_value - unique)) -
            MAX(0, (int64_t)(ds->ds_reserved - unique));
-       ds->ds_reserved = new_reservation;
+       ds->ds_reserved = effective_value;
        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);
-       dsl_prop_set_uint64_sync(ds->ds_dir, "refreservation",
-           new_reservation, cr, tx);
-
-       spa_history_internal_log(LOG_DS_REFRESERV,
-           ds->ds_dir->dd_pool->dp_spa, tx, cr, "%lld dataset = %llu",
-           (longlong_t)new_reservation, ds->ds_object);
 }
 
 int
-dsl_dataset_set_reservation(const char *dsname, uint64_t reservation)
+dsl_dataset_set_reservation(const char *dsname, zprop_source_t source,
+    uint64_t reservation)
 {
        dsl_dataset_t *ds;
+       dsl_prop_setarg_t psa;
        int err;
 
+       dsl_prop_setarg_init_uint64(&psa, "refreservation", source,
+           &reservation);
+
        err = dsl_dataset_hold(dsname, FTAG, &ds);
        if (err)
                return (err);
 
        err = dsl_sync_task_do(ds->ds_dir->dd_pool,
            dsl_dataset_set_reservation_check,
-           dsl_dataset_set_reservation_sync, ds, &reservation, 0);
+           dsl_dataset_set_reservation_sync, ds, &psa, 0);
+
        dsl_dataset_rele(ds, FTAG);
        return (err);
 }
+
+typedef struct zfs_hold_cleanup_arg {
+       dsl_pool_t *dp;
+       uint64_t dsobj;
+       char htag[MAXNAMELEN];
+} zfs_hold_cleanup_arg_t;
+
+static void
+dsl_dataset_user_release_onexit(void *arg)
+{
+       zfs_hold_cleanup_arg_t *ca = arg;
+
+       (void) dsl_dataset_user_release_tmp(ca->dp, ca->dsobj, ca->htag,
+           B_TRUE);
+       kmem_free(ca, sizeof (zfs_hold_cleanup_arg_t));
+}
+
+void
+dsl_register_onexit_hold_cleanup(dsl_dataset_t *ds, const char *htag,
+    minor_t minor)
+{
+       zfs_hold_cleanup_arg_t *ca;
+
+       ca = kmem_alloc(sizeof (zfs_hold_cleanup_arg_t), KM_SLEEP);
+       ca->dp = ds->ds_dir->dd_pool;
+       ca->dsobj = ds->ds_object;
+       (void) strlcpy(ca->htag, htag, sizeof (ca->htag));
+       VERIFY3U(0, ==, zfs_onexit_add_cb(minor,
+           dsl_dataset_user_release_onexit, ca, NULL));
+}
+
+/*
+ * If you add new checks here, you may need to add
+ * additional checks to the "temporary" case in
+ * snapshot_check() in dmu_objset.c.
+ */
+static int
+dsl_dataset_user_hold_check(void *arg1, void *arg2, dmu_tx_t *tx)
+{
+       dsl_dataset_t *ds = arg1;
+       struct dsl_ds_holdarg *ha = arg2;
+       char *htag = ha->htag;
+       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       int error = 0;
+
+       if (spa_version(ds->ds_dir->dd_pool->dp_spa) < SPA_VERSION_USERREFS)
+               return (ENOTSUP);
+
+       if (!dsl_dataset_is_snapshot(ds))
+               return (EINVAL);
+
+       /* tags must be unique */
+       mutex_enter(&ds->ds_lock);
+       if (ds->ds_phys->ds_userrefs_obj) {
+               error = zap_lookup(mos, ds->ds_phys->ds_userrefs_obj, htag,
+                   8, 1, tx);
+               if (error == 0)
+                       error = EEXIST;
+               else if (error == ENOENT)
+                       error = 0;
+       }
+       mutex_exit(&ds->ds_lock);
+
+       if (error == 0 && ha->temphold &&
+           strlen(htag) + MAX_TAG_PREFIX_LEN >= MAXNAMELEN)
+               error = E2BIG;
+
+       return (error);
+}
+
+void
+dsl_dataset_user_hold_sync(void *arg1, void *arg2, dmu_tx_t *tx)
+{
+       dsl_dataset_t *ds = arg1;
+       struct dsl_ds_holdarg *ha = arg2;
+       char *htag = ha->htag;
+       dsl_pool_t *dp = ds->ds_dir->dd_pool;
+       objset_t *mos = dp->dp_meta_objset;
+       uint64_t now = gethrestime_sec();
+       uint64_t zapobj;
+
+       mutex_enter(&ds->ds_lock);
+       if (ds->ds_phys->ds_userrefs_obj == 0) {
+               /*
+                * This is the first user hold for this dataset.  Create
+                * the userrefs zap object.
+                */
+               dmu_buf_will_dirty(ds->ds_dbuf, tx);
+               zapobj = ds->ds_phys->ds_userrefs_obj =
+                   zap_create(mos, DMU_OT_USERREFS, DMU_OT_NONE, 0, tx);
+       } else {
+               zapobj = ds->ds_phys->ds_userrefs_obj;
+       }
+       ds->ds_userrefs++;
+       mutex_exit(&ds->ds_lock);
+
+       VERIFY(0 == zap_add(mos, zapobj, htag, 8, 1, &now, tx));
+
+       if (ha->temphold) {
+               VERIFY(0 == dsl_pool_user_hold(dp, ds->ds_object,
+                   htag, &now, tx));
+       }
+
+       spa_history_log_internal(LOG_DS_USER_HOLD,
+           dp->dp_spa, tx, "<%s> temp = %d dataset = %llu", htag,
+           (int)ha->temphold, ds->ds_object);
+}
+
+static int
+dsl_dataset_user_hold_one(const char *dsname, void *arg)
+{
+       struct dsl_ds_holdarg *ha = arg;
+       dsl_dataset_t *ds;
+       int error;
+       char *name;
+
+       /* alloc a buffer to hold dsname@snapname plus terminating NULL */
+       name = kmem_asprintf("%s@%s", dsname, ha->snapname);
+       error = dsl_dataset_hold(name, ha->dstg, &ds);
+       strfree(name);
+       if (error == 0) {
+               ha->gotone = B_TRUE;
+               dsl_sync_task_create(ha->dstg, dsl_dataset_user_hold_check,
+                   dsl_dataset_user_hold_sync, ds, ha, 0);
+       } else if (error == ENOENT && ha->recursive) {
+               error = 0;
+       } else {
+               (void) strlcpy(ha->failed, dsname, sizeof (ha->failed));
+       }
+       return (error);
+}
+
+int
+dsl_dataset_user_hold_for_send(dsl_dataset_t *ds, char *htag,
+    boolean_t temphold)
+{
+       struct dsl_ds_holdarg *ha;
+       int error;
+
+       ha = kmem_zalloc(sizeof (struct dsl_ds_holdarg), KM_SLEEP);
+       ha->htag = htag;
+       ha->temphold = temphold;
+       error = dsl_sync_task_do(ds->ds_dir->dd_pool,
+           dsl_dataset_user_hold_check, dsl_dataset_user_hold_sync,
+           ds, ha, 0);
+       kmem_free(ha, sizeof (struct dsl_ds_holdarg));
+
+       return (error);
+}
+
+int
+dsl_dataset_user_hold(char *dsname, char *snapname, char *htag,
+    boolean_t recursive, boolean_t temphold, int cleanup_fd)
+{
+       struct dsl_ds_holdarg *ha;
+       dsl_sync_task_t *dst;
+       spa_t *spa;
+       int error;
+       minor_t minor = 0;
+
+       if (cleanup_fd != -1) {
+               /* Currently we only support cleanup-on-exit of tempholds. */
+               if (!temphold)
+                       return (EINVAL);
+               error = zfs_onexit_fd_hold(cleanup_fd, &minor);
+               if (error)
+                       return (error);
+       }
+
+       ha = kmem_zalloc(sizeof (struct dsl_ds_holdarg), KM_SLEEP);
+
+       (void) strlcpy(ha->failed, dsname, sizeof (ha->failed));
+
+       error = spa_open(dsname, &spa, FTAG);
+       if (error) {
+               kmem_free(ha, sizeof (struct dsl_ds_holdarg));
+               if (cleanup_fd != -1)
+                       zfs_onexit_fd_rele(cleanup_fd);
+               return (error);
+       }
+
+       ha->dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
+       ha->htag = htag;
+       ha->snapname = snapname;
+       ha->recursive = recursive;
+       ha->temphold = temphold;
+
+       if (recursive) {
+               error = dmu_objset_find(dsname, dsl_dataset_user_hold_one,
+                   ha, DS_FIND_CHILDREN);
+       } else {
+               error = dsl_dataset_user_hold_one(dsname, ha);
+       }
+       if (error == 0)
+               error = dsl_sync_task_group_wait(ha->dstg);
+
+       for (dst = list_head(&ha->dstg->dstg_tasks); dst;
+           dst = list_next(&ha->dstg->dstg_tasks, dst)) {
+               dsl_dataset_t *ds = dst->dst_arg1;
+
+               if (dst->dst_err) {
+                       dsl_dataset_name(ds, ha->failed);
+                       *strchr(ha->failed, '@') = '\0';
+               } else if (error == 0 && minor != 0 && temphold) {
+                       /*
+                        * If this hold is to be released upon process exit,
+                        * register that action now.
+                        */
+                       dsl_register_onexit_hold_cleanup(ds, htag, minor);
+               }
+               dsl_dataset_rele(ds, ha->dstg);
+       }
+
+       if (error == 0 && recursive && !ha->gotone)
+               error = ENOENT;
+
+       if (error)
+               (void) strlcpy(dsname, ha->failed, sizeof (ha->failed));
+
+       dsl_sync_task_group_destroy(ha->dstg);
+
+       kmem_free(ha, sizeof (struct dsl_ds_holdarg));
+       spa_close(spa, FTAG);
+       if (cleanup_fd != -1)
+               zfs_onexit_fd_rele(cleanup_fd);
+       return (error);
+}
+
+struct dsl_ds_releasearg {
+       dsl_dataset_t *ds;
+       const char *htag;
+       boolean_t own;          /* do we own or just hold ds? */
+};
+
+static int
+dsl_dataset_release_might_destroy(dsl_dataset_t *ds, const char *htag,
+    boolean_t *might_destroy)
+{
+       objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
+       uint64_t zapobj;
+       uint64_t tmp;
+       int error;
+
+       *might_destroy = B_FALSE;
+
+       mutex_enter(&ds->ds_lock);
+       zapobj = ds->ds_phys->ds_userrefs_obj;
+       if (zapobj == 0) {
+               /* The tag can't possibly exist */
+               mutex_exit(&ds->ds_lock);
+               return (ESRCH);
+       }
+
+       /* Make sure the tag exists */
+       error = zap_lookup(mos, zapobj, htag, 8, 1, &tmp);
+       if (error) {
+               mutex_exit(&ds->ds_lock);
+               if (error == ENOENT)
+                       error = ESRCH;
+               return (error);
+       }
+
+       if (ds->ds_userrefs == 1 && ds->ds_phys->ds_num_children == 1 &&
+           DS_IS_DEFER_DESTROY(ds))
+               *might_destroy = B_TRUE;
+
+       mutex_exit(&ds->ds_lock);
+       return (0);
+}
+
+static int
+dsl_dataset_user_release_check(void *arg1, void *tag, dmu_tx_t *tx)
+{
+       struct dsl_ds_releasearg *ra = arg1;
+       dsl_dataset_t *ds = ra->ds;
+       boolean_t might_destroy;
+       int error;
+
+       if (spa_version(ds->ds_dir->dd_pool->dp_spa) < SPA_VERSION_USERREFS)
+               return (ENOTSUP);
+
+       error = dsl_dataset_release_might_destroy(ds, ra->htag, &might_destroy);
+       if (error)
+               return (error);
+
+       if (might_destroy) {
+               struct dsl_ds_destroyarg dsda = {0};
+
+               if (dmu_tx_is_syncing(tx)) {
+                       /*
+                        * If we're not prepared to remove the snapshot,
+                        * we can't allow the release to happen right now.
+                        */
+                       if (!ra->own)
+                               return (EBUSY);
+               }
+               dsda.ds = ds;
+               dsda.releasing = B_TRUE;
+               return (dsl_dataset_destroy_check(&dsda, tag, tx));
+       }
+
+       return (0);
+}
+
+static void
+dsl_dataset_user_release_sync(void *arg1, void *tag, dmu_tx_t *tx)
+{
+       struct dsl_ds_releasearg *ra = arg1;
+       dsl_dataset_t *ds = ra->ds;
+       dsl_pool_t *dp = ds->ds_dir->dd_pool;
+       objset_t *mos = dp->dp_meta_objset;
+       uint64_t zapobj;
+       uint64_t dsobj = ds->ds_object;
+       uint64_t refs;
+       int error;
+
+       mutex_enter(&ds->ds_lock);
+       ds->ds_userrefs--;
+       refs = ds->ds_userrefs;
+       mutex_exit(&ds->ds_lock);
+       error = dsl_pool_user_release(dp, ds->ds_object, ra->htag, tx);
+       VERIFY(error == 0 || error == ENOENT);
+       zapobj = ds->ds_phys->ds_userrefs_obj;
+       VERIFY(0 == zap_remove(mos, zapobj, ra->htag, tx));
+
+       spa_history_log_internal(LOG_DS_USER_RELEASE,
+           dp->dp_spa, tx, "<%s> %lld dataset = %llu",
+           ra->htag, (longlong_t)refs, dsobj);
+
+       if (ds->ds_userrefs == 0 && ds->ds_phys->ds_num_children == 1 &&
+           DS_IS_DEFER_DESTROY(ds)) {
+               struct dsl_ds_destroyarg dsda = {0};
+
+               ASSERT(ra->own);
+               dsda.ds = ds;
+               dsda.releasing = B_TRUE;
+               /* We already did the destroy_check */
+               dsl_dataset_destroy_sync(&dsda, tag, tx);
+       }
+}
+
+static int
+dsl_dataset_user_release_one(const char *dsname, void *arg)
+{
+       struct dsl_ds_holdarg *ha = arg;
+       struct dsl_ds_releasearg *ra;
+       dsl_dataset_t *ds;
+       int error;
+       void *dtag = ha->dstg;
+       char *name;
+       boolean_t own = B_FALSE;
+       boolean_t might_destroy;
+
+       /* alloc a buffer to hold dsname@snapname, plus the terminating NULL */
+       name = kmem_asprintf("%s@%s", dsname, ha->snapname);
+       error = dsl_dataset_hold(name, dtag, &ds);
+       strfree(name);
+       if (error == ENOENT && ha->recursive)
+               return (0);
+       (void) strlcpy(ha->failed, dsname, sizeof (ha->failed));
+       if (error)
+               return (error);
+
+       ha->gotone = B_TRUE;
+
+       ASSERT(dsl_dataset_is_snapshot(ds));
+
+       error = dsl_dataset_release_might_destroy(ds, ha->htag, &might_destroy);
+       if (error) {
+               dsl_dataset_rele(ds, dtag);
+               return (error);
+       }
+
+       if (might_destroy) {
+#ifdef _KERNEL
+               name = kmem_asprintf("%s@%s", dsname, ha->snapname);
+               error = zfs_unmount_snap(name, NULL);
+               strfree(name);
+               if (error) {
+                       dsl_dataset_rele(ds, dtag);
+                       return (error);
+               }
+#endif
+               if (!dsl_dataset_tryown(ds, B_TRUE, dtag)) {
+                       dsl_dataset_rele(ds, dtag);
+                       return (EBUSY);
+               } else {
+                       own = B_TRUE;
+                       dsl_dataset_make_exclusive(ds, dtag);
+               }
+       }
+
+       ra = kmem_alloc(sizeof (struct dsl_ds_releasearg), KM_SLEEP);
+       ra->ds = ds;
+       ra->htag = ha->htag;
+       ra->own = own;
+       dsl_sync_task_create(ha->dstg, dsl_dataset_user_release_check,
+           dsl_dataset_user_release_sync, ra, dtag, 0);
+
+       return (0);
+}
+
+int
+dsl_dataset_user_release(char *dsname, char *snapname, char *htag,
+    boolean_t recursive)
+{
+       struct dsl_ds_holdarg *ha;
+       dsl_sync_task_t *dst;
+       spa_t *spa;
+       int error;
+
+top:
+       ha = kmem_zalloc(sizeof (struct dsl_ds_holdarg), KM_SLEEP);
+
+       (void) strlcpy(ha->failed, dsname, sizeof (ha->failed));
+
+       error = spa_open(dsname, &spa, FTAG);
+       if (error) {
+               kmem_free(ha, sizeof (struct dsl_ds_holdarg));
+               return (error);
+       }
+
+       ha->dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
+       ha->htag = htag;
+       ha->snapname = snapname;
+       ha->recursive = recursive;
+       if (recursive) {
+               error = dmu_objset_find(dsname, dsl_dataset_user_release_one,
+                   ha, DS_FIND_CHILDREN);
+       } else {
+               error = dsl_dataset_user_release_one(dsname, ha);
+       }
+       if (error == 0)
+               error = dsl_sync_task_group_wait(ha->dstg);
+
+       for (dst = list_head(&ha->dstg->dstg_tasks); dst;
+           dst = list_next(&ha->dstg->dstg_tasks, dst)) {
+               struct dsl_ds_releasearg *ra = dst->dst_arg1;
+               dsl_dataset_t *ds = ra->ds;
+
+               if (dst->dst_err)
+                       dsl_dataset_name(ds, ha->failed);
+
+               if (ra->own)
+                       dsl_dataset_disown(ds, ha->dstg);
+               else
+                       dsl_dataset_rele(ds, ha->dstg);
+
+               kmem_free(ra, sizeof (struct dsl_ds_releasearg));
+       }
+
+       if (error == 0 && recursive && !ha->gotone)
+               error = ENOENT;
+
+       if (error && error != EBUSY)
+               (void) strlcpy(dsname, ha->failed, sizeof (ha->failed));
+
+       dsl_sync_task_group_destroy(ha->dstg);
+       kmem_free(ha, sizeof (struct dsl_ds_holdarg));
+       spa_close(spa, FTAG);
+
+       /*
+        * We can get EBUSY if we were racing with deferred destroy and
+        * dsl_dataset_user_release_check() hadn't done the necessary
+        * open context setup.  We can also get EBUSY if we're racing
+        * with destroy and that thread is the ds_owner.  Either way
+        * the busy condition should be transient, and we should retry
+        * the release operation.
+        */
+       if (error == EBUSY)
+               goto top;
+
+       return (error);
+}
+
+/*
+ * Called at spa_load time (with retry == B_FALSE) to release a stale
+ * temporary user hold. Also called by the onexit code (with retry == B_TRUE).
+ */
+int
+dsl_dataset_user_release_tmp(dsl_pool_t *dp, uint64_t dsobj, char *htag,
+    boolean_t retry)
+{
+       dsl_dataset_t *ds;
+       char *snap;
+       char *name;
+       int namelen;
+       int error;
+
+       do {
+               rw_enter(&dp->dp_config_rwlock, RW_READER);
+               error = dsl_dataset_hold_obj(dp, dsobj, FTAG, &ds);
+               rw_exit(&dp->dp_config_rwlock);
+               if (error)
+                       return (error);
+               namelen = dsl_dataset_namelen(ds)+1;
+               name = kmem_alloc(namelen, KM_SLEEP);
+               dsl_dataset_name(ds, name);
+               dsl_dataset_rele(ds, FTAG);
+
+               snap = strchr(name, '@');
+               *snap = '\0';
+               ++snap;
+               error = dsl_dataset_user_release(name, snap, htag, B_FALSE);
+               kmem_free(name, namelen);
+
+               /*
+                * The object can't have been destroyed because we have a hold,
+                * but it might have been renamed, resulting in ENOENT.  Retry
+                * if we've been requested to do so.
+                *
+                * It would be nice if we could use the dsobj all the way
+                * through and avoid ENOENT entirely.  But we might need to
+                * unmount the snapshot, and there's currently no way to lookup
+                * a vfsp using a ZFS object id.
+                */
+       } while ((error == ENOENT) && retry);
+
+       return (error);
+}
+
+int
+dsl_dataset_get_holds(const char *dsname, nvlist_t **nvp)
+{
+       dsl_dataset_t *ds;
+       int err;
+
+       err = dsl_dataset_hold(dsname, FTAG, &ds);
+       if (err)
+               return (err);
+
+       VERIFY(0 == nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP));
+       if (ds->ds_phys->ds_userrefs_obj != 0) {
+               zap_attribute_t *za;
+               zap_cursor_t zc;
+
+               za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
+               for (zap_cursor_init(&zc, ds->ds_dir->dd_pool->dp_meta_objset,
+                   ds->ds_phys->ds_userrefs_obj);
+                   zap_cursor_retrieve(&zc, za) == 0;
+                   zap_cursor_advance(&zc)) {
+                       VERIFY(0 == nvlist_add_uint64(*nvp, za->za_name,
+                           za->za_first_integer));
+               }
+               zap_cursor_fini(&zc);
+               kmem_free(za, sizeof (zap_attribute_t));
+       }
+       dsl_dataset_rele(ds, FTAG);
+       return (0);
+}
+
+/*
+ * Note, this function is used as the callback for dmu_objset_find().  We
+ * always return 0 so that we will continue to find and process
+ * inconsistent datasets, even if we encounter an error trying to
+ * process one of them.
+ */
+/* ARGSUSED */
+int
+dsl_destroy_inconsistent(const char *dsname, void *arg)
+{
+       dsl_dataset_t *ds;
+
+       if (dsl_dataset_own(dsname, B_TRUE, FTAG, &ds) == 0) {
+               if (DS_IS_INCONSISTENT(ds))
+                       (void) dsl_dataset_destroy(ds, FTAG, B_FALSE);
+               else
+                       dsl_dataset_disown(ds, FTAG);
+       }
+       return (0);
+}
+
+
+/*
+ * 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.
+ *
+ * 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 snapshots, thus reducing new's used space relative to old's.
+ * Specifically, this is the space that was born before old->ds_creation_txg,
+ * and freed before new (ie. on new's deadlist or a previous deadlist).
+ *
+ * space freed                         [---------------------]
+ * snapshots                       ---O-------O--------O-------O------
+ *                                         oldsnap            new
+ */
+int
+dsl_dataset_space_written(dsl_dataset_t *oldsnap, dsl_dataset_t *new,
+    uint64_t *usedp, uint64_t *compp, uint64_t *uncompp)
+{
+       int err = 0;
+       uint64_t snapobj;
+       dsl_pool_t *dp = new->ds_dir->dd_pool;
+
+       *usedp = 0;
+       *usedp += new->ds_phys->ds_referenced_bytes;
+       *usedp -= oldsnap->ds_phys->ds_referenced_bytes;
+
+       *compp = 0;
+       *compp += new->ds_phys->ds_compressed_bytes;
+       *compp -= oldsnap->ds_phys->ds_compressed_bytes;
+
+       *uncompp = 0;
+       *uncompp += new->ds_phys->ds_uncompressed_bytes;
+       *uncompp -= oldsnap->ds_phys->ds_uncompressed_bytes;
+
+       rw_enter(&dp->dp_config_rwlock, RW_READER);
+       snapobj = new->ds_object;
+       while (snapobj != oldsnap->ds_object) {
+               dsl_dataset_t *snap;
+               uint64_t used, comp, uncomp;
+
+               if (snapobj == new->ds_object) {
+                       snap = new;
+               } else {
+                       err = dsl_dataset_hold_obj(dp, snapobj, FTAG, &snap);
+                       if (err != 0)
+                               break;
+               }
+
+               if (snap->ds_phys->ds_prev_snap_txg ==
+                   oldsnap->ds_phys->ds_creation_txg) {
+                       /*
+                        * The blocks in the deadlist can not be born after
+                        * ds_prev_snap_txg, so get the whole deadlist space,
+                        * which is more efficient (especially for old-format
+                        * deadlists).  Unfortunately the deadlist code
+                        * doesn't have enough information to make this
+                        * optimization itself.
+                        */
+                       dsl_deadlist_space(&snap->ds_deadlist,
+                           &used, &comp, &uncomp);
+               } else {
+                       dsl_deadlist_space_range(&snap->ds_deadlist,
+                           0, oldsnap->ds_phys->ds_creation_txg,
+                           &used, &comp, &uncomp);
+               }
+               *usedp += used;
+               *compp += comp;
+               *uncompp += uncomp;
+
+               /*
+                * If we get to the beginning of the chain of snapshots
+                * (ds_prev_snap_obj == 0) before oldsnap, then oldsnap
+                * was not a snapshot of/before new.
+                */
+               snapobj = snap->ds_phys->ds_prev_snap_obj;
+               if (snap != new)
+                       dsl_dataset_rele(snap, FTAG);
+               if (snapobj == 0) {
+                       err = EINVAL;
+                       break;
+               }
+
+       }
+       rw_exit(&dp->dp_config_rwlock);
+       return (err);
+}
+
+/*
+ * 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(dsl_dataset_is_snapshot(firstsnap));
+       ASSERT(dsl_dataset_is_snapshot(lastsnap));
+
+       /*
+        * Check that the snapshots are in the same dsl_dir, and firstsnap
+        * is before lastsnap.
+        */
+       if (firstsnap->ds_dir != lastsnap->ds_dir ||
+           firstsnap->ds_phys->ds_creation_txg >
+           lastsnap->ds_phys->ds_creation_txg)
+               return (EINVAL);
+
+       *usedp = *compp = *uncompp = 0;
+
+       rw_enter(&dp->dp_config_rwlock, RW_READER);
+       snapobj = lastsnap->ds_phys->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,
+                   firstsnap->ds_phys->ds_prev_snap_txg, UINT64_MAX,
+                   &used, &comp, &uncomp);
+               *usedp += used;
+               *compp += comp;
+               *uncompp += uncomp;
+
+               snapobj = ds->ds_phys->ds_prev_snap_obj;
+               ASSERT3U(snapobj, !=, 0);
+               dsl_dataset_rele(ds, FTAG);
+       }
+       rw_exit(&dp->dp_config_rwlock);
+       return (err);
+}
+
+#if defined(_KERNEL) && defined(HAVE_SPL)
+EXPORT_SYMBOL(dmu_snapshots_destroy_nvl);
+EXPORT_SYMBOL(dsl_dataset_hold);
+EXPORT_SYMBOL(dsl_dataset_hold_obj);
+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_disown);
+EXPORT_SYMBOL(dsl_dataset_drop_ref);
+EXPORT_SYMBOL(dsl_dataset_tryown);
+EXPORT_SYMBOL(dsl_dataset_make_exclusive);
+EXPORT_SYMBOL(dsl_dataset_create_sync);
+EXPORT_SYMBOL(dsl_dataset_create_sync_dd);
+EXPORT_SYMBOL(dsl_dataset_destroy);
+EXPORT_SYMBOL(dsl_dataset_destroy_check);
+EXPORT_SYMBOL(dsl_dataset_destroy_sync);
+EXPORT_SYMBOL(dsl_dataset_snapshot_check);
+EXPORT_SYMBOL(dsl_dataset_snapshot_sync);
+EXPORT_SYMBOL(dsl_dataset_rename);
+EXPORT_SYMBOL(dsl_dataset_promote);
+EXPORT_SYMBOL(dsl_dataset_clone_swap);
+EXPORT_SYMBOL(dsl_dataset_user_hold);
+EXPORT_SYMBOL(dsl_dataset_user_release);
+EXPORT_SYMBOL(dsl_dataset_user_release_tmp);
+EXPORT_SYMBOL(dsl_dataset_get_holds);
+EXPORT_SYMBOL(dsl_dataset_get_blkptr);
+EXPORT_SYMBOL(dsl_dataset_set_blkptr);
+EXPORT_SYMBOL(dsl_dataset_get_spa);
+EXPORT_SYMBOL(dsl_dataset_modified_since_lastsnap);
+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_block_freeable);
+EXPORT_SYMBOL(dsl_dataset_prev_snap_txg);
+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_set_quota);
+EXPORT_SYMBOL(dsl_dataset_set_quota_sync);
+EXPORT_SYMBOL(dsl_dataset_set_reservation);
+EXPORT_SYMBOL(dsl_destroy_inconsistent);
+#endif