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dsl_dataset.c

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

#include <sys/dmu_objset.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_synctask.h>
#include <sys/dmu_traverse.h>
#include <sys/dmu_tx.h>
#include <sys/arc.h>
#include <sys/zio.h>
#include <sys/zap.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>

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     DS_REF_MAX  (1ULL << 62)

#define     DSL_DEADLIST_BLOCKSIZE  SPA_MAXBLOCKSIZE

#define     DSL_DATASET_IS_DESTROYED(ds)  ((ds)->ds_owner == dsl_reaper)


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

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

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

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

void
dsl_dataset_block_born(dsl_dataset_t *ds, 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);
      int64_t delta;

      dprintf_bp(bp, "born, ds=%p\n", 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);
      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);
            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_compressed_bytes += compressed;
      ds->ds_phys->ds_uncompressed_bytes += uncompressed;
      ds->ds_phys->ds_unique_bytes += used;
      mutex_exit(&ds->ds_lock);
      dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD, delta,
          compressed, uncompressed, tx);
      dsl_dir_transfer_space(ds->ds_dir, used - delta,
          DD_USED_REFRSRV, DD_USED_HEAD, tx);
      mutex_exit(&ds->ds_dir->dd_lock);
}

int
dsl_dataset_block_kill(dsl_dataset_t *ds, blkptr_t *bp, zio_t *pio,
    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);

      ASSERT(pio != NULL);
      ASSERT(dmu_tx_is_syncing(tx));
      /* No block pointer => nothing to free */
      if (BP_IS_HOLE(bp))
            return (0);

      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);
            return (used);
      }
      ASSERT3P(tx->tx_pool, ==, ds->ds_dir->dd_pool);

      ASSERT(!dsl_dataset_is_snapshot(ds));
      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);

            mutex_enter(&ds->ds_dir->dd_lock);
            mutex_enter(&ds->ds_lock);
            ASSERT(ds->ds_phys->ds_unique_bytes >= used ||
                !DS_UNIQUE_IS_ACCURATE(ds));
            delta = parent_delta(ds, -used);
            ds->ds_phys->ds_unique_bytes -= used;
            mutex_exit(&ds->ds_lock);
            dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD,
                delta, -compressed, -uncompressed, tx);
            dsl_dir_transfer_space(ds->ds_dir, -used - delta,
                DD_USED_REFRSRV, DD_USED_HEAD, tx);
            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));
            ASSERT3U(ds->ds_prev->ds_object, ==,
                ds->ds_phys->ds_prev_snap_obj);
            ASSERT(ds->ds_prev->ds_phys->ds_num_children > 0);
            /* if (bp->blk_birth > prev prev snap txg) prev unique += bs */
            if (ds->ds_prev->ds_phys->ds_next_snap_obj ==
                ds->ds_object && bp->blk_birth >
                ds->ds_prev->ds_phys->ds_prev_snap_txg) {
                  dmu_buf_will_dirty(ds->ds_prev->ds_dbuf, tx);
                  mutex_enter(&ds->ds_prev->ds_lock);
                  ds->ds_prev->ds_phys->ds_unique_bytes += used;
                  mutex_exit(&ds->ds_prev->ds_lock);
            }
            if (bp->blk_birth > ds->ds_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_compressed_bytes, >=, compressed);
      ds->ds_phys->ds_compressed_bytes -= compressed;
      ASSERT3U(ds->ds_phys->ds_uncompressed_bytes, >=, uncompressed);
      ds->ds_phys->ds_uncompressed_bytes -= uncompressed;
      mutex_exit(&ds->ds_lock);

      return (used);
}

uint64_t
dsl_dataset_prev_snap_txg(dsl_dataset_t *ds)
{
      uint64_t trysnap = 0;

      if (ds == NULL)
            return (0);
      /*
       * The snapshot creation could fail, but that would cause an
       * incorrect FALSE return, which would only result in an
       * overestimation of the amount of space that an operation would
       * consume, which is OK.
       *
       * There's also a small window where we could miss a pending
       * snapshot, because we could set the sync task in the quiescing
       * phase.  So this should only be used as a guess.
       */
      if (ds->ds_trysnap_txg >
          spa_last_synced_txg(ds->ds_dir->dd_pool->dp_spa))
            trysnap = ds->ds_trysnap_txg;
      return (MAX(ds->ds_phys->ds_prev_snap_txg, trysnap));
}

boolean_t
dsl_dataset_block_freeable(dsl_dataset_t *ds, uint64_t blk_birth)
{
      return (blk_birth > dsl_dataset_prev_snap_txg(ds));
}

/* ARGSUSED */
static void
dsl_dataset_evict(dmu_buf_t *db, void *dsv)
{
      dsl_dataset_t *ds = 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_prev) {
            dsl_dataset_drop_ref(ds->ds_prev, ds);
            ds->ds_prev = NULL;
      }

      bplist_close(&ds->ds_deadlist);
      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_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));
}

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

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

      err = dmu_bonus_hold(mos, ds->ds_dir->dd_phys->dd_head_dataset_obj,
          FTAG, &headdbuf);
      if (err)
            return (err);
      headphys = headdbuf->db_data;
      err = zap_value_search(dp->dp_meta_objset,
          headphys->ds_snapnames_zapobj, ds->ds_object, 0, ds->ds_snapname);
      dmu_buf_rele(headdbuf, FTAG);
      return (err);
}

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

      if (ds->ds_phys->ds_flags & DS_FLAG_CI_DATASET)
            mt = MT_FIRST;
      else
            mt = MT_EXACT;

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

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

      if (ds->ds_phys->ds_flags & DS_FLAG_CI_DATASET)
            mt = MT_FIRST;
      else
            mt = MT_EXACT;

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

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

      ASSERT(RW_LOCK_HELD(&dp->dp_config_rwlock) ||
          dsl_pool_sync_context(dp));

      err = dmu_bonus_hold(mos, dsobj, tag, &dbuf);
      if (err)
            return (err);
      ds = dmu_buf_get_user(dbuf);
      if (ds == NULL) {
            dsl_dataset_t *winner;

            ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
            ds->ds_dbuf = dbuf;
            ds->ds_object = dsobj;
            ds->ds_phys = dbuf->db_data;

            mutex_init(&ds->ds_lock, 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);
            cv_init(&ds->ds_exclusive_cv, NULL, CV_DEFAULT, NULL);

            err = bplist_open(&ds->ds_deadlist,
                mos, ds->ds_phys->ds_deadlist_obj);
            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_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));
                  dmu_buf_rele(dbuf, tag);
                  return (err);
            }

            if (!dsl_dataset_is_snapshot(ds)) {
                  ds->ds_snapname[0] = '\0';
                  if (ds->ds_phys->ds_prev_snap_obj) {
                        err = dsl_dataset_get_ref(dp,
                            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 && !dsl_dataset_is_snapshot(ds)) {
                  /*
                   * In sync context, we're called with either no lock
                   * or with the write lock.  If we're not syncing,
                   * we're always called with the read lock held.
                   */
                  boolean_t need_lock =
                      !RW_WRITE_HELD(&dp->dp_config_rwlock) &&
                      dsl_pool_sync_context(dp);

                  if (need_lock)
                        rw_enter(&dp->dp_config_rwlock, RW_READER);

                  err = dsl_prop_get_ds(ds,
                      "refreservation", sizeof (uint64_t), 1,
                      &ds->ds_reserved, NULL);
                  if (err == 0) {
                        err = dsl_prop_get_ds(ds,
                            "refquota", sizeof (uint64_t), 1,
                            &ds->ds_quota, NULL);
                  }

                  if (need_lock)
                        rw_exit(&dp->dp_config_rwlock);
            } else {
                  ds->ds_reserved = ds->ds_quota = 0;
            }

            if (err == 0) {
                  winner = dmu_buf_set_user_ie(dbuf, ds, &ds->ds_phys,
                      dsl_dataset_evict);
            }
            if (err || winner) {
                  bplist_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_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));
                  if (err) {
                        dmu_buf_rele(dbuf, tag);
                        return (err);
                  }
                  ds = winner;
            } else {
                  ds->ds_fsid_guid =
                      unique_insert(ds->ds_phys->ds_fsid_guid);
            }
      }
      ASSERT3P(ds->ds_dbuf, ==, dbuf);
      ASSERT3P(ds->ds_phys, ==, dbuf->db_data);
      ASSERT(ds->ds_phys->ds_prev_snap_obj != 0 ||
          spa_version(dp->dp_spa) < SPA_VERSION_ORIGIN ||
          dp->dp_origin_snap == NULL || ds == dp->dp_origin_snap);
      mutex_enter(&ds->ds_lock);
      if (!dsl_pool_sync_context(dp) && DSL_DATASET_IS_DESTROYED(ds)) {
            mutex_exit(&ds->ds_lock);
            dmu_buf_rele(ds->ds_dbuf, tag);
            return (ENOENT);
      }
      mutex_exit(&ds->ds_lock);
      *dsp = ds;
      return (0);
}

static int
dsl_dataset_hold_ref(dsl_dataset_t *ds, void *tag)
{
      dsl_pool_t *dp = ds->ds_dir->dd_pool;

      /*
       * In syncing context we don't want the rwlock lock: there
       * may be an existing writer waiting for sync phase to
       * finish.  We don't need to worry about such writers, since
       * sync phase is single-threaded, so the writer can't be
       * doing anything while we are active.
       */
      if (dsl_pool_sync_context(dp)) {
            ASSERT(!DSL_DATASET_IS_DESTROYED(ds));
            return (0);
      }

      /*
       * Normal users will hold the ds_rwlock as a READER until they
       * are finished (i.e., call dsl_dataset_rele()).  "Owners" will
       * drop their READER lock after they set the ds_owner field.
       *
       * If the dataset is being destroyed, the destroy thread will
       * obtain a WRITER lock for exclusive access after it's done its
       * open-context work and then change the ds_owner to
       * dsl_reaper once destruction is assured.  So threads
       * may block here temporarily, until the "destructability" of
       * the dataset is determined.
       */
      ASSERT(!RW_WRITE_HELD(&dp->dp_config_rwlock));
      mutex_enter(&ds->ds_lock);
      while (!rw_tryenter(&ds->ds_rwlock, RW_READER)) {
            rw_exit(&dp->dp_config_rwlock);
            cv_wait(&ds->ds_exclusive_cv, &ds->ds_lock);
            if (DSL_DATASET_IS_DESTROYED(ds)) {
                  mutex_exit(&ds->ds_lock);
                  dsl_dataset_drop_ref(ds, tag);
                  rw_enter(&dp->dp_config_rwlock, RW_READER);
                  return (ENOENT);
            }
            rw_enter(&dp->dp_config_rwlock, RW_READER);
      }
      mutex_exit(&ds->ds_lock);
      return (0);
}

int
dsl_dataset_hold_obj(dsl_pool_t *dp, uint64_t dsobj, void *tag,
    dsl_dataset_t **dsp)
{
      int err = dsl_dataset_get_ref(dp, dsobj, tag, dsp);

      if (err)
            return (err);
      return (dsl_dataset_hold_ref(*dsp, tag));
}

int
dsl_dataset_own_obj(dsl_pool_t *dp, uint64_t dsobj, int flags, void *owner,
    dsl_dataset_t **dsp)
{
      int err = dsl_dataset_hold_obj(dp, dsobj, owner, dsp);

      ASSERT(DS_MODE_TYPE(flags) != DS_MODE_USER);

      if (err)
            return (err);
      if (!dsl_dataset_tryown(*dsp, DS_MODE_IS_INCONSISTENT(flags), owner)) {
            dsl_dataset_rele(*dsp, owner);
            *dsp = NULL;
            return (EBUSY);
      }
      return (0);
}

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

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

      dp = dd->dd_pool;
      obj = dd->dd_phys->dd_head_dataset_obj;
      rw_enter(&dp->dp_config_rwlock, RW_READER);
      if (obj)
            err = dsl_dataset_get_ref(dp, obj, tag, dsp);
      else
            err = ENOENT;
      if (err)
            goto out;

      err = dsl_dataset_hold_ref(*dsp, tag);

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

            if (*snapname++ != '@') {
                  dsl_dataset_rele(*dsp, tag);
                  err = ENOENT;
                  goto out;
            }

            dprintf("looking for snapshot '%s'\n", snapname);
            err = dsl_dataset_snap_lookup(*dsp, snapname, &obj);
            if (err == 0)
                  err = dsl_dataset_get_ref(dp, obj, tag, &ds);
            dsl_dataset_rele(*dsp, tag);

            ASSERT3U((err == 0), ==, (ds != NULL));

            if (ds) {
                  mutex_enter(&ds->ds_lock);
                  if (ds->ds_snapname[0] == 0)
                        (void) strlcpy(ds->ds_snapname, snapname,
                            sizeof (ds->ds_snapname));
                  mutex_exit(&ds->ds_lock);
                  err = dsl_dataset_hold_ref(ds, tag);
                  *dsp = err ? NULL : ds;
            }
      }
out:
      rw_exit(&dp->dp_config_rwlock);
      dsl_dir_close(dd, FTAG);
      return (err);
}

int
dsl_dataset_own(const char *name, int flags, void *owner, dsl_dataset_t **dsp)
{
      int err = dsl_dataset_hold(name, owner, 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);
            return (EBUSY);
      }
      return (0);
}

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

static int
dsl_dataset_namelen(dsl_dataset_t *ds)
{
      int result;

      if (ds == NULL) {
            result = 3; /* "mos" */
      } else {
            result = dsl_dir_namelen(ds->ds_dir);
            VERIFY(0 == dsl_dataset_get_snapname(ds));
            if (ds->ds_snapname[0]) {
                  ++result;   /* adding one for the @-sign */
                  if (!MUTEX_HELD(&ds->ds_lock)) {
                        mutex_enter(&ds->ds_lock);
                        result += strlen(ds->ds_snapname);
                        mutex_exit(&ds->ds_lock);
                  } else {
                        result += strlen(ds->ds_snapname);
                  }
            }
      }

      return (result);
}

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

void
dsl_dataset_rele(dsl_dataset_t *ds, void *tag)
{
      if (!dsl_pool_sync_context(ds->ds_dir->dd_pool)) {
            rw_exit(&ds->ds_rwlock);
      }
      dsl_dataset_drop_ref(ds, tag);
}

void
dsl_dataset_disown(dsl_dataset_t *ds, void *owner)
{
      ASSERT((ds->ds_owner == owner && ds->ds_dbuf) ||
          (DSL_DATASET_IS_DESTROYED(ds) && ds->ds_dbuf == NULL));

      mutex_enter(&ds->ds_lock);
      ds->ds_owner = NULL;
      if (RW_WRITE_HELD(&ds->ds_rwlock)) {
            rw_exit(&ds->ds_rwlock);
            cv_broadcast(&ds->ds_exclusive_cv);
      }
      mutex_exit(&ds->ds_lock);
      if (ds->ds_dbuf)
            dsl_dataset_drop_ref(ds, owner);
      else
            dsl_dataset_evict(ds->ds_dbuf, ds);
}

boolean_t
dsl_dataset_tryown(dsl_dataset_t *ds, boolean_t inconsistentok, void *owner)
{
      boolean_t gotit = FALSE;

      mutex_enter(&ds->ds_lock);
      if (ds->ds_owner == NULL &&
          (!DS_IS_INCONSISTENT(ds) || inconsistentok)) {
            ds->ds_owner = owner;
            if (!dsl_pool_sync_context(ds->ds_dir->dd_pool))
                  rw_exit(&ds->ds_rwlock);
            gotit = TRUE;
      }
      mutex_exit(&ds->ds_lock);
      return (gotit);
}

void
dsl_dataset_make_exclusive(dsl_dataset_t *ds, void *owner)
{
      ASSERT3P(owner, ==, ds->ds_owner);
      if (!RW_WRITE_HELD(&ds->ds_rwlock))
            rw_enter(&ds->ds_rwlock, RW_WRITER);
}

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

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

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

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

      if (origin) {
            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_compressed_bytes =
                origin->ds_phys->ds_compressed_bytes;
            dsphys->ds_uncompressed_bytes =
                origin->ds_phys->ds_uncompressed_bytes;
            dsphys->ds_bp = origin->ds_phys->ds_bp;
            dsphys->ds_flags |= origin->ds_phys->ds_flags;

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

            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 =
                            zap_create(mos,
                            DMU_OT_NEXT_CLONES, DMU_OT_NONE, 0, tx);
                  }
                  VERIFY(0 == zap_add_int(mos,
                      origin->ds_phys->ds_next_clones_obj,
                      dsobj, tx));
            }

            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_UNIQUE_ACCURATE)
            dsphys->ds_flags |= DS_FLAG_UNIQUE_ACCURATE;

      dmu_buf_rele(dbuf, FTAG);

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

      return (dsobj);
}

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

      ASSERT(lastname[0] != '@');

      ddobj = dsl_dir_create_sync(dp, pdd, lastname, tx);
      VERIFY(0 == dsl_dir_open_obj(dp, ddobj, lastname, FTAG, &dd));

      dsobj = dsl_dataset_create_sync_dd(dd, origin, flags, tx);

      dsl_deleg_set_create_perms(dd, tx, cr);

      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;

      (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);
      }
      return (err);
}

/*
 * Destroy 'snapname' in all descendants of 'fsname'.
 */
#pragma weak dmu_snapshots_destroy = dsl_snapshots_destroy
int
dsl_snapshots_destroy(char *fsname, char *snapname)
{
      int err;
      struct destroyarg da;
      dsl_sync_task_t *dst;
      spa_t *spa;

      err = spa_open(fsname, &spa, FTAG);
      if (err)
            return (err);
      da.dstg = dsl_sync_task_group_create(spa_get_dsl(spa));
      da.snapname = snapname;
      da.failed = fsname;

      err = dmu_objset_find(fsname,
          dsl_snapshot_destroy_one, &da, DS_FIND_CHILDREN);

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

      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_disown(ds, da.dstg);
      }

      dsl_sync_task_group_destroy(da.dstg);
      spa_close(spa, FTAG);
      return (err);
}

/*
 * ds must be opened as OWNER.  On return (whether successful or not),
 * ds will be closed and caller can no longer dereference it.
 */
int
dsl_dataset_destroy(dsl_dataset_t *ds, void *tag)
{
      int err;
      dsl_sync_task_group_t *dstg;
      objset_t *os;
      dsl_dir_t *dd;
      uint64_t obj;

      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;
            }
            err = dsl_sync_task_do(ds->ds_dir->dd_pool,
                dsl_dataset_destroy_check, dsl_dataset_destroy_sync,
                ds, tag, 0);
            goto out;
      }

      dd = ds->ds_dir;

      /*
       * 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;

      err = dmu_objset_open_ds(ds, DMU_OST_ANY, &os);
      if (err)
            goto out;

      /*
       * 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().
             */
            (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);

      /*
       * 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;

            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);
      }

      /*
       * 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 it is successful, dsl_dir_destroy_sync will close the dd */
      if (err)
            dsl_dir_close(dd, FTAG);
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)
{
      return (&ds->ds_phys->ds_bp);
}

void
dsl_dataset_set_blkptr(dsl_dataset_t *ds, blkptr_t *bp, dmu_tx_t *tx)
{
      ASSERT(dmu_tx_is_syncing(tx));
      /* If it's the meta-objset, set dp_meta_rootbp */
      if (ds == NULL) {
            tx->tx_pool->dp_meta_rootbp = *bp;
      } else {
            dmu_buf_will_dirty(ds->ds_dbuf, tx);
            ds->ds_phys->ds_bp = *bp;
      }
}

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

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

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

      ASSERT(ds->ds_user_ptr != NULL);

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

      dp = ds->ds_dir->dd_pool;

      if (txg_list_add(&dp->dp_dirty_datasets, ds, tx->tx_txg) == 0) {
            /* up the hold count until we can be written out */
            dmu_buf_add_ref(ds->ds_dbuf, ds);
      }
}

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

      if (ds->ds_phys->ds_prev_snap_obj != 0)
            mrs_used = ds->ds_prev->ds_phys->ds_used_bytes;
      else
            mrs_used = 0;

      VERIFY(0 == bplist_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);

      if (!DS_UNIQUE_IS_ACCURATE(ds) &&
          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)
{
      struct killarg *ka = arg;

      if (bp == NULL)
            return (0);

      if ((zb->zb_level == -1ULL && zb->zb_blkid != 0) ||
          (zb->zb_object != 0 && dnp == 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));
      } else {
            ASSERT3U(bp->blk_birth, >, ka->ds->ds_phys->ds_prev_snap_txg);
            (void) dsl_dataset_block_kill(ka->ds, bp, ka->zio, ka->tx);
      }

      return (0);
}

/* ARGSUSED */
static int
dsl_dataset_rollback_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);

      /*
       * This must not be a snapshot.
       */
      if (ds->ds_phys->ds_next_snap_obj != 0)
            return (EINVAL);

      /*
       * If we made changes this txg, traverse_dataset won't find
       * them.  Try again.
       */
      if (ds->ds_phys->ds_bp.blk_birth >= tx->tx_txg)
            return (EAGAIN);

      return (0);
}

/* ARGSUSED */
static void
dsl_dataset_rollback_sync(void *arg1, void *arg2, cred_t *cr, 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;

      dmu_buf_will_dirty(ds->ds_dbuf, tx);

      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;

            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);
      }

      /* 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));

      {
            /*
             * Free blkptrs that we gave birth to - this covers
             * claimed but not played log blocks too.
             */
            zio_t *zio;
            struct killarg ka;

            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);
      }

      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.
       */
      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_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);
}

/* ARGSUSED */
int
dsl_dataset_destroy_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;

      /* 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);

      /*
       * 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);

      /*
       * If we made changes this txg, traverse_dsl_dataset won't find
       * them.  Try again.
       */
      if (ds->ds_phys->ds_bp.blk_birth >= tx->tx_txg)
            return (EAGAIN);

      /* XXX we should do some i/o error checking... */
      return (0);
}

struct refsarg {
      kmutex_t lock;
      boolean_t gone;
      kcondvar_t cv;
};

/* ARGSUSED */
static void
dsl_dataset_refs_gone(dmu_buf_t *db, void *argv)
{
      struct refsarg *arg = argv;

      mutex_enter(&arg->lock);
      arg->gone = TRUE;
      cv_signal(&arg->cv);
      mutex_exit(&arg->lock);
}

static void
dsl_dataset_drain_refs(dsl_dataset_t *ds, void *tag)
{
      struct refsarg arg;

      mutex_init(&arg.lock, NULL, MUTEX_DEFAULT, NULL);
      cv_init(&arg.cv, NULL, CV_DEFAULT, NULL);
      arg.gone = FALSE;
      (void) dmu_buf_update_user(ds->ds_dbuf, ds, &arg, &ds->ds_phys,
          dsl_dataset_refs_gone);
      dmu_buf_rele(ds->ds_dbuf, tag);
      mutex_enter(&arg.lock);
      while (!arg.gone)
            cv_wait(&arg.cv, &arg.lock);
      ASSERT(arg.gone);
      mutex_exit(&arg.lock);
      ds->ds_dbuf = NULL;
      ds->ds_phys = NULL;
      mutex_destroy(&arg.lock);
      cv_destroy(&arg.cv);
}

void
dsl_dataset_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      zio_t *zio;
      int err;
      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;
      uint64_t obj;

      ASSERT(ds->ds_owner);
      ASSERT3U(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);

      /* signal any waiters that this dataset is going away */
      mutex_enter(&ds->ds_lock);
      ds->ds_owner = dsl_reaper;
      cv_broadcast(&ds->ds_exclusive_cv);
      mutex_exit(&ds->ds_lock);

      /* 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);
      }

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

      dsl_pool_ds_destroyed(ds, tx);

      obj = ds->ds_object;

      if (ds->ds_phys->ds_prev_snap_obj != 0) {
            if (ds->ds_prev) {
                  ds_prev = ds->ds_prev;
            } else {
                  VERIFY(0 == dsl_dataset_hold_obj(dp,
                      ds->ds_phys->ds_prev_snap_obj, FTAG, &ds_prev));
            }
            after_branch_point =
                (ds_prev->ds_phys->ds_next_snap_obj != obj);

            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));
                  if (ds->ds_phys->ds_next_snap_obj != 0) {
                        VERIFY(0 == zap_add_int(mos,
                            ds_prev->ds_phys->ds_next_clones_obj,
                            ds->ds_phys->ds_next_snap_obj, tx));
                  }
            }
            if (after_branch_point &&
                ds->ds_phys->ds_next_snap_obj == 0) {
                  /* This clone is toast. */
                  ASSERT(ds_prev->ds_phys->ds_num_children > 1);
                  ds_prev->ds_phys->ds_num_children--;
            } 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;
            dsl_dataset_t *ds_next;
            uint64_t itor = 0;
            uint64_t old_unique;
            int64_t used = 0, compressed = 0, uncompressed = 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);

            dmu_buf_will_dirty(ds_next->ds_dbuf, tx);
            ds_next->ds_phys->ds_prev_snap_obj =
                ds->ds_phys->ds_prev_snap_obj;
            ds_next->ds_phys->ds_prev_snap_txg =
                ds->ds_phys->ds_prev_snap_txg;
            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);

            /* change snapused */
            dsl_dir_diduse_space(ds->ds_dir, DD_USED_SNAP,
                -used, -compressed, -uncompressed, tx);

            /* free next's deadlist */
            bplist_close(&ds_next->ds_deadlist);
            bplist_destroy(mos, ds_next->ds_phys->ds_deadlist_obj, 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 (ds_next->ds_phys->ds_next_snap_obj != 0) {
                  /*
                   * Update next's unique to include blocks which
                   * were previously shared by only this snapshot
                   * and it.  Those blocks will be born after the
                   * prev snap and before this snap, and will have
                   * 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,
                      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);
                  ASSERT3P(ds_next->ds_prev, ==, NULL);
            } else {
                  ASSERT3P(ds_next->ds_prev, ==, ds);
                  dsl_dataset_drop_ref(ds_next->ds_prev, ds_next);
                  ds_next->ds_prev = NULL;
                  if (ds_prev) {
                        VERIFY(0 == dsl_dataset_get_ref(dp,
                            ds->ds_phys->ds_prev_snap_obj,
                            ds_next, &ds_next->ds_prev));
                  }

                  dsl_dataset_recalc_head_uniq(ds_next);

                  /*
                   * Reduce the amount of our unconsmed refreservation
                   * being charged to our parent by the amount of
                   * new unique data we have gained.
                   */
                  if (old_unique < ds_next->ds_reserved) {
                        int64_t mrsdelta;
                        uint64_t new_unique =
                            ds_next->ds_phys->ds_unique_bytes;

                        ASSERT(old_unique <= new_unique);
                        mrsdelta = MIN(new_unique - old_unique,
                            ds_next->ds_reserved - old_unique);
                        dsl_dir_diduse_space(ds->ds_dir,
                            DD_USED_REFRSRV, -mrsdelta, 0, 0, tx);
                  }
            }
            dsl_dataset_rele(ds_next, FTAG);
      } else {
            /*
             * 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);
            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);
      }

      err = zio_wait(zio);
      ASSERT3U(err, ==, 0);

      if (ds->ds_dir->dd_phys->dd_head_dataset_obj == ds->ds_object) {
            /* Erase the link in the dir */
            dmu_buf_will_dirty(ds->ds_dir->dd_dbuf, tx);
            ds->ds_dir->dd_phys->dd_head_dataset_obj = 0;
            ASSERT(ds->ds_phys->ds_snapnames_zapobj != 0);
            err = zap_destroy(mos, ds->ds_phys->ds_snapnames_zapobj, tx);
            ASSERT(err == 0);
      } else {
            /* remove from snapshot namespace */
            dsl_dataset_t *ds_head;
            ASSERT(ds->ds_phys->ds_snapnames_zapobj == 0);
            VERIFY(0 == dsl_dataset_hold_obj(dp,
                ds->ds_dir->dd_phys->dd_head_dataset_obj, FTAG, &ds_head));
            VERIFY(0 == dsl_dataset_get_snapname(ds));
#ifdef ZFS_DEBUG
            {
                  uint64_t val;

                  err = dsl_dataset_snap_lookup(ds_head,
                      ds->ds_snapname, &val);
                  ASSERT3U(err, ==, 0);
                  ASSERT3U(val, ==, obj);
            }
#endif
            err = dsl_dataset_snap_remove(ds_head, ds->ds_snapname, tx);
            ASSERT(err == 0);
            dsl_dataset_rele(ds_head, FTAG);
      }

      if (ds_prev && ds->ds_prev != ds_prev)
            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);

      if (ds->ds_phys->ds_next_clones_obj != 0) {
            uint64_t count;
            ASSERT(0 == zap_count(mos,
                ds->ds_phys->ds_next_clones_obj, &count) && count == 0);
            VERIFY(0 == dmu_object_free(mos,
                ds->ds_phys->ds_next_clones_obj, tx));
      }
      if (ds->ds_phys->ds_props_obj != 0)
            VERIFY(0 == zap_destroy(mos, ds->ds_phys->ds_props_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));
}

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

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

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

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

      return (0);
}

/* ARGSUSED */
int
dsl_dataset_snapshot_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      const char *snapname = arg2;
      int err;
      uint64_t value;

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

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

      /*
       * Check that the dataset's name is not too long.  Name consists
       * of the dataset's length + 1 for the @-sign + snapshot name's length
       */
      if (dsl_dataset_namelen(ds) + 1 + strlen(snapname) >= MAXNAMELEN)
            return (ENAMETOOLONG);

      err = dsl_dataset_snapshot_reserve_space(ds, tx);
      if (err)
            return (err);

      ds->ds_trysnap_txg = tx->tx_txg;
      return (0);
}

void
dsl_dataset_snapshot_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      const char *snapname = arg2;
      dsl_pool_t *dp = ds->ds_dir->dd_pool;
      dmu_buf_t *dbuf;
      dsl_dataset_phys_t *dsphys;
      uint64_t dsobj, crtxg;
      objset_t *mos = dp->dp_meta_objset;
      int err;

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

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

      dsobj = dmu_object_alloc(mos, DMU_OT_DSL_DATASET, 0,
          DMU_OT_DSL_DATASET, sizeof (dsl_dataset_phys_t), tx);
      VERIFY(0 == dmu_bonus_hold(mos, dsobj, FTAG, &dbuf));
      dmu_buf_will_dirty(dbuf, tx);
      dsphys = dbuf->db_data;
      bzero(dsphys, sizeof (dsl_dataset_phys_t));
      dsphys->ds_dir_obj = ds->ds_dir->dd_object;
      dsphys->ds_fsid_guid = unique_create();
      (void) random_get_pseudo_bytes((void*)&dsphys->ds_guid,
          sizeof (dsphys->ds_guid));
      dsphys->ds_prev_snap_obj = ds->ds_phys->ds_prev_snap_obj;
      dsphys->ds_prev_snap_txg = ds->ds_phys->ds_prev_snap_txg;
      dsphys->ds_next_snap_obj = ds->ds_object;
      dsphys->ds_num_children = 1;
      dsphys->ds_creation_time = gethrestime_sec();
      dsphys->ds_creation_txg = crtxg;
      dsphys->ds_deadlist_obj = ds->ds_phys->ds_deadlist_obj;
      dsphys->ds_used_bytes = ds->ds_phys->ds_used_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;
      dsphys->ds_bp = ds->ds_phys->ds_bp;
      dmu_buf_rele(dbuf, FTAG);

      ASSERT3U(ds->ds_prev != 0, ==, ds->ds_phys->ds_prev_snap_obj != 0);
      if (ds->ds_prev) {
            uint64_t next_clones_obj =
                ds->ds_prev->ds_phys->ds_next_clones_obj;
            ASSERT(ds->ds_prev->ds_phys->ds_next_snap_obj ==
                ds->ds_object ||
                ds->ds_prev->ds_phys->ds_num_children > 1);
            if (ds->ds_prev->ds_phys->ds_next_snap_obj == ds->ds_object) {
                  dmu_buf_will_dirty(ds->ds_prev->ds_dbuf, tx);
                  ASSERT3U(ds->ds_phys->ds_prev_snap_txg, ==,
                      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));
                  VERIFY3U(0, ==, zap_add_int(mos,
                      next_clones_obj, dsobj, tx));
            }
      }

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

      bplist_close(&ds->ds_deadlist);
      dmu_buf_will_dirty(ds->ds_dbuf, 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);

      if (ds->ds_prev)
            dsl_dataset_drop_ref(ds->ds_prev, ds);
      VERIFY(0 == dsl_dataset_get_ref(dp,
          ds->ds_phys->ds_prev_snap_obj, ds, &ds->ds_prev));

      dsl_pool_ds_snapshotted(ds, tx);

      spa_history_internal_log(LOG_DS_SNAPSHOT, dp->dp_spa, tx, cr,
          "dataset = %llu", dsobj);
}

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_phys->ds_next_snap_obj == 0);

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

void
dsl_dataset_stats(dsl_dataset_t *ds, nvlist_t *nv)
{
      uint64_t refd, avail, uobjs, aobjs;

      dsl_dir_stats(ds->ds_dir, nv);

      dsl_dataset_space(ds, &refd, &avail, &uobjs, &aobjs);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_AVAILABLE, avail);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFERENCED, refd);

      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_CREATION,
          ds->ds_phys->ds_creation_time);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_CREATETXG,
          ds->ds_phys->ds_creation_txg);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFQUOTA,
          ds->ds_quota);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_REFRESERVATION,
          ds->ds_reserved);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_GUID,
          ds->ds_phys->ds_guid);

      if (ds->ds_phys->ds_next_snap_obj) {
            /*
             * This is a snapshot; override the dd's space used with
             * our unique space and compression ratio.
             */
            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));
      }
}

void
dsl_dataset_fast_stat(dsl_dataset_t *ds, dmu_objset_stats_t *stat)
{
      stat->dds_creation_txg = ds->ds_phys->ds_creation_txg;
      stat->dds_inconsistent = ds->ds_phys->ds_flags & DS_FLAG_INCONSISTENT;
      stat->dds_guid = ds->ds_phys->ds_guid;
      if (ds->ds_phys->ds_next_snap_obj) {
            stat->dds_is_snapshot = B_TRUE;
            stat->dds_num_clones = ds->ds_phys->ds_num_children - 1;
      } else {
            stat->dds_is_snapshot = B_FALSE;
            stat->dds_num_clones = 0;
      }

      /* clone origin is really a dsl_dir thing... */
      rw_enter(&ds->ds_dir->dd_pool->dp_config_rwlock, RW_READER);
      if (dsl_dir_is_clone(ds->ds_dir)) {
            dsl_dataset_t *ods;

            VERIFY(0 == dsl_dataset_get_ref(ds->ds_dir->dd_pool,
                ds->ds_dir->dd_phys->dd_origin_obj, FTAG, &ods));
            dsl_dataset_name(ods, stat->dds_origin);
            dsl_dataset_drop_ref(ods, FTAG);
      } else {
            stat->dds_origin[0] = '\0';
      }
      rw_exit(&ds->ds_dir->dd_pool->dp_config_rwlock);
}

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

void
dsl_dataset_space(dsl_dataset_t *ds,
    uint64_t *refdbytesp, uint64_t *availbytesp,
    uint64_t *usedobjsp, uint64_t *availobjsp)
{
      *refdbytesp = ds->ds_phys->ds_used_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;
      if (ds->ds_quota != 0) {
            /*
             * Adjust available bytes according to refquota
             */
            if (*refdbytesp < ds->ds_quota)
                  *availbytesp = MIN(*availbytesp,
                      ds->ds_quota - *refdbytesp);
            else
                  *availbytesp = 0;
      }
      *usedobjsp = ds->ds_phys->ds_bp.blk_fill;
      *availobjsp = DN_MAX_OBJECT - *usedobjsp;
}

boolean_t
dsl_dataset_modified_since_lastsnap(dsl_dataset_t *ds)
{
      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);
      return (B_FALSE);
}

/* ARGSUSED */
static int
dsl_dataset_snapshot_rename_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      char *newsnapname = arg2;
      dsl_dir_t *dd = ds->ds_dir;
      dsl_dataset_t *hds;
      uint64_t val;
      int err;

      err = dsl_dataset_hold_obj(dd->dd_pool,
          dd->dd_phys->dd_head_dataset_obj, FTAG, &hds);
      if (err)
            return (err);

      /* new name better not be in use */
      err = dsl_dataset_snap_lookup(hds, newsnapname, &val);
      dsl_dataset_rele(hds, FTAG);

      if (err == 0)
            err = EEXIST;
      else if (err == ENOENT)
            err = 0;

      /* dataset name + 1 for the "@" + the new snapshot name must fit */
      if (dsl_dir_namelen(ds->ds_dir) + 1 + strlen(newsnapname) >= MAXNAMELEN)
            err = ENAMETOOLONG;

      return (err);
}

static void
dsl_dataset_snapshot_rename_sync(void *arg1, void *arg2,
    cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *ds = arg1;
      const char *newsnapname = arg2;
      dsl_dir_t *dd = ds->ds_dir;
      objset_t *mos = dd->dd_pool->dp_meta_objset;
      dsl_dataset_t *hds;
      int err;

      ASSERT(ds->ds_phys->ds_next_snap_obj != 0);

      VERIFY(0 == dsl_dataset_hold_obj(dd->dd_pool,
          dd->dd_phys->dd_head_dataset_obj, FTAG, &hds));

      VERIFY(0 == dsl_dataset_get_snapname(ds));
      err = dsl_dataset_snap_remove(hds, ds->ds_snapname, tx);
      ASSERT3U(err, ==, 0);
      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);

      spa_history_internal_log(LOG_DS_RENAME, dd->dd_pool->dp_spa, tx,
          cr, "dataset = %llu", ds->ds_object);
      dsl_dataset_rele(hds, FTAG);
}

struct renamesnaparg {
      dsl_sync_task_group_t *dstg;
      char failed[MAXPATHLEN];
      char *oldsnap;
      char *newsnap;
};

static int
dsl_snapshot_rename_one(char *name, void *arg)
{
      struct renamesnaparg *ra = arg;
      dsl_dataset_t *ds = NULL;
      char *cp;
      int err;

      cp = name + strlen(name);
      *cp = '@';
      (void) strcpy(cp + 1, ra->oldsnap);

      /*
       * 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);
      }

#ifdef _KERNEL
      /*
       * For all filesystems undergoing rename, we'll need to unmount it.
       */
      (void) zfs_unmount_snap(name, 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);
      }

      dsl_sync_task_create(ra->dstg, dsl_dataset_snapshot_rename_check,
          dsl_dataset_snapshot_rename_sync, ds, ra->newsnap, 0);

      return (0);
}

static int
dsl_recursive_rename(char *oldname, const char *newname)
{
      int err;
      struct renamesnaparg *ra;
      dsl_sync_task_t *dst;
      spa_t *spa;
      char *cp, *fsname = spa_strdup(oldname);
      int len = strlen(oldname);

      /* truncate the snapshot name to get the fsname */
      cp = strchr(fsname, '@');
      *cp = '\0';

      err = spa_open(fsname, &spa, FTAG);
      if (err) {
            kmem_free(fsname, len + 1);
            return (err);
      }
      ra = kmem_alloc(sizeof (struct renamesnaparg), KM_SLEEP);
      ra->dstg = dsl_sync_task_group_create(spa_get_dsl(spa));

      ra->oldsnap = strchr(oldname, '@') + 1;
      ra->newsnap = strchr(newname, '@') + 1;
      *ra->failed = '\0';

      err = dmu_objset_find(fsname, dsl_snapshot_rename_one, ra,
          DS_FIND_CHILDREN);
      kmem_free(fsname, len + 1);

      if (err == 0) {
            err = dsl_sync_task_group_wait(ra->dstg);
      }

      for (dst = list_head(&ra->dstg->dstg_tasks); dst;
          dst = list_next(&ra->dstg->dstg_tasks, dst)) {
            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);
            }
            dsl_dataset_rele(ds, ra->dstg);
      }

      if (err)
            (void) strcpy(oldname, ra->failed);

      dsl_sync_task_group_destroy(ra->dstg);
      kmem_free(ra, sizeof (struct renamesnaparg));
      spa_close(spa, FTAG);
      return (err);
}

static int
dsl_valid_rename(char *oldname, void *arg)
{
      int delta = *(int *)arg;

      if (strlen(oldname) + delta >= MAXNAMELEN)
            return (ENAMETOOLONG);

      return (0);
}

#pragma weak dmu_objset_rename = dsl_dataset_rename
int
dsl_dataset_rename(char *oldname, const char *newname, boolean_t recursive)
{
      dsl_dir_t *dd;
      dsl_dataset_t *ds;
      const char *tail;
      int err;

      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);

            /* if we're growing, validate child name lengths */
            if (delta > 0)
                  err = dmu_objset_find(oldname, dsl_valid_rename,
                      &delta, DS_FIND_CHILDREN | DS_FIND_SNAPSHOTS);

            if (!err)
                  err = dsl_dir_rename(dd, newname);
            dsl_dir_close(dd, FTAG);
            return (err);
      }
      if (tail[0] != '@') {
            /* the name ended in a nonexistant component */
            dsl_dir_close(dd, FTAG);
            return (ENOENT);
      }

      dsl_dir_close(dd, FTAG);

      /* new name must be snapshot in same filesystem */
      tail = strchr(newname, '@');
      if (tail == NULL)
            return (EINVAL);
      tail++;
      if (strncmp(oldname, newname, tail - newname) != 0)
            return (EXDEV);

      if (recursive) {
            err = dsl_recursive_rename(oldname, newname);
      } else {
            err = dsl_dataset_hold(oldname, FTAG, &ds);
            if (err)
                  return (err);

            err = dsl_sync_task_do(ds->ds_dir->dd_pool,
                dsl_dataset_snapshot_rename_check,
                dsl_dataset_snapshot_rename_sync, ds, (char *)tail, 1);

            dsl_dataset_rele(ds, FTAG);
      }

      return (err);
}

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

struct promotearg {
      list_t shared_snaps, origin_snaps, clone_snaps;
      dsl_dataset_t *origin_origin, *origin_head;
      uint64_t used, comp, uncomp, unique, cloneusedsnap, originusedsnap;
};

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)
{
      dsl_dataset_t *hds = arg1;
      struct promotearg *pa = arg2;
      struct promotenode *snap = list_head(&pa->shared_snaps);
      dsl_dataset_t *origin_ds = snap->ds;
      int err;

      /* Check that it is a real clone */
      if (!dsl_dir_is_clone(hds->ds_dir))
            return (EINVAL);

      /* Since this is so expensive, don't do the preliminary check */
      if (!dmu_tx_is_syncing(tx))
            return (0);

      if (hds->ds_phys->ds_flags & DS_FLAG_NOPROMOTE)
            return (EXDEV);

      /* 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);

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

            /* 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 != ENOENT)
                  return (err);

            /* 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);
            pa->used += dlused;
            pa->comp += dlcomp;
            pa->uncomp += dluncomp;
      }

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

      /* Check that there is enough space here */
      err = dsl_dir_transfer_possible(origin_ds->ds_dir, hds->ds_dir,
          pa->used);
      if (err)
            return (err);

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

            /*
             * 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()
             * 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);
            if (err)
                  return (err);

            err = snaplist_space(&pa->clone_snaps,
                snap->ds->ds_origin_txg, &space);
            if (err)
                  return (err);
            pa->cloneusedsnap += space;
      }
      if (origin_ds->ds_dir->dd_phys->dd_flags & DD_FLAG_USED_BREAKDOWN) {
            err = snaplist_space(&pa->origin_snaps,
                origin_ds->ds_phys->ds_creation_txg, &pa->originusedsnap);
            if (err)
                  return (err);
      }

      return (0);
}

static void
dsl_dataset_promote_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dataset_t *hds = arg1;
      struct promotearg *pa = arg2;
      struct promotenode *snap = list_head(&pa->shared_snaps);
      dsl_dataset_t *origin_ds = snap->ds;
      dsl_dataset_t *origin_head;
      dsl_dir_t *dd = hds->ds_dir;
      dsl_pool_t *dp = hds->ds_dir->dd_pool;
      dsl_dir_t *odd = NULL;
      uint64_t oldnext_obj;
      int64_t delta;

      ASSERT(0 == (hds->ds_phys->ds_flags & DS_FLAG_NOPROMOTE));

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

      /*
       * We need to explicitly open odd, since origin_ds's dd will be
       * changing.
       */
      VERIFY(0 == dsl_dir_open_obj(dp, origin_ds->ds_dir->dd_object,
          NULL, FTAG, &odd));

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

      /* 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));
            VERIFY3U(0, ==, zap_add_int(dp->dp_meta_objset,
                origin_ds->ds_phys->ds_next_clones_obj,
                oldnext_obj, tx));
      }

      /* change origin */
      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;
      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;

      /* move snapshots to this dir */
      for (snap = list_head(&pa->shared_snaps); snap;
          snap = list_next(&pa->shared_snaps, snap)) {
            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;
            }
            /* move snap name entry */
            VERIFY(0 == dsl_dataset_get_snapname(ds));
            VERIFY(0 == dsl_dataset_snap_remove(origin_head,
                ds->ds_snapname, 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);
            ds->ds_phys->ds_dir_obj = dd->dd_object;
            ASSERT3P(ds->ds_dir, ==, odd);
            dsl_dir_close(ds->ds_dir, ds);
            VERIFY(0 == dsl_dir_open_obj(dp, dd->dd_object,
                NULL, ds, &ds->ds_dir));

            ASSERT3U(dsl_prop_numcb(ds), ==, 0);
      }

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

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

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

      dsl_dir_close(odd, FTAG);
}

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

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

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

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

            if (own) {
                  err = dsl_dataset_own_obj(dp, obj,
                      0, snaplist_tag, &ds);
                  if (err == 0)
                        dsl_dataset_make_exclusive(ds, snaplist_tag);
            } else {
                  err = dsl_dataset_hold_obj(dp, obj, snaplist_tag, &ds);
            }
            if (err == ENOENT) {
                  /* lost race with snapshot destroy */
                  struct promotenode *last = list_tail(l);
                  ASSERT(obj != last->ds->ds_phys->ds_prev_snap_obj);
                  obj = last->ds->ds_phys->ds_prev_snap_obj;
                  continue;
            } else if (err) {
                  return (err);
            }

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

            snap = kmem_alloc(sizeof (struct promotenode), KM_SLEEP);
            snap->ds = ds;
            list_insert_tail(l, snap);
            obj = ds->ds_phys->ds_prev_snap_obj;
      }

      return (0);
}

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

      *spacep = 0;
      for (snap = list_head(l); snap; snap = list_next(l, snap)) {
            uint64_t used;
            int err = bplist_space_birthrange(&snap->ds->ds_deadlist,
                mintxg, UINT64_MAX, &used);
            if (err)
                  return (err);
            *spacep += used;
      }
      return (0);
}

static void
snaplist_destroy(list_t *l, boolean_t own)
{
      struct promotenode *snap;

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

      while ((snap = list_tail(l)) != NULL) {
            list_remove(l, snap);
            if (own)
                  dsl_dataset_disown(snap->ds, snaplist_tag);
            else
                  dsl_dataset_rele(snap->ds, snaplist_tag);
            kmem_free(snap, sizeof (struct promotenode));
      }
      list_destroy(l);
}

/*
 * Promote a clone.  Nomenclature note:
 * "clone" or "cds": the original clone which is being promoted
 * "origin" or "ods": the snapshot which is originally clone's origin
 * "origin head" or "ohds": the dataset which is the head
 * (filesystem/volume) for the origin
 * "origin origin": the origin of the origin's filesystem (typically
 * NULL, indicating that the clone is not a clone of a clone).
 */
int
dsl_dataset_promote(const char *name)
{
      dsl_dataset_t *ds;
      dsl_dir_t *dd;
      dsl_pool_t *dp;
      dmu_object_info_t doi;
      struct promotearg pa = { 0 };
      struct promotenode *snap;
      int err;

      err = dsl_dataset_hold(name, FTAG, &ds);
      if (err)
            return (err);
      dd = ds->ds_dir;
      dp = dd->dd_pool;

      err = dmu_object_info(dp->dp_meta_objset,
          ds->ds_phys->ds_snapnames_zapobj, &doi);
      if (err) {
            dsl_dataset_rele(ds, FTAG);
            return (err);
      }

      if (dsl_dataset_is_snapshot(ds) || dd->dd_phys->dd_origin_obj == 0) {
            dsl_dataset_rele(ds, FTAG);
            return (EINVAL);
      }

      /*
       * We are going to inherit all the snapshots taken before our
       * origin (i.e., our new origin will be our parent's origin).
       * Take ownership of them so that we can rename them into our
       * namespace.
       */
      rw_enter(&dp->dp_config_rwlock, RW_READER);

      err = snaplist_make(dp, B_TRUE, 0, dd->dd_phys->dd_origin_obj,
          &pa.shared_snaps);
      if (err != 0)
            goto out;

      err = snaplist_make(dp, B_FALSE, 0, ds->ds_object, &pa.clone_snaps);
      if (err != 0)
            goto out;

      snap = list_head(&pa.shared_snaps);
      ASSERT3U(snap->ds->ds_object, ==, dd->dd_phys->dd_origin_obj);
      err = snaplist_make(dp, B_FALSE, dd->dd_phys->dd_origin_obj,
          snap->ds->ds_dir->dd_phys->dd_head_dataset_obj, &pa.origin_snaps);
      if (err != 0)
            goto out;

      if (dsl_dir_is_clone(snap->ds->ds_dir)) {
            err = dsl_dataset_own_obj(dp,
                snap->ds->ds_dir->dd_phys->dd_origin_obj,
                0, FTAG, &pa.origin_origin);
            if (err != 0)
                  goto out;
      }

out:
      rw_exit(&dp->dp_config_rwlock);

      /*
       * Add in 128x the snapnames zapobj size, since we will be moving
       * a bunch of snapnames to the promoted ds, and dirtying their
       * bonus buffers.
       */
      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);
      }

      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(ds, FTAG);
      return (err);
}

struct cloneswaparg {
      dsl_dataset_t *cds; /* clone dataset */
      dsl_dataset_t *ohds; /* origin's head dataset */
      boolean_t force;
      int64_t unused_refres_delta; /* change in unconsumed refreservation */
};

/* ARGSUSED */
static int
dsl_dataset_clone_swap_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      struct cloneswaparg *csa = arg1;

      /* they should both be heads */
      if (dsl_dataset_is_snapshot(csa->cds) ||
          dsl_dataset_is_snapshot(csa->ohds))
            return (EINVAL);

      /* the branch point should be just before them */
      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)
            return (EINVAL);

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

      /* ohds shouldn't be modified unless 'force' */
      if (!csa->force && dsl_dataset_modified_since_lastsnap(csa->ohds))
            return (ETXTBSY);

      /* adjust amount of any unconsumed refreservation */
      csa->unused_refres_delta =
          (int64_t)MIN(csa->ohds->ds_reserved,
          csa->ohds->ds_phys->ds_unique_bytes) -
          (int64_t)MIN(csa->ohds->ds_reserved,
          csa->cds->ds_phys->ds_unique_bytes);

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

      return (0);
}

/* ARGSUSED */
static void
dsl_dataset_clone_swap_sync(void *arg1, void *arg2, cred_t *cr, 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);

      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->ohds->ds_user_ptr != NULL) {
            csa->ohds->ds_user_evict_func(csa->ohds,
                csa->ohds->ds_user_ptr);
            csa->ohds->ds_user_ptr = 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));

      /* swap blkptrs */
      {
            blkptr_t tmp;
            tmp = csa->ohds->ds_phys->ds_bp;
            csa->ohds->ds_phys->ds_bp = csa->cds->ds_phys->ds_bp;
            csa->cds->ds_phys->ds_bp = tmp;
      }

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

            ASSERT3U(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));

            dused = csa->cds->ds_phys->ds_used_bytes + cdl_used -
                (csa->ohds->ds_phys->ds_used_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 +
                cdl_uncomp -
                (csa->ohds->ds_phys->ds_uncompressed_bytes + odl_uncomp);

            dsl_dir_diduse_space(csa->ohds->ds_dir, DD_USED_HEAD,
                dused, dcomp, duncomp, tx);
            dsl_dir_diduse_space(csa->cds->ds_dir, DD_USED_HEAD,
                -dused, -dcomp, -duncomp, tx);

            /*
             * The difference in the space used by snapshots is the
             * difference in snapshot space due to the head's
             * deadlist (since that's the only thing that's
             * changing that affects the snapused).
             */
            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_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_compressed_bytes,
          csa->cds->ds_phys->ds_compressed_bytes);
      SWITCH64(csa->ohds->ds_phys->ds_uncompressed_bytes,
          csa->cds->ds_phys->ds_uncompressed_bytes);
      SWITCH64(csa->ohds->ds_phys->ds_unique_bytes,
          csa->cds->ds_phys->ds_unique_bytes);

      /* apply any parent delta for change in unconsumed refreservation */
      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);
      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_pool_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.
 */
int
dsl_dataset_clone_swap(dsl_dataset_t *clone, dsl_dataset_t *origin_head,
    boolean_t force)
{
      struct cloneswaparg csa;
      int error;

      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)) {
            rw_exit(&clone->ds_rwlock);
            rw_enter(&origin_head->ds_rwlock, RW_WRITER);
            if (!rw_tryenter(&clone->ds_rwlock, RW_WRITER)) {
                  rw_exit(&origin_head->ds_rwlock);
                  goto retry;
            }
      }
      csa.cds = clone;
      csa.ohds = origin_head;
      csa.force = force;
      error = dsl_sync_task_do(clone->ds_dir->dd_pool,
          dsl_dataset_clone_swap_check,
          dsl_dataset_clone_swap_sync, &csa, NULL, 9);
      return (error);
}

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

      if ((error = spa_open(pname, &spa, FTAG)) != 0)
            return (error);
      dp = spa_get_dsl(spa);
      rw_enter(&dp->dp_config_rwlock, RW_READER);
      if ((error = dsl_dataset_hold_obj(dp, obj, FTAG, &ds)) == 0) {
            dsl_dataset_name(ds, buf);
            dsl_dataset_rele(ds, FTAG);
      }
      rw_exit(&dp->dp_config_rwlock);
      spa_close(spa, FTAG);

      return (error);
}

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

      ASSERT3S(asize, >, 0);

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

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

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

      return (error);
}

/* ARGSUSED */
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;

      if (spa_version(ds->ds_dir->dd_pool->dp_spa) < SPA_VERSION_REFQUOTA)
            return (ENOTSUP);

      if (new_quota == 0)
            return (0);

      if (new_quota < ds->ds_phys->ds_used_bytes ||
          new_quota < ds->ds_reserved)
            return (ENOSPC);

      return (0);
}

/* ARGSUSED */
void
dsl_dataset_set_quota_sync(void *arg1, void *arg2, cred_t *cr, 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_set_uint64_sync(ds->ds_dir, "refquota", new_quota, cr, tx);

      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);
}

int
dsl_dataset_set_quota(const char *dsname, uint64_t quota)
{
      dsl_dataset_t *ds;
      int err;

      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);

            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);
}

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;
      uint64_t unique;

      if (spa_version(ds->ds_dir->dd_pool->dp_spa) <
          SPA_VERSION_REFRESERVATION)
            return (ENOTSUP);

      if (dsl_dataset_is_snapshot(ds))
            return (EINVAL);

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

      mutex_enter(&ds->ds_lock);
      unique = dsl_dataset_unique(ds);
      mutex_exit(&ds->ds_lock);

      if (MAX(unique, new_reservation) > MAX(unique, ds->ds_reserved)) {
            uint64_t delta = MAX(unique, new_reservation) -
                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)
                  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_t *ds = arg1;
      uint64_t *reservationp = arg2;
      uint64_t new_reservation = *reservationp;
      uint64_t unique;
      int64_t delta;

      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)) -
          MAX(0, (int64_t)(ds->ds_reserved - unique));
      ds->ds_reserved = new_reservation;
      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_t *ds;
      int err;

      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_rele(ds, FTAG);
      return (err);
}

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