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dsl_dir.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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <sys/dmu.h>
#include <sys/dmu_objset.h>
#include <sys/dmu_tx.h>
#include <sys/dsl_dataset.h>
#include <sys/dsl_dir.h>
#include <sys/dsl_prop.h>
#include <sys/dsl_synctask.h>
#include <sys/dsl_deleg.h>
#include <sys/spa.h>
#include <sys/zap.h>
#include <sys/zio.h>
#include <sys/arc.h>
#include <sys/sunddi.h>
#include "zfs_namecheck.h"

static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd);
static void dsl_dir_set_reservation_sync(void *arg1, void *arg2,
    cred_t *cr, dmu_tx_t *tx);


/* ARGSUSED */
static void
dsl_dir_evict(dmu_buf_t *db, void *arg)
{
      dsl_dir_t *dd = arg;
      dsl_pool_t *dp = dd->dd_pool;
      int t;

      for (t = 0; t < TXG_SIZE; t++) {
            ASSERT(!txg_list_member(&dp->dp_dirty_dirs, dd, t));
            ASSERT(dd->dd_tempreserved[t] == 0);
            ASSERT(dd->dd_space_towrite[t] == 0);
      }

      if (dd->dd_parent)
            dsl_dir_close(dd->dd_parent, dd);

      spa_close(dd->dd_pool->dp_spa, dd);

      /*
       * The props callback list should be empty since they hold the
       * dir open.
       */
      list_destroy(&dd->dd_prop_cbs);
      mutex_destroy(&dd->dd_lock);
      kmem_free(dd, sizeof (dsl_dir_t));
}

int
dsl_dir_open_obj(dsl_pool_t *dp, uint64_t ddobj,
    const char *tail, void *tag, dsl_dir_t **ddp)
{
      dmu_buf_t *dbuf;
      dsl_dir_t *dd;
      int err;

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

      err = dmu_bonus_hold(dp->dp_meta_objset, ddobj, tag, &dbuf);
      if (err)
            return (err);
      dd = dmu_buf_get_user(dbuf);
#ifdef ZFS_DEBUG
      {
            dmu_object_info_t doi;
            dmu_object_info_from_db(dbuf, &doi);
            ASSERT3U(doi.doi_type, ==, DMU_OT_DSL_DIR);
            ASSERT3U(doi.doi_bonus_size, >=, sizeof (dsl_dir_phys_t));
      }
#endif
      if (dd == NULL) {
            dsl_dir_t *winner;
            int err;

            dd = kmem_zalloc(sizeof (dsl_dir_t), KM_SLEEP);
            dd->dd_object = ddobj;
            dd->dd_dbuf = dbuf;
            dd->dd_pool = dp;
            dd->dd_phys = dbuf->db_data;
            mutex_init(&dd->dd_lock, NULL, MUTEX_DEFAULT, NULL);

            list_create(&dd->dd_prop_cbs, sizeof (dsl_prop_cb_record_t),
                offsetof(dsl_prop_cb_record_t, cbr_node));

            if (dd->dd_phys->dd_parent_obj) {
                  err = dsl_dir_open_obj(dp, dd->dd_phys->dd_parent_obj,
                      NULL, dd, &dd->dd_parent);
                  if (err)
                        goto errout;
                  if (tail) {
#ifdef ZFS_DEBUG
                        uint64_t foundobj;

                        err = zap_lookup(dp->dp_meta_objset,
                            dd->dd_parent->dd_phys->dd_child_dir_zapobj,
                            tail, sizeof (foundobj), 1, &foundobj);
                        ASSERT(err || foundobj == ddobj);
#endif
                        (void) strcpy(dd->dd_myname, tail);
                  } else {
                        err = zap_value_search(dp->dp_meta_objset,
                            dd->dd_parent->dd_phys->dd_child_dir_zapobj,
                            ddobj, 0, dd->dd_myname);
                  }
                  if (err)
                        goto errout;
            } else {
                  (void) strcpy(dd->dd_myname, spa_name(dp->dp_spa));
            }

            winner = dmu_buf_set_user_ie(dbuf, dd, &dd->dd_phys,
                dsl_dir_evict);
            if (winner) {
                  if (dd->dd_parent)
                        dsl_dir_close(dd->dd_parent, dd);
                  mutex_destroy(&dd->dd_lock);
                  kmem_free(dd, sizeof (dsl_dir_t));
                  dd = winner;
            } else {
                  spa_open_ref(dp->dp_spa, dd);
            }
      }

      /*
       * The dsl_dir_t has both open-to-close and instantiate-to-evict
       * holds on the spa.  We need the open-to-close holds because
       * otherwise the spa_refcnt wouldn't change when we open a
       * dir which the spa also has open, so we could incorrectly
       * think it was OK to unload/export/destroy the pool.  We need
       * the instantiate-to-evict hold because the dsl_dir_t has a
       * pointer to the dd_pool, which has a pointer to the spa_t.
       */
      spa_open_ref(dp->dp_spa, tag);
      ASSERT3P(dd->dd_pool, ==, dp);
      ASSERT3U(dd->dd_object, ==, ddobj);
      ASSERT3P(dd->dd_dbuf, ==, dbuf);
      *ddp = dd;
      return (0);

errout:
      if (dd->dd_parent)
            dsl_dir_close(dd->dd_parent, dd);
      mutex_destroy(&dd->dd_lock);
      kmem_free(dd, sizeof (dsl_dir_t));
      dmu_buf_rele(dbuf, tag);
      return (err);

}

void
dsl_dir_close(dsl_dir_t *dd, void *tag)
{
      dprintf_dd(dd, "%s\n", "");
      spa_close(dd->dd_pool->dp_spa, tag);
      dmu_buf_rele(dd->dd_dbuf, tag);
}

/* buf must be long enough (MAXNAMELEN + strlen(MOS_DIR_NAME) + 1 should do) */
void
dsl_dir_name(dsl_dir_t *dd, char *buf)
{
      if (dd->dd_parent) {
            dsl_dir_name(dd->dd_parent, buf);
            (void) strcat(buf, "/");
      } else {
            buf[0] = '\0';
      }
      if (!MUTEX_HELD(&dd->dd_lock)) {
            /*
             * recursive mutex so that we can use
             * dprintf_dd() with dd_lock held
             */
            mutex_enter(&dd->dd_lock);
            (void) strcat(buf, dd->dd_myname);
            mutex_exit(&dd->dd_lock);
      } else {
            (void) strcat(buf, dd->dd_myname);
      }
}

/* Calculate name legnth, avoiding all the strcat calls of dsl_dir_name */
int
dsl_dir_namelen(dsl_dir_t *dd)
{
      int result = 0;

      if (dd->dd_parent) {
            /* parent's name + 1 for the "/" */
            result = dsl_dir_namelen(dd->dd_parent) + 1;
      }

      if (!MUTEX_HELD(&dd->dd_lock)) {
            /* see dsl_dir_name */
            mutex_enter(&dd->dd_lock);
            result += strlen(dd->dd_myname);
            mutex_exit(&dd->dd_lock);
      } else {
            result += strlen(dd->dd_myname);
      }

      return (result);
}

int
dsl_dir_is_private(dsl_dir_t *dd)
{
      int rv = FALSE;

      if (dd->dd_parent && dsl_dir_is_private(dd->dd_parent))
            rv = TRUE;
      if (dataset_name_hidden(dd->dd_myname))
            rv = TRUE;
      return (rv);
}


static int
getcomponent(const char *path, char *component, const char **nextp)
{
      char *p;
      if (path == NULL)
            return (ENOENT);
      /* This would be a good place to reserve some namespace... */
      p = strpbrk(path, "/@");
      if (p && (p[1] == '/' || p[1] == '@')) {
            /* two separators in a row */
            return (EINVAL);
      }
      if (p == NULL || p == path) {
            /*
             * if the first thing is an @ or /, it had better be an
             * @ and it had better not have any more ats or slashes,
             * and it had better have something after the @.
             */
            if (p != NULL &&
                (p[0] != '@' || strpbrk(path+1, "/@") || p[1] == '\0'))
                  return (EINVAL);
            if (strlen(path) >= MAXNAMELEN)
                  return (ENAMETOOLONG);
            (void) strcpy(component, path);
            p = NULL;
      } else if (p[0] == '/') {
            if (p-path >= MAXNAMELEN)
                  return (ENAMETOOLONG);
            (void) strncpy(component, path, p - path);
            component[p-path] = '\0';
            p++;
      } else if (p[0] == '@') {
            /*
             * if the next separator is an @, there better not be
             * any more slashes.
             */
            if (strchr(path, '/'))
                  return (EINVAL);
            if (p-path >= MAXNAMELEN)
                  return (ENAMETOOLONG);
            (void) strncpy(component, path, p - path);
            component[p-path] = '\0';
      } else {
            ASSERT(!"invalid p");
      }
      *nextp = p;
      return (0);
}

/*
 * same as dsl_open_dir, ignore the first component of name and use the
 * spa instead
 */
int
dsl_dir_open_spa(spa_t *spa, const char *name, void *tag,
    dsl_dir_t **ddp, const char **tailp)
{
      char buf[MAXNAMELEN];
      const char *next, *nextnext = NULL;
      int err;
      dsl_dir_t *dd;
      dsl_pool_t *dp;
      uint64_t ddobj;
      int openedspa = FALSE;

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

      err = getcomponent(name, buf, &next);
      if (err)
            return (err);
      if (spa == NULL) {
            err = spa_open(buf, &spa, FTAG);
            if (err) {
                  dprintf("spa_open(%s) failed\n", buf);
                  return (err);
            }
            openedspa = TRUE;

            /* XXX this assertion belongs in spa_open */
            ASSERT(!dsl_pool_sync_context(spa_get_dsl(spa)));
      }

      dp = spa_get_dsl(spa);

      rw_enter(&dp->dp_config_rwlock, RW_READER);
      err = dsl_dir_open_obj(dp, dp->dp_root_dir_obj, NULL, tag, &dd);
      if (err) {
            rw_exit(&dp->dp_config_rwlock);
            if (openedspa)
                  spa_close(spa, FTAG);
            return (err);
      }

      while (next != NULL) {
            dsl_dir_t *child_ds;
            err = getcomponent(next, buf, &nextnext);
            if (err)
                  break;
            ASSERT(next[0] != '\0');
            if (next[0] == '@')
                  break;
            dprintf("looking up %s in obj%lld\n",
                buf, dd->dd_phys->dd_child_dir_zapobj);

            err = zap_lookup(dp->dp_meta_objset,
                dd->dd_phys->dd_child_dir_zapobj,
                buf, sizeof (ddobj), 1, &ddobj);
            if (err) {
                  if (err == ENOENT)
                        err = 0;
                  break;
            }

            err = dsl_dir_open_obj(dp, ddobj, buf, tag, &child_ds);
            if (err)
                  break;
            dsl_dir_close(dd, tag);
            dd = child_ds;
            next = nextnext;
      }
      rw_exit(&dp->dp_config_rwlock);

      if (err) {
            dsl_dir_close(dd, tag);
            if (openedspa)
                  spa_close(spa, FTAG);
            return (err);
      }

      /*
       * It's an error if there's more than one component left, or
       * tailp==NULL and there's any component left.
       */
      if (next != NULL &&
          (tailp == NULL || (nextnext && nextnext[0] != '\0'))) {
            /* bad path name */
            dsl_dir_close(dd, tag);
            dprintf("next=%p (%s) tail=%p\n", next, next?next:"", tailp);
            err = ENOENT;
      }
      if (tailp)
            *tailp = next;
      if (openedspa)
            spa_close(spa, FTAG);
      *ddp = dd;
      return (err);
}

/*
 * Return the dsl_dir_t, and possibly the last component which couldn't
 * be found in *tail.  Return NULL if the path is bogus, or if
 * tail==NULL and we couldn't parse the whole name.  (*tail)[0] == '@'
 * means that the last component is a snapshot.
 */
int
dsl_dir_open(const char *name, void *tag, dsl_dir_t **ddp, const char **tailp)
{
      return (dsl_dir_open_spa(NULL, name, tag, ddp, tailp));
}

uint64_t
dsl_dir_create_sync(dsl_pool_t *dp, dsl_dir_t *pds, const char *name,
    dmu_tx_t *tx)
{
      objset_t *mos = dp->dp_meta_objset;
      uint64_t ddobj;
      dsl_dir_phys_t *dsphys;
      dmu_buf_t *dbuf;

      ddobj = dmu_object_alloc(mos, DMU_OT_DSL_DIR, 0,
          DMU_OT_DSL_DIR, sizeof (dsl_dir_phys_t), tx);
      if (pds) {
            VERIFY(0 == zap_add(mos, pds->dd_phys->dd_child_dir_zapobj,
                name, sizeof (uint64_t), 1, &ddobj, tx));
      } else {
            /* it's the root dir */
            VERIFY(0 == zap_add(mos, DMU_POOL_DIRECTORY_OBJECT,
                DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1, &ddobj, tx));
      }
      VERIFY(0 == dmu_bonus_hold(mos, ddobj, FTAG, &dbuf));
      dmu_buf_will_dirty(dbuf, tx);
      dsphys = dbuf->db_data;

      dsphys->dd_creation_time = gethrestime_sec();
      if (pds)
            dsphys->dd_parent_obj = pds->dd_object;
      dsphys->dd_props_zapobj = zap_create(mos,
          DMU_OT_DSL_PROPS, DMU_OT_NONE, 0, tx);
      dsphys->dd_child_dir_zapobj = zap_create(mos,
          DMU_OT_DSL_DIR_CHILD_MAP, DMU_OT_NONE, 0, tx);
      if (spa_version(dp->dp_spa) >= SPA_VERSION_USED_BREAKDOWN)
            dsphys->dd_flags |= DD_FLAG_USED_BREAKDOWN;
      dmu_buf_rele(dbuf, FTAG);

      return (ddobj);
}

/* ARGSUSED */
int
dsl_dir_destroy_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      dsl_pool_t *dp = dd->dd_pool;
      objset_t *mos = dp->dp_meta_objset;
      int err;
      uint64_t count;

      /*
       * There should be exactly two holds, both from
       * dsl_dataset_destroy: one on the dd directory, and one on its
       * head ds.  Otherwise, someone is trying to lookup something
       * inside this dir while we want to destroy it.  The
       * config_rwlock ensures that nobody else opens it after we
       * check.
       */
      if (dmu_buf_refcount(dd->dd_dbuf) > 2)
            return (EBUSY);

      err = zap_count(mos, dd->dd_phys->dd_child_dir_zapobj, &count);
      if (err)
            return (err);
      if (count != 0)
            return (EEXIST);

      return (0);
}

void
dsl_dir_destroy_sync(void *arg1, void *tag, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      objset_t *mos = dd->dd_pool->dp_meta_objset;
      uint64_t val, obj;
      dd_used_t t;

      ASSERT(RW_WRITE_HELD(&dd->dd_pool->dp_config_rwlock));
      ASSERT(dd->dd_phys->dd_head_dataset_obj == 0);

      /* Remove our reservation. */
      val = 0;
      dsl_dir_set_reservation_sync(dd, &val, cr, tx);
      ASSERT3U(dd->dd_phys->dd_used_bytes, ==, 0);
      ASSERT3U(dd->dd_phys->dd_reserved, ==, 0);
      for (t = 0; t < DD_USED_NUM; t++)
            ASSERT3U(dd->dd_phys->dd_used_breakdown[t], ==, 0);

      VERIFY(0 == zap_destroy(mos, dd->dd_phys->dd_child_dir_zapobj, tx));
      VERIFY(0 == zap_destroy(mos, dd->dd_phys->dd_props_zapobj, tx));
      VERIFY(0 == dsl_deleg_destroy(mos, dd->dd_phys->dd_deleg_zapobj, tx));
      VERIFY(0 == zap_remove(mos,
          dd->dd_parent->dd_phys->dd_child_dir_zapobj, dd->dd_myname, tx));

      obj = dd->dd_object;
      dsl_dir_close(dd, tag);
      VERIFY(0 == dmu_object_free(mos, obj, tx));
}

boolean_t
dsl_dir_is_clone(dsl_dir_t *dd)
{
      return (dd->dd_phys->dd_origin_obj &&
          (dd->dd_pool->dp_origin_snap == NULL ||
          dd->dd_phys->dd_origin_obj !=
          dd->dd_pool->dp_origin_snap->ds_object));
}

void
dsl_dir_stats(dsl_dir_t *dd, nvlist_t *nv)
{
      mutex_enter(&dd->dd_lock);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USED,
          dd->dd_phys->dd_used_bytes);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_QUOTA, dd->dd_phys->dd_quota);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_RESERVATION,
          dd->dd_phys->dd_reserved);
      dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_COMPRESSRATIO,
          dd->dd_phys->dd_compressed_bytes == 0 ? 100 :
          (dd->dd_phys->dd_uncompressed_bytes * 100 /
          dd->dd_phys->dd_compressed_bytes));
      if (dd->dd_phys->dd_flags & DD_FLAG_USED_BREAKDOWN) {
            dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDSNAP,
                dd->dd_phys->dd_used_breakdown[DD_USED_SNAP]);
            dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDDS,
                dd->dd_phys->dd_used_breakdown[DD_USED_HEAD]);
            dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDREFRESERV,
                dd->dd_phys->dd_used_breakdown[DD_USED_REFRSRV]);
            dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDCHILD,
                dd->dd_phys->dd_used_breakdown[DD_USED_CHILD] +
                dd->dd_phys->dd_used_breakdown[DD_USED_CHILD_RSRV]);
      }
      mutex_exit(&dd->dd_lock);

      rw_enter(&dd->dd_pool->dp_config_rwlock, RW_READER);
      if (dsl_dir_is_clone(dd)) {
            dsl_dataset_t *ds;
            char buf[MAXNAMELEN];

            VERIFY(0 == dsl_dataset_hold_obj(dd->dd_pool,
                dd->dd_phys->dd_origin_obj, FTAG, &ds));
            dsl_dataset_name(ds, buf);
            dsl_dataset_rele(ds, FTAG);
            dsl_prop_nvlist_add_string(nv, ZFS_PROP_ORIGIN, buf);
      }
      rw_exit(&dd->dd_pool->dp_config_rwlock);
}

void
dsl_dir_dirty(dsl_dir_t *dd, dmu_tx_t *tx)
{
      dsl_pool_t *dp = dd->dd_pool;

      ASSERT(dd->dd_phys);

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

static int64_t
parent_delta(dsl_dir_t *dd, uint64_t used, int64_t delta)
{
      uint64_t old_accounted = MAX(used, dd->dd_phys->dd_reserved);
      uint64_t new_accounted = MAX(used + delta, dd->dd_phys->dd_reserved);
      return (new_accounted - old_accounted);
}

void
dsl_dir_sync(dsl_dir_t *dd, dmu_tx_t *tx)
{
      ASSERT(dmu_tx_is_syncing(tx));

      dmu_buf_will_dirty(dd->dd_dbuf, tx);

      mutex_enter(&dd->dd_lock);
      ASSERT3U(dd->dd_tempreserved[tx->tx_txg&TXG_MASK], ==, 0);
      dprintf_dd(dd, "txg=%llu towrite=%lluK\n", tx->tx_txg,
          dd->dd_space_towrite[tx->tx_txg&TXG_MASK] / 1024);
      dd->dd_space_towrite[tx->tx_txg&TXG_MASK] = 0;
      mutex_exit(&dd->dd_lock);

      /* release the hold from dsl_dir_dirty */
      dmu_buf_rele(dd->dd_dbuf, dd);
}

static uint64_t
dsl_dir_space_towrite(dsl_dir_t *dd)
{
      uint64_t space = 0;
      int i;

      ASSERT(MUTEX_HELD(&dd->dd_lock));

      for (i = 0; i < TXG_SIZE; i++) {
            space += dd->dd_space_towrite[i&TXG_MASK];
            ASSERT3U(dd->dd_space_towrite[i&TXG_MASK], >=, 0);
      }
      return (space);
}

/*
 * How much space would dd have available if ancestor had delta applied
 * to it?  If ondiskonly is set, we're only interested in what's
 * on-disk, not estimated pending changes.
 */
uint64_t
dsl_dir_space_available(dsl_dir_t *dd,
    dsl_dir_t *ancestor, int64_t delta, int ondiskonly)
{
      uint64_t parentspace, myspace, quota, used;

      /*
       * If there are no restrictions otherwise, assume we have
       * unlimited space available.
       */
      quota = UINT64_MAX;
      parentspace = UINT64_MAX;

      if (dd->dd_parent != NULL) {
            parentspace = dsl_dir_space_available(dd->dd_parent,
                ancestor, delta, ondiskonly);
      }

      mutex_enter(&dd->dd_lock);
      if (dd->dd_phys->dd_quota != 0)
            quota = dd->dd_phys->dd_quota;
      used = dd->dd_phys->dd_used_bytes;
      if (!ondiskonly)
            used += dsl_dir_space_towrite(dd);

      if (dd->dd_parent == NULL) {
            uint64_t poolsize = dsl_pool_adjustedsize(dd->dd_pool, FALSE);
            quota = MIN(quota, poolsize);
      }

      if (dd->dd_phys->dd_reserved > used && parentspace != UINT64_MAX) {
            /*
             * We have some space reserved, in addition to what our
             * parent gave us.
             */
            parentspace += dd->dd_phys->dd_reserved - used;
      }

      if (dd == ancestor) {
            ASSERT(delta <= 0);
            ASSERT(used >= -delta);
            used += delta;
            if (parentspace != UINT64_MAX)
                  parentspace -= delta;
      }

      if (used > quota) {
            /* over quota */
            myspace = 0;

            /*
             * While it's OK to be a little over quota, if
             * we think we are using more space than there
             * is in the pool (which is already 1.6% more than
             * dsl_pool_adjustedsize()), something is very
             * wrong.
             */
            ASSERT3U(used, <=, spa_get_space(dd->dd_pool->dp_spa));
      } else {
            /*
             * the lesser of the space provided by our parent and
             * the space left in our quota
             */
            myspace = MIN(parentspace, quota - used);
      }

      mutex_exit(&dd->dd_lock);

      return (myspace);
}

struct tempreserve {
      list_node_t tr_node;
      dsl_pool_t *tr_dp;
      dsl_dir_t *tr_ds;
      uint64_t tr_size;
};

static int
dsl_dir_tempreserve_impl(dsl_dir_t *dd, uint64_t asize, boolean_t netfree,
    boolean_t ignorequota, boolean_t checkrefquota, list_t *tr_list,
    dmu_tx_t *tx, boolean_t first)
{
      uint64_t txg = tx->tx_txg;
      uint64_t est_inflight, used_on_disk, quota, parent_rsrv;
      struct tempreserve *tr;
      int enospc = EDQUOT;
      int txgidx = txg & TXG_MASK;
      int i;
      uint64_t ref_rsrv = 0;

      ASSERT3U(txg, !=, 0);
      ASSERT3S(asize, >, 0);

      mutex_enter(&dd->dd_lock);

      /*
       * Check against the dsl_dir's quota.  We don't add in the delta
       * when checking for over-quota because they get one free hit.
       */
      est_inflight = dsl_dir_space_towrite(dd);
      for (i = 0; i < TXG_SIZE; i++)
            est_inflight += dd->dd_tempreserved[i];
      used_on_disk = dd->dd_phys->dd_used_bytes;

      /*
       * On the first iteration, fetch the dataset's used-on-disk and
       * refreservation values. Also, if checkrefquota is set, test if
       * allocating this space would exceed the dataset's refquota.
       */
      if (first && tx->tx_objset) {
            int error;
            dsl_dataset_t *ds = tx->tx_objset->os->os_dsl_dataset;

            error = dsl_dataset_check_quota(ds, checkrefquota,
                asize, est_inflight, &used_on_disk, &ref_rsrv);
            if (error) {
                  mutex_exit(&dd->dd_lock);
                  return (error);
            }
      }

      /*
       * If this transaction will result in a net free of space,
       * we want to let it through.
       */
      if (ignorequota || netfree || dd->dd_phys->dd_quota == 0)
            quota = UINT64_MAX;
      else
            quota = dd->dd_phys->dd_quota;

      /*
       * Adjust the quota against the actual pool size at the root.
       * To ensure that it's possible to remove files from a full
       * pool without inducing transient overcommits, we throttle
       * netfree transactions against a quota that is slightly larger,
       * but still within the pool's allocation slop.  In cases where
       * we're very close to full, this will allow a steady trickle of
       * removes to get through.
       */
      if (dd->dd_parent == NULL) {
            uint64_t poolsize = dsl_pool_adjustedsize(dd->dd_pool, netfree);
            if (poolsize < quota) {
                  quota = poolsize;
                  enospc = ENOSPC;
            }
      }

      /*
       * 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 (used_on_disk + est_inflight > quota) {
            if (est_inflight > 0 || used_on_disk < quota)
                  enospc = ERESTART;
            dprintf_dd(dd, "failing: used=%lluK inflight = %lluK "
                "quota=%lluK tr=%lluK err=%d\n",
                used_on_disk>>10, est_inflight>>10,
                quota>>10, asize>>10, enospc);
            mutex_exit(&dd->dd_lock);
            return (enospc);
      }

      /* We need to up our estimated delta before dropping dd_lock */
      dd->dd_tempreserved[txgidx] += asize;

      parent_rsrv = parent_delta(dd, used_on_disk + est_inflight,
          asize - ref_rsrv);
      mutex_exit(&dd->dd_lock);

      tr = kmem_zalloc(sizeof (struct tempreserve), KM_SLEEP);
      tr->tr_ds = dd;
      tr->tr_size = asize;
      list_insert_tail(tr_list, tr);

      /* see if it's OK with our parent */
      if (dd->dd_parent && parent_rsrv) {
            boolean_t ismos = (dd->dd_phys->dd_head_dataset_obj == 0);

            return (dsl_dir_tempreserve_impl(dd->dd_parent,
                parent_rsrv, netfree, ismos, TRUE, tr_list, tx, FALSE));
      } else {
            return (0);
      }
}

/*
 * Reserve space in this dsl_dir, to be used in this tx's txg.
 * After the space has been dirtied (and dsl_dir_willuse_space()
 * has been called), the reservation should be canceled, using
 * dsl_dir_tempreserve_clear().
 */
int
dsl_dir_tempreserve_space(dsl_dir_t *dd, uint64_t lsize, uint64_t asize,
    uint64_t fsize, uint64_t usize, void **tr_cookiep, dmu_tx_t *tx)
{
      int err;
      list_t *tr_list;

      if (asize == 0) {
            *tr_cookiep = NULL;
            return (0);
      }

      tr_list = kmem_alloc(sizeof (list_t), KM_SLEEP);
      list_create(tr_list, sizeof (struct tempreserve),
          offsetof(struct tempreserve, tr_node));
      ASSERT3S(asize, >, 0);
      ASSERT3S(fsize, >=, 0);

      err = arc_tempreserve_space(lsize, tx->tx_txg);
      if (err == 0) {
            struct tempreserve *tr;

            tr = kmem_zalloc(sizeof (struct tempreserve), KM_SLEEP);
            tr->tr_size = lsize;
            list_insert_tail(tr_list, tr);

            err = dsl_pool_tempreserve_space(dd->dd_pool, asize, tx);
      } else {
            if (err == EAGAIN) {
                  txg_delay(dd->dd_pool, tx->tx_txg, 1);
                  err = ERESTART;
            }
            dsl_pool_memory_pressure(dd->dd_pool);
      }

      if (err == 0) {
            struct tempreserve *tr;

            tr = kmem_zalloc(sizeof (struct tempreserve), KM_SLEEP);
            tr->tr_dp = dd->dd_pool;
            tr->tr_size = asize;
            list_insert_tail(tr_list, tr);

            err = dsl_dir_tempreserve_impl(dd, asize, fsize >= asize,
                FALSE, asize > usize, tr_list, tx, TRUE);
      }

      if (err)
            dsl_dir_tempreserve_clear(tr_list, tx);
      else
            *tr_cookiep = tr_list;

      return (err);
}

/*
 * Clear a temporary reservation that we previously made with
 * dsl_dir_tempreserve_space().
 */
void
dsl_dir_tempreserve_clear(void *tr_cookie, dmu_tx_t *tx)
{
      int txgidx = tx->tx_txg & TXG_MASK;
      list_t *tr_list = tr_cookie;
      struct tempreserve *tr;

      ASSERT3U(tx->tx_txg, !=, 0);

      if (tr_cookie == NULL)
            return;

      while (tr = list_head(tr_list)) {
            if (tr->tr_dp) {
                  dsl_pool_tempreserve_clear(tr->tr_dp, tr->tr_size, tx);
            } else if (tr->tr_ds) {
                  mutex_enter(&tr->tr_ds->dd_lock);
                  ASSERT3U(tr->tr_ds->dd_tempreserved[txgidx], >=,
                      tr->tr_size);
                  tr->tr_ds->dd_tempreserved[txgidx] -= tr->tr_size;
                  mutex_exit(&tr->tr_ds->dd_lock);
            } else {
                  arc_tempreserve_clear(tr->tr_size);
            }
            list_remove(tr_list, tr);
            kmem_free(tr, sizeof (struct tempreserve));
      }

      kmem_free(tr_list, sizeof (list_t));
}

static void
dsl_dir_willuse_space_impl(dsl_dir_t *dd, int64_t space, dmu_tx_t *tx)
{
      int64_t parent_space;
      uint64_t est_used;

      mutex_enter(&dd->dd_lock);
      if (space > 0)
            dd->dd_space_towrite[tx->tx_txg & TXG_MASK] += space;

      est_used = dsl_dir_space_towrite(dd) + dd->dd_phys->dd_used_bytes;
      parent_space = parent_delta(dd, est_used, space);
      mutex_exit(&dd->dd_lock);

      /* Make sure that we clean up dd_space_to* */
      dsl_dir_dirty(dd, tx);

      /* XXX this is potentially expensive and unnecessary... */
      if (parent_space && dd->dd_parent)
            dsl_dir_willuse_space_impl(dd->dd_parent, parent_space, tx);
}

/*
 * Call in open context when we think we're going to write/free space,
 * eg. when dirtying data.  Be conservative (ie. OK to write less than
 * this or free more than this, but don't write more or free less).
 */
void
dsl_dir_willuse_space(dsl_dir_t *dd, int64_t space, dmu_tx_t *tx)
{
      dsl_pool_willuse_space(dd->dd_pool, space, tx);
      dsl_dir_willuse_space_impl(dd, space, tx);
}

/* call from syncing context when we actually write/free space for this dd */
void
dsl_dir_diduse_space(dsl_dir_t *dd, dd_used_t type,
    int64_t used, int64_t compressed, int64_t uncompressed, dmu_tx_t *tx)
{
      int64_t accounted_delta;
      boolean_t needlock = !MUTEX_HELD(&dd->dd_lock);

      ASSERT(dmu_tx_is_syncing(tx));
      ASSERT(type < DD_USED_NUM);

      dsl_dir_dirty(dd, tx);

      if (needlock)
            mutex_enter(&dd->dd_lock);
      accounted_delta = parent_delta(dd, dd->dd_phys->dd_used_bytes, used);
      ASSERT(used >= 0 || dd->dd_phys->dd_used_bytes >= -used);
      ASSERT(compressed >= 0 ||
          dd->dd_phys->dd_compressed_bytes >= -compressed);
      ASSERT(uncompressed >= 0 ||
          dd->dd_phys->dd_uncompressed_bytes >= -uncompressed);
      dd->dd_phys->dd_used_bytes += used;
      dd->dd_phys->dd_uncompressed_bytes += uncompressed;
      dd->dd_phys->dd_compressed_bytes += compressed;

      if (dd->dd_phys->dd_flags & DD_FLAG_USED_BREAKDOWN) {
            ASSERT(used > 0 ||
                dd->dd_phys->dd_used_breakdown[type] >= -used);
            dd->dd_phys->dd_used_breakdown[type] += used;
#ifdef DEBUG
            dd_used_t t;
            uint64_t u = 0;
            for (t = 0; t < DD_USED_NUM; t++)
                  u += dd->dd_phys->dd_used_breakdown[t];
            ASSERT3U(u, ==, dd->dd_phys->dd_used_bytes);
#endif
      }
      if (needlock)
            mutex_exit(&dd->dd_lock);

      if (dd->dd_parent != NULL) {
            dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD,
                accounted_delta, compressed, uncompressed, tx);
            dsl_dir_transfer_space(dd->dd_parent,
                used - accounted_delta,
                DD_USED_CHILD_RSRV, DD_USED_CHILD, tx);
      }
}

void
dsl_dir_transfer_space(dsl_dir_t *dd, int64_t delta,
    dd_used_t oldtype, dd_used_t newtype, dmu_tx_t *tx)
{
      boolean_t needlock = !MUTEX_HELD(&dd->dd_lock);

      ASSERT(dmu_tx_is_syncing(tx));
      ASSERT(oldtype < DD_USED_NUM);
      ASSERT(newtype < DD_USED_NUM);

      if (delta == 0 || !(dd->dd_phys->dd_flags & DD_FLAG_USED_BREAKDOWN))
            return;

      dsl_dir_dirty(dd, tx);
      if (needlock)
            mutex_enter(&dd->dd_lock);
      ASSERT(delta > 0 ?
          dd->dd_phys->dd_used_breakdown[oldtype] >= delta :
          dd->dd_phys->dd_used_breakdown[newtype] >= -delta);
      ASSERT(dd->dd_phys->dd_used_bytes >= ABS(delta));
      dd->dd_phys->dd_used_breakdown[oldtype] -= delta;
      dd->dd_phys->dd_used_breakdown[newtype] += delta;
      if (needlock)
            mutex_exit(&dd->dd_lock);
}

static int
dsl_dir_set_quota_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      uint64_t *quotap = arg2;
      uint64_t new_quota = *quotap;
      int err = 0;
      uint64_t towrite;

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

      mutex_enter(&dd->dd_lock);
      /*
       * If we are doing the preliminary check in open context, and
       * there are pending changes, then don't fail it, since the
       * pending changes could under-estimate the amount of space to be
       * freed up.
       */
      towrite = dsl_dir_space_towrite(dd);
      if ((dmu_tx_is_syncing(tx) || towrite == 0) &&
          (new_quota < dd->dd_phys->dd_reserved ||
          new_quota < dd->dd_phys->dd_used_bytes + towrite)) {
            err = ENOSPC;
      }
      mutex_exit(&dd->dd_lock);
      return (err);
}

/* ARGSUSED */
static void
dsl_dir_set_quota_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      uint64_t *quotap = arg2;
      uint64_t new_quota = *quotap;

      dmu_buf_will_dirty(dd->dd_dbuf, tx);

      mutex_enter(&dd->dd_lock);
      dd->dd_phys->dd_quota = new_quota;
      mutex_exit(&dd->dd_lock);

      spa_history_internal_log(LOG_DS_QUOTA, dd->dd_pool->dp_spa,
          tx, cr, "%lld dataset = %llu ",
          (longlong_t)new_quota, dd->dd_phys->dd_head_dataset_obj);
}

int
dsl_dir_set_quota(const char *ddname, uint64_t quota)
{
      dsl_dir_t *dd;
      int err;

      err = dsl_dir_open(ddname, FTAG, &dd, NULL);
      if (err)
            return (err);

      if (quota != dd->dd_phys->dd_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(dd->dd_pool, 0);

            err = dsl_sync_task_do(dd->dd_pool, dsl_dir_set_quota_check,
                dsl_dir_set_quota_sync, dd, &quota, 0);
      }
      dsl_dir_close(dd, FTAG);
      return (err);
}

int
dsl_dir_set_reservation_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      uint64_t *reservationp = arg2;
      uint64_t new_reservation = *reservationp;
      uint64_t used, avail;
      int64_t delta;

      if (new_reservation > INT64_MAX)
            return (EOVERFLOW);

      /*
       * 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(&dd->dd_lock);
      used = dd->dd_phys->dd_used_bytes;
      delta = MAX(used, new_reservation) -
          MAX(used, dd->dd_phys->dd_reserved);
      mutex_exit(&dd->dd_lock);

      if (dd->dd_parent) {
            avail = dsl_dir_space_available(dd->dd_parent,
                NULL, 0, FALSE);
      } else {
            avail = dsl_pool_adjustedsize(dd->dd_pool, B_FALSE) - used;
      }

      if (delta > 0 && delta > avail)
            return (ENOSPC);
      if (delta > 0 && dd->dd_phys->dd_quota > 0 &&
          new_reservation > dd->dd_phys->dd_quota)
            return (ENOSPC);
      return (0);
}

/* ARGSUSED */
static void
dsl_dir_set_reservation_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      uint64_t *reservationp = arg2;
      uint64_t new_reservation = *reservationp;
      uint64_t used;
      int64_t delta;

      dmu_buf_will_dirty(dd->dd_dbuf, tx);

      mutex_enter(&dd->dd_lock);
      used = dd->dd_phys->dd_used_bytes;
      delta = MAX(used, new_reservation) -
          MAX(used, dd->dd_phys->dd_reserved);
      dd->dd_phys->dd_reserved = new_reservation;

      if (dd->dd_parent != NULL) {
            /* Roll up this additional usage into our ancestors */
            dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD_RSRV,
                delta, 0, 0, tx);
      }
      mutex_exit(&dd->dd_lock);

      spa_history_internal_log(LOG_DS_RESERVATION, dd->dd_pool->dp_spa,
          tx, cr, "%lld dataset = %llu",
          (longlong_t)new_reservation, dd->dd_phys->dd_head_dataset_obj);
}

int
dsl_dir_set_reservation(const char *ddname, uint64_t reservation)
{
      dsl_dir_t *dd;
      int err;

      err = dsl_dir_open(ddname, FTAG, &dd, NULL);
      if (err)
            return (err);
      err = dsl_sync_task_do(dd->dd_pool, dsl_dir_set_reservation_check,
          dsl_dir_set_reservation_sync, dd, &reservation, 0);
      dsl_dir_close(dd, FTAG);
      return (err);
}

static dsl_dir_t *
closest_common_ancestor(dsl_dir_t *ds1, dsl_dir_t *ds2)
{
      for (; ds1; ds1 = ds1->dd_parent) {
            dsl_dir_t *dd;
            for (dd = ds2; dd; dd = dd->dd_parent) {
                  if (ds1 == dd)
                        return (dd);
            }
      }
      return (NULL);
}

/*
 * If delta is applied to dd, how much of that delta would be applied to
 * ancestor?  Syncing context only.
 */
static int64_t
would_change(dsl_dir_t *dd, int64_t delta, dsl_dir_t *ancestor)
{
      if (dd == ancestor)
            return (delta);

      mutex_enter(&dd->dd_lock);
      delta = parent_delta(dd, dd->dd_phys->dd_used_bytes, delta);
      mutex_exit(&dd->dd_lock);
      return (would_change(dd->dd_parent, delta, ancestor));
}

struct renamearg {
      dsl_dir_t *newparent;
      const char *mynewname;
};

/*ARGSUSED*/
static int
dsl_dir_rename_check(void *arg1, void *arg2, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      struct renamearg *ra = arg2;
      dsl_pool_t *dp = dd->dd_pool;
      objset_t *mos = dp->dp_meta_objset;
      int err;
      uint64_t val;

      /* There should be 2 references: the open and the dirty */
      if (dmu_buf_refcount(dd->dd_dbuf) > 2)
            return (EBUSY);

      /* check for existing name */
      err = zap_lookup(mos, ra->newparent->dd_phys->dd_child_dir_zapobj,
          ra->mynewname, 8, 1, &val);
      if (err == 0)
            return (EEXIST);
      if (err != ENOENT)
            return (err);

      if (ra->newparent != dd->dd_parent) {
            /* is there enough space? */
            uint64_t myspace =
                MAX(dd->dd_phys->dd_used_bytes, dd->dd_phys->dd_reserved);

            /* no rename into our descendant */
            if (closest_common_ancestor(dd, ra->newparent) == dd)
                  return (EINVAL);

            if (err = dsl_dir_transfer_possible(dd->dd_parent,
                ra->newparent, myspace))
                  return (err);
      }

      return (0);
}

static void
dsl_dir_rename_sync(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
{
      dsl_dir_t *dd = arg1;
      struct renamearg *ra = arg2;
      dsl_pool_t *dp = dd->dd_pool;
      objset_t *mos = dp->dp_meta_objset;
      int err;

      ASSERT(dmu_buf_refcount(dd->dd_dbuf) <= 2);

      if (ra->newparent != dd->dd_parent) {
            dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD,
                -dd->dd_phys->dd_used_bytes,
                -dd->dd_phys->dd_compressed_bytes,
                -dd->dd_phys->dd_uncompressed_bytes, tx);
            dsl_dir_diduse_space(ra->newparent, DD_USED_CHILD,
                dd->dd_phys->dd_used_bytes,
                dd->dd_phys->dd_compressed_bytes,
                dd->dd_phys->dd_uncompressed_bytes, tx);

            if (dd->dd_phys->dd_reserved > dd->dd_phys->dd_used_bytes) {
                  uint64_t unused_rsrv = dd->dd_phys->dd_reserved -
                      dd->dd_phys->dd_used_bytes;

                  dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD_RSRV,
                      -unused_rsrv, 0, 0, tx);
                  dsl_dir_diduse_space(ra->newparent, DD_USED_CHILD_RSRV,
                      unused_rsrv, 0, 0, tx);
            }
      }

      dmu_buf_will_dirty(dd->dd_dbuf, tx);

      /* remove from old parent zapobj */
      err = zap_remove(mos, dd->dd_parent->dd_phys->dd_child_dir_zapobj,
          dd->dd_myname, tx);
      ASSERT3U(err, ==, 0);

      (void) strcpy(dd->dd_myname, ra->mynewname);
      dsl_dir_close(dd->dd_parent, dd);
      dd->dd_phys->dd_parent_obj = ra->newparent->dd_object;
      VERIFY(0 == dsl_dir_open_obj(dd->dd_pool,
          ra->newparent->dd_object, NULL, dd, &dd->dd_parent));

      /* add to new parent zapobj */
      err = zap_add(mos, ra->newparent->dd_phys->dd_child_dir_zapobj,
          dd->dd_myname, 8, 1, &dd->dd_object, tx);
      ASSERT3U(err, ==, 0);

      spa_history_internal_log(LOG_DS_RENAME, dd->dd_pool->dp_spa,
          tx, cr, "dataset = %llu", dd->dd_phys->dd_head_dataset_obj);
}

int
dsl_dir_rename(dsl_dir_t *dd, const char *newname)
{
      struct renamearg ra;
      int err;

      /* new parent should exist */
      err = dsl_dir_open(newname, FTAG, &ra.newparent, &ra.mynewname);
      if (err)
            return (err);

      /* can't rename to different pool */
      if (dd->dd_pool != ra.newparent->dd_pool) {
            err = ENXIO;
            goto out;
      }

      /* new name should not already exist */
      if (ra.mynewname == NULL) {
            err = EEXIST;
            goto out;
      }

      err = dsl_sync_task_do(dd->dd_pool,
          dsl_dir_rename_check, dsl_dir_rename_sync, dd, &ra, 3);

out:
      dsl_dir_close(ra.newparent, FTAG);
      return (err);
}

int
dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd, uint64_t space)
{
      dsl_dir_t *ancestor;
      int64_t adelta;
      uint64_t avail;

      ancestor = closest_common_ancestor(sdd, tdd);
      adelta = would_change(sdd, -space, ancestor);
      avail = dsl_dir_space_available(tdd, ancestor, adelta, FALSE);
      if (avail < space)
            return (ENOSPC);

      return (0);
}

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