FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/zfs/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 https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    /*
     * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
     * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
     * Copyright (c) 2013 Martin Matuska. All rights reserved.
     * Copyright (c) 2014 Joyent, Inc. All rights reserved.
     * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
     * Copyright (c) 2016 Actifio, Inc. All rights reserved.
     * Copyright (c) 2018, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
     */
    
    #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/dmu_impl.h>
    #include <sys/spa.h>
    #include <sys/spa_impl.h>
    #include <sys/metaslab.h>
    #include <sys/zap.h>
    #include <sys/zio.h>
    #include <sys/arc.h>
    #include <sys/sunddi.h>
    #include <sys/zfeature.h>
    #include <sys/policy.h>
    #include <sys/zfs_vfsops.h>
    #include <sys/zfs_znode.h>
    #include <sys/zvol.h>
    #include <sys/zthr.h>
    #include "zfs_namecheck.h"
    #include "zfs_prop.h"
    
    /*
     * This controls if we verify the ZVOL quota or not.
     * Currently, quotas are not implemented for ZVOLs.
     * The quota size is the size of the ZVOL.
     * The size of the volume already implies the ZVOL size quota.
     * The quota mechanism can introduce a significant performance drop.
     */
    static int zvol_enforce_quotas = B_TRUE;
    
    /*
     * Filesystem and Snapshot Limits
     * ------------------------------
     *
     * These limits are used to restrict the number of filesystems and/or snapshots
     * that can be created at a given level in the tree or below. A typical
     * use-case is with a delegated dataset where the administrator wants to ensure
     * that a user within the zone is not creating too many additional filesystems
     * or snapshots, even though they're not exceeding their space quota.
     *
     * The filesystem and snapshot counts are stored as extensible properties. This
     * capability is controlled by a feature flag and must be enabled to be used.
     * Once enabled, the feature is not active until the first limit is set. At
     * that point, future operations to create/destroy filesystems or snapshots
     * will validate and update the counts.
     *
     * Because the count properties will not exist before the feature is active,
     * the counts are updated when a limit is first set on an uninitialized
     * dsl_dir node in the tree (The filesystem/snapshot count on a node includes
     * all of the nested filesystems/snapshots. Thus, a new leaf node has a
     * filesystem count of 0 and a snapshot count of 0. Non-existent filesystem and
     * snapshot count properties on a node indicate uninitialized counts on that
     * node.) When first setting a limit on an uninitialized node, the code starts
     * at the filesystem with the new limit and descends into all sub-filesystems
     * to add the count properties.
     *
     * In practice this is lightweight since a limit is typically set when the
     * filesystem is created and thus has no children. Once valid, changing the
     * limit value won't require a re-traversal since the counts are already valid.
     * When recursively fixing the counts, if a node with a limit is encountered
     * during the descent, the counts are known to be valid and there is no need to
     * descend into that filesystem's children. The counts on filesystems above the
     * one with the new limit will still be uninitialized, unless a limit is
     * eventually set on one of those filesystems. The counts are always recursively
     * updated when a limit is set on a dataset, unless there is already a limit.
    * When a new limit value is set on a filesystem with an existing limit, it is
    * possible for the new limit to be less than the current count at that level
    * since a user who can change the limit is also allowed to exceed the limit.
    *
    * Once the feature is active, then whenever a filesystem or snapshot is
    * created, the code recurses up the tree, validating the new count against the
    * limit at each initialized level. In practice, most levels will not have a
    * limit set. If there is a limit at any initialized level up the tree, the
    * check must pass or the creation will fail. Likewise, when a filesystem or
    * snapshot is destroyed, the counts are recursively adjusted all the way up
    * the initialized nodes in the tree. Renaming a filesystem into different point
    * in the tree will first validate, then update the counts on each branch up to
    * the common ancestor. A receive will also validate the counts and then update
    * them.
    *
    * An exception to the above behavior is that the limit is not enforced if the
    * user has permission to modify the limit. This is primarily so that
    * recursive snapshots in the global zone always work. We want to prevent a
    * denial-of-service in which a lower level delegated dataset could max out its
    * limit and thus block recursive snapshots from being taken in the global zone.
    * Because of this, it is possible for the snapshot count to be over the limit
    * and snapshots taken in the global zone could cause a lower level dataset to
    * hit or exceed its limit. The administrator taking the global zone recursive
    * snapshot should be aware of this side-effect and behave accordingly.
    * For consistency, the filesystem limit is also not enforced if the user can
    * modify the limit.
    *
    * The filesystem and snapshot limits are validated by dsl_fs_ss_limit_check()
    * and updated by dsl_fs_ss_count_adjust(). A new limit value is setup in
    * dsl_dir_activate_fs_ss_limit() and the counts are adjusted, if necessary, by
    * dsl_dir_init_fs_ss_count().
    */
   
   static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd);
   
   typedef struct ddulrt_arg {
           dsl_dir_t       *ddulrta_dd;
           uint64_t        ddlrta_txg;
   } ddulrt_arg_t;
   
   static void
   dsl_dir_evict_async(void *dbu)
   {
           dsl_dir_t *dd = dbu;
           int t;
           dsl_pool_t *dp __maybe_unused = dd->dd_pool;
   
           dd->dd_dbuf = NULL;
   
           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_async_rele(dd->dd_parent, dd);
   
           spa_async_close(dd->dd_pool->dp_spa, dd);
   
           if (dsl_deadlist_is_open(&dd->dd_livelist))
                   dsl_dir_livelist_close(dd);
   
           dsl_prop_fini(dd);
           cv_destroy(&dd->dd_activity_cv);
           mutex_destroy(&dd->dd_activity_lock);
           mutex_destroy(&dd->dd_lock);
           kmem_free(dd, sizeof (dsl_dir_t));
   }
   
   int
   dsl_dir_hold_obj(dsl_pool_t *dp, uint64_t ddobj,
       const char *tail, const void *tag, dsl_dir_t **ddp)
   {
           dmu_buf_t *dbuf;
           dsl_dir_t *dd;
           dmu_object_info_t doi;
           int err;
   
           ASSERT(dsl_pool_config_held(dp));
   
           err = dmu_bonus_hold(dp->dp_meta_objset, ddobj, tag, &dbuf);
           if (err != 0)
                   return (err);
           dd = dmu_buf_get_user(dbuf);
   
           dmu_object_info_from_db(dbuf, &doi);
           ASSERT3U(doi.doi_bonus_type, ==, DMU_OT_DSL_DIR);
           ASSERT3U(doi.doi_bonus_size, >=, sizeof (dsl_dir_phys_t));
   
           if (dd == NULL) {
                   dsl_dir_t *winner;
   
                   dd = kmem_zalloc(sizeof (dsl_dir_t), KM_SLEEP);
                   dd->dd_object = ddobj;
                   dd->dd_dbuf = dbuf;
                   dd->dd_pool = dp;
   
                   mutex_init(&dd->dd_lock, NULL, MUTEX_DEFAULT, NULL);
                   mutex_init(&dd->dd_activity_lock, NULL, MUTEX_DEFAULT, NULL);
                   cv_init(&dd->dd_activity_cv, NULL, CV_DEFAULT, NULL);
                   dsl_prop_init(dd);
   
                   if (dsl_dir_is_zapified(dd)) {
                           err = zap_lookup(dp->dp_meta_objset,
                               ddobj, DD_FIELD_CRYPTO_KEY_OBJ,
                               sizeof (uint64_t), 1, &dd->dd_crypto_obj);
                           if (err == 0) {
                                   /* check for on-disk format errata */
                                   if (dsl_dir_incompatible_encryption_version(
                                       dd)) {
                                           dp->dp_spa->spa_errata =
                                               ZPOOL_ERRATA_ZOL_6845_ENCRYPTION;
                                   }
                           } else if (err != ENOENT) {
                                   goto errout;
                           }
                   }
   
                   if (dsl_dir_phys(dd)->dd_parent_obj) {
                           err = dsl_dir_hold_obj(dp,
                               dsl_dir_phys(dd)->dd_parent_obj, NULL, dd,
                               &dd->dd_parent);
                           if (err != 0)
                                   goto errout;
                           if (tail) {
   #ifdef ZFS_DEBUG
                                   uint64_t foundobj;
   
                                   err = zap_lookup(dp->dp_meta_objset,
                                       dsl_dir_phys(dd->dd_parent)->
                                       dd_child_dir_zapobj, tail,
                                       sizeof (foundobj), 1, &foundobj);
                                   ASSERT(err || foundobj == ddobj);
   #endif
                                   (void) strlcpy(dd->dd_myname, tail,
                                       sizeof (dd->dd_myname));
                           } else {
                                   err = zap_value_search(dp->dp_meta_objset,
                                       dsl_dir_phys(dd->dd_parent)->
                                       dd_child_dir_zapobj,
                                       ddobj, 0, dd->dd_myname);
                           }
                           if (err != 0)
                                   goto errout;
                   } else {
                           (void) strlcpy(dd->dd_myname, spa_name(dp->dp_spa),
                               sizeof (dd->dd_myname));
                   }
   
                   if (dsl_dir_is_clone(dd)) {
                           dmu_buf_t *origin_bonus;
                           dsl_dataset_phys_t *origin_phys;
   
                           /*
                            * We can't open the origin dataset, because
                            * that would require opening this dsl_dir.
                            * Just look at its phys directly instead.
                            */
                           err = dmu_bonus_hold(dp->dp_meta_objset,
                               dsl_dir_phys(dd)->dd_origin_obj, FTAG,
                               &origin_bonus);
                           if (err != 0)
                                   goto errout;
                           origin_phys = origin_bonus->db_data;
                           dd->dd_origin_txg =
                               origin_phys->ds_creation_txg;
                           dmu_buf_rele(origin_bonus, FTAG);
                           if (dsl_dir_is_zapified(dd)) {
                                   uint64_t obj;
                                   err = zap_lookup(dp->dp_meta_objset,
                                       dd->dd_object, DD_FIELD_LIVELIST,
                                       sizeof (uint64_t), 1, &obj);
                                   if (err == 0)
                                           dsl_dir_livelist_open(dd, obj);
                                   else if (err != ENOENT)
                                           goto errout;
                           }
                   }
   
                   if (dsl_dir_is_zapified(dd)) {
                           inode_timespec_t t = {0};
                           (void) zap_lookup(dp->dp_meta_objset, ddobj,
                               DD_FIELD_SNAPSHOTS_CHANGED,
                               sizeof (uint64_t),
                               sizeof (inode_timespec_t) / sizeof (uint64_t),
                               &t);
                           dd->dd_snap_cmtime = t;
                   }
   
                   dmu_buf_init_user(&dd->dd_dbu, NULL, dsl_dir_evict_async,
                       &dd->dd_dbuf);
                   winner = dmu_buf_set_user_ie(dbuf, &dd->dd_dbu);
                   if (winner != NULL) {
                           if (dd->dd_parent)
                                   dsl_dir_rele(dd->dd_parent, dd);
                           if (dsl_deadlist_is_open(&dd->dd_livelist))
                                   dsl_dir_livelist_close(dd);
                           dsl_prop_fini(dd);
                           cv_destroy(&dd->dd_activity_cv);
                           mutex_destroy(&dd->dd_activity_lock);
                           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_rele(dd->dd_parent, dd);
           if (dsl_deadlist_is_open(&dd->dd_livelist))
                   dsl_dir_livelist_close(dd);
           dsl_prop_fini(dd);
           cv_destroy(&dd->dd_activity_cv);
           mutex_destroy(&dd->dd_activity_lock);
           mutex_destroy(&dd->dd_lock);
           kmem_free(dd, sizeof (dsl_dir_t));
           dmu_buf_rele(dbuf, tag);
           return (err);
   }
   
   void
   dsl_dir_rele(dsl_dir_t *dd, const void *tag)
   {
           dprintf_dd(dd, "%s\n", "");
           spa_close(dd->dd_pool->dp_spa, tag);
           dmu_buf_rele(dd->dd_dbuf, tag);
   }
   
   /*
    * Remove a reference to the given dsl dir that is being asynchronously
    * released.  Async releases occur from a taskq performing eviction of
    * dsl datasets and dirs.  This process is identical to a normal release
    * with the exception of using the async API for releasing the reference on
    * the spa.
    */
   void
   dsl_dir_async_rele(dsl_dir_t *dd, const void *tag)
   {
           dprintf_dd(dd, "%s\n", "");
           spa_async_close(dd->dd_pool->dp_spa, tag);
           dmu_buf_rele(dd->dd_dbuf, tag);
   }
   
   /* buf must be at least ZFS_MAX_DATASET_NAME_LEN bytes */
   void
   dsl_dir_name(dsl_dir_t *dd, char *buf)
   {
           if (dd->dd_parent) {
                   dsl_dir_name(dd->dd_parent, buf);
                   VERIFY3U(strlcat(buf, "/", ZFS_MAX_DATASET_NAME_LEN), <,
                       ZFS_MAX_DATASET_NAME_LEN);
           } 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);
                   VERIFY3U(strlcat(buf, dd->dd_myname, ZFS_MAX_DATASET_NAME_LEN),
                       <, ZFS_MAX_DATASET_NAME_LEN);
                   mutex_exit(&dd->dd_lock);
           } else {
                   VERIFY3U(strlcat(buf, dd->dd_myname, ZFS_MAX_DATASET_NAME_LEN),
                       <, ZFS_MAX_DATASET_NAME_LEN);
           }
   }
   
   /* Calculate name length, 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);
   }
   
   static int
   getcomponent(const char *path, char *component, const char **nextp)
   {
           char *p;
   
           if ((path == NULL) || (path[0] == '\0'))
                   return (SET_ERROR(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 (SET_ERROR(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 (SET_ERROR(EINVAL));
                   if (strlen(path) >= ZFS_MAX_DATASET_NAME_LEN)
                           return (SET_ERROR(ENAMETOOLONG));
                   (void) strlcpy(component, path, ZFS_MAX_DATASET_NAME_LEN);
                   p = NULL;
           } else if (p[0] == '/') {
                   if (p - path >= ZFS_MAX_DATASET_NAME_LEN)
                           return (SET_ERROR(ENAMETOOLONG));
                   (void) strlcpy(component, path, p - path + 1);
                   p++;
           } else if (p[0] == '@') {
                   /*
                    * if the next separator is an @, there better not be
                    * any more slashes.
                    */
                   if (strchr(path, '/'))
                           return (SET_ERROR(EINVAL));
                   if (p - path >= ZFS_MAX_DATASET_NAME_LEN)
                           return (SET_ERROR(ENAMETOOLONG));
                   (void) strlcpy(component, path, p - path + 1);
           } else {
                   panic("invalid p=%p", (void *)p);
           }
           *nextp = p;
           return (0);
   }
   
   /*
    * Return the dsl_dir_t, and possibly the last component which couldn't
    * be found in *tail.  The name must be in the specified dsl_pool_t.  This
    * thread must hold the dp_config_rwlock for the pool.  Returns 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_hold(dsl_pool_t *dp, const char *name, const void *tag,
       dsl_dir_t **ddp, const char **tailp)
   {
           char *buf;
           const char *spaname, *next, *nextnext = NULL;
           int err;
           dsl_dir_t *dd;
           uint64_t ddobj;
   
           buf = kmem_alloc(ZFS_MAX_DATASET_NAME_LEN, KM_SLEEP);
           err = getcomponent(name, buf, &next);
           if (err != 0)
                   goto error;
   
           /* Make sure the name is in the specified pool. */
           spaname = spa_name(dp->dp_spa);
           if (strcmp(buf, spaname) != 0) {
                   err = SET_ERROR(EXDEV);
                   goto error;
           }
   
           ASSERT(dsl_pool_config_held(dp));
   
           err = dsl_dir_hold_obj(dp, dp->dp_root_dir_obj, NULL, tag, &dd);
           if (err != 0) {
                   goto error;
           }
   
           while (next != NULL) {
                   dsl_dir_t *child_dd;
                   err = getcomponent(next, buf, &nextnext);
                   if (err != 0)
                           break;
                   ASSERT(next[0] != '\0');
                   if (next[0] == '@')
                           break;
                   dprintf("looking up %s in obj%lld\n",
                       buf, (longlong_t)dsl_dir_phys(dd)->dd_child_dir_zapobj);
   
                   err = zap_lookup(dp->dp_meta_objset,
                       dsl_dir_phys(dd)->dd_child_dir_zapobj,
                       buf, sizeof (ddobj), 1, &ddobj);
                   if (err != 0) {
                           if (err == ENOENT)
                                   err = 0;
                           break;
                   }
   
                   err = dsl_dir_hold_obj(dp, ddobj, buf, tag, &child_dd);
                   if (err != 0)
                           break;
                   dsl_dir_rele(dd, tag);
                   dd = child_dd;
                   next = nextnext;
           }
   
           if (err != 0) {
                   dsl_dir_rele(dd, tag);
                   goto error;
           }
   
           /*
            * 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_rele(dd, tag);
                   dprintf("next=%p (%s) tail=%p\n", next, next?next:"", tailp);
                   err = SET_ERROR(ENOENT);
           }
           if (tailp != NULL)
                   *tailp = next;
           if (err == 0)
                   *ddp = dd;
   error:
           kmem_free(buf, ZFS_MAX_DATASET_NAME_LEN);
           return (err);
   }
   
   /*
    * If the counts are already initialized for this filesystem and its
    * descendants then do nothing, otherwise initialize the counts.
    *
    * The counts on this filesystem, and those below, may be uninitialized due to
    * either the use of a pre-existing pool which did not support the
    * filesystem/snapshot limit feature, or one in which the feature had not yet
    * been enabled.
    *
    * Recursively descend the filesystem tree and update the filesystem/snapshot
    * counts on each filesystem below, then update the cumulative count on the
    * current filesystem. If the filesystem already has a count set on it,
    * then we know that its counts, and the counts on the filesystems below it,
    * are already correct, so we don't have to update this filesystem.
    */
   static void
   dsl_dir_init_fs_ss_count(dsl_dir_t *dd, dmu_tx_t *tx)
   {
           uint64_t my_fs_cnt = 0;
           uint64_t my_ss_cnt = 0;
           dsl_pool_t *dp = dd->dd_pool;
           objset_t *os = dp->dp_meta_objset;
           zap_cursor_t *zc;
           zap_attribute_t *za;
           dsl_dataset_t *ds;
   
           ASSERT(spa_feature_is_active(dp->dp_spa, SPA_FEATURE_FS_SS_LIMIT));
           ASSERT(dsl_pool_config_held(dp));
           ASSERT(dmu_tx_is_syncing(tx));
   
           dsl_dir_zapify(dd, tx);
   
           /*
            * If the filesystem count has already been initialized then we
            * don't need to recurse down any further.
            */
           if (zap_contains(os, dd->dd_object, DD_FIELD_FILESYSTEM_COUNT) == 0)
                   return;
   
           zc = kmem_alloc(sizeof (zap_cursor_t), KM_SLEEP);
           za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP);
   
           /* Iterate my child dirs */
           for (zap_cursor_init(zc, os, dsl_dir_phys(dd)->dd_child_dir_zapobj);
               zap_cursor_retrieve(zc, za) == 0; zap_cursor_advance(zc)) {
                   dsl_dir_t *chld_dd;
                   uint64_t count;
   
                   VERIFY0(dsl_dir_hold_obj(dp, za->za_first_integer, NULL, FTAG,
                       &chld_dd));
   
                   /*
                    * Ignore hidden ($FREE, $MOS & $ORIGIN) objsets.
                    */
                   if (chld_dd->dd_myname[0] == '$') {
                           dsl_dir_rele(chld_dd, FTAG);
                           continue;
                   }
   
                   my_fs_cnt++;    /* count this child */
   
                   dsl_dir_init_fs_ss_count(chld_dd, tx);
   
                   VERIFY0(zap_lookup(os, chld_dd->dd_object,
                       DD_FIELD_FILESYSTEM_COUNT, sizeof (count), 1, &count));
                   my_fs_cnt += count;
                   VERIFY0(zap_lookup(os, chld_dd->dd_object,
                       DD_FIELD_SNAPSHOT_COUNT, sizeof (count), 1, &count));
                   my_ss_cnt += count;
   
                   dsl_dir_rele(chld_dd, FTAG);
           }
           zap_cursor_fini(zc);
           /* Count my snapshots (we counted children's snapshots above) */
           VERIFY0(dsl_dataset_hold_obj(dd->dd_pool,
               dsl_dir_phys(dd)->dd_head_dataset_obj, FTAG, &ds));
   
           for (zap_cursor_init(zc, os, dsl_dataset_phys(ds)->ds_snapnames_zapobj);
               zap_cursor_retrieve(zc, za) == 0;
               zap_cursor_advance(zc)) {
                   /* Don't count temporary snapshots */
                   if (za->za_name[0] != '%')
                           my_ss_cnt++;
           }
           zap_cursor_fini(zc);
   
           dsl_dataset_rele(ds, FTAG);
   
           kmem_free(zc, sizeof (zap_cursor_t));
           kmem_free(za, sizeof (zap_attribute_t));
   
           /* we're in a sync task, update counts */
           dmu_buf_will_dirty(dd->dd_dbuf, tx);
           VERIFY0(zap_add(os, dd->dd_object, DD_FIELD_FILESYSTEM_COUNT,
               sizeof (my_fs_cnt), 1, &my_fs_cnt, tx));
           VERIFY0(zap_add(os, dd->dd_object, DD_FIELD_SNAPSHOT_COUNT,
               sizeof (my_ss_cnt), 1, &my_ss_cnt, tx));
   }
   
   static int
   dsl_dir_actv_fs_ss_limit_check(void *arg, dmu_tx_t *tx)
   {
           char *ddname = (char *)arg;
           dsl_pool_t *dp = dmu_tx_pool(tx);
           dsl_dataset_t *ds;
           dsl_dir_t *dd;
           int error;
   
           error = dsl_dataset_hold(dp, ddname, FTAG, &ds);
           if (error != 0)
                   return (error);
   
           if (!spa_feature_is_enabled(dp->dp_spa, SPA_FEATURE_FS_SS_LIMIT)) {
                   dsl_dataset_rele(ds, FTAG);
                   return (SET_ERROR(ENOTSUP));
           }
   
           dd = ds->ds_dir;
           if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_FS_SS_LIMIT) &&
               dsl_dir_is_zapified(dd) &&
               zap_contains(dp->dp_meta_objset, dd->dd_object,
               DD_FIELD_FILESYSTEM_COUNT) == 0) {
                   dsl_dataset_rele(ds, FTAG);
                   return (SET_ERROR(EALREADY));
           }
   
           dsl_dataset_rele(ds, FTAG);
           return (0);
   }
   
   static void
   dsl_dir_actv_fs_ss_limit_sync(void *arg, dmu_tx_t *tx)
   {
           char *ddname = (char *)arg;
           dsl_pool_t *dp = dmu_tx_pool(tx);
           dsl_dataset_t *ds;
           spa_t *spa;
   
           VERIFY0(dsl_dataset_hold(dp, ddname, FTAG, &ds));
   
           spa = dsl_dataset_get_spa(ds);
   
           if (!spa_feature_is_active(spa, SPA_FEATURE_FS_SS_LIMIT)) {
                   /*
                    * Since the feature was not active and we're now setting a
                    * limit, increment the feature-active counter so that the
                    * feature becomes active for the first time.
                    *
                    * We are already in a sync task so we can update the MOS.
                    */
                   spa_feature_incr(spa, SPA_FEATURE_FS_SS_LIMIT, tx);
           }
   
           /*
            * Since we are now setting a non-UINT64_MAX limit on the filesystem,
            * we need to ensure the counts are correct. Descend down the tree from
            * this point and update all of the counts to be accurate.
            */
           dsl_dir_init_fs_ss_count(ds->ds_dir, tx);
   
           dsl_dataset_rele(ds, FTAG);
   }
   
   /*
    * Make sure the feature is enabled and activate it if necessary.
    * Since we're setting a limit, ensure the on-disk counts are valid.
    * This is only called by the ioctl path when setting a limit value.
    *
    * We do not need to validate the new limit, since users who can change the
    * limit are also allowed to exceed the limit.
    */
   int
   dsl_dir_activate_fs_ss_limit(const char *ddname)
   {
           int error;
   
           error = dsl_sync_task(ddname, dsl_dir_actv_fs_ss_limit_check,
               dsl_dir_actv_fs_ss_limit_sync, (void *)ddname, 0,
               ZFS_SPACE_CHECK_RESERVED);
   
           if (error == EALREADY)
                   error = 0;
   
           return (error);
   }
   
   /*
    * Used to determine if the filesystem_limit or snapshot_limit should be
    * enforced. We allow the limit to be exceeded if the user has permission to
    * write the property value. We pass in the creds that we got in the open
    * context since we will always be the GZ root in syncing context. We also have
    * to handle the case where we are allowed to change the limit on the current
    * dataset, but there may be another limit in the tree above.
    *
    * We can never modify these two properties within a non-global zone. In
    * addition, the other checks are modeled on zfs_secpolicy_write_perms. We
    * can't use that function since we are already holding the dp_config_rwlock.
    * In addition, we already have the dd and dealing with snapshots is simplified
    * in this code.
    */
   
   typedef enum {
           ENFORCE_ALWAYS,
           ENFORCE_NEVER,
           ENFORCE_ABOVE
   } enforce_res_t;
   
   static enforce_res_t
   dsl_enforce_ds_ss_limits(dsl_dir_t *dd, zfs_prop_t prop,
       cred_t *cr, proc_t *proc)
   {
           enforce_res_t enforce = ENFORCE_ALWAYS;
           uint64_t obj;
           dsl_dataset_t *ds;
           uint64_t zoned;
           const char *zonedstr;
   
           ASSERT(prop == ZFS_PROP_FILESYSTEM_LIMIT ||
               prop == ZFS_PROP_SNAPSHOT_LIMIT);
   
   #ifdef _KERNEL
           if (crgetzoneid(cr) != GLOBAL_ZONEID)
                   return (ENFORCE_ALWAYS);
   
           /*
            * We are checking the saved credentials of the user process, which is
            * not the current process.  Note that we can't use secpolicy_zfs(),
            * because it only works if the cred is that of the current process (on
            * Linux).
            */
           if (secpolicy_zfs_proc(cr, proc) == 0)
                   return (ENFORCE_NEVER);
   #else
           (void) proc;
   #endif
   
           if ((obj = dsl_dir_phys(dd)->dd_head_dataset_obj) == 0)
                   return (ENFORCE_ALWAYS);
   
           ASSERT(dsl_pool_config_held(dd->dd_pool));
   
           if (dsl_dataset_hold_obj(dd->dd_pool, obj, FTAG, &ds) != 0)
                   return (ENFORCE_ALWAYS);
   
           zonedstr = zfs_prop_to_name(ZFS_PROP_ZONED);
           if (dsl_prop_get_ds(ds, zonedstr, 8, 1, &zoned, NULL) || zoned) {
                   /* Only root can access zoned fs's from the GZ */
                   enforce = ENFORCE_ALWAYS;
           } else {
                   if (dsl_deleg_access_impl(ds, zfs_prop_to_name(prop), cr) == 0)
                           enforce = ENFORCE_ABOVE;
           }
   
           dsl_dataset_rele(ds, FTAG);
           return (enforce);
   }
   
   /*
    * Check if adding additional child filesystem(s) would exceed any filesystem
    * limits or adding additional snapshot(s) would exceed any snapshot limits.
    * The prop argument indicates which limit to check.
    *
    * Note that all filesystem limits up to the root (or the highest
    * initialized) filesystem or the given ancestor must be satisfied.
    */
   int
   dsl_fs_ss_limit_check(dsl_dir_t *dd, uint64_t delta, zfs_prop_t prop,
       dsl_dir_t *ancestor, cred_t *cr, proc_t *proc)
   {
           objset_t *os = dd->dd_pool->dp_meta_objset;
           uint64_t limit, count;
           const char *count_prop;
           enforce_res_t enforce;
           int err = 0;
   
           ASSERT(dsl_pool_config_held(dd->dd_pool));
           ASSERT(prop == ZFS_PROP_FILESYSTEM_LIMIT ||
               prop == ZFS_PROP_SNAPSHOT_LIMIT);
   
           if (prop == ZFS_PROP_SNAPSHOT_LIMIT) {
                   /*
                    * We don't enforce the limit for temporary snapshots. This is
                    * indicated by a NULL cred_t argument.
                    */
                   if (cr == NULL)
                           return (0);
   
                   count_prop = DD_FIELD_SNAPSHOT_COUNT;
           } else {
                   count_prop = DD_FIELD_FILESYSTEM_COUNT;
           }
           /*
            * If we're allowed to change the limit, don't enforce the limit
            * e.g. this can happen if a snapshot is taken by an administrative
            * user in the global zone (i.e. a recursive snapshot by root).
            * However, we must handle the case of delegated permissions where we
            * are allowed to change the limit on the current dataset, but there
            * is another limit in the tree above.
            */
           enforce = dsl_enforce_ds_ss_limits(dd, prop, cr, proc);
           if (enforce == ENFORCE_NEVER)
                   return (0);
   
           /*
            * e.g. if renaming a dataset with no snapshots, count adjustment
            * is 0.
            */
           if (delta == 0)
                   return (0);
   
           /*
            * If an ancestor has been provided, stop checking the limit once we
            * hit that dir. We need this during rename so that we don't overcount
            * the check once we recurse up to the common ancestor.
            */
           if (ancestor == dd)
                   return (0);
   
           /*
            * If we hit an uninitialized node while recursing up the tree, we can
            * stop since we know there is no limit here (or above). The counts are
            * not valid on this node and we know we won't touch this node's counts.
            */
           if (!dsl_dir_is_zapified(dd))
                   return (0);
           err = zap_lookup(os, dd->dd_object,
               count_prop, sizeof (count), 1, &count);
           if (err == ENOENT)
                   return (0);
           if (err != 0)
                   return (err);
   
           err = dsl_prop_get_dd(dd, zfs_prop_to_name(prop), 8, 1, &limit, NULL,
               B_FALSE);
           if (err != 0)
                   return (err);
   
           /* Is there a limit which we've hit? */
           if (enforce == ENFORCE_ALWAYS && (count + delta) > limit)
                   return (SET_ERROR(EDQUOT));
   
           if (dd->dd_parent != NULL)
                   err = dsl_fs_ss_limit_check(dd->dd_parent, delta, prop,
                       ancestor, cr, proc);
   
           return (err);
   }
   
   /*
    * Adjust the filesystem or snapshot count for the specified dsl_dir_t and all
    * parents. When a new filesystem/snapshot is created, increment the count on
    * all parents, and when a filesystem/snapshot is destroyed, decrement the
    * count.
    */
   void
   dsl_fs_ss_count_adjust(dsl_dir_t *dd, int64_t delta, const char *prop,
       dmu_tx_t *tx)
   {
           int err;
           objset_t *os = dd->dd_pool->dp_meta_objset;
           uint64_t count;
   
           ASSERT(dsl_pool_config_held(dd->dd_pool));
           ASSERT(dmu_tx_is_syncing(tx));
           ASSERT(strcmp(prop, DD_FIELD_FILESYSTEM_COUNT) == 0 ||
               strcmp(prop, DD_FIELD_SNAPSHOT_COUNT) == 0);
   
           /*
            * We don't do accounting for hidden ($FREE, $MOS & $ORIGIN) objsets.
            */
           if (dd->dd_myname[0] == '$' && strcmp(prop,
               DD_FIELD_FILESYSTEM_COUNT) == 0) {
                   return;
           }
   
           /*
            * e.g. if renaming a dataset with no snapshots, count adjustment is 0
            */
           if (delta == 0)
                   return;
   
           /*
            * If we hit an uninitialized node while recursing up the tree, we can
            * stop since we know the counts are not valid on this node and we
            * know we shouldn't touch this node's counts. An uninitialized count
            * on the node indicates that either the feature has not yet been
            * activated or there are no limits on this part of the tree.
            */
           if (!dsl_dir_is_zapified(dd) || (err = zap_lookup(os, dd->dd_object,
               prop, sizeof (count), 1, &count)) == ENOENT)
                   return;
           VERIFY0(err);
   
           count += delta;
           /* Use a signed verify to make sure we're not neg. */
           VERIFY3S(count, >=, 0);
   
           VERIFY0(zap_update(os, dd->dd_object, prop, sizeof (count), 1, &count,
               tx));
   
           /* Roll up this additional count into our ancestors */
           if (dd->dd_parent != NULL)
                   dsl_fs_ss_count_adjust(dd->dd_parent, delta, prop, tx);
   }
   
   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 *ddphys;
           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) {
                   VERIFY0(zap_add(mos, dsl_dir_phys(pds)->dd_child_dir_zapobj,
                       name, sizeof (uint64_t), 1, &ddobj, tx));
           } else {
                   /* it's the root dir */
                   VERIFY0(zap_add(mos, DMU_POOL_DIRECTORY_OBJECT,
                       DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1, &ddobj, tx));
           }
           VERIFY0(dmu_bonus_hold(mos, ddobj, FTAG, &dbuf));
           dmu_buf_will_dirty(dbuf, tx);
           ddphys = dbuf->db_data;
   
           ddphys->dd_creation_time = gethrestime_sec();
           if (pds) {
                   ddphys->dd_parent_obj = pds->dd_object;
   
                   /* update the filesystem counts */
                   dsl_fs_ss_count_adjust(pds, 1, DD_FIELD_FILESYSTEM_COUNT, tx);
           }
           ddphys->dd_props_zapobj = zap_create(mos,
               DMU_OT_DSL_PROPS, DMU_OT_NONE, 0, tx);
           ddphys->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)
                   ddphys->dd_flags |= DD_FLAG_USED_BREAKDOWN;
   
           dmu_buf_rele(dbuf, FTAG);
   
           return (ddobj);
   }
   
   boolean_t
   dsl_dir_is_clone(dsl_dir_t *dd)
   {
           return (dsl_dir_phys(dd)->dd_origin_obj &&
               (dd->dd_pool->dp_origin_snap == NULL ||
              dsl_dir_phys(dd)->dd_origin_obj !=
              dd->dd_pool->dp_origin_snap->ds_object));
  }
  
  uint64_t
  dsl_dir_get_used(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_used_bytes);
  }
  
  uint64_t
  dsl_dir_get_compressed(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_compressed_bytes);
  }
  
  uint64_t
  dsl_dir_get_quota(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_quota);
  }
  
  uint64_t
  dsl_dir_get_reservation(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_reserved);
  }
  
  uint64_t
  dsl_dir_get_compressratio(dsl_dir_t *dd)
  {
          /* a fixed point number, 100x the ratio */
          return (dsl_dir_phys(dd)->dd_compressed_bytes == 0 ? 100 :
              (dsl_dir_phys(dd)->dd_uncompressed_bytes * 100 /
              dsl_dir_phys(dd)->dd_compressed_bytes));
  }
  
  uint64_t
  dsl_dir_get_logicalused(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_uncompressed_bytes);
  }
  
  uint64_t
  dsl_dir_get_usedsnap(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_used_breakdown[DD_USED_SNAP]);
  }
  
  uint64_t
  dsl_dir_get_usedds(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_used_breakdown[DD_USED_HEAD]);
  }
  
  uint64_t
  dsl_dir_get_usedrefreserv(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_used_breakdown[DD_USED_REFRSRV]);
  }
  
  uint64_t
  dsl_dir_get_usedchild(dsl_dir_t *dd)
  {
          return (dsl_dir_phys(dd)->dd_used_breakdown[DD_USED_CHILD] +
              dsl_dir_phys(dd)->dd_used_breakdown[DD_USED_CHILD_RSRV]);
  }
  
  void
  dsl_dir_get_origin(dsl_dir_t *dd, char *buf)
  {
          dsl_dataset_t *ds;
          VERIFY0(dsl_dataset_hold_obj(dd->dd_pool,
              dsl_dir_phys(dd)->dd_origin_obj, FTAG, &ds));
  
          dsl_dataset_name(ds, buf);
  
          dsl_dataset_rele(ds, FTAG);
  }
  
  int
  dsl_dir_get_filesystem_count(dsl_dir_t *dd, uint64_t *count)
  {
          if (dsl_dir_is_zapified(dd)) {
                  objset_t *os = dd->dd_pool->dp_meta_objset;
                  return (zap_lookup(os, dd->dd_object, DD_FIELD_FILESYSTEM_COUNT,
                      sizeof (*count), 1, count));
          } else {
                  return (SET_ERROR(ENOENT));
          }
  }
  
  int
  dsl_dir_get_snapshot_count(dsl_dir_t *dd, uint64_t *count)
  {
          if (dsl_dir_is_zapified(dd)) {
                  objset_t *os = dd->dd_pool->dp_meta_objset;
                  return (zap_lookup(os, dd->dd_object, DD_FIELD_SNAPSHOT_COUNT,
                      sizeof (*count), 1, count));
          } else {
                  return (SET_ERROR(ENOENT));
          }
  }
  
  void
  dsl_dir_stats(dsl_dir_t *dd, nvlist_t *nv)
  {
          mutex_enter(&dd->dd_lock);
          dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_QUOTA,
              dsl_dir_get_quota(dd));
          dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_RESERVATION,
              dsl_dir_get_reservation(dd));
          dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_LOGICALUSED,
              dsl_dir_get_logicalused(dd));
          if (dsl_dir_phys(dd)->dd_flags & DD_FLAG_USED_BREAKDOWN) {
                  dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDSNAP,
                      dsl_dir_get_usedsnap(dd));
                  dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDDS,
                      dsl_dir_get_usedds(dd));
                  dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDREFRESERV,
                      dsl_dir_get_usedrefreserv(dd));
                  dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_USEDCHILD,
                      dsl_dir_get_usedchild(dd));
          }
          mutex_exit(&dd->dd_lock);
  
          uint64_t count;
          if (dsl_dir_get_filesystem_count(dd, &count) == 0) {
                  dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_FILESYSTEM_COUNT,
                      count);
          }
          if (dsl_dir_get_snapshot_count(dd, &count) == 0) {
                  dsl_prop_nvlist_add_uint64(nv, ZFS_PROP_SNAPSHOT_COUNT,
                      count);
          }
  
          if (dsl_dir_is_clone(dd)) {
                  char buf[ZFS_MAX_DATASET_NAME_LEN];
                  dsl_dir_get_origin(dd, buf);
                  dsl_prop_nvlist_add_string(nv, ZFS_PROP_ORIGIN, buf);
          }
  
  }
  
  void
  dsl_dir_dirty(dsl_dir_t *dd, dmu_tx_t *tx)
  {
          dsl_pool_t *dp = dd->dd_pool;
  
          ASSERT(dsl_dir_phys(dd));
  
          if (txg_list_add(&dp->dp_dirty_dirs, dd, tx->tx_txg)) {
                  /* 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, dsl_dir_phys(dd)->dd_reserved);
          uint64_t new_accounted =
              MAX(used + delta, dsl_dir_phys(dd)->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));
  
          mutex_enter(&dd->dd_lock);
          ASSERT0(dd->dd_tempreserved[tx->tx_txg & TXG_MASK]);
          dprintf_dd(dd, "txg=%llu towrite=%lluK\n", (u_longlong_t)tx->tx_txg,
              (u_longlong_t)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;
  
          ASSERT(MUTEX_HELD(&dd->dd_lock));
  
          for (int i = 0; i < TXG_SIZE; i++)
                  space += dd->dd_space_towrite[i & TXG_MASK];
  
          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 (dsl_dir_phys(dd)->dd_quota != 0)
                  quota = dsl_dir_phys(dd)->dd_quota;
          used = dsl_dir_phys(dd)->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,
                      ZFS_SPACE_CHECK_NORMAL);
                  quota = MIN(quota, poolsize);
          }
  
          if (dsl_dir_phys(dd)->dd_reserved > used && parentspace != UINT64_MAX) {
                  /*
                   * We have some space reserved, in addition to what our
                   * parent gave us.
                   */
                  parentspace += dsl_dir_phys(dd)->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;
          } 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_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, list_t *tr_list,
      dmu_tx_t *tx, boolean_t first)
  {
          uint64_t txg;
          uint64_t quota;
          struct tempreserve *tr;
          int retval;
          uint64_t ext_quota;
          uint64_t ref_rsrv;
  
  top_of_function:
          txg = tx->tx_txg;
          retval = EDQUOT;
          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.
           */
          uint64_t est_inflight = dsl_dir_space_towrite(dd);
          for (int i = 0; i < TXG_SIZE; i++)
                  est_inflight += dd->dd_tempreserved[i];
          uint64_t used_on_disk = dsl_dir_phys(dd)->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_dsl_dataset;
  
                  error = dsl_dataset_check_quota(ds, !netfree,
                      asize, est_inflight, &used_on_disk, &ref_rsrv);
                  if (error != 0) {
                          mutex_exit(&dd->dd_lock);
                          DMU_TX_STAT_BUMP(dmu_tx_quota);
                          return (error);
                  }
          }
  
          /*
           * If this transaction will result in a net free of space,
           * we want to let it through.
           */
          if (ignorequota || netfree || dsl_dir_phys(dd)->dd_quota == 0 ||
              (tx->tx_objset && dmu_objset_type(tx->tx_objset) == DMU_OST_ZVOL &&
              zvol_enforce_quotas == B_FALSE))
                  quota = UINT64_MAX;
          else
                  quota = dsl_dir_phys(dd)->dd_quota;
  
          /*
           * Adjust the quota against the actual pool size at the root
           * minus any outstanding deferred frees.
           * 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 avail = dsl_pool_unreserved_space(dd->dd_pool,
                      (netfree) ?
                      ZFS_SPACE_CHECK_RESERVED : ZFS_SPACE_CHECK_NORMAL);
  
                  if (avail < quota) {
                          quota = avail;
                          retval = SET_ERROR(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
           * or deferred frees (which may free up space for us).
           */
          ext_quota = quota >> 5;
          if (quota == UINT64_MAX)
                  ext_quota = 0;
  
          if (used_on_disk >= quota) {
                  /* Quota exceeded */
                  mutex_exit(&dd->dd_lock);
                  DMU_TX_STAT_BUMP(dmu_tx_quota);
                  return (retval);
          } else if (used_on_disk + est_inflight >= quota + ext_quota) {
                  if (est_inflight > 0 || used_on_disk < quota) {
                          retval = SET_ERROR(ERESTART);
                  } else {
                          ASSERT3U(used_on_disk, >=, quota);
  
                          if (retval == ENOSPC && (used_on_disk - quota) <
                              dsl_pool_deferred_space(dd->dd_pool)) {
                                  retval = SET_ERROR(ERESTART);
                          }
                  }
  
                  dprintf_dd(dd, "failing: used=%lluK inflight = %lluK "
                      "quota=%lluK tr=%lluK err=%d\n",
                      (u_longlong_t)used_on_disk>>10,
                      (u_longlong_t)est_inflight>>10,
                      (u_longlong_t)quota>>10, (u_longlong_t)asize>>10, retval);
                  mutex_exit(&dd->dd_lock);
                  DMU_TX_STAT_BUMP(dmu_tx_quota);
                  return (retval);
          }
  
          /* We need to up our estimated delta before dropping dd_lock */
          dd->dd_tempreserved[txg & TXG_MASK] += asize;
  
          uint64_t 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 != NULL && parent_rsrv != 0) {
                  /*
                   * Recurse on our parent without recursion. This has been
                   * observed to be potentially large stack usage even within
                   * the test suite. Largest seen stack was 7632 bytes on linux.
                   */
  
                  dd = dd->dd_parent;
                  asize = parent_rsrv;
                  ignorequota = (dsl_dir_phys(dd)->dd_head_dataset_obj == 0);
                  first = B_FALSE;
                  goto top_of_function;
          }
  
          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,
      boolean_t netfree, 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);
  
          err = arc_tempreserve_space(dd->dd_pool->dp_spa, 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);
          } else {
                  if (err == EAGAIN) {
                          /*
                           * If arc_memory_throttle() detected that pageout
                           * is running and we are low on memory, we delay new
                           * non-pageout transactions to give pageout an
                           * advantage.
                           *
                           * It is unfortunate to be delaying while the caller's
                           * locks are held.
                           */
                          txg_delay(dd->dd_pool, tx->tx_txg,
                              MSEC2NSEC(10), MSEC2NSEC(10));
                          err = SET_ERROR(ERESTART);
                  }
          }
  
          if (err == 0) {
                  err = dsl_dir_tempreserve_impl(dd, asize, netfree,
                      B_FALSE, tr_list, tx, B_TRUE);
          }
  
          if (err != 0)
                  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)) != NULL) {
                  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));
  }
  
  /*
   * This should be called from open context when we think we're going to write
   * or free space, for example when dirtying data. Be conservative; it's okay
   * to write less space or free more, but we don't want to write more or free
   * less than the amount specified.
   *
   * NOTE: The behavior of this function is identical to the Illumos / FreeBSD
   * version however it has been adjusted to use an iterative rather than
   * recursive algorithm to minimize stack usage.
   */
  void
  dsl_dir_willuse_space(dsl_dir_t *dd, int64_t space, dmu_tx_t *tx)
  {
          int64_t parent_space;
          uint64_t est_used;
  
          do {
                  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) +
                      dsl_dir_phys(dd)->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);
  
                  dd = dd->dd_parent;
                  space = parent_space;
          } while (space && dd);
  }
  
  /* 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;
  
          ASSERT(dmu_tx_is_syncing(tx));
          ASSERT(type < DD_USED_NUM);
  
          dmu_buf_will_dirty(dd->dd_dbuf, tx);
  
          /*
           * dsl_dataset_set_refreservation_sync_impl() calls this with
           * dd_lock held, so that it can atomically update
           * ds->ds_reserved and the dsl_dir accounting, so that
           * dsl_dataset_check_quota() can see dataset and dir accounting
           * consistently.
           */
          boolean_t needlock = !MUTEX_HELD(&dd->dd_lock);
          if (needlock)
                  mutex_enter(&dd->dd_lock);
          dsl_dir_phys_t *ddp = dsl_dir_phys(dd);
          accounted_delta = parent_delta(dd, ddp->dd_used_bytes, used);
          ASSERT(used >= 0 || ddp->dd_used_bytes >= -used);
          ASSERT(compressed >= 0 || ddp->dd_compressed_bytes >= -compressed);
          ASSERT(uncompressed >= 0 ||
              ddp->dd_uncompressed_bytes >= -uncompressed);
          ddp->dd_used_bytes += used;
          ddp->dd_uncompressed_bytes += uncompressed;
          ddp->dd_compressed_bytes += compressed;
  
          if (ddp->dd_flags & DD_FLAG_USED_BREAKDOWN) {
                  ASSERT(used >= 0 || ddp->dd_used_breakdown[type] >= -used);
                  ddp->dd_used_breakdown[type] += used;
  #ifdef ZFS_DEBUG
                  {
                          dd_used_t t;
                          uint64_t u = 0;
                          for (t = 0; t < DD_USED_NUM; t++)
                                  u += ddp->dd_used_breakdown[t];
                          ASSERT3U(u, ==, ddp->dd_used_bytes);
                  }
  #endif
          }
          if (needlock)
                  mutex_exit(&dd->dd_lock);
  
          if (dd->dd_parent != NULL) {
                  dsl_dir_diduse_transfer_space(dd->dd_parent,
                      accounted_delta, compressed, uncompressed,
                      used, 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)
  {
          ASSERT(dmu_tx_is_syncing(tx));
          ASSERT(oldtype < DD_USED_NUM);
          ASSERT(newtype < DD_USED_NUM);
  
          dsl_dir_phys_t *ddp = dsl_dir_phys(dd);
          if (delta == 0 ||
              !(ddp->dd_flags & DD_FLAG_USED_BREAKDOWN))
                  return;
  
          dmu_buf_will_dirty(dd->dd_dbuf, tx);
          mutex_enter(&dd->dd_lock);
          ASSERT(delta > 0 ?
              ddp->dd_used_breakdown[oldtype] >= delta :
              ddp->dd_used_breakdown[newtype] >= -delta);
          ASSERT(ddp->dd_used_bytes >= ABS(delta));
          ddp->dd_used_breakdown[oldtype] -= delta;
          ddp->dd_used_breakdown[newtype] += delta;
          mutex_exit(&dd->dd_lock);
  }
  
  void
  dsl_dir_diduse_transfer_space(dsl_dir_t *dd, int64_t used,
      int64_t compressed, int64_t uncompressed, int64_t tonew,
      dd_used_t oldtype, dd_used_t newtype, dmu_tx_t *tx)
  {
          int64_t accounted_delta;
  
          ASSERT(dmu_tx_is_syncing(tx));
          ASSERT(oldtype < DD_USED_NUM);
          ASSERT(newtype < DD_USED_NUM);
  
          dmu_buf_will_dirty(dd->dd_dbuf, tx);
  
          mutex_enter(&dd->dd_lock);
          dsl_dir_phys_t *ddp = dsl_dir_phys(dd);
          accounted_delta = parent_delta(dd, ddp->dd_used_bytes, used);
          ASSERT(used >= 0 || ddp->dd_used_bytes >= -used);
          ASSERT(compressed >= 0 || ddp->dd_compressed_bytes >= -compressed);
          ASSERT(uncompressed >= 0 ||
              ddp->dd_uncompressed_bytes >= -uncompressed);
          ddp->dd_used_bytes += used;
          ddp->dd_uncompressed_bytes += uncompressed;
          ddp->dd_compressed_bytes += compressed;
  
          if (ddp->dd_flags & DD_FLAG_USED_BREAKDOWN) {
                  ASSERT(tonew - used <= 0 ||
                      ddp->dd_used_breakdown[oldtype] >= tonew - used);
                  ASSERT(tonew >= 0 ||
                      ddp->dd_used_breakdown[newtype] >= -tonew);
                  ddp->dd_used_breakdown[oldtype] -= tonew - used;
                  ddp->dd_used_breakdown[newtype] += tonew;
  #ifdef ZFS_DEBUG
                  {
                          dd_used_t t;
                          uint64_t u = 0;
                          for (t = 0; t < DD_USED_NUM; t++)
                                  u += ddp->dd_used_breakdown[t];
                          ASSERT3U(u, ==, ddp->dd_used_bytes);
                  }
  #endif
          }
          mutex_exit(&dd->dd_lock);
  
          if (dd->dd_parent != NULL) {
                  dsl_dir_diduse_transfer_space(dd->dd_parent,
                      accounted_delta, compressed, uncompressed,
                      used, DD_USED_CHILD_RSRV, DD_USED_CHILD, tx);
          }
  }
  
  typedef struct dsl_dir_set_qr_arg {
          const char *ddsqra_name;
          zprop_source_t ddsqra_source;
          uint64_t ddsqra_value;
  } dsl_dir_set_qr_arg_t;
  
  static int
  dsl_dir_set_quota_check(void *arg, dmu_tx_t *tx)
  {
          dsl_dir_set_qr_arg_t *ddsqra = arg;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          dsl_dataset_t *ds;
          int error;
          uint64_t towrite, newval;
  
          error = dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds);
          if (error != 0)
                  return (error);
  
          error = dsl_prop_predict(ds->ds_dir, "quota",
              ddsqra->ddsqra_source, ddsqra->ddsqra_value, &newval);
          if (error != 0) {
                  dsl_dataset_rele(ds, FTAG);
                  return (error);
          }
  
          if (newval == 0) {
                  dsl_dataset_rele(ds, FTAG);
                  return (0);
          }
  
          mutex_enter(&ds->ds_dir->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(ds->ds_dir);
          if ((dmu_tx_is_syncing(tx) || towrite == 0) &&
              (newval < dsl_dir_phys(ds->ds_dir)->dd_reserved ||
              newval < dsl_dir_phys(ds->ds_dir)->dd_used_bytes + towrite)) {
                  error = SET_ERROR(ENOSPC);
          }
          mutex_exit(&ds->ds_dir->dd_lock);
          dsl_dataset_rele(ds, FTAG);
          return (error);
  }
  
  static void
  dsl_dir_set_quota_sync(void *arg, dmu_tx_t *tx)
  {
          dsl_dir_set_qr_arg_t *ddsqra = arg;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          dsl_dataset_t *ds;
          uint64_t newval;
  
          VERIFY0(dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds));
  
          if (spa_version(dp->dp_spa) >= SPA_VERSION_RECVD_PROPS) {
                  dsl_prop_set_sync_impl(ds, zfs_prop_to_name(ZFS_PROP_QUOTA),
                      ddsqra->ddsqra_source, sizeof (ddsqra->ddsqra_value), 1,
                      &ddsqra->ddsqra_value, tx);
  
                  VERIFY0(dsl_prop_get_int_ds(ds,
                      zfs_prop_to_name(ZFS_PROP_QUOTA), &newval));
          } else {
                  newval = ddsqra->ddsqra_value;
                  spa_history_log_internal_ds(ds, "set", tx, "%s=%lld",
                      zfs_prop_to_name(ZFS_PROP_QUOTA), (longlong_t)newval);
          }
  
          dmu_buf_will_dirty(ds->ds_dir->dd_dbuf, tx);
          mutex_enter(&ds->ds_dir->dd_lock);
          dsl_dir_phys(ds->ds_dir)->dd_quota = newval;
          mutex_exit(&ds->ds_dir->dd_lock);
          dsl_dataset_rele(ds, FTAG);
  }
  
  int
  dsl_dir_set_quota(const char *ddname, zprop_source_t source, uint64_t quota)
  {
          dsl_dir_set_qr_arg_t ddsqra;
  
          ddsqra.ddsqra_name = ddname;
          ddsqra.ddsqra_source = source;
          ddsqra.ddsqra_value = quota;
  
          return (dsl_sync_task(ddname, dsl_dir_set_quota_check,
              dsl_dir_set_quota_sync, &ddsqra, 0,
              ZFS_SPACE_CHECK_EXTRA_RESERVED));
  }
  
  static int
  dsl_dir_set_reservation_check(void *arg, dmu_tx_t *tx)
  {
          dsl_dir_set_qr_arg_t *ddsqra = arg;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          dsl_dataset_t *ds;
          dsl_dir_t *dd;
          uint64_t newval, used, avail;
          int error;
  
          error = dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds);
          if (error != 0)
                  return (error);
          dd = ds->ds_dir;
  
          /*
           * If we are doing the preliminary check in open context, the
           * space estimates may be inaccurate.
           */
          if (!dmu_tx_is_syncing(tx)) {
                  dsl_dataset_rele(ds, FTAG);
                  return (0);
          }
  
          error = dsl_prop_predict(ds->ds_dir,
              zfs_prop_to_name(ZFS_PROP_RESERVATION),
              ddsqra->ddsqra_source, ddsqra->ddsqra_value, &newval);
          if (error != 0) {
                  dsl_dataset_rele(ds, FTAG);
                  return (error);
          }
  
          mutex_enter(&dd->dd_lock);
          used = dsl_dir_phys(dd)->dd_used_bytes;
          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,
                      ZFS_SPACE_CHECK_NORMAL) - used;
          }
  
          if (MAX(used, newval) > MAX(used, dsl_dir_phys(dd)->dd_reserved)) {
                  uint64_t delta = MAX(used, newval) -
                      MAX(used, dsl_dir_phys(dd)->dd_reserved);
  
                  if (delta > avail ||
                      (dsl_dir_phys(dd)->dd_quota > 0 &&
                      newval > dsl_dir_phys(dd)->dd_quota))
                          error = SET_ERROR(ENOSPC);
          }
  
          dsl_dataset_rele(ds, FTAG);
          return (error);
  }
  
  void
  dsl_dir_set_reservation_sync_impl(dsl_dir_t *dd, uint64_t value, dmu_tx_t *tx)
  {
          uint64_t used;
          int64_t delta;
  
          dmu_buf_will_dirty(dd->dd_dbuf, tx);
  
          mutex_enter(&dd->dd_lock);
          used = dsl_dir_phys(dd)->dd_used_bytes;
          delta = MAX(used, value) - MAX(used, dsl_dir_phys(dd)->dd_reserved);
          dsl_dir_phys(dd)->dd_reserved = value;
  
          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);
  }
  
  static void
  dsl_dir_set_reservation_sync(void *arg, dmu_tx_t *tx)
  {
          dsl_dir_set_qr_arg_t *ddsqra = arg;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          dsl_dataset_t *ds;
          uint64_t newval;
  
          VERIFY0(dsl_dataset_hold(dp, ddsqra->ddsqra_name, FTAG, &ds));
  
          if (spa_version(dp->dp_spa) >= SPA_VERSION_RECVD_PROPS) {
                  dsl_prop_set_sync_impl(ds,
                      zfs_prop_to_name(ZFS_PROP_RESERVATION),
                      ddsqra->ddsqra_source, sizeof (ddsqra->ddsqra_value), 1,
                      &ddsqra->ddsqra_value, tx);
  
                  VERIFY0(dsl_prop_get_int_ds(ds,
                      zfs_prop_to_name(ZFS_PROP_RESERVATION), &newval));
          } else {
                  newval = ddsqra->ddsqra_value;
                  spa_history_log_internal_ds(ds, "set", tx, "%s=%lld",
                      zfs_prop_to_name(ZFS_PROP_RESERVATION),
                      (longlong_t)newval);
          }
  
          dsl_dir_set_reservation_sync_impl(ds->ds_dir, newval, tx);
          dsl_dataset_rele(ds, FTAG);
  }
  
  int
  dsl_dir_set_reservation(const char *ddname, zprop_source_t source,
      uint64_t reservation)
  {
          dsl_dir_set_qr_arg_t ddsqra;
  
          ddsqra.ddsqra_name = ddname;
          ddsqra.ddsqra_source = source;
          ddsqra.ddsqra_value = reservation;
  
          return (dsl_sync_task(ddname, dsl_dir_set_reservation_check,
              dsl_dir_set_reservation_sync, &ddsqra, 0,
              ZFS_SPACE_CHECK_EXTRA_RESERVED));
  }
  
  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, dsl_dir_phys(dd)->dd_used_bytes, delta);
          mutex_exit(&dd->dd_lock);
          return (would_change(dd->dd_parent, delta, ancestor));
  }
  
  typedef struct dsl_dir_rename_arg {
          const char *ddra_oldname;
          const char *ddra_newname;
          cred_t *ddra_cred;
          proc_t *ddra_proc;
  } dsl_dir_rename_arg_t;
  
  typedef struct dsl_valid_rename_arg {
          int char_delta;
          int nest_delta;
  } dsl_valid_rename_arg_t;
  
  static int
  dsl_valid_rename(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg)
  {
          (void) dp;
          dsl_valid_rename_arg_t *dvra = arg;
          char namebuf[ZFS_MAX_DATASET_NAME_LEN];
  
          dsl_dataset_name(ds, namebuf);
  
          ASSERT3U(strnlen(namebuf, ZFS_MAX_DATASET_NAME_LEN),
              <, ZFS_MAX_DATASET_NAME_LEN);
          int namelen = strlen(namebuf) + dvra->char_delta;
          int depth = get_dataset_depth(namebuf) + dvra->nest_delta;
  
          if (namelen >= ZFS_MAX_DATASET_NAME_LEN)
                  return (SET_ERROR(ENAMETOOLONG));
          if (dvra->nest_delta > 0 && depth >= zfs_max_dataset_nesting)
                  return (SET_ERROR(ENAMETOOLONG));
          return (0);
  }
  
  static int
  dsl_dir_rename_check(void *arg, dmu_tx_t *tx)
  {
          dsl_dir_rename_arg_t *ddra = arg;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          dsl_dir_t *dd, *newparent;
          dsl_valid_rename_arg_t dvra;
          dsl_dataset_t *parentds;
          objset_t *parentos;
          const char *mynewname;
          int error;
  
          /* target dir should exist */
          error = dsl_dir_hold(dp, ddra->ddra_oldname, FTAG, &dd, NULL);
          if (error != 0)
                  return (error);
  
          /* new parent should exist */
          error = dsl_dir_hold(dp, ddra->ddra_newname, FTAG,
              &newparent, &mynewname);
          if (error != 0) {
                  dsl_dir_rele(dd, FTAG);
                  return (error);
          }
  
          /* can't rename to different pool */
          if (dd->dd_pool != newparent->dd_pool) {
                  dsl_dir_rele(newparent, FTAG);
                  dsl_dir_rele(dd, FTAG);
                  return (SET_ERROR(EXDEV));
          }
  
          /* new name should not already exist */
          if (mynewname == NULL) {
                  dsl_dir_rele(newparent, FTAG);
                  dsl_dir_rele(dd, FTAG);
                  return (SET_ERROR(EEXIST));
          }
  
          /* can't rename below anything but filesystems (eg. no ZVOLs) */
          error = dsl_dataset_hold_obj(newparent->dd_pool,
              dsl_dir_phys(newparent)->dd_head_dataset_obj, FTAG, &parentds);
          if (error != 0) {
                  dsl_dir_rele(newparent, FTAG);
                  dsl_dir_rele(dd, FTAG);
                  return (error);
          }
          error = dmu_objset_from_ds(parentds, &parentos);
          if (error != 0) {
                  dsl_dataset_rele(parentds, FTAG);
                  dsl_dir_rele(newparent, FTAG);
                  dsl_dir_rele(dd, FTAG);
                  return (error);
          }
          if (dmu_objset_type(parentos) != DMU_OST_ZFS) {
                  dsl_dataset_rele(parentds, FTAG);
                  dsl_dir_rele(newparent, FTAG);
                  dsl_dir_rele(dd, FTAG);
                  return (SET_ERROR(ZFS_ERR_WRONG_PARENT));
          }
          dsl_dataset_rele(parentds, FTAG);
  
          ASSERT3U(strnlen(ddra->ddra_newname, ZFS_MAX_DATASET_NAME_LEN),
              <, ZFS_MAX_DATASET_NAME_LEN);
          ASSERT3U(strnlen(ddra->ddra_oldname, ZFS_MAX_DATASET_NAME_LEN),
              <, ZFS_MAX_DATASET_NAME_LEN);
          dvra.char_delta = strlen(ddra->ddra_newname)
              - strlen(ddra->ddra_oldname);
          dvra.nest_delta = get_dataset_depth(ddra->ddra_newname)
              - get_dataset_depth(ddra->ddra_oldname);
  
          /* if the name length is growing, validate child name lengths */
          if (dvra.char_delta > 0 || dvra.nest_delta > 0) {
                  error = dmu_objset_find_dp(dp, dd->dd_object, dsl_valid_rename,
                      &dvra, DS_FIND_CHILDREN | DS_FIND_SNAPSHOTS);
                  if (error != 0) {
                          dsl_dir_rele(newparent, FTAG);
                          dsl_dir_rele(dd, FTAG);
                          return (error);
                  }
          }
  
          if (dmu_tx_is_syncing(tx)) {
                  if (spa_feature_is_active(dp->dp_spa,
                      SPA_FEATURE_FS_SS_LIMIT)) {
                          /*
                           * Although this is the check function and we don't
                           * normally make on-disk changes in check functions,
                           * we need to do that here.
                           *
                           * Ensure this portion of the tree's counts have been
                           * initialized in case the new parent has limits set.
                           */
                          dsl_dir_init_fs_ss_count(dd, tx);
                  }
          }
  
          if (newparent != dd->dd_parent) {
                  /* is there enough space? */
                  uint64_t myspace =
                      MAX(dsl_dir_phys(dd)->dd_used_bytes,
                      dsl_dir_phys(dd)->dd_reserved);
                  objset_t *os = dd->dd_pool->dp_meta_objset;
                  uint64_t fs_cnt = 0;
                  uint64_t ss_cnt = 0;
  
                  if (dsl_dir_is_zapified(dd)) {
                          int err;
  
                          err = zap_lookup(os, dd->dd_object,
                              DD_FIELD_FILESYSTEM_COUNT, sizeof (fs_cnt), 1,
                              &fs_cnt);
                          if (err != ENOENT && err != 0) {
                                  dsl_dir_rele(newparent, FTAG);
                                  dsl_dir_rele(dd, FTAG);
                                  return (err);
                          }
  
                          /*
                           * have to add 1 for the filesystem itself that we're
                           * moving
                           */
                          fs_cnt++;
  
                          err = zap_lookup(os, dd->dd_object,
                              DD_FIELD_SNAPSHOT_COUNT, sizeof (ss_cnt), 1,
                              &ss_cnt);
                          if (err != ENOENT && err != 0) {
                                  dsl_dir_rele(newparent, FTAG);
                                  dsl_dir_rele(dd, FTAG);
                                  return (err);
                          }
                  }
  
                  /* check for encryption errors */
                  error = dsl_dir_rename_crypt_check(dd, newparent);
                  if (error != 0) {
                          dsl_dir_rele(newparent, FTAG);
                          dsl_dir_rele(dd, FTAG);
                          return (SET_ERROR(EACCES));
                  }
  
                  /* no rename into our descendant */
                  if (closest_common_ancestor(dd, newparent) == dd) {
                          dsl_dir_rele(newparent, FTAG);
                          dsl_dir_rele(dd, FTAG);
                          return (SET_ERROR(EINVAL));
                  }
  
                  error = dsl_dir_transfer_possible(dd->dd_parent,
                      newparent, fs_cnt, ss_cnt, myspace,
                      ddra->ddra_cred, ddra->ddra_proc);
                  if (error != 0) {
                          dsl_dir_rele(newparent, FTAG);
                          dsl_dir_rele(dd, FTAG);
                          return (error);
                  }
          }
  
          dsl_dir_rele(newparent, FTAG);
          dsl_dir_rele(dd, FTAG);
          return (0);
  }
  
  static void
  dsl_dir_rename_sync(void *arg, dmu_tx_t *tx)
  {
          dsl_dir_rename_arg_t *ddra = arg;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          dsl_dir_t *dd, *newparent;
          const char *mynewname;
          objset_t *mos = dp->dp_meta_objset;
  
          VERIFY0(dsl_dir_hold(dp, ddra->ddra_oldname, FTAG, &dd, NULL));
          VERIFY0(dsl_dir_hold(dp, ddra->ddra_newname, FTAG, &newparent,
              &mynewname));
  
          /* Log this before we change the name. */
          spa_history_log_internal_dd(dd, "rename", tx,
              "-> %s", ddra->ddra_newname);
  
          if (newparent != dd->dd_parent) {
                  objset_t *os = dd->dd_pool->dp_meta_objset;
                  uint64_t fs_cnt = 0;
                  uint64_t ss_cnt = 0;
  
                  /*
                   * We already made sure the dd counts were initialized in the
                   * check function.
                   */
                  if (spa_feature_is_active(dp->dp_spa,
                      SPA_FEATURE_FS_SS_LIMIT)) {
                          VERIFY0(zap_lookup(os, dd->dd_object,
                              DD_FIELD_FILESYSTEM_COUNT, sizeof (fs_cnt), 1,
                              &fs_cnt));
                          /* add 1 for the filesystem itself that we're moving */
                          fs_cnt++;
  
                          VERIFY0(zap_lookup(os, dd->dd_object,
                              DD_FIELD_SNAPSHOT_COUNT, sizeof (ss_cnt), 1,
                              &ss_cnt));
                  }
  
                  dsl_fs_ss_count_adjust(dd->dd_parent, -fs_cnt,
                      DD_FIELD_FILESYSTEM_COUNT, tx);
                  dsl_fs_ss_count_adjust(newparent, fs_cnt,
                      DD_FIELD_FILESYSTEM_COUNT, tx);
  
                  dsl_fs_ss_count_adjust(dd->dd_parent, -ss_cnt,
                      DD_FIELD_SNAPSHOT_COUNT, tx);
                  dsl_fs_ss_count_adjust(newparent, ss_cnt,
                      DD_FIELD_SNAPSHOT_COUNT, tx);
  
                  dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD,
                      -dsl_dir_phys(dd)->dd_used_bytes,
                      -dsl_dir_phys(dd)->dd_compressed_bytes,
                      -dsl_dir_phys(dd)->dd_uncompressed_bytes, tx);
                  dsl_dir_diduse_space(newparent, DD_USED_CHILD,
                      dsl_dir_phys(dd)->dd_used_bytes,
                      dsl_dir_phys(dd)->dd_compressed_bytes,
                      dsl_dir_phys(dd)->dd_uncompressed_bytes, tx);
  
                  if (dsl_dir_phys(dd)->dd_reserved >
                      dsl_dir_phys(dd)->dd_used_bytes) {
                          uint64_t unused_rsrv = dsl_dir_phys(dd)->dd_reserved -
                              dsl_dir_phys(dd)->dd_used_bytes;
  
                          dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD_RSRV,
                              -unused_rsrv, 0, 0, tx);
                          dsl_dir_diduse_space(newparent, DD_USED_CHILD_RSRV,
                              unused_rsrv, 0, 0, tx);
                  }
          }
  
          dmu_buf_will_dirty(dd->dd_dbuf, tx);
  
          /* remove from old parent zapobj */
          VERIFY0(zap_remove(mos,
              dsl_dir_phys(dd->dd_parent)->dd_child_dir_zapobj,
              dd->dd_myname, tx));
  
          (void) strlcpy(dd->dd_myname, mynewname,
              sizeof (dd->dd_myname));
          dsl_dir_rele(dd->dd_parent, dd);
          dsl_dir_phys(dd)->dd_parent_obj = newparent->dd_object;
          VERIFY0(dsl_dir_hold_obj(dp,
              newparent->dd_object, NULL, dd, &dd->dd_parent));
  
          /* add to new parent zapobj */
          VERIFY0(zap_add(mos, dsl_dir_phys(newparent)->dd_child_dir_zapobj,
              dd->dd_myname, 8, 1, &dd->dd_object, tx));
  
          /* TODO: A rename callback to avoid these layering violations. */
          zfsvfs_update_fromname(ddra->ddra_oldname, ddra->ddra_newname);
          zvol_rename_minors(dp->dp_spa, ddra->ddra_oldname,
              ddra->ddra_newname, B_TRUE);
  
          dsl_prop_notify_all(dd);
  
          dsl_dir_rele(newparent, FTAG);
          dsl_dir_rele(dd, FTAG);
  }
  
  int
  dsl_dir_rename(const char *oldname, const char *newname)
  {
          dsl_dir_rename_arg_t ddra;
  
          ddra.ddra_oldname = oldname;
          ddra.ddra_newname = newname;
          ddra.ddra_cred = CRED();
          ddra.ddra_proc = curproc;
  
          return (dsl_sync_task(oldname,
              dsl_dir_rename_check, dsl_dir_rename_sync, &ddra,
              3, ZFS_SPACE_CHECK_RESERVED));
  }
  
  int
  dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd,
      uint64_t fs_cnt, uint64_t ss_cnt, uint64_t space,
      cred_t *cr, proc_t *proc)
  {
          dsl_dir_t *ancestor;
          int64_t adelta;
          uint64_t avail;
          int err;
  
          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 (SET_ERROR(ENOSPC));
  
          err = dsl_fs_ss_limit_check(tdd, fs_cnt, ZFS_PROP_FILESYSTEM_LIMIT,
              ancestor, cr, proc);
          if (err != 0)
                  return (err);
          err = dsl_fs_ss_limit_check(tdd, ss_cnt, ZFS_PROP_SNAPSHOT_LIMIT,
              ancestor, cr, proc);
          if (err != 0)
                  return (err);
  
          return (0);
  }
  
  inode_timespec_t
  dsl_dir_snap_cmtime(dsl_dir_t *dd)
  {
          inode_timespec_t t;
  
          mutex_enter(&dd->dd_lock);
          t = dd->dd_snap_cmtime;
          mutex_exit(&dd->dd_lock);
  
          return (t);
  }
  
  void
  dsl_dir_snap_cmtime_update(dsl_dir_t *dd, dmu_tx_t *tx)
  {
          dsl_pool_t *dp = dmu_tx_pool(tx);
          inode_timespec_t t;
          gethrestime(&t);
  
          mutex_enter(&dd->dd_lock);
          dd->dd_snap_cmtime = t;
          if (spa_feature_is_enabled(dp->dp_spa,
              SPA_FEATURE_EXTENSIBLE_DATASET)) {
                  objset_t *mos = dd->dd_pool->dp_meta_objset;
                  uint64_t ddobj = dd->dd_object;
                  dsl_dir_zapify(dd, tx);
                  VERIFY0(zap_update(mos, ddobj,
                      DD_FIELD_SNAPSHOTS_CHANGED,
                      sizeof (uint64_t),
                      sizeof (inode_timespec_t) / sizeof (uint64_t),
                      &t, tx));
          }
          mutex_exit(&dd->dd_lock);
  }
  
  void
  dsl_dir_zapify(dsl_dir_t *dd, dmu_tx_t *tx)
  {
          objset_t *mos = dd->dd_pool->dp_meta_objset;
          dmu_object_zapify(mos, dd->dd_object, DMU_OT_DSL_DIR, tx);
  }
  
  boolean_t
  dsl_dir_is_zapified(dsl_dir_t *dd)
  {
          dmu_object_info_t doi;
  
          dmu_object_info_from_db(dd->dd_dbuf, &doi);
          return (doi.doi_type == DMU_OTN_ZAP_METADATA);
  }
  
  void
  dsl_dir_livelist_open(dsl_dir_t *dd, uint64_t obj)
  {
          objset_t *mos = dd->dd_pool->dp_meta_objset;
          ASSERT(spa_feature_is_active(dd->dd_pool->dp_spa,
              SPA_FEATURE_LIVELIST));
          dsl_deadlist_open(&dd->dd_livelist, mos, obj);
          bplist_create(&dd->dd_pending_allocs);
          bplist_create(&dd->dd_pending_frees);
  }
  
  void
  dsl_dir_livelist_close(dsl_dir_t *dd)
  {
          dsl_deadlist_close(&dd->dd_livelist);
          bplist_destroy(&dd->dd_pending_allocs);
          bplist_destroy(&dd->dd_pending_frees);
  }
  
  void
  dsl_dir_remove_livelist(dsl_dir_t *dd, dmu_tx_t *tx, boolean_t total)
  {
          uint64_t obj;
          dsl_pool_t *dp = dmu_tx_pool(tx);
          spa_t *spa = dp->dp_spa;
          livelist_condense_entry_t to_condense = spa->spa_to_condense;
  
          if (!dsl_deadlist_is_open(&dd->dd_livelist))
                  return;
  
          /*
           * If the livelist being removed is set to be condensed, stop the
           * condense zthr and indicate the cancellation in the spa_to_condense
           * struct in case the condense no-wait synctask has already started
           */
          zthr_t *ll_condense_thread = spa->spa_livelist_condense_zthr;
          if (ll_condense_thread != NULL &&
              (to_condense.ds != NULL) && (to_condense.ds->ds_dir == dd)) {
                  /*
                   * We use zthr_wait_cycle_done instead of zthr_cancel
                   * because we don't want to destroy the zthr, just have
                   * it skip its current task.
                   */
                  spa->spa_to_condense.cancelled = B_TRUE;
                  zthr_wait_cycle_done(ll_condense_thread);
                  /*
                   * If we've returned from zthr_wait_cycle_done without
                   * clearing the to_condense data structure it's either
                   * because the no-wait synctask has started (which is
                   * indicated by 'syncing' field of to_condense) and we
                   * can expect it to clear to_condense on its own.
                   * Otherwise, we returned before the zthr ran. The
                   * checkfunc will now fail as cancelled == B_TRUE so we
                   * can safely NULL out ds, allowing a different dir's
                   * livelist to be condensed.
                   *
                   * We can be sure that the to_condense struct will not
                   * be repopulated at this stage because both this
                   * function and dsl_livelist_try_condense execute in
                   * syncing context.
                   */
                  if ((spa->spa_to_condense.ds != NULL) &&
                      !spa->spa_to_condense.syncing) {
                          dmu_buf_rele(spa->spa_to_condense.ds->ds_dbuf,
                              spa);
                          spa->spa_to_condense.ds = NULL;
                  }
          }
  
          dsl_dir_livelist_close(dd);
          VERIFY0(zap_lookup(dp->dp_meta_objset, dd->dd_object,
              DD_FIELD_LIVELIST, sizeof (uint64_t), 1, &obj));
          VERIFY0(zap_remove(dp->dp_meta_objset, dd->dd_object,
              DD_FIELD_LIVELIST, tx));
          if (total) {
                  dsl_deadlist_free(dp->dp_meta_objset, obj, tx);
                  spa_feature_decr(spa, SPA_FEATURE_LIVELIST, tx);
          }
  }
  
  static int
  dsl_dir_activity_in_progress(dsl_dir_t *dd, dsl_dataset_t *ds,
      zfs_wait_activity_t activity, boolean_t *in_progress)
  {
          int error = 0;
  
          ASSERT(MUTEX_HELD(&dd->dd_activity_lock));
  
          switch (activity) {
          case ZFS_WAIT_DELETEQ: {
  #ifdef _KERNEL
                  objset_t *os;
                  error = dmu_objset_from_ds(ds, &os);
                  if (error != 0)
                          break;
  
                  mutex_enter(&os->os_user_ptr_lock);
                  void *user = dmu_objset_get_user(os);
                  mutex_exit(&os->os_user_ptr_lock);
                  if (dmu_objset_type(os) != DMU_OST_ZFS ||
                      user == NULL || zfs_get_vfs_flag_unmounted(os)) {
                          *in_progress = B_FALSE;
                          return (0);
                  }
  
                  uint64_t readonly = B_FALSE;
                  error = zfs_get_temporary_prop(ds, ZFS_PROP_READONLY, &readonly,
                      NULL);
  
                  if (error != 0)
                          break;
  
                  if (readonly || !spa_writeable(dd->dd_pool->dp_spa)) {
                          *in_progress = B_FALSE;
                          return (0);
                  }
  
                  uint64_t count, unlinked_obj;
                  error = zap_lookup(os, MASTER_NODE_OBJ, ZFS_UNLINKED_SET, 8, 1,
                      &unlinked_obj);
                  if (error != 0) {
                          dsl_dataset_rele(ds, FTAG);
                          break;
                  }
                  error = zap_count(os, unlinked_obj, &count);
  
                  if (error == 0)
                          *in_progress = (count != 0);
                  break;
  #else
                  /*
                   * The delete queue is ZPL specific, and libzpool doesn't have
                   * it. It doesn't make sense to wait for it.
                   */
                  (void) ds;
                  *in_progress = B_FALSE;
                  break;
  #endif
          }
          default:
                  panic("unrecognized value for activity %d", activity);
          }
  
          return (error);
  }
  
  int
  dsl_dir_wait(dsl_dir_t *dd, dsl_dataset_t *ds, zfs_wait_activity_t activity,
      boolean_t *waited)
  {
          int error = 0;
          boolean_t in_progress;
          dsl_pool_t *dp = dd->dd_pool;
          for (;;) {
                  dsl_pool_config_enter(dp, FTAG);
                  error = dsl_dir_activity_in_progress(dd, ds, activity,
                      &in_progress);
                  dsl_pool_config_exit(dp, FTAG);
                  if (error != 0 || !in_progress)
                          break;
  
                  *waited = B_TRUE;
  
                  if (cv_wait_sig(&dd->dd_activity_cv, &dd->dd_activity_lock) ==
                      0 || dd->dd_activity_cancelled) {
                          error = SET_ERROR(EINTR);
                          break;
                  }
          }
          return (error);
  }
  
  void
  dsl_dir_cancel_waiters(dsl_dir_t *dd)
  {
          mutex_enter(&dd->dd_activity_lock);
          dd->dd_activity_cancelled = B_TRUE;
          cv_broadcast(&dd->dd_activity_cv);
          while (dd->dd_activity_waiters > 0)
                  cv_wait(&dd->dd_activity_cv, &dd->dd_activity_lock);
          mutex_exit(&dd->dd_activity_lock);
  }
  
  #if defined(_KERNEL)
  EXPORT_SYMBOL(dsl_dir_set_quota);
  EXPORT_SYMBOL(dsl_dir_set_reservation);
  #endif
  
  /* CSTYLED */
  ZFS_MODULE_PARAM(zfs, , zvol_enforce_quotas, INT, ZMOD_RW,
          "Enable strict ZVOL quota enforcment");

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