MFC r305209: MFV r302660: 6314 buffer overflow in dsl_dataset_name

[FreeBSD/stable/10.git] / sys / cddl / contrib / opensolaris / uts / common / fs / 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 http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2011 Pawel Jakub Dawidek <pawel@dawidek.net>.
 * All rights reserved.
 * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
 * Copyright (c) 2014 Joyent, Inc. All rights reserved.
 * Copyright (c) 2014 Spectra Logic Corporation, All rights reserved.
 * Copyright 2015 Nexenta Systems, Inc. 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/metaslab.h>
#include <sys/zap.h>
#include <sys/zio.h>
#include <sys/arc.h>
#include <sys/sunddi.h>
#include <sys/zvol.h>
#ifdef _KERNEL
#include <sys/zfs_vfsops.h>
#endif
#include <sys/zfeature.h>
#include <sys/policy.h>
#include <sys/zfs_znode.h>
#include "zfs_namecheck.h"
#include "zfs_prop.h"

/*
 * 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 initizized 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().
 *
 * There is a special case when we receive a filesystem that already exists. In
 * this case a temporary clone name of %X is created (see dmu_recv_begin). We
 * never update the filesystem counts for temporary clones.
 *
 * Likewise, we do not update the snapshot counts for temporary snapshots,
 * such as those created by zfs diff.
 */

extern inline dsl_dir_phys_t *dsl_dir_phys(dsl_dir_t *dd);

static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd);

static void
dsl_dir_evict(void *dbu)
{
        dsl_dir_t *dd = dbu;
        dsl_pool_t *dp = dd->dd_pool;
        int t;

        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);

        dsl_prop_fini(dd);
        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, void *tag, dsl_dir_t **ddp)
{
        dmu_buf_t *dbuf;
        dsl_dir_t *dd;
        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);
#ifdef ZFS_DEBUG
        {
                dmu_object_info_t doi;
                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));
        }
#endif
        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);
                dsl_prop_init(dd);

                dsl_dir_snap_cmtime_update(dd);

                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) strcpy(dd->dd_myname, tail);
                        } 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) strcpy(dd->dd_myname, spa_name(dp->dp_spa));
                }

                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);
                }

                dmu_buf_init_user(&dd->dd_dbu, dsl_dir_evict, &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);
                        dsl_prop_fini(dd);
                        mutex_destroy(&dd->dd_lock);
                        kmem_free(dd, sizeof (dsl_dir_t));
                        dd = winner;
                } else {
                        spa_open_ref(dp->dp_spa, dd);
                }
        }

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

errout:
        if (dd->dd_parent)
                dsl_dir_rele(dd->dd_parent, dd);
        dsl_prop_fini(dd);
        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, 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, 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) strcpy(component, path);
                p = NULL;
        } else if (p[0] == '/') {
                if (p - path >= ZFS_MAX_DATASET_NAME_LEN)
                        return (SET_ERROR(ENAMETOOLONG));
                (void) strncpy(component, path, p - path);
                component[p - path] = '\0';
                p++;
        } else if (p[0] == '@') {
                /*
                 * if the next separator is an @, there better not be
                 * any more slashes.
                 */
                if (strchr(path, '/'))
                        return (SET_ERROR(EINVAL));
                if (p - path >= ZFS_MAX_DATASET_NAME_LEN)
                        return (SET_ERROR(ENAMETOOLONG));
                (void) strncpy(component, path, p - path);
                component[p - path] = '\0';
        } 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, void *tag,
    dsl_dir_t **ddp, const char **tailp)
{
        char buf[ZFS_MAX_DATASET_NAME_LEN];
        const char *spaname, *next, *nextnext = NULL;
        int err;
        dsl_dir_t *dd;
        uint64_t ddobj;

        err = getcomponent(name, buf, &next);
        if (err != 0)
                return (err);

        /* Make sure the name is in the specified pool. */
        spaname = spa_name(dp->dp_spa);
        if (strcmp(buf, spaname) != 0)
                return (SET_ERROR(EXDEV));

        ASSERT(dsl_pool_config_held(dp));

        err = dsl_dir_hold_obj(dp, dp->dp_root_dir_obj, NULL, tag, &dd);
        if (err != 0) {
                return (err);
        }

        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, 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);
                return (err);
        }

        /*
         * It's an error if there's more than one component left, or
         * tailp==NULL and there's any component left.
         */
        if (next != NULL &&
            (tailp == NULL || (nextnext && nextnext[0] != '\0'))) {
                /* bad path name */
                dsl_dir_rele(dd, tag);
                dprintf("next=%p (%s) tail=%p\n", next, next?next:"", tailp);
                err = SET_ERROR(ENOENT);
        }
        if (tailp != NULL)
                *tailp = next;
        *ddp = dd;
        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 & $ORIGIN) objsets and
                 * temporary datasets.
                 */
                if (chld_dd->dd_myname[0] == '$' ||
                    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)
{
        enforce_res_t enforce = ENFORCE_ALWAYS;
        uint64_t obj;
        dsl_dataset_t *ds;
        uint64_t zoned;

        ASSERT(prop == ZFS_PROP_FILESYSTEM_LIMIT ||
            prop == ZFS_PROP_SNAPSHOT_LIMIT);

#ifdef _KERNEL
#ifdef __FreeBSD__
        if (jailed(cr))
#else
        if (crgetzoneid(cr) != GLOBAL_ZONEID)
#endif
                return (ENFORCE_ALWAYS);

        if (secpolicy_zfs(cr) == 0)
                return (ENFORCE_NEVER);
#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);

        if (dsl_prop_get_ds(ds, "zoned", 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)
{
        objset_t *os = dd->dd_pool->dp_meta_objset;
        uint64_t limit, count;
        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 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);
        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 (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 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) || zap_lookup(os, dd->dd_object,
            count_prop, sizeof (count), 1, &count) == ENOENT)
                return (0);

        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);

        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);

        /*
         * When we receive an incremental stream into a filesystem that already
         * exists, a temporary clone is created.  We don't count this temporary
         * clone, whose name begins with a '%'. We also ignore hidden ($FREE,
         * $MOS & $ORIGIN) objsets.
         */
        if ((dd->dd_myname[0] == '%' || dd->dd_myname[0] == '$') &&
            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) {
                VERIFY(0 == zap_add(mos, dsl_dir_phys(pds)->dd_child_dir_zapobj,
                    name, sizeof (uint64_t), 1, &ddobj, tx));
        } else {
                /* it's the root dir */
                VERIFY(0 == zap_add(mos, DMU_POOL_DIRECTORY_OBJECT,
                    DMU_POOL_ROOT_DATASET, sizeof (uint64_t), 1, &ddobj, tx));
        }
        VERIFY(0 == dmu_bonus_hold(mos, ddobj, FTAG, &dbuf));
        dmu_buf_will_dirty(dbuf, tx);
        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));
}

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

        if (dsl_dir_is_zapified(dd)) {
                uint64_t count;
                objset_t *os = dd->dd_pool->dp_meta_objset;

                if (zap_lookup(os, dd->dd_object, DD_FIELD_FILESYSTEM_COUNT,
                    sizeof (count), 1, &count) == 0) {
                        dsl_prop_nvlist_add_uint64(nv,
                            ZFS_PROP_FILESYSTEM_COUNT, count);
                }
                if (zap_lookup(os, dd->dd_object, DD_FIELD_SNAPSHOT_COUNT,
                    sizeof (count), 1, &count) == 0) {
                        dsl_prop_nvlist_add_uint64(nv,
                            ZFS_PROP_SNAPSHOT_COUNT, count);
                }
        }

        if (dsl_dir_is_clone(dd)) {
                dsl_dataset_t *ds;
                char buf[ZFS_MAX_DATASET_NAME_LEN];

                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);
                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", tx->tx_txg,
            dd->dd_space_towrite[tx->tx_txg&TXG_MASK] / 1024);
        dd->dd_space_towrite[tx->tx_txg&TXG_MASK] = 0;
        mutex_exit(&dd->dd_lock);

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

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

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

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

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

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

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

        mutex_enter(&dd->dd_lock);
        if (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, FALSE);
                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, boolean_t checkrefquota, list_t *tr_list,
    dmu_tx_t *tx, boolean_t first)
{
        uint64_t txg = tx->tx_txg;
        uint64_t est_inflight, used_on_disk, quota, parent_rsrv;
        uint64_t deferred = 0;
        struct tempreserve *tr;
        int retval = EDQUOT;
        int txgidx = txg & TXG_MASK;
        int i;
        uint64_t ref_rsrv = 0;

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

        mutex_enter(&dd->dd_lock);

        /*
         * Check against the dsl_dir's quota.  We don't add in the delta
         * when checking for over-quota because they get one free hit.
         */
        est_inflight = dsl_dir_space_towrite(dd);
        for (i = 0; i < TXG_SIZE; i++)
                est_inflight += dd->dd_tempreserved[i];
        used_on_disk = 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, checkrefquota,
                    asize, est_inflight, &used_on_disk, &ref_rsrv);
                if (error) {
                        mutex_exit(&dd->dd_lock);
                        return (error);
                }
        }

        /*
         * If this transaction will result in a net free of space,
         * we want to let it through.
         */
        if (ignorequota || netfree || dsl_dir_phys(dd)->dd_quota == 0)
                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) {
                spa_t *spa = dd->dd_pool->dp_spa;
                uint64_t poolsize = dsl_pool_adjustedsize(dd->dd_pool, netfree);
                deferred = metaslab_class_get_deferred(spa_normal_class(spa));
                if (poolsize - deferred < quota) {
                        quota = poolsize - deferred;
                        retval = ENOSPC;
                }
        }

        /*
         * If they are requesting more space, and our current estimate
         * is over quota, they get to try again unless the actual
         * on-disk is over quota and there are no pending changes (which
         * may free up space for us).
         */
        if (used_on_disk + est_inflight >= quota) {
                if (est_inflight > 0 || used_on_disk < quota ||
                    (retval == ENOSPC && used_on_disk < quota + deferred))
                        retval = ERESTART;
                dprintf_dd(dd, "failing: used=%lluK inflight = %lluK "
                    "quota=%lluK tr=%lluK err=%d\n",
                    used_on_disk>>10, est_inflight>>10,
                    quota>>10, asize>>10, retval);
                mutex_exit(&dd->dd_lock);
                return (SET_ERROR(retval));
        }

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

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

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

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

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

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

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

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

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

                tr = kmem_zalloc(sizeof (struct tempreserve), KM_SLEEP);
                tr->tr_size = lsize;
                list_insert_tail(tr_list, tr);
        } 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, fsize >= asize,
                    FALSE, asize > usize, tr_list, tx, 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.
 */
void
dsl_dir_willuse_space(dsl_dir_t *dd, int64_t space, dmu_tx_t *tx)
{
        int64_t parent_space;
        uint64_t est_used;

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

        est_used = dsl_dir_space_towrite(dd) + 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);

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

/* call from syncing context when we actually write/free space for this dd */
void
dsl_dir_diduse_space(dsl_dir_t *dd, dd_used_t type,
    int64_t used, int64_t compressed, int64_t uncompressed, dmu_tx_t *tx)
{
        int64_t accounted_delta;

        /*
         * 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);

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

        dmu_buf_will_dirty(dd->dd_dbuf, tx);

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

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

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

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(tx == NULL || dmu_tx_is_syncing(tx));
        ASSERT(oldtype < DD_USED_NUM);
        ASSERT(newtype < DD_USED_NUM);

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

        if (tx != NULL)
                dmu_buf_will_dirty(dd->dd_dbuf, tx);
        mutex_enter(&dd->dd_lock);
        ASSERT(delta > 0 ?
            dsl_dir_phys(dd)->dd_used_breakdown[oldtype] >= delta :
            dsl_dir_phys(dd)->dd_used_breakdown[newtype] >= -delta);
        ASSERT(dsl_dir_phys(dd)->dd_used_bytes >= ABS(delta));
        dsl_dir_phys(dd)->dd_used_breakdown[oldtype] -= delta;
        dsl_dir_phys(dd)->dd_used_breakdown[newtype] += delta;
        mutex_exit(&dd->dd_lock);
}

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_NONE));
}

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, B_FALSE) - 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_NONE));
}

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;
} dsl_dir_rename_arg_t;

/* ARGSUSED */
static int
dsl_valid_rename(dsl_pool_t *dp, dsl_dataset_t *ds, void *arg)
{
        int *deltap = arg;
        char namebuf[ZFS_MAX_DATASET_NAME_LEN];

        dsl_dataset_name(ds, namebuf);

        if (strlen(namebuf) + *deltap >= ZFS_MAX_DATASET_NAME_LEN)
                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;
        const char *mynewname;
        int error;
        int delta = strlen(ddra->ddra_newname) - strlen(ddra->ddra_oldname);

        /* 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));
        }

        /* if the name length is growing, validate child name lengths */
        if (delta > 0) {
                error = dmu_objset_find_dp(dp, dd->dd_object, dsl_valid_rename,
                    &delta, 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);
                        }
                }

                /* 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);
                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;
        int error;
        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 */
        error = zap_remove(mos,
            dsl_dir_phys(dd->dd_parent)->dd_child_dir_zapobj,
            dd->dd_myname, tx);
        ASSERT0(error);

        (void) strcpy(dd->dd_myname, mynewname);
        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));

#ifdef __FreeBSD__
#ifdef _KERNEL
        zfsvfs_update_fromname(ddra->ddra_oldname, ddra->ddra_newname);
        zvol_rename_minors(ddra->ddra_oldname, ddra->ddra_newname);
#endif
#endif

        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();

        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)
{
        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);
        if (err != 0)
                return (err);
        err = dsl_fs_ss_limit_check(tdd, ss_cnt, ZFS_PROP_SNAPSHOT_LIMIT,
            ancestor, cr);
        if (err != 0)
                return (err);

        return (0);
}

timestruc_t
dsl_dir_snap_cmtime(dsl_dir_t *dd)
{
        timestruc_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)
{
        timestruc_t t;

        gethrestime(&t);
        mutex_enter(&dd->dd_lock);
        dd->dd_snap_cmtime = t;
        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);
}