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OS-1566 filesystem limits for ZFS datasets

*** 19,28 **** --- 19,29 ---- * CDDL HEADER END */ /* * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. * Copyright (c) 2012 by Delphix. All rights reserved. + * Copyright (c) 2012 Joyent, Inc. All rights reserved. */ #include <sys/dmu.h> #include <sys/dmu_objset.h> #include <sys/dmu_tx.h>
*** 36,51 **** --- 37,129 ---- #include <sys/zap.h> #include <sys/zio.h> #include <sys/arc.h> #include <sys/sunddi.h> #include <sys/zfs_zone.h> + #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 count of filesystems and snapshots is stored in the dsl_dir_phys_t which + * impacts the on-disk format. As such, 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 on-disk counts will be uninitialized (0) before the feature is + * active, the counts are updated when a limit is first set on an uninitialized + * node (The filesystem/snapshot counts on a node includes all of the nested + * filesystems/snapshots, plus the node itself. Thus, a new leaf node has a + * filesystem count of 1 and a snapshot count of 0. A filesystem count of 0 on + * a node indicates uninitialized counts on that node.) When setting a limit on + * an uninitialized node, the code starts at the filesystem with the new limit + * and descends into all sub-filesystems and updates the counts to be accurate. + * 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 (0), 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 limit is validated by dsl_dir_fscount_check() and updated by + * dsl_dir_fscount_adjust(). The snapshot limit is validated by + * dsl_snapcount_check() and updated by dsl_snapcount_adjust(). + * A new limit value is validated in dsl_dir_validate_fs_ss_limit() and the + * filesystem counts are adjusted, if necessary, by dsl_dir_set_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. + */ + static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd); static void dsl_dir_set_reservation_sync_impl(dsl_dir_t *dd, uint64_t value, dmu_tx_t *tx); + extern dsl_syncfunc_t dsl_prop_set_sync; + /* ARGSUSED */ static void dsl_dir_evict(dmu_buf_t *db, void *arg) { dsl_dir_t *dd = arg;
*** 405,423 **** --- 483,889 ---- dsl_dir_open(const char *name, void *tag, dsl_dir_t **ddp, const char **tailp) { return (dsl_dir_open_spa(NULL, name, tag, ddp, tailp)); } + /* + * Check if the counts are already valid for this filesystem and its + * descendants. 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 limit set on it, + * then we know that its counts, and the counts on the filesystems below it, + * have been updated to be correct, so we can skip this filesystem. + */ + static int + dsl_dir_set_fs_ss_count(dsl_dir_t *dd, dmu_tx_t *tx, uint64_t *fscnt, + uint64_t *sscnt) + { + uint64_t my_fs_cnt = 0; + uint64_t my_ss_cnt = 0; + uint64_t curr_ss_cnt; + objset_t *os = dd->dd_pool->dp_meta_objset; + zap_cursor_t *zc; + zap_attribute_t *za; + int err; + int ret = 0; + boolean_t limit_set = B_FALSE; + uint64_t fslimit, sslimit; + dsl_dataset_t *ds; + + ASSERT(RW_LOCK_HELD(&dd->dd_pool->dp_config_rwlock)); + + err = dsl_prop_get_dd(dd, zfs_prop_to_name(ZFS_PROP_FILESYSTEM_LIMIT), + 8, 1, &fslimit, NULL, B_FALSE); + if (err == 0 && fslimit != UINT64_MAX) + limit_set = B_TRUE; + + if (!limit_set) { + err = dsl_prop_get_dd(dd, + zfs_prop_to_name(ZFS_PROP_SNAPSHOT_LIMIT), 8, 1, &sslimit, + NULL, B_FALSE); + if (err == 0 && sslimit != UINT64_MAX) + limit_set = B_TRUE; + } + + /* + * If the dd has a limit, we know its count is already good and we + * don't need to recurse down any further. + */ + if (limit_set) { + *fscnt = dd->dd_phys->dd_filesystem_count; + *sscnt = dd->dd_phys->dd_snapshot_count; + return (ret); + } + + zc = kmem_alloc(sizeof (zap_cursor_t), KM_SLEEP); + za = kmem_alloc(sizeof (zap_attribute_t), KM_SLEEP); + + mutex_enter(&dd->dd_lock); + + /* Iterate datasets */ + for (zap_cursor_init(zc, os, dd->dd_phys->dd_child_dir_zapobj); + zap_cursor_retrieve(zc, za) == 0; zap_cursor_advance(zc)) { + dsl_dir_t *chld_dd; + uint64_t chld_fs_cnt = 0; + uint64_t chld_ss_cnt = 0; + + if (dsl_dir_open_obj(dd->dd_pool, + ZFS_DIRENT_OBJ(za->za_first_integer), NULL, FTAG, + &chld_dd)) { + ret = 1; + break; + } + + if (dsl_dir_set_fs_ss_count(chld_dd, tx, &chld_fs_cnt, + &chld_ss_cnt)) { + ret = 1; + break; + } + + dsl_dir_close(chld_dd, FTAG); + + my_fs_cnt += chld_fs_cnt; + my_ss_cnt += chld_ss_cnt; + } + zap_cursor_fini(zc); + kmem_free(zc, sizeof (zap_cursor_t)); + kmem_free(za, sizeof (zap_attribute_t)); + + /* Count snapshots */ + if (dsl_dataset_hold_obj(dd->dd_pool, dd->dd_phys->dd_head_dataset_obj, + FTAG, &ds) == 0) { + if (zap_count(os, ds->ds_phys->ds_snapnames_zapobj, + &curr_ss_cnt) == 0) + my_ss_cnt += curr_ss_cnt; + else + ret = 1; + dsl_dataset_rele(ds, FTAG); + } else { + ret = 1; + } + + /* Add 1 for self */ + my_fs_cnt++; + + /* save updated counts */ + dmu_buf_will_dirty(dd->dd_dbuf, tx); + dd->dd_phys->dd_filesystem_count = my_fs_cnt; + dd->dd_phys->dd_snapshot_count = my_ss_cnt; + + mutex_exit(&dd->dd_lock); + + /* Return child dataset count plus self */ + *fscnt = my_fs_cnt; + *sscnt = my_ss_cnt; + return (ret); + } + + /* ARGSUSED */ + static int + fs_ss_limit_feat_check(void *arg1, void *arg2, dmu_tx_t *tx) + { + return (0); + } + + /* ARGSUSED */ + static void + fs_ss_limit_feat_sync(void *arg1, void *arg2, dmu_tx_t *tx) + { + spa_t *spa = arg1; + zfeature_info_t *limit_feat = + &spa_feature_table[SPA_FEATURE_FS_SS_LIMIT]; + + spa_feature_incr(spa, limit_feat, tx); + } + + /* + * Make sure the feature is enabled and activate it if necessary. + * If setting a limit, ensure the on-disk counts are valid. + * + * We do not validate the new limit, since users who can change the limit are + * also allowed to exceed the limit. + * + * Return -1 to force the zfs_set_prop_nvlist code down the default path to set + * the value in the nvlist. + */ + int + dsl_dir_validate_fs_ss_limit(const char *ddname, uint64_t limit, + zfs_prop_t ptype) + { + dsl_dir_t *dd; + dsl_dataset_t *ds; + int err; + dmu_tx_t *tx; + uint64_t my_fs_cnt = 0; + uint64_t my_ss_cnt = 0; + uint64_t curr_limit; + spa_t *spa; + zfeature_info_t *limit_feat = + &spa_feature_table[SPA_FEATURE_FS_SS_LIMIT]; + + if ((err = dsl_dataset_hold(ddname, FTAG, &ds)) != 0) + return (err); + + spa = dsl_dataset_get_spa(ds); + if (!spa_feature_is_enabled(spa, + &spa_feature_table[SPA_FEATURE_FS_SS_LIMIT])) { + dsl_dataset_rele(ds, FTAG); + return (ENOTSUP); + } + + dd = ds->ds_dir; + + if ((err = dsl_prop_get_dd(dd, zfs_prop_to_name(ptype), 8, 1, + &curr_limit, NULL, B_FALSE)) != 0) { + dsl_dataset_rele(ds, FTAG); + return (err); + } + + if (limit == UINT64_MAX) { + /* + * If we had a limit, since we're now removing that limit, this + * is where we could decrement the feature-active counter so + * that the feature becomes inactive (only enabled) if we + * remove the last limit. However, we do not currently support + * deactivating the feature. + */ + dsl_dataset_rele(ds, FTAG); + return (-1); + } + + if (!spa_feature_is_active(spa, limit_feat)) { + /* + * 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 can't update the MOS in open context, so create a sync + * task. + */ + err = dsl_sync_task_do(dd->dd_pool, fs_ss_limit_feat_check, + fs_ss_limit_feat_sync, spa, (void *)1, 0); + if (err != 0) + return (err); + } + + tx = dmu_tx_create_dd(dd); + if (dmu_tx_assign(tx, TXG_WAIT)) { + dmu_tx_abort(tx); + dsl_dataset_rele(ds, FTAG); + return (ENOSPC); + } + + /* + * Since we are now setting a non-UINT64_MAX 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. + */ + err = -1; + rw_enter(&dd->dd_pool->dp_config_rwlock, RW_READER); + if (dsl_dir_set_fs_ss_count(dd, tx, &my_fs_cnt, &my_ss_cnt)) + err = ENOSPC; + rw_exit(&dd->dd_pool->dp_config_rwlock); + + dmu_tx_commit(tx); + dsl_dataset_rele(ds, FTAG); + + return (err); + } + + /* + * 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 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. + */ + int + dsl_secpolicy_write_prop(dsl_dir_t *dd, zfs_prop_t prop, cred_t *cr) + { + int err = 0; + uint64_t obj; + dsl_dataset_t *ds; + uint64_t zoned; + + #ifdef _KERNEL + if (crgetzoneid(cr) != GLOBAL_ZONEID) + return (EPERM); + + if (secpolicy_zfs(cr) == 0) + return (0); + #endif + + if ((obj = dd->dd_phys->dd_head_dataset_obj) == NULL) + return (ENOENT); + + ASSERT(RW_LOCK_HELD(&dd->dd_pool->dp_config_rwlock)); + + if ((err = dsl_dataset_hold_obj(dd->dd_pool, obj, FTAG, &ds)) != 0) + return (err); + + if (dsl_prop_get_ds(ds, "zoned", 8, 1, &zoned, NULL) || zoned) { + /* Only root can access zoned fs's from the GZ */ + err = EPERM; + } else { + err = dsl_deleg_access_impl(ds, zfs_prop_to_name(prop), cr, + B_FALSE); + } + + dsl_dataset_rele(ds, FTAG); + return (err); + } + + /* + * Check if adding additional child filesystem(s) would exceed any filesystem + * limits. Note that all filesystem limits up to the root (or the highest + * initialized) filesystem or the given ancestor must be satisfied. + */ + int + dsl_dir_fscount_check(dsl_dir_t *dd, uint64_t cnt, dsl_dir_t *ancestor, + cred_t *cr) + { + uint64_t limit; + int err = 0; + + VERIFY(RW_LOCK_HELD(&dd->dd_pool->dp_config_rwlock)); + + /* If we're allowed to change the limit, don't enforce the limit. */ + if (dsl_secpolicy_write_prop(dd, ZFS_PROP_FILESYSTEM_LIMIT, cr) == 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 the counts are not valid on this node and we + * know we won't touch this node's counts. + */ + if (dd->dd_phys->dd_filesystem_count == 0) + return (0); + + err = dsl_prop_get_dd(dd, zfs_prop_to_name(ZFS_PROP_FILESYSTEM_LIMIT), + 8, 1, &limit, NULL, B_FALSE); + if (err != 0) + return (err); + + /* Is there a fs limit which we've hit? */ + if ((dd->dd_phys->dd_filesystem_count + cnt) > limit) + return (EDQUOT); + + if (dd->dd_parent != NULL) + err = dsl_dir_fscount_check(dd->dd_parent, cnt, ancestor, cr); + + return (err); + } + + /* + * Adjust the filesystem count for the specified dsl_dir_t and all parent + * filesystems. When a new filesystem is created, increment the count on all + * parents, and when a filesystem is destroyed, decrement the count. + */ + void + dsl_dir_fscount_adjust(dsl_dir_t *dd, dmu_tx_t *tx, int64_t delta, + boolean_t first) + { + if (first) { + VERIFY(RW_LOCK_HELD(&dd->dd_pool->dp_config_rwlock)); + VERIFY(dmu_tx_is_syncing(tx)); + } + + /* + * 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 '%'. + */ + if (dd->dd_myname[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 (dd->dd_phys->dd_filesystem_count == 0) + return; + + /* + * On initial entry we need to check if this feature is active, but + * we don't want to re-check this on each recursive call. Note: the + * feature cannot be active if its not enabled. If the feature is not + * active, don't touch the on-disk count fields. + */ + if (first) { + zfeature_info_t *quota_feat = + &spa_feature_table[SPA_FEATURE_FS_SS_LIMIT]; + + if (!spa_feature_is_active(dd->dd_pool->dp_spa, quota_feat)) + return; + } + + dmu_buf_will_dirty(dd->dd_dbuf, tx); + + mutex_enter(&dd->dd_lock); + + dd->dd_phys->dd_filesystem_count += delta; + VERIFY(dd->dd_phys->dd_filesystem_count >= 1); /* ourself is 1 */ + + /* Roll up this additional count into our ancestors */ + if (dd->dd_parent != NULL) + dsl_dir_fscount_adjust(dd->dd_parent, tx, delta, B_FALSE); + + mutex_exit(&dd->dd_lock); + } + 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; + zfeature_info_t *limit_feat = + &spa_feature_table[SPA_FEATURE_FS_SS_LIMIT]; + ddobj = dmu_object_alloc(mos, DMU_OT_DSL_DIR, 0, DMU_OT_DSL_DIR, sizeof (dsl_dir_phys_t), tx); if (pds) { VERIFY(0 == zap_add(mos, pds->dd_phys->dd_child_dir_zapobj, name, sizeof (uint64_t), 1, &ddobj, tx));
*** 429,438 **** --- 895,907 ---- 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(); + /* Only initialize the count if the limit feature is active */ + if (spa_feature_is_active(dp->dp_spa, limit_feat)) + ddphys->dd_filesystem_count = 1; if (pds) ddphys->dd_parent_obj = pds->dd_object; ddphys->dd_props_zapobj = zap_create(mos, DMU_OT_DSL_PROPS, DMU_OT_NONE, 0, tx); ddphys->dd_child_dir_zapobj = zap_create(mos,
*** 486,495 **** --- 955,974 ---- ASSERT(RW_WRITE_HELD(&dd->dd_pool->dp_config_rwlock)); ASSERT(dd->dd_phys->dd_head_dataset_obj == 0); /* + * Decrement the filesystem count for all parent filesystems. + * + * When we receive an incremental stream into a filesystem that already + * exists, a temporary clone is created. We never count this temporary + * clone, whose name begins with a '%'. + */ + if (dd->dd_myname[0] != '%' && dd->dd_parent != NULL) + dsl_dir_fscount_adjust(dd->dd_parent, tx, -1, B_TRUE); + + /* * Remove our reservation. The impl() routine avoids setting the * actual property, which would require the (already destroyed) ds. */ dsl_dir_set_reservation_sync_impl(dd, 0, tx);
*** 1034,1045 **** } mutex_exit(&dd->dd_lock); return (err); } - extern dsl_syncfunc_t dsl_prop_set_sync; - static void dsl_dir_set_quota_sync(void *arg1, void *arg2, dmu_tx_t *tx) { dsl_dataset_t *ds = arg1; dsl_dir_t *dd = ds->ds_dir; --- 1513,1522 ----
*** 1236,1245 **** --- 1713,1723 ---- } struct renamearg { dsl_dir_t *newparent; const char *mynewname; + cred_t *cr; }; static int dsl_dir_rename_check(void *arg1, void *arg2, dmu_tx_t *tx) {
*** 1276,1288 **** /* no rename into our descendant */ if (closest_common_ancestor(dd, ra->newparent) == dd) return (EINVAL); if (err = dsl_dir_transfer_possible(dd->dd_parent, ! ra->newparent, myspace)) return (err); } return (0); } static void --- 1754,1780 ---- /* no rename into our descendant */ if (closest_common_ancestor(dd, ra->newparent) == dd) return (EINVAL); if (err = dsl_dir_transfer_possible(dd->dd_parent, ! ra->newparent, dd, myspace, ra->cr)) return (err); + + if (dd->dd_phys->dd_filesystem_count == 0 && + dmu_tx_is_syncing(tx)) { + uint64_t fs_cnt = 0; + uint64_t ss_cnt = 0; + + /* + * Ensure this portion of the tree's counts have been + * initialized in case the new parent has limits set. + */ + err = dsl_dir_set_fs_ss_count(dd, tx, &fs_cnt, &ss_cnt); + if (err) + return (EIO); } + } return (0); } static void
*** 1301,1310 **** --- 1793,1816 ---- dsl_dir_name(ra->newparent, namebuf); spa_history_log_internal_dd(dd, "rename", tx, "-> %s/%s", namebuf, ra->mynewname); if (ra->newparent != dd->dd_parent) { + int cnt; + + mutex_enter(&dd->dd_lock); + + cnt = dd->dd_phys->dd_filesystem_count; + dsl_dir_fscount_adjust(dd->dd_parent, tx, -cnt, B_TRUE); + dsl_dir_fscount_adjust(ra->newparent, tx, cnt, B_TRUE); + + cnt = dd->dd_phys->dd_snapshot_count; + dsl_snapcount_adjust(dd->dd_parent, tx, -cnt, B_TRUE); + dsl_snapcount_adjust(ra->newparent, tx, cnt, B_TRUE); + + mutex_exit(&dd->dd_lock); + dsl_dir_diduse_space(dd->dd_parent, DD_USED_CHILD, -dd->dd_phys->dd_used_bytes, -dd->dd_phys->dd_compressed_bytes, -dd->dd_phys->dd_uncompressed_bytes, tx); dsl_dir_diduse_space(ra->newparent, DD_USED_CHILD,
*** 1364,1394 **** if (ra.mynewname == NULL) { err = EEXIST; goto out; } err = dsl_sync_task_do(dd->dd_pool, dsl_dir_rename_check, dsl_dir_rename_sync, dd, &ra, 3); out: dsl_dir_close(ra.newparent, FTAG); return (err); } int ! dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd, uint64_t space) { dsl_dir_t *ancestor; int64_t adelta; uint64_t avail; ancestor = closest_common_ancestor(sdd, tdd); adelta = would_change(sdd, -space, ancestor); avail = dsl_dir_space_available(tdd, ancestor, adelta, FALSE); if (avail < space) return (ENOSPC); return (0); } timestruc_t dsl_dir_snap_cmtime(dsl_dir_t *dd) --- 1870,1915 ---- if (ra.mynewname == NULL) { err = EEXIST; goto out; } + ra.cr = CRED(); + err = dsl_sync_task_do(dd->dd_pool, dsl_dir_rename_check, dsl_dir_rename_sync, dd, &ra, 3); out: dsl_dir_close(ra.newparent, FTAG); return (err); } int ! dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd, dsl_dir_t *moving_dd, ! 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 (ENOSPC); + if (sdd != moving_dd) { + err = dsl_dir_fscount_check(tdd, + moving_dd->dd_phys->dd_filesystem_count, ancestor, cr); + if (err != 0) + return (err); + } + err = dsl_snapcount_check(tdd, moving_dd->dd_phys->dd_snapshot_count, + ancestor, cr); + if (err != 0) + return (err); + return (0); } timestruc_t dsl_dir_snap_cmtime(dsl_dir_t *dd)