Illumos 3897 - zfs filesystem and snapshot limits

3897 zfs filesystem and snapshot limits
Author: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Christopher Siden <christopher.siden@delphix.com>

References:
  https://www.illumos.org/issues/3897
  https://github.com/illumos/illumos-gate/commit/a2afb61

Porting Notes:

dsl_dataset_snapshot_check(): reduce stack usage using kmem_alloc().

Ported-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

module/zfs/dmu_objset.c

@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 /* Portions Copyright 2010 Robert Milkowski */
@@ -780,9 +781,11 @@ dmu_objset_create_check(void *arg, dmu_tx_t *tx)
 		dsl_dir_rele(pdd, FTAG);
 		return (SET_ERROR(EEXIST));
 	}
+	error = dsl_fs_ss_limit_check(pdd, 1, ZFS_PROP_FILESYSTEM_LIMIT, NULL,
+	    doca->doca_cred);
 	dsl_dir_rele(pdd, FTAG);
 
-	return (0);
+	return (error);
 }
 
 static void
@@ -866,6 +869,12 @@ dmu_objset_clone_check(void *arg, dmu_tx_t *tx)
 		dsl_dir_rele(pdd, FTAG);
 		return (SET_ERROR(EXDEV));
 	}
+	error = dsl_fs_ss_limit_check(pdd, 1, ZFS_PROP_FILESYSTEM_LIMIT, NULL,
+	    doca->doca_cred);
+	if (error != 0) {
+		dsl_dir_rele(pdd, FTAG);
+		return (SET_ERROR(EDQUOT));
+	}
 	dsl_dir_rele(pdd, FTAG);
 
 	error = dsl_dataset_hold(dp, doca->doca_origin, FTAG, &origin);

module/zfs/dmu_send.c

@@ -22,7 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011 by Delphix. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
- * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2014, Joyent, Inc. All rights reserved.
  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
  */
 
@@ -897,6 +897,20 @@ recv_begin_check_existing_impl(dmu_recv_begin_arg_t *drba, dsl_dataset_t *ds,
 	if (error != ENOENT)
 		return (error == 0 ? EEXIST : error);
 
+	/*
+	 * Check snapshot limit before receiving. We'll recheck again at the
+	 * end, but might as well abort before receiving if we're already over
+	 * the limit.
+	 *
+	 * Note that we do not check the file system limit with
+	 * dsl_dir_fscount_check because the temporary %clones don't count
+	 * against that limit.
+	 */
+	error = dsl_fs_ss_limit_check(ds->ds_dir, 1, ZFS_PROP_SNAPSHOT_LIMIT,
+	    NULL, drba->drba_cred);
+	if (error != 0)
+		return (error);
+
 	if (fromguid != 0) {
 		dsl_dataset_t *snap;
 		uint64_t obj = ds->ds_phys->ds_prev_snap_obj;
@@ -1015,6 +1029,25 @@ dmu_recv_begin_check(void *arg, dmu_tx_t *tx)
 		if (error != 0)
 			return (error);
 
+		/*
+		 * Check filesystem and snapshot limits before receiving. We'll
+		 * recheck snapshot limits again at the end (we create the
+		 * filesystems and increment those counts during begin_sync).
+		 */
+		error = dsl_fs_ss_limit_check(ds->ds_dir, 1,
+		    ZFS_PROP_FILESYSTEM_LIMIT, NULL, drba->drba_cred);
+		if (error != 0) {
+			dsl_dataset_rele(ds, FTAG);
+			return (error);
+		}
+
+		error = dsl_fs_ss_limit_check(ds->ds_dir, 1,
+		    ZFS_PROP_SNAPSHOT_LIMIT, NULL, drba->drba_cred);
+		if (error != 0) {
+			dsl_dataset_rele(ds, FTAG);
+			return (error);
+		}
+
 		if (drba->drba_origin != NULL) {
 			dsl_dataset_t *origin;
 			error = dsl_dataset_hold(dp, drba->drba_origin,
@@ -1124,6 +1157,7 @@ dmu_recv_begin(char *tofs, char *tosnap, struct drr_begin *drrb,
 	drc->drc_tosnap = tosnap;
 	drc->drc_tofs = tofs;
 	drc->drc_force = force;
+	drc->drc_cred = CRED();
 
 	if (drrb->drr_magic == BSWAP_64(DMU_BACKUP_MAGIC))
 		drc->drc_byteswap = B_TRUE;
@@ -1919,7 +1953,7 @@ dmu_recv_end_check(void *arg, dmu_tx_t *tx)
 			return (error);
 		}
 		error = dsl_dataset_snapshot_check_impl(origin_head,
-		    drc->drc_tosnap, tx, B_TRUE);
+		    drc->drc_tosnap, tx, B_TRUE, 1, drc->drc_cred);
 		dsl_dataset_rele(origin_head, FTAG);
 		if (error != 0)
 			return (error);
@@ -1927,7 +1961,7 @@ dmu_recv_end_check(void *arg, dmu_tx_t *tx)
 		error = dsl_destroy_head_check_impl(drc->drc_ds, 1);
 	} else {
 		error = dsl_dataset_snapshot_check_impl(drc->drc_ds,
-		    drc->drc_tosnap, tx, B_TRUE);
+		    drc->drc_tosnap, tx, B_TRUE, 1, drc->drc_cred);
 	}
 	return (error);
 }

module/zfs/dsl_dataset.c

@@ -21,7 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
- * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2014, Joyent, Inc. All rights reserved.
  * Copyright (c) 2014 RackTop Systems.
  */
 
@@ -318,7 +318,8 @@ dsl_dataset_snap_lookup(dsl_dataset_t *ds, const char *name, uint64_t *value)
 }
 
 int
-dsl_dataset_snap_remove(dsl_dataset_t *ds, const char *name, dmu_tx_t *tx)
+dsl_dataset_snap_remove(dsl_dataset_t *ds, const char *name, dmu_tx_t *tx,
+    boolean_t adj_cnt)
 {
 	objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
 	uint64_t snapobj = ds->ds_phys->ds_snapnames_zapobj;
@@ -335,6 +336,11 @@ dsl_dataset_snap_remove(dsl_dataset_t *ds, const char *name, dmu_tx_t *tx)
 	err = zap_remove_norm(mos, snapobj, name, mt, tx);
 	if (err == ENOTSUP && mt == MT_FIRST)
 		err = zap_remove(mos, snapobj, name, tx);
+
+	if (err == 0 && adj_cnt)
+		dsl_fs_ss_count_adjust(ds->ds_dir, -1,
+		    DD_FIELD_SNAPSHOT_COUNT, tx);
+
 	return (err);
 }
 
@@ -767,6 +773,21 @@ dsl_dataset_create_sync(dsl_dir_t *pdd, const char *lastname,
 
 	dsl_deleg_set_create_perms(dd, tx, cr);
 
+	/*
+	 * Since we're creating a new node we know it's a leaf, so we can
+	 * initialize the counts if the limit feature is active.
+	 */
+	if (spa_feature_is_active(dp->dp_spa, SPA_FEATURE_FS_SS_LIMIT)) {
+		uint64_t cnt = 0;
+		objset_t *os = dd->dd_pool->dp_meta_objset;
+
+		dsl_dir_zapify(dd, tx);
+		VERIFY0(zap_add(os, dd->dd_object, DD_FIELD_FILESYSTEM_COUNT,
+		    sizeof (cnt), 1, &cnt, tx));
+		VERIFY0(zap_add(os, dd->dd_object, DD_FIELD_SNAPSHOT_COUNT,
+		    sizeof (cnt), 1, &cnt, tx));
+	}
+
 	dsl_dir_rele(dd, FTAG);
 
 	/*
@@ -935,11 +956,12 @@ typedef struct dsl_dataset_snapshot_arg {
 	nvlist_t *ddsa_snaps;
 	nvlist_t *ddsa_props;
 	nvlist_t *ddsa_errors;
+	cred_t *ddsa_cr;
 } dsl_dataset_snapshot_arg_t;
 
 int
 dsl_dataset_snapshot_check_impl(dsl_dataset_t *ds, const char *snapname,
-    dmu_tx_t *tx, boolean_t recv)
+    dmu_tx_t *tx, boolean_t recv, uint64_t cnt, cred_t *cr)
 {
 	int error;
 	uint64_t value;
@@ -977,6 +999,18 @@ dsl_dataset_snapshot_check_impl(dsl_dataset_t *ds, const char *snapname,
 	if (!recv && DS_IS_INCONSISTENT(ds))
 		return (SET_ERROR(EBUSY));
 
+	/*
+	 * Skip the check for temporary snapshots or if we have already checked
+	 * the counts in dsl_dataset_snapshot_check. This means we really only
+	 * check the count here when we're receiving a stream.
+	 */
+	if (cnt != 0 && cr != NULL) {
+		error = dsl_fs_ss_limit_check(ds->ds_dir, cnt,
+		    ZFS_PROP_SNAPSHOT_LIMIT, NULL, cr);
+		if (error != 0)
+			return (error);
+	}
+
 	error = dsl_dataset_snapshot_reserve_space(ds, tx);
 	if (error != 0)
 		return (error);
@@ -992,6 +1026,103 @@ dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx)
 	nvpair_t *pair;
 	int rv = 0;
 
+	/*
+	 * Pre-compute how many total new snapshots will be created for each
+	 * level in the tree and below. This is needed for validating the
+	 * snapshot limit when either taking a recursive snapshot or when
+	 * taking multiple snapshots.
+	 *
+	 * The problem is that the counts are not actually adjusted when
+	 * we are checking, only when we finally sync. For a single snapshot,
+	 * this is easy, the count will increase by 1 at each node up the tree,
+	 * but its more complicated for the recursive/multiple snapshot case.
+	 *
+	 * The dsl_fs_ss_limit_check function does recursively check the count
+	 * at each level up the tree but since it is validating each snapshot
+	 * independently we need to be sure that we are validating the complete
+	 * count for the entire set of snapshots. We do this by rolling up the
+	 * counts for each component of the name into an nvlist and then
+	 * checking each of those cases with the aggregated count.
+	 *
+	 * This approach properly handles not only the recursive snapshot
+	 * case (where we get all of those on the ddsa_snaps list) but also
+	 * the sibling case (e.g. snapshot a/b and a/c so that we will also
+	 * validate the limit on 'a' using a count of 2).
+	 *
+	 * We validate the snapshot names in the third loop and only report
+	 * name errors once.
+	 */
+	if (dmu_tx_is_syncing(tx)) {
+		char *nm;
+		nvlist_t *cnt_track = NULL;
+		cnt_track = fnvlist_alloc();
+
+		nm = kmem_alloc(MAXPATHLEN, KM_SLEEP);
+
+		/* Rollup aggregated counts into the cnt_track list */
+		for (pair = nvlist_next_nvpair(ddsa->ddsa_snaps, NULL);
+		    pair != NULL;
+		    pair = nvlist_next_nvpair(ddsa->ddsa_snaps, pair)) {
+			char *pdelim;
+			uint64_t val;
+
+			(void) strlcpy(nm, nvpair_name(pair), MAXPATHLEN);
+			pdelim = strchr(nm, '@');
+			if (pdelim == NULL)
+				continue;
+			*pdelim = '\0';
+
+			do {
+				if (nvlist_lookup_uint64(cnt_track, nm,
+				    &val) == 0) {
+					/* update existing entry */
+					fnvlist_add_uint64(cnt_track, nm,
+					    val + 1);
+				} else {
+					/* add to list */
+					fnvlist_add_uint64(cnt_track, nm, 1);
+				}
+
+				pdelim = strrchr(nm, '/');
+				if (pdelim != NULL)
+					*pdelim = '\0';
+			} while (pdelim != NULL);
+		}
+
+		kmem_free(nm, MAXPATHLEN);
+
+		/* Check aggregated counts at each level */
+		for (pair = nvlist_next_nvpair(cnt_track, NULL);
+		    pair != NULL; pair = nvlist_next_nvpair(cnt_track, pair)) {
+			int error = 0;
+			char *name;
+			uint64_t cnt = 0;
+			dsl_dataset_t *ds;
+
+			name = nvpair_name(pair);
+			cnt = fnvpair_value_uint64(pair);
+			ASSERT(cnt > 0);
+
+			error = dsl_dataset_hold(dp, name, FTAG, &ds);
+			if (error == 0) {
+				error = dsl_fs_ss_limit_check(ds->ds_dir, cnt,
+				    ZFS_PROP_SNAPSHOT_LIMIT, NULL,
+				    ddsa->ddsa_cr);
+				dsl_dataset_rele(ds, FTAG);
+			}
+
+			if (error != 0) {
+				if (ddsa->ddsa_errors != NULL)
+					fnvlist_add_int32(ddsa->ddsa_errors,
+					    name, error);
+				rv = error;
+				/* only report one error for this check */
+				break;
+			}
+		}
+		nvlist_free(cnt_track);
+	}
+
 	for (pair = nvlist_next_nvpair(ddsa->ddsa_snaps, NULL);
 	    pair != NULL; pair = nvlist_next_nvpair(ddsa->ddsa_snaps, pair)) {
 		int error = 0;
@@ -1012,8 +1143,9 @@ dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx)
 		if (error == 0)
 			error = dsl_dataset_hold(dp, dsname, FTAG, &ds);
 		if (error == 0) {
+			/* passing 0/NULL skips dsl_fs_ss_limit_check */
 			error = dsl_dataset_snapshot_check_impl(ds,
-			    atp + 1, tx, B_FALSE);
+			    atp + 1, tx, B_FALSE, 0, NULL);
 			dsl_dataset_rele(ds, FTAG);
 		}
 
@@ -1025,6 +1157,7 @@ dsl_dataset_snapshot_check(void *arg, dmu_tx_t *tx)
 			rv = error;
 		}
 	}
+
 	return (rv);
 }
 
@@ -1051,6 +1184,7 @@ dsl_dataset_snapshot_sync_impl(dsl_dataset_t *ds, const char *snapname,
 	    bcmp(&os->os_phys->os_zil_header, &zero_zil,
 	    sizeof (zero_zil)) == 0);
 
+	dsl_fs_ss_count_adjust(ds->ds_dir, 1, DD_FIELD_SNAPSHOT_COUNT, tx);
 
 	/*
 	 * The origin's ds_creation_txg has to be < TXG_INITIAL
@@ -1227,6 +1361,7 @@ dsl_dataset_snapshot(nvlist_t *snaps, nvlist_t *props, nvlist_t *errors)
 	ddsa.ddsa_snaps = snaps;
 	ddsa.ddsa_props = props;
 	ddsa.ddsa_errors = errors;
+	ddsa.ddsa_cr = CRED();
 
 	if (error == 0) {
 		error = dsl_sync_task(firstname, dsl_dataset_snapshot_check,
@@ -1275,8 +1410,9 @@ dsl_dataset_snapshot_tmp_check(void *arg, dmu_tx_t *tx)
 	if (error != 0)
 		return (error);
 
+	/* NULL cred means no limit check for tmp snapshot */
 	error = dsl_dataset_snapshot_check_impl(ds, ddsta->ddsta_snapname,
-	    tx, B_FALSE);
+	    tx, B_FALSE, 0, NULL);
 	if (error != 0) {
 		dsl_dataset_rele(ds, FTAG);
 		return (error);
@@ -1644,7 +1780,8 @@ dsl_dataset_rename_snapshot_sync_impl(dsl_pool_t *dp,
 	spa_history_log_internal_ds(ds, "rename", tx,
 	    "-> @%s", ddrsa->ddrsa_newsnapname);
 
-	VERIFY0(dsl_dataset_snap_remove(hds, ddrsa->ddrsa_oldsnapname, tx));
+	VERIFY0(dsl_dataset_snap_remove(hds, ddrsa->ddrsa_oldsnapname, tx,
+	    B_FALSE));
 	mutex_enter(&ds->ds_lock);
 	(void) strcpy(ds->ds_snapname, ddrsa->ddrsa_newsnapname);
 	mutex_exit(&ds->ds_lock);
@@ -1896,6 +2033,7 @@ typedef struct dsl_dataset_promote_arg {
 	dsl_dataset_t *origin_origin; /* origin of the origin */
 	uint64_t used, comp, uncomp, unique, cloneusedsnap, originusedsnap;
 	char *err_ds;
+	cred_t *cr;
 } dsl_dataset_promote_arg_t;
 
 static int snaplist_space(list_t *l, uint64_t mintxg, uint64_t *spacep);
@@ -1913,6 +2051,7 @@ dsl_dataset_promote_check(void *arg, dmu_tx_t *tx)
 	dsl_dataset_t *origin_ds;
 	int err;
 	uint64_t unused;
+	uint64_t ss_mv_cnt;
 
 	err = promote_hold(ddpa, dp, FTAG);
 	if (err != 0)
@@ -1959,6 +2098,7 @@ dsl_dataset_promote_check(void *arg, dmu_tx_t *tx)
 	 * Note however, if we stop before we reach the ORIGIN we get:
 	 * uN + kN + kN-1 + ... + kM - uM-1
 	 */
+	ss_mv_cnt = 0;
 	ddpa->used = origin_ds->ds_phys->ds_referenced_bytes;
 	ddpa->comp = origin_ds->ds_phys->ds_compressed_bytes;
 	ddpa->uncomp = origin_ds->ds_phys->ds_uncompressed_bytes;
@@ -1967,6 +2107,8 @@ dsl_dataset_promote_check(void *arg, dmu_tx_t *tx)
 		uint64_t val, dlused, dlcomp, dluncomp;
 		dsl_dataset_t *ds = snap->ds;
 
+		ss_mv_cnt++;
+
 		/*
 		 * If there are long holds, we won't be able to evict
 		 * the objset.
@@ -2009,9 +2151,9 @@ dsl_dataset_promote_check(void *arg, dmu_tx_t *tx)
 		    ddpa->origin_origin->ds_phys->ds_uncompressed_bytes;
 	}
 
-	/* Check that there is enough space here */
+	/* Check that there is enough space and limit headroom here */
 	err = dsl_dir_transfer_possible(origin_ds->ds_dir, hds->ds_dir,
-	    ddpa->used);
+	    0, ss_mv_cnt, ddpa->used, ddpa->cr);
 	if (err != 0)
 		goto out;
 
@@ -2151,10 +2293,12 @@ dsl_dataset_promote_sync(void *arg, dmu_tx_t *tx)
 		/* move snap name entry */
 		VERIFY0(dsl_dataset_get_snapname(ds));
 		VERIFY0(dsl_dataset_snap_remove(origin_head,
-		    ds->ds_snapname, tx));
+		    ds->ds_snapname, tx, B_TRUE));
 		VERIFY0(zap_add(dp->dp_meta_objset,
 		    hds->ds_phys->ds_snapnames_zapobj, ds->ds_snapname,
 		    8, 1, &ds->ds_object, tx));
+		dsl_fs_ss_count_adjust(hds->ds_dir, 1,
+		    DD_FIELD_SNAPSHOT_COUNT, tx);
 
 		/* change containing dsl_dir */
 		dmu_buf_will_dirty(ds->ds_dbuf, tx);
@@ -2392,6 +2536,7 @@ dsl_dataset_promote(const char *name, char *conflsnap)
 
 	ddpa.ddpa_clonename = name;
 	ddpa.err_ds = conflsnap;
+	ddpa.cr = CRED();
 
 	return (dsl_sync_task(name, dsl_dataset_promote_check,
 	    dsl_dataset_promote_sync, &ddpa, 2 + numsnaps));

module/zfs/dsl_destroy.c

@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2012, 2014 by Delphix. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
+ * Copyright (c) 2013 by Joyent, Inc. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -434,7 +435,7 @@ dsl_destroy_snapshot_sync_impl(dsl_dataset_t *ds, boolean_t defer, dmu_tx_t *tx)
 		ASSERT3U(val, ==, obj);
 	}
 #endif
-	VERIFY0(dsl_dataset_snap_remove(ds_head, ds->ds_snapname, tx));
+	VERIFY0(dsl_dataset_snap_remove(ds_head, ds->ds_snapname, tx, B_TRUE));
 	dsl_dataset_rele(ds_head, FTAG);
 
 	if (ds_prev != NULL)
@@ -662,6 +663,17 @@ dsl_dir_destroy_sync(uint64_t ddobj, dmu_tx_t *tx)
 
 	ASSERT0(dd->dd_phys->dd_head_dataset_obj);
 
+	/*
+	 * 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_fs_ss_count_adjust(dd->dd_parent, -1,
+		    DD_FIELD_FILESYSTEM_COUNT, tx);
+
 	/*
 	 * Remove our reservation. The impl() routine avoids setting the
 	 * actual property, which would require the (already destroyed) ds.

module/zfs/dsl_dir.c

@@ -22,6 +22,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2013 Martin Matuska. All rights reserved.
+ * Copyright (c) 2014 Joyent, Inc. All rights reserved.
  */
 
 #include <sys/dmu.h>
@@ -39,8 +40,87 @@
 #include <sys/zio.h>
 #include <sys/arc.h>
 #include <sys/sunddi.h>
+#include <sys/zfeature.h>
+#include <sys/policy.h>
+#include <sys/zfs_znode.h>
 #include <sys/zvol.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.
+ */
 
 static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd);
 
@@ -384,6 +464,398 @@ error:
 	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_enabled(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, dd->dd_phys->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,
+	    dd->dd_phys->dd_head_dataset_obj, FTAG, &ds));
+
+	for (zap_cursor_init(zc, os, ds->ds_phys->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++;
+	}
+
+	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);
+
+	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
+	if (crgetzoneid(cr) != GLOBAL_ZONEID)
+		return (ENFORCE_ALWAYS);
+
+	if (secpolicy_zfs(cr) == 0)
+		return (ENFORCE_NEVER);
+#endif
+
+	if ((obj = dd->dd_phys->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)
@@ -408,8 +880,12 @@ dsl_dir_create_sync(dsl_pool_t *dp, dsl_dir_t *pds, const char *name,
 	ddphys = dbuf->db_data;
 
 	ddphys->dd_creation_time = gethrestime_sec();
-	if (pds)
+	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,
@@ -458,6 +934,22 @@ dsl_dir_stats(dsl_dir_t *dd, nvlist_t *nv)
 	}
 	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[MAXNAMELEN];
@@ -1166,6 +1658,7 @@ would_change(dsl_dir_t *dd, int64_t delta, dsl_dir_t *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 */
@@ -1230,10 +1723,50 @@ dsl_dir_rename_check(void *arg, dmu_tx_t *tx)
 		}
 	}
 
+	if (dmu_tx_is_syncing(tx)) {
+		if (spa_feature_is_enabled(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(dd->dd_phys->dd_used_bytes, dd->dd_phys->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)
+				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)
+				return (err);
+		}
 
 		/* no rename into our descendant */
 		if (closest_common_ancestor(dd, newparent) == dd) {
@@ -1243,7 +1776,7 @@ dsl_dir_rename_check(void *arg, dmu_tx_t *tx)
 		}
 
 		error = dsl_dir_transfer_possible(dd->dd_parent,
-		    newparent, myspace);
+		    newparent, fs_cnt, ss_cnt, myspace, ddra->ddra_cred);
 		if (error != 0) {
 			dsl_dir_rele(newparent, FTAG);
 			dsl_dir_rele(dd, FTAG);
@@ -1275,6 +1808,37 @@ dsl_dir_rename_sync(void *arg, dmu_tx_t *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_enabled(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,
 		    -dd->dd_phys->dd_used_bytes,
 		    -dd->dd_phys->dd_compressed_bytes,
@@ -1329,17 +1893,20 @@ dsl_dir_rename(const char *oldname, const char *newname)
 
 	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));
 }
 
 int
-dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd, uint64_t space)
+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);
@@ -1347,6 +1914,15 @@ dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd, uint64_t space)
 	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);
 }
 
@@ -1380,6 +1956,15 @@ dsl_dir_zapify(dsl_dir_t *dd, dmu_tx_t *tx)
 	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);
+}
+
 #if defined(_KERNEL) && defined(HAVE_SPL)
 EXPORT_SYMBOL(dsl_dir_set_quota);
 EXPORT_SYMBOL(dsl_dir_set_reservation);

module/zfs/zfeature_common.c

@@ -215,6 +215,17 @@ zpool_feature_init(void)
 	    B_TRUE, B_FALSE, B_FALSE, bookmarks_deps);
 	}
 
+	{
+	static const spa_feature_t filesystem_limits_deps[] = {
+	    SPA_FEATURE_EXTENSIBLE_DATASET,
+	    SPA_FEATURE_NONE
+	};
+	zfeature_register(SPA_FEATURE_FS_SS_LIMIT,
+	    "com.joyent:filesystem_limits", "filesystem_limits",
+	    "Filesystem and snapshot limits.", B_TRUE, B_FALSE, B_FALSE,
+	    filesystem_limits_deps);
+	}
+
 	zfeature_register(SPA_FEATURE_EMBEDDED_DATA,
 	    "com.delphix:embedded_data", "embedded_data",
 	    "Blocks which compress very well use even less space.",

module/zfs/zfs_ioctl.c

@@ -25,8 +25,8 @@
  * Portions Copyright 2012 Pawel Jakub Dawidek <pawel@dawidek.net>
  * Copyright (c) 2012, Joyent, Inc. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
- * Copyright (c) 2012, Joyent, Inc. All rights reserved.
- * Copyright (c) 201i3 by Delphix. All rights reserved.
+ * Copyright (c) 2014, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  * Copyright (c) 2014, Nexenta Systems, Inc. All rights reserved.
@@ -641,12 +641,14 @@ zfs_secpolicy_setprop(const char *dsname, zfs_prop_t prop, nvpair_t *propval,
 		break;
 
 	case ZFS_PROP_QUOTA:
+	case ZFS_PROP_FILESYSTEM_LIMIT:
+	case ZFS_PROP_SNAPSHOT_LIMIT:
 		if (!INGLOBALZONE(curproc)) {
 			uint64_t zoned;
 			char setpoint[MAXNAMELEN];
 			/*
 			 * Unprivileged users are allowed to modify the
-			 * quota on things *under* (ie. contained by)
+			 * limit on things *under* (ie. contained by)
 			 * the thing they own.
 			 */
 			if (dsl_prop_get_integer(dsname, "zoned", &zoned,
@@ -2417,6 +2419,21 @@ zfs_prop_set_special(const char *dsname, zprop_source_t source,
 	case ZFS_PROP_REFQUOTA:
 		err = dsl_dataset_set_refquota(dsname, source, intval);
 		break;
+	case ZFS_PROP_FILESYSTEM_LIMIT:
+	case ZFS_PROP_SNAPSHOT_LIMIT:
+		if (intval == UINT64_MAX) {
+			/* clearing the limit, just do it */
+			err = 0;
+		} else {
+			err = dsl_dir_activate_fs_ss_limit(dsname);
+		}
+		/*
+		 * Set err to -1 to force the zfs_set_prop_nvlist code down the
+		 * default path to set the value in the nvlist.
+		 */
+		if (err == 0)
+			err = -1;
+		break;
 	case ZFS_PROP_RESERVATION:
 		err = dsl_dir_set_reservation(dsname, source, intval);
 		break;