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>

include/sys/dmu_send.h

@@ -23,7 +23,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
- * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 #ifndef _DMU_SEND_H
@@ -56,6 +56,7 @@ typedef struct dmu_recv_cookie {
 	zio_cksum_t drc_cksum;
 	uint64_t drc_newsnapobj;
 	void *drc_owner;
+	cred_t *drc_cred;
 } dmu_recv_cookie_t;
 
 int dmu_recv_begin(char *tofs, char *tosnap, struct drr_begin *drrb,

include/sys/dsl_dataset.h

@@ -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) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  */
 
@@ -266,7 +266,7 @@ int dsl_dataset_clone_swap_check_impl(dsl_dataset_t *clone,
 void dsl_dataset_clone_swap_sync_impl(dsl_dataset_t *clone,
     dsl_dataset_t *origin_head, dmu_tx_t *tx);
 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);
 void dsl_dataset_snapshot_sync_impl(dsl_dataset_t *ds, const char *snapname,
     dmu_tx_t *tx);
 
@@ -276,7 +276,8 @@ void dsl_dataset_recalc_head_uniq(dsl_dataset_t *ds);
 int dsl_dataset_get_snapname(dsl_dataset_t *ds);
 int 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);
+int dsl_dataset_snap_remove(dsl_dataset_t *ds, const char *name, dmu_tx_t *tx,
+    boolean_t adj_cnt);
 void dsl_dataset_set_refreservation_sync_impl(dsl_dataset_t *ds,
     zprop_source_t source, uint64_t value, dmu_tx_t *tx);
 void dsl_dataset_zapify(dsl_dataset_t *ds, dmu_tx_t *tx);

include/sys/dsl_dir.h

@@ -21,6 +21,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
+ * Copyright (c) 2014, Joyent, Inc. All rights reserved.
  */
 
 #ifndef	_SYS_DSL_DIR_H
@@ -38,6 +39,14 @@ extern "C" {
 
 struct dsl_dataset;
 
+/*
+ * DD_FIELD_* are strings that are used in the "extensified" dsl_dir zap object.
+ * They should be of the format <reverse-dns>:<field>.
+ */
+
+#define	DD_FIELD_FILESYSTEM_COUNT	"com.joyent:filesystem_count"
+#define	DD_FIELD_SNAPSHOT_COUNT		"com.joyent:snapshot_count"
+
 typedef enum dd_used {
 	DD_USED_HEAD,
 	DD_USED_SNAP,
@@ -129,8 +138,13 @@ int dsl_dir_set_quota(const char *ddname, zprop_source_t source,
     uint64_t quota);
 int dsl_dir_set_reservation(const char *ddname, zprop_source_t source,
     uint64_t reservation);
+int dsl_dir_activate_fs_ss_limit(const char *);
+int dsl_fs_ss_limit_check(dsl_dir_t *, uint64_t, zfs_prop_t, dsl_dir_t *,
+    cred_t *);
+void dsl_fs_ss_count_adjust(dsl_dir_t *, int64_t, const char *, dmu_tx_t *);
 int dsl_dir_rename(const char *oldname, const char *newname);
-int dsl_dir_transfer_possible(dsl_dir_t *sdd, dsl_dir_t *tdd, uint64_t space);
+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 *);
 boolean_t dsl_dir_is_clone(dsl_dir_t *dd);
 void dsl_dir_new_refreservation(dsl_dir_t *dd, struct dsl_dataset *ds,
     uint64_t reservation, cred_t *cr, dmu_tx_t *tx);
@@ -138,6 +152,8 @@ void dsl_dir_snap_cmtime_update(dsl_dir_t *dd);
 timestruc_t dsl_dir_snap_cmtime(dsl_dir_t *dd);
 void dsl_dir_set_reservation_sync_impl(dsl_dir_t *dd, uint64_t value,
     dmu_tx_t *tx);
+void dsl_dir_zapify(dsl_dir_t *dd, dmu_tx_t *tx);
+boolean_t dsl_dir_is_zapified(dsl_dir_t *dd);
 
 /* internal reserved dir name */
 #define	MOS_DIR_NAME "$MOS"

include/sys/fs/zfs.h

@@ -23,7 +23,7 @@
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
- * Copyright (c) 2012, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  */
 
 /* Portions Copyright 2010 Robert Milkowski */
@@ -142,6 +142,10 @@ typedef enum {
 	ZFS_PROP_LOGICALUSED,
 	ZFS_PROP_LOGICALREFERENCED,
 	ZFS_PROP_INCONSISTENT,		/* not exposed to the user */
+	ZFS_PROP_FILESYSTEM_LIMIT,
+	ZFS_PROP_SNAPSHOT_LIMIT,
+	ZFS_PROP_FILESYSTEM_COUNT,
+	ZFS_PROP_SNAPSHOT_COUNT,
 	ZFS_PROP_SNAPDEV,
 	ZFS_PROP_ACLTYPE,
 	ZFS_PROP_SELINUX_CONTEXT,

include/zfeature_common.h

@@ -48,6 +48,7 @@ typedef enum spa_feature {
 	SPA_FEATURE_EXTENSIBLE_DATASET,
 	SPA_FEATURE_EMBEDDED_DATA,
 	SPA_FEATURE_BOOKMARKS,
+	SPA_FEATURE_FS_SS_LIMIT,
 	SPA_FEATURES
 } spa_feature_t;
 

lib/libspl/include/sys/Makefile.am

@@ -31,6 +31,7 @@ libspl_HEADERS = \
 	$(top_srcdir)/lib/libspl/include/sys/mount.h \
 	$(top_srcdir)/lib/libspl/include/sys/note.h \
 	$(top_srcdir)/lib/libspl/include/sys/param.h \
+	$(top_srcdir)/lib/libspl/include/sys/policy.h \
 	$(top_srcdir)/lib/libspl/include/sys/priv.h \
 	$(top_srcdir)/lib/libspl/include/sys/processor.h \
 	$(top_srcdir)/lib/libspl/include/sys/stack.h \

lib/libspl/include/sys/policy.h

@@ -0,0 +1,26 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License, Version 1.0 only
+ * (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
+ */
+
+#ifndef	_LIBSYS_SYS_POLICY_H
+#define	_LIBSYS_SYS_POLICY_H
+
+#endif	/* _LIBSYS_SYS_POLICY_H */

lib/libzfs/libzfs_dataset.c

@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2013 by Delphix. All rights reserved.
  * Copyright (c) 2012 DEY Storage Systems, Inc.  All rights reserved.
  * Copyright (c) 2012 Pawel Jakub Dawidek <pawel@dawidek.net>.
@@ -1934,6 +1935,10 @@ get_numeric_property(zfs_handle_t *zhp, zfs_prop_t prop, zprop_source_t *src,
 	case ZFS_PROP_REFQUOTA:
 	case ZFS_PROP_RESERVATION:
 	case ZFS_PROP_REFRESERVATION:
+	case ZFS_PROP_FILESYSTEM_LIMIT:
+	case ZFS_PROP_SNAPSHOT_LIMIT:
+	case ZFS_PROP_FILESYSTEM_COUNT:
+	case ZFS_PROP_SNAPSHOT_COUNT:
 		*val = getprop_uint64(zhp, prop, source);
 
 		if (*source == NULL) {
@@ -2342,6 +2347,30 @@ zfs_prop_get(zfs_handle_t *zhp, zfs_prop_t prop, char *propbuf, size_t proplen,
 		}
 		break;
 
+	case ZFS_PROP_FILESYSTEM_LIMIT:
+	case ZFS_PROP_SNAPSHOT_LIMIT:
+	case ZFS_PROP_FILESYSTEM_COUNT:
+	case ZFS_PROP_SNAPSHOT_COUNT:
+
+		if (get_numeric_property(zhp, prop, src, &source, &val) != 0)
+			return (-1);
+
+		/*
+		 * If limit is UINT64_MAX, we translate this into 'none' (unless
+		 * literal is set), and indicate that it's the default value.
+		 * Otherwise, we print the number nicely and indicate that it's
+		 * set locally.
+		 */
+		if (literal) {
+			(void) snprintf(propbuf, proplen, "%llu",
+			    (u_longlong_t)val);
+		} else if (val == UINT64_MAX) {
+			(void) strlcpy(propbuf, "none", proplen);
+		} else {
+			zfs_nicenum(val, propbuf, proplen);
+		}
+		break;
+
 	case ZFS_PROP_REFRATIO:
 	case ZFS_PROP_COMPRESSRATIO:
 		if (get_numeric_property(zhp, prop, src, &source, &val) != 0)

lib/libzfs/libzfs_util.c

@@ -21,6 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright (c) 2012 by Delphix. All rights reserved.
  */
 
@@ -1478,6 +1479,16 @@ zprop_parse_value(libzfs_handle_t *hdl, nvpair_t *elem, int prop,
 			    "use 'none' to disable quota/refquota"));
 			goto error;
 		}
+
+		/*
+		 * Special handling for "*_limit=none". In this case it's not
+		 * 0 but UINT64_MAX.
+		 */
+		if ((type & ZFS_TYPE_DATASET) && isnone &&
+		    (prop == ZFS_PROP_FILESYSTEM_LIMIT ||
+		    prop == ZFS_PROP_SNAPSHOT_LIMIT)) {
+			*ivalp = UINT64_MAX;
+		}
 		break;
 
 	case PROP_TYPE_INDEX:

man/man5/zpool-features.5

@@ -1,6 +1,7 @@
 '\" te
 .\" Copyright (c) 2013 by Delphix. All rights reserved.
 .\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
 .\" 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
@@ -198,6 +199,27 @@ This feature is \fBactive\fR while there are any filesystems, volumes,
 or snapshots which were created after enabling this feature.
 .RE
 
+.sp
+.ne 2
+.na
+\fB\fBfilesystem_limits\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID	com.joyent:filesystem_limits
+READ\-ONLY COMPATIBLE	yes
+DEPENDENCIES	extensible_dataset
+.TE
+
+This feature enables filesystem and snapshot limits. These limits can be used
+to control how many filesystems and/or snapshots can be created at the point in
+the tree on which the limits are set.
+
+This feature is \fBactive\fR once either of the limit properties has been
+set on a dataset. Once activated the feature is never deactivated.
+.RE
+
 .sp
 .ne 2
 .na

man/man8/zfs.8

@@ -23,7 +23,7 @@
 .\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved.
 .\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org>
 .\" Copyright (c) 2014 by Delphix. All rights reserved.
-.\" Copyright (c) 2012, Joyent, Inc. All rights reserved.
+.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
 .\" Copyright 2012 Nexenta Systems, Inc. All Rights Reserved.
 .\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
 .\"
@@ -467,6 +467,18 @@ This property is \fBon\fR if the snapshot has been marked for deferred destructi
 .ne 2
 .mk
 .na
+\fB\fBfilesystem_count\fR
+.ad
+.sp .6
+.RS 4n
+The total number of filesystems and volumes that exist under this location in the
+dataset tree.  This value is only available when a \fBfilesystem_limit\fR has
+been set somewhere in the tree under which the dataset resides.
+.RE
+
+.sp
+.ne 2
+.na
 \fB\fBlogicalreferenced\fR\fR
 .ad
 .sp .6
@@ -549,6 +561,18 @@ property.
 .ne 2
 .mk
 .na
+\fB\fBsnapshot_count\fR
+.ad
+.sp .6
+.RS 4n
+The total number of snapshots that exist under this location in the dataset tree.
+This value is only available when a \fBsnapshot_limit\fR has been set somewhere
+in the tree under which the dataset resides.
+.RE
+
+.sp
+.ne 2
+.na
 \fB\fBtype\fR\fR
 .ad
 .sp .6
@@ -910,6 +934,21 @@ Zones are a Solaris feature and are not relevant on Linux.
 .ne 2
 .mk
 .na
+\fB\fBfilesystem_limit\fR=\fIcount\fR | \fBnone\fR\fR
+.ad
+.sp .6
+.RS 4n
+Limits the number of filesystems and volumes that can exist under this point in
+the dataset tree.  The limit is not enforced if the user is allowed to change
+the limit. Setting a filesystem_limit on a descendent of a filesystem that
+already has a filesystem_limit does not override the ancestor's filesystem_limit,
+but rather imposes an additional limit. This feature must be enabled to be used
+(see \fBzpool-features\fR(5)).
+.RE
+
+.sp
+.ne 2
+.na
 \fB\fBmountpoint\fR=\fIpath\fR | \fBnone\fR | \fBlegacy\fR\fR
 .ad
 .sp .6
@@ -958,6 +997,22 @@ Quotas cannot be set on volumes, as the \fBvolsize\fR property acts as an implic
 .ne 2
 .mk
 .na
+\fB\fBsnapshot_limit\fR=\fIcount\fR | \fBnone\fR\fR
+.ad
+.sp .6
+.RS 4n
+Limits the number of snapshots that can be created on a dataset and its
+descendents. Setting a snapshot_limit on a descendent of a dataset that already
+has a snapshot_limit does not override the ancestor's snapshot_limit, but
+rather imposes an additional limit. The limit is not enforced if the user is
+allowed to change the limit. For example, this means that recursive snapshots
+taken from the global zone are counted against each delegated dataset within
+a zone. This feature must be enabled to be used (see \fBzpool-features\fR(5)).
+.RE
+
+.sp
+.ne 2
+.na
 \fB\fBuserquota@\fR\fIuser\fR=\fIsize\fR | \fBnone\fR\fR
 .ad
 .sp .6
@@ -3013,6 +3068,7 @@ copies           property
 dedup            property
 devices          property       
 exec             property       
+filesystem_limit property
 logbias          property
 mlslabel         property
 mountpoint       property       
@@ -3031,6 +3087,7 @@ shareiscsi       property
 sharenfs         property       
 sharesmb         property       
 snapdir          property       
+snapshot_limit   property
 utf8only         property       
 version          property       
 volblocksize     property       

module/zcommon/zfs_prop.c

@@ -411,6 +411,18 @@ zfs_prop_init(void)
 	zprop_register_number(ZFS_PROP_REFRESERVATION, "refreservation", 0,
 	    PROP_DEFAULT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
 	    "<size> | none", "REFRESERV");
+	zprop_register_number(ZFS_PROP_FILESYSTEM_LIMIT, "filesystem_limit",
+	    UINT64_MAX, PROP_DEFAULT, ZFS_TYPE_FILESYSTEM,
+	    "<count> | none", "FSLIMIT");
+	zprop_register_number(ZFS_PROP_SNAPSHOT_LIMIT, "snapshot_limit",
+	    UINT64_MAX, PROP_DEFAULT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
+	    "<count> | none", "SSLIMIT");
+	zprop_register_number(ZFS_PROP_FILESYSTEM_COUNT, "filesystem_count",
+	    UINT64_MAX, PROP_DEFAULT, ZFS_TYPE_FILESYSTEM,
+	    "<count>", "FSCOUNT");
+	zprop_register_number(ZFS_PROP_SNAPSHOT_COUNT, "snapshot_count",
+	    UINT64_MAX, PROP_DEFAULT, ZFS_TYPE_FILESYSTEM | ZFS_TYPE_VOLUME,
+	    "<count>", "SSCOUNT");
 
 	/* inherit number properties */
 	zprop_register_number(ZFS_PROP_RECORDSIZE, "recordsize",

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) 2014, Joyent, Inc. All rights reserved.
- * Copyright (c) 201i3 by Delphix. 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;