cmd/zfs: clone: accept -u to not mount newly created datasets

Signed-off-by: Ivan Shapovalov <intelfx@intelfx.name>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Closes #18080

Author: intelfx

cmd/zfs/zfs_main.c

@@ -292,7 +292,7 @@ get_usage(zfs_help_t idx)
 {
 	switch (idx) {
 	case HELP_CLONE:
-		return (gettext("\tclone [-p] [-o property=value] ... "
+		return (gettext("\tclone [-pu] [-o property=value] ... "
 		    "<snapshot> <filesystem|volume>\n"));
 	case HELP_CREATE:
 		return (gettext("\tcreate [-Pnpuv] [-o property=value] ... "
@@ -818,29 +818,32 @@ zfs_mount_and_share(libzfs_handle_t *hdl, const char *dataset, zfs_type_t type)
 }
 
 /*
- * zfs clone [-p] [-o prop=value] ... <snap> <fs | vol>
+ * zfs clone [-pu] [-o prop=value] ... <snap> <fs | vol>
  *
  * Given an existing dataset, create a writable copy whose initial contents
  * are the same as the source.  The newly created dataset maintains a
  * dependency on the original; the original cannot be destroyed so long as
  * the clone exists.
  *
  * The '-p' flag creates all the non-existing ancestors of the target first.
+ *
+ * The '-u' flag prevents the newly created file system from being mounted.
  */
 static int
 zfs_do_clone(int argc, char **argv)
 {
 	zfs_handle_t *zhp = NULL;
 	boolean_t parents = B_FALSE;
+	boolean_t nomount = B_FALSE;
 	nvlist_t *props;
-	int ret = 0;
+	int ret = 1;
 	int c;
 
 	if (nvlist_alloc(&props, NV_UNIQUE_NAME, 0) != 0)
 		nomem();
 
 	/* check options */
-	while ((c = getopt(argc, argv, "o:p")) != -1) {
+	while ((c = getopt(argc, argv, "o:pu")) != -1) {
 		switch (c) {
 		case 'o':
 			if (!parseprop(props, optarg)) {
@@ -851,6 +854,9 @@ zfs_do_clone(int argc, char **argv)
 		case 'p':
 			parents = B_TRUE;
 			break;
+		case 'u':
+			nomount = B_TRUE;
+			break;
 		case '?':
 			(void) fprintf(stderr, gettext("invalid option '%c'\n"),
 			    optopt);
@@ -879,8 +885,7 @@ zfs_do_clone(int argc, char **argv)
 
 	/* open the source dataset */
 	if ((zhp = zfs_open(g_zfs, argv[0], ZFS_TYPE_SNAPSHOT)) == NULL) {
-		nvlist_free(props);
-		return (1);
+		goto error_open;
 	}
 
 	if (parents && zfs_name_valid(argv[1], ZFS_TYPE_FILESYSTEM |
@@ -892,37 +897,39 @@ zfs_do_clone(int argc, char **argv)
 		 */
 		if (zfs_dataset_exists(g_zfs, argv[1], ZFS_TYPE_FILESYSTEM |
 		    ZFS_TYPE_VOLUME)) {
-			zfs_close(zhp);
-			nvlist_free(props);
-			return (0);
+			ret = 0;
+			goto error;
 		}
 		if (zfs_create_ancestors(g_zfs, argv[1]) != 0) {
-			zfs_close(zhp);
-			nvlist_free(props);
-			return (1);
+			goto error;
 		}
 	}
 
 	/* pass to libzfs */
 	ret = zfs_clone(zhp, argv[1], props);
 
-	/* create the mountpoint if necessary */
-	if (ret == 0) {
-		if (log_history) {
-			(void) zpool_log_history(g_zfs, history_str);
-			log_history = B_FALSE;
-		}
+	if (ret != 0)
+		goto error;
 
-		/*
-		 * Dataset cloned successfully, mount/share failures are
-		 * non-fatal.
-		 */
-		(void) zfs_mount_and_share(g_zfs, argv[1], ZFS_TYPE_DATASET);
+	/* create the mountpoint if necessary */
+	if (log_history) {
+		(void) zpool_log_history(g_zfs, history_str);
+		log_history = B_FALSE;
 	}
 
+	if (nomount)
+		goto error;
+
+	/*
+	 * Dataset cloned successfully, mount/share failures are
+	 * non-fatal.
+	 */
+	(void) zfs_mount_and_share(g_zfs, argv[1], ZFS_TYPE_DATASET);
+
+error:
 	zfs_close(zhp);
+error_open:
 	nvlist_free(props);
-
 	return (!!ret);
 
 usage:
@@ -4046,7 +4053,7 @@ zfs_do_rename(int argc, char **argv)
 	zfs_handle_t *zhp;
 	renameflags_t flags = { 0 };
 	int c;
-	int ret = 0;
+	int ret = 1;
 	int types;
 	boolean_t parents = B_FALSE;
 
@@ -4118,18 +4125,19 @@ zfs_do_rename(int argc, char **argv)
 		types = ZFS_TYPE_DATASET;
 
 	if ((zhp = zfs_open(g_zfs, argv[0], types)) == NULL)
-		return (1);
+		goto error_open;
 
 	/* If we were asked and the name looks good, try to create ancestors. */
 	if (parents && zfs_name_valid(argv[1], zfs_get_type(zhp)) &&
 	    zfs_create_ancestors(g_zfs, argv[1]) != 0) {
-		zfs_close(zhp);
-		return (1);
+		goto error;
 	}
 
 	ret = (zfs_rename(zhp, argv[1], flags) != 0);
 
+error:
 	zfs_close(zhp);
+error_open:
 	return (ret);
 }
 

man/man8/zfs-clone.8

@@ -40,7 +40,7 @@
 .Sh SYNOPSIS
 .Nm zfs
 .Cm clone
-.Op Fl p
+.Op Fl pu
 .Oo Fl o Ar property Ns = Ns Ar value Oc Ns …
 .Ar snapshot Ar filesystem Ns | Ns Ar volume
 .
@@ -64,6 +64,8 @@ Datasets created in this manner are automatically mounted according to the
 property inherited from their parent.
 If the target filesystem or volume already exists, the operation completes
 successfully.
+.It Fl u
+Do not mount the newly created file system.
 .El
 .
 .Sh EXAMPLES

tests/runfiles/common.run

@@ -196,7 +196,7 @@ tests = ['zfs_clone_001_neg', 'zfs_clone_002_pos', 'zfs_clone_003_pos',
     'zfs_clone_004_pos', 'zfs_clone_005_pos', 'zfs_clone_006_pos',
     'zfs_clone_007_pos', 'zfs_clone_008_neg', 'zfs_clone_009_neg',
     'zfs_clone_010_pos', 'zfs_clone_encrypted', 'zfs_clone_deeply_nested',
-    'zfs_clone_rm_nested']
+    'zfs_clone_rm_nested', 'zfs_clone_nomount']
 tags = ['functional', 'cli_root', 'zfs_clone']
 
 [tests/functional/cli_root/zfs_copies]

tests/zfs-tests/tests/Makefile.am

@@ -677,6 +677,7 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/cli_root/zfs_clone/zfs_clone_010_pos.ksh \
 	functional/cli_root/zfs_clone/zfs_clone_deeply_nested.ksh \
 	functional/cli_root/zfs_clone/zfs_clone_encrypted.ksh \
+	functional/cli_root/zfs_clone/zfs_clone_nomount.ksh \
 	functional/cli_root/zfs_clone/zfs_clone_rm_nested.ksh \
 	functional/cli_root/zfs_copies/cleanup.ksh \
 	functional/cli_root/zfs_copies/setup.ksh \

tests/zfs-tests/tests/functional/cli_root/zfs_clone/zfs_clone_nomount.ksh

@@ -0,0 +1,66 @@
+#!/bin/ksh -p
+# shellcheck disable=SC2066
+# SPDX-License-Identifier: CDDL-1.0
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+
+#
+# Copyright 2025 Ivan Shapovalov <intelfx@intelfx.name>
+#
+
+. "$STF_SUITE/include/libtest.shlib"
+
+#
+# DESCRIPTION:
+# 	`zfs clone -u` should leave the new file system unmounted.
+#
+# STRATEGY:
+#	1. Prepare snapshots
+#	2. Clone a snapshot using `-u` and make sure the clone is not mounted.
+#
+
+verify_runnable "both"
+
+function setup_all
+{
+	log_note "Creating snapshots..."
+
+	for snap in "$SNAPFS" ; do
+		if ! snapexists "$snap" ; then
+			log_must zfs snapshot "$snap"
+		fi
+	done
+
+	return 0
+}
+
+function cleanup_all
+{
+	datasetexists "$fs" && destroy_dataset "$fs"
+
+	for snap in "$SNAPFS" ; do
+		snapexists "$snap" && destroy_dataset "$snap" -Rf
+	done
+
+	return 0
+}
+
+log_onexit cleanup_all
+log_must setup_all
+
+log_assert "zfs clone -u should leave the new file system unmounted"
+
+typeset fs="$TESTPOOL/clonefs$$"
+
+log_must zfs clone -u "$SNAPFS" "$fs"
+log_mustnot ismounted "$fs"
+
+log_pass "zfs clone -u leaves the new file system unmounted"