ZTS/zfs_mount: test that ro/rw mount methods remain consistent

Whether a mount ends up as read-only or read-write depends on a
combination of platform, readonly= filesystem property, mount method
(system mount(8) or zfs-mount(8)) and mount option provided (ro, rw or
none).

This tests all combinations, and ensures they match what has
traditionally been expected on this platform, so we'll know if we
accidentally changed it.

Sponsored-by: TrueNAS
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <rob.norris@truenas.com>
Closes #18557
Closes #18563

tests/runfiles/common.run

@@ -271,8 +271,8 @@ tests = ['zfs_mount_001_pos', 'zfs_mount_002_pos', 'zfs_mount_003_pos',
     'zfs_mount_004_pos', 'zfs_mount_005_pos', 'zfs_mount_007_pos',
     'zfs_mount_009_neg', 'zfs_mount_010_neg', 'zfs_mount_011_neg',
     'zfs_mount_012_pos', 'zfs_mount_all_001_pos', 'zfs_mount_encrypted',
-    'zfs_mount_remount', 'zfs_mount_all_fail', 'zfs_mount_all_mountpoints',
-    'zfs_mount_test_race', 'zfs_mount_recursive']
+    'zfs_mount_remount', 'zfs_mount_ro_rw', 'zfs_mount_all_fail',
+    'zfs_mount_all_mountpoints', 'zfs_mount_test_race', 'zfs_mount_recursive']
 tags = ['functional', 'cli_root', 'zfs_mount']
 
 [tests/functional/cli_root/zfs_program]

tests/runfiles/sanity.run

@@ -156,7 +156,7 @@ tests = ['zfs_mount_001_pos', 'zfs_mount_002_pos', 'zfs_mount_003_pos',
     'zfs_mount_004_pos', 'zfs_mount_005_pos', 'zfs_mount_007_pos',
     'zfs_mount_009_neg', 'zfs_mount_010_neg', 'zfs_mount_011_neg',
     'zfs_mount_012_pos', 'zfs_mount_encrypted', 'zfs_mount_remount',
-    'zfs_mount_all_fail', 'zfs_mount_all_mountpoints',
+    'zfs_mount_ro_rw', 'zfs_mount_all_fail', 'zfs_mount_all_mountpoints',
     'zfs_mount_test_race', 'zfs_mount_recursive']
 tags = ['functional', 'cli_root', 'zfs_mount']
 

tests/zfs-tests/tests/Makefile.am

@@ -814,6 +814,7 @@ nobase_dist_datadir_zfs_tests_tests_SCRIPTS += \
 	functional/cli_root/zfs_mount/zfs_mount_encrypted.ksh \
 	functional/cli_root/zfs_mount/zfs_mount_recursive.ksh \
 	functional/cli_root/zfs_mount/zfs_mount_remount.ksh \
+	functional/cli_root/zfs_mount/zfs_mount_ro_rw.ksh \
 	functional/cli_root/zfs_mount/zfs_mount_test_race.ksh \
 	functional/cli_root/zfs_mount/zfs_multi_mount.ksh \
 	functional/cli_root/zfs_program/cleanup.ksh \

tests/zfs-tests/tests/functional/cli_root/zfs_mount/zfs_mount_ro_rw.ksh

@@ -0,0 +1,130 @@
+#!/bin/ksh -p
+# SPDX-License-Identifier: CDDL-1.0
+#
+# CDDL HEADER START
+#
+# The contents of this file are subject to the terms of the
+# Common Development and Distribution License (the "License").
+# You may not use this file except in compliance with the License.
+#
+# You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+# or https://opensource.org/licenses/CDDL-1.0.
+# See the License for the specific language governing permissions
+# and limitations under the License.
+#
+# When distributing Covered Code, include this CDDL HEADER in each
+# file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+# If applicable, add the following below this CDDL HEADER, with the
+# fields enclosed by brackets "[]" replaced with your own identifying
+# information: Portions Copyright [yyyy] [name of copyright owner]
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright (c) 2026, TrueNAS.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/cli_root/zfs_mount/zfs_mount.kshlib
+
+#
+# we set up and mount multiple times, with these combinations:
+# - readonly property: on, off
+# - mount method: mount(8) (mountpoint=legacy), zfs-mount(8) (mountpoint=path)
+# - mount option: [none], ro, rw
+#
+# after each mount, we check whether we ended up mounting read-only or
+# read-write, and note the result. once we've done them all, we compare the
+# result set to the "correct" set for this platform (by observation). the
+# test passes if they match, fail if they don't
+#
+#        readonly     |         on          |         off         |
+#        mount method |  legacy  |   path   |  legacy  |   path   |
+#        mount option | -- ro rw | -- ro rw | -- ro rw | -- ro rw |
+typeset -a rs_linux=(   rw ro rw   ro ro rw   rw ro rw   rw ro rw )
+typeset -a rs_freebsd=( ro ro ro   ro ro rw   rw ro rw   rw ro rw )
+
+if is_linux ; then
+    typeset -n rs_wanted=rs_linux
+elif is_freebsd ; then
+    typeset -n rs_wanted=rs_freebsd
+else
+    log_unsupported "no result set defined for this platform"
+fi
+
+verify_runnable "both"
+
+testfs=$TESTPOOL/$TESTFS
+testmnt=$TESTDIR/mountpoint
+
+function cleanup
+{
+	log_must zfs inherit -S canmount $testfs
+	log_must zfs inherit readonly $testfs
+	log_must zfs inherit mountpoint $testfs
+	log_must rm -rf $testmnt
+}
+
+log_assert "Verify combinations of readonly/readwrite produce correct mount."
+
+log_onexit cleanup
+
+
+# setup
+log_must datasetexists $testfs
+log_must zfs set canmount=noauto $testfs
+umount $testfs
+
+
+typeset -a rs=()
+
+for readonly in on off ; do
+	for method in legacy path ; do
+		for option in default ro rw ; do
+
+			log_must zfs set readonly=$readonly $testfs
+
+			if [[ $method == 'legacy' ]] ; then
+				log_must zfs set mountpoint=legacy $testfs
+			else
+				log_must zfs set mountpoint=$testmnt $testfs
+			fi
+
+			# recreate the mountpoint. even if it wasn't mounted,
+			# changing the mountpoint property can remove it
+			log_must mkdir -p $testmnt
+
+			# issue the mount with the wanted method and option
+			case $method in
+			legacy)
+				case $option in
+				default) log_must mount_default $testfs $testmnt ;;
+				ro)      log_must mount_ro $testfs $testmnt ;;
+				rw)      log_must mount_rw $testfs $testmnt ;;
+				esac
+			;;
+			path)
+				case $option in
+				default)  log_must zfs mount $testfs ;;
+				ro)       log_must zfs mount -o ro $testfs ;;
+				rw)       log_must zfs mount -o rw $testfs ;;
+				esac
+			;;
+			esac
+
+			result=$(mount_get_ro_rw $testmnt)
+			rs+=($result)
+			log_note "result: $result"
+
+			log_must umount $testfs
+		done
+	done
+done
+
+log_note "results: ${rs[@]}"
+log_note "wanted:  ${rs_wanted[@]}"
+
+log_must test "${rs[*]}" == "${rs_wanted[*]}"
+
+log_pass "All mounts correct for this platform."