diff --git a/tools/test/stress2/misc/gnop12.sh b/tools/test/stress2/misc/gnop12.sh
new file mode 100755
index 000000000000..d22a82b35a7e
--- /dev/null
+++ b/tools/test/stress2/misc/gnop12.sh
@@ -0,0 +1,114 @@
+#!/bin/sh
+
+#
+# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+#
+# Copyright (c) 2022 Peter Holm <pho@FreeBSD.org>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+
+# fsck test with forced unmount of a SU FS.
+# Variation of gnop8.sh by Kirk McKusick <mckusick@mckusick.com>
+
+# Long fsck_ffs runtime scenario
+
+[ `id -u ` -ne 0 ] && echo "Must be root!" && exit 1
+. ../default.cfg
+
+fsck=/sbin/fsck_ffs
+fsck_loops=10
+log=/tmp/gnop12.log
+[ -c /dev/md$mdstart ] && mdconfig -d -u $mdstart
+mdconfig -a -t swap -s 5g -u $mdstart || exit 1
+md=md$mdstart
+newfs -U /dev/$md > /dev/null 2>&1 || exit 1
+
+export LOAD=80
+export rwLOAD=80
+export runRUNTIME=10m
+export RUNDIR=$mntpoint/stressX
+export CTRLDIR=$mntpoint/stressX.control
+export MAXSWAPPCT=80
+export TESTPROGS='
+testcases/creat/creat
+'
+
+start=`date +%s`
+while [ $((`date +%s` - start)) -lt 600 ]; do
+	gnop create /dev/$md || exit 1
+	mount /dev/$md.nop $mntpoint || exit 1
+
+	rm -rf $RUNDIR $CTRLDIR
+	mkdir -p $RUNDIR $CTRLDIR
+	chmod 777 $RUNDIR $CTRLDIR
+	set `df -ik $mntpoint | tail -1 | awk '{print $4,$7}'`
+	export KBLOCKS=$(($1 / 10 * 7))
+	export INODES=$(($2 / 10 * 7))
+
+	su $testuser -c 'cd ..; ./testcases/run/run $TESTPROGS' > /dev/null 2>&1 &
+
+	# after some number of seconds
+	sleep `jot -r 1 20 30`
+	gnop destroy -f /dev/$md.nop
+	../tools/killall.sh || exit 1
+	while pgrep -qU $testuser; do pkill -U $testuser; done
+	wait
+
+	# Wait until forcible unmount, may be up to about 30 seconds,
+	# but typically very quick if I/O is in progress
+	s=`date +%s`
+	n=0
+	while mount | grep -q "on $mntpoint "; do
+		[ $n -eq 0 ] && /bin/echo -n "Waiting for $mntpoint to force umount ..."
+		n=$((n + 1))
+		sleep 5
+		if [ $((`date +%s` - s)) -ge 180 ]; then
+			echo "Giving up on waiting for umount of $mntpoint"
+			umount $mntpoint
+			while mount | grep -q "on $mntpoint "; do
+			    umount -f $mntpoint
+			done
+		fi
+	done
+	[ $n -ne 0 ] && echo
+
+	# The initial fsck_ffs may run for more than on hour with a 5GB MD disk
+	t=`date +%s`
+	$fsck -fy /dev/$md > /dev/null 2>&1
+	t=$((`date +%s`- t))
+	[ $t -gt 300 ] && { echo "First fsck took $(((t + 30) / 60)) minutes!"; e=1; }
+
+	for i in `jot $fsck_loops`; do
+		sleep 10
+		$fsck -fy /dev/$md > $log 2>&1
+		# For now, do not trust fsck_ffs's "CLEAN" message
+#		grep -Eq "IS CLEAN|MARKED CLEAN" $log && break
+		grep -Eq "FILE SYSTEM WAS MODIFIED" $log || break
+		[ $i -eq $fsck_loops ] &&
+		    { echo "$fsck did not mark FS as clean"; tail -12 $log; exit 1; }
+	done
+done
+$fsck -fy /dev/$md > $log || { tail -5 $log; exit 1; }
+mdconfig -d -u ${md#md}
+rm -f $log
+exit $e