diff --git a/tools/test/stress2/misc/all.exclude b/tools/test/stress2/misc/all.exclude
index d4a57af4d559..5106478ff2d0 100644
--- a/tools/test/stress2/misc/all.exclude
+++ b/tools/test/stress2/misc/all.exclude
@@ -73,6 +73,8 @@ truss3.sh		WiP								20200915
 unionfs.sh		insmntque: non-locked vp: xx is not exclusive locked...		20130909
 unionfs2.sh		insmntque: mp-safe fs and non-locked vp is not ...		20111219
 unionfs3.sh		insmntque: mp-safe fs and non-locked vp is not ...		20111216
+unionfs4.sh		WiP								20210916
+unionfs5.sh		WiP								20210916
 
 # Test not to run for other reasons:
 
diff --git a/tools/test/stress2/misc/unionfs4.sh b/tools/test/stress2/misc/unionfs4.sh
new file mode 100755
index 000000000000..557cead66389
--- /dev/null
+++ b/tools/test/stress2/misc/unionfs4.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+
+#
+# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+#
+# Copyright (c) 2021 Peter Holm
+#
+# 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.
+#
+
+# "mkdir: mkdir(d2), level 2. mkdir.c:96: No such file or directory" seen
+# with a non debug kernel.
+
+[ `id -u ` -ne 0 ] && echo "Must be root!" && exit 1
+. ../default.cfg
+
+# unionfs usage example from the man page:
+#	   mount -t cd9660 -o ro /dev/cd0 /usr/src
+#	   mount -t unionfs -o noatime /var/obj	/usr/src
+
+md1=$mdstart
+md2=$((md1 + 1))
+mp1=/mnt$md1
+mp2=/mnt$md2
+mkdir -p $mp1 $mp2
+set -e
+for i in $mp1 $mp2; do
+	mount | grep -q "on $i " && umount -f $i
+done
+for i in $md1 $md2; do
+	mdconfig -l | grep -q md$i && mdconfig -d -u $i
+done
+
+mdconfig -a -t swap -s 2g -u $md1
+mdconfig -a -t swap -s 2g -u $md2
+newfs $newfs_flags -n md$md1 > /dev/null
+newfs $newfs_flags -n md$md2 > /dev/null
+mount /dev/md$md1 $mp1
+mount /dev/md$md2 $mp2
+
+mount -t unionfs -o noatime $mp1 $mp2
+set +e
+mount | grep -E "$mp1|$mp2"
+
+export RUNDIR=$mp2/stressX
+export runRUNTIME=2m 
+
+(cd ..; ./run.sh marcus.cfg)
+
+../tools/killall.sh
+umount $mp2	# The unionfs mount
+umount $mp2
+n=`find $mp1/stressX | wc -l`
+[ $n -eq 1 ] && s=0 || { find $mp1/stressX -ls | head -12; s=1; }
+umount $mp1
+mdconfig -d -u $md2
+mdconfig -d -u $md1
+exit $s
diff --git a/tools/test/stress2/misc/unionfs5.sh b/tools/test/stress2/misc/unionfs5.sh
new file mode 100755
index 000000000000..ba00fa2b5258
--- /dev/null
+++ b/tools/test/stress2/misc/unionfs5.sh
@@ -0,0 +1,83 @@
+#!/bin/sh
+
+#
+# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+#
+# Copyright (c) 2021 Peter Holm
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+
+# "mkdir: mkdir(d2), level 2. mkdir.c:96: No such file or directory" seen
+# with a non debug kernel.
+
+[ `id -u ` -ne 0 ] && echo "Must be root!" && exit 1
+. ../default.cfg
+
+# unionfs usage example from the man page:
+#	   mount -t cd9660 -o ro /dev/cd0 /usr/src
+#	   mount -t unionfs -o noatime /var/obj	/usr/src
+
+md1=$mdstart
+md2=$((md1 + 1))
+mp1=/mnt$md1
+mp2=/mnt$md2
+mkdir -p $mp1 $mp2
+set -e
+for i in $mp1 $mp2; do
+	mount | grep -q "on $i " && umount -f $i
+done
+for i in $md1 $md2; do
+	mdconfig -l | grep -q md$i && mdconfig -d -u $i
+done
+
+mdconfig -a -t swap -s 2g -u $md1
+mdconfig -a -t swap -s 2g -u $md2
+newfs $newfs_flags -n md$md1 > /dev/null
+newfs $newfs_flags -n md$md2 > /dev/null
+mount /dev/md$md1 $mp1
+mount /dev/md$md2 $mp2
+
+mount -t unionfs -o noatime $mp1 $mp2
+set +e
+mount | grep -E "$mp1|$mp2"
+
+if [ $# -eq 0 ]; then
+	echo "Using unionfs"
+	export RUNDIR=$mp2/stressX
+else
+	echo "Using FFS"
+	export RUNDIR=$mp1/stressX
+fi
+export runRUNTIME=2m 
+
+(cd ../testcases/mkdir; ./mkdir -t 2m -i 20)
+
+find $RUNDIR -ls
+umount $mp2	# The unionfs mount
+umount $mp2
+n=`find $mp1/stressX | wc -l`
+[ $n -eq 1 ] && s=0 || s=1
+umount $mp1
+mdconfig -d -u $md2
+mdconfig -d -u $md1
+exit $s