diff --git a/common/config b/common/config
index db5721c..f431a8d 100644
--- a/common/config
+++ b/common/config
@@ -35,7 +35,9 @@
 # RMT_TAPE_DEV -    the remote tape device for the xfsdump tests
 # RMT_IRIXTAPE_DEV- the IRIX remote tape device for the xfsdump tests
 # RMT_TAPE_USER -   remote user for tape device
+# TEST_BASE_DEV -   device for base fs containing overlay test dirs
 # TEST_BASE_MNT -   mount point for base fs of overlay test dirs
+# SCRATCH_BASE_DEV- device for base fs containing overlay scratch dirs
 # SCRATCH_BASE_MNT- mount point for base fs of overlay scratch dirs
 #
 # - These can be added to $HOST_CONFIG_DIR (witch default to ./config)
@@ -470,11 +472,12 @@ _config_overlay()
 	[ -z "$TEST_DEV" ] || export TEST_BASE_DIR="$TEST_DEV"
 	[ -z "$SCRATCH_DEV" ] || export SCRATCH_BASE_DIR="$SCRATCH_DEV"
 
-	# 2. set SCRATCH/TEST_BASE_MNT to configure base fs.
+	# 2. set SCRATCH/TEST_BASE_DEV/MNT to configure base fs.
 	#    SCRATCH/TEST_DEV are derived from SCRATCH/TEST_BASE_MNT
 	#    and therein, overlay fs directories will be created.
 	[ -n "$TEST_BASE_MNT" ] || return
 
+	_check_device TEST_BASE_DEV optional $TEST_BASE_DEV
 	if [ ! -d "$TEST_BASE_MNT" ]; then
 		echo "common/config: Error: \$TEST_BASE_MNT ($TEST_BASE_MNT) is not a directory"
 		exit 1
@@ -486,6 +489,7 @@ _config_overlay()
 
 	[ -n "$SCRATCH_BASE_MNT" ] || return
 
+	_check_device SCRATCH_BASE_DEV optional $SCRATCH_BASE_DEV
 	if [ ! -d "$SCRATCH_BASE_MNT" ]; then
 		echo "common/config: Error: \$SCRATCH_BASE_MNT ($SCRATCH_BASE_MNT) is not a directory"
 		exit 1
diff --git a/common/rc b/common/rc
index f5ab869..5033ed4 100644
--- a/common/rc
+++ b/common/rc
@@ -320,24 +320,62 @@ _overlay_mount()
 			    $SELINUX_MOUNT_OPTIONS $* $dir $mnt
 }
 
+_overlay_test_base_mount()
+{
+	if [ -n "$TEST_BASE_DEV" -a -n "$TEST_BASE_MNT" ]; then
+		_mount $TEST_BASE_MOUNT_OPTIONS \
+			$SELINUX_MOUNT_OPTIONS \
+			$TEST_BASE_DEV $TEST_BASE_MNT
+	fi
+}
+
 _overlay_test_mount()
 {
+	_overlay_test_base_mount
 	_overlay_mount $TEST_BASE_DIR $TEST_DIR $*
 }
 
+_overlay_scratch_base_mount()
+{
+	if [ -n "$SCRATCH_BASE_DEV" -a -n "$SCRATCH_BASE_MNT" ]; then
+		_mount $SCRATCH_BASE_MOUNT_OPTIONS \
+			$SELINUX_MOUNT_OPTIONS \
+			$SCRATCH_BASE_DEV $SCRATCH_BASE_MNT
+	fi
+}
+
+_overlay_scratch_base_unmount()
+{
+	if [ -n "$SCRATCH_BASE_DEV" -a -n "$SCRATCH_BASE_MNT" ]; then
+		$UMOUNT_PROG $SCRATCH_BASE_MNT
+	fi
+}
+
 _overlay_scratch_mount()
 {
+	# base fs may be mounted after overlay mkfs
+	_overlay_scratch_base_unmount 2>/dev/null
+	_overlay_scratch_base_mount
 	_overlay_mount $SCRATCH_BASE_DIR $SCRATCH_MNT $*
 }
 
+_overlay_test_base_unmount()
+{
+	if [ -n "$TEST_BASE_DEV" -a -n "$TEST_BASE_MNT" ]; then
+		$UMOUNT_PROG $TEST_BASE_MNT
+	fi
+}
+
 _overlay_test_unmount()
 {
 	$UMOUNT_PROG $TEST_DIR
+	_overlay_test_base_unmount
 }
 
 _overlay_scratch_unmount()
 {
 	$UMOUNT_PROG $SCRATCH_MNT
+	_overlay_scratch_base_unmount
 }
 
 _scratch_mount()
@@ -643,7 +681,11 @@ _scratch_cleanup_files()
 	overlay)
 		# Avoid rm -rf /* if we messed up
 		[ -n "$SCRATCH_BASE_DIR" ] || return
+		# overlay 'mkfs' needs to make sure base fs is mounted and clean
+		_overlay_scratch_base_unmount 2>/dev/null
+		_overlay_scratch_base_mount
 		rm -rf $SCRATCH_BASE_DIR/*
+		# leave base fs mouted so tests can setup lower dir
 		;;
 	*)
 		[ -n "$SCRATCH_MNT" ] || return
diff --git a/tests/overlay/003 b/tests/overlay/003
index bb59700..81aea85 100755
--- a/tests/overlay/003
+++ b/tests/overlay/003
@@ -89,7 +89,8 @@ rm -rf ${SCRATCH_MNT}/*
 # nothing should be listed
 ls ${SCRATCH_MNT}/
 
-_scratch_unmount
+# unmount overlayfs but not base fs
+$UMOUNT_PROG $SCRATCH_MNT
 
 rm -rf $lowerdir
 echo "Silence is golden"
diff --git a/tests/overlay/004 b/tests/overlay/004
index 6d78f9f..26ac547 100755
--- a/tests/overlay/004
+++ b/tests/overlay/004
@@ -85,7 +85,8 @@ _user_do "chmod g+t ${SCRATCH_MNT}/attr_file2 > /dev/null 2>&1"
 _user_do "chmod u-X ${SCRATCH_MNT}/attr_file2 > /dev/null 2>&1"
 stat -c %a ${SCRATCH_MNT}/attr_file2
 
-_scratch_unmount
+# unmount overlayfs but not base fs
+$UMOUNT_PROG $SCRATCH_MNT
 
 # check mode bits of the file that has been copied up, and
 # the file that should not have been copied up.
diff --git a/tests/overlay/014 b/tests/overlay/014
index 7426c31..6519432 100755
--- a/tests/overlay/014
+++ b/tests/overlay/014
@@ -73,7 +73,8 @@ mkdir -p $lowerdir1/testdir/d
 _overlay_mount_dirs $lowerdir1 $lowerdir2 $workdir $SCRATCH_BASE_DIR $SCRATCH_MNT
 rm -rf $SCRATCH_MNT/testdir
 mkdir -p $SCRATCH_MNT/testdir/visibledir
-_scratch_unmount
+# unmount overlayfs but not base fs
+$UMOUNT_PROG $SCRATCH_MNT
 
 # mount overlay again, with lowerdir1 and lowerdir2 as multiple lowerdirs,
 # and create a new file in testdir, triggers copyup from lowerdir,
@@ -84,7 +85,7 @@ touch $SCRATCH_MNT/testdir/visiblefile
 
 # umount and mount overlay again, buggy kernel treats the copied-up dir as
 # opaque, visibledir is not seen in merged dir.
-_scratch_unmount
+$UMOUNT_PROG $SCRATCH_MNT
 _overlay_mount_dirs "$lowerdir2:$lowerdir1" $upperdir $workdir \
 		    $SCRATCH_BASE_DIR $SCRATCH_MNT
 ls $SCRATCH_MNT/testdir
