overlay/036: filter busy mount message

util-linux v2.30 changed error message of a busy mount and caused
overlay/036 to fail. e.g.

 - mount: <device> is already mounted or <mountpoint> busy
 + mount: <mountpoint>: <device> already mounted or mount point busy.

Filter the mount output by a newly introduced _filter_busy_mount
into a unified format.

   mount: device already mounted or mount point busy

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

common/filter

@@ -423,6 +423,18 @@ _filter_error_mount()
 	sed -e "s/mount:\(.*failed:\)/mount:/" | _filter_ending_dot
 }
 
+# Similar to _filter_error_mount, filter a busy mount output.
+# Turn both old (prior to util-linux v2.30) and new (v2.30 and later) format to
+# a simple one. e.g.
+# old: mount: <device> is already mounted or <mountpoint> busy
+# new: mount: <mountpoint>: <device> already mounted or mount point busy.
+# filtered: mount: device already mounted or mount point busy
+_filter_busy_mount()
+{
+	sed -e "s/.*: .* already mounted or .* busy/mount: device already mounted or mount point busy/" | \
+		_filter_ending_dot
+}
+
 _filter_od()
 {
 	BLOCK_SIZE=$(_get_block_size $SCRATCH_MNT)

tests/overlay/036

@@ -103,12 +103,12 @@ _overlay_mount_dirs $lowerdir2 $upperdir2 $workdir \
 # Try to mount another overlay with the same upperdir
 # with index=on - expect EBUSY
 _overlay_mount_dirs $lowerdir2 $upperdir $workdir2 \
-		    overlay2 $SCRATCH_MNT -oindex=on 2>&1 | _filter_scratch
+	    overlay2 $SCRATCH_MNT -oindex=on 2>&1 | _filter_busy_mount
 
 # Try to mount another overlay with the same workdir
 # with index=on - expect EBUSY
 _overlay_mount_dirs $lowerdir2 $upperdir2 $workdir \
-		    overlay3 $SCRATCH_MNT -oindex=on 2>&1 | _filter_scratch
+	    overlay3 $SCRATCH_MNT -oindex=on 2>&1 | _filter_busy_mount
 
 
 # success, all done

tests/overlay/036.out

@@ -1,3 +1,3 @@
 QA output created by 036
-mount: overlay2 is already mounted or SCRATCH_MNT busy
+mount: device already mounted or mount point busy
-mount: overlay3 is already mounted or SCRATCH_MNT busy
+mount: device already mounted or mount point busy