block: test 'blockdev-snapshot' using a file BDS as the overlay

This test checks that it is not possible to create a snapshot if the
requested overlay node is a BDS which does not support backing images.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/085

@@ -103,7 +103,8 @@ function add_snapshot_image()
            { 'options':
              { 'driver': 'qcow2', 'node-name': 'snap_${1}', ${extra_params}
                'file':
-               { 'driver': 'file', 'filename': '${snapshot_file}' } } } }"
+               { 'driver': 'file', 'filename': '${snapshot_file}',
+                 'node-name': 'file_${1}' } } } }"
     _send_qemu_cmd $h "${cmd}" "return"
 }
 
@@ -186,6 +187,15 @@ SNAPSHOTS=$((${SNAPSHOTS}+1))
 add_snapshot_image ${SNAPSHOTS}
 blockdev_snapshot ${SNAPSHOTS}
 
+echo
+echo === Invalid command - cannot create a snapshot using a file BDS ===
+echo
+
+_send_qemu_cmd $h "{ 'execute': 'blockdev-snapshot',
+                     'arguments': { 'node':'virtio0',
+                                    'overlay':'file_${SNAPSHOTS}' }
+                   }" "error"
+
 echo
 echo === Invalid command - snapshot node used as active layer ===
 echo

tests/qemu-iotests/085.out

@@ -62,6 +62,10 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/
 {"return": {}}
 {"return": {}}
 
+=== Invalid command - cannot create a snapshot using a file BDS ===
+
+{"error": {"class": "GenericError", "desc": "The snapshot does not support backing images"}}
+
 === Invalid command - snapshot node used as active layer ===
 
 {"error": {"class": "GenericError", "desc": "The snapshot is already in use by virtio0"}}