Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: stefanha/block/qcow2.c
===================================================================
--- stefanha.orig/block/qcow2.c
+++ stefanha/block/qcow2.c
@@ -767,6 +767,20 @@ static int qcow2_change_backing_file(Blo
     return qcow2_update_ext_header(bs, backing_file, backing_fmt);
 }
 
+static BlockDriverState *qcow2_find_backing_image(BlockDriverState *bs,
+                                                  const char *id)
+{
+
+    do {
+        if (!strncmp(bs->backing_file, id, sizeof(bs->backing_file)))
+            return bs->backing_hd;
+
+        bs = bs->backing_hd;
+    } while (bs);
+
+    return NULL;
+}
+
 static int preallocate(BlockDriverState *bs)
 {
     uint64_t nb_sectors;
@@ -1304,6 +1318,7 @@ static BlockDriver bdrv_qcow2 = {
     .bdrv_load_vmstate    = qcow2_load_vmstate,
 
     .bdrv_change_backing_file   = qcow2_change_backing_file,
+    .bdrv_find_backing_image    = qcow2_find_backing_image,
 
     .bdrv_invalidate_cache      = qcow2_invalidate_cache,