[Qemu-devel] [PATCH] block: fix the use of protocols in backing files

[Anthony Liguori]

Signed-off-by: Anthony Liguori <aligu...@us.ibm.com>

diff --git a/block.c b/block.c
index 1a965b2..00b6f21 100644
--- a/block.c
+++ b/block.c
@@ -603,10 +603,16 @@ int bdrv_open(BlockDriverState *bs, const char *filename, 
int flags,
         BlockDriver *back_drv = NULL;
 
         bs->backing_hd = bdrv_new("");
-        path_combine(backing_filename, sizeof(backing_filename),
-                     filename, bs->backing_file);
-        if (bs->backing_format[0] != '\0')
-            back_drv = bdrv_find_format(bs->backing_format);
+        back_drv = bdrv_find_protocol(bs->backing_file);
+        if (!back_drv) {
+            path_combine(backing_filename, sizeof(backing_filename),
+                         filename, bs->backing_file);
+            if (bs->backing_format[0] != '\0')
+                back_drv = bdrv_find_format(bs->backing_format);
+        } else {
+            pstrcpy(backing_filename, sizeof(backing_filename),
+                    bs->backing_file);
+        }
 
         /* backing files always opened read-only */
         back_flags =
-- 
1.7.0.4