block-copy: Use CAF to find sync=top base

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/block-copy.c b/block/block-copy.c
index a30b909..cd9bc47 100644 (file)
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -440,8 +440,8 @@ static int block_copy_block_status(BlockCopyState *s, int64_t offset,
     BlockDriverState *base;
     int ret;
 
-    if (s->skip_unallocated && s->source->bs->backing) {
-        base = s->source->bs->backing->bs;
+    if (s->skip_unallocated) {
+        base = bdrv_backing_chain_next(s->source->bs);
     } else {
         base = NULL;
     }