block: Add bdrv_change_backing_file

Introduce the functions needed to change the backing file of an image. The
function is implemented for qcow2.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/block.h b/block.h
index f660d5f4d..bee9ec566 100644
--- a/block.h
+++ b/block.h
@@ -83,6 +83,8 @@ int64_t bdrv_getlength(BlockDriverState *bs);
 void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
 void bdrv_guess_geometry(BlockDriverState *bs, int *pcyls, int *pheads, int *psecs);
 int bdrv_commit(BlockDriverState *bs);
+int bdrv_change_backing_file(BlockDriverState *bs,
+    const char *backing_file, const char *backing_fmt);
 void bdrv_register(BlockDriver *bdrv);
 
 /* async block I/O */