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>
diff --git a/block.c b/block.c
index 994109e..c7bc837 100644
--- a/block.c
+++ b/block.c
@@ -597,6 +597,26 @@
return 0;
}
+/*
+ * Return values:
+ * 0 - success
+ * -EINVAL - backing format specified, but no file
+ * -ENOSPC - can't update the backing file because no space is left in the
+ * image file header
+ * -ENOTSUP - format driver doesn't support changing the backing file
+ */
+int bdrv_change_backing_file(BlockDriverState *bs,
+ const char *backing_file, const char *backing_fmt)
+{
+ BlockDriver *drv = bs->drv;
+
+ if (drv->bdrv_change_backing_file != NULL) {
+ return drv->bdrv_change_backing_file(bs, backing_file, backing_fmt);
+ } else {
+ return -ENOTSUP;
+ }
+}
+
static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
size_t size)
{
