block: Introduce BdrvChildRole.update_filename
There is no good reason for bdrv_drop_intermediate() to know the active
layer above the subchain it is operating on - even more so, because
the assumption that there is a single active layer above it is not
generally true.
In order to prepare removal of the active parameter, use a BdrvChildRole
callback to update the backing file string in the overlay image instead
of directly calling bdrv_change_backing_file().
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 79366b9..7e8a206 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -544,6 +544,12 @@
void (*attach)(BdrvChild *child);
void (*detach)(BdrvChild *child);
+
+ /* Notifies the parent that the filename of its child has changed (e.g.
+ * because the direct child was removed from the backing chain), so that it
+ * can update its reference. */
+ int (*update_filename)(BdrvChild *child, BlockDriverState *new_base,
+ const char *filename, Error **errp);
};
extern const BdrvChildRole child_file;
