block: Add support to warn on backing file change without format
For now, this is a mechanical addition; all callers pass false. But
the next patch will use it to improve 'qemu-img rebase -u' when
selecting a backing file with no format.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Message-Id: <20200706203954.341758-10-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index 6925e57..4acfebf 100644
--- a/block.c
+++ b/block.c
@@ -1206,7 +1206,8 @@
}
ret = bdrv_change_backing_file(parent, filename,
- base->drv ? base->drv->format_name : "");
+ base->drv ? base->drv->format_name : "",
+ false);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not update backing file link");
}
@@ -4680,8 +4681,8 @@
* 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)
+int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
+ const char *backing_fmt, bool warn)
{
BlockDriver *drv = bs->drv;
int ret;
@@ -4695,6 +4696,12 @@
return -EINVAL;
}
+ if (warn && backing_file && !backing_fmt) {
+ warn_report("Deprecated use of backing file without explicit "
+ "backing format, use of this image requires "
+ "potentially unsafe format probing");
+ }
+
if (drv->bdrv_change_backing_file != NULL) {
ret = drv->bdrv_change_backing_file(bs, backing_file, backing_fmt);
} else {
