- bs = bdrv_open(full_backing, NULL, backing_options, back_flags,
- &local_err);
- g_free(full_backing);
- if (!bs) {
- goto out;
- }
- size = bdrv_getlength(bs);
- if (size < 0) {
- error_setg_errno(errp, -size, "Could not get size of '%s'",
- backing_file);
- bdrv_unref(bs);
- goto out;
+ bs = bdrv_open(full_backing, NULL, backing_options, back_flags,
+ &local_err);
+ g_free(full_backing);
+ if (!bs && size != -1) {
+ /* Couldn't open BS, but we have a size, so it's nonfatal */
+ warn_reportf_err(local_err,
+ "Could not verify backing image. "
+ "This may become an error in future versions.\n");
+ local_err = NULL;
+ } else if (!bs) {
+ /* Couldn't open bs, do not have size */
+ error_append_hint(&local_err,
+ "Could not open backing image to determine size.\n");
+ goto out;
+ } else {
+ if (size == -1) {
+ /* Opened BS, have no size */
+ size = bdrv_getlength(bs);
+ if (size < 0) {
+ error_setg_errno(errp, -size, "Could not get size of '%s'",
+ backing_file);
+ bdrv_unref(bs);
+ goto out;
+ }
+ qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);