static int qcow2_change_backing_file(BlockDriverState *bs, const char *backing_file, const char *backing_fmt) { /* Backing file format doesn't make sense without a backing file */ if (backing_fmt && !backing_file) { return -EINVAL; } pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: ""); pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: ""); return qcow2_update_header(bs); }