On Fri, Oct 02, 2020 at 03:36:11AM +0900, Naohiro Aota wrote: > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -588,6 +588,9 @@ struct btrfs_fs_info { > struct btrfs_root *free_space_root; > struct btrfs_root *data_reloc_root; > > + /* Zone size when in ZONED mode */ > + u64 zone_size; I think this could be reused to avoid the lengthy if (btrfs_fs_incompat(fs_info, ZONED)) to do if (fs_info->zoned) In order to keep the semantics of both an anonymouns union should work: union { u64 zone_size; u64 zone; }; and the existing usage of zone_size can be kept intact.