On Thu, 22 Feb 2024 at 17:08, Jan Kara <jack@xxxxxxx> wrote: > > If we are going to start fixing userspace, then we better make sure to > > use the right interfaces, that won't have issues in the future. > > I agree we should give this a good thought which identification of a > filesystem is the best. To find mount boundaries statx.stx_mnt_id (especially with STATX_MNT_ID_UNIQUE) is perfect. By supplying stx_mnt_id to statmount(2) it's possible to get the device number associated with that filesystem (statmount.sb_dev_*). I think it's what Josef wants btrfs to return as st_dev. And statx could return that in stx_dev_*, with an interface feature flag, same as we've done with stx_mnt_id. I.e. STATX_DEV_NOHACK would force the vfs to replace anything the filesystem put in kstat.dev with sb->s_dev. Thanks, Miklos
