On Tue 07-11-23 23:51:58, Christoph Hellwig wrote: > On Mon, Nov 06, 2023 at 05:42:10PM -0500, Josef Bacik wrote: > > Again, this is where I'm confused, because this doesn't change anything, we're > > still going to report st_dev as being different, which is what you hate. > > It's not something I hate. It's that changing it without a mount point > has broken things and will probably still break things. So let me maybe return to what has started this thread. For fanotify we return <fsid, fhandle> pair with events to identify object where something happened. The fact that fsid is not uniform for all inodes of a superblock on btrfs is what triggered this series because we are then faced with the problem that caching fsid per superblock for "superblock marks" (to save CPU overhead when generating events) can lead to somewhat confusing results on btrfs. Whether we have vfsmount in the places where inodes' st_dev / fsid change is irrelevant for this fanotify issue. As far as I'm following the discussion it seems the non-uniform fsids per superblock are going to stay with us on btrfs so fanotify code should better accommodate them? At least by making sure the behavior is somewhat consistent and documented... Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
