Re: [PATCH 0/3] fanotify support for btrfs sub-volumes

Jan Kara
2023-10-25T17:04:52Z

On Wed 25-10-23 08:34:21, Christoph Hellwig wrote:
> On Wed, Oct 25, 2023 at 04:50:45PM +0300, Amir Goldstein wrote:
> > Jan,
> >
> > This patch set implements your suggestion [1] for handling fanotify
> > events for filesystems with non-uniform f_fsid.
>
> File systems nust never report non-uniform fsids (or st_dev) for that
> matter. btrfs is simply broken here and needs to be fixed.

Well, this is the discussion how btrfs should be presenting its subvolumes
to VFS / userspace, isn't it? I never dived into that too closely but as
far as I remember it was discussed to death without finding an acceptable
(to all parties) solution? I guess having a different fsid per subvolume
makes sense (and we can't change that given it is like that forever even if
we wanted). Having different subvolumes share one superblock is more
disputable but there were reasons for that as well. So I'm not sure how you
imagine to resolve this...

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR