Re: [PATCH v4 15/16] gfs2: add pre-content fsnotify hook to fault

Amir Goldstein
2024-08-29T11:26:29Z

On Thu, Aug 29, 2024 at 1:15 PM Jan Kara <jack@suse.cz> wrote:
>
> On Wed 14-08-24 17:25:33, Josef Bacik wrote:
> > gfs2 takes the glock before calling into filemap fault, so add the
> > fsnotify hook for ->fault before we take the glock in order to avoid any
> > possible deadlock with the HSM.
> >
> > Signed-off-by: Josef Bacik <josef@toxicpanda.com>
>
> The idea of interactions between GFS2 cluster locking and HSM gives me
> creeps. But yes, this patch looks good to me. Would be nice to get ack from
> GFS2 guys. Andreas?

If we are being honest, I think that the fact that HSM events require careful
handling in ->fault() and not to mention no documentation of this fact,
perhaps we should let HSM events be an opt-in file_system_type feature?

Additionally, we had to introduce FS_DISALLOW_NOTIFY_PERM
and restrict sb marks on SB_NOUSER, all because these fanotify
features did not require fs opt-in to begin with.

I think we would be repeating this mistake if we do not add
FS_ALLOW_HSM from the start.

After all, I cannot imagine HSM being used on anything but
the major disk filesystems.

Hmm?

Amir.