lsm sb_delete hook, was Re: [PATCH 4/7] vfs: Convert sb->s_inodes iteration to super_iter_inodes()

[Jan Kara]

On Mon 07-10-24 17:54:16, Linus Torvalds wrote:
> On Mon, 7 Oct 2024 at 17:28, Linus Torvalds
> <torvalds at linux-foundation.org> wrote:
> >
> > And yes, this changes the timing on when fsnotify events happen, but
> > what I'm actually hoping for is that Jan will agree that it doesn't
> > actually matter semantically.
> 
> .. and yes, I realize it might actually matter. fsnotify does do
> 'ihold()' to hold an inode ref, and with this that would actually be
> more or less pointless, because the mark would be removed _despite_
> such a ref.
> 
> So maybe it's not an option to do what I suggested. I don't know the
> users well enough.

Yeah, we need to keep the notification mark alive either until the inode is
deleted or until the filesystem is unmounted to maintain behavior of
inotify and fanotify APIs.

That being said we could rework lifetime rules inside fsnotify subsystem as
Dave suggests so that fsnotify would not pin inodes, detach it's structures
from inodes on inode reclaim and associate notification marks with inodes
when they are loaded from disk.  But it's a relatively big overhaul.

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