Re: [PATCH v8 16/19] fsnotify: generate pre-content permission event on page fault

Jan Kara
2024-12-09T12:34:11Z

On Mon 09-12-24 16:15:32, Aithal, Srikanth wrote:
> On 12/8/2024 10:28 PM, Klara Modin wrote:
> > Hi,
> >
> > On 2024-11-15 16:30, Josef Bacik wrote:
> > > FS_PRE_ACCESS or FS_PRE_MODIFY will be generated on page fault depending
> > > on the faulting method.
> > >
> > > This pre-content event is meant to be used by hierarchical storage
> > > managers that want to fill in the file content on first read access.
> > >
> > > Export a simple helper that file systems that have their own ->fault()
> > > will use, and have a more complicated helper to be do fancy things with
> > > in filemap_fault.
> > >
> >
> > This patch (0790303ec869d0fd658a548551972b51ced7390c in next-20241206)
> > interacts poorly with some programs which hang and are stuck at 100 %
> > sys cpu usage (examples of programs are logrotate and atop with root
> > privileges).
> >
> > I also retested the new version on Jan Kara's for_next branch and it
> > behaves the same way.
>
> From linux-next20241206 onward we started hitting issues where KVM guests
> running kernel > next20241206 on AMD platforms fails to shutdown, hangs
> forever with below errors:

Thanks for report! This was discussed in [1] and I've just pushed out a
branch which has this bug fixed.

[1] https://lore.kernel.org/all/20241208152520.3559-1-spasswolf@web.de

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