Re: Removing Mandatory Locks

Willy Tarreau
2021-08-19T20:06:40Z

On Thu, Aug 19, 2021 at 03:18:15PM -0400, Jeff Layton wrote:
> On Wed, 2021-08-18 at 11:34 +0200, Rodrigo Campos wrote:
> > On Tue, Aug 17, 2021 at 6:49 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
> > >
> > > Matthew Wilcox <willy@infradead.org> writes:
> > >
> > > > On Fri, Aug 13, 2021 at 05:49:19PM -0700, Andy Lutomirski wrote:
> > > > > [0] we have mandatory locks, too. Sigh.
> > > >
> > > > I'd love to remove that. Perhaps we could try persuading more of the
> > > > distros to disable the CONFIG option first.
> > >
> > > Yes. The support is disabled in RHEL8.
> >
> > If it helps, it seems to be enabled on the just released debian stable:
> > $ grep CONFIG_MANDATORY_FILE_LOCKING /boot/config-5.10.0-8-amd64
> > CONFIG_MANDATORY_FILE_LOCKING=y
> >
> > Also the new 5.13 kernel in experimental has it too:
> > $ grep CONFIG_MANDATORY_FILE_LOCKING /boot/config-5.13.0-trunk-amd64
> > CONFIG_MANDATORY_FILE_LOCKING=y
>
> A pity. It would have been nice if they had turned it off a while ago. I
> guess I should have done more outreach at the time. Sigh...

Would it be acceptable to add a warning when MS_MANDLOCK is passed to
mount() and backport this to stable kernels in order to get reports
of any such use in a reasonably short time ? Anyway it sounds
important to at least warn about deprecation.

Willy