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Date:   Thu, 19 Aug 2021 22:03:23 +0200
From:   Willy Tarreau <w@1wt.eu>
To:     Jeff Layton <jlayton@kernel.org>
Cc:     Rodrigo Campos <rodrigo@kinvolk.io>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Matthew Wilcox <willy@infradead.org>,
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Subject: Re: Removing Mandatory Locks
Message-ID: <20210819200323.GA13017@1wt.eu>
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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