linux-kernel - Removing Mandatory Locks

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Date:   Tue, 17 Aug 2021 11:48:12 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        David Laight <David.Laight@...lab.com>,
        David Hildenbrand <david@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Peter Zijlstra \(Intel\)" <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Kees Cook <keescook@...omium.org>,
        Greg Ungerer <gerg@...ux-m68k.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Mike Rapoport <rppt@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Chinwen Chang <chinwen.chang@...iatek.com>,
        Michel Lespinasse <walken@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Huang Ying <ying.huang@...el.com>,
        Jann Horn <jannh@...gle.com>, Feng Tang <feng.tang@...el.com>,
        Kevin Brodsky <Kevin.Brodsky@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Shawn Anastasio <shawn@...stas.io>,
        Steven Price <steven.price@....com>,
        Nicholas Piggin <npiggin@...il.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Jens Axboe <axboe@...nel.dk>,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        Peter Xu <peterx@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Nicolas Viennot <Nicolas.Viennot@...sigma.com>,
        Thomas Cedeno <thomascedeno@...gle.com>,
        Collin Fijalkovich <cfijalkovich@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Chengguang Xu <cgxu519@...ernel.net>,
        Christian König 
        <ckoenig.leichtzumerken@...il.com>,
        "linux-unionfs\@vger.kernel.org" <linux-unionfs@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        "\<linux-fsdevel\@vger.kernel.org\>" <linux-fsdevel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Florian Weimer <fweimer@...hat.com>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Removing Mandatory Locks

Matthew Wilcox <willy@...radead.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.

Does anyone know the appropriate people to talk to encourage other
distro's to encourage them to disable the CONFIG_MANDATORY_FILE_LOCKING?

Either that or we can wait until the code bit-rots, but distro's
disabling and removing a feature on their own is the more responsible
path.

Given how many hoops need to be jumped through to use mandatory file
locking once it is enabled, and the fact it has never worked in
containers makes me suspect there are no more users.

Eric