From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754627AbaGHVPL (ORCPT ); Tue, 8 Jul 2014 17:15:11 -0400 Received: from mail-lb0-f178.google.com ([209.85.217.178]:33548 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753411AbaGHVPJ (ORCPT ); Tue, 8 Jul 2014 17:15:09 -0400 Date: Wed, 9 Jul 2014 01:15:06 +0400 From: Cyrill Gorcunov To: Andrew Morton Cc: LKML , Linux MM , Pavel Emelyanov Subject: Re: [PATCH] mm: Don't forget to set softdirty on file mapped fault Message-ID: <20140708211506.GI17860@moon.sw.swsoft.com> References: <20140708192151.GD17860@moon.sw.swsoft.com> <20140708131920.2a857d573e8cc89780c9fa1c@linux-foundation.org> <20140708204017.GG17860@moon.sw.swsoft.com> <20140708134511.4a32b7400a952541a31e9078@linux-foundation.org> <20140708205448.GH17860@moon.sw.swsoft.com> <20140708140501.6c293226bfd87e4dff7ef7fb@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140708140501.6c293226bfd87e4dff7ef7fb@linux-foundation.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 08, 2014 at 02:05:01PM -0700, Andrew Morton wrote: > > > > In case if page fault happend on dirty filemapping the newly created pte > > may loose softdirty bit thus if a userspace program is tracking memory > > changes with help of a memory tracker (CONFIG_MEM_SOFT_DIRTY) it might > > miss modification of a memory page (which in worts case may lead to > > data inconsistency). > > Much better, thanks. > > It's a rather gross-looking bug and data inconsistency sounds serious. > Do you think a -stable backport is needed? It seems the memory tracker is not that widespread in userspace programs (I mean at the moment as far as I know only we use it intensively) so I don't consider it as critical but moving it into stable won't hurt. Still I fear in 3.16 the mm/memory.c code has been significantly reworked so this patch won't apply on its own. I can prepare a patch for 3.15 though, just say a word.