From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx151.postini.com [74.125.245.151]) by kanga.kvack.org (Postfix) with SMTP id 7F3926B0072 for ; Tue, 23 Oct 2012 17:56:37 -0400 (EDT) Date: Tue, 23 Oct 2012 14:56:36 -0700 From: Andrew Morton Subject: Re: [PATCH] mm: Fix XFS oops due to dirty pages without buffers on s390 Message-Id: <20121023145636.0a9b9a3e.akpm@linux-foundation.org> In-Reply-To: <20121023102153.GD3064@quack.suse.cz> References: <1350918406-11369-1-git-send-email-jack@suse.cz> <20121022123852.a4bd5f2a.akpm@linux-foundation.org> <20121023102153.GD3064@quack.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: linux-mm@kvack.org, Martin Schwidefsky , Mel Gorman , linux-s390@vger.kernel.org, Hugh Dickins On Tue, 23 Oct 2012 12:21:53 +0200 Jan Kara wrote: > > That seems a fairly serious problem. To which kernel version(s) should > > we apply the fix? > Well, XFS will crash starting from 2.6.36 kernel where the assertion was > added. Previously XFS just silently added buffers (as other filesystems do > it) and wrote / redirtied the page (unnecessarily). So looking into > maintained -stable branches I think pushing the patch to -stable from 3.0 > on should be enough. OK, thanks, I made it so. > > > diff --git a/mm/rmap.c b/mm/rmap.c > > > > It's a bit surprising that none of the added comments mention the s390 > > pte-dirtying oddity. I don't see an obvious place to mention this, but > > I for one didn't know about this and it would be good if we could > > capture the info _somewhere_? > As Hugh says, the comment before page_test_and_clear_dirty() is somewhat > updated. But do you mean recording somewhere the catch that s390 HW dirty > bit gets set also whenever we write to a page from kernel? Yes, this. It's surprising behaviour which we may trip over again, so how do we inform developers about it? > I guess we could > add that also to the comment before page_test_and_clear_dirty() in > page_remove_rmap() and also before definition of > page_test_and_clear_dirty(). So most people that will add / remove these > calls will be warned. OK? Sounds good, thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org