Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756696Ab2JJV4H (ORCPT ); Wed, 10 Oct 2012 17:56:07 -0400 Received: from ipmail07.adl2.internode.on.net ([150.101.137.131]:36657 "EHLO ipmail07.adl2.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755199Ab2JJV4E (ORCPT ); Wed, 10 Oct 2012 17:56:04 -0400 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: ArErAK3tdVB5LIL3/2dsb2JhbABEhSm0JoRjAgJ7gQmCIAEBBTocIxAIAxIGLhQlAw0UE4gDuBoUizM7gSiEPQOVa5AxgwE Date: Thu, 11 Oct 2012 08:56:00 +1100 From: Dave Chinner To: Hugh Dickins Cc: Jan Kara , linux-mm@kvack.org, LKML , xfs@oss.sgi.com, Martin Schwidefsky , Mel Gorman , linux-s390@vger.kernel.org Subject: Re: [PATCH] mm: Fix XFS oops due to dirty pages without buffers on s390 Message-ID: <20121010215600.GX23644@dastard> References: <1349108796-32161-1-git-send-email-jack@suse.cz> <20121009162107.GE15790@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2212 Lines: 45 On Tue, Oct 09, 2012 at 07:19:09PM -0700, Hugh Dickins wrote: > On Tue, 9 Oct 2012, Jan Kara wrote: > > On Mon 08-10-12 21:24:40, Hugh Dickins wrote: > > > On Mon, 1 Oct 2012, Jan Kara wrote: > > > > > > > On s390 any write to a page (even from kernel itself) sets architecture > > > > specific page dirty bit. Thus when a page is written to via standard write, HW > > > > dirty bit gets set and when we later map and unmap the page, page_remove_rmap() > > > > finds the dirty bit and calls set_page_dirty(). > > > > > > > > Dirtying of a page which shouldn't be dirty can cause all sorts of problems to > > > > filesystems. The bug we observed in practice is that buffers from the page get > > > > freed, so when the page gets later marked as dirty and writeback writes it, XFS > > > > crashes due to an assertion BUG_ON(!PagePrivate(page)) in page_buffers() called > > > > from xfs_count_page_state(). > > > > > > What changed recently? Was XFS hardly used on s390 until now? > > The problem was originally hit on SLE11-SP2 which is 3.0 based after > > migration of our s390 build machines from SLE11-SP1 (2.6.32 based). I think > > XFS just started to be more peevish about what pages it gets between these > > two releases ;) (e.g. ext3 or ext4 just says "oh, well" and fixes things > > up). > > Right, in 2.6.32 xfs_vm_writepage() had a !page_has_buffers(page) case, > whereas by 3.0 that had become ASSERT(page_has_buffers(page)), with the > ASSERT usually compiled out, stumbling later in page_buffers() as you say. What that says is that no-one is running xfstests-based QA on s390 with CONFIG_XFS_DEBUG enabled, otherwise this would have been found. I've never tested XFS on s390 before, and I doubt any of the upstream developers have, either, because not many peopl ehave s390 machines in their basement. So this is probably just an oversight in the distro QA environment more than anything.... Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/