From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx185.postini.com [74.125.245.185]) by kanga.kvack.org (Postfix) with SMTP id 104AB6B002B for ; Thu, 11 Oct 2012 03:44:13 -0400 (EDT) Received: from /spool/local by e06smtp17.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 11 Oct 2012 08:44:11 +0100 Received: from d06av03.portsmouth.uk.ibm.com (d06av03.portsmouth.uk.ibm.com [9.149.37.213]) by b06cxnps4075.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q9B7i1Xi58130590 for ; Thu, 11 Oct 2012 07:44:01 GMT Received: from d06av03.portsmouth.uk.ibm.com (localhost.localdomain [127.0.0.1]) by d06av03.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q9B7i7Ci024917 for ; Thu, 11 Oct 2012 01:44:07 -0600 Date: Thu, 11 Oct 2012 09:44:05 +0200 From: Martin Schwidefsky Subject: Re: [PATCH] mm: Fix XFS oops due to dirty pages without buffers on s390 Message-ID: <20121011094405.1c5990c9@mschwide> In-Reply-To: <20121010215600.GX23644@dastard> References: <1349108796-32161-1-git-send-email-jack@suse.cz> <20121009162107.GE15790@quack.suse.cz> <20121010215600.GX23644@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Chinner Cc: Hugh Dickins , Jan Kara , linux-mm@kvack.org, LKML , xfs@oss.sgi.com, Mel Gorman , linux-s390@vger.kernel.org On Thu, 11 Oct 2012 08:56:00 +1100 Dave Chinner wrote: > 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.... Our internal builds indeed have CONFIG_XFS_DEBUG=n, I'll change that and watch for the fallout. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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