Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753326Ab2JHO2f (ORCPT ); Mon, 8 Oct 2012 10:28:35 -0400 Received: from cantor2.suse.de ([195.135.220.15]:58413 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753166Ab2JHO21 (ORCPT ); Mon, 8 Oct 2012 10:28:27 -0400 Date: Mon, 8 Oct 2012 15:28:23 +0100 From: Mel Gorman To: Jan Kara Cc: linux-mm@kvack.org, LKML , xfs@oss.sgi.com, Martin Schwidefsky , linux-s390@vger.kernel.org Subject: Re: [PATCH] mm: Fix XFS oops due to dirty pages without buffers on s390 Message-ID: <20121008142823.GL29125@suse.de> References: <1349108796-32161-1-git-send-email-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1349108796-32161-1-git-send-email-jack@suse.cz> 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: 1828 Lines: 39 On Mon, Oct 01, 2012 at 06:26:36PM +0200, 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(). > > Similar problem can also happen when zero_user_segment() call from > xfs_vm_writepage() (or block_write_full_page() for that matter) set the > hardware dirty bit during writeback, later buffers get freed, and then page > unmapped. > > Fix the issue by ignoring s390 HW dirty bit for page cache pages in > page_mkclean() and page_remove_rmap(). This is safe because when a page gets > marked as writeable in PTE it is also marked dirty in do_wp_page() or > do_page_fault(). When the dirty bit is cleared by clear_page_dirty_for_io(), > the page gets writeprotected in page_mkclean(). So pagecache page is writeable > if and only if it is dirty. > > CC: Martin Schwidefsky > CC: Mel Gorman > CC: linux-s390@vger.kernel.org > Signed-off-by: Jan Kara Acked-by: Mel Gorman -- Mel Gorman SUSE Labs -- 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/