From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q98EQxCV079811 for ; Mon, 8 Oct 2012 09:26:59 -0500 Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by cuda.sgi.com with ESMTP id u4NujWUHx7LUhmkd (version=TLSv1 cipher=AES256-SHA bits=256 verify=NO) for ; Mon, 08 Oct 2012 07:28:28 -0700 (PDT) Date: Mon, 8 Oct 2012 15:28:23 +0100 From: Mel Gorman 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-Disposition: inline In-Reply-To: <1349108796-32161-1-git-send-email-jack@suse.cz> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Jan Kara Cc: Martin Schwidefsky , linux-mm@kvack.org, linux-s390@vger.kernel.org, LKML , xfs@oss.sgi.com 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 _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs