From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx206.postini.com [74.125.245.206]) by kanga.kvack.org (Postfix) with SMTP id 12B3C6B002B for ; Mon, 8 Oct 2012 10:28:28 -0400 (EDT) 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-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <1349108796-32161-1-git-send-email-jack@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: linux-mm@kvack.org, LKML , xfs@oss.sgi.com, Martin Schwidefsky , linux-s390@vger.kernel.org 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, 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