From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754722Ab0KHXTm (ORCPT ); Mon, 8 Nov 2010 18:19:42 -0500 Received: from mga03.intel.com ([143.182.124.21]:42412 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754099Ab0KHXTi (ORCPT ); Mon, 8 Nov 2010 18:19:38 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.59,171,1288594800"; d="scan'208";a="346159512" Message-Id: <20101108231726.993880740@intel.com> User-Agent: quilt/0.48-1 Date: Tue, 09 Nov 2010 07:09:19 +0800 From: Wu Fengguang To: Andrew Morton cc: Jan Kara , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Wu Fengguang cc: Christoph Hellwig , Jan Engelhardt Cc: LKML Subject: [PATCH 3/5] writeback: stop background/kupdate works from livelocking other works References: <20101108230916.826791396@intel.com> Content-Disposition: inline; filename=0002-mm-Stop-background-writeback-if-there-is-other-work-.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jan Kara Background writeback are easily livelockable (from a definition of their target). This is inconvenient because it can make sync(1) stall forever waiting on its queued work to be finished. Generally, when a flusher thread has some work queued, someone submitted the work to achieve a goal more specific than what background writeback does. So it makes sense to give it a priority over a generic page cleaning. Thus we interrupt background writeback if there is some other work to do. We return to the background writeback after completing all the queued work. Signed-off-by: Jan Kara Signed-off-by: Wu Fengguang --- fs/fs-writeback.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- linux-next.orig/fs/fs-writeback.c 2010-11-07 21:56:42.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2010-11-07 22:00:51.000000000 +0800 @@ -651,6 +651,15 @@ static long wb_writeback(struct bdi_writ break; /* + * Background writeout and kupdate-style writeback are + * easily livelockable. Stop them if there is other work + * to do so that e.g. sync can proceed. + */ + if ((work->for_background || work->for_kupdate) && + !list_empty(&wb->bdi->work_list)) + break; + + /* * For background writeout, stop when we are below the * background dirty threshold */