From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759929AbZBNBFi (ORCPT ); Fri, 13 Feb 2009 20:05:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755656AbZBNBBe (ORCPT ); Fri, 13 Feb 2009 20:01:34 -0500 Received: from kroah.org ([198.145.64.141]:39512 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755367AbZBNBBd (ORCPT ); Fri, 13 Feb 2009 20:01:33 -0500 Date: Fri, 13 Feb 2009 16:58:25 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Artem Bityutskiy , Nick Piggin Subject: [patch 11/47] write-back: fix nr_to_write counter Message-ID: <20090214005825.GL11282@kroah.com> References: <20090214005130.617401075@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="write-back-fix-nr_to_write-counter.patch" In-Reply-To: <20090214005726.GA11282@kroah.com> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.27-stable review patch. If anyone has any objections, please let us know. ------------------ From: Artem Bityutskiy commit dcf6a79dda5cc2a2bec183e50d829030c0972aaa upstream. Commit 05fe478dd04e02fa230c305ab9b5616669821dd3 introduced some @wbc->nr_to_write breakage. It made the following changes: 1. Decrement wbc->nr_to_write instead of nr_to_write 2. Decrement wbc->nr_to_write _only_ if wbc->sync_mode == WB_SYNC_NONE 3. If synced nr_to_write pages, stop only if if wbc->sync_mode == WB_SYNC_NONE, otherwise keep going. However, according to the commit message, the intention was to only make change 3. Change 1 is a bug. Change 2 does not seem to be necessary, and it breaks UBIFS expectations, so if needed, it should be done separately later. And change 2 does not seem to be documented in the commit message. This patch does the following: 1. Undo changes 1 and 2 2. Add a comment explaining change 3 (it very useful to have comments in _code_, not only in the commit). Signed-off-by: Artem Bityutskiy Acked-by: Nick Piggin Cc: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/page-writeback.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -985,13 +985,22 @@ continue_unlock: } } - if (wbc->sync_mode == WB_SYNC_NONE) { + if (wbc->nr_to_write > 0) wbc->nr_to_write--; - if (wbc->nr_to_write <= 0) { - done = 1; - break; - } + else if (wbc->sync_mode == WB_SYNC_NONE) { + /* + * We stop writing back only if we are not + * doing integrity sync. In case of integrity + * sync we have to keep going because someone + * may be concurrently dirtying pages, and we + * might have synced a lot of newly appeared + * dirty pages, but have not synced all of the + * old dirty pages. + */ + done = 1; + break; } + if (wbc->nonblocking && bdi_write_congested(bdi)) { wbc->encountered_congestion = 1; done = 1;