From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754152AbZBJGYh (ORCPT ); Tue, 10 Feb 2009 01:24:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751837AbZBJGY3 (ORCPT ); Tue, 10 Feb 2009 01:24:29 -0500 Received: from mailhost-h1-m1.nerim-networks.com ([78.40.49.162]:54497 "EHLO smtp-delay2.nerim.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751668AbZBJGY2 (ORCPT ); Tue, 10 Feb 2009 01:24:28 -0500 Date: Tue, 10 Feb 2009 07:22:49 +0100 From: Damien Wyart To: Nick Piggin Cc: Andrew Morton , Federico Cuello , linux-kernel@vger.kernel.org, Artem Bityutskiy Subject: Re: [PATCH] write-back: fix break condition Message-ID: <20090210062249.GA5224@localhost.localdomain> References: <1233977610-8919-1-git-send-email-fedux@lugmen.org.ar> <20090209152140.aa3f50aa.akpm@linux-foundation.org> <20090210003452.GA26143@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090210003452.GA26143@wotan.suse.de> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Nick Piggin [2009-02-10 01:34]: > On Mon, Feb 09, 2009 at 03:21:40PM -0800, Andrew Morton wrote: > > Thanks, but please do cc the people who were involved with a patch when > > you find a problem with it! > > On Sat, 7 Feb 2009 01:33:30 -0200 > > Federico Cuello wrote: > > > Commit 673353723e7a6550625fb719059c5f31cfaecd18 fixed nr_to_write > > > counter, but didn't set the break condition properly. > > It's actually commit dcf6a79dda5cc2a2bec183e50d829030c0972aaa > > ("write-back: fix nr_to_write counter"). > > > If nr_to_write == 0 after being decremented it will loop one more time > > > before setting done = 1 and breaking the loop. > > We prefer that patches include the author's Signed-off-by:, as per > > Documentation/SubmittingPatches, please. > > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > > > index bb5fa2b..9e2ae50 100644 > > > --- a/mm/page-writeback.c > > > +++ b/mm/page-writeback.c > > > @@ -981,20 +981,21 @@ continue_unlock: > > > } > > > } > > > - if (nr_to_write > 0) > > > + if (nr_to_write > 0) { > > > nr_to_write--; > > > - 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 (nr_to_write == 0 && 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)) { > > Artem, Nick, please check? > Yes, this looks OK by me. > Acked-by: Nick Piggin Shouldn't this go to stable 2.6.28, too ? They have not been in Cc for now. I think the problem was at first detected in 2.6.28.X, but it is not yet sure if it is solved or if this interacts with some ext4 problems. -- Damien Wyart