From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754423AbZBCPpv (ORCPT ); Tue, 3 Feb 2009 10:45:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752042AbZBCPpk (ORCPT ); Tue, 3 Feb 2009 10:45:40 -0500 Received: from smtp.nokia.com ([192.100.105.134]:65429 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbZBCPpk (ORCPT ); Tue, 3 Feb 2009 10:45:40 -0500 Subject: [BUGFIX take 4] [PATCH] write-back: fix nr_to_write counter From: Artem Bityutskiy Reply-To: dedekind@infradead.org To: torvalds Cc: Andrew Morton , Nick Piggin , Linux Kernel Mailing List , linux-fsdevel In-Reply-To: <49885ABD.2010600@hp.com> References: <1233655712.24809.101.camel@localhost.localdomain> <1233668461.30906.4.camel@norville.austin.ibm.com> <1233672349.5138.12.camel@localhost.localdomain> <49885ABD.2010600@hp.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 03 Feb 2009 17:44:59 +0200 Message-Id: <1233675899.5138.19.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.3 (2.24.3-1.fc10) Content-Transfer-Encoding: 8bit X-OriginalArrivalTime: 03 Feb 2009 15:44:55.0307 (UTC) FILETIME=[5C524DB0:01C98616] X-Nokia-AV: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Fix spelling, pointed to by jim owens] From: Artem Bityutskiy Date: Mon, 2 Feb 2009 18:33:49 +0200 Subject: [PATCH] write-back: fix nr_to_write counter Commit 05fe478dd04e02fa230c305ab9b5616669821dd3 introduced some @wbc->nr_to_write breakage. Here is the change from the commit: >--- a/mm/page-writeback.c >+++ b/mm/page-writeback.c >@@ -963,8 +963,10 @@ retry: > } > } > > if (--nr_to_write <= 0) > done = 1; > if (wbc->sync_mode == WB_SYNC_NONE) { > if (--wbc->nr_to_write <= 0) > done = 1; > } > if (wbc->nonblocking && bdi_write_congested(bdi)) { > wbc->encountered_congestion = 1; > done = 1 > } It makes 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 --- mm/page-writeback.c | 21 +++++++++++++++------ 1 files changed, 15 insertions(+), 6 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index b493db7..dc32dae 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1051,13 +1051,22 @@ continue_unlock: } } - if (wbc->sync_mode == WB_SYNC_NONE) { - wbc->nr_to_write--; - if (wbc->nr_to_write <= 0) { - done = 1; - break; - } + 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 (wbc->nonblocking && bdi_write_congested(bdi)) { wbc->encountered_congestion = 1; done = 1; -- 1.6.0.6 -- Best regards, Artem Bityutskiy (Битюцкий Артём)