From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755116AbZBCNlY (ORCPT ); Tue, 3 Feb 2009 08:41:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753325AbZBCNlO (ORCPT ); Tue, 3 Feb 2009 08:41:14 -0500 Received: from e35.co.us.ibm.com ([32.97.110.153]:60139 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752919AbZBCNlM (ORCPT ); Tue, 3 Feb 2009 08:41:12 -0500 Subject: Re: [BUGFIX take 2] [PATCH] write-back: fix nr_to_write counter From: Dave Kleikamp To: dedekind@infradead.org Cc: torvalds@linux-foundation.org, Andrew Morton , Nick Piggin , Linux Kernel Mailing List , linux-fsdevel In-Reply-To: <1233655712.24809.101.camel@localhost.localdomain> References: <1233655712.24809.101.camel@localhost.localdomain> Content-Type: text/plain Date: Tue, 03 Feb 2009 07:41:01 -0600 Message-Id: <1233668461.30906.4.camel@norville.austin.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.24.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-02-03 at 12:08 +0200, Artem Bityutskiy wrote: > 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 > } Actually quoting a patch in the description in this manner will make the patch fail to apply (or fail to apply correctly). If you must quote the patch, you should probably prepend ">" or something. > 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 des 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..13a2b8e 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, bud 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 > > -- David Kleikamp IBM Linux Technology Center