From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: [BUGFIX take 2] [PATCH] write-back: fix nr_to_write counter Date: Tue, 03 Feb 2009 12:08:32 +0200 Message-ID: <1233655712.24809.101.camel@localhost.localdomain> Reply-To: dedekind@infradead.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Andrew Morton , Nick Piggin , Linux Kernel Mailing List , linux-fsdevel To: torvalds@linux-foundation.org Return-path: Received: from smtp.nokia.com ([192.100.122.233]:59273 "EHLO mgw-mx06.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751933AbZBCKIx (ORCPT ); Tue, 3 Feb 2009 05:08:53 -0500 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: =46rom: 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 <=3D 0) - done =3D 1; + if (wbc->sync_mode =3D=3D WB_SYNC_NONE) { + if (--wbc->nr_to_write <=3D 0) + done =3D 1; + } if (wbc->nonblocking && bdi_write_congested(bdi= )) { wbc->encountered_congestion =3D 1; done =3D 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 =3D=3D WB_SYNC_N= ONE 3. If synced nr_to_write pages, stop only if if wbc->sync_mode =3D=3D 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 i= n _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: } } =20 - if (wbc->sync_mode =3D=3D WB_SYNC_NONE) { - wbc->nr_to_write--; - if (wbc->nr_to_write <=3D 0) { - done =3D 1; - break; - } + if (nr_to_write > 0) + nr_to_write--; + else if (wbc->sync_mode =3D=3D 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 =3D 1; + break; } + if (wbc->nonblocking && bdi_write_congested(bdi)) { wbc->encountered_congestion =3D 1; done =3D 1; --=20 1.6.0.6 --=20 Best regards, Artem Bityutskiy (=D0=91=D0=B8=D1=82=D1=8E=D1=86=D0=BA=D0=B8=D0=B9 =D0=90= =D1=80=D1=82=D1=91=D0=BC) -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html