From mboxrd@z Thu Jan 1 00:00:00 1970 From: Artem Bityutskiy Subject: [BUGFIX re-send] [PATCH] write-back: fix nr_to_write counter Date: Tue, 03 Feb 2009 10:42:22 +0200 Message-ID: <1233650542.24809.54.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: npiggin@suse.de, LKML To: linux-fsdevel Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Hi, commit 05fe478dd04e02fa230c305ab9b5616669821dd3 Author: Nick Piggin Date: Tue Jan 6 14:39:08 2009 -0800 mm: write_cache_pages integrity fix broke wbc->nr_to_write handling. Here is the fix. I'm not 100% sure I got things right, because I am far not expert in th= e area. Please, review it. The patch fixes my UBIFS issues, which are caused by the fact that wbc->nr_to_write is not updated. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =46rom: Artem Bityutskiy Date: Mon, 2 Feb 2009 18:33:49 +0200 Subject: [PATCH] write-back: fix nr_to_write counter Commit 05fe478dd04e02fa230c305ab9b5616669821dd3 broke @wbc->nr_to_write= =2E 'write_cache_pages()' changes it in the loop, but restores the original value from @nr_to_write at the end, because of this code: if (!wbc->no_nrwrite_index_update) { if (wbc->range_cyclic || (range_whole && nr_to_write > = 0)) mapping->writeback_index =3D done_index; wbc->nr_to_write =3D nr_to_write; } Well, in case of @wbc->no_nrwrite_index_update !=3D 0, we do change wbc->nr_to_write, while we should not. This patch fixes this behavior. Also, I think wbc->nr_to_write should be changed in all cases, not only when wbc->sync_mode =3D=3D WB_SYNC_NONE. Also, I add a comment explaining why we do not stop writing back. Signed-off-by: Artem Bityutskiy --- 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)