From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753880Ab2G3Ai7 (ORCPT ); Sun, 29 Jul 2012 20:38:59 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:34732 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753747Ab2G3Ai5 (ORCPT ); Sun, 29 Jul 2012 20:38:57 -0400 Date: Mon, 30 Jul 2012 08:40:11 +0800 From: majianpeng To: "Jeff Moyer" Cc: viro , "Neil Brown" , linux-fsdevel , linux-kernel , linux-raid Subject: Re: Re: [RFC PATCH] fs/direct-io.c: Set bi_rw when alloc bio. References: <201207271602081096921@gmail.com>, X-Priority: 3 X-Has-Attach: no X-Mailer: Foxmail 7.0.1.91[en] Mime-Version: 1.0 Message-ID: <201207300840005466080@gmail.com> Content-Type: text/plain; charset="gb2312" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id q6U0d3Oq002230 On 2012-07-27 22:21 Jeff Moyer Wrote: >majianpeng writes: > >> When exec bio_alloc, the bi_rw is zero.But after calling bio_add_page, >> it will use bi_rw. >> Fox example, in functiion __bio_add_page,it will call merge_bvec_fn(). >> The merge_bvec_fn of raid456 will use the bi_rw to judge the merge. >>>> if ((bvm->bi_rw & 1) == WRITE) >>>> return biovec->bv_len; /* always allow writes to be mergeable */ >> >> Signed-off-by: Jianpeng Ma > >Good catch. How did you find this? Did you experience data corruption >as a result of this oversight, reduced performance due to missed merge >opportunities, or did you just notice it in reviewing the code? > >Reviewed-by: Jeff Moyer > Sorry for late to reply. When i analysed the performance of raid5, i found this bug. >> >> There are many place like this in kernel.If you think this patch ok, i will correct those. >> --- >> fs/direct-io.c | 1 + >> 1 files changed, 1 insertions(+), 0 deletions(-) >> >> diff --git a/fs/direct-io.c b/fs/direct-io.c >> index 1faf4cb..77f0bbf 100644 >> --- a/fs/direct-io.c >> +++ b/fs/direct-io.c >> @@ -349,6 +349,7 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, >> >> bio->bi_bdev = bdev; >> bio->bi_sector = first_sector; >> + bio->bi_rw = dio->rw; >> if (dio->is_async) >> bio->bi_end_io = dio_bio_end_aio; >> else{.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I