From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E06ADC43441 for ; Fri, 16 Nov 2018 02:11:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9D5DA214F1 for ; Fri, 16 Nov 2018 02:11:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="n43+lbPG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D5DA214F1 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=osandov.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389385AbeKPMWR (ORCPT ); Fri, 16 Nov 2018 07:22:17 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:41928 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389344AbeKPMWL (ORCPT ); Fri, 16 Nov 2018 07:22:11 -0500 Received: by mail-pg1-f196.google.com with SMTP id 70so9869013pgh.8 for ; Thu, 15 Nov 2018 18:11:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=fw5ouGiFQ8H9xz3HMkj3MnFIB/8cu61F/BMbgak5qVo=; b=n43+lbPGeaGJv5nZPtjvUNU9RusoWxagZQZh2JUDk5ifS+opUrvbJTg3olvONSVLlO ou399InyV5fk0IzEkS4W6JY1CeRJA2LGv9AFhCSbZDGmqqkyu1bFMLye+Gu9w7TA/jcR JWidLK99zYGxNywyV0gz2oqvqUlEmVZ2r6LNwyzVQjJI0+YbtAuhTzMTjwjO4lt3JYog B4wDn0wG+TFfi8ha98IRF+DhZW8KR8ngaM3/poOZkRLwt1d1PLOI9+YAmvFq6zyuBYCQ vLeObpH0P3IxYwopAfD5tyPJMCATwrFNrN4T08PDDJhGtKW5F0skZ1itK2BvlqWWCTwv haSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=fw5ouGiFQ8H9xz3HMkj3MnFIB/8cu61F/BMbgak5qVo=; b=KBC7Zagwsm3UgtooHNA78swHW1k3YT0nyhOBJfBeeCoppM9Cpl5fOOEecqeirXGYcj vcC5ug4tcTyR2FigRCQKRZm7U5QGZuASnKI/UQMVXYvSBw4u/C/kmYmWJnUCDgS124eq F/2r9ShiSeGYV6Z2bZhwsE1RrQ4sJJWppVdbHvY2eIyo1KkAOTwt73qDu6yxv758k3in WLRkbNb14KiTD3jOKrmnw4YanQaDy0wekjriXFq+3XpyDtGeRbN5tllej5IfuK7pVuYj wRYc6+aBYWYr9BVwImf/c8TaSJ5UegKEoWaEGYFWzsoNk6tGHeM5a/b9vX/I+7M2Cb6G O8vA== X-Gm-Message-State: AGRZ1gK5zEhgbl5V29cbHrFNVTBFTobf04OX3kDdmgx/goOkjGw+CZY4 yN2BF5eDJs+qgfI5SyUym8PxSg== X-Google-Smtp-Source: AJdET5c3E4A2RbqtCnQc5jwvauUMf7a8KgLxcBuVSjYMJIyJ0jhrItIEeS+5+KqwKpfdP8fzYx/xLQ== X-Received: by 2002:a63:224f:: with SMTP id t15mr8135068pgm.69.1542334302454; Thu, 15 Nov 2018 18:11:42 -0800 (PST) Received: from vader ([64.114.255.97]) by smtp.gmail.com with ESMTPSA id t3sm8847311pgv.31.2018.11.15.18.11.41 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 15 Nov 2018 18:11:41 -0800 (PST) Date: Thu, 15 Nov 2018 18:11:40 -0800 From: Omar Sandoval To: Ming Lei Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Kent Overstreet , Mike Snitzer , dm-devel@redhat.com, Alexander Viro , linux-fsdevel@vger.kernel.org, Shaohua Li , linux-raid@vger.kernel.org, linux-erofs@lists.ozlabs.org, David Sterba , linux-btrfs@vger.kernel.org, "Darrick J . Wong" , linux-xfs@vger.kernel.org, Gao Xiang , Christoph Hellwig , Theodore Ts'o , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com Subject: Re: [PATCH V10 17/19] block: don't use bio->bi_vcnt to figure out segment number Message-ID: <20181116021140.GL23828@vader> References: <20181115085306.9910-1-ming.lei@redhat.com> <20181115085306.9910-18-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181115085306.9910-18-ming.lei@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Thu, Nov 15, 2018 at 04:53:04PM +0800, Ming Lei wrote: > It is wrong to use bio->bi_vcnt to figure out how many segments > there are in the bio even though CLONED flag isn't set on this bio, > because this bio may be splitted or advanced. > > So always use bio_segments() in blk_recount_segments(), and it shouldn't > cause any performance loss now because the physical segment number is figured > out in blk_queue_split() and BIO_SEG_VALID is set meantime since > bdced438acd83ad83a6c ("block: setup bi_phys_segments after splitting"). > > Cc: Dave Chinner > Cc: Kent Overstreet > Fixes: 7f60dcaaf91 ("block: blk-merge: fix blk_recount_segments()") >From what I can tell, the problem was originally introduced by 76d8137a3113 ("blk-merge: recaculate segment if it isn't less than max segments") Is that right? > Cc: Mike Snitzer > Cc: dm-devel@redhat.com > Cc: Alexander Viro > Cc: linux-fsdevel@vger.kernel.org > Cc: Shaohua Li > Cc: linux-raid@vger.kernel.org > Cc: linux-erofs@lists.ozlabs.org > Cc: David Sterba > Cc: linux-btrfs@vger.kernel.org > Cc: Darrick J. Wong > Cc: linux-xfs@vger.kernel.org > Cc: Gao Xiang > Cc: Christoph Hellwig > Cc: Theodore Ts'o > Cc: linux-ext4@vger.kernel.org > Cc: Coly Li > Cc: linux-bcache@vger.kernel.org > Cc: Boaz Harrosh > Cc: Bob Peterson > Cc: cluster-devel@redhat.com > Signed-off-by: Ming Lei > --- > block/blk-merge.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index cb9f49bcfd36..153a659fde74 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -429,13 +429,7 @@ void blk_recalc_rq_segments(struct request *rq) > > void blk_recount_segments(struct request_queue *q, struct bio *bio) > { > - unsigned short seg_cnt; > - > - /* estimate segment number by bi_vcnt for non-cloned bio */ > - if (bio_flagged(bio, BIO_CLONED)) > - seg_cnt = bio_segments(bio); > - else > - seg_cnt = bio->bi_vcnt; > + unsigned short seg_cnt = bio_segments(bio); > > if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) && > (seg_cnt < queue_max_segments(q))) > -- > 2.9.5 >