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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,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 D6C77C43441 for ; Mon, 19 Nov 2018 09:07:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F9C120817 for ; Mon, 19 Nov 2018 09:07:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F9C120817 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S1727175AbeKSTaN (ORCPT ); Mon, 19 Nov 2018 14:30:13 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54862 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726784AbeKSTaM (ORCPT ); Mon, 19 Nov 2018 14:30:12 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 42C3C3082A44; Mon, 19 Nov 2018 09:07:12 +0000 (UTC) Received: from ming.t460p (ovpn-8-26.pek2.redhat.com [10.72.8.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2876819490; Mon, 19 Nov 2018 09:06:50 +0000 (UTC) Date: Mon, 19 Nov 2018 17:06:46 +0800 From: Ming Lei To: Omar Sandoval 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: <20181119090645.GN16736@ming.t460p> References: <20181115085306.9910-1-ming.lei@redhat.com> <20181115085306.9910-18-ming.lei@redhat.com> <20181116021140.GL23828@vader> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181116021140.GL23828@vader> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Mon, 19 Nov 2018 09:07:12 +0000 (UTC) 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 06:11:40PM -0800, Omar Sandoval wrote: > 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? Indeed, will update it in next version. Thanks, Ming