From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752371AbcBOITz (ORCPT ); Mon, 15 Feb 2016 03:19:55 -0500 Received: from mail-wm0-f52.google.com ([74.125.82.52]:37545 "EHLO mail-wm0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752223AbcBOITx (ORCPT ); Mon, 15 Feb 2016 03:19:53 -0500 Subject: Re: [PATCH 1/4] block: bio: introduce helpers to get the 1st and last bvec To: Ming Lei , Jens Axboe , linux-kernel@vger.kernel.org References: <1455519687-23873-1-git-send-email-ming.lei@canonical.com> <1455519687-23873-2-git-send-email-ming.lei@canonical.com> Cc: linux-block@vger.kernel.org, Christoph Hellwig , stable@vger.kernel.org From: Sagi Grimberg Message-ID: <56C18A25.50803@dev.mellanox.co.il> Date: Mon, 15 Feb 2016 10:19:49 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <1455519687-23873-2-git-send-email-ming.lei@canonical.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > +/* > + * bio_get_last_bvec() is introduced to get the last bvec of one > + * bio for bio_will_gap(). > + * > + * TODO: make it more efficient. > + */ > +static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) > +{ > + struct bvec_iter iter; > + > + bio_for_each_segment(*bv, bio, iter) > + if (bv->bv_len == iter.bi_size) > + break; > +} This helper is used for each req/bio once or more. I'd say it's critical to make it efficient and not settle for a quick bail for drivers that don't have a virt_boundary like you did in patch #2. However, given that it's a regression bug fix I'm not sure it's the best idea to add logic here.