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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=no 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 96889C433E1 for ; Mon, 17 Aug 2020 12:10:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77D4D2072E for ; Mon, 17 Aug 2020 12:10:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727880AbgHQMKF (ORCPT ); Mon, 17 Aug 2020 08:10:05 -0400 Received: from out30-57.freemail.mail.aliyun.com ([115.124.30.57]:48839 "EHLO out30-57.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726265AbgHQMKF (ORCPT ); Mon, 17 Aug 2020 08:10:05 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R801e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04427;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U62Iq6A_1597666202; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0U62Iq6A_1597666202) by smtp.aliyun-inc.com(127.0.0.1); Mon, 17 Aug 2020 20:10:02 +0800 Date: Mon, 17 Aug 2020 20:10:02 +0800 From: Baolin Wang To: Christoph Hellwig Cc: axboe@kernel.dk, ming.lei@redhat.com, baolin.wang7@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RESEND 3/5] block: Add a new helper to attempt to merge a bio Message-ID: <20200817121002.GB79836@VM20190228-100.tbsite.net> Reply-To: Baolin Wang References: <5b932aa51fc2b46c381d7b83d591a6ddbf05b199.1597637287.git.baolin.wang@linux.alibaba.com> <20200817062634.GC12248@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200817062634.GC12248@lst.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Aug 17, 2020 at 08:26:34AM +0200, Christoph Hellwig wrote: > On Mon, Aug 17, 2020 at 12:09:17PM +0800, Baolin Wang wrote: > > There are lots of duplicated code when trying to merge a bio from > > plug list and sw queue, we can introduce a new helper to attempt > > to merge a bio, which can simplify the blk_mq_bio_list_merge() > > and blk_attempt_plug_merge(). > > Looks sensible, but two comments: > > > +enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, > > + struct request *rq, > > + struct bio *bio, > > + unsigned int nr_segs) > > +{ > > + bool merged = false; > > + > > + if (!blk_rq_merge_ok(rq, bio)) > > + return BIO_MERGE_NONE; > > + > > + switch (blk_try_merge(rq, bio)) { > > + case ELEVATOR_BACK_MERGE: > > + merged = bio_attempt_back_merge(rq, bio, nr_segs); > > + break; > > + case ELEVATOR_FRONT_MERGE: > > + merged = bio_attempt_front_merge(rq, bio, nr_segs); > > + break; > > + case ELEVATOR_DISCARD_MERGE: > > + merged = bio_attempt_discard_merge(q, rq, bio); > > + break; > > Can't we also switch the bio_attempt_*merge helpers to return > enum bio_merge_status to simplify this a bit? Yes, will do. > > Also I think these helpers can be marked static now, although I didn't > actually apply your series, so I might have missed something. Cause this function will be used by blk_mq_bio_list_merge() in blk-mq-sched.c, it should be exported. > > > +++ b/block/blk-mq-sched.c > > @@ -391,31 +391,17 @@ bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list, > > { > > struct request *rq; > > int checked = 8; > > + enum bio_merge_status merge; > > > > list_for_each_entry_reverse(rq, list, queuelist) { > > - bool merged = false; > > - > > if (!checked--) > > break; > > > > + merge = blk_attempt_bio_merge(q, rq, bio, nr_segs); > > + if (merge == BIO_MERGE_NONE) > > continue; > > > > + return merge == BIO_MERGE_OK ? true: false; > > Maybe write this a little more explicit: > > switch (blk_attempt_bio_merge(q, rq, bio, nr_segs)) { > case BIO_MERGE_NONE: > continue: > case BIO_MERGE_OK: > return true; > case BIO_MERGE_FAILED: > return false; > } Sure. > > > enum elv_merge blk_try_merge(struct request *rq, struct bio *bio); > > > > +enum bio_merge_status { > > + BIO_MERGE_OK, > > + BIO_MERGE_NONE, > > + BIO_MERGE_FAILED, > > +}; > > + > > +enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, > > + struct request *rq, struct bio *bio, unsigned int nr_segs); > > + > > int blk_dev_init(void); > > > > /* > > -- > > 1.8.3.1 > ---end quoted text---