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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 E794AC41518 for ; Wed, 10 Mar 2021 22:02:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C018964FAB for ; Wed, 10 Mar 2021 22:02:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233882AbhCJWBl (ORCPT ); Wed, 10 Mar 2021 17:01:41 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:28227 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233809AbhCJWBa (ORCPT ); Wed, 10 Mar 2021 17:01:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615413690; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5MWUWHikDuHFwOWnHcZ5hNjQN8vsP5I1JtfVKI5geTI=; b=hbG0ZIZLnfbqyn+QpcXTTHcTPkmx23gUNVZ+kn9A2KFeZPhMdUHHME2SzMkx8SocPywsCf gFse3Cw+1G1vjiQ+pF/OUEZ5H8URMAv3aDmnLWx6YM1MsmGuOJ9A3rD00B7GRzcQyHcO8d Ek3+UvxfRdraq3kMfmf9oBd/lIGZ7zg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-503-nlwRBGokMuWFHFfw5E1x_g-1; Wed, 10 Mar 2021 17:01:28 -0500 X-MC-Unique: nlwRBGokMuWFHFfw5E1x_g-1 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 mimecast-mx01.redhat.com (Postfix) with ESMTPS id D73F41019623; Wed, 10 Mar 2021 22:01:26 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4CF1D19C48; Wed, 10 Mar 2021 22:01:23 +0000 (UTC) Date: Wed, 10 Mar 2021 17:01:22 -0500 From: Mike Snitzer To: Jeffle Xu Cc: axboe@kernel.dk, io-uring@vger.kernel.org, dm-devel@redhat.com, linux-block@vger.kernel.org, mpatocka@redhat.com, caspar@linux.alibaba.com, joseph.qi@linux.alibaba.com Subject: Re: [PATCH v5 03/12] block: add poll method to support bio-based IO polling Message-ID: <20210310220122.GB23410@redhat.com> References: <20210303115740.127001-1-jefflexu@linux.alibaba.com> <20210303115740.127001-4-jefflexu@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210303115740.127001-4-jefflexu@linux.alibaba.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, Mar 03 2021 at 6:57am -0500, Jeffle Xu wrote: > ->poll_fn was introduced in commit ea435e1b9392 ("block: add a poll_fn > callback to struct request_queue") to support bio-based queues such as > nvme multipath, but was later removed in commit 529262d56dbe ("block: > remove ->poll_fn"). > > Given commit c62b37d96b6e ("block: move ->make_request_fn to struct > block_device_operations") restore the possibility of bio-based IO > polling support by adding an ->poll method to gendisk->fops. > > Make blk_mq_poll() specific to blk-mq, while blk_bio_poll() is > originally a copy from blk_mq_poll(), and is specific to bio-based > polling. Currently hybrid polling is not supported by bio-based polling. > > Signed-off-by: Jeffle Xu > --- > block/blk-core.c | 58 ++++++++++++++++++++++++++++++++++++++++++ > block/blk-mq.c | 22 +--------------- > include/linux/blk-mq.h | 1 + > include/linux/blkdev.h | 1 + > 4 files changed, 61 insertions(+), 21 deletions(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index fc60ff208497..6d7d53030d7c 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1119,6 +1119,64 @@ blk_qc_t submit_bio(struct bio *bio) > } > EXPORT_SYMBOL(submit_bio); > > + Minor nit: Extra empty new line here? ^ Otherwise, looks good (I like the end result of blk-mq and bio-based polling being decoupled like hch suggested). Reviewed-by: Mike Snitzer > +static int blk_bio_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > +{ > + long state; > + struct gendisk *disk = queue_to_disk(q); > + > + state = current->state; > + do { > + int ret; > + > + ret = disk->fops->poll(q, cookie); > + if (ret > 0) { > + __set_current_state(TASK_RUNNING); > + return ret; > + } > + > + if (signal_pending_state(state, current)) > + __set_current_state(TASK_RUNNING); > + > + if (current->state == TASK_RUNNING) > + return 1; > + if (ret < 0 || !spin) > + break; > + cpu_relax(); > + } while (!need_resched()); > + > + __set_current_state(TASK_RUNNING); > + return 0; > +} > + > +/** > + * blk_poll - poll for IO completions > + * @q: the queue > + * @cookie: cookie passed back at IO submission time > + * @spin: whether to spin for completions > + * > + * Description: > + * Poll for completions on the passed in queue. Returns number of > + * completed entries found. If @spin is true, then blk_poll will continue > + * looping until at least one completion is found, unless the task is > + * otherwise marked running (or we need to reschedule). > + */ > +int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > +{ > + if (!blk_qc_t_valid(cookie) || > + !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > + return 0; > + > + if (current->plug) > + blk_flush_plug_list(current->plug, false); > + > + if (queue_is_mq(q)) > + return blk_mq_poll(q, cookie, spin); > + else > + return blk_bio_poll(q, cookie, spin); > +} > +EXPORT_SYMBOL_GPL(blk_poll); > + > /** > * blk_cloned_rq_check_limits - Helper function to check a cloned request > * for the new queue limits > diff --git a/block/blk-mq.c b/block/blk-mq.c > index d4d7c1caa439..214fa30b460a 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -3852,30 +3852,11 @@ static bool blk_mq_poll_hybrid(struct request_queue *q, > return blk_mq_poll_hybrid_sleep(q, rq); > } > > -/** > - * blk_poll - poll for IO completions > - * @q: the queue > - * @cookie: cookie passed back at IO submission time > - * @spin: whether to spin for completions > - * > - * Description: > - * Poll for completions on the passed in queue. Returns number of > - * completed entries found. If @spin is true, then blk_poll will continue > - * looping until at least one completion is found, unless the task is > - * otherwise marked running (or we need to reschedule). > - */ > -int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > { > struct blk_mq_hw_ctx *hctx; > long state; > > - if (!blk_qc_t_valid(cookie) || > - !test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) > - return 0; > - > - if (current->plug) > - blk_flush_plug_list(current->plug, false); > - > hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)]; > > /* > @@ -3917,7 +3898,6 @@ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) > __set_current_state(TASK_RUNNING); > return 0; > } > -EXPORT_SYMBOL_GPL(blk_poll); > > unsigned int blk_mq_rq_cpu(struct request *rq) > { > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 2c473c9b8990..6a7b693b9917 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -615,6 +615,7 @@ static inline void blk_rq_bio_prep(struct request *rq, struct bio *bio, > } > > blk_qc_t blk_mq_submit_bio(struct bio *bio); > +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, bool spin); > void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx, > struct lock_class_key *key); > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index b81a9fe015ab..9dc83c30e7bc 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1866,6 +1866,7 @@ static inline void blk_ksm_unregister(struct request_queue *q) { } > > struct block_device_operations { > blk_qc_t (*submit_bio) (struct bio *bio); > + int (*poll)(struct request_queue *q, blk_qc_t cookie); > int (*open) (struct block_device *, fmode_t); > void (*release) (struct gendisk *, fmode_t); > int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int); > -- > 2.27.0 >