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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 61AF5C433E3 for ; Mon, 22 Mar 2021 11:24:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DD456191A for ; Mon, 22 Mar 2021 11:24:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230010AbhCVLXf (ORCPT ); Mon, 22 Mar 2021 07:23:35 -0400 Received: from mx2.suse.de ([195.135.220.15]:34826 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229508AbhCVLXV (ORCPT ); Mon, 22 Mar 2021 07:23:21 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id C6B00AD4A; Mon, 22 Mar 2021 11:23:19 +0000 (UTC) Subject: Re: [PATCH 1/2] blk-mq: add a blk_mq_submit_bio_direct API To: Christoph Hellwig , Sagi Grimberg , Keith Busch , Jens Axboe Cc: Chao Leng , linux-block@vger.kernel.org, linux-nvme@lists.infradead.org References: <20210322073726.788347-1-hch@lst.de> <20210322073726.788347-2-hch@lst.de> From: Hannes Reinecke Message-ID: Date: Mon, 22 Mar 2021 12:23:19 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210322073726.788347-2-hch@lst.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 3/22/21 8:37 AM, Christoph Hellwig wrote: > This adds (back) and API for simple stacking drivers to submit a bio to > blk-mq queue. The prime aim is to avoid blocking on the queue freeze > percpu ref, as a multipath driver really does not want to get blocked > on that when an underlying device is undergoing error recovery. It also > happens to optimize away the small overhead of the curren->bio_list based > recursion avoidance. > > Signed-off-by: Christoph Hellwig > --- > block/blk-core.c | 2 +- > block/blk-mq.c | 37 +++++++++++++++++++++++++++++++++++++ > block/blk.h | 1 + > include/linux/blk-mq.h | 1 + > 4 files changed, 40 insertions(+), 1 deletion(-) > > diff --git a/block/blk-core.c b/block/blk-core.c > index fc60ff20849738..4344f3c9058282 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -792,7 +792,7 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q, > return BLK_STS_OK; > } > > -static noinline_for_stack bool submit_bio_checks(struct bio *bio) > +noinline_for_stack bool submit_bio_checks(struct bio *bio) > { > struct block_device *bdev = bio->bi_bdev; > struct request_queue *q = bdev->bd_disk->queue; > diff --git a/block/blk-mq.c b/block/blk-mq.c > index d4d7c1caa43966..4ff85692843b49 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2286,6 +2286,43 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio) > return BLK_QC_T_NONE; > } > > +/** > + * blk_mq_submit_bio_direct - hand a bio directly to the driver for I/O > + * @bio: The bio describing the location in memory and on the device. > + * > + * This function behaves similar to submit_bio_noacct(), but does never waits > + * for the queue to be unfreozen, instead it return false and lets the caller > + * deal with the fallout. It also does not protect against recursion and thus > + * must only be used if the called driver is known to be blk-mq based. > + */ > +bool blk_mq_submit_bio_direct(struct bio *bio, blk_qc_t *qc) > +{ > + struct gendisk *disk = bio->bi_bdev->bd_disk; > + struct request_queue *q = disk->queue; > + > + if (WARN_ON_ONCE(!current->bio_list) || > + WARN_ON_ONCE(disk->fops->submit_bio)) { > + bio_io_error(bio); > + goto fail; > + } > + if (!submit_bio_checks(bio)) > + goto fail; > + > + if (unlikely(blk_queue_enter(q, BLK_MQ_REQ_NOWAIT))) > + return false; > + if (!blk_crypto_bio_prep(&bio)) > + goto fail_queue_exit; > + *qc = blk_mq_submit_bio(bio); > + return true; > + > +fail_queue_exit: > + blk_queue_exit(disk->queue); > +fail: > + *qc = BLK_QC_T_NONE; > + return true; > +} > +EXPORT_SYMBOL_GPL(blk_mq_submit_bio_direct); > + > void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, > unsigned int hctx_idx) > { > diff --git a/block/blk.h b/block/blk.h > index 3b53e44b967e4e..c4c66b2a9ffb19 100644 > --- a/block/blk.h > +++ b/block/blk.h > @@ -221,6 +221,7 @@ ssize_t part_timeout_show(struct device *, struct device_attribute *, char *); > ssize_t part_timeout_store(struct device *, struct device_attribute *, > const char *, size_t); > > +bool submit_bio_checks(struct bio *bio); > void __blk_queue_split(struct bio **bio, unsigned int *nr_segs); > int ll_back_merge_fn(struct request *req, struct bio *bio, > unsigned int nr_segs); > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 2c473c9b899089..6804f397106ada 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); > +bool blk_mq_submit_bio_direct(struct bio *bio, blk_qc_t *qc); > void blk_mq_hctx_set_fq_lock_class(struct blk_mq_hw_ctx *hctx, > struct lock_class_key *key); > > Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Felix Imendörffer