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[73.241.217.19]) by smtp.gmail.com with ESMTPSA id s21sm11395838pfw.57.2021.06.08.16.07.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Jun 2021 16:07:17 -0700 (PDT) From: Bart Van Assche To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Jaegeuk Kim , Bart Van Assche , Damien Le Moal , Johannes Thumshirn , Himanshu Madhani , Hannes Reinecke , Ming Lei Subject: [PATCH 05/14] block/mq-deadline: Add several comments Date: Tue, 8 Jun 2021 16:06:54 -0700 Message-Id: <20210608230703.19510-6-bvanassche@acm.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210608230703.19510-1-bvanassche@acm.org> References: <20210608230703.19510-1-bvanassche@acm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Make the code easier to read by adding more comments. Reviewed-by: Damien Le Moal Reviewed-by: Johannes Thumshirn Reviewed-by: Himanshu Madhani Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Ming Lei Signed-off-by: Bart Van Assche --- block/mq-deadline.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 8eea2cbf2bf4..31418e9ce9e2 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -139,6 +139,9 @@ static void dd_request_merged(struct request_queue *q, struct request *req, } } +/* + * Callback function that is invoked after @next has been merged into @req. + */ static void dd_merged_requests(struct request_queue *q, struct request *req, struct request *next) { @@ -375,6 +378,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd) } /* + * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests(). + * * One confusing aspect here is that we get called for a specific * hardware queue, but we may return a request that is for a * different hardware queue. This is because mq-deadline has shared @@ -438,6 +443,10 @@ static int dd_init_queue(struct request_queue *q, struct elevator_type *e) return 0; } +/* + * Try to merge @bio into an existing request. If @bio has been merged into + * an existing request, store the pointer to that request into *@rq. + */ static int dd_request_merge(struct request_queue *q, struct request **rq, struct bio *bio) { @@ -461,6 +470,10 @@ static int dd_request_merge(struct request_queue *q, struct request **rq, return ELEVATOR_NO_MERGE; } +/* + * Attempt to merge a bio into an existing request. This function is called + * before @bio is associated with a request. + */ static bool dd_bio_merge(struct request_queue *q, struct bio *bio, unsigned int nr_segs) { @@ -518,6 +531,9 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, } } +/* + * Called from blk_mq_sched_insert_request() or blk_mq_sched_insert_requests(). + */ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx, struct list_head *list, bool at_head) { @@ -544,6 +560,8 @@ static void dd_prepare_request(struct request *rq) } /* + * Callback from inside blk_mq_free_request(). + * * For zoned block devices, write unlock the target zone of * completed write requests. Do this while holding the zone lock * spinlock so that the zone is never unlocked while deadline_fifo_request()