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From: Bart Van Assche <bvanassche@acm.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	Adam Manzanares <a.manzanares@samsung.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	Johannes Thumshirn <johannes.thumshirn@wdc.com>,
	Himanshu Madhani <himanshu.madhani@oracle.com>,
	Hannes Reinecke <hare@suse.de>, Ming Lei <ming.lei@redhat.com>
Subject: [PATCH v3 05/16] block/mq-deadline: Add several comments
Date: Thu, 17 Jun 2021 17:44:45 -0700	[thread overview]
Message-ID: <20210618004456.7280-6-bvanassche@acm.org> (raw)
In-Reply-To: <20210618004456.7280-1-bvanassche@acm.org>

Make the code easier to read by adding more comments.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 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()

  parent reply	other threads:[~2021-06-18  0:45 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-18  0:44 [PATCH v3 00/16] Improve I/O priority support Bart Van Assche
2021-06-18  0:44 ` [PATCH v3 01/16] block/Kconfig: Make the BLK_WBT and BLK_WBT_MQ entries consecutive Bart Van Assche
2021-06-18 17:09   ` Adam Manzanares
2021-06-18 19:49   ` Himanshu Madhani
2021-06-18  0:44 ` [PATCH v3 02/16] block/blk-cgroup: Swap the blk_throtl_init() and blk_iolatency_init() calls Bart Van Assche
2021-06-18 17:15   ` Adam Manzanares
2021-06-18 19:49   ` Himanshu Madhani
2021-06-21 14:24   ` Tejun Heo
2021-06-18  0:44 ` [PATCH v3 03/16] block/blk-rq-qos: Move a function from a header file into a C file Bart Van Assche
2021-06-18 17:22   ` Adam Manzanares
2021-06-18 19:49   ` Himanshu Madhani
2021-06-18  0:44 ` [PATCH v3 04/16] block: Introduce the ioprio rq-qos policy Bart Van Assche
2021-06-18 22:02   ` Adam Manzanares
2021-06-18  0:44 ` Bart Van Assche [this message]
2021-06-18 22:06   ` [PATCH v3 05/16] block/mq-deadline: Add several comments Adam Manzanares
2021-06-18  0:44 ` [PATCH v3 06/16] block/mq-deadline: Add two lockdep_assert_held() statements Bart Van Assche
2021-06-18 22:09   ` Adam Manzanares
2021-06-18  0:44 ` [PATCH v3 07/16] block/mq-deadline: Remove two local variables Bart Van Assche
2021-06-18 22:16   ` Adam Manzanares
2021-06-18  0:44 ` [PATCH v3 08/16] block/mq-deadline: Rename dd_init_queue() and dd_exit_queue() Bart Van Assche
2021-06-18 22:18   ` Adam Manzanares
2021-06-18  0:44 ` [PATCH v3 09/16] block/mq-deadline: Improve compile-time argument checking Bart Van Assche
2021-06-18 22:30   ` Adam Manzanares
2021-06-18  0:44 ` [PATCH v3 10/16] block/mq-deadline: Improve the sysfs show and store macros Bart Van Assche
2021-06-18 23:07   ` Adam Manzanares
2021-06-18  0:44 ` [PATCH v3 11/16] block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests Bart Van Assche
2021-06-18  0:44 ` [PATCH v3 12/16] block/mq-deadline: Micro-optimize the batching algorithm Bart Van Assche
2021-06-18  0:44 ` [PATCH v3 13/16] block/mq-deadline: Add I/O priority support Bart Van Assche
2021-06-18  0:44 ` [PATCH v3 14/16] block/mq-deadline: Track I/O statistics Bart Van Assche
2021-06-18  0:44 ` [PATCH v3 15/16] block/mq-deadline: Add cgroup support Bart Van Assche
2021-06-18  0:44 ` [PATCH v3 16/16] block/mq-deadline: Prioritize high-priority requests Bart Van Assche
2021-08-20  0:45   ` Niklas Cassel
2021-08-20 18:04     ` Bart Van Assche
2021-08-20 23:05       ` Niklas Cassel
2021-08-20 23:38         ` Bart Van Assche
2021-08-23  7:36           ` Niklas Cassel
2021-08-23 17:15             ` Bart Van Assche
2021-08-23 23:01               ` Damien Le Moal
2021-08-24 21:33               ` Niklas Cassel
2021-06-21 16:06 ` [PATCH v3 00/16] Improve I/O priority support Jens Axboe

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