[05/14] block/mq-deadline: Add several comments

Commit Message

Bart Van Assche June 8, 2021, 11:06 p.m. UTC

Make the code easier to read by adding more comments.

Reviewed-by: Damien Le Moal <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Himanshu Madhani <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Cc: Ming Lei <[e-mail]>
Signed-off-by: Bart Van Assche <[e-mail]>
---
 block/mq-deadline.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Comments

Hannes Reinecke June 10, 2021, 6:21 a.m. UTC | #1

On 6/9/21 1:06 AM, Bart Van Assche wrote:
> Make the code easier to read by adding more comments.
> 
> Reviewed-by: Damien Le Moal <[e-mail]>
> Reviewed-by: Johannes Thumshirn <[e-mail]>
> Reviewed-by: Himanshu Madhani <[e-mail]>
> Cc: Christoph Hellwig <[e-mail]>
> Cc: Hannes Reinecke <[e-mail]>
> Cc: Ming Lei <[e-mail]>
> Signed-off-by: Bart Van Assche <[e-mail]>
> ---
>  block/mq-deadline.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
Reviewed-by: Hannes Reinecke <[e-mail]>

Cheers,

Hannes

Patch

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()