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FROMGIT: block/mq-deadline: Add several comments

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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>
BUG: 187357408
Change-Id: If62eb600614d2883d72ee3bd7e7859ae66b24512
(cherry picked from commit 16c3afdb127bbff7d3552e076e568281765674b7 git://git.kernel.dk/linux-block/ for-5.14/block)
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche 2021-05-21 11:00:46 -07:00 committed by Todd Kjos
parent 46d6ae07a7
commit dfc5e14a36
1 changed files with 18 additions and 0 deletions
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18
block/mq-deadline.c
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@ -137,6 +137,9 @@ 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)
{
@ -373,6 +376,8 @@ 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
@ -436,6 +441,10 @@ 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)
{
@ -459,6 +468,10 @@ 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)
{
@ -516,6 +529,9 @@ 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)
{
@ -542,6 +558,8 @@ 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()