Re: [PATCH v3 05/16] block/mq-deadline: Add several comments

From: Adam Manzanares <a.manzanares@samsung.com>
To: Bart Van Assche <bvanassche@acm.org>
Cc: Jens Axboe <axboe@kernel.dk>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Christoph Hellwig <hch@lst.de>, Jaegeuk Kim <jaegeuk@kernel.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: Re: [PATCH v3 05/16] block/mq-deadline: Add several comments
Date: Fri, 18 Jun 2021 22:06:38 +0000	[thread overview]
Message-ID: <20210618220638.GB210778@bgt-140510-bm01> (raw)
In-Reply-To: <20210618004456.7280-6-bvanassche@acm.org>

On Thu, Jun 17, 2021 at 05:44:45PM -0700, Bart Van Assche wrote:
> 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()

Looks good.

Reviewed by: Adam Manzanares <a.manzanares@samsung.com>