Re: [PATCH 2/9] block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ

From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
	kashyap.desai@broadcom.com, hare@suse.de
Subject: Re: [PATCH 2/9] block: Rename BLKDEV_MAX_RQ -> BLKDEV_DEFAULT_RQ
Date: Tue, 20 Jul 2021 15:44:19 +0800	[thread overview]
Message-ID: <YPZ+02j486IuuZ+J@T590> (raw)
In-Reply-To: <1626275195-215652-3-git-send-email-john.garry@huawei.com>

On Wed, Jul 14, 2021 at 11:06:28PM +0800, John Garry wrote:
> It is a bit confusing that there is BLKDEV_MAX_RQ and MAX_SCHED_RQ, as
> the name BLKDEV_MAX_RQ would imply the max requests always, which it is
> not.
> 
> Rename to BLKDEV_MAX_RQ to BLKDEV_DEFAULT_RQ, matching its usage - that being
> the default number of requests assigned when allocating a request queue.
> 
> Signed-off-by: John Garry <john.garry@huawei.com>
> ---
>  block/blk-core.c       | 2 +-
>  block/blk-mq-sched.c   | 2 +-
>  block/blk-mq-sched.h   | 2 +-
>  drivers/block/rbd.c    | 2 +-
>  include/linux/blkdev.h | 2 +-
>  5 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 04477697ee4b..5d71382b6131 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -579,7 +579,7 @@ struct request_queue *blk_alloc_queue(int node_id)
>  
>  	blk_queue_dma_alignment(q, 511);
>  	blk_set_default_limits(&q->limits);
> -	q->nr_requests = BLKDEV_MAX_RQ;
> +	q->nr_requests = BLKDEV_DEFAULT_RQ;

The above assignment isn't necessary since bio based queue doesn't use
->nr_requests. For request based queue, ->nr_requests will be re-set
in either blk_mq_init_sched() or blk_mq_init_allocated_queue(), but
that may not be related with this patch itself.

>  
>  	return q;
>  
> diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
> index c838d81ac058..f5cb2931c20d 100644
> --- a/block/blk-mq-sched.c
> +++ b/block/blk-mq-sched.c
> @@ -615,7 +615,7 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
>  	 * Additionally, this is a per-hw queue depth.
>  	 */
>  	q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
> -				   BLKDEV_MAX_RQ);
> +				   BLKDEV_DEFAULT_RQ);
>  
>  	queue_for_each_hw_ctx(q, hctx, i) {
>  		ret = blk_mq_sched_alloc_tags(q, hctx, i);
> diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h
> index 5246ae040704..1e46be6c5178 100644
> --- a/block/blk-mq-sched.h
> +++ b/block/blk-mq-sched.h
> @@ -5,7 +5,7 @@
>  #include "blk-mq.h"
>  #include "blk-mq-tag.h"
>  
> -#define MAX_SCHED_RQ (16 * BLKDEV_MAX_RQ)
> +#define MAX_SCHED_RQ (16 * BLKDEV_DEFAULT_RQ)
>  
>  void blk_mq_sched_assign_ioc(struct request *rq);
>  
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 531d390902dd..d3f329749173 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -836,7 +836,7 @@ struct rbd_options {
>  	u32 alloc_hint_flags;  /* CEPH_OSD_OP_ALLOC_HINT_FLAG_* */
>  };
>  
> -#define RBD_QUEUE_DEPTH_DEFAULT	BLKDEV_MAX_RQ
> +#define RBD_QUEUE_DEPTH_DEFAULT	BLKDEV_DEFAULT_RQ
>  #define RBD_ALLOC_SIZE_DEFAULT	(64 * 1024)
>  #define RBD_LOCK_TIMEOUT_DEFAULT 0  /* no timeout */
>  #define RBD_READ_ONLY_DEFAULT	false
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 3177181c4326..6a64ea23f552 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -45,7 +45,7 @@ struct blk_stat_callback;
>  struct blk_keyslot_manager;
>  
>  #define BLKDEV_MIN_RQ	4
> -#define BLKDEV_MAX_RQ	128	/* Default maximum */
> +#define BLKDEV_DEFAULT_RQ	128
>  
>  /* Must be consistent with blk_mq_poll_stats_bkt() */
>  #define BLK_MQ_POLL_STATS_BKTS 16
> -- 
> 2.26.2
> 

Looks fine,

Reviewed-by: Ming Lei <ming.lei@redhat.com>

-- 
Ming