Re: [PATCH 3/9] blk-mq: Relocate shared sbitmap resize in blk_mq_update_nr_requests()

[Ming Lei]

On Wed, Jul 14, 2021 at 11:06:29PM +0800, John Garry wrote:
> For shared sbitmap, if the call to blk_mq_tag_update_depth() was
> successful for any hctx when hctx->sched_tags is not set, then it would be
> successful for all (due to nature in which blk_mq_tag_update_depth()
> fails).
> 
> As such, there is no need to call blk_mq_tag_resize_shared_sbitmap() for
> each hctx. So relocate the call until after the hctx iteration under the
> !q->elevator check, which is equivalent (to !hctx->sched_tags).
> 
> Signed-off-by: John Garry <john.garry@xxxxxxxxxx>
> ---
>  block/blk-mq.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index ae28f470893c..56e3c6fdba60 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -3624,8 +3624,6 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
>  		if (!hctx->sched_tags) {
>  			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
>  							false);
> -			if (!ret && blk_mq_is_sbitmap_shared(set->flags))
> -				blk_mq_tag_resize_shared_sbitmap(set, nr);
>  		} else {
>  			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
>  							nr, true);
> @@ -3643,9 +3641,14 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
>  	}
>  	if (!ret) {
>  		q->nr_requests = nr;
> -		if (q->elevator && blk_mq_is_sbitmap_shared(set->flags))
> -			sbitmap_queue_resize(&q->sched_bitmap_tags,
> -					     nr - set->reserved_tags);
> +		if (blk_mq_is_sbitmap_shared(set->flags)) {
> +			if (q->elevator) {
> +				sbitmap_queue_resize(&q->sched_bitmap_tags,
> +						     nr - set->reserved_tags);
> +			} else {
> +				blk_mq_tag_resize_shared_sbitmap(set, nr);
> +			}

The above two {} can be removed.

-- 
Ming