Re: [PATCH V3] block: optimize for small block size IO

[Jens Axboe <axboe@xxxxxxxxx>]

On 10/29/19 4:51 AM, Ming Lei wrote:
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 48e6725b32ee..737bbec9e153 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -309,6 +309,10 @@ void __blk_queue_split(struct request_queue *q, struct bio **bio,
>   				nr_segs);
>   		break;
>   	default:
> +		if (!bio_flagged(*bio, BIO_MULTI_PAGE)) {
> +			*nr_segs = 1;
> +			return;
> +		}
>   		split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs);
>   		break;
>   	}

Can we just make that:

  	default:
		if (!bio_flagged(*bio, BIO_MULTI_PAGE)) {
			*nr_segs = 1;
			split = NULL;
		} else {
  			split = blk_bio_segment_split(q, *bio, &q->bio_split,
							nr_segs);
		}
  		break;

Otherwise this looks fine to me, and the win is palatable.

-- 
Jens Axboe