Re: [PATCH v1 4/6] block: check bio_mergeable() early before merging

[Jeff Moyer]

Ming Lei <ming.lei@xxxxxxxxxxxxx> writes:

> After bio splitting is introduced, one bio can be splitted
> and it is marked as NOMERGE because it is too fat to be merged,
> so check bio_mergeable() earlier to avoid to try to merge it
> unnecessarily.
>
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx>

Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>

Ming, do you think we should also add a check in blk_attempt_plug_merge?

-Jeff

> ---
>  block/elevator.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/elevator.c b/block/elevator.c
> index 84d6394..c3555c9 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -420,7 +420,7 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
>  	 * 	noxmerges: Only simple one-hit cache try
>  	 * 	merges:	   All merge tries attempted
>  	 */
> -	if (blk_queue_nomerges(q))
> +	if (blk_queue_nomerges(q) || !bio_mergeable(bio))
>  		return ELEVATOR_NO_MERGE;
>  
>  	/*
--
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