Re: [PATCH v2 5/7] block: check bio_mergeable() early before merging

From: Jeff Moyer
Date: Tue Oct 20 2015 - 11:22:16 EST


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>

> ---
> 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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