linux-kernel - Re: [PATCH 2/4] block: avoid to merge splitted bio

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Message-ID: <x49twpsgo2m.fsf@segfault.boston.devel.redhat.com>
Date:	Thu, 15 Oct 2015 11:15:45 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	Ming Lin <ming.l@....samsung.com>,
	Kent Overstreet <kent.overstreet@...il.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH 2/4] block: avoid to merge splitted bio

Ming Lei <ming.lei@...onical.com> writes:

> The splitted bio has been already too fat to merge, so mark it
> as NOMERGE.
>
> Signed-off-by: Ming Lei <ming.lei@...onical.com>

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>

> ---
>  block/blk-merge.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 22293fd..de5716d8 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -139,6 +139,9 @@ void blk_queue_split(struct request_queue *q, struct bio **bio,
>  	bio_set_flag(res, BIO_SEG_VALID);
>  
>  	if (split) {
> +		/* there isn't chance to merge the splitted bio */
> +		split->bi_rw |= REQ_NOMERGE;
> +
>  		bio_chain(split, *bio);
>  		generic_make_request(*bio);
>  		*bio = split;
--
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