linux-kernel - Re: [PATCH 02/20] io-controller: Common flat fair queuing code in elevaotor layer

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Message-ID: <20090608125823.GC3652@redhat.com>
Date:	Mon, 8 Jun 2009 08:58:23 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Gui Jianfeng <guijianfeng@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, dm-devel@...hat.com,
	jens.axboe@...cle.com, nauman@...gle.com, dpshah@...gle.com,
	lizf@...fujitsu.com, mikew@...gle.com, fchecconi@...il.com,
	paolo.valente@...more.it, ryov@...inux.co.jp,
	fernando@....ntt.co.jp, s-uchida@...jp.nec.com, taka@...inux.co.jp,
	jmoyer@...hat.com, dhaval@...ux.vnet.ibm.com,
	balbir@...ux.vnet.ibm.com, righi.andrea@...il.com,
	m-ikeda@...jp.nec.com, jbaron@...hat.com, agk@...hat.com,
	snitzer@...hat.com, akpm@...ux-foundation.org, peterz@...radead.org
Subject: Re: [PATCH 02/20] io-controller: Common flat fair queuing code in
	elevaotor layer

On Mon, Jun 08, 2009 at 09:08:44AM +0800, Gui Jianfeng wrote:
> Vivek Goyal wrote:
> ...
> > +
> > +/* Get next queue for service. */
> > +struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
> > +{
> > +	struct elv_fq_data *efqd = &q->elevator->efqd;
> > +	struct io_entity *entity = NULL;
> > +	struct io_queue *ioq = NULL;
> > +	struct io_sched_data *sd;
> > +
> > +	/*
> > +	 * one can check for which queue will be selected next while having
> > +	 * one queue active. preempt logic uses it.
> > +	 */
> > +	BUG_ON(extract && efqd->active_queue != NULL);
> > +
> > +	if (!efqd->busy_queues)
> > +		return NULL;
> > +
> > +	sd = &efqd->root_group->sched_data;
> > +	if (extract)
> > +		entity = bfq_lookup_next_entity(sd, 1);
> > +	else
> > +		entity = bfq_lookup_next_entity(sd, 0);
> 
> This if and else branch is not needed.
> 
> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
> ---
>  block/elevator-fq.c |    5 +----
>  1 files changed, 1 insertions(+), 4 deletions(-)
> 
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index 3c5f9da..655162b 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -3069,10 +3069,7 @@ struct io_queue *elv_get_next_ioq(struct request_queue *q, int extract)
>  
>  	sd = &efqd->root_group->sched_data;
>  	for (; sd != NULL; sd = entity->my_sched_data) {
> -		if (extract)
> -			entity = bfq_lookup_next_entity(sd, 1);
> -		else
> -			entity = bfq_lookup_next_entity(sd, 0);
> +		entity = bfq_lookup_next_entity(sd, extract);
>  
>  		/*
>  		 * entity can be null despite the fact that there are busy

Thanks Gui. Queued for next posting.

Thanks
Vivek
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