linux-kernel - Re: [PATCH 2/5] sched: always use blk_schedule_flush_plug in io_schedule

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Message-ID: <20150501171410.GB16920@lst.de>
Date:	Fri, 1 May 2015 19:14:10 +0200
From:	Christoph Hellwig <hch@....de>
To:	Shaohua Li <shli@...com>
Cc:	linux-kernel@...r.kernel.org, axboe@...com, jmoyer@...hat.com,
	hch@....de, neilb@...e.de
Subject: Re: [PATCH 2/5] sched: always use blk_schedule_flush_plug in
	io_schedule_out

On Thu, Apr 30, 2015 at 10:45:15AM -0700, Shaohua Li wrote:
>  long __sched io_schedule_timeout(long timeout)
>  {
> -	int old_iowait = current->in_iowait;
>  	struct rq *rq;
>  	long ret;
>  
>  	current->in_iowait = 1;
> -	if (old_iowait)
> -		blk_schedule_flush_plug(current);
> -	else
> -		blk_flush_plug(current);
> +	blk_schedule_flush_plug(current);
>  
>  	delayacct_blkio_start();
>  	rq = raw_rq();
>  	atomic_inc(&rq->nr_iowait);
>  	ret = schedule_timeout(timeout);
> -	current->in_iowait = old_iowait;
> +	current->in_iowait = 0;

Always clearing ->in_iowait is behavior change not mentioned in the
changelog.  Even if it was intentional it would better be done in
a separate patch.
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