linux-kernel - Re: [PATCH] cfq: fix IOPRIO_CLASS

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Date:	Tue, 6 Nov 2007 20:26:11 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, Nick <gentuu@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cfq: fix IOPRIO_CLASS_IDLE delays

On Tue, Nov 06 2007, Oleg Nesterov wrote:
> After the fresh boot:
> 
> 	ionice -c3 -p $$
> 	echo cfq >> /sys/block/XXX/queue/scheduler
> 	dd if=/dev/XXX of=/dev/null bs=512 count=1
> 
> Now dd hangs in D state and the queue is completely stalled for approximately
> INITIAL_JIFFIES + CFQ_IDLE_GRACE jiffies. This is because cfq_init_queue()
> forgets to initialize cfq_data->last_end_request.

Another good catch, thanks Oleg!

> (I guess this patch is not complete, overflow is still possible)

Hmm, where would it overflow?

-- 
Jens Axboe

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