linux-kernel - Re: [PATCH 4/4] disk-protect: Add a generic block layer queue freezing facility

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Message-ID: <20080315124952.GC4669@ucw.cz>
Date:	Sat, 15 Mar 2008 13:49:52 +0100
From:	Pavel Machek <pavel@....cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [PATCH 4/4] disk-protect: Add a generic block layer queue freezing facility

On Fri 2008-03-07 19:26:41, Elias Oltmanns wrote:
> This patch provides a generic way to freeze the request queue of a block
> device temporarily. This functionality is exposed to user space via sysfs.
> 
> Signed-off-by: Elias Oltmanns <eo@...ensachen.de>

I guess this should have patch going to documentation. Otherwise it
looks ok.


> +/*
> + * When reading the 'protect' attribute, we return seconds remaining
> + * before the unfreeze timeout expires.
> + */
> +static ssize_t queue_protect_show(struct request_queue *q, char *page)
> +{
> +	unsigned int seconds = 0;
> +
> +	if (blk_queue_stopped(q) && timer_pending(&q->unfreeze_timer))
> +		/*
> +		 * Adding 1 in order to guarantee nonzero value until timer
> +		 * has actually expired.
> +		 */
> +		seconds = jiffies_to_msecs(q->unfreeze_timer.expires
> +					   - jiffies) / 1000 + 1;

Is it okay to read expires without locking? 
						Pavel
-- 
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