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Commit 0e7be9ed authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Jens Axboe
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cfq_idle_class_timer: add paranoid checks for jiffies overflow 



In theory, if the queue was idle long enough, cfq_idle_class_timer may have
a false (and very long) timeout because jiffies can wrap into the past wrt
->last_end_request.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent b70c864d

block/cfq-iosched.c

+17 −11
Original line number Diff line number Diff line
@@ -789,6 +789,20 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, int timed_out) 
		__cfq_slice_expired(cfqd, cfqq, timed_out);

}



static int start_idle_class_timer(struct cfq_data *cfqd)

{

	unsigned long end = cfqd->last_end_request + CFQ_IDLE_GRACE;

	unsigned long now = jiffies;



	if (time_before(now, end) &&

	    time_after_eq(now, cfqd->last_end_request)) {

		mod_timer(&cfqd->idle_class_timer, end);

		return 1;

	}



	return 0;

}



/*

 * Get next queue for service. Unless we have a queue preemption,

 * we'll simply select the first cfqq in the service tree.
@@ -805,20 +819,15 @@ static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd) 
	cfqq = rb_entry(n, struct cfq_queue, rb_node);



	if (cfq_class_idle(cfqq)) {

		unsigned long end;



		/*

		 * if we have idle queues and no rt or be queues had

		 * pending requests, either allow immediate service if

		 * the grace period has passed or arm the idle grace

		 * timer

		 */

		end = cfqd->last_end_request + CFQ_IDLE_GRACE;

		if (time_before(jiffies, end)) {

			mod_timer(&cfqd->idle_class_timer, end);

		if (start_idle_class_timer(cfqd))

			cfqq = NULL;

	}

	}



	return cfqq;

}
@@ -2036,17 +2045,14 @@ static void cfq_idle_slice_timer(unsigned long data) 
static void cfq_idle_class_timer(unsigned long data)

{

	struct cfq_data *cfqd = (struct cfq_data *) data;

	unsigned long flags, end;

	unsigned long flags;



	spin_lock_irqsave(cfqd->queue->queue_lock, flags);



	/*

	 * race with a non-idle queue, reset timer

	 */

	end = cfqd->last_end_request + CFQ_IDLE_GRACE;

	if (!time_after_eq(jiffies, end))

		mod_timer(&cfqd->idle_class_timer, end);

	else

	if (!start_idle_class_timer(cfqd))

		cfq_schedule_dispatch(cfqd);



	spin_unlock_irqrestore(cfqd->queue->queue_lock, flags);