From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Wed, 7 Nov 2007 08:46:13 +0000 (+0100)
Subject: cfq: fix IOPRIO_CLASS_IDLE delays
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=b70c864d3ce706571d2f3cac1d35d4fba01d6072;p=openwrt%2Fstaging%2Fblogic.git

cfq: fix IOPRIO_CLASS_IDLE delays

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.

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

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 61a3f22eee29..6831a758d541 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -2126,6 +2126,7 @@ static void *cfq_init_queue(struct request_queue *q)
 
 	INIT_WORK(&cfqd->unplug_work, cfq_kick_queue);
 
+	cfqd->last_end_request = jiffies;
 	cfqd->cfq_quantum = cfq_quantum;
 	cfqd->cfq_fifo_expire[0] = cfq_fifo_expire[0];
 	cfqd->cfq_fifo_expire[1] = cfq_fifo_expire[1];