[PATCH v2] cfq-iosched: avoid probable slice overrun when idling

[Corrado Zoccolo <czoccolo@gmail.com>]

Idle timer is not armed if remaining slice is less than average think
time.

Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com>
---
 block/cfq-iosched.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index b35cc56..af1d621 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1099,6 +1099,14 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
 	if (!cic || !atomic_read(&cic->ioc->nr_tasks))
 		return;
 
+	/*
+	 * think time is greater than remaining time slice
+	 * don't idle, to avoid overrunnig the time slice
+	 */
+	if (sample_valid(cic->ttime_samples) &&
+		(cfqq->slice_end - jiffies < cic->ttime_mean))
+		return;
+
 	cfq_mark_cfqq_wait_request(cfqq);
 
 	/*
-- 
1.6.2.5