[BLOCK] cfq-iosched: fix slice_left calculation
When cfq slice expires, remainder of slice is calculated and stored in
cfqq->slice_left. Current code calculates the opposite of remainder -
how many jiffies the cfqq has used past slice end. This patch fixes
the bug.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 4525386..2b64f58 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -861,8 +861,8 @@
* store what was left of this slice, if the queue idled out
* or was preempted
*/
- if (time_after(now, cfqq->slice_end))
- cfqq->slice_left = now - cfqq->slice_end;
+ if (time_after(cfqq->slice_end, now))
+ cfqq->slice_left = cfqq->slice_end - now;
else
cfqq->slice_left = 0;