[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>

1 files changed, 2 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 452538644bce..2b64f5852bfd 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -861,8 +861,8 @@ __cfq_slice_expired(struct cfq_data *cfqd, struct cfq_queue *cfqq,
          * 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;