[PATCH] cfq-iosched: busy_rr fairness fix

Now that we select busy_rr for possible service, insert entries at the
back of that list instead of at the front.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 5 insertions, 2 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 85d188a30f82..8e9d84825e1c 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -501,10 +501,13 @@ static void cfq_resort_rr_list(struct cfq_queue *cfqq, int preempted)
 
         /*
          * if queue was preempted, just add to front to be fair. busy_rr
-         * isn't sorted.
+         * isn't sorted, but insert at the back for fairness.
          */
         if (preempted || list == &cfqd->busy_rr) {
-                list_add(&cfqq->cfq_list, list);
+                if (preempted)
+                        list = list->prev;
+
+                list_add_tail(&cfqq->cfq_list, list);
                 return;
         }