1 files changed, 13 insertions, 3 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 86338d5d4d09..dfceb6386bd5 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -157,6 +157,7 @@ enum wl_prio_t {
         BE_WORKLOAD = 0,
         RT_WORKLOAD = 1,
         IDLE_WORKLOAD = 2,
+        CFQ_PRIO_NR,
 };
 
 /*
@@ -181,10 +182,19 @@ struct cfq_group {
         /* number of cfqq currently on this group */
         int nr_cfqq;
 
-        /* Per group busy queus average. Useful for workload slice calc. */
-        unsigned int busy_queues_avg[2];
         /*
-         * rr lists of queues with requests, onle rr for each priority class.
+         * Per group busy queus average. Useful for workload slice calc. We
+         * create the array for each prio class but at run time it is used
+         * only for RT and BE class and slot for IDLE class remains unused.
+         * This is primarily done to avoid confusion and a gcc warning.
+         */
+        unsigned int busy_queues_avg[CFQ_PRIO_NR];
+        /*
+         * rr lists of queues with requests. We maintain service trees for
+         * RT and BE classes. These trees are subdivided in subclasses
+         * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
+         * class there is no subclassification and all the cfq queues go on
+         * a single tree service_tree_idle.
          * Counts are embedded in the cfq_rb_root
          */
         struct cfq_rb_root service_trees[2][3];