1 files changed, 41 insertions, 12 deletions

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 89e0d1cc14b..12e380b2c4e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -178,6 +178,8 @@ struct cfq_group {
         /* group service_tree key */
         u64 vdisktime;
         unsigned int weight;
+        unsigned int new_weight;
+        bool needs_update;
 
         /* number of cfqq currently on this group */
         int nr_cfqq;
@@ -853,7 +855,27 @@ __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
 }
 
 static void
-cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
+cfq_update_group_weight(struct cfq_group *cfqg)
+{
+        BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+        if (cfqg->needs_update) {
+                cfqg->weight = cfqg->new_weight;
+                cfqg->needs_update = false;
+        }
+}
+
+static void
+cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+        BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+
+        cfq_update_group_weight(cfqg);
+        __cfq_group_service_tree_add(st, cfqg);
+        st->total_weight += cfqg->weight;
+}
+
+static void
+cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
         struct cfq_rb_root *st = &cfqd->grp_service_tree;
         struct cfq_group *__cfqg;
@@ -874,13 +896,19 @@ cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
                 cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
         } else
                 cfqg->vdisktime = st->min_vdisktime;
+        cfq_group_service_tree_add(st, cfqg);
+}
 
-        __cfq_group_service_tree_add(st, cfqg);
-        st->total_weight += cfqg->weight;
+static void
+cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+        st->total_weight -= cfqg->weight;
+        if (!RB_EMPTY_NODE(&cfqg->rb_node))
+                cfq_rb_erase(&cfqg->rb_node, st);
 }
 
 static void
-cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
+cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
 {
         struct cfq_rb_root *st = &cfqd->grp_service_tree;
 
@@ -892,9 +920,7 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
                 return;
 
         cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
-        st->total_weight -= cfqg->weight;
-        if (!RB_EMPTY_NODE(&cfqg->rb_node))
-                cfq_rb_erase(&cfqg->rb_node, st);
+        cfq_group_service_tree_del(st, cfqg);
         cfqg->saved_workload_slice = 0;
         cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
 }
@@ -948,9 +974,10 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
                 charge = cfqq->allocated_slice;
 
         /* Can't update vdisktime while group is on service tree */
-        cfq_rb_erase(&cfqg->rb_node, st);
+        cfq_group_service_tree_del(st, cfqg);
         cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
-        __cfq_group_service_tree_add(st, cfqg);
+        /* If a new weight was requested, update now, off tree */
+        cfq_group_service_tree_add(st, cfqg);
 
         /* This group is being expired. Save the context */
         if (time_after(cfqd->workload_expires, jiffies)) {
@@ -982,7 +1009,9 @@ static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
 void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
                                         unsigned int weight)
 {
-        cfqg_of_blkg(blkg)->weight = weight;
+        struct cfq_group *cfqg = cfqg_of_blkg(blkg);
+        cfqg->new_weight = weight;
+        cfqg->needs_update = true;
 }
 
 static struct cfq_group *
@@ -1255,7 +1284,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
         service_tree->count++;
         if ((add_front || !new_cfqq) && !group_changed)
                 return;
-        cfq_group_service_tree_add(cfqd, cfqq->cfqg);
+        cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
 }
 
 static struct cfq_queue *
@@ -1368,7 +1397,7 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
                 cfqq->p_root = NULL;
         }
 
-        cfq_group_service_tree_del(cfqd, cfqq->cfqg);
+        cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
         BUG_ON(!cfqd->busy_queues);
         cfqd->busy_queues--;
         if (cfq_cfqq_sync(cfqq))