3 files changed, 5 insertions, 10 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 54ad00292edf..e90c7c164c83 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -615,12 +615,10 @@ u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off)
         struct blkcg_policy *pol = blkcg_policy[pd->plid];
         struct blkcg_gq *pos_blkg;
         struct cgroup_subsys_state *pos_css;
-        u64 sum;
+        u64 sum = 0;
 
         lockdep_assert_held(pd->blkg->q->queue_lock);
 
-        sum = blkg_stat_read((void *)pd + off);
-
         rcu_read_lock();
         blkg_for_each_descendant_pre(pos_blkg, pos_css, pd_to_blkg(pd)) {
                 struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
@@ -650,13 +648,11 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
         struct blkcg_policy *pol = blkcg_policy[pd->plid];
         struct blkcg_gq *pos_blkg;
         struct cgroup_subsys_state *pos_css;
-        struct blkg_rwstat sum;
+        struct blkg_rwstat sum = { };
         int i;
 
         lockdep_assert_held(pd->blkg->q->queue_lock);
 
-        sum = blkg_rwstat_read((void *)pd + off);
-
         rcu_read_lock();
         blkg_for_each_descendant_pre(pos_blkg, pos_css, pd_to_blkg(pd)) {
                 struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 855538630300..ae6969a7ffd4 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -291,6 +291,7 @@ struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
  * read locked.  If called under either blkcg or queue lock, the iteration
  * is guaranteed to include all and only online blkgs.  The caller may
  * update @pos_css by calling css_rightmost_descendant() to skip subtree.
+ * @p_blkg is included in the iteration and the first node to be visited.
  */
 #define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)           \
         css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)   \
@@ -304,7 +305,8 @@ struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
  * @p_blkg: target blkg to walk descendants of
  *
  * Similar to blkg_for_each_descendant_pre() but performs post-order
- * traversal instead.  Synchronization rules are the same.
+ * traversal instead.  Synchronization rules are the same.  @p_blkg is
+ * included in the iteration and the last node to be visited.
  */
 #define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)          \
         css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)  \
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8cefa7f8590e..8331aba9426f 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1379,7 +1379,6 @@ static int tg_set_conf(struct cgroup_subsys_state *css, struct cftype *cft,
          * restrictions in the whole hierarchy and allows them to bypass
          * blk-throttle.
          */
-        tg_update_has_rules(tg);
         blkg_for_each_descendant_pre(blkg, pos_css, ctx.blkg)
                 tg_update_has_rules(blkg_to_tg(blkg));
 
@@ -1639,8 +1638,6 @@ void blk_throtl_drain(struct request_queue *q)
         blkg_for_each_descendant_post(blkg, pos_css, td->queue->root_blkg)
                 tg_drain_bios(&blkg_to_tg(blkg)->service_queue);
 
-        tg_drain_bios(&td_root_tg(td)->service_queue);
-
         /* finally, transfer bios from top-level tg's into the td */
         tg_drain_bios(&td->service_queue);