3 files changed, 13 insertions, 2 deletions

diff --git a/block/Kconfig b/block/Kconfig
index 09acf1b39905..a7e40a7c8214 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -89,7 +89,7 @@ config BLK_DEV_INTEGRITY
 
 config BLK_DEV_THROTTLING
         bool "Block layer bio throttling support"
-        depends on BLK_CGROUP=y && EXPERIMENTAL
+        depends on BLK_CGROUP=y
         default n
         ---help---
         Block layer bio throttling support. It can be used to limit
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 6ce36ff98a41..3dc60fc441cb 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -285,6 +285,13 @@ static void blkg_destroy_all(struct request_queue *q)
                 blkg_destroy(blkg);
                 spin_unlock(&blkcg->lock);
         }
+
+        /*
+         * root blkg is destroyed.  Just clear the pointer since
+         * root_rl does not take reference on root blkg.
+         */
+        q->root_blkg = NULL;
+        q->root_rl.blkg = NULL;
 }
 
 static void blkg_rcu_free(struct rcu_head *rcu_head)
@@ -326,6 +333,9 @@ struct request_list *__blk_queue_next_rl(struct request_list *rl,
          */
         if (rl == &q->root_rl) {
                 ent = &q->blkg_list;
+                /* There are no more block groups, hence no request lists */
+                if (list_empty(ent))
+                        return NULL;
         } else {
                 blkg = container_of(rl, struct blkcg_gq, rl);
                 ent = &blkg->q_node;
diff --git a/block/blk-core.c b/block/blk-core.c
index a33870b1847b..3c95c4d6e31a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2868,7 +2868,8 @@ static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
         struct request *rqa = container_of(a, struct request, queuelist);
         struct request *rqb = container_of(b, struct request, queuelist);
 
-        return !(rqa->q <= rqb->q);
+        return !(rqa->q < rqb->q ||
+                (rqa->q == rqb->q && blk_rq_pos(rqa) < blk_rq_pos(rqb)));
 }
 
 /*