blkcg: don't call into policy draining if root_blkg is already gone

[firefly-linux-kernel-4.4.55.git] / block / blk-cgroup.c

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 069bc202ffe340fb69e9e3dc9414fe8b03043bd1..28d227c5ca7781aed5bb15cf37d3b0f1dcaa8d79 100644 (file)
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -80,7 +80,7 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
        blkg->q = q;
        INIT_LIST_HEAD(&blkg->q_node);
        blkg->blkcg = blkcg;
-       blkg->refcnt = 1;
+       atomic_set(&blkg->refcnt, 1);
 
        /* root blkg uses @q->root_rl, init rl only for !root blkgs */
        if (blkcg != &blkcg_root) {
@@ -399,11 +399,8 @@ void __blkg_release_rcu(struct rcu_head *rcu_head)
 
        /* release the blkcg and parent blkg refs this blkg has been holding */
        css_put(&blkg->blkcg->css);
-       if (blkg->parent) {
-               spin_lock_irq(blkg->q->queue_lock);
+       if (blkg->parent)
                blkg_put(blkg->parent);
-               spin_unlock_irq(blkg->q->queue_lock);
-       }
 
        blkg_free(blkg);
 }
@@ -875,6 +872,13 @@ void blkcg_drain_queue(struct request_queue *q)
 {
        lockdep_assert_held(q->queue_lock);
 
+       /*
+        * @q could be exiting and already have destroyed all blkgs as
+        * indicated by NULL root_blkg.  If so, don't confuse policies.
+        */
+       if (!q->root_blkg)
+               return;
+
        blk_throtl_drain(q);
 }
 
@@ -1093,7 +1097,7 @@ EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
  * Register @pol with blkcg core.  Might sleep and @pol may be modified on
  * successful registration.  Returns 0 on success and -errno on failure.
  */
-int __init blkcg_policy_register(struct blkcg_policy *pol)
+int blkcg_policy_register(struct blkcg_policy *pol)
 {
        int i, ret;