1 files changed, 21 insertions, 8 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 069bc202ffe3..e17da947f6bd 100644
--- 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);
 }
 
@@ -924,7 +928,15 @@ struct cgroup_subsys blkio_cgrp_subsys = {
 	.css_offline = blkcg_css_offline,
 	.css_free = blkcg_css_free,
 	.can_attach = blkcg_can_attach,
-	.base_cftypes = blkcg_files,
+	.legacy_cftypes = blkcg_files,
+#ifdef CONFIG_MEMCG
+	/*
+	 * This ensures that, if available, memcg is automatically enabled
+	 * together on the default hierarchy so that the owner cgroup can
+	 * be retrieved from writeback pages.
+	 */
+	.depends_on = 1 << memory_cgrp_id,
+#endif
 };
 EXPORT_SYMBOL_GPL(blkio_cgrp_subsys);
 
@@ -1093,7 +1105,7 @@ 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;
 
@@ -1116,7 +1128,8 @@ int __init blkcg_policy_register(struct blkcg_policy *pol)
 
 	/* everything is in place, add intf files for the new policy */
 	if (pol->cftypes)
-		WARN_ON(cgroup_add_cftypes(&blkio_cgrp_subsys, pol->cftypes));
+		WARN_ON(cgroup_add_legacy_cftypes(&blkio_cgrp_subsys,
+						  pol->cftypes));
 	ret = 0;
 out_unlock:
 	mutex_unlock(&blkcg_pol_mutex);