1 files changed, 17 insertions, 26 deletions

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index e4a6949fd171..35f8ffe92b70 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -46,6 +46,7 @@ struct blkcg_gq;
 struct blkcg {
 	struct cgroup_subsys_state	css;
 	spinlock_t			lock;
+	refcount_t			online_pin;
 
 	struct radix_tree_root		blkg_tree;
 	struct blkcg_gq	__rcu		*blkg_hint;
@@ -56,7 +57,6 @@ struct blkcg {
 	struct list_head		all_blkcgs_node;
 #ifdef CONFIG_CGROUP_WRITEBACK
 	struct list_head		cgwb_list;
-	refcount_t			cgwb_refcnt;
 #endif
 };
 
@@ -412,47 +412,38 @@ static inline struct blkcg *cpd_to_blkcg(struct blkcg_policy_data *cpd)
 
 extern void blkcg_destroy_blkgs(struct blkcg *blkcg);
 
-#ifdef CONFIG_CGROUP_WRITEBACK
-
 /**
- * blkcg_cgwb_get - get a reference for blkcg->cgwb_list
+ * blkcg_pin_online - pin online state
  * @blkcg: blkcg of interest
  *
- * This is used to track the number of active wb's related to a blkcg.
+ * While pinned, a blkcg is kept online.  This is primarily used to
+ * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
+ * while an associated cgwb is still active.
  */
-static inline void blkcg_cgwb_get(struct blkcg *blkcg)
+static inline void blkcg_pin_online(struct blkcg *blkcg)
 {
-	refcount_inc(&blkcg->cgwb_refcnt);
+	refcount_inc(&blkcg->online_pin);
 }
 
 /**
- * blkcg_cgwb_put - put a reference for @blkcg->cgwb_list
+ * blkcg_unpin_online - unpin online state
  * @blkcg: blkcg of interest
  *
- * This is used to track the number of active wb's related to a blkcg.
- * When this count goes to zero, all active wb has finished so the
+ * This is primarily used to impedance-match blkg and cgwb lifetimes so
+ * that blkg doesn't go offline while an associated cgwb is still active.
+ * When this count goes to zero, all active cgwbs have finished so the
  * blkcg can continue destruction by calling blkcg_destroy_blkgs().
- * This work may occur in cgwb_release_workfn() on the cgwb_release
- * workqueue.
  */
-static inline void blkcg_cgwb_put(struct blkcg *blkcg)
+static inline void blkcg_unpin_online(struct blkcg *blkcg)
 {
-	if (refcount_dec_and_test(&blkcg->cgwb_refcnt))
+	do {
+		if (!refcount_dec_and_test(&blkcg->online_pin))
+			break;
 		blkcg_destroy_blkgs(blkcg);
+		blkcg = blkcg_parent(blkcg);
+	} while (blkcg);
 }
 
-#else
-
-static inline void blkcg_cgwb_get(struct blkcg *blkcg) { }
-
-static inline void blkcg_cgwb_put(struct blkcg *blkcg)
-{
-	/* wb isn't being accounted, so trigger destruction right away */
-	blkcg_destroy_blkgs(blkcg);
-}
-
-#endif
-
 /**
  * blkg_path - format cgroup path of blkg
  * @blkg: blkg of interest