[PATCH v2] blk-cgroup: remove entries in blkg_tree before queue release

[Alexandru Moise <00moses.alexander00@gmail.com>]

The q->id is used as an index within the blkg_tree radix tree.

If the entry is not released before reclaiming the blk_queue_ida's id
blkcg_init_queue() within a different driver from which this id
was originally for can fail due to the entry at that index within
the radix tree already existing.

Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com>
---
v2: Added no-op for !CONFIG_BLK_CGROUP

 block/blk-cgroup.c         | 2 +-
 block/blk-sysfs.c          | 4 ++++
 include/linux/blk-cgroup.h | 3 +++
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1c16694ae145..224e937dbb59 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -369,7 +369,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
  *
  * Destroy all blkgs associated with @q.
  */
-static void blkg_destroy_all(struct request_queue *q)
+void blkg_destroy_all(struct request_queue *q)
 {
 	struct blkcg_gq *blkg, *n;
 
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index d00d1b0ec109..a72866458f22 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -816,6 +816,10 @@ static void __blk_release_queue(struct work_struct *work)
 	if (q->bio_split)
 		bioset_free(q->bio_split);
 
+	spin_lock_irq(q->queue_lock);
+	blkg_destroy_all(q);
+	spin_unlock_irq(q->queue_lock);
+
 	ida_simple_remove(&blk_queue_ida, q->id);
 	call_rcu(&q->rcu_head, blk_free_queue_rcu);
 }
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 6c666fd7de3c..3d60b1d1973d 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -179,6 +179,8 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 int blkcg_init_queue(struct request_queue *q);
 void blkcg_drain_queue(struct request_queue *q);
 void blkcg_exit_queue(struct request_queue *q);
+void blkg_destroy_all(struct request_queue *q);
+
 
 /* Blkio controller policy registration */
 int blkcg_policy_register(struct blkcg_policy *pol);
@@ -740,6 +742,7 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { ret
 static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
 static inline void blkcg_drain_queue(struct request_queue *q) { }
 static inline void blkcg_exit_queue(struct request_queue *q) { }
+static inline void blkg_destroy_all(struct request_queue *q) { }
 static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
 static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
 static inline int blkcg_activate_policy(struct request_queue *q,
-- 
2.16.2