block: RCU free request_queue

RCU free request_queue so that blkcg_gq->q can be dereferenced under
RCU lock.  This will be used to implement hierarchical stats.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 788147797a79..6206a934eb8c 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -497,6 +497,13 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr,
         return res;
 }
 
+static void blk_free_queue_rcu(struct rcu_head *rcu_head)
+{
+        struct request_queue *q = container_of(rcu_head, struct request_queue,
+                                               rcu_head);
+        kmem_cache_free(blk_requestq_cachep, q);
+}
+
 /**
  * blk_release_queue: - release a &struct request_queue when it is no longer needed
  * @kobj:    the kobj belonging to the request queue to be released
@@ -538,7 +545,7 @@ static void blk_release_queue(struct kobject *kobj)
         bdi_destroy(&q->backing_dev_info);
 
         ida_simple_remove(&blk_queue_ida, q->id);
-        kmem_cache_free(blk_requestq_cachep, q);
+        call_rcu(&q->rcu_head, blk_free_queue_rcu);
 }
 
 static const struct sysfs_ops queue_sysfs_ops = {