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>

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 788147797a798b0041e8d3fa3bf70955016b0915..6206a934eb8c85a2f21636759f1b64afe8e3fb70 100644 (file)
--- 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 = {

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f94bc83011ed5c7a3c96f0adabefa1246f86cb47..406343c43cdaf35bb54c0b51bb00f6b759e22014 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -19,6 +19,7 @@
 #include <linux/gfp.h>
 #include <linux/bsg.h>
 #include <linux/smp.h>
+#include <linux/rcupdate.h>
 
 #include <asm/scatterlist.h>
 
@@ -437,6 +438,7 @@ struct request_queue {
        /* Throttle data */
        struct throtl_data *td;
 #endif
+       struct rcu_head         rcu_head;
 };
 
 #define QUEUE_FLAG_QUEUED      1       /* uses generic tag queueing */