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Subject[PATCH 20/24] block: RCU free request_queue
Date
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>
---
block/blk-sysfs.c | 9 ++++++++-
include/linux/blkdev.h | 2 ++
2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 7881477..6206a93 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 = {
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f94bc83..406343c 100644
--- 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 */
--
1.8.0.2


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