On Fri, Dec 28, 2012 at 12:35:42PM -0800, Tejun Heo wrote:
> 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@xxxxxxxxxx>
Acked-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
Vivek
> ---
> 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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