[PATCH 17/24] blkcg: implement blkcg_policy->on/offline_pd_fn() and blkcg_gq->online

[Vivek Goyal]

On Fri, Dec 28, 2012 at 12:35:39PM -0800, Tejun Heo wrote:

[..]
> diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
> index 40f5b97..678e89e 100644
> --- a/block/blk-cgroup.h
> +++ b/block/blk-cgroup.h
> @@ -106,12 +106,17 @@ struct blkcg_gq {
>  	/* reference count */
>  	int				refcnt;
>  
> +	/* is this blkg online? protected by both blkcg and q locks */
> +	bool				online;
> +

Hi Tejun,

What does above mean? One needs to take one lock or both the locks to
check/modify blkg->online.

Thanks
Vivek