[dm-devel] Re: [PATCH 07/18] io-controller: Export disk time used and nr sectors dipatched through cgroups

[Gui Jianfeng <guijianfeng cn fujitsu com>]

Vivek Goyal wrote:
...
>  
> +/*
> + * traverse through all the io_groups associated with this cgroup and calculate
> + * the aggr disk time received by all the groups on respective disks.
> + */
> +static u64 calculate_aggr_disk_time(struct io_cgroup *iocg)
> +{
> +	struct io_group *iog;
> +	struct hlist_node *n;
> +	u64 disk_time = 0;
> +
> +	rcu_read_lock();

  This function is in slow-path, so no need to call rcu_read_lock(), just need to ensure
  that the caller already holds the iocg->lock.

> +	hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
> +		/*
> +		 * There might be groups which are not functional and
> +		 * waiting to be reclaimed upon cgoup deletion.
> +		 */
> +		if (rcu_dereference(iog->key))
> +			disk_time += iog->entity.total_service;
> +	}
> +	rcu_read_unlock();
> +
> +	return disk_time;
> +}
> +

-- 
Regards
Gui Jianfeng