Re: [PATCH v2 2/2] cgroup, kernfs: Move cgroup to the RCU interface for name lookups

[Tejun Heo <tj@kernel.org>]

Hello,

On Tue, Nov 12, 2024 at 04:52:39PM +0100, Sebastian Andrzej Siewior wrote:
...
>  /**
> - * pr_cont_kernfs_name - pr_cont name of a kernfs_node
> + * pr_cont_kernfs_name_rcu - pr_cont name of a kernfs_node
>   * @kn: kernfs_node of interest
>   *
> - * This function can be called from any context.
> + * This function can be called from any context. The root node must be with
> + * KERNFS_ROOT_SAME_PARENT.
>   */
> -void pr_cont_kernfs_name(struct kernfs_node *kn)
> +void pr_cont_kernfs_name_rcu(struct kernfs_node *kn)

Having to split the interface all the way up isn't great. While there are
also downsides, I wonder whether a better approach here is just making the
backend function (kernfs_path_from_node()) automatically use RCU locking if
the flag is set rather than propagating the difference by splitting the
interface. The distinction doesn't mean anything to most users after all.

Thanks.

-- 
tejun