linux-kernel - Re: [PATCH v11 02/14] cgroup/misc: Add per resource callbacks for CSS events

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Date: Mon, 15 Apr 2024 13:43:46 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "hpa@...or.com" <hpa@...or.com>, "tim.c.chen@...ux.intel.com"
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	"chrisyan@...rosoft.com" <chrisyan@...rosoft.com>
Subject: Re: [PATCH v11 02/14] cgroup/misc: Add per resource callbacks for CSS
 events

On Wed, 2024-04-10 at 11:25 -0700, Haitao Huang wrote:
> From: Kristen Carlson Accardi <kristen@...ux.intel.com>
> 
> The misc cgroup controller (subsystem) currently does not perform
> resource type specific action for Cgroups Subsystem State (CSS) events:
> the 'css_alloc' event when a cgroup is created and the 'css_free' event
> when a cgroup is destroyed.
> 
> Define callbacks for those events and allow resource providers to
> register the callbacks per resource type as needed. This will be
> utilized later by the EPC misc cgroup support implemented in the SGX
> driver.
> 
> Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
> Co-developed-by: Haitao Huang <haitao.huang@...ux.intel.com>
> Signed-off-by: Haitao Huang <haitao.huang@...ux.intel.com>
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
> Reviewed-by: Tejun Heo <tj@...nel.org>
> 

Reviewed-by: Kai Huang <kai.huang@...el.com>

Nitpickings below:

>  
> +/**
> + * struct misc_res_ops: per resource type callback ops.
> + * @alloc: invoked for resource specific initialization when cgroup is allocated.
> + * @free: invoked for resource specific cleanup when cgroup is deallocated.
> + */
> +struct misc_res_ops {
> +	int (*alloc)(struct misc_cg *cg);
> +	void (*free)(struct misc_cg *cg);
> +};
> +

Perhaps you can mention why you take 'struct misc_cg *cg' as parameter, but not
'struct misc_res *res' to the changelog.  

It's not very clear in this patch.


[...]

>  static struct cgroup_subsys_state *
>  misc_cg_alloc(struct cgroup_subsys_state *parent_css)
>  {
> -	enum misc_res_type i;
> -	struct misc_cg *cg;
> +	struct misc_cg *parent_cg, *cg;
> +	int ret;
>  
> -	if (!parent_css) {
> -		cg = &root_cg;
> +	if (unlikely(!parent_css)) {
> +		parent_cg = cg = &root_cg;

Seems the 'unlikely' is new.

I think you can remove it because it's not something that is related to this
patch.