linux-kernel - Re: [PATCH] cgroup: Delete unnecessary if statement in css

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Message-ID: <20201001144426.GA8928@haolee.github.io>
Date:   Thu, 1 Oct 2020 14:44:26 +0000
From:   Hao Lee <haolee.swjtu@...il.com>
To:     tj@...nel.org
Cc:     lizefan@...wei.com, hannes@...xchg.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cgroup: Delete unnecessary if statement in css_visible()

Hi, ping...

On Sat, Aug 29, 2020 at 10:03:16AM +0000, Hao Lee wrote:
> css_visible() is called in either cgroup_apply_control_enable()
> or cgroup_apply_control_disable().
> In cgroup_apply_control_enable(), we have checked ss_mask before calling
> css_visible(), so there is no need to do the same thing again.
> In cgroup_apply_control_disable():
>  - If css->parent is not NULL, we have checked ss_mask in the
>    second condition, so there is no need to do the same thing again.
>  - If css->parent is NULL, dsct is root cgroup so the deleted if
>    statement is always false and there is no need to keep it.
> 
> Signed-off-by: Hao Lee <haolee.swjtu@...il.com>
> ---
>  kernel/cgroup/cgroup.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index dd247747ec14..b6714166106d 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -3023,8 +3023,6 @@ static bool css_visible(struct cgroup_subsys_state *css)
>  
>  	if (cgroup_control(cgrp) & (1 << ss->id))
>  		return true;
> -	if (!(cgroup_ss_mask(cgrp) & (1 << ss->id)))
> -		return false;
>  	return cgroup_on_dfl(cgrp) && ss->implicit_on_dfl;
>  }
>  
> -- 
> 2.24.1
>