Date:   Wed, 5 Jan 2022 20:35:04 +0100
From:   Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>
To:     Wei Yang <richard.weiyang@gmail.com>
Cc:     tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] cgroup/rstat: check updated_next only for root
Message-ID: <20220105193504.GD6464@blackbody.suse.cz>
References: <20211225000932.7253-1-richard.weiyang@gmail.com>
 <20211225000932.7253-2-richard.weiyang@gmail.com>
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On Sat, Dec 25, 2021 at 12:09:32AM +0000, Wei Yang <richard.weiyang@gmail.com> wrote:
> This means we can remove the check on ->updated_next, if we make sure
> the subtree from @root is on list, which could be done by checking
> updated_next for root.

Nice refactoring.

> @@ -96,9 +97,12 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
>  	 * We're gonna walk down to the first leaf and visit/remove it.  We
>  	 * can pick whatever unvisited node as the starting point.
>  	 */
> -	if (!pos)
> +	if (!pos) {
>  		pos = root;
> -	else
> +		// return NULL if this subtree is not on-list
> +		if (!cgroup_rstat_cpu(pos, cpu)->updated_next)
> +			return NULL;
> +	} else
+		/* return NULL if this subtree is not on-list */

Just a coding style nitpick.

The patch is otherwise
Reviewed-by: Michal Koutn? <mkoutny@suse.com>