linux-kernel - Re: [PATCH] memcg: make it work on sparse non-0-node systems

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Date:   Mon, 29 Apr 2019 07:30:22 -0400
From:   Michal Hocko <mhocko@...nel.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org,
        Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
Subject: Re: [PATCH] memcg: make it work on sparse non-0-node systems

On Mon 29-04-19 12:59:39, Jiri Slaby wrote:
[...]
>  static inline bool list_lru_memcg_aware(struct list_lru *lru)
>  {
> -	/*
> -	 * This needs node 0 to be always present, even
> -	 * in the systems supporting sparse numa ids.
> -	 */
> -	return !!lru->node[0].memcg_lrus;
> +	return !!lru->node[first_online_node].memcg_lrus;
>  }
>  
>  static inline struct list_lru_one *

How come this doesn't blow up later - e.g. in memcg_destroy_list_lru
path which does iterate over all existing nodes thus including the
node 0.
-- 
Michal Hocko
SUSE Labs