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Date:   Mon, 29 Apr 2019 07:30:22 -0400
From:   Michal Hocko <mhocko@kernel.org>
To:     Jiri Slaby <jslaby@suse.cz>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Johannes Weiner <hannes@cmpxchg.org>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        cgroups@vger.kernel.org,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
Subject: Re: [PATCH] memcg: make it work on sparse non-0-node systems
Message-ID: <20190429112916.GI21837@dhcp22.suse.cz>
References: <359d98e6-044a-7686-8522-bdd2489e9456@suse.cz>
 <20190429105939.11962-1-jslaby@suse.cz>
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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