linux-kernel - Re: memcg causes crashes in list_lru

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Date:   Mon, 29 Apr 2019 12:40:51 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Jiri Slaby <jslaby@...e.cz>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, mm <linux-mm@...ck.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: memcg causes crashes in list_lru_add

On Mon 29-04-19 12:09:53, Jiri Slaby wrote:
> On 29. 04. 19, 11:25, Jiri Slaby wrote:> memcg_update_all_list_lrus
> should take care about resizing the array.
> 
> It should, but:
> [    0.058362] Number of physical nodes 2
> [    0.058366] Skipping disabled node 0
> 
> So this should be the real fix:
> --- linux-5.0-stable1.orig/mm/list_lru.c
> +++ linux-5.0-stable1/mm/list_lru.c
> @@ -37,11 +37,12 @@ static int lru_shrinker_id(struct list_l
> 
>  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;
> +       int i;
> +
> +       for_each_online_node(i)
> +               return !!lru->node[i].memcg_lrus;
> +
> +       return false;
>  }
> 
>  static inline struct list_lru_one *
> 
> 
> 
> 
> 
> Opinions?

Please report upstream. This code here is there for quite some time.
I do not really remember why we do have an assumption about node 0
and why it hasn't been problem until now.

Thanks!
-- 
Michal Hocko
SUSE Labs