Re: [PATCH] mm: workingset: fix NULL ptr in count_shadow_nodes

[Balbir Singh]

On Fri, Dec 2, 2016 at 12:21 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> 0a6b76dd23fa ("mm: workingset: make shadow node shrinker memcg aware")
> has made the workingset shadow nodes shrinker memcg aware. The
> implementation is not correct though because memcg_kmem_enabled() might
> become true while we are doing a global reclaim when the sc->memcg might
> be NULL which is exactly what Marek has seen:
>
<snip>
>
> -       if (memcg_kmem_enabled()) {
> +       if (sc->memcg) {
>                 pages = mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid,
>                                                      LRU_ALL_FILE);
>         } else {

Acked-by: Balbir Singh <bsingharora@xxxxxxxxx>