On Thu, Dec 01, 2016 at 02:21:56PM +0100, Michal Hocko wrote:
> From: Michal Hocko <mho...@suse.com>
> 
> 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:

[...]

> This patch fixes the issue by checking sc->memcg rather than 
> memcg_kmem_enabled()
> which is sufficient because shrink_slab makes sure that only memcg aware 
> shrinkers
> will get non-NULL memcgs and only if memcg_kmem_enabled is true.
> 
> Fixes: 0a6b76dd23fa ("mm: workingset: make shadow node shrinker memcg aware")
> Reported-and-tested-by: Marek Marczykowski-Górecki <marma...@mimuw.edu.pl>
> Cc: sta...@vger.kernel.org # 4.6+
> Signed-off-by: Michal Hocko <mho...@suse.com>

Acked-by: Johannes Weiner <han...@cmpxchg.org>

Thanks Michal

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