Re: [PATCH 4/5] mm, memcg: avoid possible NULL pointer dereferencing in mem_cgroup_init()

[Matthew Wilcox]

On Thu, Jul 29, 2021 at 08:57:54PM +0800, Miaohe Lin wrote:
> rtpn might be NULL in very rare case. We have better to check it before
> dereferencing it. Since memcg can live with NULL rb_tree_per_node in
> soft_limit_tree, warn this case and continue.

Why would we need to warn?  the GFP flags don't contain NOWARN, so
we already know an allocation failed.