Re: [PATCH] mm: memcontrol-v1: use nofail allocations for soft limit trees

[Michal Hocko]

On Mon 08-06-26 16:34:48, Ruoyu Wang wrote:
> No, I have not observed this allocation failing in practice.
> 
> This was found by static analysis and then checked by reading the code:
> memcg1_init() dereferences rtpn unconditionally after kzalloc_node(). I
> treated the soft-limit tree as mandatory memcg v1 init state and used
> __GFP_NOFAIL because continuing without it would not be useful.

This should have been part of the changelog because it provides an
insight into how have you reached your conclusion.

> I agree this is early boot init code, and I do not have a
> runtime failure report or fault-injection reproduction for it. If such
> allocations are considered not worth handling in this path, feel
> free to drop the patch.

Yes, there is simply no point in handling these failures because early
allocation failure like this one would very likely lead to massive
failure before userspace is brought up anyway so there is no practical
way to trigger the NULL ptr.

-- 
Michal Hocko
SUSE Labs