Re: [PATCH bpf-next v2 2/7] mm: introduce BPF kfuncs to deal with memcg pointers

[Shakeel Butt]

On Fri, Dec 19, 2025 at 08:12:45PM -0800, Roman Gushchin wrote:
> To effectively operate with memory cgroups in BPF there is a need
> to convert css pointers to memcg pointers. A simple container_of
> cast which is used in the kernel code can't be used in BPF because
> from the verifier's point of view that's a out-of-bounds memory access.
> 
> Introduce helper get/put kfuncs which can be used to get
> a refcounted memcg pointer from the css pointer:
>   - bpf_get_mem_cgroup,
>   - bpf_put_mem_cgroup.
> 
> bpf_get_mem_cgroup() can take both memcg's css and the corresponding
> cgroup's "self" css. It allows it to be used with the existing cgroup
> iterator which iterates over cgroup tree, not memcg tree.
> 
> Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>

Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>