mm: introduce BPF kfuncs to deal with memcg pointers

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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@linux.dev>
Link: https://lore.kernel.org/r/20251223044156.208250-3-roman.gushchin@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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This commit is contained in:

Roman Gushchin 2025-12-22 20:41:52 -08:00 • committed by Alexei Starovoitov

parent 4221de8c41

commit 5904db9891

2 changed files with 91 additions and 0 deletions

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mm/Makefile

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88

mm/bpf_memcontrol.c

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