[PATCH bpf-next 0/3] bpf: Expand bpf_cgrp_storage to support cgroup1 non-attach case

[Yafang Shao <laoar.shao@gmail.com>]

In the current cgroup1 environment, associating operations between a cgroup
and applications in a BPF program requires storing a mapping of cgroup_id
to application either in a hash map or maintaining it in userspace.
However, by enabling bpf_cgrp_storage for cgroup1, it becomes possible to
conveniently store application-specific information in cgroup-local storage
and utilize it within BPF programs. Furthermore, enabling this feature for
cgroup1 involves minor modifications for the non-attach case, streamlining
the process.

However, when it comes to enabling this functionality for the cgroup1
attach case, it presents challenges. Therefore, the decision is to focus on
enabling it solely for the cgroup1 non-attach case at present. If
attempting to attach to a cgroup1 fd, the operation will simply fail with
the error code -EBADF.

Changes:
- RFC -> v1:
  - Collect acked-by
  - Avoid unnecessary is_cgroup1 check (Yonghong)
  - Keep the code patterns consistent (Yonghong)

Yafang Shao (3):
  bpf: Enable bpf_cgrp_storage for cgroup1 non-attach case
  selftests/bpf: Add a new cgroup helper open_classid()
  selftests/bpf: Add selftests for cgroup1 local storage

 kernel/bpf/bpf_cgrp_storage.c                      |  6 +-
 tools/testing/selftests/bpf/cgroup_helpers.c       | 16 ++++
 tools/testing/selftests/bpf/cgroup_helpers.h       |  1 +
 .../selftests/bpf/prog_tests/cgrp_local_storage.c  | 98 +++++++++++++++++++++-
 .../selftests/bpf/progs/cgrp_ls_recursion.c        | 84 +++++++++++++++----
 .../selftests/bpf/progs/cgrp_ls_sleepable.c        | 61 ++++++++++++--
 tools/testing/selftests/bpf/progs/cgrp_ls_tp_btf.c | 82 +++++++++++++-----
 7 files changed, 298 insertions(+), 50 deletions(-)

-- 
1.8.3.1