[PATCH bpf-next v2 0/6] Add Open-coded process and css iters

[Chuyi Zhou]

Hi,

This is version 2 of process and css iters support. All the changes were
suggested by Alexei.

Thanks for your review!

--- Changelog ---
Changes from v1:
- Add a pre-patch to make some preparations before supporting css_task
  iters.
- Add an allowlist for css_task iters
- Let bpf progs do explicit bpf_rcu_read_lock() when using process iters
and css_descendant iters.
---------------------

In some BPF usage scenarios, it will be useful to iterate the process and
css directly in the BPF program. One of the expected scenarios is
customizable OOM victim selection via BPF[1].

Inspired by Dave's task_vma iter[2], this patchset adds three types of
open-coded iterator kfuncs:

1. bpf_for_each(process, p). Just like for_each_process(p) in kernel to
itearing all tasks in the system.

2. bpf_for_each(css_task, task, css). It works like
css_task_iter_{start, next, end} and would be used to iterating
tasks/threads under a css.

3. bpf_for_each(css_{post, pre}, pos, root_css). It works like
css_next_descendant_{pre, post} to iterating all descendant css.

BPF programs can use these kfuncs directly or through bpf_for_each macro.

link[1]: https://lore.kernel.org/lkml/20230810081319.65668-1-zhouchuyi@xxxxxxxxxxxxx/
link[2]: https://lore.kernel.org/all/20230810183513.684836-1-davemarchevsky@xxxxxx/

Chuyi Zhou (6):
  cgroup: Prepare for using css_task_iter_*() in BPF
  bpf: Introduce css_task open-coded iterator kfuncs
  bpf: Introduce process open coded iterator kfuncs
  bpf: Introduce css_descendant open-coded iterator kfuncs
  bpf: teach the verifier to enforce css_iter and process_iter in RCU CS
  selftests/bpf: Add tests for open-coded task and css iter

 include/linux/cgroup.h                        |  12 +-
 include/uapi/linux/bpf.h                      |  16 ++
 kernel/bpf/helpers.c                          |  12 ++
 kernel/bpf/task_iter.c                        | 130 +++++++++++++++++
 kernel/bpf/verifier.c                         |  53 ++++++-
 kernel/cgroup/cgroup.c                        |  18 ++-
 tools/include/uapi/linux/bpf.h                |  16 ++
 tools/lib/bpf/bpf_helpers.h                   |  24 +++
 .../testing/selftests/bpf/prog_tests/iters.c  | 138 ++++++++++++++++++
 .../testing/selftests/bpf/progs/iters_task.c  | 104 +++++++++++++
 10 files changed, 508 insertions(+), 15 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/iters_task.c

-- 
2.20.1