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

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Message-ID: <09a0a33a-57c5-a81d-1b5b-982aa0e0441d@bytedance.com>
Date:   Tue, 12 Sep 2023 15:11:47 +0800
From:   Chuyi Zhou <zhouchuyi@...edance.com>
To:     bpf@...r.kernel.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...nel.org, tj@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 0/6] Add Open-coded process and css iters



在 2023/9/12 15:01, Chuyi Zhou 写道:
> 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.

Sorry for missing the link to v1 
(https://lore.kernel.org/lkml/20230827072057.1591929-1-zhouchuyi@bytedance.com/).


> ---------------------
> 
> 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@bytedance.com/
> link[2]: https://lore.kernel.org/all/20230810183513.684836-1-davemarchevsky@fb.com/
> 
> 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
>