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From:   Hao Luo <haoluo@google.com>
Date:   Fri, 20 May 2022 19:34:45 -0700
Message-ID: <CA+khW7gGrwTrDsfWp7wj=QaCg01FNj381a1QLs1ThsjAkW85eQ@mail.gmail.com>
Subject: Re: [PATCH bpf-next v1 3/5] bpf: Introduce cgroup iter
To:     Yonghong Song <yhs@fb.com>
Cc:     Tejun Heo <tj@kernel.org>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Yosry Ahmed <yosryahmed@google.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Zefan Li <lizefan.x@bytedance.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shuah Khan <shuah@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Michal Hocko <mhocko@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        David Rientjes <rientjes@google.com>,
        Greg Thelen <gthelen@google.com>,
        Shakeel Butt <shakeelb@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
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On Fri, May 20, 2022 at 5:59 PM Yonghong Song <yhs@fb.com> wrote:
> On 5/20/22 3:57 PM, Tejun Heo wrote:
> > Hello,
> >
> > On Fri, May 20, 2022 at 03:19:19PM -0700, Alexei Starovoitov wrote:
> >> We have bpf_map iterator that walks all bpf maps.
> >> When map iterator is parametrized with map_fd the iterator walks
> >> all elements of that map.
> >> cgroup iterator should have similar semantics.
> >> When non-parameterized it will walk all cgroups and their descendent
> >> depth first way. I believe that's what Yonghong is proposing.
> >> When parametrized it will start from that particular cgroup and
> >> walk all descendant of that cgroup only.
> >> The bpf prog can stop the iteration right away with ret 1.
> >> Maybe we can add two parameters. One -> cgroup_fd to use and another ->
> >> the order of iteration css_for_each_descendant_pre vs _post.
> >> wdyt?
> >
> > Sounds perfectly reasonable to me.
>
> This works for me too. Thanks!
>

This sounds good to me. Thanks. Let's try to do it in the next iteration.