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Message-ID: <5b301151-0a65-df43-3a3a-6d57e10cfc2d@fb.com>
Date:   Fri, 20 May 2022 17:59:21 -0700
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Subject: Re: [PATCH bpf-next v1 3/5] bpf: Introduce cgroup iter
Content-Language: en-US
To:     Tejun Heo <tj@kernel.org>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc:     Yosry Ahmed <yosryahmed@google.com>, Hao Luo <haoluo@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>,
        Cgroups <cgroups@vger.kernel.org>
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From:   Yonghong Song <yhs@fb.com>
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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!

> 
> Thanks.
>