netdev - Re: [PATCH bpf-next v3 06/21] bpf: create anonymous bpf iterator

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Message-ID: <CAEf4Bzb8YhqZM4UM8z3kYRLYCFsk96rdPCkK9JT2ZpkL9KGn2w@mail.gmail.com>
Date:   Fri, 8 May 2020 11:57:34 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH bpf-next v3 06/21] bpf: create anonymous bpf iterator

On Wed, May 6, 2020 at 10:39 PM Yonghong Song <yhs@...com> wrote:
>
> A new bpf command BPF_ITER_CREATE is added.
>
> The anonymous bpf iterator is seq_file based.
> The seq_file private data are referenced by targets.
> The bpf_iter infrastructure allocated additional space
> at seq_file->private before the space used by targets
> to store some meta data, e.g.,
>   prog:       prog to run
>   session_id: an unique id for each opened seq_file
>   seq_num:    how many times bpf programs are queried in this session
>   done_stop:  an internal state to decide whether bpf program
>               should be called in seq_ops->stop() or not
>
> The seq_num will start from 0 for valid objects.
> The bpf program may see the same seq_num more than once if
>  - seq_file buffer overflow happens and the same object
>    is retried by bpf_seq_read(), or
>  - the bpf program explicitly requests a retry of the
>    same object
>
> Since module is not supported for bpf_iter, all target
> registeration happens at __init time, so there is no
> need to change bpf_iter_unreg_target() as it is used
> mostly in error path of the init function at which time
> no bpf iterators have been created yet.
>
> Signed-off-by: Yonghong Song <yhs@...com>
> ---

LGTM.

Acked-by: Andrii Nakryiko <andriin@...com>

>  include/linux/bpf.h            |   1 +
>  include/uapi/linux/bpf.h       |   6 ++
>  kernel/bpf/bpf_iter.c          | 129 +++++++++++++++++++++++++++++++++
>  kernel/bpf/syscall.c           |  26 +++++++
>  tools/include/uapi/linux/bpf.h |   6 ++
>  5 files changed, 168 insertions(+)
>

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