linux-kernel - Re: [bpf-next 1/3] bpf: Move bpf_prog_clone

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Date:   Wed, 7 Jul 2021 00:02:52 -0700
From:   Song Liu <song@...nel.org>
To:     He Fengqing <hefengqing@...wei.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [bpf-next 1/3] bpf: Move bpf_prog_clone_free into filter.h file

On Tue, Jul 6, 2021 at 8:53 PM He Fengqing <hefengqing@...wei.com> wrote:
>
> Move bpf_prog_clone_free function into filter.h, so we can use
> it in other file.
>
> Signed-off-by: He Fengqing <hefengqing@...wei.com>
> ---
>  include/linux/filter.h | 15 +++++++++++++++
>  kernel/bpf/core.c      | 20 +-------------------
>  2 files changed, 16 insertions(+), 19 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 472f97074da0..f39e008a377d 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -884,6 +884,21 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
>                                   gfp_t gfp_extra_flags);
>  void __bpf_prog_free(struct bpf_prog *fp);
>
> +static inline void bpf_prog_clone_free(struct bpf_prog *fp)
> +{
> +       /* aux was stolen by the other clone, so we cannot free
> +        * it from this path! It will be freed eventually by the
> +        * other program on release.
> +        *
> +        * At this point, we don't need a deferred release since
> +        * clone is guaranteed to not be locked.
> +        */
> +       fp->aux = NULL;
> +       fp->stats = NULL;
> +       fp->active = NULL;
> +       __bpf_prog_free(fp);
> +}
> +
>  static inline void bpf_prog_unlock_free(struct bpf_prog *fp)
>  {
>         __bpf_prog_free(fp);
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 034ad93a1ad7..49b0311f48c1 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -238,10 +238,7 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
>                 /* We keep fp->aux from fp_old around in the new
>                  * reallocated structure.
>                  */
After the change, we can remove the comment above.

> -               fp_old->aux = NULL;
> -               fp_old->stats = NULL;
> -               fp_old->active = NULL;
> -               __bpf_prog_free(fp_old);
> +               bpf_prog_clone_free(fp_old);

Please add a couple sentences in the commit log about this chanage.

Thanks,
Song