linux-kernel - Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing programs

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Date:   Mon, 11 Jan 2021 09:16:33 -0800
From:   Yonghong Song <yhs@...com>
To:     Song Liu <songliubraving@...com>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <mingo@...hat.com>, <peterz@...radead.org>, <ast@...nel.org>,
        <daniel@...earbox.net>, <andrii@...nel.org>,
        <john.fastabend@...il.com>, <kpsingh@...omium.org>,
        <kernel-team@...com>, <haoluo@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH bpf-next 1/4] bpf: enable task local storage for tracing
 programs



On 1/8/21 3:19 PM, Song Liu wrote:
> To access per-task data, BPF program typically creates a hash table with
> pid as the key. This is not ideal because:
>   1. The use need to estimate requires size of the hash table, with may be
>      inaccurate;
>   2. Big hash tables are slow;
>   3. To clean up the data properly during task terminations, the user need
>      to write code.
> 
> Task local storage overcomes these issues and becomes a better option for
> these per-task data. Task local storage is only available to BPF_LSM. Now
> enable it for tracing programs.
> 
> Reported-by: kernel test robot <lkp@...el.com>

The whole patch is not reported by kernel test robot. I think we should
drop this.

> Signed-off-by: Song Liu <songliubraving@...com>
> ---
>   include/linux/bpf.h            |  7 +++++++
>   include/linux/bpf_lsm.h        | 22 ----------------------
>   include/linux/bpf_types.h      |  2 +-
>   include/linux/sched.h          |  5 +++++
>   kernel/bpf/Makefile            |  3 +--
>   kernel/bpf/bpf_local_storage.c | 28 +++++++++++++++++-----------
>   kernel/bpf/bpf_lsm.c           |  4 ----
>   kernel/bpf/bpf_task_storage.c  | 26 ++++++--------------------
>   kernel/fork.c                  |  5 +++++
>   kernel/trace/bpf_trace.c       |  4 ++++
>   10 files changed, 46 insertions(+), 60 deletions(-)
> 
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 07cb5d15e7439..cf16548f28f7b 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1480,6 +1480,7 @@ struct bpf_prog *bpf_prog_by_id(u32 id);
>   struct bpf_link *bpf_link_by_id(u32 id);
>   
>   const struct bpf_func_proto *bpf_base_func_proto(enum bpf_func_id func_id);
> +void bpf_task_storage_free(struct task_struct *task);
>   #else /* !CONFIG_BPF_SYSCALL */
>   static inline struct bpf_prog *bpf_prog_get(u32 ufd)
>   {
> @@ -1665,6 +1666,10 @@ bpf_base_func_proto(enum bpf_func_id func_id)
>   {
>   	return NULL;
>   }
> +
> +static inline void bpf_task_storage_free(struct task_struct *task)
> +{
> +}
>   #endif /* CONFIG_BPF_SYSCALL */
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