netdev - RE: [PATCH bpf-next 1/8] page_pool: Add callback to init pages when they are allocated

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Date:   Wed, 08 Dec 2021 14:30:08 -0800
From:   John Fastabend <john.fastabend@...il.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        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>
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: RE: [PATCH bpf-next 1/8] page_pool: Add callback to init pages when
 they are allocated

Toke Høiland-Jørgensen wrote:
> Add a new callback function to page_pool that, if set, will be called every
> time a new page is allocated. This will be used from bpf_test_run() to
> initialise the page data with the data provided by userspace when running
> XDP programs with redirect turned on.
> 
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---

LGTM.

Acked-by: John Fastabend <john.fastabend@...il.com>

>  include/net/page_pool.h | 2 ++
>  net/core/page_pool.c    | 2 ++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/include/net/page_pool.h b/include/net/page_pool.h
> index 3855f069627f..a71201854c41 100644
> --- a/include/net/page_pool.h
> +++ b/include/net/page_pool.h
> @@ -80,6 +80,8 @@ struct page_pool_params {
>  	enum dma_data_direction dma_dir; /* DMA mapping direction */
>  	unsigned int	max_len; /* max DMA sync memory size */
>  	unsigned int	offset;  /* DMA addr offset */
> +	void (*init_callback)(struct page *page, void *arg);
> +	void *init_arg;
>  };
>  
>  struct page_pool {
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index 9b60e4301a44..fb5a90b9d574 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -219,6 +219,8 @@ static void page_pool_set_pp_info(struct page_pool *pool,
>  {
>  	page->pp = pool;
>  	page->pp_magic |= PP_SIGNATURE;
> +	if (unlikely(pool->p.init_callback))
> +		pool->p.init_callback(page, pool->p.init_arg);

already in slow path right? So unlikely in a slow path should not
have any impact on performance is my reading.

>  }
>  
>  static void page_pool_clear_pp_info(struct page *page)
> -- 
> 2.34.0
>