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

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Message-ID: <87zgp9wyvc.fsf@toke.dk>
Date:   Thu, 09 Dec 2021 17:01:59 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     John Fastabend <john.fastabend@...il.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:     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

John Fastabend <john.fastabend@...il.com> writes:

> 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.

Yeah, fair point, may have gone a little overboard on the "minimise
impact to existing code" here - will drop.

-Toke