linux-kernel - Re: [PATCH net-next 2/9] net: skbuff: don't include <net/page

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Date:   Sat, 29 Jul 2023 19:40:19 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Alexander Lobakin <aleksander.lobakin@...el.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Simon Horman <simon.horman@...igine.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 2/9] net: skbuff: don't include
 <net/page_pool/types.h> to <linux/skbuff.h>

On 2023/7/28 21:58, Alexander Lobakin wrote:
> From: Yunsheng Lin <linyunsheng@...wei.com>
> Date: Fri, 28 Jul 2023 20:02:51 +0800
> 
>> On 2023/7/27 22:43, Alexander Lobakin wrote:
>>> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
>>
>> ...
>>
>>> +bool page_pool_return_skb_page(struct page *page, bool napi_safe)
>>
>> Still having the 'page_pool_' prefix seems odd here when it is in the
>> skbuff.c where most have skb_ or napi_ prefix, is it better to rename
>> it to something like napi_return_page_pool_page()?
> 
> Given that how the function that goes next is named, maybe
> skb_pp_return_page() (or skb_pp_put_page())?

skb_pp_put_page() seems better.

And I like napi_pp_put_page() with 'napi_' prefix better as
it does not take a skb as parameter and the naming is aligned
with the 'napi_safe' parameter.

> 
>>
>>> +{
>>> +	struct napi_struct *napi;
>>> +	struct page_pool *pp;
>>> +	bool allow_direct;
>>> +
>>> +	page = compound_head(page);
>>> +
>>> +	/* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
>>> +	 * in order to preserve any existing bits, such as bit 0 for the
>>> +	 * head page of compound page and bit 1 for pfmemalloc page, so
>>> +	 * mask those bits for freeing side when doing below checking,
>>> +	 * and page_is_pfmemalloc() is checked in __page_pool_put_page()
>>> +	 * to avoid recycling the pfmemalloc page.
>>> +	 */
>>> +	if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
>>> +		return false;
>>> +
>>> +	pp = page->pp;
>>> +
>>> +	/* Allow direct recycle if we have reasons to believe that we are
>>> +	 * in the same context as the consumer would run, so there's
>>> +	 * no possible race.
>>> +	 */
>>> +	napi = READ_ONCE(pp->p.napi);
>>> +	allow_direct = napi_safe && napi &&
>>> +		READ_ONCE(napi->list_owner) == smp_processor_id();
>>> +
>>> +	/* Driver set this to memory recycling info. Reset it on recycle.
>>> +	 * This will *not* work for NIC using a split-page memory model.
>>> +	 * The page will be returned to the pool here regardless of the
>>> +	 * 'flipped' fragment being in use or not.
>>> +	 */
>>> +	page_pool_put_full_page(pp, page, allow_direct);
>>> +
>>> +	return true;
>>> +}
>>> +EXPORT_SYMBOL(page_pool_return_skb_page);
>>> +
>>>  static bool skb_pp_recycle(struct sk_buff *skb, void *data, bool napi_safe)
> 
> (this one)
> 
>>>  {
>>>  	if (!IS_ENABLED(CONFIG_PAGE_POOL) || !skb->pp_recycle)

We may need the 'IS_ENABLED(CONFIG_PAGE_POOL' checking in the newly
moved function too.

>>>
> 
> Thanks,
> Olek
> 
> .
>