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

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Date:   Fri, 28 Jul 2023 15:58:58 +0200
From:   Alexander Lobakin <aleksander.lobakin@...el.com>
To:     Yunsheng Lin <linyunsheng@...wei.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>

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())?

> 
>> +{
>> +	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)
>>

Thanks,
Olek