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

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Date: Fri, 28 Jul 2023 20:02:51 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
CC: 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 2023/7/27 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()?

> +{
> +	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)
>  {
>  	if (!IS_ENABLED(CONFIG_PAGE_POOL) || !skb->pp_recycle)
>