linux-kernel - Re: [PATCH net-next v4 2/3] net: mirror skb frag ref/unref helpers

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Date: Wed, 3 Apr 2024 18:21:19 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Ayush Sawal <ayush.sawal@...lsio.com>, "David S. Miller" <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Steffen Klassert <steffen.klassert@...unet.com>, Herbert Xu <herbert@...dor.apana.org.au>, 
	David Ahern <dsahern@...nel.org>, Boris Pismenny <borisp@...dia.com>, 
	John Fastabend <john.fastabend@...il.com>, Tariq Toukan <tariqt@...dia.com>, 
	Dragos Tatulea <dtatulea@...dia.com>, Simon Horman <horms@...nel.org>, 
	Sabrina Dubroca <sd@...asysnail.net>, 
	Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>, 
	Pavan Chebbi <pavan.chebbi@...adcom.com>, 
	Christophe JAILLET <christophe.jaillet@...adoo.fr>, Yunsheng Lin <linyunsheng@...wei.com>, 
	Florian Westphal <fw@...len.de>, David Howells <dhowells@...hat.com>, 
	Alexander Lobakin <aleksander.lobakin@...el.com>, Lorenzo Bianconi <lorenzo@...nel.org>, 
	Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH net-next v4 2/3] net: mirror skb frag ref/unref helpers

On Wed, Apr 3, 2024 at 5:28 PM Mina Almasry <almasrymina@...gle.com> wrote:
>
> Refactor some of the skb frag ref/unref helpers for improved clarity.
>
> Implement napi_pp_get_page() to be the mirror counterpart of
> napi_pp_put_page().
>
> Implement skb_page_ref() to be the mirror of skb_page_unref().
>
> Improve __skb_frag_ref() to become a mirror counterpart of
> __skb_frag_unref(). Previously unref could handle pp & non-pp pages,
> while the ref could only handle non-pp pages. Now both the ref & unref
> helpers can correctly handle both pp & non-pp pages.
>
> Now that __skb_frag_ref() can handle both pp & non-pp pages, remove
> skb_pp_frag_ref(), and use __skb_frag_ref() instead.  This lets us
> remove pp specific handling from skb_try_coalesce.
>
> Additionally, since __skb_frag_ref() can now handle both pp & non-pp
> pages, a latent issue in skb_shift() should now be fixed. Previously
> this function would do a non-pp ref & pp unref on potential pp frags
> (fragfrom). After this patch, skb_shift() should correctly do a pp
> ref/unref on pp frags.
>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
> Reviewed-by: Dragos Tatulea <dtatulea@...dia.com>
>

..

>  #if IS_ENABLED(CONFIG_PAGE_POOL)
> +bool napi_pp_get_page(struct page *page)
> +{
> +       page = compound_head(page);
> +
> +       if (!is_pp_page(page))
> +               return false;
> +
> +       page_pool_ref_page(page);
> +       return true;
> +}
> +EXPORT_SYMBOL(napi_pp_get_page);

It seems this could be inlined (along with is_pp_page())