linux-kernel - Re: [PATCH net-next v5 2/3] net: mirror skb frag ref/unref helpers

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Date: Wed, 10 Apr 2024 12:09:26 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Ayush Sawal <ayush.sawal@...lsio.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, Ilias Apalodimas <ilias.apalodimas@...aro.org>, 
	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>, Dragos Tatulea <dtatulea@...dia.com>
Subject: Re: [PATCH net-next v5 2/3] net: mirror skb frag ref/unref helpers

On Tue, Apr 9, 2024 at 6:23 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Mon,  8 Apr 2024 08:29:57 -0700 Mina Almasry wrote:
> > +#ifdef CONFIG_PAGE_POOL
> > +static inline bool is_pp_page(struct page *page)
> > +{
> > +     return (page->pp_magic & ~0x3UL) == PP_SIGNATURE;
> > +}
> > +
> > +/* page_pool_unref_page() lives in net/page_pool/helpers.h */
> > +static inline void page_pool_ref_page(struct page *page)
> > +{
> > +     atomic_long_inc(&page->pp_ref_count);
> > +}
> > +
> > +static inline 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;
> > +}
> > +#endif
> > +
> > +static inline void skb_page_ref(struct page *page, bool recycle)
> > +{
> > +#ifdef CONFIG_PAGE_POOL
> > +     if (recycle && napi_pp_get_page(page))
> > +             return;
> > +#endif
> > +     get_page(page);
> > +}
>
> Shifting of all this code from pp to skbuff catches the eye.
> There aren't that many callers to these, can we start a new header?

I am not 100% sure what the new header should be named and what
exactly you wanted moved to the new header, but made a guess and
uploaded v6 with this change. Let me know if it's not what you had in
mind. I added a new linux/skbuff_ref.h header file, moved all the ref
functions there, and included page pool headers in that without worry.

v6: https://patchwork.kernel.org/project/netdevbpf/list/?series=843380

> We can then include page pool headers in the without worry.
>
> I'll apply the other patches, they look independent.



-- 
Thanks,
Mina