linux-kernel - Re: [RFC PATCH v3 08/12] net: support non paged skb frags

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Date:   Thu, 9 Nov 2023 20:06:00 -0800
From:   Mina Almasry <almasrymina@...gle.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        David Ahern <dsahern@...nel.org>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jeroen de Borst <jeroendb@...gle.com>,
        Praveen Kaligineedi <pkaligineedi@...gle.com>
Subject: Re: [RFC PATCH v3 08/12] net: support non paged skb frags

On Thu, Nov 9, 2023 at 1:15 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On Sun, 2023-11-05 at 18:44 -0800, Mina Almasry wrote:
> [...]
> > @@ -3421,7 +3446,7 @@ static inline struct page *skb_frag_page(const skb_frag_t *frag)
> >   */
> >  static inline void __skb_frag_ref(skb_frag_t *frag)
> >  {
> > -     get_page(skb_frag_page(frag));
> > +     page_pool_page_get_many(frag->bv_page, 1);
>
> I guess the above needs #ifdef CONFIG_PAGE_POOL guards and explicit
> skb_frag_is_page_pool_iov() check ?
>

It doesn't actually. page_pool_page_* helpers are compiled in
regardless of CONFIG_PAGE_POOL, and handle both page_pool_iov* & page*
just fine (the checking happens inside the function).

You may yell at me that it's too confusing... I somewhat agree, but
I'm unsure of what is a better name or location for the helpers. The
helpers handle (page_pool_iov* || page*) gracefully, so they seem to
belong in the page pool for me, but it is indeed surprising/confusing
that these helpers are available even if !CONFIG_PAGE_POOL.

>
> Cheers,
>
> Paolo
>
>


-- 
Thanks,
Mina