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Date: Wed, 10 Jul 2024 18:22:02 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Mina Almasry <almasrymina@google.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
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Subject: Re: [PATCH net-next v16 05/13] page_pool: devmem support
Message-ID: <20240710182202.0324279f@kernel.org>
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On Wed, 10 Jul 2024 13:29:03 -0700 Mina Almasry wrote:
> If we want to add __skb_frag_ref() support for net_iov I suggest something like:
> 
> diff --git a/include/linux/skbuff_ref.h b/include/linux/skbuff_ref.h
> index 0f3c58007488a..02f7f4c7d4821 100644
> --- a/include/linux/skbuff_ref.h
> +++ b/include/linux/skbuff_ref.h
> @@ -17,7 +17,13 @@
>   */
>  static inline void __skb_frag_ref(skb_frag_t *frag)
>  {
> -       get_page(skb_frag_page(frag));
> +       netmem_ref netmem = skb_frag_netmem(frag);
> +
> +       /* netmem always uses pp-refs for refcounting. Never non-pp refs. */
> +       if (!netmem_is_net_iov(netmem))
> +               get_page(netmem_to_page(netmem));
> +       else
> +               page_pool_ref_netmem(netmem);
>  }

Probably not much better since freeing still looks at the recycle bit.
Eric and Willem acked patch 8, maybe it works, and if it doesn't we
know who to call :) I can't point out any case that won't work so if 
y'all think this is fine, let's leave it.