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

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Date: Tue, 9 Apr 2024 16:58:17 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Mina Almasry <almasrymina@...gle.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
CC: Ayush Sawal <ayush.sawal@...lsio.com>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, 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 4/8/2024 8:29 AM, Mina Almasry 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.
> 

The description sounds like a lot is going on here, and at first I was
thinking this should be split further. However I think that would just
end up with a lot of needless thrash.

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>