netdev - Re: [PATCH] mm, page_pool: introduce a new page type for page pool in page type

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Message-ID: <77ee68c4-f265-4e55-9889-43ab08f26efd@gmail.com>
Date: Mon, 21 Jul 2025 12:12:39 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Byungchul Park <byungchul@...com>, linux-mm@...ck.org,
 netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel_team@...ynix.com,
 harry.yoo@...cle.com, ast@...nel.org, daniel@...earbox.net,
 davem@...emloft.net, kuba@...nel.org, hawk@...nel.org,
 john.fastabend@...il.com, sdf@...ichev.me, saeedm@...dia.com,
 leon@...nel.org, tariqt@...dia.com, mbloch@...dia.com,
 andrew+netdev@...n.ch, edumazet@...gle.com, pabeni@...hat.com,
 akpm@...ux-foundation.org, david@...hat.com, lorenzo.stoakes@...cle.com,
 Liam.Howlett@...cle.com, vbabka@...e.cz, rppt@...nel.org, surenb@...gle.com,
 mhocko@...e.com, horms@...nel.org, jackmanb@...gle.com, hannes@...xchg.org,
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 usamaarif642@...il.com, baolin.wang@...ux.alibaba.com,
 almasrymina@...gle.com, toke@...hat.com, bpf@...r.kernel.org,
 linux-rdma@...r.kernel.org
Subject: Re: [PATCH] mm, page_pool: introduce a new page type for page pool in
 page type

On 7/21/25 06:49, Byungchul Park wrote:
> Hi,
> 
> I focused on converting the existing APIs accessing ->pp_magic field to
> page type APIs.  However, yes.  Additional works would better be
> considered on top like:
> 
>     1. Adjust how to store and retrieve dma index.  Maybe network guys
>        can work better on top.
> 
>     2. Move the sanity check for page pool in mm/page_alloc.c to on free.

Don't be in a hurry, I've got a branch, but as mentioned before,
it'll be for-6.18. And there will also be more time for testing.

> This work was inspired by the following link by Pavel:

The idea came from David, let's add

Suggested-by: David Hildenbrand <david@...hat.com>

...> -
>   static inline bool netmem_is_pp(netmem_ref netmem)
>   {
> -	return (netmem_get_pp_magic(netmem) & PP_MAGIC_MASK) == PP_SIGNATURE;
> +	if (netmem_is_net_iov(netmem))

This needs to return false for tx niovs. Seems like all callers are
gated on ->pp_recycle, so maybe it's fine, but we can at least
check pp. Mina, you've been checking tx doesn't mix with rx, any
opinion on that?

Question to net maintainers, can a ->pp_recycle marked skb contain
not page pool originated pages or a mix?

-- 
Pavel Begunkov