linux-kernel - Re: [RFC mm v5 1/2] page_pool: check nmdesc->pp to see its usage as page pool for net

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Message-ID: <87ms53pam0.fsf@toke.dk>
Date: Mon, 03 Nov 2025 13:24:39 +0100
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: Byungchul Park <byungchul@...com>, linux-mm@...ck.org,
 netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, kernel_team@...ynix.com,
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Subject: Re: [RFC mm v5 1/2] page_pool: check nmdesc->pp to see its usage as
 page pool for net_iov not page-backed

Byungchul Park <byungchul@...com> writes:

> Currently, the condition 'page->pp_magic == PP_SIGNATURE' is used to
> determine if a page belongs to a page pool.  However, with the planned
> removal of ->pp_magic, we will instead leverage the page_type in struct
> page, such as PGTY_netpp, for this purpose.
>
> That works for page-backed network memory.  However, for net_iov not
> page-backed, the identification cannot be based on the page_type.
> Instead, nmdesc->pp can be used to see if it belongs to a page pool, by
> making sure nmdesc->pp is NULL otherwise.
>
> For net_iov not page-backed, initialize it using nmdesc->pp = NULL in
> net_devmem_bind_dmabuf() and using kvmalloc_array(__GFP_ZERO) in
> io_zcrx_create_area() so that netmem_is_pp() can check if nmdesc->pp is
> !NULL to confirm its usage as page pool.
>
> Signed-off-by: Byungchul Park <byungchul@...com>
> Reviewed-by: Mina Almasry <almasrymina@...gle.com>

Reviewed-by: Toke Høiland-Jørgensen <toke@...hat.com>