linux-kernel - Re: [PATCH v2 02/16] netmem: introduce netmem alloc APIs to wrap page alloc APIs

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Message-ID: <CAHS8izOkr96_i1B8o_AWQGgfWSWZVVjHhOShReLZozsxZB6WdQ@mail.gmail.com>
Date: Tue, 27 May 2025 20:11:58 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Byungchul Park <byungchul@...com>
Cc: willy@...radead.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mm@...ck.org, kernel_team@...ynix.com, kuba@...nel.org, 
	ilias.apalodimas@...aro.org, harry.yoo@...cle.com, hawk@...nel.org, 
	akpm@...ux-foundation.org, davem@...emloft.net, john.fastabend@...il.com, 
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	linux-rdma@...r.kernel.org, bpf@...r.kernel.org, vishal.moola@...il.com
Subject: Re: [PATCH v2 02/16] netmem: introduce netmem alloc APIs to wrap page
 alloc APIs

On Tue, May 27, 2025 at 7:29 PM Byungchul Park <byungchul@...com> wrote:
>
> To eliminate the use of struct page in page pool, the page pool code
> should use netmem descriptor and APIs instead.
>
> As part of the work, introduce netmem alloc APIs allowing the code to
> use them rather than the existing APIs for struct page.
>
> Signed-off-by: Byungchul Park <byungchul@...com>
> ---
>  include/net/netmem.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/include/net/netmem.h b/include/net/netmem.h
> index a721f9e060a2..37d0e0e002c2 100644
> --- a/include/net/netmem.h
> +++ b/include/net/netmem.h
> @@ -177,6 +177,19 @@ static inline netmem_ref page_to_netmem(struct page *page)
>         return (__force netmem_ref)page;
>  }
>
> +static inline netmem_ref alloc_netmems_node(int nid, gfp_t gfp_mask,
> +               unsigned int order)
> +{
> +       return page_to_netmem(alloc_pages_node(nid, gfp_mask, order));
> +}
> +
> +static inline unsigned long alloc_netmems_bulk_node(gfp_t gfp, int nid,
> +               unsigned long nr_netmems, netmem_ref *netmem_array)
> +{
> +       return alloc_pages_bulk_node(gfp, nid, nr_netmems,
> +                       (struct page **)netmem_array);
> +}
> +
>  /**
>   * virt_to_netmem - convert virtual memory pointer to a netmem reference
>   * @data: host memory pointer to convert

Code looks fine to me, but I'm not sure we want to export these
helpers in include/net where they're available to the entire kernel
and net stack. Can we put these helpers in net/core/page_pool.c or at
least net/core/netmem_priv.h?

Also maybe the helpers aren't needed anyway. AFAICT there is only 1
call site in page_pool.c for each, so maybe we can implement this
inline.

-- 
Thanks,
Mina