linux-kernel - Re: [PATCH net-next v10 02/12] netmem: use netmem_desc instead of page to access ->pp in __netmem_get

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Message-ID: <6e4a4ae7-b84e-470d-81e9-a58ecf9c9157@gmail.com>
Date: Thu, 17 Jul 2025 10:17:17 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Mina Almasry <almasrymina@...gle.com>, Byungchul Park <byungchul@...com>,
 "Lobakin, Aleksander" <aleksander.lobakin@...el.com>
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Subject: Re: [PATCH net-next v10 02/12] netmem: use netmem_desc instead of
 page to access ->pp in __netmem_get_pp()

On 7/16/25 20:41, Mina Almasry wrote:
...>> I will kill __netmem_get_pp() as you and I prefer.  However,
>> __netmem_get_pp() users e.i. libeth_xdp_return_va() and
>> libeth_xdp_tx_fill_buf() should be altered.  I will modify the code like:
>>
>> as is: __netmem_get_pp(netmem)
>> to be: __netmem_nmdesc(netmem)->pp
>>
>> Is it okay with you?
>>
> 
> When Pavel and I were saying 'remove __netmem_get_pp', I think we
> meant to remove the entire concept of unsafe netmem -> page
> conversions. I think we both don't like them. From this perspective,
> __netmem_nmdesc(netmem)->pp is just as bad as __netmem_get_pp(netmem).

Yes. It'd great to have all of them gone. IMHO it's much better
to let the caller do the casting so at least it's explicit and
assumptions are not hidden. E.g. instead of

pp = __netmem_nmdesc(netmem)->pp;

It'd be

struct page *page = __netmem_to_page(netmem);

page_to_nmdesc(page)->pp;
// or page_get_pp(page), or whatever the helper is

That might be easier as well.

-- 
Pavel Begunkov