netdev - Re: [RFC v3 18/18] page_pool: access ->pp_magic through struct netmem_desc in page_pool_page_is

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <eb82d1c8-fc85-4bcb-aba2-f73c31d69cd3@gmail.com>
Date: Thu, 29 May 2025 21:49:52 +0100
From: Pavel Begunkov <asml.silence@...il.com>
To: Mina Almasry <almasrymina@...gle.com>, 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, andrew+netdev@...n.ch, toke@...hat.com,
 tariqt@...dia.com, edumazet@...gle.com, pabeni@...hat.com,
 saeedm@...dia.com, leon@...nel.org, ast@...nel.org, daniel@...earbox.net,
 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, linux-rdma@...r.kernel.org, bpf@...r.kernel.org,
 vishal.moola@...il.com
Subject: Re: [RFC v3 18/18] page_pool: access ->pp_magic through struct
 netmem_desc in page_pool_page_is_pp()

On 5/29/25 20:54, Mina Almasry wrote:
...>>   #endif /* _LINUX_MM_H */
>> diff --git a/include/net/netmem.h b/include/net/netmem.h
>> index f05a8b008d00..9e4ed3530788 100644
>> --- a/include/net/netmem.h
>> +++ b/include/net/netmem.h
>> @@ -53,6 +53,20 @@ NETMEM_DESC_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
>>    */
>>   static_assert(sizeof(struct netmem_desc) <= offsetof(struct page, _refcount));
>>
>> +#ifdef CONFIG_PAGE_POOL
>> +static inline bool page_pool_page_is_pp(struct page *page)
>> +{
>> +       struct netmem_desc *desc = (__force struct netmem_desc *)page;
>> +
> 
> Is it expected that page can be cast to netmem_desc freely? I know it
> works now since netmem_desc and page have the same layout, but how is
> it going to continue to work when page is shrunk and no longer has
> 'pp_magic' inside of it? Is that series going to fixup all the places
> where casts are done?

It's expected the struct page will have a type field once it's shrunk.


> Is it also allowed that we can static cast netmem_desc to page?
> 
> Consider creating netmem_desc_page helper like ptdesc_page.
> 
> I'm not sure the __force is needed too.
> 

-- 
Pavel Begunkov