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

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: <20251107174129.62a3f39c@kernel.org>
Date: Fri, 7 Nov 2025 17:41:29 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Byungchul Park <byungchul@...com>
Cc: linux-mm@...ck.org, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, kernel_team@...ynix.com,
 harry.yoo@...cle.com, ast@...nel.org, daniel@...earbox.net,
 davem@...emloft.net, 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, ziy@...dia.com,
 ilias.apalodimas@...aro.org, willy@...radead.org, brauner@...nel.org,
 kas@...nel.org, yuzhao@...gle.com, usamaarif642@...il.com,
 baolin.wang@...ux.alibaba.com, almasrymina@...gle.com, toke@...hat.com,
 asml.silence@...il.com, bpf@...r.kernel.org, linux-rdma@...r.kernel.org,
 sfr@...b.auug.org.au, dw@...idwei.uk, ap420073@...il.com,
 dtatulea@...dia.com
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

On Fri, 7 Nov 2025 13:47:08 +0900 Byungchul Park wrote:
> The offset of page_type in struct page cannot be used in struct net_iov
> for the same purpose, since the offset in struct net_iov is for storing
> (struct net_iov_area *)owner.

owner does not have to be at a fixed offset. Can we not move owner 
to _pp_mapping_pad ? Or reorder it with type, enum net_iov_type 
only has 2 values we can smoosh it with page_type easily.

> Yeah, you can tell 'why don't we add the field, page_type, to struct
> net_iov (or struct netmem_desc)' so as to be like:
> 
>   struct net_iov {
> 	union {
> 		struct netmem_desc desc;
> 		struct
> 		{
> 			unsigned long _flags;
> 			unsigned long pp_magic;
> 			struct page_pool *pp;
> 			unsigned long _pp_mapping_pad;
> 			unsigned long dma_addr;
> 			atomic_long_t pp_ref_count;
> +			unsigned int page_type; // add this field newly
> 		};
> 	};
> 	struct net_iov_area *owner; // the same offet of page_type
> 	enum net_iov_type type;
>   };
> 
> I think we can make it anyway but it makes less sense to add page_type
> to struct net_iov, only for PGTY_netpp.
> 
> It'd be better to use netmem_desc->pp for that purpose, IMO.