linux-kernel - Re: [PATCH 01/18] netmem: introduce struct netmem_desc struct_group_tagged()'ed on struct 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: <20250527025047.GA71538@system.software.com>
Date: Tue, 27 May 2025 11:50:47 +0900
From: Byungchul Park <byungchul@...com>
To: willy@...radead.org, netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kernel_team@...ynix.com, kuba@...nel.org, almasrymina@...gle.com,
	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,
	asml.silence@...il.com, 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: [PATCH 01/18] netmem: introduce struct netmem_desc
 struct_group_tagged()'ed on struct net_iov

On Fri, May 23, 2025 at 12:25:52PM +0900, Byungchul Park wrote:
> To simplify struct page, the page pool members of struct page should be
> moved to other, allowing these members to be removed from struct page.
> 
> Introduce a network memory descriptor to store the members, struct
> netmem_desc, reusing struct net_iov that already mirrored struct page.
> 
> While at it, relocate _pp_mapping_pad to group struct net_iov's fields.
> 
> Signed-off-by: Byungchul Park <byungchul@...com>
> ---
>  include/linux/mm_types.h |  2 +-
>  include/net/netmem.h     | 43 +++++++++++++++++++++++++++++++++-------
>  2 files changed, 37 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 56d07edd01f9..873e820e1521 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -120,13 +120,13 @@ struct page {
>  			unsigned long private;
>  		};
>  		struct {	/* page_pool used by netstack */
> +			unsigned long _pp_mapping_pad;
>  			/**
>  			 * @pp_magic: magic value to avoid recycling non
>  			 * page_pool allocated pages.
>  			 */
>  			unsigned long pp_magic;
>  			struct page_pool *pp;
> -			unsigned long _pp_mapping_pad;
>  			unsigned long dma_addr;
>  			atomic_long_t pp_ref_count;
>  		};
> diff --git a/include/net/netmem.h b/include/net/netmem.h
> index 386164fb9c18..08e9d76cdf14 100644
> --- a/include/net/netmem.h
> +++ b/include/net/netmem.h
> @@ -31,12 +31,41 @@ enum net_iov_type {
>  };
>  
>  struct net_iov {
> -	enum net_iov_type type;
> -	unsigned long pp_magic;
> -	struct page_pool *pp;
> -	struct net_iov_area *owner;
> -	unsigned long dma_addr;
> -	atomic_long_t pp_ref_count;
> +	/*
> +	 * XXX: Now that struct netmem_desc overlays on struct page,
> +	 * struct_group_tagged() should cover all of them.  However,
> +	 * a separate struct netmem_desc should be declared and embedded,
> +	 * once struct netmem_desc is no longer overlayed but it has its
> +	 * own instance from slab.  The final form should be:
> +	 *
> +	 *    struct netmem_desc {
> +	 *	   unsigned long pp_magic;
> +	 *	   struct page_pool *pp;
> +	 *	   unsigned long dma_addr;
> +	 *	   atomic_long_t pp_ref_count;
> +	 *    };
> +	 *
> +	 *    struct net_iov {
> +	 *	   enum net_iov_type type;
> +	 *	   struct net_iov_area *owner;
> +	 *	   struct netmem_desc;
> +	 *    };
> +	 */
> +	struct_group_tagged(netmem_desc, desc,

So..  For now, this is the best option we can pick.  We can do all that
you told me once struct netmem_desc has it own instance from slab.

Again, it's because the page pool fields (or netmem things) from struct
page will be gone by this series.

Mina, thoughts?

	Byungchul

> +		/*
> +		 * only for struct net_iov
> +		 */
> +		enum net_iov_type type;
> +		struct net_iov_area *owner;
> +
> +		/*
> +		 * actually for struct netmem_desc
> +		 */
> +		unsigned long pp_magic;
> +		struct page_pool *pp;
> +		unsigned long dma_addr;
> +		atomic_long_t pp_ref_count;
> +	);
>  };
>  
>  struct net_iov_area {
> @@ -51,9 +80,9 @@ struct net_iov_area {
>  /* These fields in struct page are used by the page_pool and net stack:
>   *
>   *        struct {
> + *                unsigned long _pp_mapping_pad;
>   *                unsigned long pp_magic;
>   *                struct page_pool *pp;
> - *                unsigned long _pp_mapping_pad;
>   *                unsigned long dma_addr;
>   *                atomic_long_t pp_ref_count;
>   *        };
> -- 
> 2.17.1