Re: [PATCH] mm: add a "struct page_frag" type containing a page, offset and length

[David Rientjes <rientjes@google.com>]

On Thu, 13 Oct 2011, Ian Campbell wrote:

> A few network drivers currently use skb_frag_struct for this purpose but I have
> patches which add additional fields and semantics there which these other uses
> do not want.
> 

Is this patch a part of a larger series that actually uses 
struct page_frag?  Probably a good idea to post them so we know it doesn't 
just lie there dormant.

> A structure for reference sub-page regions seems like a generally useful thing
> so do so instead of adding a network subsystem specific structure.
> 

Agreed.

> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Jens Axboe <jaxboe@fusionio.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> [since v1: s/struct subpage/struct page_frag/ on advice from Christoph]

Acked-by: David Rientjes <rientjes@google.com>

> ---
>  include/linux/mm_types.h |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 774b895..575faaf 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -135,6 +135,17 @@ struct page {
>  #endif
>  ;
>  
> +struct page_frag {
> +	struct page *page;
> +#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
> +	__u32 page_offset;
> +	__u32 size;
> +#else
> +	__u16 page_offset;
> +	__u16 size;
> +#endif
> +};
> +
>  typedef unsigned long __nocast vm_flags_t;
>  
>  /*

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