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

[Ian Campbell <ian.campbell@citrix.com>]

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.

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

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]
---
 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;
 
 /*
-- 
1.7.2.5

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