linux-kernel - [PATCH] generic: make lowmem_page_address() use PFN

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Date:	Thu, 20 May 2010 12:12:14 -0700
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
CC:	Barry Song <21cnbao@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH] generic: make lowmem_page_address() use PFN_PHYS() for improved
 portability

This ensures that platforms with lowmem PAs above 32 bits work
correctly by avoiding truncating the PA during a left shift.

Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
---
 include/linux/mm.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index fb19bb9..33bedcf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -13,6 +13,7 @@
 #include <linux/debug_locks.h>
 #include <linux/mm_types.h>
 #include <linux/range.h>
+#include <linux/pfn.h>

 struct mempolicy;
 struct anon_vma;
@@ -591,7 +592,7 @@ static inline void set_page_links(struct page *page,
enum zone_type zone,

 static __always_inline void *lowmem_page_address(struct page *page)
 {
-       return __va(page_to_pfn(page) << PAGE_SHIFT);
+       return __va(PFN_PHYS(page_to_pfn(page)));
 }

 #if defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL)


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