linux-kernel - [PATCH v2] mm:page.h: Calculate virt_to_page and page_to

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Date:	Tue, 23 Aug 2011 16:29:50 +0800
From:	Sonic Zhang <sonic.adi@...il.com>
To:	<linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>
CC:	<uclinux-dist-devel@...ckfin.uclinux.org>,
	Sonic Zhang <sonic.zhang@...log.com>
Subject: [PATCH v2] mm:page.h: Calculate virt_to_page and page_to_virt via predefined macro.

From: Sonic Zhang <sonic.zhang@...log.com>

In NOMMU architecture, if physical memory doesn't start from 0, ARCH_PFN_OFFSET is defined
to generate page index in mem_map array. Because virtual address is equal to physical
address, PAGE_OFFSET is always 0. virt_to_page and page_to_virt should not index page by
PAGE_OFFSET directly.

Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
---
 include/asm-generic/page.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h
index 75fec18..351889d 100644
--- a/include/asm-generic/page.h
+++ b/include/asm-generic/page.h
@@ -79,8 +79,8 @@ extern unsigned long memory_end;
 #define virt_to_pfn(kaddr)	(__pa(kaddr) >> PAGE_SHIFT)
 #define pfn_to_virt(pfn)	__va((pfn) << PAGE_SHIFT)
 
-#define virt_to_page(addr)	(mem_map + (((unsigned long)(addr)-PAGE_OFFSET) >> PAGE_SHIFT))
-#define page_to_virt(page)	((((page) - mem_map) << PAGE_SHIFT) + PAGE_OFFSET)
+#define virt_to_page(addr)	pfn_to_page(virt_to_pfn(addr))
+#define page_to_virt(page)	pfn_to_virt(page_to_pfn(page))
 
 #ifndef page_to_phys
 #define page_to_phys(page)      ((dma_addr_t)page_to_pfn(page) << PAGE_SHIFT)
-- 
1.7.0.4


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