[RFC:PATCH 003/008] Handle tail pages in kmap & kmap_atomic

[Dave Kleikamp <shaggy@austin.ibm.com>]

Handle tail pages in kmap & kmap_atomic

TODO: possibly move to mm.h: lowmem_page_address()

Signed-off-by: Dave Kleikamp <shaggy@austin.ibm.com>
---
diff -Nurp linux002/include/asm-powerpc/io.h linux003/include/asm-powerpc/io.h
--- linux002/include/asm-powerpc/io.h	2006-06-17 20:49:35.000000000 -0500
+++ linux003/include/asm-powerpc/io.h	2006-07-17 23:04:38.000000000 -0500
@@ -250,7 +250,9 @@ static inline void * phys_to_virt(unsign
 /*
  * Change "struct page" to physical address.
  */
-#define page_to_phys(page)	(page_to_pfn(page) << PAGE_SHIFT)
+#define page_to_phys(page)	(PageTail(page) ?			\
+				__pa((page)->mapping->tail) :		\
+				page_to_pfn(page) << PAGE_SHIFT)
 
 /* We do NOT want virtual merging, it would put too much pressure on
  * our iommu allocator. Instead, we want drivers to be smart enough
diff -Nurp linux002/include/linux/highmem.h linux003/include/linux/highmem.h
--- linux002/include/linux/highmem.h	2006-06-17 20:49:35.000000000 -0500
+++ linux003/include/linux/highmem.h	2006-07-17 23:04:38.000000000 -0500
@@ -33,12 +33,21 @@ static inline unsigned int nr_free_highp
 static inline void *kmap(struct page *page)
 {
 	might_sleep();
+#ifdef CONFIG_FILE_TAILS
+	return PageTail(page) ? page->mapping->tail : page_address(page);
+#else
 	return page_address(page);
+#endif
 }
 
 #define kunmap(page) do { (void) (page); } while (0)
 
+#ifdef CONFIG_FILE_TAILS
+#define kmap_atomic(page, idx) \
+       	(PageTail(page) ? (page)->mapping->tail : page_address(page))
+#else
 #define kmap_atomic(page, idx)		page_address(page)
+#endif
 #define kunmap_atomic(addr, idx)	do { } while (0)
 #define kmap_atomic_pfn(pfn, idx)	page_address(pfn_to_page(pfn))
 #define kmap_atomic_to_page(ptr)	virt_to_page(ptr)

-- 
David Kleikamp
IBM Linux Technology Center

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