[PATCH] mm: define PFN_PAGE_MAP_LINEAR to optimize gigantic page scans

[Mike Kravetz]

Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
 arch/ia64/include/asm/page.h       | 1 +
 arch/m68k/include/asm/page_no.h    | 1 +
 include/asm-generic/memory_model.h | 2 ++
 mm/internal.h                      | 2 ++
 4 files changed, 6 insertions(+)

diff --git a/arch/ia64/include/asm/page.h b/arch/ia64/include/asm/page.h
index b69a5499d75b..8f4288862ec8 100644
--- a/arch/ia64/include/asm/page.h
+++ b/arch/ia64/include/asm/page.h
@@ -106,6 +106,7 @@ extern struct page *vmem_map;
 #ifdef CONFIG_DISCONTIGMEM
 # define page_to_pfn(page)	((unsigned long) (page - vmem_map))
 # define pfn_to_page(pfn)	(vmem_map + (pfn))
+# define PFN_PAGE_MAP_LINEAR
 # define __pfn_to_phys(pfn)	PFN_PHYS(pfn)
 #else
 # include <asm-generic/memory_model.h>
diff --git a/arch/m68k/include/asm/page_no.h b/arch/m68k/include/asm/page_no.h
index 6bbe52025de3..cafc0731a42c 100644
--- a/arch/m68k/include/asm/page_no.h
+++ b/arch/m68k/include/asm/page_no.h
@@ -28,6 +28,7 @@ extern unsigned long memory_end;
 
 #define pfn_to_page(pfn)	virt_to_page(pfn_to_virt(pfn))
 #define page_to_pfn(page)	virt_to_pfn(page_to_virt(page))
+#define PFN_PAGE_MAP_LINEAR
 #define pfn_valid(pfn)	        ((pfn) < max_mapnr)
 
 #define	virt_addr_valid(kaddr)	(((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index 7637fb46ba4f..8ac4c48dbf22 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -33,6 +33,7 @@
 #define __pfn_to_page(pfn)	(mem_map + ((pfn) - ARCH_PFN_OFFSET))
 #define __page_to_pfn(page)	((unsigned long)((page) - mem_map) + \
 				 ARCH_PFN_OFFSET)
+#define PFN_PAGE_MAP_LINEAR
 #elif defined(CONFIG_DISCONTIGMEM)
 
 #define __pfn_to_page(pfn)			\
@@ -53,6 +54,7 @@
 /* memmap is virtually contiguous.  */
 #define __pfn_to_page(pfn)	(vmemmap + (pfn))
 #define __page_to_pfn(page)	(unsigned long)((page) - vmemmap)
+#define PFN_PAGE_MAP_LINEAR
 
 #elif defined(CONFIG_SPARSEMEM)
 /*
diff --git a/mm/internal.h b/mm/internal.h
index 25d2b2439f19..64cc5069047c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -454,12 +454,14 @@ static inline struct page *mem_map_offset(struct page *base, int offset)
 static inline struct page *mem_map_next(struct page *iter,
 						struct page *base, int offset)
 {
+#ifndef PFN_PAGE_MAP_LINEAR
 	if (unlikely((offset & (MAX_ORDER_NR_PAGES - 1)) == 0)) {
 		unsigned long pfn = page_to_pfn(base) + offset;
 		if (!pfn_valid(pfn))
 			return NULL;
 		return pfn_to_page(pfn);
 	}
+#endif
 	return iter + 1;
 }
 
-- 
2.29.2