mm: make some struct page's const

These uses are read-only and in a subsequent patch I have a const struct
page in my hand...

[akpm@linux-foundation.org: fix warnings in lowmem_page_address()]
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Michel Lespinasse <walken@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8a45ad22a170..6321e840e21d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -637,7 +637,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
 #define SECTIONS_MASK           ((1UL << SECTIONS_WIDTH) - 1)
 #define ZONEID_MASK             ((1UL << ZONEID_SHIFT) - 1)
 
-static inline enum zone_type page_zonenum(struct page *page)
+static inline enum zone_type page_zonenum(const struct page *page)
 {
         return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
 }
@@ -665,15 +665,15 @@ static inline int zone_to_nid(struct zone *zone)
 }
 
 #ifdef NODE_NOT_IN_PAGE_FLAGS
-extern int page_to_nid(struct page *page);
+extern int page_to_nid(const struct page *page);
 #else
-static inline int page_to_nid(struct page *page)
+static inline int page_to_nid(const struct page *page)
 {
         return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
 }
 #endif
 
-static inline struct zone *page_zone(struct page *page)
+static inline struct zone *page_zone(const struct page *page)
 {
         return &NODE_DATA(page_to_nid(page))->node_zones[page_zonenum(page)];
 }
@@ -718,9 +718,9 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
  */
 #include <linux/vmstat.h>
 
-static __always_inline void *lowmem_page_address(struct page *page)
+static __always_inline void *lowmem_page_address(const struct page *page)
 {
-        return __va(PFN_PHYS(page_to_pfn(page)));
+        return __va(PFN_PHYS(page_to_pfn((struct page *)page)));
 }
 
 #if defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL)