mm: rename page struct field helpers

The function names page_xchg_last_nid(), page_last_nid() and
reset_page_last_nid() were judged to be inconsistent so rename them to a
struct_field_op style pattern.  As it looked jarring to have
reset_page_mapcount() and page_nid_reset_last() beside each other in
memmap_init_zone(), this patch also renames reset_page_mapcount() to
page_mapcount_reset().  There are others like init_page_count() but as
it is used throughout the arch code a rename would likely cause more
conflicts than it is worth.

[akpm@linux-foundation.org: fix zcache]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mmzone.c b/mm/mmzone.c
index bce796e..2ac0afb 100644
--- a/mm/mmzone.c
+++ b/mm/mmzone.c
@@ -98,14 +98,14 @@
 }
 
 #if defined(CONFIG_NUMA_BALANCING) && !defined(LAST_NID_NOT_IN_PAGE_FLAGS)
-int page_xchg_last_nid(struct page *page, int nid)
+int page_nid_xchg_last(struct page *page, int nid)
 {
 	unsigned long old_flags, flags;
 	int last_nid;
 
 	do {
 		old_flags = flags = page->flags;
-		last_nid = page_last_nid(page);
+		last_nid = page_nid_last(page);
 
 		flags &= ~(LAST_NID_MASK << LAST_NID_PGSHIFT);
 		flags |= (nid & LAST_NID_MASK) << LAST_NID_PGSHIFT;