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/migrate.c b/mm/migrate.c
index f560071..de5c371 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1497,7 +1497,7 @@
 					  __GFP_NOWARN) &
 					 ~GFP_IOFS, 0);
 	if (newpage)
-		page_xchg_last_nid(newpage, page_last_nid(page));
+		page_nid_xchg_last(newpage, page_nid_last(page));
 
 	return newpage;
 }
@@ -1681,7 +1681,7 @@
 	if (!new_page)
 		goto out_fail;
 
-	page_xchg_last_nid(new_page, page_last_nid(page));
+	page_nid_xchg_last(new_page, page_nid_last(page));
 
 	isolated = numamigrate_isolate_page(pgdat, page);
 	if (!isolated) {