mm, page_alloc: remove fair zone allocation policy

The fair zone allocation policy interleaves allocation requests between
zones to avoid an age inversion problem whereby new pages are reclaimed
to balance a zone.  Reclaim is now node-based so this should no longer
be an issue and the fair zone allocation policy is not free.  This patch
removes it.

Link: http://lkml.kernel.org/r/1467970510-21195-30-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/vmstat.c b/mm/vmstat.c
index bc94968..ab7f789 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -921,7 +921,6 @@
 const char * const vmstat_text[] = {
 	/* enum zone_stat_item countes */
 	"nr_free_pages",
-	"nr_alloc_batch",
 	"nr_zone_anon_lru",
 	"nr_zone_file_lru",
 	"nr_zone_write_pending",
@@ -1632,10 +1631,9 @@
 		val = atomic_long_read(&vm_zone_stat[i]);
 		if (val < 0) {
 			switch (i) {
-			case NR_ALLOC_BATCH:
 			case NR_PAGES_SCANNED:
 				/*
-				 * These are often seen to go negative in
+				 * This is often seen to go negative in
 				 * recent kernels, but not to go permanently
 				 * negative.  Whilst it would be nicer not to
 				 * have exceptions, rooting them out would be