mm: use zonelist name instead of using hardcoded index

Use the existing enums instead of hardcoded index when looking at the
zonelist.  This makes it more readable.  No functionality change by this
patch.

Link: http://lkml.kernel.org/r/1472227078-24852-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 2da72a5..ad1c96a 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1749,7 +1749,7 @@
 		 */
 		struct zonelist *zonelist;
 		enum zone_type highest_zoneidx = gfp_zone(GFP_KERNEL);
-		zonelist = &NODE_DATA(node)->node_zonelists[0];
+		zonelist = &NODE_DATA(node)->node_zonelists[ZONELIST_FALLBACK];
 		z = first_zones_zonelist(zonelist, highest_zoneidx,
 							&policy->v.nodes);
 		return z->zone ? z->zone->node : node;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b0f133f..f6a5a22 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4574,7 +4574,7 @@
 	int j;
 	struct zonelist *zonelist;
 
-	zonelist = &pgdat->node_zonelists[0];
+	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
 	for (j = 0; zonelist->_zonerefs[j].zone != NULL; j++)
 		;
 	j = build_zonelists_node(NODE_DATA(node), zonelist, j);
@@ -4590,7 +4590,7 @@
 	int j;
 	struct zonelist *zonelist;
 
-	zonelist = &pgdat->node_zonelists[1];
+	zonelist = &pgdat->node_zonelists[ZONELIST_NOFALLBACK];
 	j = build_zonelists_node(pgdat, zonelist, 0);
 	zonelist->_zonerefs[j].zone = NULL;
 	zonelist->_zonerefs[j].zone_idx = 0;
@@ -4611,7 +4611,7 @@
 	struct zone *z;
 	struct zonelist *zonelist;
 
-	zonelist = &pgdat->node_zonelists[0];
+	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
 	pos = 0;
 	for (zone_type = MAX_NR_ZONES - 1; zone_type >= 0; zone_type--) {
 		for (j = 0; j < nr_nodes; j++) {
@@ -4746,7 +4746,7 @@
 
 	local_node = pgdat->node_id;
 
-	zonelist = &pgdat->node_zonelists[0];
+	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
 	j = build_zonelists_node(pgdat, zonelist, 0);
 
 	/*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d3715c1..744f926 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3036,7 +3036,7 @@
 	 */
 	nid = mem_cgroup_select_victim_node(memcg);
 
-	zonelist = NODE_DATA(nid)->node_zonelists;
+	zonelist = &NODE_DATA(nid)->node_zonelists[ZONELIST_FALLBACK];
 
 	trace_mm_vmscan_memcg_reclaim_begin(0,
 					    sc.may_writepage,