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>

mm/mempolicy.c

@@ -1749,7 +1749,7 @@ unsigned int mempolicy_slab_node(void)
 		 */
 		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;

mm/page_alloc.c

@@ -4574,7 +4574,7 @@ static void build_zonelists_in_node_order(pg_data_t *pgdat, int node)
 	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 @@ static void build_thisnode_zonelists(pg_data_t *pgdat)
 	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 @@ static void build_zonelists_in_zone_order(pg_data_t *pgdat, int nr_nodes)
 	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 @@ static void build_zonelists(pg_data_t *pgdat)
 
 	local_node = pgdat->node_id;
 
-	zonelist = &pgdat->node_zonelists[0];
+	zonelist = &pgdat->node_zonelists[ZONELIST_FALLBACK];
 	j = build_zonelists_node(pgdat, zonelist, 0);
 
 	/*

mm/vmscan.c

@@ -3036,7 +3036,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 	 */
 	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,