mm/zonelist: enumerate zonelists array index

Hardcoding index to zonelists array in gfp_zonelist() is not a good
idea, let's enumerate it to improve readability.

No functional change.

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix CONFIG_NUMA=n build]
[n-horiguchi@ah.jp.nec.com: fix warning in comparing enumerator]
Signed-off-by: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2f6d30d..e40e702 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4148,8 +4148,7 @@
 
 static void build_zonelists(pg_data_t *pgdat)
 {
-	int j, node, load;
-	enum zone_type i;
+	int i, node, load;
 	nodemask_t used_mask;
 	int local_node, prev_node;
 	struct zonelist *zonelist;
@@ -4169,7 +4168,7 @@
 	nodes_clear(used_mask);
 
 	memset(node_order, 0, sizeof(node_order));
-	j = 0;
+	i = 0;
 
 	while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
 		/*
@@ -4186,12 +4185,12 @@
 		if (order == ZONELIST_ORDER_NODE)
 			build_zonelists_in_node_order(pgdat, node);
 		else
-			node_order[j++] = node;	/* remember order */
+			node_order[i++] = node;	/* remember order */
 	}
 
 	if (order == ZONELIST_ORDER_ZONE) {
 		/* calculate node order -- i.e., DMA last! */
-		build_zonelists_in_zone_order(pgdat, j);
+		build_zonelists_in_zone_order(pgdat, i);
 	}
 
 	build_thisnode_zonelists(pgdat);