mm: memcontrol: simplify soft limit tree init code

- No need to test the node for N_MEMORY.  node_online() is enough for
  node fallback to work in slab, use NUMA_NO_NODE for everything else.

- Remove the BUG_ON() for allocation failure.  A NULL pointer crash is
  just as descriptive, and the absent return value check is obvious.

- Move local variables to the inner-most blocks.

- Point to the tree structure after its initialized, not before, it's
  just more logical that way.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Christoph Lameter <cl@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/memcontrol.c

@@ -4509,24 +4509,23 @@ EXPORT_SYMBOL(parent_mem_cgroup);
 
 static void __init mem_cgroup_soft_limit_tree_init(void)
 {
-	struct mem_cgroup_tree_per_node *rtpn;
-	struct mem_cgroup_tree_per_zone *rtpz;
-	int tmp, node, zone;
+	int node;
 
 	for_each_node(node) {
-		tmp = node;
-		if (!node_state(node, N_NORMAL_MEMORY))
-			tmp = -1;
-		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
-		BUG_ON(!rtpn);
+		struct mem_cgroup_tree_per_node *rtpn;
+		int zone;
 
-		soft_limit_tree.rb_tree_per_node[node] = rtpn;
+		rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
+				    node_online(node) ? node : NUMA_NO_NODE);
 
 		for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+			struct mem_cgroup_tree_per_zone *rtpz;
+
 			rtpz = &rtpn->rb_tree_per_zone[zone];
 			rtpz->rb_root = RB_ROOT;
 			spin_lock_init(&rtpz->lock);
 		}
+		soft_limit_tree.rb_tree_per_node[node] = rtpn;
 	}
 }