crush: fix tree node weight lookup

Fix the node weight lookup for tree buckets by using a correct accessor.

Reflects ceph.git commit d287ade5bcbdca82a3aef145b92924cf1e856733.

Reviewed-by: Alex Elder <elder@inktank.com>
Signed-off-by: Sage Weil <sage@inktank.com>

include/linux/crush/crush.h

@@ -166,4 +166,9 @@ extern void crush_destroy_bucket_straw(struct crush_bucket_straw *b);
 extern void crush_destroy_bucket(struct crush_bucket *b);
 extern void crush_destroy(struct crush_map *map);
 
+static inline int crush_calc_tree_node(int i)
+{
+	return ((i+1) << 1)-1;
+}
+
 #endif

net/ceph/crush/crush.c

@@ -37,9 +37,7 @@ int crush_get_bucket_item_weight(const struct crush_bucket *b, int p)
 	case CRUSH_BUCKET_LIST:
 		return ((struct crush_bucket_list *)b)->item_weights[p];
 	case CRUSH_BUCKET_TREE:
-		if (p & 1)
-			return ((struct crush_bucket_tree *)b)->node_weights[p];
-		return 0;
+		return ((struct crush_bucket_tree *)b)->node_weights[crush_calc_tree_node(p)];
 	case CRUSH_BUCKET_STRAW:
 		return ((struct crush_bucket_straw *)b)->item_weights[p];
 	}