HDFS-15295. AvailableSpaceBlockPlacementPolicy should use chooseRandomWithStorageTypeTwoTrial() for better performance. Contributed by Jinglun.

(cherry picked from commit 453771f170a062265b7687b31b2a3735827958fb)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/AvailableSpaceBlockPlacementPolicy.java

@@ -87,9 +87,9 @@ public class AvailableSpaceBlockPlacementPolicy extends
     Preconditions.checkArgument(clusterMap instanceof DFSNetworkTopology);
     DFSNetworkTopology dfsClusterMap = (DFSNetworkTopology)clusterMap;
     DatanodeDescriptor a = (DatanodeDescriptor) dfsClusterMap
-        .chooseRandomWithStorageType(scope, excludedNode, type);
+        .chooseRandomWithStorageTypeTwoTrial(scope, excludedNode, type);
     DatanodeDescriptor b = (DatanodeDescriptor) dfsClusterMap
-        .chooseRandomWithStorageType(scope, excludedNode, type);
+        .chooseRandomWithStorageTypeTwoTrial(scope, excludedNode, type);
     return select(a, b, false);
   }