Add Parameter	rackMap : Map<String,List<DatanodeStorageInfo>> in method public chooseReplicaToDelete(moreThanOne Collection<DatanodeStorageInfo>, exactlyOne Collection<DatanodeStorageInfo>, excessTypes List<StorageType>, rackMap Map<String,List<DatanodeStorageInfo>>) : DatanodeStorageInfo from class org.apache.hadoop.hdfs.server.blockmanagement.BlockPlacementPolicyDefault