HDFS-5061. Merge 1510626 from branch-2

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.1-beta@1510629 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -13,6 +13,9 @@ Release 2.1.1-beta - UNRELEASED
     HDFS-4513. Clarify in the WebHDFS REST API that all JSON respsonses may
     contain additional properties.  (szetszwo)
 
+    HDFS-5061. Make FSNameSystem#auditLoggers an unmodifiable list. 
+    (Arpit Agarwal via suresh)
+
   OPTIMIZATIONS
 
   BUG FIXES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -757,7 +757,7 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
     if (auditLoggers.isEmpty()) {
       auditLoggers.add(new DefaultAuditLogger());
     }
-    return auditLoggers;
+    return Collections.unmodifiableList(auditLoggers);
   }
 
   void loadFSImage(StartupOption startOpt, FSImage fsImage, boolean haEnabled)