HDFS-5705. Merging r1555190 and r1576989 from trunk to branch-2.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1576991 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -359,6 +359,9 @@ Release 2.4.0 - UNRELEASED
 
     HDFS-6079. Timeout for getFileBlockStorageLocations does not work. (wang)
 
+    HDFS-5705. TestSecondaryNameNodeUpgrade#testChangeNsIDFails may fail due
+    to ConcurrentModificationException. (Ted Yu via brandonli)
+
   BREAKDOWN OF HDFS-5698 SUBTASKS AND RELATED JIRAS
 
     HDFS-5717. Save FSImage header in protobuf. (Haohui Mai via jing9)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java

@@ -19,10 +19,10 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import java.io.File;
 import java.io.IOException;
-import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executor;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadFactory;
@@ -54,7 +54,7 @@ class FsVolumeImpl implements FsVolumeSpi {
   private final String storageID;
   private final StorageType storageType;
   private final Map<String, BlockPoolSlice> bpSlices
-      = new HashMap<String, BlockPoolSlice>();
+      = new ConcurrentHashMap<String, BlockPoolSlice>();
   private final File currentDir;    // <StorageDirectory>/current
   private final DF usage;           
   private final long reserved;