HDFS-14610. HashMap is not thread safe. Field storageMap is typically synchronized by storageMap. However, in one place, field storageMap is not protected with synchronized. (#1015)

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

@@ -451,8 +451,11 @@ public class DatanodeDescriptor extends DatanodeInfo {
     this.volumeFailureSummary = volumeFailureSummary;
     for (StorageReport report : reports) {
 
-      DatanodeStorageInfo storage =
-          storageMap.get(report.getStorage().getStorageID());
+      DatanodeStorageInfo storage = null;
+      synchronized (storageMap) {
+        storage =
+            storageMap.get(report.getStorage().getStorageID());
+      }
       if (checkFailedStorages) {
         failedStorageInfos.remove(storage);
       }