svn merge -c 1581936 from trunk for HDFS-6115. Call flush() for every append on block scan verification log.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.4@1581938 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -434,6 +434,9 @@ Release 2.4.0 - UNRELEASED
     HDFS-6130. NPE when upgrading namenode from fsimages older than -32.
     (wheat9)
 
+    HDFS-6115. Call flush() for every append on block scan verification log.
+    (Vinayakumar B via szetszwo)
+
   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/RollingLogsImpl.java

@@ -55,6 +55,7 @@ class RollingLogsImpl implements RollingLogs {
               + " is not yet opened.");
         }
         out.print(csq);
+        out.flush();
       }
       return this;
     }