svn merge -c 1552711 merging from trunk to branch-2 to fix HDFS-5681. renewLease should not hold fsn write lock.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1552713 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -194,6 +194,8 @@ Release 2.4.0 - UNRELEASED
     HDFS-5341. Reduce fsdataset lock duration during directory scanning.
     (Qus-Jiawei via kihwal)
 
+    HDFS-5681. renewLease should not hold fsn write lock. (daryn via Kihwal)
+
   BUG FIXES
 
     HDFS-5034.  Remove debug prints from GetFileLinkInfo (Andrew Wang via Colin

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

@@ -3976,13 +3976,13 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
    */
   void renewLease(String holder) throws IOException {
     checkOperation(OperationCategory.WRITE);
-    writeLock();
+    readLock();
     try {
       checkOperation(OperationCategory.WRITE);
       checkNameNodeSafeMode("Cannot renew lease for " + holder);
       leaseManager.renewLease(holder);
     } finally {
-      writeUnlock();
+      readUnlock();
     }
   }