HDFS-9332. Fix Precondition failures from NameNodeEditLogRoller while saving namespace.

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

@@ -2196,6 +2196,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-9044. Give Priority to FavouredNodes , before selecting
     nodes from FavouredNode's Node Group (J.Andreina via vinayakumarb)
 
+    HDFS-9332. Fix Precondition failures from NameNodeEditLogRoller while
+    saving namespace. (wang)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

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

@@ -3729,9 +3729,7 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     public void run() {
       while (fsRunning && shouldRun) {
         try {
-          FSEditLog editLog = getFSImage().getEditLog();
-          long numEdits =
-              editLog.getLastWrittenTxId() - editLog.getCurSegmentTxId();
+          long numEdits = getTransactionsSinceLastLogRoll();
           if (numEdits > rollThreshold) {
             FSNamesystem.LOG.info("NameNode rolling its own edit log because"
                 + " number of edits in open segment exceeds threshold of "