HDFS-13115. In getNumUnderConstructionBlocks(), ignore the inodeIds for which the inodes have been deleted. Contributed by Yongjun Zhang.

(cherry picked from commit f491f717e9ee6b75ad5cfca48da9c6297e94a8f7)

Conflicts:

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

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

@@ -142,7 +142,15 @@ public class LeaseManager {
       + "acquired before counting under construction blocks";
     long numUCBlocks = 0;
     for (Long id : getINodeIdWithLeases()) {
-      final INodeFile cons = fsnamesystem.getFSDirectory().getInode(id).asFile();
+      INode inode = fsnamesystem.getFSDirectory().getInode(id);
+      if (inode == null) {
+        // The inode could have been deleted after getINodeIdWithLeases() is
+        // called, check here, and ignore it if so
+        LOG.warn("Failed to find inode " + id +
+            " in getNumUnderConstructionBlocks().");
+        continue;
+      }
+      final INodeFile cons = inode.asFile();
       if (!cons.isUnderConstruction()) {
         LOG.warn("The file " + cons.getFullPathName()
             + " is not under construction but has lease.");
@@ -153,10 +161,11 @@ public class LeaseManager {
         continue;
       }
       for(BlockInfo b : blocks) {
-        if(!b.isComplete())
+        if(!b.isComplete()) {
           numUCBlocks++;
         }
       }
+    }
     LOG.info("Number of blocks under construction: " + numUCBlocks);
     return numUCBlocks;
   }