HDFS-4781. Fix a NullPointerException when listing .snapshot under a non-existing directory.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-2802@1478135 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt

@@ -329,3 +329,6 @@ Branch-2802 Snapshot (Unreleased)
 
   HDFS-4758. Disallow nested snapshottable directories and unwrap
   RemoteException.  (szetszwo)
+
+  HDFS-4781. Fix a NullPointerException when listing .snapshot under
+  a non-existing directory.  (szetszwo)

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

@@ -1588,7 +1588,8 @@ public class FSDirectory implements Closeable {
         src.length() - HdfsConstants.DOT_SNAPSHOT_DIR.length()));
     
     final INode node = this.getINode(dirPath);
-    if (node.isDirectory()
+    if (node != null
+        && node.isDirectory()
         && node.asDirectory() instanceof INodeDirectorySnapshottable) {
       return new HdfsFileStatus(0, true, 0, 0, 0, 0, null, null, null, null,
           HdfsFileStatus.EMPTY_NAME, -1L);

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

@@ -313,12 +313,12 @@ public abstract class INode implements Diff.Element<byte[]> {
    * children.
    * 
    * 1.3 The current inode is a {@link FileWithSnapshot}.
-   * Call {@link INode#recordModification(Snapshot)} to capture the 
-   * current states. Mark the INode as deleted.
+   * Call recordModification(..) to capture the current states.
+   * Mark the INode as deleted.
    * 
    * 1.4 The current inode is a {@link INodeDirectoryWithSnapshot}.
-   * Call {@link INode#recordModification(Snapshot)} to capture the 
-   * current states. Destroy files/directories created after the latest snapshot 
+   * Call recordModification(..) to capture the current states. 
+   * Destroy files/directories created after the latest snapshot 
    * (i.e., the inodes stored in the created list of the latest snapshot).
    * Recursively clean remaining children. 
    *

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

@@ -111,7 +111,7 @@ public class INodeDirectory extends INodeWithAdditionalFields {
    * Remove the specified child from this directory.
    * 
    * @param child the child inode to be removed
-   * @param latest See {@link INode#recordModification(Snapshot)}.
+   * @param latest See {@link INode#recordModification(Snapshot, INodeMap)}.
    */
   public boolean removeChild(INode child, Snapshot latest,
       final INodeMap inodeMap) throws QuotaExceededException {

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestSnapshotPathINodes.java

@@ -22,6 +22,8 @@ import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
+import java.io.FileNotFoundException;
+
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.DFSTestUtil;
@@ -238,6 +240,18 @@ public class TestSnapshotPathINodes {
     final INode last = nodesInPath.getLastINode();
     assertEquals(last.getFullPathName(), sub1.toString());
     assertFalse(last instanceof INodeFileWithSnapshot);
+    
+    String[] invalidPathComponent = {"invalidDir", "foo", ".snapshot", "bar"};
+    Path invalidPath = new Path(invalidPathComponent[0]);
+    for(int i = 1; i < invalidPathComponent.length; i++) {
+      invalidPath = new Path(invalidPath, invalidPathComponent[i]);
+      try {
+        hdfs.getFileStatus(invalidPath);
+        Assert.fail();
+      } catch(FileNotFoundException fnfe) {
+        System.out.println("The exception is expected: " + fnfe);
+      }
+    }
   }
   
   /**