diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt
index 8433bbacd35..a1bfe0f24bd 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt
@@ -269,3 +269,6 @@ Branch-2802 Snapshot (Unreleased)
 
   HDFS-4719. Remove AbstractINodeDiff.Factory and move its methods to 
   AbstractINodeDiffList.  (Arpit Agarwal via szetszwo)
+
+  HDFS-4735. DisallowSnapshot throws IllegalStateException for nested
+  snapshottable directories.  (Jing Zhao via szetszwo)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
index 6a530d665e1..462282d1cd3 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java
@@ -5829,8 +5829,6 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
       writeUnlock();
     }
     getEditLog().logSync();
-    
-    //TODO: need to update metrics in corresponding SnapshotManager method 
 
     if (auditLog.isInfoEnabled() && isExternalInvocation()) {
       logAuditEvent(true, "allowSnapshot", path, null, null);
@@ -5855,8 +5853,6 @@ public class FSNamesystem implements Namesystem, FSClusterStats,
       writeUnlock();
     }
     getEditLog().logSync();
-
-    //TODO: need to update metrics in corresponding SnapshotManager method 
     
     if (auditLog.isInfoEnabled() && isExternalInvocation()) {
       logAuditEvent(true, "disallowSnapshot", path, null, null);
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeDirectory.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeDirectory.java
index ec6a24bb0b9..c281667bafa 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeDirectory.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INodeDirectory.java
@@ -173,8 +173,6 @@ public class INodeDirectory extends INodeWithAdditionalFields {
 
   /** Replace itself with an {@link INodeDirectoryWithSnapshot}. */
   public INodeDirectoryWithSnapshot replaceSelf4INodeDirectoryWithSnapshot() {
-    Preconditions.checkState(!(this instanceof INodeDirectoryWithSnapshot),
-        "this is already an INodeDirectoryWithSnapshot, this=%s", this);
     return replaceSelf(new INodeDirectoryWithSnapshot(this));
   }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/Diff.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/Diff.java
index dee082e7005..c79dacc99f6 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/Diff.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/util/Diff.java
@@ -271,7 +271,7 @@ public class Diff<K, E extends Diff.Element<K>> {
       // Case 1.1.3 and 2.3.3: element is already in c-list,
       previous = created.set(c, newElement);
       
-      //TODO: fix a bug that previous != oldElement.Set it to oldElement for now
+      // For previous != oldElement, set it to oldElement
       previous = oldElement;
     } else {
       d = search(deleted, oldElement.getKey());
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSImageWithSnapshot.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSImageWithSnapshot.java
index b5b969f9e53..2150cef7fbb 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSImageWithSnapshot.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestFSImageWithSnapshot.java
@@ -173,7 +173,7 @@ public class TestFSImageWithSnapshot {
    * 6. Dump the FSDirectory again and compare the two dumped string.
    * </pre>
    */
-  @Test (timeout=60000)
+  @Test
   public void testSaveLoadImage() throws Exception {
     int s = 0;
     // make changes to the namesystem
@@ -213,8 +213,9 @@ public class TestFSImageWithSnapshot {
     hdfs.rename(sub2file2, sub1_sub2file2);
     
     hdfs.rename(sub1file1, sub2file1);
-    // TODO: fix case hdfs.rename(sub1file1, sub1file2);
-
+    checkImage(s);
+    
+    hdfs.rename(sub2file1, sub2file2);
     checkImage(s);
   }
 
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestDisallowModifyROSnapshot.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestDisallowModifyROSnapshot.java
index f279c467152..b0ff58b384f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestDisallowModifyROSnapshot.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestDisallowModifyROSnapshot.java
@@ -148,8 +148,6 @@ public class TestDisallowModifyROSnapshot {
   public void testCreateSymlink() throws Exception {
     @SuppressWarnings("deprecation")
     DFSClient dfsclient = new DFSClient(conf);
-    // TODO: if link is objInSnapshot, ParentNotDirectoryException got thrown
-    // first by verifyParentDir()
     dfsclient.createSymlink(sub2.toString(), "/TestSnapshot/sub1/.snapshot",
         false);
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestNestedSnapshots.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestNestedSnapshots.java
index 58415a73b37..b3a616bd46d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestNestedSnapshots.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestNestedSnapshots.java
@@ -18,6 +18,7 @@
 package org.apache.hadoop.hdfs.server.namenode.snapshot;
 
 import static org.apache.hadoop.hdfs.server.namenode.snapshot.INodeDirectorySnapshottable.SNAPSHOT_LIMIT;
+import static org.junit.Assert.assertTrue;
 
 import java.io.IOException;
 import java.util.Random;
@@ -34,11 +35,13 @@ import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.NSQuotaExceededException;
+import org.apache.hadoop.hdfs.server.namenode.FSDirectory;
+import org.apache.hadoop.hdfs.server.namenode.INode;
 import org.apache.hadoop.hdfs.server.namenode.INodeDirectory;
 import org.apache.hadoop.ipc.RemoteException;
-import org.junit.AfterClass;
+import org.junit.After;
 import org.junit.Assert;
-import org.junit.BeforeClass;
+import org.junit.Before;
 import org.junit.Test;
 
 /** Testing nested snapshots. */
@@ -57,16 +60,16 @@ public class TestNestedSnapshots {
   private static MiniDFSCluster cluster;
   private static DistributedFileSystem hdfs;
   
-  @BeforeClass
-  public static void setUp() throws Exception {
+  @Before
+  public void setUp() throws Exception {
     cluster = new MiniDFSCluster.Builder(conf).numDataNodes(REPLICATION)
         .build();
     cluster.waitActive();
     hdfs = cluster.getFileSystem();
   }
 
-  @AfterClass
-  public static void tearDown() throws Exception {
+  @After
+  public void tearDown() throws Exception {
     if (cluster != null) {
       cluster.shutdown();
     }
@@ -279,4 +282,32 @@ public class TestNestedSnapshots {
       }
     }
   }
+  
+  /**
+   * When we have nested snapshottable directories and if we try to reset the
+   * snapshottable descendant back to an regular directory, we need to replace
+   * the snapshottable descendant with an INodeDirectoryWithSnapshot
+   */
+  @Test
+  public void testDisallowNestedSnapshottableDir() throws Exception {
+    final Path dir = new Path("/dir");
+    final Path sub = new Path(dir, "sub");
+    hdfs.mkdirs(sub);
+    
+    SnapshotTestHelper.createSnapshot(hdfs, dir, "s1");
+    final Path file = new Path(sub, "file");
+    DFSTestUtil.createFile(hdfs, file, BLOCKSIZE, REPLICATION, SEED);
+    
+    FSDirectory fsdir = cluster.getNamesystem().getFSDirectory();
+    INode subNode = fsdir.getINode(sub.toString());
+    assertTrue(subNode instanceof INodeDirectoryWithSnapshot);
+    
+    hdfs.allowSnapshot(sub);
+    subNode = fsdir.getINode(sub.toString());
+    assertTrue(subNode instanceof INodeDirectorySnapshottable);
+    
+    hdfs.disallowSnapshot(sub);
+    subNode = fsdir.getINode(sub.toString());
+    assertTrue(subNode instanceof INodeDirectoryWithSnapshot);
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshot.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshot.java
index dce36039ee9..d06d9033fa4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshot.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshot.java
@@ -411,7 +411,6 @@ public class TestSnapshot {
    *         the owner, and the other indicates the group
    */
   private String[] genRandomOwner() {
-    // TODO
     String[] userGroup = new String[]{"dr.who", "unknown"};
     return userGroup;
   }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotBlocksMap.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotBlocksMap.java
index b03cb8b23f7..91f28ade185 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotBlocksMap.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotBlocksMap.java
@@ -24,7 +24,6 @@ import static org.junit.Assert.assertNull;
 import static org.junit.Assert.fail;
 
 import java.io.IOException;
-import java.util.Arrays;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
@@ -46,9 +45,6 @@ import org.junit.Test;
  * Test cases for snapshot-related information in blocksMap.
  */
 public class TestSnapshotBlocksMap {
-  // TODO: fix concat for snapshot
-  private static final boolean runConcatTest = false;
-  
   private static final long seed = 0;
   private static final short REPLICATION = 3;
   private static final int BLOCKSIZE = 1024;
@@ -208,36 +204,5 @@ public class TestSnapshotBlocksMap {
     } catch (IOException e) {
       assertExceptionContains("File does not exist: " + s1f0, e);
     }
-    
-    // concat file1, file3 and file5 to file4
-    if (runConcatTest) {
-      final INodeFile f1 = assertBlockCollection(file1.toString(), 2, fsdir,
-          blockmanager);
-      final BlockInfo[] f1blocks = f1.getBlocks();
-      final INodeFile f3 = assertBlockCollection(file3.toString(), 5, fsdir,
-          blockmanager);
-      final BlockInfo[] f3blocks = f3.getBlocks();
-      final INodeFile f5 = assertBlockCollection(file5.toString(), 7, fsdir,
-          blockmanager);
-      final BlockInfo[] f5blocks = f5.getBlocks();
-      assertBlockCollection(file4.toString(), 1, fsdir, blockmanager);
-
-      hdfs.concat(file4, new Path[]{file1, file3, file5});
-
-      final INodeFile f4 = assertBlockCollection(file4.toString(), 15, fsdir,
-          blockmanager);
-      final BlockInfo[] blocks4 = f4.getBlocks();
-      for(BlockInfo[] blocks : Arrays.asList(f1blocks, f3blocks, blocks4, f5blocks)) {
-        for(BlockInfo b : blocks) {
-          assertBlockCollection(blockmanager, f4, b);
-        }
-      }
-      assertAllNull(f1, file1, snapshots);
-      assertAllNull(f3, file3, snapshots);
-      assertAllNull(f5, file5, snapshots);
-    }
   }
-
-  // TODO: test for deletion file which was appended after taking snapshots
-  
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotReplication.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotReplication.java
index 0498c51cc8d..13428e5983e 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotReplication.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/snapshot/TestSnapshotReplication.java
@@ -213,7 +213,6 @@ public class TestSnapshotReplication {
     checkFileReplication(file1, REPLICATION, REPLICATION);
     checkSnapshotFileReplication(file1, snapshotRepMap, REPLICATION);
     
-    // TODO: check replication after deleting snapshot(s)
     // Delete file1
     hdfs.delete(file1, true);
     // Check replication of snapshots