diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt
index 8728c3f7925..c27d9292129 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-2802.txt
@@ -244,3 +244,6 @@ Branch-2802 Snapshot (Unreleased)
 
   HDFS-4700. Fix the undo section of rename with snapshots.  (Jing Zhao via
   szetszwo)
+
+  HDFS-4529. Disallow concat when one of the src files is in some snapshot.
+  (szetszwo)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
index afd79f77098..478df02ade0 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
@@ -68,6 +68,7 @@ import org.apache.hadoop.hdfs.server.namenode.snapshot.INodeDirectoryWithSnapsho
 import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot.Root;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotAccessControlException;
+import org.apache.hadoop.hdfs.server.namenode.snapshot.SnapshotException;
 import org.apache.hadoop.hdfs.util.ByteArray;
 import org.apache.hadoop.hdfs.util.ReadOnlyList;
 
@@ -1099,9 +1100,9 @@ public class FSDirectory implements Closeable {
   /**
    * Concat all the blocks from srcs to trg and delete the srcs files
    */
-  public void concat(String target, String [] srcs) 
+  void concat(String target, String [] srcs) 
       throws UnresolvedLinkException, QuotaExceededException,
-      SnapshotAccessControlException {
+      SnapshotAccessControlException, SnapshotException {
     writeLock();
     try {
       // actual move
@@ -1122,7 +1123,7 @@ public class FSDirectory implements Closeable {
    */
   void unprotectedConcat(String target, String [] srcs, long timestamp) 
       throws UnresolvedLinkException, QuotaExceededException,
-      SnapshotAccessControlException {
+      SnapshotAccessControlException, SnapshotException {
     assert hasWriteLock();
     if (NameNode.stateChangeLog.isDebugEnabled()) {
       NameNode.stateChangeLog.debug("DIR* FSNamesystem.concat to "+target);
@@ -1137,7 +1138,24 @@ public class FSDirectory implements Closeable {
     
     final INodeFile [] allSrcInodes = new INodeFile[srcs.length];
     for(int i = 0; i < srcs.length; i++) {
-      allSrcInodes[i] = getINode4Write(srcs[i]).asFile();
+      final INodesInPath iip = getINodesInPath4Write(srcs[i]);
+      final Snapshot latest = iip.getLatestSnapshot();
+      final INode inode = iip.getLastINode();
+
+      // check if the file in the latest snapshot
+      if (inode.isInLatestSnapshot(latest)) {
+        throw new SnapshotException("Concat: the source file " + srcs[i]
+            + " is in snapshot " + latest);
+      }
+
+      // check if the file has other references.
+      if (inode.isReference() && ((INodeReference.WithCount)
+          inode.asReference().getReferredINode()).getReferenceCount() > 1) {
+        throw new SnapshotException("Concat: the source file " + srcs[i]
+            + " is referred by some other reference in some snapshot.");
+      }
+
+      allSrcInodes[i] = inode.asFile();
     }
     trgInode.concatBlocks(allSrcInodes);
     
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INode.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INode.java
index f32abd03e5f..14879341fd2 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INode.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/INode.java
@@ -42,6 +42,7 @@ import org.apache.hadoop.hdfs.util.Diff;
 import org.apache.hadoop.util.StringUtils;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
 import com.google.common.primitives.SignedBytes;
 
 /**
@@ -185,25 +186,27 @@ public abstract class INode implements Diff.Element<byte[]> {
   }
   
   /**
-   * Called by {@link INode#recordModification}. For a reference node and its
-   * subtree, the function tells which snapshot the modification should be
+   * When {@link #recordModification} is called on a referred node,
+   * this method tells which snapshot the modification should be
    * associated with: the snapshot that belongs to the SRC tree of the rename
    * operation, or the snapshot belonging to the DST tree.
    * 
-   * @param latest
+   * @param latestInDst
    *          the latest snapshot in the DST tree above the reference node
    * @return True: the modification should be recorded in the snapshot that
    *         belongs to the SRC tree. False: the modification should be
    *         recorded in the snapshot that belongs to the DST tree.
    */
-  public final boolean isInSrcSnapshot(final Snapshot latest) {
-    if (latest == null) {
+  public final boolean shouldRecordInSrcSnapshot(final Snapshot latestInDst) {
+    Preconditions.checkState(!isReference());
+
+    if (latestInDst == null) {
       return true;
     }
     INodeReference withCount = getParentReference();
     if (withCount != null) {
       int dstSnapshotId = withCount.getParentReference().getDstSnapshotId();
-      if (dstSnapshotId >= latest.getId()) {
+      if (dstSnapshotId >= latestInDst.getId()) {
         return true;
       }
     }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeDirectoryWithSnapshot.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeDirectoryWithSnapshot.java
index 8b8c524b214..80397ceef4f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeDirectoryWithSnapshot.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeDirectoryWithSnapshot.java
@@ -564,7 +564,7 @@ public class INodeDirectoryWithSnapshot extends INodeDirectoryWithQuota {
   @Override
   public INodeDirectoryWithSnapshot recordModification(final Snapshot latest)
       throws QuotaExceededException {
-    if (isInLatestSnapshot(latest) && !isInSrcSnapshot(latest)) {
+    if (isInLatestSnapshot(latest) && !shouldRecordInSrcSnapshot(latest)) {
       return saveSelf2Snapshot(latest, null);
     }
     return this;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileUnderConstructionWithSnapshot.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileUnderConstructionWithSnapshot.java
index 352ac188f27..5c8ffa3e501 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileUnderConstructionWithSnapshot.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileUnderConstructionWithSnapshot.java
@@ -95,7 +95,7 @@ public class INodeFileUnderConstructionWithSnapshot
   @Override
   public INodeFileUnderConstructionWithSnapshot recordModification(
       final Snapshot latest) throws QuotaExceededException {
-    if (isInLatestSnapshot(latest) && !isInSrcSnapshot(latest)) {
+    if (isInLatestSnapshot(latest) && !shouldRecordInSrcSnapshot(latest)) {
       diffs.saveSelf2Snapshot(latest, this, null);
     }
     return this;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileWithSnapshot.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileWithSnapshot.java
index 26d45e9914e..133f1c6c0dc 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileWithSnapshot.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/INodeFileWithSnapshot.java
@@ -66,7 +66,7 @@ public class INodeFileWithSnapshot extends INodeFile
   @Override
   public INodeFileWithSnapshot recordModification(final Snapshot latest)
       throws QuotaExceededException {
-    if (isInLatestSnapshot(latest) && !isInSrcSnapshot(latest)) {
+    if (isInLatestSnapshot(latest) && !shouldRecordInSrcSnapshot(latest)) {
       diffs.saveSelf2Snapshot(latest, this, null);
     }
     return this;
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotException.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotException.java
index 021f1f27721..565e08194cd 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotException.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/snapshot/SnapshotException.java
@@ -23,11 +23,11 @@ import java.io.IOException;
 public class SnapshotException extends IOException {
   private static final long serialVersionUID = 1L;
 
-  SnapshotException(final String message) {
+  public SnapshotException(final String message) {
     super(message);
   }
 
-  SnapshotException(final Throwable cause) {
+  public SnapshotException(final Throwable cause) {
     super(cause);
   }
 }
\ No newline at end of file