diff --git a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java
index f5875d8d96..6969d19043 100644
--- a/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java
+++ b/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/IOUtils.java
@@ -20,6 +20,9 @@
 
 import java.io.*;
 import java.net.Socket;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.WritableByteChannel;
 
 import org.apache.commons.logging.Log;
 
@@ -245,4 +248,34 @@ public void write(byte[] b, int off, int len) throws IOException {
     public void write(int b) throws IOException {
     }
   }  
+  
+  /**
+   * Write a ByteBuffer to a WritableByteChannel, handling short writes.
+   * 
+   * @param bc               The WritableByteChannel to write to
+   * @param buf              The input buffer
+   * @throws IOException     On I/O error
+   */
+  public static void writeFully(WritableByteChannel bc, ByteBuffer buf)
+      throws IOException {
+    do {
+      bc.write(buf);
+    } while (buf.remaining() > 0);
+  }
+
+  /**
+   * Write a ByteBuffer to a FileChannel at a given offset, 
+   * handling short writes.
+   * 
+   * @param fc               The FileChannel to write to
+   * @param buf              The input buffer
+   * @param offset           The offset in the file to start writing at
+   * @throws IOException     On I/O error
+   */
+  public static void writeFully(FileChannel fc, ByteBuffer buf,
+      long offset) throws IOException {
+    do {
+      offset += fc.write(buf, offset);
+    } while (buf.remaining() > 0);
+  }
 }
diff --git a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java
index d4f5057f7c..60c0703abc 100644
--- a/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java
+++ b/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/io/TestIOUtils.java
@@ -21,9 +21,13 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.io.RandomAccessFile;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
 
 import org.junit.Test;
 import org.mockito.Mockito;
@@ -32,7 +36,8 @@
  * Test cases for IOUtils.java
  */
 public class TestIOUtils {
-
+  private static final String TEST_FILE_NAME = "test_file";
+  
   @Test
   public void testCopyBytesShouldCloseStreamsWhenCloseIsTrue() throws Exception {
     InputStream inputStream = Mockito.mock(InputStream.class);
@@ -110,4 +115,41 @@ public void testCopyBytesWithCountShouldThrowOutTheStreamClosureExceptions()
     Mockito.verify(outputStream, Mockito.atLeastOnce()).close();
   }
   
+  @Test
+  public void testWriteFully() throws IOException {
+    final int INPUT_BUFFER_LEN = 10000;
+    final int HALFWAY = 1 + (INPUT_BUFFER_LEN / 2);
+    byte[] input = new byte[INPUT_BUFFER_LEN];
+    for (int i = 0; i < input.length; i++) {
+      input[i] = (byte)(i & 0xff);
+    }
+    byte[] output = new byte[input.length];
+    
+    try {
+      RandomAccessFile raf = new RandomAccessFile(TEST_FILE_NAME, "rw");
+      FileChannel fc = raf.getChannel();
+      ByteBuffer buf = ByteBuffer.wrap(input);
+      IOUtils.writeFully(fc, buf);
+      raf.seek(0);
+      raf.read(output);
+      for (int i = 0; i < input.length; i++) {
+        assertEquals(input[i], output[i]);
+      }
+      buf.rewind();
+      IOUtils.writeFully(fc, buf, HALFWAY);
+      for (int i = 0; i < HALFWAY; i++) {
+        assertEquals(input[i], output[i]);
+      }
+      raf.seek(0);
+      raf.read(output);
+      for (int i = HALFWAY; i < input.length; i++) {
+        assertEquals(input[i - HALFWAY], output[i]);
+      }
+    } finally {
+      File f = new File(TEST_FILE_NAME);
+      if (f.exists()) {
+        f.delete();
+      }
+    }
+  }
 }
diff --git a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
index fb5ae88cd9..155e45f83c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
+++ b/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
@@ -328,6 +328,9 @@ Branch-2 ( Unreleased changes )
     HDFS-3522. If a namenode is in safemode, it should throw SafeModeException
     when getBlockLocations has zero locations.  (Brandon Li via szetszwo)
 
+    HDFS-3531. EditLogFileOutputStream#preallocate should check for
+    incomplete writes. (Colin Patrick McCabe via eli)
+
   BREAKDOWN OF HDFS-3042 SUBTASKS
 
     HDFS-2185. HDFS portion of ZK-based FailoverController (todd)
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
index dd8102ee74..08a560ce12 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/EditLogFileOutputStream.java
@@ -206,10 +206,10 @@ private void preallocate() throws IOException {
             + fc.size());
       }
       fill.position(0);
-      int written = fc.write(fill, position);
+      IOUtils.writeFully(fc, fill, position);
       if(FSNamesystem.LOG.isDebugEnabled()) {
         FSNamesystem.LOG.debug("Edit log size is now " + fc.size() +
-            " written " + written + " bytes " + " at offset " + position);
+            " written " + fill.capacity() + " bytes " + " at offset " + position);
       }
     }
   }