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From z..@apache.org
Subject [05/50] [abbrv] hadoop git commit: HDFS-7496. Fix FsVolume removal race conditions on the DataNode by reference-counting the volume instances (lei via cmccabe)
Date Mon, 26 Jan 2015 17:44:20 GMT
HDFS-7496. Fix FsVolume removal race conditions on the DataNode by reference-counting the volume instances (lei via cmccabe)


Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/9014305e
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/9014305e
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/9014305e

Branch: refs/heads/HDFS-EC
Commit: 9014305e0bb8cca43fd886562bf7fade545f58ac
Parents: a6d1f21
Author: Colin Patrick Mccabe <cmccabe@cloudera.com>
Authored: Tue Jan 20 19:05:33 2015 -0800
Committer: Zhe Zhang <zhz@apache.org>
Committed: Mon Jan 26 09:43:25 2015 -0800

----------------------------------------------------------------------
 .../hdfs/server/datanode/BlockReceiver.java     |  58 ++--
 .../hdfs/server/datanode/BlockSender.java       |  10 +
 .../hdfs/server/datanode/ReplicaHandler.java    |  49 ++++
 .../server/datanode/fsdataset/FsDatasetSpi.java |  13 +-
 .../datanode/fsdataset/FsVolumeReference.java   |  48 ++++
 .../server/datanode/fsdataset/FsVolumeSpi.java  |  10 +
 .../datanode/fsdataset/ReplicaInputStreams.java |   6 +-
 .../impl/FsDatasetAsyncDiskService.java         |  16 +-
 .../datanode/fsdataset/impl/FsDatasetImpl.java  | 284 ++++++++++++-------
 .../datanode/fsdataset/impl/FsVolumeImpl.java   | 121 +++++++-
 .../datanode/fsdataset/impl/FsVolumeList.java   |  76 ++++-
 .../impl/RamDiskAsyncLazyPersistService.java    |  19 +-
 .../src/main/proto/datatransfer.proto           |   2 +-
 .../hdfs/TestWriteBlockGetsBlockLengthHint.java |   2 +-
 .../server/datanode/SimulatedFSDataset.java     |  35 ++-
 .../hdfs/server/datanode/TestBlockRecovery.java |   2 +-
 .../datanode/TestDataNodeHotSwapVolumes.java    |  33 ++-
 .../server/datanode/TestDirectoryScanner.java   |   9 +-
 .../server/datanode/TestSimulatedFSDataset.java |   2 +-
 .../extdataset/ExternalDatasetImpl.java         |  22 +-
 .../datanode/extdataset/ExternalVolumeImpl.java |   7 +
 .../fsdataset/impl/FsVolumeListTest.java        |  94 ++++++
 .../fsdataset/impl/TestFsDatasetImpl.java       |   7 +-
 .../fsdataset/impl/TestWriteToReplica.java      |  12 +-
 24 files changed, 717 insertions(+), 220 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java
index 08c96be..df8dd5c 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java
@@ -26,7 +26,6 @@ import java.io.DataOutputStream;
 import java.io.File;
 import java.io.FileDescriptor;
 import java.io.FileOutputStream;
-import java.io.FileWriter;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
@@ -49,10 +48,8 @@ import org.apache.hadoop.hdfs.protocol.datatransfer.PacketReceiver;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PipelineAck;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.BlockOpResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status;
-import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaInputStreams;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
-import org.apache.hadoop.hdfs.server.datanode.ReplicaInPipeline;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeRegistration;
 import org.apache.hadoop.hdfs.util.DataTransferThrottler;
 import org.apache.hadoop.io.IOUtils;
@@ -125,6 +122,8 @@ class BlockReceiver implements Closeable {
 
   private boolean syncOnClose;
   private long restartBudget;
+  /** the reference of the volume where the block receiver writes to */
+  private final ReplicaHandler replicaHandler;
 
   /**
    * for replaceBlock response
@@ -179,48 +178,50 @@ class BlockReceiver implements Closeable {
       // Open local disk out
       //
       if (isDatanode) { //replication or move
-        replicaInfo = datanode.data.createTemporary(storageType, block);
+        replicaHandler = datanode.data.createTemporary(storageType, block);
       } else {
         switch (stage) {
         case PIPELINE_SETUP_CREATE:
-          replicaInfo = datanode.data.createRbw(storageType, block, allowLazyPersist);
+          replicaHandler = datanode.data.createRbw(storageType, block, allowLazyPersist);
           datanode.notifyNamenodeReceivingBlock(
-              block, replicaInfo.getStorageUuid());
+              block, replicaHandler.getReplica().getStorageUuid());
           break;
         case PIPELINE_SETUP_STREAMING_RECOVERY:
-          replicaInfo = datanode.data.recoverRbw(
+          replicaHandler = datanode.data.recoverRbw(
               block, newGs, minBytesRcvd, maxBytesRcvd);
           block.setGenerationStamp(newGs);
           break;
         case PIPELINE_SETUP_APPEND:
-          replicaInfo = datanode.data.append(block, newGs, minBytesRcvd);
+          replicaHandler = datanode.data.append(block, newGs, minBytesRcvd);
           if (datanode.blockScanner != null) { // remove from block scanner
             datanode.blockScanner.deleteBlock(block.getBlockPoolId(),
                 block.getLocalBlock());
           }
           block.setGenerationStamp(newGs);
           datanode.notifyNamenodeReceivingBlock(
-              block, replicaInfo.getStorageUuid());
+              block, replicaHandler.getReplica().getStorageUuid());
           break;
         case PIPELINE_SETUP_APPEND_RECOVERY:
-          replicaInfo = datanode.data.recoverAppend(block, newGs, minBytesRcvd);
+          replicaHandler = datanode.data.recoverAppend(block, newGs, minBytesRcvd);
           if (datanode.blockScanner != null) { // remove from block scanner
             datanode.blockScanner.deleteBlock(block.getBlockPoolId(),
                 block.getLocalBlock());
           }
           block.setGenerationStamp(newGs);
           datanode.notifyNamenodeReceivingBlock(
-              block, replicaInfo.getStorageUuid());
+              block, replicaHandler.getReplica().getStorageUuid());
           break;
         case TRANSFER_RBW:
         case TRANSFER_FINALIZED:
           // this is a transfer destination
-          replicaInfo = datanode.data.createTemporary(storageType, block);
+          replicaHandler =
+              datanode.data.createTemporary(storageType, block);
           break;
         default: throw new IOException("Unsupported stage " + stage + 
               " while receiving block " + block + " from " + inAddr);
         }
       }
+      replicaInfo = replicaHandler.getReplica();
       this.dropCacheBehindWrites = (cachingStrategy.getDropBehind() == null) ?
         datanode.getDnConf().dropCacheBehindWrites :
           cachingStrategy.getDropBehind();
@@ -339,6 +340,9 @@ class BlockReceiver implements Closeable {
     finally{
       IOUtils.closeStream(out);
     }
+    if (replicaHandler != null) {
+      IOUtils.cleanup(null, replicaHandler);
+    }
     if (measuredFlushTime) {
       datanode.metrics.addFlushNanos(flushTotalNanos);
     }
@@ -950,15 +954,12 @@ class BlockReceiver implements Closeable {
     //
     byte[] buf = new byte[sizePartialChunk];
     byte[] crcbuf = new byte[checksumSize];
-    ReplicaInputStreams instr = null;
-    try { 
-      instr = datanode.data.getTmpInputStreams(block, blkoff, ckoff);
+    try (ReplicaInputStreams instr =
+        datanode.data.getTmpInputStreams(block, blkoff, ckoff)) {
       IOUtils.readFully(instr.getDataIn(), buf, 0, sizePartialChunk);
 
       // open meta file and read in crc value computer earlier
       IOUtils.readFully(instr.getChecksumIn(), crcbuf, 0, crcbuf.length);
-    } finally {
-      IOUtils.closeStream(instr);
     }
 
     // compute crc of partial chunk from data read in the block file.
@@ -1244,28 +1245,7 @@ class BlockReceiver implements Closeable {
 
           if (lastPacketInBlock) {
             // Finalize the block and close the block file
-            try {
-              finalizeBlock(startTime);
-            } catch (ReplicaNotFoundException e) {
-              // Verify that the exception is due to volume removal.
-              FsVolumeSpi volume;
-              synchronized (datanode.data) {
-                volume = datanode.data.getVolume(block);
-              }
-              if (volume == null) {
-                // ReplicaInfo has been removed due to the corresponding data
-                // volume has been removed. Don't need to check disk error.
-                LOG.info(myString
-                    + ": BlockReceiver is interrupted because the block pool "
-                    + block.getBlockPoolId() + " has been removed.", e);
-                sendAckUpstream(ack, expected, totalAckTimeNanos, 0,
-                    Status.OOB_INTERRUPTED);
-                running = false;
-                receiverThread.interrupt();
-                continue;
-              }
-              throw e;
-            }
+            finalizeBlock(startTime);
           }
 
           sendAckUpstream(ack, expected, totalAckTimeNanos,

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java
index 27d3e5c..182b366 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockSender.java
@@ -37,6 +37,7 @@ import org.apache.hadoop.fs.ChecksumException;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PacketHeader;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.LengthInputStream;
 import org.apache.hadoop.hdfs.util.DataTransferThrottler;
 import org.apache.hadoop.io.IOUtils;
@@ -143,6 +144,8 @@ class BlockSender implements java.io.Closeable {
   
   /** The file descriptor of the block being sent */
   private FileDescriptor blockInFd;
+  /** The reference to the volume where the block is located */
+  private FsVolumeReference volumeRef;
 
   // Cache-management related fields
   private final long readaheadLength;
@@ -257,6 +260,9 @@ class BlockSender implements java.io.Closeable {
       this.transferToAllowed = datanode.getDnConf().transferToAllowed &&
         (!is32Bit || length <= Integer.MAX_VALUE);
 
+      // Obtain a reference before reading data
+      this.volumeRef = datanode.data.getVolume(block).obtainReference();
+
       /* 
        * (corruptChecksumOK, meta_file_exist): operation
        * True,   True: will verify checksum  
@@ -420,6 +426,10 @@ class BlockSender implements java.io.Closeable {
       blockIn = null;
       blockInFd = null;
     }
+    if (volumeRef != null) {
+      IOUtils.cleanup(null, volumeRef);
+      volumeRef = null;
+    }
     // throw IOException if there is any
     if(ioe!= null) {
       throw ioe;

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaHandler.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaHandler.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaHandler.java
new file mode 100644
index 0000000..b563d7f
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaHandler.java
@@ -0,0 +1,49 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.datanode;
+
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+/**
+ * This class includes a replica being actively written and the reference to
+ * the fs volume where this replica is located.
+ */
+public class ReplicaHandler implements Closeable {
+  private final ReplicaInPipelineInterface replica;
+  private final FsVolumeReference volumeReference;
+
+  public ReplicaHandler(
+      ReplicaInPipelineInterface replica, FsVolumeReference reference) {
+    this.replica = replica;
+    this.volumeReference = reference;
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (this.volumeReference != null) {
+      volumeReference.close();
+    }
+  }
+
+  public ReplicaInPipelineInterface getReplica() {
+    return replica;
+  }
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
index da8e6d8..0d5de81 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsDatasetSpi.java
@@ -43,6 +43,7 @@ import org.apache.hadoop.hdfs.server.datanode.DataStorage;
 import org.apache.hadoop.hdfs.server.datanode.FinalizedReplica;
 import org.apache.hadoop.hdfs.server.datanode.Replica;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaInPipelineInterface;
+import org.apache.hadoop.hdfs.server.datanode.ReplicaHandler;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaInfo;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaNotFoundException;
 import org.apache.hadoop.hdfs.server.datanode.StorageLocation;
@@ -198,7 +199,7 @@ public interface FsDatasetSpi<V extends FsVolumeSpi> extends FSDatasetMBean {
    * @return the meta info of the replica which is being written to
    * @throws IOException if an error occurs
    */
-  public ReplicaInPipelineInterface createTemporary(StorageType storageType,
+  public ReplicaHandler createTemporary(StorageType storageType,
       ExtendedBlock b) throws IOException;
 
   /**
@@ -208,7 +209,7 @@ public interface FsDatasetSpi<V extends FsVolumeSpi> extends FSDatasetMBean {
    * @return the meta info of the replica which is being written to
    * @throws IOException if an error occurs
    */
-  public ReplicaInPipelineInterface createRbw(StorageType storageType,
+  public ReplicaHandler createRbw(StorageType storageType,
       ExtendedBlock b, boolean allowLazyPersist) throws IOException;
 
   /**
@@ -221,7 +222,7 @@ public interface FsDatasetSpi<V extends FsVolumeSpi> extends FSDatasetMBean {
    * @return the meta info of the replica which is being written to
    * @throws IOException if an error occurs
    */
-  public ReplicaInPipelineInterface recoverRbw(ExtendedBlock b, 
+  public ReplicaHandler recoverRbw(ExtendedBlock b,
       long newGS, long minBytesRcvd, long maxBytesRcvd) throws IOException;
 
   /**
@@ -241,7 +242,7 @@ public interface FsDatasetSpi<V extends FsVolumeSpi> extends FSDatasetMBean {
    * @return the meata info of the replica which is being written to
    * @throws IOException
    */
-  public ReplicaInPipelineInterface append(ExtendedBlock b, long newGS,
+  public ReplicaHandler append(ExtendedBlock b, long newGS,
       long expectedBlockLen) throws IOException;
 
   /**
@@ -254,8 +255,8 @@ public interface FsDatasetSpi<V extends FsVolumeSpi> extends FSDatasetMBean {
    * @return the meta info of the replica which is being written to
    * @throws IOException
    */
-  public ReplicaInPipelineInterface recoverAppend(ExtendedBlock b, long newGS,
-      long expectedBlockLen) throws IOException;
+  public ReplicaHandler recoverAppend(
+      ExtendedBlock b, long newGS, long expectedBlockLen) throws IOException;
   
   /**
    * Recover a failed pipeline close

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeReference.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeReference.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeReference.java
new file mode 100644
index 0000000..e61a059
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeReference.java
@@ -0,0 +1,48 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hdfs.server.datanode.fsdataset;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+/**
+ * This is the interface for holding reference count as AutoClosable resource.
+ * It increases the reference count by one in the constructor, and decreases
+ * the reference count by one in {@link #close()}.
+ *
+ * <pre>
+ *  {@code
+ *    try (FsVolumeReference ref = volume.obtainReference()) {
+ *      // Do IOs on the volume
+ *      volume.createRwb(...);
+ *      ...
+ *    }
+ *  }
+ * </pre>
+ */
+public interface FsVolumeReference extends Closeable {
+  /**
+   * Descrese the reference count of the volume.
+   * @throws IOException it never throws IOException.
+   */
+  @Override
+  public void close() throws IOException;
+
+  /** Returns the underlying volume object */
+  public FsVolumeSpi getVolume();
+}

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java
index 8ebf2b4..3a635b7 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java
@@ -19,6 +19,7 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.channels.ClosedChannelException;
 
 import org.apache.hadoop.hdfs.StorageType;
 
@@ -26,6 +27,15 @@ import org.apache.hadoop.hdfs.StorageType;
  * This is an interface for the underlying volume.
  */
 public interface FsVolumeSpi {
+  /**
+   * Obtain a reference object that had increased 1 reference count of the
+   * volume.
+   *
+   * It is caller's responsibility to close {@link FsVolumeReference} to decrease
+   * the reference count on the volume.
+   */
+  FsVolumeReference obtainReference() throws ClosedChannelException;
+
   /** @return the StorageUuid of the volume */
   public String getStorageID();
 

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaInputStreams.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaInputStreams.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaInputStreams.java
index 6bd7199..a8bf622 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaInputStreams.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaInputStreams.java
@@ -30,9 +30,12 @@ import org.apache.hadoop.io.IOUtils;
 public class ReplicaInputStreams implements Closeable {
   private final InputStream dataIn;
   private final InputStream checksumIn;
+  private final FsVolumeReference volumeRef;
 
   /** Create an object with a data input stream and a checksum input stream. */
-  public ReplicaInputStreams(FileDescriptor dataFd, FileDescriptor checksumFd) {
+  public ReplicaInputStreams(FileDescriptor dataFd, FileDescriptor checksumFd,
+      FsVolumeReference volumeRef) {
+    this.volumeRef = volumeRef;
     this.dataIn = new FileInputStream(dataFd);
     this.checksumIn = new FileInputStream(checksumFd);
   }
@@ -51,5 +54,6 @@ public class ReplicaInputStreams implements Closeable {
   public void close() {
     IOUtils.closeStream(dataIn);
     IOUtils.closeStream(checksumIn);
+    IOUtils.cleanup(null, volumeRef);
   }
 }
\ No newline at end of file

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
index bee7bf7..13e854f 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetAsyncDiskService.java
@@ -20,6 +20,7 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import java.io.File;
 import java.io.FileDescriptor;
+import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.LinkedBlockingQueue;
@@ -31,7 +32,9 @@ import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.protocol.BlockCommand;
+import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.nativeio.NativeIO;
 import org.apache.hadoop.io.nativeio.NativeIOException;
 
@@ -200,13 +203,13 @@ class FsDatasetAsyncDiskService {
    * Delete the block file and meta file from the disk asynchronously, adjust
    * dfsUsed statistics accordingly.
    */
-  void deleteAsync(FsVolumeImpl volume, File blockFile, File metaFile,
+  void deleteAsync(FsVolumeReference volumeRef, File blockFile, File metaFile,
       ExtendedBlock block, String trashDirectory) {
     LOG.info("Scheduling " + block.getLocalBlock()
         + " file " + blockFile + " for deletion");
     ReplicaFileDeleteTask deletionTask = new ReplicaFileDeleteTask(
-        volume, blockFile, metaFile, block, trashDirectory);
-    execute(volume.getCurrentDir(), deletionTask);
+        volumeRef, blockFile, metaFile, block, trashDirectory);
+    execute(((FsVolumeImpl) volumeRef.getVolume()).getCurrentDir(), deletionTask);
   }
   
   /** A task for deleting a block file and its associated meta file, as well
@@ -216,15 +219,17 @@ class FsDatasetAsyncDiskService {
    *  files are deleted immediately.
    */
   class ReplicaFileDeleteTask implements Runnable {
+    final FsVolumeReference volumeRef;
     final FsVolumeImpl volume;
     final File blockFile;
     final File metaFile;
     final ExtendedBlock block;
     final String trashDirectory;
     
-    ReplicaFileDeleteTask(FsVolumeImpl volume, File blockFile,
+    ReplicaFileDeleteTask(FsVolumeReference volumeRef, File blockFile,
         File metaFile, ExtendedBlock block, String trashDirectory) {
-      this.volume = volume;
+      this.volumeRef = volumeRef;
+      this.volume = (FsVolumeImpl) volumeRef.getVolume();
       this.blockFile = blockFile;
       this.metaFile = metaFile;
       this.block = block;
@@ -281,6 +286,7 @@ class FsDatasetAsyncDiskService {
         LOG.info("Deleted " + block.getBlockPoolId() + " "
             + block.getLocalBlock() + " file " + blockFile);
       }
+      IOUtils.cleanup(null, volumeRef);
     }
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
index e62986f..5347323 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java
@@ -29,6 +29,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.RandomAccessFile;
 import java.nio.ByteBuffer;
+import java.nio.channels.ClosedChannelException;
 import java.nio.channels.FileChannel;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -75,6 +76,7 @@ import org.apache.hadoop.hdfs.server.datanode.Replica;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaAlreadyExistsException;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaBeingWritten;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaInPipeline;
+import org.apache.hadoop.hdfs.server.datanode.ReplicaHandler;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaInfo;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaNotFoundException;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaUnderRecovery;
@@ -82,6 +84,7 @@ import org.apache.hadoop.hdfs.server.datanode.ReplicaWaitingToBeRecovered;
 import org.apache.hadoop.hdfs.server.datanode.StorageLocation;
 import org.apache.hadoop.hdfs.server.datanode.UnexpectedReplicaStateException;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.LengthInputStream;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaInputStreams;
@@ -137,22 +140,26 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
   @Override // FsDatasetSpi
   public StorageReport[] getStorageReports(String bpid)
       throws IOException {
-    StorageReport[] reports;
+    List<StorageReport> reports;
     synchronized (statsLock) {
       List<FsVolumeImpl> curVolumes = getVolumes();
-      reports = new StorageReport[curVolumes.size()];
-      int i = 0;
+      reports = new ArrayList<>(curVolumes.size());
       for (FsVolumeImpl volume : curVolumes) {
-        reports[i++] = new StorageReport(volume.toDatanodeStorage(),
-                                         false,
-                                         volume.getCapacity(),
-                                         volume.getDfsUsed(),
-                                         volume.getAvailable(),
-                                         volume.getBlockPoolUsed(bpid));
+        try (FsVolumeReference ref = volume.obtainReference()) {
+          StorageReport sr = new StorageReport(volume.toDatanodeStorage(),
+              false,
+              volume.getCapacity(),
+              volume.getDfsUsed(),
+              volume.getAvailable(),
+              volume.getBlockPoolUsed(bpid));
+          reports.add(sr);
+        } catch (ClosedChannelException e) {
+          continue;
+        }
       }
     }
 
-    return reports;
+    return reports.toArray(new StorageReport[reports.size()]);
   }
 
   @Override
@@ -622,17 +629,24 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
   public synchronized ReplicaInputStreams getTmpInputStreams(ExtendedBlock b, 
                           long blkOffset, long ckoff) throws IOException {
     ReplicaInfo info = getReplicaInfo(b);
-    File blockFile = info.getBlockFile();
-    RandomAccessFile blockInFile = new RandomAccessFile(blockFile, "r");
-    if (blkOffset > 0) {
-      blockInFile.seek(blkOffset);
-    }
-    File metaFile = info.getMetaFile();
-    RandomAccessFile metaInFile = new RandomAccessFile(metaFile, "r");
-    if (ckoff > 0) {
-      metaInFile.seek(ckoff);
+    FsVolumeReference ref = info.getVolume().obtainReference();
+    try {
+      File blockFile = info.getBlockFile();
+      RandomAccessFile blockInFile = new RandomAccessFile(blockFile, "r");
+      if (blkOffset > 0) {
+        blockInFile.seek(blkOffset);
+      }
+      File metaFile = info.getMetaFile();
+      RandomAccessFile metaInFile = new RandomAccessFile(metaFile, "r");
+      if (ckoff > 0) {
+        metaInFile.seek(ckoff);
+      }
+      return new ReplicaInputStreams(
+          blockInFile.getFD(), metaInFile.getFD(), ref);
+    } catch (IOException e) {
+      IOUtils.cleanup(null, ref);
+      throw e;
     }
-    return new ReplicaInputStreams(blockInFile.getFD(), metaInFile.getFD());
   }
 
   static File moveBlockFiles(Block b, File srcfile, File destdir)
@@ -732,26 +746,27 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
           + replicaInfo.getVolume().getStorageType());
     }
 
-    FsVolumeImpl targetVolume = volumes.getNextVolume(targetStorageType,
-        block.getNumBytes());
-    File oldBlockFile = replicaInfo.getBlockFile();
-    File oldMetaFile = replicaInfo.getMetaFile();
+    try (FsVolumeReference volumeRef = volumes.getNextVolume(
+        targetStorageType, block.getNumBytes())) {
+      File oldBlockFile = replicaInfo.getBlockFile();
+      File oldMetaFile = replicaInfo.getMetaFile();
+      FsVolumeImpl targetVolume = (FsVolumeImpl) volumeRef.getVolume();
+      // Copy files to temp dir first
+      File[] blockFiles = copyBlockFiles(block.getBlockId(),
+          block.getGenerationStamp(), oldMetaFile, oldBlockFile,
+          targetVolume.getTmpDir(block.getBlockPoolId()),
+          replicaInfo.isOnTransientStorage());
 
-    // Copy files to temp dir first
-    File[] blockFiles = copyBlockFiles(block.getBlockId(),
-        block.getGenerationStamp(), oldMetaFile, oldBlockFile,
-        targetVolume.getTmpDir(block.getBlockPoolId()),
-        replicaInfo.isOnTransientStorage());
+      ReplicaInfo newReplicaInfo = new ReplicaInPipeline(
+          replicaInfo.getBlockId(), replicaInfo.getGenerationStamp(),
+          targetVolume, blockFiles[0].getParentFile(), 0);
+      newReplicaInfo.setNumBytes(blockFiles[1].length());
+      // Finalize the copied files
+      newReplicaInfo = finalizeReplica(block.getBlockPoolId(), newReplicaInfo);
 
-    ReplicaInfo newReplicaInfo = new ReplicaInPipeline(
-        replicaInfo.getBlockId(), replicaInfo.getGenerationStamp(),
-        targetVolume, blockFiles[0].getParentFile(), 0);
-    newReplicaInfo.setNumBytes(blockFiles[1].length());
-    // Finalize the copied files
-    newReplicaInfo = finalizeReplica(block.getBlockPoolId(), newReplicaInfo);
-
-    removeOldReplica(replicaInfo, newReplicaInfo, oldBlockFile, oldMetaFile,
-        oldBlockFile.length(), oldMetaFile.length(), block.getBlockPoolId());
+      removeOldReplica(replicaInfo, newReplicaInfo, oldBlockFile, oldMetaFile,
+          oldBlockFile.length(), oldMetaFile.length(), block.getBlockPoolId());
+    }
 
     // Replace the old block if any to reschedule the scanning.
     datanode.getBlockScanner().addBlock(block);
@@ -870,7 +885,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
 
 
   @Override  // FsDatasetSpi
-  public synchronized ReplicaInPipeline append(ExtendedBlock b,
+  public synchronized ReplicaHandler append(ExtendedBlock b,
       long newGS, long expectedBlockLen) throws IOException {
     // If the block was successfully finalized because all packets
     // were successfully processed at the Datanode but the ack for
@@ -895,8 +910,16 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
           " expected length is " + expectedBlockLen);
     }
 
-    return append(b.getBlockPoolId(), (FinalizedReplica)replicaInfo, newGS,
-        b.getNumBytes());
+    FsVolumeReference ref = replicaInfo.getVolume().obtainReference();
+    ReplicaBeingWritten replica = null;
+    try {
+      replica = append(b.getBlockPoolId(), (FinalizedReplica)replicaInfo, newGS,
+          b.getNumBytes());
+    } catch (IOException e) {
+      IOUtils.cleanup(null, ref);
+      throw e;
+    }
+    return new ReplicaHandler(replica, ref);
   }
   
   /** Append to a finalized replica
@@ -1017,22 +1040,30 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     
     return replicaInfo;
   }
-  
+
   @Override  // FsDatasetSpi
-  public synchronized ReplicaInPipeline recoverAppend(ExtendedBlock b,
-      long newGS, long expectedBlockLen) throws IOException {
+  public synchronized ReplicaHandler recoverAppend(
+      ExtendedBlock b, long newGS, long expectedBlockLen) throws IOException {
     LOG.info("Recover failed append to " + b);
 
     ReplicaInfo replicaInfo = recoverCheck(b, newGS, expectedBlockLen);
 
-    // change the replica's state/gs etc.
-    if (replicaInfo.getState() == ReplicaState.FINALIZED ) {
-      return append(b.getBlockPoolId(), (FinalizedReplica) replicaInfo, newGS, 
-          b.getNumBytes());
-    } else { //RBW
-      bumpReplicaGS(replicaInfo, newGS);
-      return (ReplicaBeingWritten)replicaInfo;
+    FsVolumeReference ref = replicaInfo.getVolume().obtainReference();
+    ReplicaBeingWritten replica;
+    try {
+      // change the replica's state/gs etc.
+      if (replicaInfo.getState() == ReplicaState.FINALIZED) {
+        replica = append(b.getBlockPoolId(), (FinalizedReplica) replicaInfo,
+                         newGS, b.getNumBytes());
+      } else { //RBW
+        bumpReplicaGS(replicaInfo, newGS);
+        replica = (ReplicaBeingWritten) replicaInfo;
+      }
+    } catch (IOException e) {
+      IOUtils.cleanup(null, ref);
+      throw e;
     }
+    return new ReplicaHandler(replica, ref);
   }
 
   @Override // FsDatasetSpi
@@ -1080,8 +1111,9 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
   }
 
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipeline createRbw(StorageType storageType,
-      ExtendedBlock b, boolean allowLazyPersist) throws IOException {
+  public synchronized ReplicaHandler createRbw(
+      StorageType storageType, ExtendedBlock b, boolean allowLazyPersist)
+      throws IOException {
     ReplicaInfo replicaInfo = volumeMap.get(b.getBlockPoolId(),
         b.getBlockId());
     if (replicaInfo != null) {
@@ -1090,15 +1122,15 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       " and thus cannot be created.");
     }
     // create a new block
-    FsVolumeImpl v;
+    FsVolumeReference ref;
     while (true) {
       try {
         if (allowLazyPersist) {
           // First try to place the block on a transient volume.
-          v = volumes.getNextTransientVolume(b.getNumBytes());
+          ref = volumes.getNextTransientVolume(b.getNumBytes());
           datanode.getMetrics().incrRamDiskBlocksWrite();
         } else {
-          v = volumes.getNextVolume(storageType, b.getNumBytes());
+          ref = volumes.getNextVolume(storageType, b.getNumBytes());
         }
       } catch (DiskOutOfSpaceException de) {
         if (allowLazyPersist) {
@@ -1110,18 +1142,25 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       }
       break;
     }
+    FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
     // create an rbw file to hold block in the designated volume
-    File f = v.createRbwFile(b.getBlockPoolId(), b.getLocalBlock());
+    File f;
+    try {
+      f = v.createRbwFile(b.getBlockPoolId(), b.getLocalBlock());
+    } catch (IOException e) {
+      IOUtils.cleanup(null, ref);
+      throw e;
+    }
+
     ReplicaBeingWritten newReplicaInfo = new ReplicaBeingWritten(b.getBlockId(), 
         b.getGenerationStamp(), v, f.getParentFile(), b.getNumBytes());
     volumeMap.add(b.getBlockPoolId(), newReplicaInfo);
-
-    return newReplicaInfo;
+    return new ReplicaHandler(newReplicaInfo, ref);
   }
-  
+
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipeline recoverRbw(ExtendedBlock b,
-      long newGS, long minBytesRcvd, long maxBytesRcvd)
+  public synchronized ReplicaHandler recoverRbw(
+      ExtendedBlock b, long newGS, long minBytesRcvd, long maxBytesRcvd)
       throws IOException {
     LOG.info("Recover RBW replica " + b);
 
@@ -1160,20 +1199,25 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
           minBytesRcvd + ", " + maxBytesRcvd + "].");
     }
 
-    // Truncate the potentially corrupt portion.
-    // If the source was client and the last node in the pipeline was lost,
-    // any corrupt data written after the acked length can go unnoticed. 
-    if (numBytes > bytesAcked) {
-      final File replicafile = rbw.getBlockFile();
-      truncateBlock(replicafile, rbw.getMetaFile(), numBytes, bytesAcked);
-      rbw.setNumBytes(bytesAcked);
-      rbw.setLastChecksumAndDataLen(bytesAcked, null);
-    }
+    FsVolumeReference ref = rbw.getVolume().obtainReference();
+    try {
+      // Truncate the potentially corrupt portion.
+      // If the source was client and the last node in the pipeline was lost,
+      // any corrupt data written after the acked length can go unnoticed.
+      if (numBytes > bytesAcked) {
+        final File replicafile = rbw.getBlockFile();
+        truncateBlock(replicafile, rbw.getMetaFile(), numBytes, bytesAcked);
+        rbw.setNumBytes(bytesAcked);
+        rbw.setLastChecksumAndDataLen(bytesAcked, null);
+      }
 
-    // bump the replica's generation stamp to newGS
-    bumpReplicaGS(rbw, newGS);
-    
-    return rbw;
+      // bump the replica's generation stamp to newGS
+      bumpReplicaGS(rbw, newGS);
+    } catch (IOException e) {
+      IOUtils.cleanup(null, ref);
+      throw e;
+    }
+    return new ReplicaHandler(rbw, ref);
   }
   
   @Override // FsDatasetSpi
@@ -1238,8 +1282,8 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
   }
 
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipeline createTemporary(StorageType storageType,
-      ExtendedBlock b) throws IOException {
+  public synchronized ReplicaHandler createTemporary(
+      StorageType storageType, ExtendedBlock b) throws IOException {
     ReplicaInfo replicaInfo = volumeMap.get(b.getBlockPoolId(), b.getBlockId());
     if (replicaInfo != null) {
       if (replicaInfo.getGenerationStamp() < b.getGenerationStamp()
@@ -1254,14 +1298,22 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
             " and thus cannot be created.");
       }
     }
-    
-    FsVolumeImpl v = volumes.getNextVolume(storageType, b.getNumBytes());
+
+    FsVolumeReference ref = volumes.getNextVolume(storageType, b.getNumBytes());
+    FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
     // create a temporary file to hold block in the designated volume
-    File f = v.createTmpFile(b.getBlockPoolId(), b.getLocalBlock());
+    File f;
+    try {
+      f = v.createTmpFile(b.getBlockPoolId(), b.getLocalBlock());
+    } catch (IOException e) {
+      IOUtils.cleanup(null, ref);
+      throw e;
+    }
+
     ReplicaInPipeline newReplicaInfo = new ReplicaInPipeline(b.getBlockId(), 
         b.getGenerationStamp(), v, f.getParentFile(), 0);
     volumeMap.add(b.getBlockPoolId(), newReplicaInfo);
-    return newReplicaInfo;
+    return new ReplicaHandler(newReplicaInfo, ref);
   }
 
   /**
@@ -1644,10 +1696,15 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       // Delete the block asynchronously to make sure we can do it fast enough.
       // It's ok to unlink the block file before the uncache operation
       // finishes.
-      asyncDiskService.deleteAsync(v, f,
-          FsDatasetUtil.getMetaFile(f, invalidBlks[i].getGenerationStamp()),
-          new ExtendedBlock(bpid, invalidBlks[i]),
-          dataStorage.getTrashDirectoryForBlockFile(bpid, f));
+      try {
+        asyncDiskService.deleteAsync(v.obtainReference(), f,
+            FsDatasetUtil.getMetaFile(f, invalidBlks[i].getGenerationStamp()),
+            new ExtendedBlock(bpid, invalidBlks[i]),
+            dataStorage.getTrashDirectoryForBlockFile(bpid, f));
+      } catch (ClosedChannelException e) {
+        LOG.warn("Volume " + v + " is closed, ignore the deletion task for " +
+            "block " + invalidBlks[i]);
+      }
     }
     if (!errors.isEmpty()) {
       StringBuilder b = new StringBuilder("Failed to delete ")
@@ -2282,14 +2339,17 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       ReplicaUnderRecovery replicaInfo, String bpid, long newBlkId, long newGS)
       throws IOException {
     String blockFileName = Block.BLOCK_FILE_PREFIX + newBlkId;
-    FsVolumeImpl v = volumes.getNextVolume(
-        replicaInfo.getVolume().getStorageType(), replicaInfo.getNumBytes());
-    final File tmpDir = v.getBlockPoolSlice(bpid).getTmpDir();
-    final File destDir = DatanodeUtil.idToBlockDir(tmpDir, newBlkId);
-    final File dstBlockFile = new File(destDir, blockFileName);
-    final File dstMetaFile = FsDatasetUtil.getMetaFile(dstBlockFile, newGS);
-    return copyBlockFiles(replicaInfo.getMetaFile(), replicaInfo.getBlockFile(),
-        dstMetaFile, dstBlockFile, true);
+    try (FsVolumeReference ref = volumes.getNextVolume(
+        replicaInfo.getVolume().getStorageType(), replicaInfo.getNumBytes())) {
+      FsVolumeImpl v = (FsVolumeImpl) ref.getVolume();
+      final File tmpDir = v.getBlockPoolSlice(bpid).getTmpDir();
+      final File destDir = DatanodeUtil.idToBlockDir(tmpDir, newBlkId);
+      final File dstBlockFile = new File(destDir, blockFileName);
+      final File dstMetaFile = FsDatasetUtil.getMetaFile(dstBlockFile, newGS);
+      return copyBlockFiles(replicaInfo.getMetaFile(),
+          replicaInfo.getBlockFile(),
+          dstMetaFile, dstBlockFile, true);
+    }
   }
 
   @Override // FsDatasetSpi
@@ -2345,9 +2405,11 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     for (FsVolumeImpl volume : getVolumes()) {
       long used = 0;
       long free = 0;
-      try {
+      try (FsVolumeReference ref = volume.obtainReference()) {
         used = volume.getDfsUsed();
         free = volume.getAvailable();
+      } catch (ClosedChannelException e) {
+        continue;
       } catch (IOException e) {
         LOG.warn(e.getMessage());
         used = 0;
@@ -2379,15 +2441,23 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     List<FsVolumeImpl> curVolumes = getVolumes();
     if (!force) {
       for (FsVolumeImpl volume : curVolumes) {
-        if (!volume.isBPDirEmpty(bpid)) {
-          LOG.warn(bpid + " has some block files, cannot delete unless forced");
-          throw new IOException("Cannot delete block pool, "
-              + "it contains some block files");
+        try (FsVolumeReference ref = volume.obtainReference()) {
+          if (!volume.isBPDirEmpty(bpid)) {
+            LOG.warn(bpid + " has some block files, cannot delete unless forced");
+            throw new IOException("Cannot delete block pool, "
+                + "it contains some block files");
+          }
+        } catch (ClosedChannelException e) {
+          // ignore.
         }
       }
     }
     for (FsVolumeImpl volume : curVolumes) {
-      volume.deleteBPDirectories(bpid, force);
+      try (FsVolumeReference ref = volume.obtainReference()) {
+        volume.deleteBPDirectories(bpid, force);
+      } catch (ClosedChannelException e) {
+        // ignore.
+      }
     }
   }
   
@@ -2620,6 +2690,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
      */
     private boolean saveNextReplica() {
       RamDiskReplica block = null;
+      FsVolumeReference targetReference;
       FsVolumeImpl targetVolume;
       ReplicaInfo replicaInfo;
       boolean succeeded = false;
@@ -2637,8 +2708,9 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
             if (replicaInfo != null &&
                 replicaInfo.getVolume().isTransientStorage()) {
               // Pick a target volume to persist the block.
-              targetVolume = volumes.getNextVolume(
+              targetReference = volumes.getNextVolume(
                   StorageType.DEFAULT, replicaInfo.getNumBytes());
+              targetVolume = (FsVolumeImpl) targetReference.getVolume();
 
               ramDiskReplicaTracker.recordStartLazyPersist(
                   block.getBlockPoolId(), block.getBlockId(), targetVolume);
@@ -2654,7 +2726,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
                   block.getBlockPoolId(), block.getBlockId(),
                   replicaInfo.getGenerationStamp(), block.getCreationTime(),
                   replicaInfo.getMetaFile(), replicaInfo.getBlockFile(),
-                  targetVolume);
+                  targetReference);
             }
           }
         }
@@ -2678,9 +2750,13 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       // Don't worry about fragmentation for now. We don't expect more than one
       // transient volume per DN.
       for (FsVolumeImpl v : getVolumes()) {
-        if (v.isTransientStorage()) {
-          capacity += v.getCapacity();
-          free += v.getAvailable();
+        try (FsVolumeReference ref = v.obtainReference()) {
+          if (v.isTransientStorage()) {
+            capacity += v.getCapacity();
+            free += v.getAvailable();
+          }
+        } catch (ClosedChannelException e) {
+          // ignore.
         }
       }
 

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
index 48427ad..7c8384d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeImpl.java
@@ -19,6 +19,7 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.channels.ClosedChannelException;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
@@ -31,6 +32,8 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 
 import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Joiner;
+import com.google.common.base.Preconditions;
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.DF;
@@ -40,8 +43,10 @@ import org.apache.hadoop.hdfs.StorageType;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.datanode.DataStorage;
 import org.apache.hadoop.hdfs.server.datanode.DatanodeUtil;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeStorage;
+import org.apache.hadoop.util.CloseableReferenceCount;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
 
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
@@ -62,6 +67,7 @@ public class FsVolumeImpl implements FsVolumeSpi {
   private final File currentDir;    // <StorageDirectory>/current
   private final DF usage;           
   private final long reserved;
+  private CloseableReferenceCount reference = new CloseableReferenceCount();
 
   // Disk space reserved for open blocks.
   private AtomicLong reservedForRbw;
@@ -99,6 +105,10 @@ public class FsVolumeImpl implements FsVolumeSpi {
     if (storageType.isTransient()) {
       return null;
     }
+    if (dataset.datanode == null) {
+      // FsVolumeImpl is used in test.
+      return null;
+    }
 
     final int maxNumThreads = dataset.datanode.getConf().getInt(
         DFSConfigKeys.DFS_DATANODE_FSDATASETCACHE_MAX_THREADS_PER_VOLUME_KEY,
@@ -116,7 +126,114 @@ public class FsVolumeImpl implements FsVolumeSpi {
     executor.allowCoreThreadTimeOut(true);
     return executor;
   }
-  
+
+  private void printReferenceTraceInfo(String op) {
+    StackTraceElement[] stack = Thread.currentThread().getStackTrace();
+    for (StackTraceElement ste : stack) {
+      switch (ste.getMethodName()) {
+      case "getDfsUsed":
+      case "getBlockPoolUsed":
+      case "getAvailable":
+      case "getVolumeMap":
+        return;
+      default:
+        break;
+      }
+    }
+    FsDatasetImpl.LOG.trace("Reference count: " + op + " " + this + ": " +
+        this.reference.getReferenceCount());
+    FsDatasetImpl.LOG.trace(
+        Joiner.on("\n").join(Thread.currentThread().getStackTrace()));
+  }
+
+  /**
+   * Increase the reference count. The caller must increase the reference count
+   * before issuing IOs.
+   *
+   * @throws IOException if the volume is already closed.
+   */
+  private void reference() throws ClosedChannelException {
+    this.reference.reference();
+    if (FsDatasetImpl.LOG.isTraceEnabled()) {
+      printReferenceTraceInfo("incr");
+    }
+  }
+
+  /**
+   * Decrease the reference count.
+   */
+  private void unreference() {
+    if (FsDatasetImpl.LOG.isTraceEnabled()) {
+      printReferenceTraceInfo("desc");
+    }
+    if (FsDatasetImpl.LOG.isDebugEnabled()) {
+      if (reference.getReferenceCount() <= 0) {
+        FsDatasetImpl.LOG.debug("Decrease reference count <= 0 on " + this +
+          Joiner.on("\n").join(Thread.currentThread().getStackTrace()));
+      }
+    }
+    checkReference();
+    this.reference.unreference();
+  }
+
+  private static class FsVolumeReferenceImpl implements FsVolumeReference {
+    private final FsVolumeImpl volume;
+
+    FsVolumeReferenceImpl(FsVolumeImpl volume) throws ClosedChannelException {
+      this.volume = volume;
+      volume.reference();
+    }
+
+    /**
+     * Decreases the reference count.
+     * @throws IOException it never throws IOException.
+     */
+    @Override
+    public void close() throws IOException {
+      volume.unreference();
+    }
+
+    @Override
+    public FsVolumeSpi getVolume() {
+      return this.volume;
+    }
+  }
+
+  @Override
+  public FsVolumeReference obtainReference() throws ClosedChannelException {
+    return new FsVolumeReferenceImpl(this);
+  }
+
+  private void checkReference() {
+    Preconditions.checkState(reference.getReferenceCount() > 0);
+  }
+
+  /**
+   * Close this volume and wait all other threads to release the reference count
+   * on this volume.
+   * @throws IOException if the volume is closed or the waiting is interrupted.
+   */
+  void closeAndWait() throws IOException {
+    try {
+      this.reference.setClosed();
+    } catch (ClosedChannelException e) {
+      throw new IOException("The volume has already closed.", e);
+    }
+    final int SLEEP_MILLIS = 500;
+    while (this.reference.getReferenceCount() > 0) {
+      if (FsDatasetImpl.LOG.isDebugEnabled()) {
+        FsDatasetImpl.LOG.debug(String.format(
+            "The reference count for %s is %d, wait to be 0.",
+            this, reference.getReferenceCount()));
+      }
+      try {
+        Thread.sleep(SLEEP_MILLIS);
+      } catch (InterruptedException e) {
+        throw new IOException(e);
+      }
+    }
+  }
+
   File getCurrentDir() {
     return currentDir;
   }
@@ -250,6 +367,7 @@ public class FsVolumeImpl implements FsVolumeSpi {
    * the block is finalized.
    */
   File createTmpFile(String bpid, Block b) throws IOException {
+    checkReference();
     return getBlockPoolSlice(bpid).createTmpFile(b);
   }
 
@@ -282,6 +400,7 @@ public class FsVolumeImpl implements FsVolumeSpi {
    * the block is finalized.
    */
   File createRbwFile(String bpid, Block b) throws IOException {
+    checkReference();
     reserveSpaceForRbw(b.getNumBytes());
     return getBlockPoolSlice(bpid).createRbwFile(b);
   }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
index c02603d..ba19897 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsVolumeList.java
@@ -18,6 +18,7 @@
 package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 
 import java.io.IOException;
+import java.nio.channels.ClosedChannelException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -28,6 +29,7 @@ import java.util.concurrent.atomic.AtomicReference;
 import com.google.common.collect.Lists;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.StorageType;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.VolumeChoosingPolicy;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
@@ -58,6 +60,21 @@ class FsVolumeList {
     return Collections.unmodifiableList(Arrays.asList(volumes.get()));
   }
 
+  private FsVolumeReference chooseVolume(List<FsVolumeImpl> list, long blockSize)
+      throws IOException {
+    while (true) {
+      FsVolumeImpl volume = blockChooser.chooseVolume(list, blockSize);
+      try {
+        return volume.obtainReference();
+      } catch (ClosedChannelException e) {
+        FsDatasetImpl.LOG.warn("Chosen a closed volume: " + volume);
+        // blockChooser.chooseVolume returns DiskOutOfSpaceException when the list
+        // is empty, indicating that all volumes are closed.
+        list.remove(volume);
+      }
+    }
+  }
+
   /** 
    * Get next volume.
    *
@@ -65,7 +82,7 @@ class FsVolumeList {
    * @param storageType the desired {@link StorageType} 
    * @return next volume to store the block in.
    */
-  FsVolumeImpl getNextVolume(StorageType storageType, long blockSize)
+  FsVolumeReference getNextVolume(StorageType storageType, long blockSize)
       throws IOException {
     // Get a snapshot of currently available volumes.
     final FsVolumeImpl[] curVolumes = volumes.get();
@@ -75,7 +92,7 @@ class FsVolumeList {
         list.add(v);
       }
     }
-    return blockChooser.chooseVolume(list, blockSize);
+    return chooseVolume(list, blockSize);
   }
 
   /**
@@ -84,7 +101,7 @@ class FsVolumeList {
    * @param blockSize free space needed on the volume
    * @return next volume to store the block in.
    */
-  FsVolumeImpl getNextTransientVolume(long blockSize) throws IOException {
+  FsVolumeReference getNextTransientVolume(long blockSize) throws IOException {
     // Get a snapshot of currently available volumes.
     final List<FsVolumeImpl> curVolumes = getVolumes();
     final List<FsVolumeImpl> list = new ArrayList<>(curVolumes.size());
@@ -93,13 +110,17 @@ class FsVolumeList {
         list.add(v);
       }
     }
-    return blockChooser.chooseVolume(list, blockSize);
+    return chooseVolume(list, blockSize);
   }
 
   long getDfsUsed() throws IOException {
     long dfsUsed = 0L;
     for (FsVolumeImpl v : volumes.get()) {
-      dfsUsed += v.getDfsUsed();
+      try(FsVolumeReference ref = v.obtainReference()) {
+        dfsUsed += v.getDfsUsed();
+      } catch (ClosedChannelException e) {
+        // ignore.
+      }
     }
     return dfsUsed;
   }
@@ -107,7 +128,11 @@ class FsVolumeList {
   long getBlockPoolUsed(String bpid) throws IOException {
     long dfsUsed = 0L;
     for (FsVolumeImpl v : volumes.get()) {
-      dfsUsed += v.getBlockPoolUsed(bpid);
+      try (FsVolumeReference ref = v.obtainReference()) {
+        dfsUsed += v.getBlockPoolUsed(bpid);
+      } catch (ClosedChannelException e) {
+        // ignore.
+      }
     }
     return dfsUsed;
   }
@@ -115,7 +140,11 @@ class FsVolumeList {
   long getCapacity() {
     long capacity = 0L;
     for (FsVolumeImpl v : volumes.get()) {
-      capacity += v.getCapacity();
+      try (FsVolumeReference ref = v.obtainReference()) {
+        capacity += v.getCapacity();
+      } catch (IOException e) {
+        // ignore.
+      }
     }
     return capacity;
   }
@@ -123,7 +152,11 @@ class FsVolumeList {
   long getRemaining() throws IOException {
     long remaining = 0L;
     for (FsVolumeSpi vol : volumes.get()) {
-      remaining += vol.getAvailable();
+      try (FsVolumeReference ref = vol.obtainReference()) {
+        remaining += vol.getAvailable();
+      } catch (ClosedChannelException e) {
+        // ignore
+      }
     }
     return remaining;
   }
@@ -139,7 +172,7 @@ class FsVolumeList {
     for (final FsVolumeImpl v : volumes.get()) {
       Thread t = new Thread() {
         public void run() {
-          try {
+          try (FsVolumeReference ref = v.obtainReference()) {
             FsDatasetImpl.LOG.info("Adding replicas to map for block pool " +
                 bpid + " on volume " + v + "...");
             long startTime = Time.monotonicNow();
@@ -147,6 +180,9 @@ class FsVolumeList {
             long timeTaken = Time.monotonicNow() - startTime;
             FsDatasetImpl.LOG.info("Time to add replicas to map for block pool"
                 + " " + bpid + " on volume " + v + ": " + timeTaken + "ms");
+          } catch (ClosedChannelException e) {
+            FsDatasetImpl.LOG.info("The volume " + v + " is closed while " +
+                "addng replicas, ignored.");
           } catch (IOException ioe) {
             FsDatasetImpl.LOG.info("Caught exception while adding replicas " +
                 "from " + v + ". Will throw later.", ioe);
@@ -189,16 +225,21 @@ class FsVolumeList {
 
       for(Iterator<FsVolumeImpl> i = volumeList.iterator(); i.hasNext(); ) {
         final FsVolumeImpl fsv = i.next();
-        try {
+        try (FsVolumeReference ref = fsv.obtainReference()) {
           fsv.checkDirs();
         } catch (DiskErrorException e) {
-          FsDatasetImpl.LOG.warn("Removing failed volume " + fsv + ": ",e);
+          FsDatasetImpl.LOG.warn("Removing failed volume " + fsv + ": ", e);
           if (removedVols == null) {
-            removedVols = new ArrayList<FsVolumeImpl>(1);
+            removedVols = new ArrayList<>(1);
           }
           removedVols.add(fsv);
           removeVolume(fsv);
           numFailedVolumes++;
+        } catch (ClosedChannelException e) {
+          FsDatasetImpl.LOG.debug("Caught exception when obtaining " +
+            "reference count on closed volume", e);
+        } catch (IOException e) {
+          FsDatasetImpl.LOG.error("Unexpected IOException", e);
         }
       }
       
@@ -221,7 +262,6 @@ class FsVolumeList {
    * @param newVolume the instance of new FsVolumeImpl.
    */
   void addVolume(FsVolumeImpl newVolume) {
-    // Make a copy of volumes to add new volumes.
     while (true) {
       final FsVolumeImpl[] curVolumes = volumes.get();
       final List<FsVolumeImpl> volumeList = Lists.newArrayList(curVolumes);
@@ -252,6 +292,12 @@ class FsVolumeList {
       if (volumeList.remove(target)) {
         if (volumes.compareAndSet(curVolumes,
             volumeList.toArray(new FsVolumeImpl[volumeList.size()]))) {
+          try {
+            target.closeAndWait();
+          } catch (IOException e) {
+            FsDatasetImpl.LOG.warn(
+                "Error occurs when waiting volume to close: " + target, e);
+          }
           target.shutdown();
           FsDatasetImpl.LOG.info("Removed volume: " + target);
           break;
@@ -298,7 +344,7 @@ class FsVolumeList {
     for (final FsVolumeImpl v : volumes.get()) {
       Thread t = new Thread() {
         public void run() {
-          try {
+          try (FsVolumeReference ref = v.obtainReference()) {
             FsDatasetImpl.LOG.info("Scanning block pool " + bpid +
                 " on volume " + v + "...");
             long startTime = Time.monotonicNow();
@@ -306,6 +352,8 @@ class FsVolumeList {
             long timeTaken = Time.monotonicNow() - startTime;
             FsDatasetImpl.LOG.info("Time taken to scan block pool " + bpid +
                 " on " + v + ": " + timeTaken + "ms");
+          } catch (ClosedChannelException e) {
+            // ignore.
           } catch (IOException ioe) {
             FsDatasetImpl.LOG.info("Caught exception while scanning " + v +
                 ". Will throw later.", ioe);

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
index 5e4dd7d..cf8de0a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/RamDiskAsyncLazyPersistService.java
@@ -21,7 +21,9 @@ package org.apache.hadoop.hdfs.server.datanode.fsdataset.impl;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 
+import javax.ws.rs.HEAD;
 import java.io.File;
 import java.io.IOException;
 import java.util.HashMap;
@@ -175,13 +177,14 @@ class RamDiskAsyncLazyPersistService {
   void submitLazyPersistTask(String bpId, long blockId,
       long genStamp, long creationTime,
       File metaFile, File blockFile,
-      FsVolumeImpl targetVolume) throws IOException {
+      FsVolumeReference target) throws IOException {
     if (LOG.isDebugEnabled()) {
       LOG.debug("LazyWriter schedule async task to persist RamDisk block pool id: "
           + bpId + " block id: " + blockId);
     }
 
-    File lazyPersistDir  = targetVolume.getLazyPersistDir(bpId);
+    FsVolumeImpl volume = (FsVolumeImpl)target.getVolume();
+    File lazyPersistDir  = volume.getLazyPersistDir(bpId);
     if (!lazyPersistDir.exists() && !lazyPersistDir.mkdirs()) {
       FsDatasetImpl.LOG.warn("LazyWriter failed to create " + lazyPersistDir);
       throw new IOException("LazyWriter fail to find or create lazy persist dir: "
@@ -190,8 +193,8 @@ class RamDiskAsyncLazyPersistService {
 
     ReplicaLazyPersistTask lazyPersistTask = new ReplicaLazyPersistTask(
         bpId, blockId, genStamp, creationTime, blockFile, metaFile,
-        targetVolume, lazyPersistDir);
-    execute(targetVolume.getCurrentDir(), lazyPersistTask);
+        target, lazyPersistDir);
+    execute(volume.getCurrentDir(), lazyPersistTask);
   }
 
   class ReplicaLazyPersistTask implements Runnable {
@@ -201,13 +204,13 @@ class RamDiskAsyncLazyPersistService {
     final long creationTime;
     final File blockFile;
     final File metaFile;
-    final FsVolumeImpl targetVolume;
+    final FsVolumeReference targetVolume;
     final File lazyPersistDir;
 
     ReplicaLazyPersistTask(String bpId, long blockId,
         long genStamp, long creationTime,
         File blockFile, File metaFile,
-        FsVolumeImpl targetVolume, File lazyPersistDir) {
+        FsVolumeReference targetVolume, File lazyPersistDir) {
       this.bpId = bpId;
       this.blockId = blockId;
       this.genStamp = genStamp;
@@ -230,14 +233,14 @@ class RamDiskAsyncLazyPersistService {
     public void run() {
       boolean succeeded = false;
       final FsDatasetImpl dataset = (FsDatasetImpl)datanode.getFSDataset();
-      try {
+      try (FsVolumeReference ref = this.targetVolume) {
         // No FsDatasetImpl lock for the file copy
         File targetFiles[] = FsDatasetImpl.copyBlockFiles(
             blockId, genStamp, metaFile, blockFile, lazyPersistDir, true);
 
         // Lock FsDataSetImpl during onCompleteLazyPersist callback
         dataset.onCompleteLazyPersist(bpId, blockId,
-                creationTime, targetFiles, targetVolume);
+                creationTime, targetFiles, (FsVolumeImpl)ref.getVolume());
         succeeded = true;
       } catch (Exception e){
         FsDatasetImpl.LOG.warn(

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
index fd1ba8a..4bd7bda 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/proto/datatransfer.proto
@@ -220,7 +220,7 @@ enum Status {
   CHECKSUM_OK = 6;
   ERROR_UNSUPPORTED = 7;
   OOB_RESTART = 8;            // Quick restart
-  OOB_INTERRUPTED = 9;        // Interrupted
+  OOB_RESERVED1 = 9;          // Reserved
   OOB_RESERVED2 = 10;         // Reserved
   OOB_RESERVED3 = 11;         // Reserved
   IN_PROGRESS = 12;

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestWriteBlockGetsBlockLengthHint.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestWriteBlockGetsBlockLengthHint.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestWriteBlockGetsBlockLengthHint.java
index b7fdccf..7f318df 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestWriteBlockGetsBlockLengthHint.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestWriteBlockGetsBlockLengthHint.java
@@ -97,7 +97,7 @@ public class TestWriteBlockGetsBlockLengthHint {
      * correctly propagate the hint to FsDatasetSpi.
      */
     @Override
-    public synchronized ReplicaInPipelineInterface createRbw(
+    public synchronized ReplicaHandler createRbw(
         StorageType storageType, ExtendedBlock b, boolean allowLazyPersist)
         throws IOException {
       assertThat(b.getLocalBlock().getNumBytes(), is(EXPECTED_BLOCK_LENGTH));

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
index 28ba88d..16b6350 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
@@ -22,6 +22,7 @@ import java.io.FileDescriptor;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.channels.ClosedChannelException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -43,8 +44,8 @@ import org.apache.hadoop.hdfs.protocol.BlockLocalPathInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsBlocksMetadata;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.common.Storage;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.LengthInputStream;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaInputStreams;
@@ -147,7 +148,7 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
         oStream = null;
       }
     }
-
+    
     @Override
     public String getStorageUuid() {
       return storage.getStorageUuid();
@@ -432,6 +433,11 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
     }
 
     @Override
+    public FsVolumeReference obtainReference() throws ClosedChannelException {
+      return null;
+    }
+
+    @Override
     public String getStorageID() {
       return storage.getStorageUuid();
     }
@@ -780,8 +786,8 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
   }
 
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipelineInterface append(ExtendedBlock b,
-      long newGS, long expectedBlockLen) throws IOException {
+  public synchronized ReplicaHandler append(
+      ExtendedBlock b, long newGS, long expectedBlockLen) throws IOException {
     final Map<Block, BInfo> map = getMap(b.getBlockPoolId());
     BInfo binfo = map.get(b.getLocalBlock());
     if (binfo == null || !binfo.isFinalized()) {
@@ -789,12 +795,12 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
           + " is not valid, and cannot be appended to.");
     }
     binfo.unfinalizeBlock();
-    return binfo;
+    return new ReplicaHandler(binfo, null);
   }
 
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipelineInterface recoverAppend(ExtendedBlock b,
-      long newGS, long expectedBlockLen) throws IOException {
+  public synchronized ReplicaHandler recoverAppend(
+      ExtendedBlock b, long newGS, long expectedBlockLen) throws IOException {
     final Map<Block, BInfo> map = getMap(b.getBlockPoolId());
     BInfo binfo = map.get(b.getLocalBlock());
     if (binfo == null) {
@@ -807,7 +813,7 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
     map.remove(b);
     binfo.theBlock.setGenerationStamp(newGS);
     map.put(binfo.theBlock, binfo);
-    return binfo;
+    return new ReplicaHandler(binfo, null);
   }
 
   @Override // FsDatasetSpi
@@ -829,8 +835,9 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
   }
   
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipelineInterface recoverRbw(ExtendedBlock b,
-      long newGS, long minBytesRcvd, long maxBytesRcvd) throws IOException {
+  public synchronized ReplicaHandler recoverRbw(
+      ExtendedBlock b, long newGS, long minBytesRcvd, long maxBytesRcvd)
+      throws IOException {
     final Map<Block, BInfo> map = getMap(b.getBlockPoolId());
     BInfo binfo = map.get(b.getLocalBlock());
     if ( binfo == null) {
@@ -844,18 +851,18 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
     map.remove(b);
     binfo.theBlock.setGenerationStamp(newGS);
     map.put(binfo.theBlock, binfo);
-    return binfo;
+    return new ReplicaHandler(binfo, null);
   }
 
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipelineInterface createRbw(
+  public synchronized ReplicaHandler createRbw(
       StorageType storageType, ExtendedBlock b,
       boolean allowLazyPersist) throws IOException {
     return createTemporary(storageType, b);
   }
 
   @Override // FsDatasetSpi
-  public synchronized ReplicaInPipelineInterface createTemporary(
+  public synchronized ReplicaHandler createTemporary(
       StorageType storageType, ExtendedBlock b) throws IOException {
     if (isValidBlock(b)) {
           throw new ReplicaAlreadyExistsException("Block " + b + 
@@ -868,7 +875,7 @@ public class SimulatedFSDataset implements FsDatasetSpi<FsVolumeSpi> {
     final Map<Block, BInfo> map = getMap(b.getBlockPoolId());
     BInfo binfo = new BInfo(b.getBlockPoolId(), b.getLocalBlock(), true);
     map.put(binfo.theBlock, binfo);
-    return binfo;
+    return new ReplicaHandler(binfo, null);
   }
 
   synchronized InputStream getBlockInputStream(ExtendedBlock b

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
index 9bf5e52..c7a4084 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java
@@ -562,7 +562,7 @@ public class TestBlockRecovery {
       LOG.debug("Running " + GenericTestUtils.getMethodName());
     }
     ReplicaInPipelineInterface replicaInfo = dn.data.createRbw(
-        StorageType.DEFAULT, block, false);
+        StorageType.DEFAULT, block, false).getReplica();
     ReplicaOutputStreams streams = null;
     try {
       streams = replicaInfo.createStreams(true,

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
index d468493..dfcbb6d 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDataNodeHotSwapVolumes.java
@@ -56,6 +56,8 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.Random;
+import java.util.concurrent.BrokenBarrierException;
+import java.util.concurrent.CyclicBarrier;
 import java.util.concurrent.TimeoutException;
 
 import org.apache.commons.logging.Log;
@@ -568,7 +570,7 @@ public class TestDataNodeHotSwapVolumes {
   @Test(timeout=180000)
   public void testRemoveVolumeBeingWritten()
       throws InterruptedException, TimeoutException, ReconfigurationException,
-      IOException {
+      IOException, BrokenBarrierException {
     // test against removing volumes on the different DataNode on the pipeline.
     for (int i = 0; i < 3; i++) {
       testRemoveVolumeBeingWrittenForDatanode(i);
@@ -582,7 +584,7 @@ public class TestDataNodeHotSwapVolumes {
    */
   private void testRemoveVolumeBeingWrittenForDatanode(int dataNodeIdx)
       throws IOException, ReconfigurationException, TimeoutException,
-      InterruptedException {
+      InterruptedException, BrokenBarrierException {
     // Starts DFS cluster with 3 DataNodes to form a pipeline.
     startDFSCluster(1, 3);
 
@@ -599,11 +601,27 @@ public class TestDataNodeHotSwapVolumes {
     out.write(writeBuf);
     out.hflush();
 
+    final CyclicBarrier barrier = new CyclicBarrier(2);
+
     List<String> oldDirs = getDataDirs(dn);
-    String newDirs = oldDirs.get(1);  // Remove the first volume.
-    dn.reconfigurePropertyImpl(
-        DFSConfigKeys.DFS_DATANODE_DATA_DIR_KEY, newDirs);
+    final String newDirs = oldDirs.get(1);  // Remove the first volume.
+    final List<Exception> exceptions = new ArrayList<>();
+    Thread reconfigThread = new Thread() {
+      public void run() {
+        try {
+          barrier.await();
+          dn.reconfigurePropertyImpl(
+              DFSConfigKeys.DFS_DATANODE_DATA_DIR_KEY, newDirs);
+        } catch (ReconfigurationException |
+            InterruptedException |
+            BrokenBarrierException e) {
+          exceptions.add(e);
+        }
+      }
+    };
+    reconfigThread.start();
 
+    barrier.await();
     rb.nextBytes(writeBuf);
     out.write(writeBuf);
     out.hflush();
@@ -614,5 +632,10 @@ public class TestDataNodeHotSwapVolumes {
     // Read the content back
     byte[] content = DFSTestUtil.readFileBuffer(fs, testFile);
     assertEquals(BLOCK_SIZE, content.length);
+
+    reconfigThread.join();
+    if (!exceptions.isEmpty()) {
+      throw new IOException(exceptions.get(0).getCause());
+    }
   }
 }

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDirectoryScanner.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDirectoryScanner.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDirectoryScanner.java
index b7795b5..1b8f243 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDirectoryScanner.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDirectoryScanner.java
@@ -28,6 +28,7 @@ import static org.junit.Assert.assertTrue;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.nio.channels.ClosedChannelException;
 import java.nio.channels.FileChannel;
 import java.util.LinkedList;
 import java.util.List;
@@ -44,6 +45,7 @@ import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.server.common.GenerationStamp;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsDatasetSpi;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.impl.FsDatasetTestUtil;
 import org.apache.hadoop.io.IOUtils;
@@ -539,7 +541,12 @@ public class TestDirectoryScanner {
     public String[] getBlockPoolList() {
       return new String[0];
     }
-    
+
+    @Override
+    public FsVolumeReference obtainReference() throws ClosedChannelException {
+      return null;
+    }
+
     @Override
     public long getAvailable() throws IOException {
       return 0;

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestSimulatedFSDataset.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestSimulatedFSDataset.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestSimulatedFSDataset.java
index 099a0cd..b9adce4 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestSimulatedFSDataset.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestSimulatedFSDataset.java
@@ -67,7 +67,7 @@ public class TestSimulatedFSDataset {
       // we pass expected len as zero, - fsdataset should use the sizeof actual
       // data written
       ReplicaInPipelineInterface bInfo = fsdataset.createRbw(
-          StorageType.DEFAULT, b, false);
+          StorageType.DEFAULT, b, false).getReplica();
       ReplicaOutputStreams out = bInfo.createStreams(true,
           DataChecksum.newDataChecksum(DataChecksum.Type.CRC32, 512));
       try {

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalDatasetImpl.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalDatasetImpl.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalDatasetImpl.java
index 36036ff..f256ee6 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalDatasetImpl.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalDatasetImpl.java
@@ -144,25 +144,25 @@ public class ExternalDatasetImpl implements FsDatasetSpi<ExternalVolumeImpl> {
   @Override
   public ReplicaInputStreams getTmpInputStreams(ExtendedBlock b, long blkoff,
       long ckoff) throws IOException {
-    return new ReplicaInputStreams(FileDescriptor.in, FileDescriptor.in);
+    return new ReplicaInputStreams(FileDescriptor.in, FileDescriptor.in, null);
   }
 
   @Override
-  public ReplicaInPipelineInterface createTemporary(StorageType t, ExtendedBlock b)
+  public ReplicaHandler createTemporary(StorageType t, ExtendedBlock b)
       throws IOException {
-    return new ExternalReplicaInPipeline();
+    return new ReplicaHandler(new ExternalReplicaInPipeline(), null);
   }
 
   @Override
-  public ReplicaInPipelineInterface createRbw(StorageType t, ExtendedBlock b, boolean tf)
+  public ReplicaHandler createRbw(StorageType t, ExtendedBlock b, boolean tf)
       throws IOException {
-    return new ExternalReplicaInPipeline();
+    return new ReplicaHandler(new ExternalReplicaInPipeline(), null);
   }
 
   @Override
-  public ReplicaInPipelineInterface recoverRbw(ExtendedBlock b, long newGS,
+  public ReplicaHandler recoverRbw(ExtendedBlock b, long newGS,
       long minBytesRcvd, long maxBytesRcvd) throws IOException {
-    return new ExternalReplicaInPipeline();
+    return new ReplicaHandler(new ExternalReplicaInPipeline(), null);
   }
 
   @Override
@@ -172,15 +172,15 @@ public class ExternalDatasetImpl implements FsDatasetSpi<ExternalVolumeImpl> {
   }
 
   @Override
-  public ReplicaInPipelineInterface append(ExtendedBlock b, long newGS,
+  public ReplicaHandler append(ExtendedBlock b, long newGS,
       long expectedBlockLen) throws IOException {
-    return new ExternalReplicaInPipeline();
+    return new ReplicaHandler(new ExternalReplicaInPipeline(), null);
   }
 
   @Override
-  public ReplicaInPipelineInterface recoverAppend(ExtendedBlock b, long newGS,
+  public ReplicaHandler recoverAppend(ExtendedBlock b, long newGS,
       long expectedBlockLen) throws IOException {
-    return new ExternalReplicaInPipeline();
+    return new ReplicaHandler(new ExternalReplicaInPipeline(), null);
   }
 
   @Override

http://git-wip-us.apache.org/repos/asf/hadoop/blob/9014305e/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalVolumeImpl.java
----------------------------------------------------------------------
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalVolumeImpl.java b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalVolumeImpl.java
index 8ae4c39..857e946 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalVolumeImpl.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/extdataset/ExternalVolumeImpl.java
@@ -20,10 +20,17 @@ package org.apache.hadoop.hdfs.server.datanode.extdataset;
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.channels.ClosedChannelException;
+
 import org.apache.hadoop.hdfs.StorageType;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeReference;
 import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 
 public class ExternalVolumeImpl implements FsVolumeSpi {
+  @Override
+  public FsVolumeReference obtainReference() throws ClosedChannelException {
+    return null;
+  }
 
   @Override
   public String[] getBlockPoolList() {


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