svn merge -c 1301661 from trunk for HDFS-3088.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-0.23@1301663 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -141,6 +141,8 @@ Release 0.23.3 - UNRELEASED
     HDFS-3057. httpfs and hdfs launcher scripts should honor CATALINA_HOME 
     and HADOOP_LIBEXEC_DIR (rvs via tucu)
 
+    HDFS-3088. Move FSDatasetInterface inner classes to a package.  (szetszwo)
+
   OPTIMIZATIONS
     HDFS-2477. Optimize computing the diff between a block report and the
                namenode state. (Tomasz Nykiel via hairong)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockPoolSliceScanner.java

@@ -44,7 +44,7 @@ import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.server.common.GenerationStamp;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.util.DataTransferThrottler;
 import org.apache.hadoop.io.IOUtils;
 
@@ -72,7 +72,7 @@ class BlockPoolSliceScanner {
   private final AtomicLong lastScanTime = new AtomicLong();
 
   private final DataNode datanode;
-  private final FSDatasetInterface<? extends FSVolumeInterface> dataset;
+  private final FSDatasetInterface<? extends FsVolumeSpi> dataset;
   
   private final SortedSet<BlockScanInfo> blockInfoSet
       = new TreeSet<BlockScanInfo>();
@@ -134,7 +134,7 @@ class BlockPoolSliceScanner {
   }
   
   BlockPoolSliceScanner(String bpid, DataNode datanode,
-      FSDatasetInterface<? extends FSVolumeInterface> dataset,
+      FSDatasetInterface<? extends FsVolumeSpi> dataset,
       Configuration conf) {
     this.datanode = datanode;
     this.dataset = dataset;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockReceiver.java

@@ -38,12 +38,12 @@ import org.apache.hadoop.fs.FSOutputSummer;
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants;
-import org.apache.hadoop.hdfs.protocol.LocatedBlock;
 import org.apache.hadoop.hdfs.protocol.datatransfer.BlockConstructionStage;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PacketHeader;
 import org.apache.hadoop.hdfs.protocol.datatransfer.PipelineAck;
 import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status;
-import org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaInputStreams;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeRegistration;
 import org.apache.hadoop.hdfs.util.DataTransferThrottler;
 import org.apache.hadoop.io.IOUtils;
@@ -86,7 +86,7 @@ class BlockReceiver implements Closeable {
   private DataOutputStream mirrorOut;
   private Daemon responder = null;
   private DataTransferThrottler throttler;
-  private FSDataset.BlockWriteStreams streams;
+  private ReplicaOutputStreams streams;
   private DatanodeInfo srcDataNode = null;
   private Checksum partialCrc = null;
   private final DataNode datanode;
@@ -202,16 +202,16 @@ class BlockReceiver implements Closeable {
       this.bytesPerChecksum = diskChecksum.getBytesPerChecksum();
       this.checksumSize = diskChecksum.getChecksumSize();
 
-      this.out = streams.dataOut;
+      this.out = streams.getDataOut();
       if (out instanceof FileOutputStream) {
         this.outFd = ((FileOutputStream)out).getFD();
       } else {
         LOG.warn("Could not get file descriptor for outputstream of class " +
             out.getClass());
       }
-      this.cout = streams.checksumOut;
+      this.cout = streams.getChecksumOut();
       this.checksumOut = new DataOutputStream(new BufferedOutputStream(
-          streams.checksumOut, HdfsConstants.SMALL_BUFFER_SIZE));
+          cout, HdfsConstants.SMALL_BUFFER_SIZE));
       // write data chunk header if creating a new replica
       if (isCreate) {
         BlockMetadataHeader.writeHeader(checksumOut, diskChecksum);
@@ -856,13 +856,13 @@ class BlockReceiver implements Closeable {
     //
     byte[] buf = new byte[sizePartialChunk];
     byte[] crcbuf = new byte[checksumSize];
-    FSDataset.BlockInputStreams instr = null;
+    ReplicaInputStreams instr = null;
     try { 
       instr = datanode.data.getTmpInputStreams(block, blkoff, ckoff);
-      IOUtils.readFully(instr.dataIn, buf, 0, sizePartialChunk);
+      IOUtils.readFully(instr.getDataIn(), buf, 0, sizePartialChunk);
 
       // open meta file and read in crc value computer earlier
-      IOUtils.readFully(instr.checksumIn, crcbuf, 0, crcbuf.length);
+      IOUtils.readFully(instr.getChecksumIn(), crcbuf, 0, crcbuf.length);
     } finally {
       IOUtils.closeStream(instr);
     }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BlockVolumeChoosingPolicy.java

@@ -21,7 +21,7 @@ import java.io.IOException;
 import java.util.List;
 
 import org.apache.hadoop.classification.InterfaceAudience;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 
 /**************************************************
  * BlockVolumeChoosingPolicy allows a DataNode to
@@ -33,7 +33,7 @@ import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterfa
  *
  ***************************************************/
 @InterfaceAudience.Private
-public interface BlockVolumeChoosingPolicy<V extends FSVolumeInterface> {
+public interface BlockVolumeChoosingPolicy<V extends FsVolumeSpi> {
 
   /**
    * Returns a specific FSVolume after applying a suitable choice algorithm

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataBlockScanner.java

@@ -31,7 +31,7 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 
 /**
  * DataBlockScanner manages block scanning for all the block pools. For each
@@ -43,7 +43,7 @@ import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterfa
 public class DataBlockScanner implements Runnable {
   public static final Log LOG = LogFactory.getLog(DataBlockScanner.class);
   private final DataNode datanode;
-  private final FSDatasetInterface<? extends FSVolumeInterface> dataset;
+  private final FSDatasetInterface<? extends FsVolumeSpi> dataset;
   private final Configuration conf;
   
   /**
@@ -55,7 +55,7 @@ public class DataBlockScanner implements Runnable {
   Thread blockScannerThread = null;
   
   DataBlockScanner(DataNode datanode,
-      FSDatasetInterface<? extends FSVolumeInterface> dataset,
+      FSDatasetInterface<? extends FsVolumeSpi> dataset,
       Configuration conf) {
     this.datanode = datanode;
     this.dataset = dataset;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java

@@ -123,8 +123,8 @@ import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.StartupOption;
 import org.apache.hadoop.hdfs.server.common.JspHelper;
 import org.apache.hadoop.hdfs.server.common.StorageInfo;
 import org.apache.hadoop.hdfs.server.common.Util;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
 import org.apache.hadoop.hdfs.server.datanode.SecureDataNodeStarter.SecureResources;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.datanode.metrics.DataNodeMetrics;
 import org.apache.hadoop.hdfs.server.datanode.web.resources.DatanodeWebHdfsMethods;
 import org.apache.hadoop.hdfs.server.namenode.FileChecksumServlets;
@@ -235,7 +235,7 @@ public class DataNode extends Configured
   
   volatile boolean shouldRun = true;
   private BlockPoolManager blockPoolManager;
-  volatile FSDatasetInterface<? extends FSVolumeInterface> data = null;
+  volatile FSDatasetInterface<? extends FsVolumeSpi> data = null;
   private String clusterId = null;
 
   public final static String EMPTY_DEL_HINT = "";

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataXceiver.java

@@ -55,7 +55,7 @@ import org.apache.hadoop.hdfs.protocol.proto.DataTransferProtos.Status;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenSecretManager;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.MetaDataInputStream;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.LengthInputStream;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeRegistration;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.MD5Hash;
@@ -511,7 +511,7 @@ class DataXceiver extends Receiver implements Runnable {
     checkAccess(out, true, block, blockToken,
         Op.BLOCK_CHECKSUM, BlockTokenSecretManager.AccessMode.READ);
     updateCurrentThreadName("Reading metadata for block " + block);
-    final MetaDataInputStream metadataIn = 
+    final LengthInputStream metadataIn = 
       datanode.data.getMetaDataInputStream(block);
     final DataInputStream checksumIn = new DataInputStream(new BufferedInputStream(
         metadataIn, HdfsConstants.IO_FILE_BUFFER_SIZE));

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DirectoryScanner.java

@@ -43,7 +43,7 @@ import org.apache.hadoop.hdfs.DFSConfigKeys;
 import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.common.GenerationStamp;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.util.Daemon;
 
 /**
@@ -157,13 +157,13 @@ public class DirectoryScanner implements Runnable {
     private final long blockId;
     private final File metaFile;
     private final File blockFile;
-    private final FSVolumeInterface volume;
+    private final FsVolumeSpi volume;
 
     ScanInfo(long blockId) {
       this(blockId, null, null, null);
     }
 
-    ScanInfo(long blockId, File blockFile, File metaFile, FSVolumeInterface vol) {
+    ScanInfo(long blockId, File blockFile, File metaFile, FsVolumeSpi vol) {
       this.blockId = blockId;
       this.metaFile = metaFile;
       this.blockFile = blockFile;
@@ -182,7 +182,7 @@ public class DirectoryScanner implements Runnable {
       return blockId;
     }
 
-    FSVolumeInterface getVolume() {
+    FsVolumeSpi getVolume() {
       return volume;
     }
 
@@ -412,8 +412,8 @@ public class DirectoryScanner implements Runnable {
 
   /** Is the given volume still valid in the dataset? */
   private static boolean isValid(final FSDatasetInterface<?> dataset,
-      final FSVolumeInterface volume) {
+      final FsVolumeSpi volume) {
-    for (FSVolumeInterface vol : dataset.getVolumes()) {
+    for (FsVolumeSpi vol : dataset.getVolumes()) {
       if (vol == volume) {
         return true;
       }
@@ -424,7 +424,7 @@ public class DirectoryScanner implements Runnable {
   /** Get lists of blocks on the disk sorted by blockId, per blockpool */
   private Map<String, ScanInfo[]> getDiskReport() {
     // First get list of data directories
-    final List<? extends FSVolumeInterface> volumes = dataset.getVolumes();
+    final List<? extends FsVolumeSpi> volumes = dataset.getVolumes();
     ArrayList<ScanInfoPerBlockPool> dirReports =
       new ArrayList<ScanInfoPerBlockPool>(volumes.size());
     
@@ -473,9 +473,9 @@ public class DirectoryScanner implements Runnable {
 
   private static class ReportCompiler 
   implements Callable<ScanInfoPerBlockPool> {
-    private FSVolumeInterface volume;
+    private FsVolumeSpi volume;
 
-    public ReportCompiler(FSVolumeInterface volume) {
+    public ReportCompiler(FsVolumeSpi volume) {
       this.volume = volume;
     }
 
@@ -492,7 +492,7 @@ public class DirectoryScanner implements Runnable {
     }
 
     /** Compile list {@link ScanInfo} for the blocks in the directory <dir> */
-    private LinkedList<ScanInfo> compileReport(FSVolumeInterface vol, File dir,
+    private LinkedList<ScanInfo> compileReport(FsVolumeSpi vol, File dir,
         LinkedList<ScanInfo> report) {
       File[] files;
       try {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/FSDataset.java

@@ -61,7 +61,10 @@ import org.apache.hadoop.hdfs.protocol.HdfsConstants;
 import org.apache.hadoop.hdfs.protocol.RecoveryInProgressException;
 import org.apache.hadoop.hdfs.server.common.GenerationStamp;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+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;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.hdfs.server.datanode.metrics.FSDatasetMBean;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
@@ -548,7 +551,7 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
    * 
    * It uses the {@link FSDataset} object for synchronization.
    */
-  static class FSVolume implements FSVolumeInterface {
+  static class FSVolume implements FsVolumeSpi {
     private final FSDataset dataset;
     private final Map<String, BlockPoolSlice> map = new HashMap<String, BlockPoolSlice>();
     private final File currentDir;    // <StorageDirectory>/current
@@ -865,7 +868,7 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
       
     private long getRemaining() throws IOException {
       long remaining = 0L;
-      for (FSVolumeInterface vol : volumes) {
+      for (FsVolumeSpi vol : volumes) {
         remaining += vol.getAvailable();
       }
       return remaining;
@@ -1052,13 +1055,13 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
   }
 
   @Override // FSDatasetInterface
-  public MetaDataInputStream getMetaDataInputStream(ExtendedBlock b)
+  public LengthInputStream getMetaDataInputStream(ExtendedBlock b)
       throws IOException {
     final File meta = getMetaFile(b);
     if (meta == null || !meta.exists()) {
       return null;
     }
-    return new MetaDataInputStream(new FileInputStream(meta), meta.length());
+    return new LengthInputStream(new FileInputStream(meta), meta.length());
   }
     
   private final DataNode datanode;
@@ -1287,7 +1290,7 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
    * Returns handles to the block file and its metadata file
    */
   @Override // FSDatasetInterface
-  public synchronized BlockInputStreams getTmpInputStreams(ExtendedBlock b, 
+  public synchronized ReplicaInputStreams getTmpInputStreams(ExtendedBlock b, 
                           long blkOffset, long ckoff) throws IOException {
     ReplicaInfo info = getReplicaInfo(b);
     File blockFile = info.getBlockFile();
@@ -1300,7 +1303,7 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
     if (ckoff > 0) {
       metaInFile.seek(ckoff);
     }
-    return new BlockInputStreams(new FileInputStream(blockInFile.getFD()),
+    return new ReplicaInputStreams(new FileInputStream(blockInFile.getFD()),
                                 new FileInputStream(metaInFile.getFD()));
   }
     
@@ -1742,9 +1745,9 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
    * last checksum will be overwritten.
    */
   @Override // FSDatasetInterface
-  public void adjustCrcChannelPosition(ExtendedBlock b, BlockWriteStreams streams, 
+  public void adjustCrcChannelPosition(ExtendedBlock b, ReplicaOutputStreams streams, 
       int checksumSize) throws IOException {
-    FileOutputStream file = (FileOutputStream) streams.checksumOut;
+    FileOutputStream file = (FileOutputStream) streams.getChecksumOut();
     FileChannel channel = file.getChannel();
     long oldPos = channel.position();
     long newPos = oldPos - checksumSize;
@@ -2195,7 +2198,7 @@ class FSDataset implements FSDatasetInterface<FSDataset.FSVolume> {
    */
   @Override
   public void checkAndUpdate(String bpid, long blockId, File diskFile,
-      File diskMetaFile, FSVolumeInterface vol) {
+      File diskMetaFile, FsVolumeSpi vol) {
     Block corruptBlock = null;
     ReplicaInfo memBlockInfo;
     synchronized (this) {

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/FSDatasetInterface.java

@@ -18,12 +18,9 @@
 package org.apache.hadoop.hdfs.server.datanode;
 
 
-import java.io.Closeable;
 import java.io.File;
-import java.io.FilterInputStream;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.OutputStream;
 import java.util.List;
 import java.util.Map;
 
@@ -34,11 +31,13 @@ import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
 import org.apache.hadoop.hdfs.protocol.BlockLocalPathInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+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;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.hdfs.server.datanode.metrics.FSDatasetMBean;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
-import org.apache.hadoop.io.IOUtils;
-import org.apache.hadoop.util.DataChecksum;
 import org.apache.hadoop.util.DiskChecker.DiskErrorException;
 import org.apache.hadoop.util.ReflectionUtils;
 
@@ -50,7 +49,7 @@ import org.apache.hadoop.util.ReflectionUtils;
  *
  */
 @InterfaceAudience.Private
-public interface FSDatasetInterface<V extends FSDatasetInterface.FSVolumeInterface>
+public interface FSDatasetInterface<V extends FsVolumeSpi>
     extends FSDatasetMBean {
   /**
    * A factory for creating FSDatasetInterface objects.
@@ -77,24 +76,6 @@ public interface FSDatasetInterface<V extends FSDatasetInterface.FSVolumeInterfa
     }
   }
 
-  /**
-   * This is an interface for the underlying volume.
-   * @see org.apache.hadoop.hdfs.server.datanode.FSDataset.FSVolume
-   */
-  interface FSVolumeInterface {
-    /** @return a list of block pools. */
-    public String[] getBlockPoolList();
-
-    /** @return the available storage space in bytes. */
-    public long getAvailable() throws IOException;
-
-    /** @return the path to the volume */
-    public String getPath(String bpid) throws IOException;
-
-    /** @return the directory for the finalized blocks in the block pool. */
-    public File getFinalizedDir(String bpid) throws IOException;
-  }
-
   /**
    * Create rolling logs.
    * 
@@ -121,32 +102,15 @@ public interface FSDatasetInterface<V extends FSDatasetInterface.FSVolumeInterfa
    * as corrupted.
    */
   public void checkAndUpdate(String bpid, long blockId, File diskFile,
-      File diskMetaFile, FSVolumeInterface vol);
+      File diskMetaFile, FsVolumeSpi vol);
 
-  /**
-   * This class provides the input stream and length of the metadata
-   * of a block
-   *
-   */
-  static class MetaDataInputStream extends FilterInputStream {
-    MetaDataInputStream(InputStream stream, long len) {
-      super(stream);
-      length = len;
-    }
-    private long length;
-    
-    public long getLength() {
-      return length;
-    }
-  }
-  
   /**
    * @param b - the block
    * @return a stream if the meta-data of the block exists;
    *         otherwise, return null.
    * @throws IOException
    */
-  public MetaDataInputStream getMetaDataInputStream(ExtendedBlock b
+  public LengthInputStream getMetaDataInputStream(ExtendedBlock b
       ) throws IOException;
 
   /**
@@ -197,58 +161,10 @@ public interface FSDatasetInterface<V extends FSDatasetInterface.FSVolumeInterfa
    *  starting at the offset
    * @throws IOException
    */
-  public BlockInputStreams getTmpInputStreams(ExtendedBlock b, long blkoff,
+  public ReplicaInputStreams getTmpInputStreams(ExtendedBlock b, long blkoff,
       long ckoff) throws IOException;
 
      /**
-      * 
-      * This class contains the output streams for the data and checksum
-      * of a block
-      *
-      */
-     static class BlockWriteStreams {
-      OutputStream dataOut;
-      OutputStream checksumOut;
-      DataChecksum checksum;
-      
-      BlockWriteStreams(OutputStream dOut, OutputStream cOut,
-          DataChecksum checksum) {
-        dataOut = dOut;
-        checksumOut = cOut;
-        this.checksum = checksum;
-      }
-      
-      void close() {
-        IOUtils.closeStream(dataOut);
-        IOUtils.closeStream(checksumOut);
-      }
-      
-      DataChecksum getChecksum() {
-        return checksum;
-      }
-    }
-
-  /**
-   * This class contains the input streams for the data and checksum
-   * of a block
-   */
-  static class BlockInputStreams implements Closeable {
-    final InputStream dataIn;
-    final InputStream checksumIn;
-
-    BlockInputStreams(InputStream dataIn, InputStream checksumIn) {
-      this.dataIn = dataIn;
-      this.checksumIn = checksumIn;
-    }
-
-    @Override
-    public void close() {
-      IOUtils.closeStream(dataIn);
-      IOUtils.closeStream(checksumIn);
-    }
-  }
-    
-  /**
    * Creates a temporary replica and returns the meta information of the replica
    * 
    * @param b block
@@ -395,7 +311,7 @@ public interface FSDatasetInterface<V extends FSDatasetInterface.FSVolumeInterfa
    * @param checksumSize number of bytes each checksum has
    * @throws IOException
    */
-  public void adjustCrcChannelPosition(ExtendedBlock b, BlockWriteStreams stream, 
+  public void adjustCrcChannelPosition(ExtendedBlock b, ReplicaOutputStreams stream, 
       int checksumSize) throws IOException;
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/FinalizedReplica.java

@@ -21,7 +21,7 @@ import java.io.File;
 
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 
 /**
  * This class describes a replica that has been finalized.
@@ -38,7 +38,7 @@ class FinalizedReplica extends ReplicaInfo {
    * @param dir directory path where block and meta files are located
    */
   FinalizedReplica(long blockId, long len, long genStamp,
-      FSVolumeInterface vol, File dir) {
+      FsVolumeSpi vol, File dir) {
     super(blockId, len, genStamp, vol, dir);
   }
   
@@ -48,7 +48,7 @@ class FinalizedReplica extends ReplicaInfo {
    * @param vol volume where replica is located
    * @param dir directory path where block and meta files are located
    */
-  FinalizedReplica(Block block, FSVolumeInterface vol, File dir) {
+  FinalizedReplica(Block block, FsVolumeSpi vol, File dir) {
     super(block, vol, dir);
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaBeingWritten.java

@@ -21,7 +21,7 @@ import java.io.File;
 
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 
 /** This class represents replicas being written. 
  * Those are the replicas that
@@ -36,7 +36,7 @@ class ReplicaBeingWritten extends ReplicaInPipeline {
    * @param dir directory path where block and meta files are located
    */
   ReplicaBeingWritten(long blockId, long genStamp, 
-        FSVolumeInterface vol, File dir) {
+        FsVolumeSpi vol, File dir) {
     super( blockId, genStamp, vol, dir);
   }
   
@@ -48,7 +48,7 @@ class ReplicaBeingWritten extends ReplicaInPipeline {
    * @param writer a thread that is writing to this replica
    */
   ReplicaBeingWritten(Block block, 
-      FSVolumeInterface vol, File dir, Thread writer) {
+      FsVolumeSpi vol, File dir, Thread writer) {
     super( block, vol, dir, writer);
   }
 
@@ -62,7 +62,7 @@ class ReplicaBeingWritten extends ReplicaInPipeline {
    * @param writer a thread that is writing to this replica
    */
   ReplicaBeingWritten(long blockId, long len, long genStamp,
-      FSVolumeInterface vol, File dir, Thread writer ) {
+      FsVolumeSpi vol, File dir, Thread writer ) {
     super( blockId, len, genStamp, vol, dir, writer);
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipeline.java

@@ -24,8 +24,8 @@ import java.io.RandomAccessFile;
 
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.BlockWriteStreams;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.util.DataChecksum;
 
@@ -53,7 +53,7 @@ class ReplicaInPipeline extends ReplicaInfo
    * @param state replica state
    */
     ReplicaInPipeline(long blockId, long genStamp, 
-        FSVolumeInterface vol, File dir) {
+        FsVolumeSpi vol, File dir) {
     this( blockId, 0L, genStamp, vol, dir, Thread.currentThread());
   }
 
@@ -65,7 +65,7 @@ class ReplicaInPipeline extends ReplicaInfo
    * @param writer a thread that is writing to this replica
    */
   ReplicaInPipeline(Block block, 
-      FSVolumeInterface vol, File dir, Thread writer) {
+      FsVolumeSpi vol, File dir, Thread writer) {
     this( block.getBlockId(), block.getNumBytes(), block.getGenerationStamp(),
         vol, dir, writer);
   }
@@ -80,7 +80,7 @@ class ReplicaInPipeline extends ReplicaInfo
    * @param writer a thread that is writing to this replica
    */
   ReplicaInPipeline(long blockId, long len, long genStamp,
-      FSVolumeInterface vol, File dir, Thread writer ) {
+      FsVolumeSpi vol, File dir, Thread writer ) {
     super( blockId, len, genStamp, vol, dir);
     this.bytesAcked = len;
     this.bytesOnDisk = len;
@@ -168,7 +168,7 @@ class ReplicaInPipeline extends ReplicaInfo
   }
   
   @Override // ReplicaInPipelineInterface
-  public BlockWriteStreams createStreams(boolean isCreate, 
+  public ReplicaOutputStreams createStreams(boolean isCreate, 
       DataChecksum requestedChecksum) throws IOException {
     File blockFile = getBlockFile();
     File metaFile = getMetaFile();
@@ -234,7 +234,7 @@ class ReplicaInPipeline extends ReplicaInfo
         blockOut.getChannel().position(blockDiskSize);
         crcOut.getChannel().position(crcDiskSize);
       }
-      return new BlockWriteStreams(blockOut, crcOut, checksum);
+      return new ReplicaOutputStreams(blockOut, crcOut, checksum);
     } catch (IOException e) {
       IOUtils.closeStream(blockOut);
       IOUtils.closeStream(metaRAF);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInPipelineInterface.java

@@ -19,7 +19,7 @@ package org.apache.hadoop.hdfs.server.datanode;
 
 import java.io.IOException;
 
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.BlockWriteStreams;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.util.DataChecksum;
 
 /** 
@@ -66,6 +66,6 @@ interface ReplicaInPipelineInterface extends Replica {
    * @return output streams for writing
    * @throws IOException if any error occurs
    */
-  public BlockWriteStreams createStreams(boolean isCreate,
+  public ReplicaOutputStreams createStreams(boolean isCreate,
       DataChecksum requestedChecksum) throws IOException;
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaInfo.java

@@ -26,7 +26,7 @@ import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.FileUtil;
 import org.apache.hadoop.fs.HardLink;
 import org.apache.hadoop.hdfs.protocol.Block;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.io.IOUtils;
 
 /**
@@ -36,7 +36,7 @@ import org.apache.hadoop.io.IOUtils;
 @InterfaceAudience.Private
 abstract public class ReplicaInfo extends Block implements Replica {
   /** volume where the replica belongs */
-  private FSVolumeInterface volume;
+  private FsVolumeSpi volume;
   /** directory where block & meta files belong */
   private File dir;
 
@@ -47,7 +47,7 @@ abstract public class ReplicaInfo extends Block implements Replica {
    * @param vol volume where replica is located
    * @param dir directory path where block and meta files are located
    */
-  ReplicaInfo(long blockId, long genStamp, FSVolumeInterface vol, File dir) {
+  ReplicaInfo(long blockId, long genStamp, FsVolumeSpi vol, File dir) {
     this( blockId, 0L, genStamp, vol, dir);
   }
   
@@ -57,7 +57,7 @@ abstract public class ReplicaInfo extends Block implements Replica {
    * @param vol volume where replica is located
    * @param dir directory path where block and meta files are located
    */
-  ReplicaInfo(Block block, FSVolumeInterface vol, File dir) {
+  ReplicaInfo(Block block, FsVolumeSpi vol, File dir) {
     this(block.getBlockId(), block.getNumBytes(), 
         block.getGenerationStamp(), vol, dir);
   }
@@ -71,7 +71,7 @@ abstract public class ReplicaInfo extends Block implements Replica {
    * @param dir directory path where block and meta files are located
    */
   ReplicaInfo(long blockId, long len, long genStamp,
-      FSVolumeInterface vol, File dir) {
+      FsVolumeSpi vol, File dir) {
     super(blockId, len, genStamp);
     this.volume = vol;
     this.dir = dir;
@@ -113,14 +113,14 @@ abstract public class ReplicaInfo extends Block implements Replica {
    * Get the volume where this replica is located on disk
    * @return the volume where this replica is located on disk
    */
-  FSVolumeInterface getVolume() {
+  FsVolumeSpi getVolume() {
     return volume;
   }
   
   /**
    * Set the volume where this replica is located on disk
    */
-  void setVolume(FSVolumeInterface vol) {
+  void setVolume(FsVolumeSpi vol) {
     this.volume = vol;
   }
   

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaUnderRecovery.java

@@ -20,7 +20,7 @@ package org.apache.hadoop.hdfs.server.datanode;
 import java.io.File;
 
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
 
 /**
@@ -145,7 +145,7 @@ class ReplicaUnderRecovery extends ReplicaInfo {
   }
   
   @Override //ReplicaInfo
-  void setVolume(FSVolumeInterface vol) {
+  void setVolume(FsVolumeSpi vol) {
     super.setVolume(vol);
     original.setVolume(vol);
   }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/ReplicaWaitingToBeRecovered.java

@@ -21,7 +21,7 @@ import java.io.File;
 
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 
 /**
  * This class represents a replica that is waiting to be recovered.
@@ -44,7 +44,7 @@ class ReplicaWaitingToBeRecovered extends ReplicaInfo {
    * @param dir directory path where block and meta files are located
    */
   ReplicaWaitingToBeRecovered(long blockId, long len, long genStamp,
-      FSVolumeInterface vol, File dir) {
+      FsVolumeSpi vol, File dir) {
     super(blockId, len, genStamp, vol, dir);
   }
   
@@ -54,7 +54,7 @@ class ReplicaWaitingToBeRecovered extends ReplicaInfo {
    * @param vol volume where replica is located
    * @param dir directory path where block and meta files are located
    */
-  ReplicaWaitingToBeRecovered(Block block, FSVolumeInterface vol, File dir) {
+  ReplicaWaitingToBeRecovered(Block block, FsVolumeSpi vol, File dir) {
     super(block, vol, dir);
   }
   

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/RoundRobinVolumesPolicy.java

@@ -20,10 +20,10 @@ package org.apache.hadoop.hdfs.server.datanode;
 import java.io.IOException;
 import java.util.List;
 
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.util.DiskChecker.DiskOutOfSpaceException;
 
-public class RoundRobinVolumesPolicy<V extends FSVolumeInterface>
+public class RoundRobinVolumesPolicy<V extends FsVolumeSpi>
     implements BlockVolumeChoosingPolicy<V> {
 
   private int curVolume = 0;

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/FsVolumeSpi.java

@@ -0,0 +1,38 @@
+/**
+ * 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.File;
+import java.io.IOException;
+
+/**
+ * This is an interface for the underlying volume.
+ */
+public interface FsVolumeSpi {
+  /** @return a list of block pools. */
+  public String[] getBlockPoolList();
+
+  /** @return the available storage space in bytes. */
+  public long getAvailable() throws IOException;
+
+  /** @return the path to the volume */
+  public String getPath(String bpid) throws IOException;
+
+  /** @return the directory for the finalized blocks in the block pool. */
+  public File getFinalizedDir(String bpid) throws IOException;
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/LengthInputStream.java

@@ -0,0 +1,44 @@
+/**
+ * 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.FilterInputStream;
+import java.io.InputStream;
+
+/**
+ * An input stream with length.
+ */
+public class LengthInputStream extends FilterInputStream {
+
+  private final long length;
+
+  /**
+   * Create an stream.
+   * @param in the underlying input stream.
+   * @param length the length of the stream.
+   */
+  public LengthInputStream(InputStream in, long length) {
+    super(in);
+    this.length = length;
+  }
+
+  /** @return the length. */
+  public long getLength() {
+    return length;
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaInputStreams.java

@@ -0,0 +1,53 @@
+/**
+ * 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.InputStream;
+
+import org.apache.hadoop.io.IOUtils;
+
+/**
+ * Contains the input streams for the data and checksum of a replica.
+ */
+public class ReplicaInputStreams implements Closeable {
+  private final InputStream dataIn;
+  private final InputStream checksumIn;
+
+  /** Create an object with a data input stream and a checksum input stream. */
+  public ReplicaInputStreams(InputStream dataIn, InputStream checksumIn) {
+    this.dataIn = dataIn;
+    this.checksumIn = checksumIn;
+  }
+
+  /** @return the data input stream. */
+  public InputStream getDataIn() {
+    return dataIn;
+  }
+
+  /** @return the checksum input stream. */
+  public InputStream getChecksumIn() {
+    return checksumIn;
+  }
+
+  @Override
+  public void close() {
+    IOUtils.closeStream(dataIn);
+    IOUtils.closeStream(checksumIn);
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/ReplicaOutputStreams.java

@@ -0,0 +1,65 @@
+/**
+ * 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.OutputStream;
+
+import org.apache.hadoop.io.IOUtils;
+import org.apache.hadoop.util.DataChecksum;
+
+/**
+ * Contains the output streams for the data and checksum of a replica.
+ */
+public class ReplicaOutputStreams implements Closeable {
+  private final OutputStream dataOut;
+  private final OutputStream checksumOut;
+  private final DataChecksum checksum;
+
+  /**
+   * Create an object with a data output stream, a checksum output stream
+   * and a checksum.
+   */
+  public ReplicaOutputStreams(OutputStream dataOut, OutputStream checksumOut,
+      DataChecksum checksum) {
+    this.dataOut = dataOut;
+    this.checksumOut = checksumOut;
+    this.checksum = checksum;
+  }
+
+  /** @return the data output stream. */
+  public OutputStream getDataOut() {
+    return dataOut;
+  }
+
+  /** @return the checksum output stream. */
+  public OutputStream getChecksumOut() {
+    return checksumOut;
+  }
+
+  /** @return the checksum. */
+  public DataChecksum getChecksum() {
+    return checksum;
+  }
+
+  @Override
+  public void close() {
+    IOUtils.closeStream(dataOut);
+    IOUtils.closeStream(checksumOut);
+  }
+}

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java

@@ -39,6 +39,10 @@ import org.apache.hadoop.hdfs.protocol.BlockLocalPathInfo;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
 import org.apache.hadoop.hdfs.server.datanode.FSDataset.FSVolumeSet;
+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;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.hdfs.server.datanode.metrics.FSDatasetMBean;
 import org.apache.hadoop.hdfs.server.protocol.BlockRecoveryCommand.RecoveringBlock;
 import org.apache.hadoop.hdfs.server.protocol.ReplicaRecoveryInfo;
@@ -61,8 +65,7 @@ import org.apache.hadoop.util.DiskChecker.DiskErrorException;
  * 
  * Note the synchronization is coarse grained - it is at each method. 
  */
-public class SimulatedFSDataset
+public class SimulatedFSDataset implements FSDatasetInterface<FsVolumeSpi> {
-    implements FSDatasetInterface<FSDatasetInterface.FSVolumeInterface> {
   static class Factory extends FSDatasetInterface.Factory<SimulatedFSDataset> {
     @Override
     public SimulatedFSDataset createFSDatasetInterface(DataNode datanode,
@@ -215,14 +218,14 @@ public class SimulatedFSDataset
     }
 
     @Override
-    synchronized public BlockWriteStreams createStreams(boolean isCreate, 
+    synchronized public ReplicaOutputStreams createStreams(boolean isCreate, 
         DataChecksum requestedChecksum) throws IOException {
       if (finalized) {
         throw new IOException("Trying to write to a finalized replica "
             + theBlock);
       } else {
         SimulatedOutputStream crcStream = new SimulatedOutputStream();
-        return new BlockWriteStreams(oStream, crcStream, requestedChecksum);
+        return new ReplicaOutputStreams(oStream, crcStream, requestedChecksum);
       }
     }
 
@@ -688,13 +691,13 @@ public class SimulatedFSDataset
 
   /** Not supported */
   @Override // FSDatasetInterface
-  public BlockInputStreams getTmpInputStreams(ExtendedBlock b, long blkoff,
+  public ReplicaInputStreams getTmpInputStreams(ExtendedBlock b, long blkoff,
       long ckoff) throws IOException {
     throw new IOException("Not supported");
   }
 
   @Override // FSDatasetInterface
-  public synchronized MetaDataInputStream getMetaDataInputStream(ExtendedBlock b
+  public synchronized LengthInputStream getMetaDataInputStream(ExtendedBlock b
       ) throws IOException {
     final Map<Block, BInfo> map = getMap(b.getBlockPoolId());
     BInfo binfo = map.get(b.getLocalBlock());
@@ -706,7 +709,7 @@ public class SimulatedFSDataset
           " is being written, its meta cannot be read");
     }
     final SimulatedInputStream sin = binfo.getMetaIStream();
-    return new MetaDataInputStream(sin, sin.getLength());
+    return new LengthInputStream(sin, sin.getLength());
   }
 
   @Override
@@ -716,7 +719,7 @@ public class SimulatedFSDataset
 
   @Override // FSDatasetInterface
   public synchronized void adjustCrcChannelPosition(ExtendedBlock b,
-                                              BlockWriteStreams stream, 
+                                              ReplicaOutputStreams stream, 
                                               int checksumSize)
                                               throws IOException {
   }
@@ -959,12 +962,12 @@ public class SimulatedFSDataset
 
   @Override
   public void checkAndUpdate(String bpid, long blockId, File diskFile,
-      File diskMetaFile, FSVolumeInterface vol) {
+      File diskMetaFile, FsVolumeSpi vol) {
     throw new UnsupportedOperationException();
   }
 
   @Override
-  public List<FSVolumeInterface> getVolumes() {
+  public List<FsVolumeSpi> getVolumes() {
     throw new UnsupportedOperationException();
   }
 

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestBlockRecovery.java

@@ -36,7 +36,7 @@ import org.apache.hadoop.hdfs.protocolPB.DatanodeProtocolClientSideTranslatorPB;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
 import org.apache.hadoop.hdfs.server.datanode.DataNode;
 import org.apache.hadoop.hdfs.server.datanode.DataNode.BlockRecord;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.BlockWriteStreams;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeCommand;
 import org.apache.hadoop.hdfs.server.protocol.DatanodeProtocol;
@@ -535,11 +535,11 @@ public class TestBlockRecovery {
       LOG.debug("Running " + GenericTestUtils.getMethodName());
     }
     ReplicaInPipelineInterface replicaInfo = dn.data.createRbw(block);
-    BlockWriteStreams streams = null;
+    ReplicaOutputStreams streams = null;
     try {
       streams = replicaInfo.createStreams(true,
           DataChecksum.newDataChecksum(DataChecksum.CHECKSUM_CRC32, 512));
-      streams.checksumOut.write('a');
+      streams.getChecksumOut().write('a');
       dn.data.initReplicaRecovery(new RecoveringBlock(block, null, RECOVERY_ID+1));
       try {
         dn.syncBlock(rBlock, initBlockRecords(dn));

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestDatanodeRestart.java

@@ -37,7 +37,7 @@ import org.apache.hadoop.hdfs.MiniDFSCluster;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants.ReplicaState;
 import org.apache.hadoop.hdfs.server.datanode.FSDataset.FSVolume;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.io.IOUtils;
 import org.junit.Assert;
 import org.junit.Test;
@@ -98,7 +98,7 @@ public class TestDatanodeRestart {
       out.write(writeBuf);
       out.hflush();
       DataNode dn = cluster.getDataNodes().get(0);
-      for (FSVolumeInterface v : dn.data.getVolumes()) {
+      for (FsVolumeSpi v : dn.data.getVolumes()) {
         FSVolume volume = (FSVolume)v;
         File currentDir = volume.getCurrentDir().getParentFile().getParentFile();
         File rbwDir = new File(currentDir, "rbw");

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestRoundRobinVolumesPolicy.java

@@ -21,7 +21,7 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
 
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.FSVolumeInterface;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.FsVolumeSpi;
 import org.apache.hadoop.util.DiskChecker.DiskOutOfSpaceException;
 import org.apache.hadoop.util.ReflectionUtils;
 import org.junit.Assert;
@@ -33,19 +33,19 @@ public class TestRoundRobinVolumesPolicy {
   // Test the Round-Robin block-volume choosing algorithm.
   @Test
   public void testRR() throws Exception {
-    final List<FSVolumeInterface> volumes = new ArrayList<FSVolumeInterface>();
+    final List<FsVolumeSpi> volumes = new ArrayList<FsVolumeSpi>();
 
     // First volume, with 100 bytes of space.
-    volumes.add(Mockito.mock(FSVolumeInterface.class));
+    volumes.add(Mockito.mock(FsVolumeSpi.class));
     Mockito.when(volumes.get(0).getAvailable()).thenReturn(100L);
 
     // Second volume, with 200 bytes of space.
-    volumes.add(Mockito.mock(FSVolumeInterface.class));
+    volumes.add(Mockito.mock(FsVolumeSpi.class));
     Mockito.when(volumes.get(1).getAvailable()).thenReturn(200L);
 
     @SuppressWarnings("unchecked")
-    final RoundRobinVolumesPolicy<FSVolumeInterface> policy = 
+    final RoundRobinVolumesPolicy<FsVolumeSpi> policy = 
-        (RoundRobinVolumesPolicy<FSVolumeInterface>)ReflectionUtils.newInstance(
+        (RoundRobinVolumesPolicy<FsVolumeSpi>)ReflectionUtils.newInstance(
             RoundRobinVolumesPolicy.class, null);
     
     // Test two rounds of round-robin choosing
@@ -71,18 +71,18 @@ public class TestRoundRobinVolumesPolicy {
   @Test
   public void testRRPolicyExceptionMessage()
       throws Exception {
-    final List<FSVolumeInterface> volumes = new ArrayList<FSVolumeInterface>();
+    final List<FsVolumeSpi> volumes = new ArrayList<FsVolumeSpi>();
 
     // First volume, with 500 bytes of space.
-    volumes.add(Mockito.mock(FSVolumeInterface.class));
+    volumes.add(Mockito.mock(FsVolumeSpi.class));
     Mockito.when(volumes.get(0).getAvailable()).thenReturn(500L);
 
     // Second volume, with 600 bytes of space.
-    volumes.add(Mockito.mock(FSVolumeInterface.class));
+    volumes.add(Mockito.mock(FsVolumeSpi.class));
     Mockito.when(volumes.get(1).getAvailable()).thenReturn(600L);
 
-    final RoundRobinVolumesPolicy<FSVolumeInterface> policy
+    final RoundRobinVolumesPolicy<FsVolumeSpi> policy
-        = new RoundRobinVolumesPolicy<FSVolumeInterface>();
+        = new RoundRobinVolumesPolicy<FsVolumeSpi>();
     int blockSize = 700;
     try {
       policy.chooseVolume(volumes, blockSize);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestSimulatedFSDataset.java

@@ -29,7 +29,7 @@ import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.BlockListAsLongs;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
-import org.apache.hadoop.hdfs.server.datanode.FSDatasetInterface.BlockWriteStreams;
+import org.apache.hadoop.hdfs.server.datanode.fsdataset.ReplicaOutputStreams;
 import org.apache.hadoop.util.DataChecksum;
 
 /**
@@ -63,10 +63,10 @@ public class TestSimulatedFSDataset extends TestCase {
       // we pass expected len as zero, - fsdataset should use the sizeof actual
       // data written
       ReplicaInPipelineInterface bInfo = fsdataset.createRbw(b);
-      BlockWriteStreams out = bInfo.createStreams(true,
+      ReplicaOutputStreams out = bInfo.createStreams(true,
           DataChecksum.newDataChecksum(DataChecksum.CHECKSUM_CRC32, 512));
       try {
-        OutputStream dataOut  = out.dataOut;
+        OutputStream dataOut  = out.getDataOut();
         assertEquals(0, fsdataset.getLength(b));
         for (int j=1; j <= blockIdToLen(i); ++j) {
           dataOut.write(j);