HDFS-5634. Allow BlockReaderLocal to switch between checksumming and not (cmccabe)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1552119 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -230,6 +230,9 @@ Release 2.4.0 - UNRELEASED
     HDFS-5580. Fix infinite loop in Balancer.waitForMoveCompletion.
     (Binglin Chang via junping_du)
 
+    HDFS-5634. Allow BlockReaderLocal to switch between checksumming and not
+    (cmccabe)
+
 Release 2.3.0 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/BlockReader.java

@@ -18,8 +18,10 @@
 package org.apache.hadoop.hdfs;
 
 import java.io.IOException;
+import java.util.EnumSet;
 
 import org.apache.hadoop.fs.ByteBufferReadable;
+import org.apache.hadoop.fs.ReadOption;
 import org.apache.hadoop.hdfs.client.ClientMmap;
 import org.apache.hadoop.hdfs.client.ClientMmapManager;
 import org.apache.hadoop.hdfs.protocol.LocatedBlock;
@@ -89,10 +91,10 @@ public interface BlockReader extends ByteBufferReadable {
   /**
    * Get a ClientMmap object for this BlockReader.
    *
-   * @param curBlock      The current block.
+   * @param opts          The read options to use.
    * @return              The ClientMmap object, or null if mmap is not
    *                      supported.
    */
-  ClientMmap getClientMmap(LocatedBlock curBlock,
+  ClientMmap getClientMmap(EnumSet<ReadOption> opts,
         ClientMmapManager mmapManager);
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/BlockReaderFactory.java

@@ -35,6 +35,7 @@ import org.apache.hadoop.hdfs.protocolPB.PBHelper;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
 import org.apache.hadoop.hdfs.server.common.HdfsServerConstants;
+import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader;
 import org.apache.hadoop.hdfs.server.datanode.CachingStrategy;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.ipc.RemoteException;
@@ -98,7 +99,7 @@ public class BlockReaderFactory {
         // enabled, try to set up a BlockReaderLocal.
         BlockReader reader = newShortCircuitBlockReader(conf, file,
             block, blockToken, startOffset, len, peer, datanodeID,
-            domSockFactory, verifyChecksum, fisCache);
+            domSockFactory, verifyChecksum, fisCache, cachingStrategy);
         if (reader != null) {
           // One we've constructed the short-circuit block reader, we don't
           // need the socket any more.  So let's return it to the cache.
@@ -160,7 +161,8 @@ public class BlockReaderFactory {
    * @param verifyChecksum     True if we should verify the checksums.
    *                           Note: even if this is true, when
    *                           DFS_CLIENT_READ_CHECKSUM_SKIP_CHECKSUM_KEY is
-   *                           set, we will skip checksums.
+   *                           set or the block is mlocked, we will skip
+   *                           checksums.
    *
    * @return                   The BlockReaderLocal, or null if the
    *                           DataNode declined to provide short-circuit
@@ -172,7 +174,8 @@ public class BlockReaderFactory {
       Token<BlockTokenIdentifier> blockToken, long startOffset,
       long len, Peer peer, DatanodeID datanodeID,
       DomainSocketFactory domSockFactory, boolean verifyChecksum,
-      FileInputStreamCache fisCache) throws IOException {
+      FileInputStreamCache fisCache,
+      CachingStrategy cachingStrategy) throws IOException {
     final DataOutputStream out =
         new DataOutputStream(new BufferedOutputStream(
           peer.getOutputStream()));
@@ -189,9 +192,18 @@ public class BlockReaderFactory {
       FileInputStream fis[] = new FileInputStream[2];
       sock.recvFileInputStreams(fis, buf, 0, buf.length);
       try {
-        reader = new BlockReaderLocal(conf, file, block,
+        reader = new BlockReaderLocal.Builder(conf).
-            startOffset, len, fis[0], fis[1], datanodeID, verifyChecksum,
+            setFilename(file).
-            fisCache);
+            setBlock(block).
+            setStartOffset(startOffset).
+            setStreams(fis).
+            setDatanodeID(datanodeID).
+            setVerifyChecksum(verifyChecksum).
+            setBlockMetadataHeader(
+                BlockMetadataHeader.preadHeader(fis[1].getChannel())).
+            setFileInputStreamCache(fisCache).
+            setCachingStrategy(cachingStrategy).
+            build();
       } finally {
         if (reader == null) {
           IOUtils.cleanup(DFSClient.LOG, fis[0], fis[1]);

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/BlockReaderLocalLegacy.java

@@ -24,10 +24,12 @@ import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.security.PrivilegedExceptionAction;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
+import org.apache.hadoop.fs.ReadOption;
 import org.apache.hadoop.hdfs.client.ClientMmap;
 import org.apache.hadoop.hdfs.client.ClientMmapManager;
 import org.apache.commons.logging.Log;
@@ -706,8 +708,8 @@ class BlockReaderLocalLegacy implements BlockReader {
   }
 
   @Override
-  public ClientMmap getClientMmap(LocatedBlock curBlock,
+  public ClientMmap getClientMmap(EnumSet<ReadOption> opts,
-      ClientMmapManager mmapManager) {
+        ClientMmapManager mmapManager) {
     return null;
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSInputStream.java

@@ -57,6 +57,7 @@ import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.protocol.datatransfer.InvalidEncryptionKeyException;
 import org.apache.hadoop.hdfs.security.token.block.BlockTokenIdentifier;
 import org.apache.hadoop.hdfs.security.token.block.InvalidBlockTokenException;
+import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader;
 import org.apache.hadoop.hdfs.server.datanode.CachingStrategy;
 import org.apache.hadoop.hdfs.server.datanode.ReplicaNotFoundException;
 import org.apache.hadoop.io.ByteBufferPool;
@@ -1073,9 +1074,18 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
         DFSClient.LOG.debug("got FileInputStreams for " + block + " from " +
             "the FileInputStreamCache.");
       }
-      return new BlockReaderLocal(dfsClient.getConf(), file,
+      return new BlockReaderLocal.Builder(dfsClient.getConf()).
-        block, startOffset, len, fis[0], fis[1], chosenNode, verifyChecksum,
+          setFilename(file).
-        fileInputStreamCache);
+          setBlock(block).
+          setStartOffset(startOffset).
+          setStreams(fis).
+          setDatanodeID(chosenNode).
+          setVerifyChecksum(verifyChecksum).
+          setBlockMetadataHeader(BlockMetadataHeader.
+              preadHeader(fis[1].getChannel())).
+          setFileInputStreamCache(fileInputStreamCache).
+          setCachingStrategy(cachingStrategy).
+          build();
     }
     
     // If the legacy local block reader is enabled and we are reading a local
@@ -1479,23 +1489,19 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
             "at position " + pos);
       }
     }
-    boolean canSkipChecksums = opts.contains(ReadOption.SKIP_CHECKSUMS);
+    ByteBuffer buffer = tryReadZeroCopy(maxLength, opts);
-    if (canSkipChecksums) {
+    if (buffer != null) {
-      ByteBuffer buffer = tryReadZeroCopy(maxLength);
+      return buffer;
-      if (buffer != null) {
-        return buffer;
-      }
     }
-    ByteBuffer buffer = ByteBufferUtil.
+    buffer = ByteBufferUtil.fallbackRead(this, bufferPool, maxLength);
-        fallbackRead(this, bufferPool, maxLength);
     if (buffer != null) {
       extendedReadBuffers.put(buffer, bufferPool);
     }
     return buffer;
   }
 
-  private synchronized ByteBuffer tryReadZeroCopy(int maxLength)
+  private synchronized ByteBuffer tryReadZeroCopy(int maxLength,
-      throws IOException {
+      EnumSet<ReadOption> opts) throws IOException {
     // Java ByteBuffers can't be longer than 2 GB, because they use
     // 4-byte signed integers to represent capacity, etc.
     // So we can't mmap the parts of the block higher than the 2 GB offset.
@@ -1518,8 +1524,7 @@ implements ByteBufferReadable, CanSetDropBehind, CanSetReadahead,
     long blockPos = curPos - blockStartInFile;
     long limit = blockPos + length;
     ClientMmap clientMmap =
-        blockReader.getClientMmap(currentLocatedBlock,
+        blockReader.getClientMmap(opts, dfsClient.getMmapManager());
-            dfsClient.getMmapManager());
     if (clientMmap == null) {
       if (DFSClient.LOG.isDebugEnabled()) {
         DFSClient.LOG.debug("unable to perform a zero-copy read from offset " +

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader.java

@@ -23,10 +23,12 @@ import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
+import java.util.EnumSet;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.fs.FSInputChecker;
 import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.ReadOption;
 import org.apache.hadoop.hdfs.client.ClientMmap;
 import org.apache.hadoop.hdfs.client.ClientMmapManager;
 import org.apache.hadoop.hdfs.net.Peer;
@@ -490,8 +492,8 @@ public class RemoteBlockReader extends FSInputChecker implements BlockReader {
   }
 
   @Override
-  public ClientMmap getClientMmap(LocatedBlock curBlock,
+  public ClientMmap getClientMmap(EnumSet<ReadOption> opts,
-      ClientMmapManager mmapManager) {
+        ClientMmapManager mmapManager) {
     return null;
   }
 }

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/RemoteBlockReader2.java

@@ -25,10 +25,12 @@ import java.io.OutputStream;
 import java.net.InetSocketAddress;
 import java.nio.ByteBuffer;
 import java.nio.channels.ReadableByteChannel;
+import java.util.EnumSet;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.fs.ReadOption;
 import org.apache.hadoop.hdfs.client.ClientMmap;
 import org.apache.hadoop.hdfs.client.ClientMmapManager;
 import org.apache.hadoop.hdfs.net.Peer;
@@ -455,8 +457,8 @@ public class RemoteBlockReader2  implements BlockReader {
   }
 
   @Override
-  public ClientMmap getClientMmap(LocatedBlock curBlock,
+  public ClientMmap getClientMmap(EnumSet<ReadOption> opts,
-      ClientMmapManager manager) {
+        ClientMmapManager mmapManager) {
     return null;
   }
 }

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

@@ -21,10 +21,13 @@ import java.io.BufferedInputStream;
 import java.io.ByteArrayInputStream;
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
+import java.io.EOFException;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.RandomAccessFile;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
 
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.util.DataChecksum;
@@ -67,7 +70,29 @@ public class BlockMetadataHeader {
     return checksum;
   }
 
- 
+  /**
+   * Read the header without changing the position of the FileChannel.
+   *
+   * @param fc The FileChannel to read.
+   * @return the Metadata Header.
+   * @throws IOException on error.
+   */
+  public static BlockMetadataHeader preadHeader(FileChannel fc)
+      throws IOException {
+    byte arr[] = new byte[2 + DataChecksum.HEADER_LEN];
+    ByteBuffer buf = ByteBuffer.wrap(arr);
+
+    while (buf.hasRemaining()) {
+      if (fc.read(buf, 0) <= 0) {
+        throw new EOFException("unexpected EOF while reading " +
+            "metadata file header");
+      }
+    }
+    short version = (short)((arr[0] << 8) | (arr[1] & 0xff));
+    DataChecksum dataChecksum = DataChecksum.newDataChecksum(arr, 2);
+    return new BlockMetadataHeader(version, dataChecksum);
+  }
+
   /**
    * This reads all the fields till the beginning of checksum.
    * @param in 

hadoop-hdfs-project/hadoop-hdfs/src/main/resources/hdfs-default.xml

@@ -1394,12 +1394,15 @@
   <name>dfs.client.cache.readahead</name>
   <value></value>
   <description>
-    Just like dfs.datanode.readahead.bytes, this setting causes the datanode to
+    When using remote reads, this setting causes the datanode to
     read ahead in the block file using posix_fadvise, potentially decreasing
     I/O wait times.  Unlike dfs.datanode.readahead.bytes, this is a client-side
     setting rather than a setting for the entire datanode.  If present, this
     setting will override the DataNode default.
 
+    When using local reads, this setting determines how much readahead we do in
+    BlockReaderLocal.
+
     If the native libraries are not available to the DataNode, this
     configuration has no effect.
   </description>

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/DFSTestUtil.java

@@ -55,6 +55,7 @@ import org.apache.hadoop.util.VersionInfo;
 
 import java.io.*;
 import java.net.*;
+import java.nio.ByteBuffer;
 import java.security.PrivilegedExceptionAction;
 import java.util.*;
 import java.util.concurrent.TimeoutException;
@@ -1018,4 +1019,10 @@ public class DFSTestUtil {
   public static void abortStream(DFSOutputStream out) throws IOException {
     out.abort();
   }
+
+  public static byte[] asArray(ByteBuffer buf) {
+    byte arr[] = new byte[buf.remaining()];
+    buf.duplicate().get(arr);
+    return arr;
+  }
 }

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestBlockReaderLocal.java

@@ -32,6 +32,8 @@ import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hdfs.client.HdfsDataInputStream;
 import org.apache.hadoop.hdfs.protocol.DatanodeID;
 import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
+import org.apache.hadoop.hdfs.server.datanode.BlockMetadataHeader;
+import org.apache.hadoop.hdfs.server.datanode.CachingStrategy;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.net.unix.DomainSocket;
 import org.apache.hadoop.net.unix.TemporarySocketDirectory;
@@ -92,22 +94,35 @@ public class TestBlockReaderLocal {
     }
   }
 
-  private static interface BlockReaderLocalTest {
+  private static class BlockReaderLocalTest {
-    final int TEST_LENGTH = 12345;
+    final static int TEST_LENGTH = 12345;
+    final static int BYTES_PER_CHECKSUM = 512;
+
+    public void setConfiguration(HdfsConfiguration conf) {
+      // default: no-op
+    }
     public void setup(File blockFile, boolean usingChecksums)
-        throws IOException;
+        throws IOException {
+      // default: no-op
+    }
     public void doTest(BlockReaderLocal reader, byte original[])
-        throws IOException;
+        throws IOException {
+      // default: no-op
+    }
   }
   
   public void runBlockReaderLocalTest(BlockReaderLocalTest test,
-      boolean checksum) throws IOException {
+      boolean checksum, long readahead) throws IOException {
     MiniDFSCluster cluster = null;
     HdfsConfiguration conf = new HdfsConfiguration();
     conf.setBoolean(DFSConfigKeys.
         DFS_CLIENT_READ_SHORTCIRCUIT_SKIP_CHECKSUM_KEY, !checksum);
+    conf.setLong(DFSConfigKeys.DFS_BYTES_PER_CHECKSUM_KEY,
+        BlockReaderLocalTest.BYTES_PER_CHECKSUM);
     conf.set(DFSConfigKeys.DFS_CHECKSUM_TYPE_KEY, "CRC32C");
-    FileInputStream dataIn = null, checkIn = null;
+    conf.setLong(DFSConfigKeys.DFS_CLIENT_CACHE_READAHEAD, readahead);
+    test.setConfiguration(conf);
+    FileInputStream dataIn = null, metaIn = null;
     final Path TEST_PATH = new Path("/a");
     final long RANDOM_SEED = 4567L;
     BlockReaderLocal blockReaderLocal = null;
@@ -143,45 +158,51 @@ public class TestBlockReaderLocal {
       cluster.shutdown();
       cluster = null;
       test.setup(dataFile, checksum);
-      dataIn = new FileInputStream(dataFile);
+      FileInputStream streams[] = {
-      checkIn = new FileInputStream(metaFile);
+          new FileInputStream(dataFile),
-      blockReaderLocal = new BlockReaderLocal(new DFSClient.Conf(conf),
+          new FileInputStream(metaFile)
-          TEST_PATH.getName(), block, 0, -1,
+      };
-          dataIn, checkIn, datanodeID, checksum, null);
+      dataIn = streams[0];
+      metaIn = streams[1];
+      blockReaderLocal = new BlockReaderLocal.Builder(
+              new DFSClient.Conf(conf)).
+          setFilename(TEST_PATH.getName()).
+          setBlock(block).
+          setStreams(streams).
+          setDatanodeID(datanodeID).
+          setCachingStrategy(new CachingStrategy(false, readahead)).
+          setVerifyChecksum(checksum).
+          setBlockMetadataHeader(BlockMetadataHeader.preadHeader(
+              metaIn.getChannel())).
+          build();
       dataIn = null;
-      checkIn = null;
+      metaIn = null;
       test.doTest(blockReaderLocal, original);
+      // BlockReaderLocal should not alter the file position.
+      Assert.assertEquals(0, streams[0].getChannel().position());
+      Assert.assertEquals(0, streams[1].getChannel().position());
     } finally {
       if (fsIn != null) fsIn.close();
       if (fs != null) fs.close();
       if (cluster != null) cluster.shutdown();
       if (dataIn != null) dataIn.close();
-      if (checkIn != null) checkIn.close();
+      if (metaIn != null) metaIn.close();
       if (blockReaderLocal != null) blockReaderLocal.close();
     }
   }
   
   private static class TestBlockReaderLocalImmediateClose 
-      implements BlockReaderLocalTest {
+      extends BlockReaderLocalTest {
-    @Override
-    public void setup(File blockFile, boolean usingChecksums)
-        throws IOException { }
-    @Override
-    public void doTest(BlockReaderLocal reader, byte original[]) 
-        throws IOException { }
   }
   
   @Test
   public void testBlockReaderLocalImmediateClose() throws IOException {
-    runBlockReaderLocalTest(new TestBlockReaderLocalImmediateClose(), true);
+    runBlockReaderLocalTest(new TestBlockReaderLocalImmediateClose(), true, 0);
-    runBlockReaderLocalTest(new TestBlockReaderLocalImmediateClose(), false);
+    runBlockReaderLocalTest(new TestBlockReaderLocalImmediateClose(), false, 0);
   }
   
   private static class TestBlockReaderSimpleReads 
-      implements BlockReaderLocalTest {
+      extends BlockReaderLocalTest {
-    @Override
-    public void setup(File blockFile, boolean usingChecksums)
-        throws IOException { }
     @Override
     public void doTest(BlockReaderLocal reader, byte original[]) 
         throws IOException {
@@ -194,24 +215,43 @@ public class TestBlockReaderLocal {
       assertArrayRegionsEqual(original, 1024, buf, 1024, 513);
       reader.readFully(buf, 1537, 514);
       assertArrayRegionsEqual(original, 1537, buf, 1537, 514);
+      // Readahead is always at least the size of one chunk in this test.
+      Assert.assertTrue(reader.getMaxReadaheadLength() >=
+          BlockReaderLocalTest.BYTES_PER_CHECKSUM);
     }
   }
   
   @Test
   public void testBlockReaderSimpleReads() throws IOException {
-    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), true);
+    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), true,
+        DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderSimpleReadsShortReadahead() throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), true,
+        BlockReaderLocalTest.BYTES_PER_CHECKSUM - 1);
   }
 
   @Test
   public void testBlockReaderSimpleReadsNoChecksum() throws IOException {
-    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), false);
+    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), false,
+        DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderSimpleReadsNoReadahead() throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), true, 0);
+  }
+
+  @Test
+  public void testBlockReaderSimpleReadsNoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderSimpleReads(), false, 0);
   }
   
   private static class TestBlockReaderLocalArrayReads2 
-      implements BlockReaderLocalTest {
+      extends BlockReaderLocalTest {
-    @Override
-    public void setup(File blockFile, boolean usingChecksums)
-        throws IOException { }
     @Override
     public void doTest(BlockReaderLocal reader, byte original[]) 
         throws IOException {
@@ -234,21 +274,30 @@ public class TestBlockReaderLocal {
   @Test
   public void testBlockReaderLocalArrayReads2() throws IOException {
     runBlockReaderLocalTest(new TestBlockReaderLocalArrayReads2(),
-        true);
+        true, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
   }
 
   @Test
   public void testBlockReaderLocalArrayReads2NoChecksum()
       throws IOException {
     runBlockReaderLocalTest(new TestBlockReaderLocalArrayReads2(),
-        false);
+        false, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalArrayReads2NoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalArrayReads2(), true, 0);
+  }
+
+  @Test
+  public void testBlockReaderLocalArrayReads2NoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalArrayReads2(), false, 0);
   }
 
   private static class TestBlockReaderLocalByteBufferReads 
-      implements BlockReaderLocalTest {
+      extends BlockReaderLocalTest {
-    @Override
-    public void setup(File blockFile, boolean usingChecksums)
-        throws IOException { }
     @Override
     public void doTest(BlockReaderLocal reader, byte original[]) 
         throws IOException {
@@ -268,19 +317,105 @@ public class TestBlockReaderLocal {
   @Test
   public void testBlockReaderLocalByteBufferReads()
       throws IOException {
-    runBlockReaderLocalTest(
+    runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferReads(),
-        new TestBlockReaderLocalByteBufferReads(), true);
+        true, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
   }
 
   @Test
   public void testBlockReaderLocalByteBufferReadsNoChecksum()
       throws IOException {
     runBlockReaderLocalTest(
-        new TestBlockReaderLocalByteBufferReads(), false);
+        new TestBlockReaderLocalByteBufferReads(),
+        false, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
   }
   
+  @Test
+  public void testBlockReaderLocalByteBufferReadsNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferReads(),
+        true, 0);
+  }
+
+  @Test
+  public void testBlockReaderLocalByteBufferReadsNoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferReads(),
+        false, 0);
+  }
+
+  /**
+   * Test reads that bypass the bounce buffer (because they are aligned
+   * and bigger than the readahead).
+   */
+  private static class TestBlockReaderLocalByteBufferFastLaneReads 
+      extends BlockReaderLocalTest {
+    @Override
+    public void doTest(BlockReaderLocal reader, byte original[])
+        throws IOException {
+      ByteBuffer buf = ByteBuffer.allocateDirect(TEST_LENGTH);
+      readFully(reader, buf, 0, 5120);
+      buf.flip();
+      assertArrayRegionsEqual(original, 0,
+          DFSTestUtil.asArray(buf), 0,
+          5120);
+      reader.skip(1537);
+      readFully(reader, buf, 0, 1);
+      buf.flip();
+      assertArrayRegionsEqual(original, 6657,
+          DFSTestUtil.asArray(buf), 0,
+          1);
+      reader.setMlocked(true);
+      readFully(reader, buf, 0, 5120);
+      buf.flip();
+      assertArrayRegionsEqual(original, 6658,
+          DFSTestUtil.asArray(buf), 0,
+          5120);
+      reader.setMlocked(false);
+      readFully(reader, buf, 0, 513);
+      buf.flip();
+      assertArrayRegionsEqual(original, 11778,
+          DFSTestUtil.asArray(buf), 0,
+          513);
+      reader.skip(3);
+      readFully(reader, buf, 0, 50);
+      buf.flip();
+      assertArrayRegionsEqual(original, 12294,
+          DFSTestUtil.asArray(buf), 0,
+          50);
+    }
+  }
+  
+  @Test
+  public void testBlockReaderLocalByteBufferFastLaneReads()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferFastLaneReads(),
+        true, 2 * BlockReaderLocalTest.BYTES_PER_CHECKSUM);
+  }
+
+  @Test
+  public void testBlockReaderLocalByteBufferFastLaneReadsNoChecksum()
+      throws IOException {
+    runBlockReaderLocalTest(
+        new TestBlockReaderLocalByteBufferFastLaneReads(),
+        false, 2 * BlockReaderLocalTest.BYTES_PER_CHECKSUM);
+  }
+
+  @Test
+  public void testBlockReaderLocalByteBufferFastLaneReadsNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferFastLaneReads(),
+        true, 0);
+  }
+
+  @Test
+  public void testBlockReaderLocalByteBufferFastLaneReadsNoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalByteBufferFastLaneReads(),
+        false, 0);
+  }
+
   private static class TestBlockReaderLocalReadCorruptStart
-      implements BlockReaderLocalTest {
+      extends BlockReaderLocalTest {
     boolean usingChecksums = false;
     @Override
     public void setup(File blockFile, boolean usingChecksums)
@@ -314,11 +449,12 @@ public class TestBlockReaderLocal {
   @Test
   public void testBlockReaderLocalReadCorruptStart()
       throws IOException {
-    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorruptStart(), true);
+    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorruptStart(), true,
+        DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
   }
   
   private static class TestBlockReaderLocalReadCorrupt
-      implements BlockReaderLocalTest {
+      extends BlockReaderLocalTest {
     boolean usingChecksums = false;
     @Override
     public void setup(File blockFile, boolean usingChecksums) 
@@ -364,8 +500,136 @@ public class TestBlockReaderLocal {
   @Test
   public void testBlockReaderLocalReadCorrupt()
       throws IOException {
-    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorrupt(), true);
+    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorrupt(), true,
-    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorrupt(), false);
+        DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalReadCorruptNoChecksum()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorrupt(), false,
+        DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalReadCorruptNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorrupt(), true, 0);
+  }
+
+  @Test
+  public void testBlockReaderLocalReadCorruptNoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalReadCorrupt(), false, 0);
+  }
+
+  private static class TestBlockReaderLocalWithMlockChanges
+      extends BlockReaderLocalTest {
+    @Override
+    public void setup(File blockFile, boolean usingChecksums)
+        throws IOException {
+    }
+    
+    @Override
+    public void doTest(BlockReaderLocal reader, byte original[])
+        throws IOException {
+      ByteBuffer buf = ByteBuffer.wrap(new byte[TEST_LENGTH]);
+      reader.skip(1);
+      readFully(reader, buf, 1, 9);
+      assertArrayRegionsEqual(original, 1, buf.array(), 1, 9);
+      readFully(reader, buf, 10, 100);
+      assertArrayRegionsEqual(original, 10, buf.array(), 10, 100);
+      reader.setMlocked(true);
+      readFully(reader, buf, 110, 700);
+      assertArrayRegionsEqual(original, 110, buf.array(), 110, 700);
+      reader.setMlocked(false);
+      reader.skip(1); // skip from offset 810 to offset 811
+      readFully(reader, buf, 811, 5);
+      assertArrayRegionsEqual(original, 811, buf.array(), 811, 5);
+    }
+  }
+
+  @Test
+  public void testBlockReaderLocalWithMlockChanges()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalWithMlockChanges(),
+        true, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalWithMlockChangesNoChecksum()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalWithMlockChanges(),
+        false, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalWithMlockChangesNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalWithMlockChanges(),
+        true, 0);
+  }
+
+  @Test
+  public void testBlockReaderLocalWithMlockChangesNoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalWithMlockChanges(),
+        false, 0);
+  }
+
+  private static class TestBlockReaderLocalOnFileWithoutChecksum
+      extends BlockReaderLocalTest {
+    @Override
+    public void setConfiguration(HdfsConfiguration conf) {
+      conf.set(DFSConfigKeys.DFS_CHECKSUM_TYPE_KEY, "NULL");
+    }
+
+    @Override
+    public void doTest(BlockReaderLocal reader, byte original[])
+        throws IOException {
+      Assert.assertTrue(!reader.getVerifyChecksum());
+      ByteBuffer buf = ByteBuffer.wrap(new byte[TEST_LENGTH]);
+      reader.skip(1);
+      readFully(reader, buf, 1, 9);
+      assertArrayRegionsEqual(original, 1, buf.array(), 1, 9);
+      readFully(reader, buf, 10, 100);
+      assertArrayRegionsEqual(original, 10, buf.array(), 10, 100);
+      reader.setMlocked(true);
+      readFully(reader, buf, 110, 700);
+      assertArrayRegionsEqual(original, 110, buf.array(), 110, 700);
+      reader.setMlocked(false);
+      reader.skip(1); // skip from offset 810 to offset 811
+      readFully(reader, buf, 811, 5);
+      assertArrayRegionsEqual(original, 811, buf.array(), 811, 5);
+    }
+  }
+
+  @Test
+  public void testBlockReaderLocalOnFileWithoutChecksum()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalOnFileWithoutChecksum(),
+        true, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalOnFileWithoutChecksumNoChecksum()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalOnFileWithoutChecksum(),
+        false, DFSConfigKeys.DFS_DATANODE_READAHEAD_BYTES_DEFAULT);
+  }
+
+  @Test
+  public void testBlockReaderLocalOnFileWithoutChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalOnFileWithoutChecksum(),
+        true, 0);
+  }
+
+  @Test
+  public void testBlockReaderLocalOnFileWithoutChecksumNoChecksumNoReadahead()
+      throws IOException {
+    runBlockReaderLocalTest(new TestBlockReaderLocalOnFileWithoutChecksum(),
+        false, 0);
   }
 
   @Test(timeout=60000)

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestShortCircuitLocalRead.java

@@ -260,7 +260,6 @@ public class TestShortCircuitLocalRead {
       assertTrue("/ should be a directory", fs.getFileStatus(path)
           .isDirectory() == true);
       
-      // create a new file in home directory. Do not close it.
       byte[] fileData = AppendTestUtil.randomBytes(seed, size);
       Path file1 = fs.makeQualified(new Path("filelocal.dat"));
       FSDataOutputStream stm = createFile(fs, file1, 1);