/** {@inheritDoc} */
 public void validateBlockMetadata(Block b) throws IOException {
   DatanodeBlockInfo info = volumeMap.get(b);
   if (info == null) {
     throw new IOException("Block " + b + " does not exist in volumeMap.");
   }
   FSVolume v = info.getVolume();
   File tmp = v.getTmpFile(b);
   File f = getFile(b);
   if (f == null) {
     f = tmp;
   }
   if (f == null) {
     throw new IOException("Block " + b + " does not exist on disk.");
   }
   if (!f.exists()) {
     throw new IOException("Block " + b + " block file " + f + " does not exist on disk.");
   }
   if (b.getNumBytes() != f.length()) {
     throw new IOException(
         "Block "
             + b
             + " length is "
             + b.getNumBytes()
             + " does not match block file length "
             + f.length());
   }
   File meta = getMetaFile(f, b);
   if (meta == null) {
     throw new IOException("Block " + b + " metafile does not exist.");
   }
   if (!meta.exists()) {
     throw new IOException("Block " + b + " metafile " + meta + " does not exist on disk.");
   }
   if (meta.length() == 0) {
     throw new IOException("Block " + b + " metafile " + meta + " is empty.");
   }
   long stamp = parseGenerationStamp(f, meta);
   if (stamp != b.getGenerationStamp()) {
     throw new IOException(
         "Block "
             + b
             + " genstamp is "
             + b.getGenerationStamp()
             + " does not match meta file stamp "
             + stamp);
   }
 }
  /** Returns handles to the block file and its metadata file */
  public synchronized BlockInputStreams getTmpInputStreams(Block b, long blkOffset, long ckoff)
      throws IOException {

    DatanodeBlockInfo info = volumeMap.get(b);
    if (info == null) {
      throw new IOException("Block " + b + " does not exist in volumeMap.");
    }
    FSVolume v = info.getVolume();
    File blockFile = v.getTmpFile(b);
    RandomAccessFile blockInFile = new RandomAccessFile(blockFile, "r");
    if (blkOffset > 0) {
      blockInFile.seek(blkOffset);
    }
    File metaFile = getMetaFile(blockFile, b);
    RandomAccessFile metaInFile = new RandomAccessFile(metaFile, "r");
    if (ckoff > 0) {
      metaInFile.seek(ckoff);
    }
    return new BlockInputStreams(
        new FileInputStream(blockInFile.getFD()), new FileInputStream(metaInFile.getFD()));
  }
 /**
  * We're informed that a block is no longer valid. We could lazily garbage-collect the block, but
  * why bother? just get rid of it.
  */
 public void invalidate(Block invalidBlks[]) throws IOException {
   boolean error = false;
   for (int i = 0; i < invalidBlks.length; i++) {
     File f = null;
     FSVolume v;
     synchronized (this) {
       f = getFile(invalidBlks[i]);
       DatanodeBlockInfo dinfo = volumeMap.get(invalidBlks[i]);
       if (dinfo == null) {
         DataNode.LOG.warn(
             "Unexpected error trying to delete block "
                 + invalidBlks[i]
                 + ". BlockInfo not found in volumeMap.");
         error = true;
         continue;
       }
       v = dinfo.getVolume();
       if (f == null) {
         DataNode.LOG.warn(
             "Unexpected error trying to delete block "
                 + invalidBlks[i]
                 + ". Block not found in blockMap."
                 + ((v == null) ? " " : " Block found in volumeMap."));
         error = true;
         continue;
       }
       if (v == null) {
         DataNode.LOG.warn(
             "Unexpected error trying to delete block "
                 + invalidBlks[i]
                 + ". No volume for this block."
                 + " Block found in blockMap. "
                 + f
                 + ".");
         error = true;
         continue;
       }
       File parent = f.getParentFile();
       if (parent == null) {
         DataNode.LOG.warn(
             "Unexpected error trying to delete block "
                 + invalidBlks[i]
                 + ". Parent not found for file "
                 + f
                 + ".");
         error = true;
         continue;
       }
       v.clearPath(parent);
       volumeMap.remove(invalidBlks[i]);
     }
     File metaFile = getMetaFile(f, invalidBlks[i]);
     long blockSize = f.length() + metaFile.length();
     if (!f.delete() || (!metaFile.delete() && metaFile.exists())) {
       DataNode.LOG.warn(
           "Unexpected error trying to delete block " + invalidBlks[i] + " at file " + f);
       error = true;
       continue;
     }
     v.decDfsUsed(blockSize);
     DataNode.LOG.info("Deleting block " + invalidBlks[i] + " file " + f);
     if (f.exists()) {
       //
       // This is a temporary check especially for hadoop-1220.
       // This will go away in the future.
       //
       DataNode.LOG.info("File " + f + " was deleted but still exists!");
     }
   }
   if (error) {
     throw new IOException("Error in deleting blocks.");
   }
 }