import org.apache.hadoop.hdfs.nfs.nfs3.WriteCtx.DataState; //导入依赖的package包/类
/**
 * Creates and adds a WriteCtx into the pendingWrites map. This is a
 * synchronized method to handle concurrent writes.
 *
 * @return A non-null {@link WriteCtx} instance if the incoming write
 * request's offset >= nextOffset. Otherwise null.
 */
private synchronized WriteCtx addWritesToCache(WRITE3Request request,
    Channel channel, int xid) {
  long offset = request.getOffset();
  int count = request.getCount();
  long cachedOffset = nextOffset.get();
  int originalCount = WriteCtx.INVALID_ORIGINAL_COUNT;
  
  if (LOG.isDebugEnabled()) {
    LOG.debug(
        "requesed offset=" + offset + " and current offset=" + cachedOffset);
  }

  // Handle a special case first
  if ((offset < cachedOffset) && (offset + count > cachedOffset)) {
    // One Linux client behavior: after a file is closed and reopened to
    // write, the client sometimes combines previous written data(could still
    // be in kernel buffer) with newly appended data in one write. This is
    // usually the first write after file reopened. In this
    // case, we log the event and drop the overlapped section.
    LOG.warn(String.format(
        "Got overwrite with appended data (%d-%d)," + " current offset %d," +
            " drop the overlapped section (%d-%d)" +
            " and append new data (%d-%d).", offset, (offset + count - 1),
        cachedOffset, offset, (cachedOffset - 1), cachedOffset,
        (offset + count - 1)));

    if (!pendingWrites.isEmpty()) {
      LOG.warn("There are other pending writes, fail this jumbo write");
      return null;
    }
    
    LOG.warn("Modify this write to write only the appended data");
    alterWriteRequest(request, cachedOffset);

    // Update local variable
    originalCount = count;
    offset = request.getOffset();
    count = request.getCount();
  }
  
  // Fail non-append call
  if (offset < cachedOffset) {
    LOG.warn("(offset,count,nextOffset):" + "(" + offset + "," + count + "," +
        nextOffset + ")");
    return null;
  } else {
    DataState dataState =
        offset == cachedOffset ? WriteCtx.DataState.NO_DUMP :
            WriteCtx.DataState.ALLOW_DUMP;
    WriteCtx writeCtx = new WriteCtx(request.getHandle(), request.getOffset(),
        request.getCount(), originalCount, request.getStableHow(),
        request.getData(), channel, xid, false, dataState);
    if (LOG.isDebugEnabled()) {
      LOG.debug("Add new write to the list with nextOffset " + cachedOffset +
          " and requesed offset=" + offset);
    }
    if (writeCtx.getDataState() == WriteCtx.DataState.ALLOW_DUMP) {
      // update the memory size
      updateNonSequentialWriteInMemory(count);
    }
    // check if there is a WriteCtx with the same range in pendingWrites
    WriteCtx oldWriteCtx = checkRepeatedWriteRequest(request, channel, xid);
    if (oldWriteCtx == null) {
      addWrite(writeCtx);
    } else {
      LOG.warn("Got a repeated request, same range, with xid:" +
          writeCtx.getXid());
    }
    return writeCtx;
  }
}
 

import org.apache.hadoop.hdfs.nfs.nfs3.WriteCtx.DataState; //导入依赖的package包/类
/**
 * Creates and adds a WriteCtx into the pendingWrites map. This is a
 * synchronized method to handle concurrent writes.
 * 
 * @return A non-null {@link WriteCtx} instance if the incoming write
 *         request's offset >= nextOffset. Otherwise null.
 */
private synchronized WriteCtx addWritesToCache(WRITE3Request request,
    Channel channel, int xid) {
  long offset = request.getOffset();
  int count = request.getCount();
  long cachedOffset = nextOffset.get();
  int originalCount = WriteCtx.INVALID_ORIGINAL_COUNT;
  
  if (LOG.isDebugEnabled()) {
    LOG.debug("requesed offset=" + offset + " and current offset="
        + cachedOffset);
  }

  // Handle a special case first
  if ((offset < cachedOffset) && (offset + count > cachedOffset)) {
    // One Linux client behavior: after a file is closed and reopened to
    // write, the client sometimes combines previous written data(could still
    // be in kernel buffer) with newly appended data in one write. This is
    // usually the first write after file reopened. In this
    // case, we log the event and drop the overlapped section.
    LOG.warn(String.format("Got overwrite with appended data (%d-%d),"
        + " current offset %d," + " drop the overlapped section (%d-%d)"
        + " and append new data (%d-%d).", offset, (offset + count - 1),
        cachedOffset, offset, (cachedOffset - 1), cachedOffset, (offset
            + count - 1)));

    if (!pendingWrites.isEmpty()) {
      LOG.warn("There are other pending writes, fail this jumbo write");
      return null;
    }
    
    LOG.warn("Modify this write to write only the appended data");
    alterWriteRequest(request, cachedOffset);

    // Update local variable
    originalCount = count;
    offset = request.getOffset();
    count = request.getCount();
  }
  
  // Fail non-append call
  if (offset < cachedOffset) {
    LOG.warn("(offset,count,nextOffset):" + "(" + offset + "," + count + ","
        + nextOffset + ")");
    return null;
  } else {
    DataState dataState = offset == cachedOffset ? WriteCtx.DataState.NO_DUMP
        : WriteCtx.DataState.ALLOW_DUMP;
    WriteCtx writeCtx = new WriteCtx(request.getHandle(),
        request.getOffset(), request.getCount(), originalCount,
        request.getStableHow(), request.getData(), channel, xid, false,
        dataState);
    if (LOG.isDebugEnabled()) {
      LOG.debug("Add new write to the list with nextOffset " + cachedOffset
          + " and requesed offset=" + offset);
    }
    if (writeCtx.getDataState() == WriteCtx.DataState.ALLOW_DUMP) {
      // update the memory size
      updateNonSequentialWriteInMemory(count);
    }
    // check if there is a WriteCtx with the same range in pendingWrites
    WriteCtx oldWriteCtx = checkRepeatedWriteRequest(request, channel, xid);
    if (oldWriteCtx == null) {
      addWrite(writeCtx);
    } else {
      LOG.warn("Got a repeated request, same range, with xid:"
          + writeCtx.getXid());
    }
    return writeCtx;
  }
}