if fd.Destroy != nil {
		fd.Destroy()
	}
	return nil
}

// Close handles the locking for closing an FD. The real operation
// is in the net package.
func (fd *FD) Close() error {
	if !fd.fdmu.increfAndClose() {
		return errClosing(fd.isFile)
	}
	return nil
}

// Read implements io.Reader.
func (fd *FD) Read(fn func([]byte) (int, error), b []byte) (int, error) {
	if err := fd.readLock(); err != nil {