SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
{
	if (unlikely(newfd == oldfd)) { /* corner case */
		struct files_struct *files = current->files;
		int retval = oldfd;

		rcu_read_lock();
		if (!files_lookup_fd_rcu(files, oldfd))
			retval = -EBADF;
		rcu_read_unlock();
		return retval;
	}
	return ksys_dup3(oldfd, newfd, 0);
}
SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
{
	if (unlikely(newfd == oldfd)) {  
		struct files_struct *files = current->files;
		int retval = oldfd;

		rcu_read_lock();
		if (!files_lookup_fd_rcu(files, oldfd))
			retval = -EBADF;
		rcu_read_unlock();
		return retval;
	}
	return ksys_dup3(oldfd, newfd, 0);
}