Greg Kroah-Hartman [off-list ref] wrote:

+	fd = do_sys_open(dfd, filename, flags, 0000);
+	if (fd <= 0)
+		return fd;
+
+	retval = ksys_read(fd, buffer, bufsize);
+
+	__close_fd(current->files, fd);

If you can use dentry_open() and vfs_read(), you might be able to avoid
dealing with file descriptors entirely.  That might make it worth a syscall.

You're going to be asked for writefile() you know ;-)

David