btrfs: create example debugfs file only in debugging build

	if (!btrfs_debugfs_root_dentry)

		return -ENOMEM;

	/*

	 * Example code, how to export data through debugfs.

	 *

	 * file:        /sys/kernel/debug/btrfs/test

	 * contents of: btrfs_debugfs_test

	 */

#ifdef CONFIG_BTRFS_DEBUG

	debugfs_create_u64("test", S_IRUGO | S_IWUSR, btrfs_debugfs_root_dentry,

			&btrfs_debugfs_test);

#endif

#endif

	return 0;

}