int path_umount(struct path *path, int flags)
{
	struct mount *mnt = real_mount(path->mnt);
	int ret;

	ret = can_umount(path, flags);
	if (!ret)
		ret = do_umount(mnt, flags);

	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
	dput(path->dentry);
	mntput_no_expire(mnt);
	return ret;
}
int path_umount(struct path *path, int flags)
{
	struct mount *mnt = real_mount(path->mnt);
	int ret;

	ret = can_umount(path, flags);
	if (!ret)
		ret = do_umount(mnt, flags);

	 
	dput(path->dentry);
	mntput_no_expire(mnt);
	return ret;
}