vfs: fix user_statfs to retry once on ESTALE errors

int user_statfs(const char __user *pathname, struct kstatfs *st)

{

	struct path path;

	int error = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);

	int error;

	unsigned int lookup_flags = LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT;

retry:

	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);

	if (!error) {

		error = vfs_statfs(&path, st);

		path_put(&path);

		if (retry_estale(error, lookup_flags)) {

			lookup_flags |= LOOKUP_REVAL;

			goto retry;

		}

	}

	return error;

}