vfs: make getxattr retry once on an ESTALE error

{

	struct path path;

	ssize_t error;

	error = user_path(pathname, &path);

	unsigned int lookup_flags = LOOKUP_FOLLOW;

retry:

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

	if (error)

		return error;

	error = getxattr(path.dentry, name, value, size);

	path_put(&path);

	if (retry_estale(error, lookup_flags)) {

		lookup_flags |= LOOKUP_REVAL;

		goto retry;

	}

	return error;

}