+ /*
+ * In the delegation case we need mutual exclusion with
+ * a number of operations that take the i_mutex. We trylock
+ * because delegations are an optional optimization, and if
+ * there's some chance of a conflict--we'd rather not
+ * bother, maybe that's a sign this just isn't a good file to
+ * hand out a delegation on.
+ */
+ if (is_deleg && !mutex_trylock(&inode->i_mutex))
+ return -EAGAIN;
+
+ if (is_deleg && arg == F_WRLCK) {
+ /* Write delegations are not currently supported: */
+ mutex_unlock(&inode->i_mutex);
+ WARN_ON_ONCE(1);
+ return -EINVAL;
+ }