ioeventfd: Always add a new event to the list

With vhost, the USER_POLL flags isn't passed to ioeventfd__add_event,
the function returns early and doesn't add the new event to the
used_ioevents list. As a result ioeventfd__del_event doesn't remove the
KVM event or free the structure. Always add the event to the list.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/ioeventfd.c b/ioeventfd.c
index bce6861..186ac70 100644
--- a/ioeventfd.c
+++ b/ioeventfd.c
@@ -154,18 +154,17 @@
 		goto cleanup;
 	}
 
-	if (!(flags & IOEVENTFD_FLAG_USER_POLL))
-		return 0;
+	if (flags & IOEVENTFD_FLAG_USER_POLL) {
+		epoll_event = (struct epoll_event) {
+			.events		= EPOLLIN,
+			.data.ptr	= new_ioevent,
+		};
 
-	epoll_event = (struct epoll_event) {
-		.events		= EPOLLIN,
-		.data.ptr	= new_ioevent,
-	};
-
-	r = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, event, &epoll_event);
-	if (r) {
-		r = -errno;
-		goto cleanup;
+		r = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, event, &epoll_event);
+		if (r) {
+			r = -errno;
+			goto cleanup;
+		}
 	}
 
 	list_add_tail(&new_ioevent->list, &used_ioevents);