fanotify: limit number of listeners per user

fanotify currently has no limit on the number of listeners a given user can
have open.  This patch limits the total number of listeners per user to
128.  This is the same as the inotify default limit.

Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/include/linux/sched.h b/include/linux/sched.h
index be7adb7..6f420ba 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -672,6 +672,9 @@
 	atomic_t inotify_watches; /* How many inotify watches does this user have? */
 	atomic_t inotify_devs;	/* How many inotify devs does this user have opened? */
 #endif
+#ifdef CONFIG_FANOTIFY
+	atomic_t fanotify_listeners;
+#endif
 #ifdef CONFIG_EPOLL
 	atomic_t epoll_watches;	/* The number of file descriptors currently watched */
 #endif