fanotify: allow ignored_masks to survive modify

Some users may want to truely ignore an inode even if it has been modified.
Say you are wanting a mount which contains a log file and you really don't
want any notification about that file.  This patch allows the listener to
do that.

Signed-off-by: Eric Paris <eparis@redhat.com>

fs/notify/fanotify/fanotify_user.c

@@ -375,6 +375,8 @@ static __u32 fanotify_mark_add_to_mask(struct fsnotify_mark *fsn_mark,
 	} else {
 		oldmask = fsn_mark->ignored_mask;
 		fsnotify_set_mark_ignored_mask_locked(fsn_mark, (oldmask | mask));
+		if (flags & FAN_MARK_IGNORED_SURV_MODIFY)
+			fsn_mark->flags |= FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY;
 	}
 	spin_unlock(&fsn_mark->lock);