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);
 

include/linux/fanotify.h

@@ -31,13 +31,15 @@
 #define FAN_MARK_ONLYDIR	0x00000008
 #define FAN_MARK_MOUNT		0x00000010
 #define FAN_MARK_IGNORED_MASK	0x00000020
+#define FAN_MARK_IGNORED_SURV_MODIFY	0x00000040
 
 #define FAN_ALL_MARK_FLAGS	(FAN_MARK_ADD |\
 				 FAN_MARK_REMOVE |\
 				 FAN_MARK_DONT_FOLLOW |\
 				 FAN_MARK_ONLYDIR |\
 				 FAN_MARK_MOUNT |\
-				 FAN_MARK_IGNORED_MASK)
+				 FAN_MARK_IGNORED_MASK |\
+				 FAN_MARK_IGNORED_SURV_MODIFY)
 
 /*
  * All of the events - we build the list by hand so that we can add flags in