fanotify: turn off support for FAN_DIR_MODIFY

FAN_DIR_MODIFY has been enabled by commit 44d705b037 ("fanotify:
report name info for FAN_DIR_MODIFY event") in 5.7-rc1. Now we are
planning further extensions to the fanotify API and during that we
realized that FAN_DIR_MODIFY may behave slightly differently to be more
consistent with extensions we plan. So until we finalize these
extensions, let's not bind our hands with exposing FAN_DIR_MODIFY to
userland.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/fanotify/fanotify.c

@@ -520,7 +520,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
 	BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 20);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19);
 
 	mask = fanotify_group_event_mask(group, iter_info, mask, data,
 					 data_type);

include/linux/fanotify.h

@@ -47,8 +47,7 @@
  * Directory entry modification events - reported only to directory
  * where entry is modified and not to a watching parent.
  */
-#define FANOTIFY_DIRENT_EVENTS	(FAN_MOVE | FAN_CREATE | FAN_DELETE | \
-				 FAN_DIR_MODIFY)
+#define FANOTIFY_DIRENT_EVENTS	(FAN_MOVE | FAN_CREATE | FAN_DELETE)
 
 /* Events that can only be reported with data type FSNOTIFY_EVENT_INODE */
 #define FANOTIFY_INODE_EVENTS	(FANOTIFY_DIRENT_EVENTS | \