fanotify: wire up FAN_RENAME event

FAN_RENAME is the successor of FAN_MOVED_FROM and FAN_MOVED_TO
and can be used to get the old and new parent+name information in
a single event.

FAN_MOVED_FROM and FAN_MOVED_TO are still supported for backward
compatibility, but it makes little sense to use them together with
FAN_RENAME in the same group.

FAN_RENAME uses special info type records to report the old and
new parent+name, so reporting only old and new parent id is less
useful and was not implemented.
Therefore, FAN_REANAME requires a group with flag FAN_REPORT_NAME.

Link: https://lore.kernel.org/r/20211129201537.1932819-12-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

Author: amir73il

fs/notify/fanotify/fanotify.c

@@ -930,7 +930,7 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
 	BUILD_BUG_ON(FAN_FS_ERROR != FS_ERROR);
 	BUILD_BUG_ON(FAN_RENAME != FS_RENAME);
 
-	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 20);
+	BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 21);
 
 	mask = fanotify_group_event_mask(group, iter_info, &match_mask,
 					 mask, data, data_type, dir);

fs/notify/fanotify/fanotify_user.c

@@ -1586,6 +1586,14 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	    (!fid_mode || mark_type == FAN_MARK_MOUNT))
 		goto fput_and_out;
 
+	/*
+	 * FAN_RENAME uses special info type records to report the old and
+	 * new parent+name.  Reporting only old and new parent id is less
+	 * useful and was not implemented.
+	 */
+	if (mask & FAN_RENAME && !(fid_mode & FAN_REPORT_NAME))
+		goto fput_and_out;
+
 	if (flags & FAN_MARK_FLUSH) {
 		ret = 0;
 		if (mark_type == FAN_MARK_MOUNT)

include/linux/fanotify.h

@@ -82,7 +82,8 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */
  * 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)
+#define FANOTIFY_DIRENT_EVENTS	(FAN_MOVE | FAN_CREATE | FAN_DELETE | \
+				 FAN_RENAME)
 
 /* Events that can be reported with event->fd */
 #define FANOTIFY_FD_EVENTS (FANOTIFY_PATH_EVENTS | FANOTIFY_PERM_EVENTS)