fsnotify: generate FS_RENAME event with rich information

The dnotify FS_DN_RENAME event is used to request notification about
a move within the same parent directory and was always coupled with
the FS_MOVED_FROM event.

Rename the FS_DN_RENAME event flag to FS_RENAME, decouple it from
FS_MOVED_FROM and report it with the moved dentry instead of the moved
inode, so it has the information about both old and new parent and name.

Generate the FS_RENAME event regardless of same parent dir and apply
the "same parent" rule in the generic fsnotify_handle_event() helper
that is used to call backends with ->handle_inode_event() method
(i.e. dnotify).  The ->handle_inode_event() method is not rich enough to
report both old and new parent and name anyway.

The enriched event is reported to fanotify over the ->handle_event()
method with the old and new dir inode marks in marks array slots for
ITER_TYPE_INODE and a new iter type slot ITER_TYPE_INODE2.

The enriched event will be used for reporting old and new parent+name to
fanotify groups with FAN_RENAME events.

Link: https://lore.kernel.org/r/20211129201537.1932819-5-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

3 files changed, 11 insertions, 7 deletions

diff --git a/include/linux/dnotify.h b/include/linux/dnotify.h
index 0aad774beaec..b87c3b85a166 100644
--- a/include/linux/dnotify.h
+++ b/include/linux/dnotify.h
@@ -26,7 +26,7 @@ struct dnotify_struct {
 			    FS_MODIFY | FS_MODIFY_CHILD |\
 			    FS_ACCESS | FS_ACCESS_CHILD |\
 			    FS_ATTRIB | FS_ATTRIB_CHILD |\
-			    FS_CREATE | FS_DN_RENAME |\
+			    FS_CREATE | FS_RENAME |\
 			    FS_MOVED_FROM | FS_MOVED_TO)
 
 extern int dir_notify_enable;
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 787545e87eeb..3a2d7dc3c607 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -144,16 +144,19 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
 	u32 fs_cookie = fsnotify_get_cookie();
 	__u32 old_dir_mask = FS_MOVED_FROM;
 	__u32 new_dir_mask = FS_MOVED_TO;
+	__u32 rename_mask = FS_RENAME;
 	const struct qstr *new_name = &moved->d_name;
 
-	if (old_dir == new_dir)
-		old_dir_mask |= FS_DN_RENAME;
-
 	if (isdir) {
 		old_dir_mask |= FS_ISDIR;
 		new_dir_mask |= FS_ISDIR;
+		rename_mask |= FS_ISDIR;
 	}
 
+	/* Event with information about both old and new parent+name */
+	fsnotify_name(rename_mask, moved, FSNOTIFY_EVENT_DENTRY,
+		      old_dir, old_name, 0);
+
 	fsnotify_name(old_dir_mask, source, FSNOTIFY_EVENT_INODE,
 		      old_dir, old_name, fs_cookie);
 	fsnotify_name(new_dir_mask, source, FSNOTIFY_EVENT_INODE,
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 73739fee1710..790c31844db5 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -63,7 +63,7 @@
  */
 #define FS_EVENT_ON_CHILD	0x08000000
 
-#define FS_DN_RENAME		0x10000000	/* file renamed */
+#define FS_RENAME		0x10000000	/* File was renamed */
 #define FS_DN_MULTISHOT		0x20000000	/* dnotify multishot */
 #define FS_ISDIR		0x40000000	/* event occurred against dir */
 #define FS_IN_ONESHOT		0x80000000	/* only send event once */
@@ -76,7 +76,7 @@
  * The watching parent may get an FS_ATTRIB|FS_EVENT_ON_CHILD event
  * when a directory entry inside a child subdir changes.
  */
-#define ALL_FSNOTIFY_DIRENT_EVENTS	(FS_CREATE | FS_DELETE | FS_MOVE)
+#define ALL_FSNOTIFY_DIRENT_EVENTS (FS_CREATE | FS_DELETE | FS_MOVE | FS_RENAME)
 
 #define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \
 				  FS_OPEN_EXEC_PERM)
@@ -101,7 +101,7 @@
 /* Events that can be reported to backends */
 #define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
 			     FS_EVENTS_POSS_ON_CHILD | \
-			     FS_DELETE_SELF | FS_MOVE_SELF | FS_DN_RENAME | \
+			     FS_DELETE_SELF | FS_MOVE_SELF | \
 			     FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED | \
 			     FS_ERROR)
 
@@ -349,6 +349,7 @@ enum fsnotify_iter_type {
 	FSNOTIFY_ITER_TYPE_VFSMOUNT,
 	FSNOTIFY_ITER_TYPE_SB,
 	FSNOTIFY_ITER_TYPE_PARENT,
+	FSNOTIFY_ITER_TYPE_INODE2,
 	FSNOTIFY_ITER_TYPE_COUNT
 };