ANDROID: fsnotify: Notify lower fs of open

If the filesystem being watched supports d_canonical_path,
notify the lower filesystem of the open as well.

Change-Id: I2b1739e068afbaf5eb39950516072bff8345ebfe
Signed-off-by: Daniel Rosenberg <drosen@google.com>
Bug: 70706497
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index e5f03a4d..ff51592 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -213,12 +213,20 @@
 static inline void fsnotify_open(struct file *file)
 {
 	struct path *path = &file->f_path;
+	struct path lower_path;
 	struct inode *inode = path->dentry->d_inode;
+
 	__u32 mask = FS_OPEN;
 
 	if (S_ISDIR(inode->i_mode))
 		mask |= FS_ISDIR;
 
+	if (path->dentry->d_op && path->dentry->d_op->d_canonical_path) {
+		path->dentry->d_op->d_canonical_path(path, &lower_path);
+		fsnotify_parent(&lower_path, NULL, mask);
+		fsnotify(lower_path.dentry->d_inode, mask, &lower_path, FSNOTIFY_EVENT_PATH, NULL, 0);
+		path_put(&lower_path);
+	}
 	fsnotify_parent(path, NULL, mask);
 	fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
 }