inotify: report both events on parent and child with single callback

fsnotify usually calls inotify_handle_event() once for watching parent
to report event with child's name and once for watching child to report
event without child's name.

Do the same thing with a single callback instead of two callbacks when
marks iterator contains both inode and child entries.

Link: https://lore.kernel.org/r/20200716084230.30611-13-amir73il@gmail.comSigned-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/inotify/inotify_fsnotify.c

@@ -55,13 +55,11 @@ static int inotify_merge(struct list_head *list,
 	return event_compare(last_event, event);
 }
 
-int inotify_handle_event(struct fsnotify_group *group, u32 mask,
-			 const void *data, int data_type, struct inode *dir,
-			 const struct qstr *file_name, u32 cookie,
-			 struct fsnotify_iter_info *iter_info)
+static int inotify_one_event(struct fsnotify_group *group, u32 mask,
+			     struct fsnotify_mark *inode_mark,
+			     const struct path *path,
+			     const struct qstr *file_name, u32 cookie)
 {
-	const struct path *path = fsnotify_data_path(data, data_type);
-	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
 	struct inotify_inode_mark *i_mark;
 	struct inotify_event_info *event;
 	struct fsnotify_event *fsn_event;
@@ -69,9 +67,6 @@ int inotify_handle_event(struct fsnotify_group *group, u32 mask,
 	int len = 0;
 	int alloc_len = sizeof(struct inotify_event_info);
 
-	if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
-		return 0;
-
 	if ((inode_mark->mask & FS_EXCL_UNLINK) &&
 	    path && d_unlinked(path->dentry))
 		return 0;
@@ -135,6 +130,37 @@ int inotify_handle_event(struct fsnotify_group *group, u32 mask,
 	return 0;
 }
 
+int inotify_handle_event(struct fsnotify_group *group, u32 mask,
+			 const void *data, int data_type, struct inode *dir,
+			 const struct qstr *file_name, u32 cookie,
+			 struct fsnotify_iter_info *iter_info)
+{
+	const struct path *path = fsnotify_data_path(data, data_type);
+	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
+	struct fsnotify_mark *child_mark = fsnotify_iter_child_mark(iter_info);
+	int ret = 0;
+
+	if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
+		return 0;
+
+	/*
+	 * Some events cannot be sent on both parent and child marks
+	 * (e.g. IN_CREATE).  Those events are always sent on inode_mark.
+	 * For events that are possible on both parent and child (e.g. IN_OPEN),
+	 * event is sent on inode_mark with name if the parent is watching and
+	 * is sent on child_mark without name if child is watching.
+	 * If both parent and child are watching, report the event with child's
+	 * name here and report another event without child's name below.
+	 */
+	if (inode_mark)
+		ret = inotify_one_event(group, mask, inode_mark, path,
+					file_name, cookie);
+	if (ret || !child_mark)
+		return ret;
+
+	return inotify_one_event(group, mask, child_mark, path, NULL, 0);
+}
+
 static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
 {
 	inotify_ignored_and_remove_idr(fsn_mark, group);