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

For some events (e.g. DN_ATTRIB on sub-directory) fsnotify may call
dnotify_handle_event() once for watching parent and once again for
the watching sub-directory.

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/20200716084230.30611-12-amir73il@gmail.comSigned-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/dnotify/dnotify.c

@@ -70,26 +70,15 @@ static void dnotify_recalc_inode_mask(struct fsnotify_mark *fsn_mark)
  * destroy the dnotify struct if it was not registered to receive multiple
  * events.
  */
-static int dnotify_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 void dnotify_one_event(struct fsnotify_group *group, u32 mask,
+			      struct fsnotify_mark *inode_mark)
 {
-	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
 	struct dnotify_mark *dn_mark;
 	struct dnotify_struct *dn;
 	struct dnotify_struct **prev;
 	struct fown_struct *fown;
 	__u32 test_mask = mask & ~FS_EVENT_ON_CHILD;
 
-	/* not a dir, dnotify doesn't care */
-	if (!dir && !(mask & FS_ISDIR))
-		return 0;
-
-	if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
-		return 0;
-
 	dn_mark = container_of(inode_mark, struct dnotify_mark, fsn_mark);
 
 	spin_lock(&inode_mark->lock);
@@ -111,6 +100,33 @@ static int dnotify_handle_event(struct fsnotify_group *group, u32 mask,
 	}
 
 	spin_unlock(&inode_mark->lock);
+}
+
+static int dnotify_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)
+{
+	struct fsnotify_mark *inode_mark = fsnotify_iter_inode_mark(iter_info);
+	struct fsnotify_mark *child_mark = fsnotify_iter_child_mark(iter_info);
+
+	/* not a dir, dnotify doesn't care */
+	if (!dir && !(mask & FS_ISDIR))
+		return 0;
+
+	if (WARN_ON(fsnotify_iter_vfsmount_mark(iter_info)))
+		return 0;
+
+	/*
+	 * Some events can be sent on both parent dir and subdir marks
+	 * (e.g. DN_ATTRIB).  If both parent dir and subdir are watching,
+	 * report the event once to parent dir and once to subdir.
+	 */
+	if (inode_mark)
+		dnotify_one_event(group, mask, inode_mark);
+	if (child_mark)
+		dnotify_one_event(group, mask, child_mark);
 
 	return 0;
 }