fsnotify: Clarify connector assignment in fsnotify_add_mark_list()

Add a comment explaining why WRITE_ONCE() is enough when setting mark->connector which can get dereferenced by RCU protected readers. Signed-off-by: Jan Kara <[email protected]>
adn770 · May 1, 2019 · 11a6f8e · 11a6f8e
1 parent b1da6a5
commit 11a6f8e
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
@@ -619,6 +619,11 @@ static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
 	/* mark should be the last entry.  last is the current last entry */
 	hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
 added:
+	/*
+	 * Since connector is attached to object using cmpxchg() we are
+	 * guaranteed that connector initialization is fully visible by anyone
+	 * seeing mark->connector set.
+	 */
 	WRITE_ONCE(mark->connector, conn);
 out_err:
 	spin_unlock(&conn->lock);