diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index e4e01a99201a..b26b8b363f7f 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -426,6 +426,10 @@ struct btrfs_space_info {
 	struct list_head ro_bgs;
 	struct list_head priority_tickets;
 	struct list_head tickets;
+	/*
+	 * tickets_id just indicates the next ticket will be handled, so note
+	 * it's not stored per ticket.
+	 */
 	u64 tickets_id;
 
 	struct rw_semaphore groups_sem;