Is module overlay always required to run dockerd?

I have found my dockerd failed to start recently. I have traced logs and found that in /lib/systemd/system/containerd.service it has a pre start command modprobe overlay. Actually I’m using devicemapper. So I’m confused, is module overlay always required even not using overlay as storage device?

BTW, I have found a interesting thing. overlay is existed when I run lsmod but not found when I run modprobe overlay. Could anyone tell me what’s going on?