On Thu, 29 Jul 2021 at 07:27, Amir Goldstein [off-list ref] wrote:

Given that today, subvolume mounts (or any mounts) on the lower layer
are not followed by overlayfs, I don't really see the difference
if mounts are created manually or automatically.
Miklos?

Never tried overlay on btrfs.  Subvolumes AFAIK do not use submounts
currently, they are a sort of hack where the st_dev changes when
crossing the subvolume boundary, but there's no sign of them in
/proc/mounts (there's no d_automount in btrfs).

Thanks,
Miklos