On Fri, Aug 6, 2021 at 10:52 AM Miklos Szeredi [off-list ref] wrote:

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

quoted

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).

That's what Niel's patch 11/11 is proposing to add and that's the reason
he was asking if this is going to break overlayfs over btrfs.

My question was, regardless of btrfs, can ovl_lookup() treat automount
dentries gracefully as empty dirs or just read them as is, instead of
returning EREMOTE on lookup?

The rationale is that we use a private mount and we are not following
across mounts from layers anyway, so what do we care about
auto or manual mounts?

Thanks,
Amir.