[scartgap][tdx-signed] overlayfs: cannot append lower layer

[fboudra]

Hi,

I enabled the composefs feature on scarthgap branch to give it try: INHERIT:append = " torizon-signed"

After a successfull build, I deployed on a Verdin i.MX 8M Plus and booted:

Starting systemd-udevd version 255.4^

Enabling fsverity on the ostree repository - this may take a few minutes.

Progress: [==================================================] (25148/25148)

Enabling fsverity succeeded (after 252 seconds).
sysroot.readonly configuration value: 0 (fs writable: 1)
composefs+ostree: Validated commit signature using '/etc/ostree/initramfs-root-binding.key'
composefs: Verifying digest: fe9c82c9151a09dabca19c0423a2c36a1cc82ea6a508a97351c3b0f76ac42a6e
composefs: mounted successfully
[  254.086864] overlayfs: cannot append lower layer

I can log in the OS:

Filesystem                  Size  Used Avail Use% Mounted on
tmpfs                       2.0G   11M  1.9G   1% /run
devtmpfs                    1.7G     0  1.7G   0% /dev
/dev/disk/by-label/otaroot   29G  1.2G   26G   5% /sysroot
overlay                     6.4M  6.4M     0 100% /
overlay                     2.0G   11M  1.9G   1% /etc
tmpfs                       2.0G     0  2.0G   0% /dev/shm
tmpfs                       2.0G     0  2.0G   0% /tmp
tmpfs                       2.0G     0  2.0G   0% /var/volatile

overlay on / type overlay (ro,relatime,lowerdir=/run/ostree/.private/cfsroot-lower::/sysroot/ostree/repo/objects,redirect_dir=on,metacopy=on,verity=require)
overlay on /etc type overlay (rw,relatime,lowerdir=/sysroot.tmp/usr/etc,upperdir=/run/ostree/transient-etc/upper,workdir=/run/ostree/transient-etc/work,uuid=on)

As we can see, there's an error message overlayfs: cannot append lower layer.
Is it expected? How can I test that the feature works as expected?

Thanks.