Comment 3 for bug 1908855

Compare the mount command from mount_union:

* 078708192bba5 ("Add support for user defined mount options")
mount -t overlay overlay /mnt -orw,redirect_dir=on -olowerdir=/lower,upperdir=/upper/0/u,workdir=/upper/0/w

* 019085f43d7e6 ("Relax layers check for older kernels")
mount -t overlay overlay /mnt -orw,redirect_dir=on,xino=on,lowerdir=/lower,upperdir=/upper/0/u,workdir=/upper/0/w

The difference here is the -olowerdir and the absence of xino=on.

If the test case changed from:
  sudo ./run --ov

To:
  sudo ./run --ov --xino

And this would pass with the latest commit in the test suite.

We need to confirm this is an expected behaviour and change our test case accordingly if needed.