ubuntu_unionmount_ovlfs failed with "File not on union layer" on B-azure-5.4

[Po-Hsu Lin]

Issue found on 5.4.0-1035.36~18.04.1
Test failed with:
 /mnt/a/foo100: File not on union layer

Test log:
 Running './run --ov'
 /mnt/a/foo100: File not on union layer
 Environment variables:

 ***
 *** ./run --ov --xino open-plain
 ***
 TEST open-plain.py:10: Open O_RDONLY

As this test has passed with B-azure-5.4.0-1033.34~18.04.1 it looks like a regression here.

[Po-Hsu Lin (cypressyew)]

This issue does not exist on Focal 5.4 and Bionic 5.4 generic kernel, which were tested about 6 days ago.

There is an update in the test suite upstream, will need to check if that is the cause.

[Po-Hsu Lin (cypressyew)]

A bisect against the test suite shows this was caused by the recent update:

078708192bba5337afbec0952e104bd587824e65
Add support for user defined mount options

$ sudo git bisect log
git bisect start
# good: [7e2a4dbfac7c51415f6d3875a50e1c93bf3eae9d] Support metacopy with nested overlay configuration
git bisect good 7e2a4dbfac7c51415f6d3875a50e1c93bf3eae9d
# bad: [95be14ee4dd75c5a2b2ae4d05df6c8810ac09737] Allow user provided options with or without -o
git bisect bad 95be14ee4dd75c5a2b2ae4d05df6c8810ac09737
# bad: [078708192bba5337afbec0952e104bd587824e65] Add support for user defined mount options
git bisect bad 078708192bba5337afbec0952e104bd587824e65
# good: [019085f43d7e6426378ccfd3deeb23e127449e3e] Relax layers check for older kernels
git bisect good 019085f43d7e6426378ccfd3deeb23e127449e3e
# first bad commit: [078708192bba5337afbec0952e104bd587824e65] Add support for user defined mount options

[Po-Hsu Lin (cypressyew)]

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.

[Po-Hsu Lin (cypressyew)]

Issue reported upstream to confirm the use case.
https://github.com/amir73il/unionmount-testsuite/issues/5

[Po-Hsu Lin (cypressyew)]

Issue fixed upstream. Retested with positive results.
Closing this bug.