ubuntu_unionmount_ovlfs failed on X/T-LTS-X with latest update in upstream testsuite

[Po-Hsu Lin]

A bisect shows this test is failing since commit 2104e51db38 (Simplify initialization of __upper)

The test will fail with:
  ***
  *** ./run --ov --ts=0 rmtree
  ***
  TEST rmtree.py:4: Recursive remove populated lower dir with lower files
  - rmtree /mnt/a/dir100
  ***
  *** ./run --ov --ts=0 rmtree-new
  ***
  TEST rmtree-new.py:4: Recursive remove populated lower dir with new subdir
   ./run --mkdir /mnt/a/dir100/b 0755
  - rmtree /mnt/a/dir100
  ***
  *** ./run --ov --ts=0 hard-link
  ***
  TEST hard-link.py:10: Hard link file
   ./run --link /mnt/a/foo100 /mnt/a/no_foo100
  stderr:
  /mnt/a/foo100: File unexpectedly on upper layer

For the complete test log, please refer the attachment.

HEAD now is 1724ef2

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-169-generic 4.4.0-169.198
ProcVersionSignature: User Name 4.4.0-169.198-generic 4.4.197
Uname: Linux 4.4.0-169-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.21
Architecture: amd64
Date: Thu Nov 28 04:21:52 2019
SourcePackage: linux-signed
UpgradeStatus: No upgrade log present (probably fresh install)

[Po-Hsu Lin (cypressyew)]

It looks like this is OK with X-4.15 but not X-4.4 / T-4.4.

Maybe something in the kernel has to do with this as well.

[Po-Hsu Lin (cypressyew)]

Verified on X-4.4 KVM, if the HEAD commit reverted back to 1fc2eec2 (Fix ./run --ov --verify --recycle)
The test will pass.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Sean Feole (sfeole)]

affected xenial 4.4

Confirmed reported that this test will pass on xenial 4.4 if we revert branch to commit 1fc2eec2, thus dropping everything after.

May be worth it to generate a patch if os.series == 16.04, drop commit# 2104e51db38

[Po-Hsu Lin (cypressyew)]

On Xenial 4.4 it's now failing with:

Running './run --ov'
 ***
 *** ./run --ov --ts=0 open-plain
 ***
 TEST open-plain.py:10: Open O_RDONLY
 /mnt/a/foo100: File unexpectedly on lower fs

[Po-Hsu Lin (cypressyew)]

Contacted upstream, this issue has been fixed with the following commit:
https://github.com/amir73il/unionmount-testsuite/commit/019085f43d7e6426378ccfd3deeb23e127449e3e