[PATCH 0/4] fix up generic dmlogwrites tests to work with XFS

[Brian Foster <bfoster@redhat.com>]

Hi all,

We've still had lingering false positive failure reports on some of
these generic dmlogwrites tests on XFS due to metadata ordering issues.
The logwrites mechanism relies on discard to provide zeroing behavior to
avoid this, but if that is not available, this can result in subtle
failures that take time to diagnose.

This series updates the remaining generic dmlogwrites tests to use the
same scheme we used in generic/482 to address this problem, which is to
explicitly use a thin volume for predictable discard support. It also
adds a discard zeroing behavior check as a backstop against future
tests. The thought crossed my mind of pushing much of this code down
into the common dmlogwrites code to reduce duplication, but I didn't
want to get too deep into the weeds of reworking the common code to
address this problem in a handful of tests.

Thoughts, reviews, flames appreciated.

Brian

Brian Foster (4):
  generic: require discard zero behavior for dmlogwrites on XFS
  generic/455: use thin volume for dmlogwrites target device
  generic/457: use thin volume for dmlogwrites target device
  generic/470: use thin volume for dmlogwrites target device

 common/dmlogwrites | 10 ++++++++--
 common/rc          | 14 ++++++++++++++
 tests/generic/455  | 36 ++++++++++++++++++++++--------------
 tests/generic/457  | 33 +++++++++++++++++++++------------
 tests/generic/470  | 24 ++++++++++++++++++------
 5 files changed, 83 insertions(+), 34 deletions(-)

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2.25.4