image conversion dir creation is racy

[Eric Harney]

_create_from_image_cache_or_download does

        if (CONF.image_conversion_dir and not
                os.path.exists(CONF.image_conversion_dir)):
            os.makedirs(CONF.image_conversion_dir)

This can race between multiple threads/processes.

os.makedirs errors resulting from the dir already existing should be ignored.

[Sean McGinnis (sean-mcginnis)]

Should probably use this from oslo.utils:

https://github.com/openstack/oslo.utils/blob/6b347590667d847c13c25a6c4746041cc04d3384/oslo_utils/fileutils.py#L34

[Sean McGinnis (sean-mcginnis)]

And mocking of that call should be done in unit tests to make sure unit test runs don't create local filesystem changes.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/569001

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/569001
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=60c0b9c0af8c056b952c782dc00ccfa84a8b3e05
Submitter: Zuul
Branch: master

commit 60c0b9c0af8c056b952c782dc00ccfa84a8b3e05
Author: smartu3 <email address hidden>
Date: Thu May 17 11:29:59 2018 +0800

    Replace os.makedirs to avoid process race

    Use oslo_utils.fileutils.ensure_tree(path, mode=_DEFAULT_MODE)
    to replace os.makedir.

    Co-Authored-By: ycx <email address hidden>

    Change-Id: Ia5de63768171aa715da6318e768cce1420fef302
    Closes-Bug: #1757521

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 13.0.0.0b3 development milestone.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/queens
Review: https://review.openstack.org/593044

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/593044
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=24066d51aad46b0dc11484a3ce43925655f82f24
Submitter: Zuul
Branch: stable/queens

commit 24066d51aad46b0dc11484a3ce43925655f82f24
Author: smartu3 <email address hidden>
Date: Thu May 17 11:29:59 2018 +0800

    Replace os.makedirs to avoid process race

    Use oslo_utils.fileutils.ensure_tree(path, mode=_DEFAULT_MODE)
    to replace os.makedir.

    Co-Authored-By: ycx <email address hidden>

    Change-Id: Ia5de63768171aa715da6318e768cce1420fef302
    Closes-Bug: #1757521
    (cherry picked from commit 60c0b9c0af8c056b952c782dc00ccfa84a8b3e05)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 12.0.4 release.