iSCSI Multipath may leave residual paths due to race condition

[Gorka Eguileor]

iSCSI multipath rescan uses iscsiadm --rescan option for nodes and sessions, which can end up recreating devices that had just been removed if there's a race condition between the removal of a SCSI device and the connection of a volume.

The race condition happens if a rescan done when attaching happens right between us removing the path and removing the exported lun, because the rescan will add not only the new path we are attaching, but the old path we are removing, since the lun still hasn't been removed.

This would leave orphaned devices that unnecessarily pollute our environment.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/433104

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/433104
Committed: https://git.openstack.org/cgit/openstack/os-brick/commit/?id=a6e789f27edc5cae84a786f3d3604cc6546820d7
Submitter: Jenkins
Branch: master

commit a6e789f27edc5cae84a786f3d3604cc6546820d7
Author: Gorka Eguileor <email address hidden>
Date: Sun Feb 12 01:58:46 2017 +0100

    Fix iSCSI multipath rescan

    iSCSI multipath rescan uses iscsiadm --rescan option for nodes and
    sessions, which can end up recreating devices that had just been removed
    if there's a race condition between the removal of a SCSI device and the
    connection of a volume.

    The race condition happens if a rescan done when attaching happens right
    between us removing the path and removing the exported lun, because the
    rescan will add not only the new path we are attaching, but the old path
    we are removing, since the lun still hasn't been removed.

    This would leave orphaned devices that unnecessarily pollute our
    environment,

    This patch narrows the rescan to only rescan for the specific target id,
    channel, and lun number if we can find this information.

    When we cannot find this information we do the scan as we were doing it
    before.

    Closes-Bug: #1664032
    Change-Id: I1b3bd34db260165a6ea9ca061f946d6dfcf8553f

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/ocata
Review: https://review.openstack.org/445943

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/os-brick 1.12.0 release.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Sean McGinnis (<email address hidden>) on branch: stable/ocata
Review: https://review.openstack.org/445943
Reason: This review is > 4 weeks without comment, and failed Jenkins the last time it was checked. We are abandoning this for now. Feel free to reactivate the review by pressing the restore button and leaving a 'recheck' comment to get fresh test results.