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[melanie witt <1939545@xxxxxxxxxxxxxxxxxx>]

** Also affects: nova/victoria
   Importance: Undecided
       Status: New

** Also affects: nova/train
   Importance: Undecided
       Status: New

** Also affects: nova/ussuri
   Importance: Undecided
       Status: New

** Also affects: nova/wallaby
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1939545

Title:
  device_path not saved into bdm.connection_info during
  pre_live_migration

Status in OpenStack Compute (nova):
  Fix Released
Status in OpenStack Compute (nova) train series:
  New
Status in OpenStack Compute (nova) ussuri series:
  New
Status in OpenStack Compute (nova) victoria series:
  New
Status in OpenStack Compute (nova) wallaby series:
  New

Bug description:
  Description
  ===========

  Various block based volume drivers attempt to save a device_path back
  into the stashed connection_info stored within Nova's block device
  mappings *after* connecting a volume to the underlying host. Thanks to
  the indirection caused by the various data structures used between the
  virt and compute layers this isn't actually saved into the underlying
  block device mapping database record during a typical attach flow
  until we get back into the compute and driver block device layer:

  https://github.com/openstack/nova/blob/84b61790763f91e12eebb96d955e2f83abc00d56/nova/virt/block_device.py#L613-L619

  However when an instance is being live migrated these volumes are
  connected as part of pre_live_migration on the destination and no
  attempt is made to save the updates made to the connection_info of the
  volume into the database. This isn't a massive problem as os-brick can
  for the most part lookup the device during future operations but it is
  obviously inefficient.

  This was initially hit in bug #1936439 but that bug is now being used
  to track in a trivial DEBUG log change while this bug will track in
  the underlying fix for the above issue.

  Steps to reproduce
  ==================
  * Attach an iSCSI/FC/NVME etc volume to an instance
  * Live migrate the instance
  * Confirm that device_path isn't present in the connection_info stashed in the bdm

  Expected result
  ===============
  device_path is stashed in the connection_info of the bdm

  Actual result
  =============
  device_path isn't stashed in the connection_info of the bdm

  Environment
  ===========
  1. Exact version of OpenStack you are running. See the following
    list for all releases: http://docs.openstack.org/releases/

  master

  2. Which hypervisor did you use?
     (For example: Libvirt + KVM, Libvirt + XEN, Hyper-V, PowerKVM, ...)
     What's the version of that?

  libvirt

  2. Which storage type did you use?
     (For example: Ceph, LVM, GPFS, ...)
     What's the version of that?

  LVM/iSCSI/FC/NVMe, any block based volume backends.

  3. Which networking type did you use?
     (For example: nova-network, Neutron with OpenVSwitch, ...)

  N/A

  Logs & Configs
  ==============

  See bug #1936439

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