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[OpenStack Infra <1937375@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.opendev.org/c/openstack/nova/+/801990
Committed: https://opendev.org/openstack/nova/commit/2209b0007fe85d7c5439e0bfdfe2120c63898fa2
Submitter: "Zuul (22348)"
Branch:    master

commit 2209b0007fe85d7c5439e0bfdfe2120c63898fa2
Author: Felix Huettner <felix.huettner@mail.schwarz>
Date:   Fri Jul 23 10:43:32 2021 +0200

    compute: Avoid duplicate BDMs during reserve_block_device_name
    
    When attaching a volume to a running instance the nova-api validates
    that the volume is not already attached to the instance. However
    nova-compute is responsible for actually creating the BDM entry in the
    database. If sending attach requests fast enough it can be possible
    that the same "attach_volume" request can be sent to nova-compute for
    the same volume/instance combination.
    
    To work around this we add a check in nova-compute to validate that
    the volume has not been attached in the mean time.
    
    Closes-Bug: #1937375
    Change-Id: I92f35514efddcb071c7094370b79d91d34c5bc72


** Changed in: nova
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1937375

Title:
  Duplicate BlockDeviceMapping if attaching volumes too fast

Status in OpenStack Compute (nova):
  Fix Released

Bug description:
  Description
  ===========
  When attaching a volume to a running instance the nova-api validates that
  the volume is not already attached to the instance. However nova-compute
  is responsible for actually creating the BDM entry in the database.
  If sending attach requests fast enough it can be possible that the same
  "attach_volume" request can be sent to nova-compute for the same
  volume/instance combination.

  Steps to reproduce
  ==================
  * Create an Instance and a volume
  * run in 2 terminals in parallel "openstack server add volume <instance> <volume>"
  * when being fast enough this results in "openstack server show" to report the volume id twice

  Expected result
  ===============
  The volume is attached to the instance just once

  Actual result
  =============
  The volume is attached to the instance two (or with more parallelity) or more times.

  Environment
  ===========
  1. Happens on master till queens (possibly also earlier releases)

  2. Which hypervisor did you use?
     Indepentent of Hypervisor, observed with Libvirt

  2. Which storage type did you use?
     Independent of Storage, observed with ceph + nfs

  3. Which networking type did you use?
     Independent of Network, observed with ovs

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