Detaching encryptors from volumes that are still attached to domains can result in failure

[Lee Yarwood]

Description
===========
Detaching encryptors from volumes that are still attached to domains can result in failure.

Steps to reproduce
==================
- Attach an encrypted volume to an instance.
- Mount and use the volume within the instance.
- Attempt to detach the volume via Nova while the volume is in-use within the instance.

Expected result
===============
The volume is detached.

Actual result
=============
Nova first attempts to detach the encryptors from the volume that is still attached to the libvirt domain. As a result this can fail with `Device or resource busy` as I/O is still in-flight between the instance and volume.

Environment
===========
1. master, stable/newton.

2. Which hypervisor did you use?
   Libvirt + KVM

2. Which storage type did you use?
   LVM / iSCSI + LUKS

3. Which networking type did you use?
   N/A

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

Failed to detach an encrypted volume
https://bugzilla.redhat.com/show_bug.cgi?id=1388417

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/398479
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=d55c5136d0f7ece722db889a4375133e827411c0
Submitter: Jenkins
Branch: master

commit d55c5136d0f7ece722db889a4375133e827411c0
Author: Lee Yarwood <email address hidden>
Date: Wed Nov 16 15:51:02 2016 +0000

    libvirt: Detach volumes from a domain before detaching any encryptors

    I983f80822a5 introduced retry logic around the detaching of volumes from
    a libvirt domain. However it also reordered the surrounding code so that
    we attempt to detach any encryptors from a volume first while the volume
    is still attached to the domain. This can lead to `Device or resource
    busy` errors if the volume is still being used by the instance when we
    attempt to detach the encryptors.

    Closes-bug: #1642628
    Change-Id: Ia0f8e725ec8a0fbc44bd4592b021dea978cf4e4f

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/newton
Review: https://review.openstack.org/412201

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/412201
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=7a7bbb6da25462737e755d6aa2845e395d60570b
Submitter: Jenkins
Branch: stable/newton

commit 7a7bbb6da25462737e755d6aa2845e395d60570b
Author: Lee Yarwood <email address hidden>
Date: Wed Nov 16 15:51:02 2016 +0000

    libvirt: Detach volumes from a domain before detaching any encryptors

    I983f80822a5 introduced retry logic around the detaching of volumes from
    a libvirt domain. However it also reordered the surrounding code so that
    we attempt to detach any encryptors from a volume first while the volume
    is still attached to the domain. This can lead to `Device or resource
    busy` errors if the volume is still being used by the instance when we
    attempt to detach the encryptors.

    Closes-bug: #1642628
    Change-Id: Ia0f8e725ec8a0fbc44bd4592b021dea978cf4e4f
    (cherry picked from commit d55c5136d0f7ece722db889a4375133e827411c0)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 15.0.0.0b3 development milestone.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 14.0.4 release.