Cinder: Add support to extend attached volumes

While creating an image, if we want to extend the volume
(to accomodate the image), we need to first detach the volume,
perform the extend and attach it again. This is inefficient
for backends that support extending attached volumes since we
are performing 3 cinder operations (the attachment call
includes 3 API calls which sum to a total of 5 API calls for 3
operations) instead of directly extending it which requires only
1 API call to cinder.
The support for extending attached volumes was added in cinder
microversion 3.42.

This patch adds a new boolean config option
``cinder_do_extend_attached`` which allows operators to specify
if the cinder backend they are using supports extending
attached (in-use) volumes. By default this will be ``false``.
Based on the parameter, we will perform the extend operation,
online (if cinder_do_extend_attached is true) and offline otherwise.

Spec: https://review.opendev.org/c/openstack/glance-specs/+/868901

Depends-On: https://review.opendev.org/c/openstack/glance/+/869021
Depends-On: https://review.opendev.org/c/openstack/cinder/+/869051

Change-Id: I5e70824e9abc5277ea25ba95704b358fe3686037

1 files changed, 10 insertions, 0 deletions

diff --git a/releasenotes/notes/cinder-support-extend-in-use-volume-c6292f950ff75cca.yaml b/releasenotes/notes/cinder-support-extend-in-use-volume-c6292f950ff75cca.yaml
new file mode 100644
index 0000000..2b4a748
--- /dev/null
+++ b/releasenotes/notes/cinder-support-extend-in-use-volume-c6292f950ff75cca.yaml
@@ -0,0 +1,10 @@
+---
+features:
+  - |
+    Added support for extending in-use volumes in cinder store.
+    A new boolean config option ``cinder_do_extend_attached`` is
+    added which allows operators to enable/disable extending
+    in-use volume support when creating an image.
+    By default, ``cinder_do_extend_attached`` will be ``False``
+    i.e. old flow of detaching, extending and attaching will be
+    used.