Creating snapshot on NFS backend fails

[Alex Deiter]

Creating a snapshot on the NFS backend fails if the snapshot name is not specified.

Following are the steps to reproduce the issue:

1. Configure a NFS backend for Cinder:

/etc/cinder/cinder.conf:
[DEFAULT]
default_volume_type = nfs
enabled_backends = nfs

[nfs]
volume_driver = cinder.volume.drivers.nfs.NfsDriver
volume_backend_name = nfs
nfs_snapshot_support = True
nas_host = 10.3.35.41
nas_share_path = /volumes/pool1/nas

2. Create a volume:
$ cinder create --volume-type nfs 1

3. Check the volume file:
$ qemu-img info /opt/stack/data/cinder/mnt/0abe5ba79045d7dd179ddc8a4ff1991c/volume-c37c17d9-7657-4f9c-8072-b8af85aeb55e
image: /opt/stack/data/cinder/mnt/0abe5ba79045d7dd179ddc8a4ff1991c/volume-c37c17d9-7657-4f9c-8072-b8af85aeb55e
file format: raw
virtual size: 1.0G (1073741824 bytes)
disk size: 512

3. Try to create a snapshot for the volume:
$ cinder snapshot-create c37c17d9-7657-4f9c-8072-b8af85aeb55e

Expected result:
Snapshot has been successfully created

Actual result:
Snapshot gets has an error state

Cinder volume service log file:

Jul 03 18:15:57 openstack-master-ns5-nfs cinder-volume[115495]: DEBUG cinder.volume.drivers.remotefs [req-b2011f05-d492-4509-b1eb-93562b65297f req-
7de56069-3901-4442-8d72-88753feddf61 admin None] Creating offline snapshot be7de718-87e8-4c17-b71a-83cb56c2ba7c of volume c37c17d9-7657-4f9c-8072-b
8af85aeb55e {{_create_snapshot /opt/stack/cinder/cinder/volume/drivers/remotefs.py:1621}}
...
Jul 03 18:15:58 openstack-master-ns5-nfs cinder-volume[115495]: INFO cinder.message.api [req-b2011f05-d492-4509-b1eb-93562b65297f req-7de56069-3901
-4442-8d72-88753feddf61 admin None] Creating message record for request_id = req-7de56069-3901-4442-8d72-88753feddf61
Jul 03 18:15:58 openstack-master-ns5-nfs cinder-volume[115495]: ERROR oslo_messaging.rpc.server [req-b2011f05-d492-4509-b1eb-93562b65297f req-7de56
069-3901-4442-8d72-88753feddf61 admin None] Exception during message handling: AttributeError: 'NoneType' object has no attribute 'startswith'
...
ERROR oslo_messaging.rpc.server File "/opt/stack/cinder/cinder/volume/drivers/nfs.py", line 576, in create_snapshot
ERROR oslo_messaging.rpc.server return self._create_snapshot(snapshot)
ERROR oslo_messaging.rpc.server File "/opt/stack/cinder/cinder/volume/drivers/remotefs.py", line 1626, in _create_snapshot
ERROR oslo_messaging.rpc.server if snapshot.display_name.startswith('tmp-snap-'):
ERROR oslo_messaging.rpc.server AttributeError: 'NoneType' object has no attribute 'startswith'

Workaround:
Specify a name when creating the snapshot:
$ cinder snapshot-create --name test c37c17d9-7657-4f9c-8072-b8af85aeb55e

Solution:
Parent RemoteFSSnapDriverBase._create_snapshot should check snapshot.display_name property for its value.

proposed patch:
$ git diff
diff --git a/cinder/volume/drivers/remotefs.py b/cinder/volume/drivers/remotefs.py
index 658c25615..ebb197325 100644
--- a/cinder/volume/drivers/remotefs.py
+++ b/cinder/volume/drivers/remotefs.py
@@ -1623,7 +1623,8 @@ class RemoteFSSnapDriverBase(RemoteFSDriver):
         status = snapshot.volume.status

         acceptable_states = ['available', 'in-use', 'backing-up']
- if snapshot.display_name.startswith('tmp-snap-'):
+ if (snapshot.display_name and
+ snapshot.display_name.startswith('tmp-snap-')):
             # This is an internal volume snapshot. In order to support
             # image caching, we'll allow creating/deleting such snapshots
             # while having volumes in 'downloading' state.

Please let me post it on review

Thank you!

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/739277

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/739277
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=11b5c9d97bd69f9e8b5db0d32bfe257063170155
Submitter: Zuul
Branch: master

commit 11b5c9d97bd69f9e8b5db0d32bfe257063170155
Author: Alex Deiter <email address hidden>
Date: Fri Jul 3 18:32:54 2020 +0000

    Creating snapshot on NFS backend fails

    Fixed an issue with creating a snapshot on an NFS backend
    if the snapshot name is not specified.

    Closes-Bug: 1886222
    Change-Id: I33da9c65ef56b3e4967170e3a0fb25f12e067876

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/ussuri
Review: https://review.opendev.org/742581

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/742581
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=f23c7e8f85f3aef368d9ea83a33bdd194efc459c
Submitter: Zuul
Branch: stable/ussuri

commit f23c7e8f85f3aef368d9ea83a33bdd194efc459c
Author: Alex Deiter <email address hidden>
Date: Fri Jul 3 18:32:54 2020 +0000

    Creating snapshot on NFS backend fails

    Fixed an issue with creating a snapshot on an NFS backend
    if the snapshot name is not specified.

    Conflicts:
      cinder/tests/unit/volume/drivers/test_remotefs.py
      Encryption parameter in test method definition

    (cherry picked from commit 11b5c9d97bd69f9e8b5db0d32bfe257063170155)

    Closes-Bug: 1886222
    Change-Id: I33da9c65ef56b3e4967170e3a0fb25f12e067876