if we firstly create a incremental backup without parent backup， the reserved value of quota_usages table is not rollbacked

[Leopard Ma]

You can use the following steps to reproduce：
1 cinder create --name test 1
+--------------------------------+--------------------------------------+
| Property | Value |
+--------------------------------+--------------------------------------+
| attachments | [] |
| availability_zone | nova |
| bootable | false |
| consistencygroup_id | None |
| created_at | 2018-12-12T03:04:00.000000 |
| description | None |
| encrypted | False |
| id | 2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61 |
| metadata | {} |
| migration_status | None |
| multiattach | False |
| name | test |
| os-vol-host-attr:host | node01@lvmdriver-1#lvmdriver-1 |
| os-vol-mig-status-attr:migstat | None |
| os-vol-mig-status-attr:name_id | None |
| os-vol-tenant-attr:tenant_id | 3521efd8be6f43f09e65a05abd32fbbe |
| replication_status | None |
| size | 1 |
| snapshot_id | None |
| source_volid | None |
| status | creating |
| updated_at | 2018-12-12T03:04:00.000000 |
| user_id | 1dc213c4fbea4c82b69036d444c20fac |
| volume_type | lvmdriver-1 |
+--------------------------------+--------------------------------------+
2 cinder show 2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61
+--------------------------------+--------------------------------------+
| Property | Value |
+--------------------------------+--------------------------------------+
| attached_servers | [] |
| attachment_ids | [] |
| availability_zone | nova |
| bootable | false |
| consistencygroup_id | None |
| created_at | 2018-12-12T03:04:00.000000 |
| description | None |
| encrypted | False |
| id | 2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61 |
| metadata | |
| migration_status | None |
| multiattach | False |
| name | test |
| os-vol-host-attr:host | node01@lvmdriver-1#lvmdriver-1 |
| os-vol-mig-status-attr:migstat | None |
| os-vol-mig-status-attr:name_id | None |
| os-vol-tenant-attr:tenant_id | 3521efd8be6f43f09e65a05abd32fbbe |
| replication_status | None |
| size | 1 |
| snapshot_id | None |
| source_volid | None |
| status | available |
| updated_at | 2018-12-12T03:04:01.000000 |
| user_id | 1dc213c4fbea4c82b69036d444c20fac |
| volume_type | lvmdriver-1 |
+--------------------------------+--------------------------------------+
3 cinder quota-usage 3521efd8be6f43f09e65a05abd32fbbe
+-----------------------+--------+----------+-------+-----------+
| Type | In_use | Reserved | Limit | Allocated |
+-----------------------+--------+----------+-------+-----------+
| backup_gigabytes | 0 | 0 | 1000 | |
| backups | 0 | 0 | 10 | |
| gigabytes | 2 | 0 | 1000 | |
| gigabytes_lvmdriver-1 | 2 | 0 | -1 | |
| groups | 0 | 0 | 10 | |
| per_volume_gigabytes | 0 | 0 | -1 | |
| snapshots | 0 | 0 | 10 | |
| snapshots_lvmdriver-1 | 0 | 0 | -1 | |
| volumes | 2 | 0 | 10 | |
| volumes_lvmdriver-1 | 2 | 0 | -1 | |
+-----------------------+--------+----------+-------+-----------+
4 cinder backup-create 2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61 --incremental
ERROR: Invalid backup: No backups available to do an incremental backup. (HTTP 400) (Request-ID: req-335eb1e6-ac70-45a7-b084-764e4470b1ce)
5 cinder quota-usage 3521efd8be6f43f09e65a05abd32fbbe
+-----------------------+--------+----------+-------+-----------+
| Type | In_use | Reserved | Limit | Allocated |
+-----------------------+--------+----------+-------+-----------+
| backup_gigabytes | 0 | 1 | 1000 | |
| backups | 0 | 1 | 10 | |
| gigabytes | 2 | 0 | 1000 | |
| gigabytes_lvmdriver-1 | 2 | 0 | -1 | |
| groups | 0 | 0 | 10 | |
| per_volume_gigabytes | 0 | 0 | -1 | |
| snapshots | 0 | 0 | 10 | |
| snapshots_lvmdriver-1 | 0 | 0 | -1 | |
| volumes | 2 | 0 | 10 | |
| volumes_lvmdriver-1 | 2 | 0 | -1 | |
+-----------------------+--------+----------+-------+-----------+
5 Repetitive operation step 4 for nine times:
  cinder backup-create 2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61 --incremental
6 cinder backup-create 2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61
ERROR: BackupLimitExceeded: Maximum number of backups allowed (10) exceeded (HTTP 413) (Request-ID: req-cf3f4cfc-521e-4115-bbe8-14a031e45718)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/626790

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/626790
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=a62fabfa65bf02ab91ff61ad2b74a6eb7509ee24
Submitter: Zuul
Branch: master

commit a62fabfa65bf02ab91ff61ad2b74a6eb7509ee24
Author: LeopardMa <email address hidden>
Date: Thu Dec 20 20:24:34 2018 -0500

    Rollback the quota_usages table when failed to create a incremental backup

    If we firstly create a incremental backup without parent backup
    or using unavailable backup file, like execute the command:
    ``cinder backup-create --name test_backup --incremental
    2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61``.

    To satisfy one of the above reasons, we will be received an error
    info: "Invalid backup: No backups available to do an incremental
    backup. (HTTP 400)". But the reserved value of the ``quota_usages``
    table has been updated, so we need to roll back the ``quota_usages``
    table. Otherwise, after repetitive operation for many times,
    create backup will be failed.

    Co-Authored-By: Brin Zhang <email address hidden>

    Closes-Bug: #1809323
    Change-Id: I1870633a5505bdb60d529fbda3147378b75e2b07

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 15.0.0.0rc1 release candidate.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/stein
Review: https://review.opendev.org/739606

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/739606
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=ef07bc95471101e42d531908a00c242710834784
Submitter: Zuul
Branch: stable/stein

commit ef07bc95471101e42d531908a00c242710834784
Author: LeopardMa <email address hidden>
Date: Thu Dec 20 20:24:34 2018 -0500

    Rollback the quota_usages table when failed to create a incremental backup

    If we firstly create a incremental backup without parent backup
    or using unavailable backup file, like execute the command:
    ``cinder backup-create --name test_backup --incremental
    2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61``.

    To satisfy one of the above reasons, we will be received an error
    info: "Invalid backup: No backups available to do an incremental
    backup. (HTTP 400)". But the reserved value of the ``quota_usages``
    table has been updated, so we need to roll back the ``quota_usages``
    table. Otherwise, after repetitive operation for many times,
    create backup will be failed.

    Co-Authored-By: Brin Zhang <email address hidden>

    Closes-Bug: #1809323
    Change-Id: I1870633a5505bdb60d529fbda3147378b75e2b07
    (cherry picked from commit a62fabfa65bf02ab91ff61ad2b74a6eb7509ee24)

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/rocky
Review: https://review.opendev.org/742220

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/742220
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=29d956c0cee09465730f304cee7cc69dd137f2be
Submitter: Zuul
Branch: stable/rocky

commit 29d956c0cee09465730f304cee7cc69dd137f2be
Author: LeopardMa <email address hidden>
Date: Thu Dec 20 20:24:34 2018 -0500

    Rollback the quota_usages table when failed to create a incremental backup

    If we firstly create a incremental backup without parent backup
    or using unavailable backup file, like execute the command:
    ``cinder backup-create --name test_backup --incremental
    2e3d9d0b-6b33-4cfe-a7c2-656415ee6f61``.

    To satisfy one of the above reasons, we will be received an error
    info: "Invalid backup: No backups available to do an incremental
    backup. (HTTP 400)". But the reserved value of the ``quota_usages``
    table has been updated, so we need to roll back the ``quota_usages``
    table. Otherwise, after repetitive operation for many times,
    create backup will be failed.

    Co-Authored-By: Brin Zhang <email address hidden>

    Closes-Bug: #1809323
    Change-Id: I1870633a5505bdb60d529fbda3147378b75e2b07
    (cherry picked from commit a62fabfa65bf02ab91ff61ad2b74a6eb7509ee24)
    (cherry picked from commit ef07bc95471101e42d531908a00c242710834784)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder rocky-eol release.