Deprecate GlusterFS backup driver

GlusterFS development has effectively ended, GlusterFS
is reaching EOL in Red Hat Storage, and is not being
included in CentOS Stream 10.

Mark it for deprecation with the plan to remove it in
2025.1.

Reference:
https://access.redhat.com/support/policy/updates/rhs

Change-Id: Id06d95128ca601c0a19e1a98060c28f11fa16abe

cinder/backup/drivers/glusterfs.py

@@ -21,6 +21,8 @@ import stat
 from os_brick.remotefs import remotefs as remotefs_brick
 from oslo_concurrency import processutils as putils
 from oslo_config import cfg
+from oslo_log import log as logging
+from oslo_log import versionutils
 
 from cinder.backup.drivers import posix
 from cinder import exception
@@ -38,6 +40,8 @@ glusterfsbackup_service_opts = [
                     'Eg: 1.2.3.4:backup_vol'),
 ]
 
+LOG = logging.getLogger(__name__)
+
 CONF = cfg.CONF
 CONF.register_opts(glusterfsbackup_service_opts)
 
@@ -60,6 +64,12 @@ class GlusterfsBackupDriver(posix.PosixBackupDriver):
 
     def check_for_setup_error(self):
         """Raises error if any required configuration flag is missing."""
+
+        versionutils.report_deprecated_feature(
+            LOG,
+            "The Cinder GlusterFS Backup Driver is deprecated and will be "
+            "removed in the 2025.1 release.")
+
         required_flags = ['glusterfs_backup_share']
         for flag in required_flags:
             val = getattr(CONF, flag, None)

releasenotes/notes/deprecate-glusterfs-backup-drv-5581909c0cc83102.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    The GlusterFS backup driver has been deprecated. It will be removed in
+    the 2025.1 release.