Option for using qemu internal iscsi driver

Qemu has a user-space implementation of iscsi,
which can be used instead of the kernel-level one.

By relying only on user-space tooling, we need
less privileges and can run more easily in containerised
environments.

cinder/backup/manager.py

@@ -94,6 +94,7 @@
 CONF = cfg.CONF
 CONF.register_opts(backup_manager_opts)
 CONF.import_opt('use_multipath_for_image_xfer', 'cinder.volume.driver')
+CONF.import_opt('use_qemu_for_image_xfer', 'cinder.volume.driver')
 CONF.import_opt('num_volume_device_scan_tries', 'cinder.volume.driver')
 QUOTAS = quota.QUOTAS
 MAPPING = {
@@ -1098,10 +1099,12 @@ def _connect_device(self, conn):
         use_multipath = CONF.use_multipath_for_image_xfer
         device_scan_attempts = CONF.num_volume_device_scan_tries
         protocol = conn['driver_volume_type']
+        use_qemu = CONF.use_qemu_for_image_xfer
         connector = volume_utils.brick_get_connector(
             protocol,
             use_multipath=use_multipath,
             device_scan_attempts=device_scan_attempts,
+            use_qemu=use_qemu,
             conn=conn,
             expect_raw_disk=True)
         vol_handle = connector.connect_volume(conn['data'])

cinder/image/image_utils.py

@@ -30,6 +30,7 @@
 import os
 import re
 import tempfile
+import time
 
 import cryptography
 from cursive import exception as cursive_exception
@@ -344,19 +345,26 @@ def _convert_image(prefix, source, dest, out_format,
 
     # If there is not enough space on the conversion partition, include
     # the partitions's name in the error message.
-    try:
-        utils.execute(*cmd, run_as_root=run_as_root)
-    except processutils.ProcessExecutionError as ex:
-        if "No space left" in ex.stderr and CONF.image_conversion_dir in dest:
-            conversion_dir = CONF.image_conversion_dir
-            while not os.path.ismount(conversion_dir):
-                conversion_dir = os.path.dirname(conversion_dir)
-
-            message = _("Insufficient free space on %(location)s for image "
-                        "conversion.") % {'location': conversion_dir}
-            LOG.error(message)
-
-        raise
+    max_tries = 3
+    for attempt in range(max_tries):
+        try:
+            utils.execute(*cmd, run_as_root=run_as_root)
+        except processutils.ProcessExecutionError as ex:
+            if "Could not create image" in ex.stderr and attempt < max_tries:
+                LOG.info("Retry %d of %d: %s", attempt, max_tries, ex)
+                time.sleep(3)
+                continue
+
+            if ("No space left" in ex.stderr
+                    and CONF.image_conversion_dir in dest):
+                conversion_dir = CONF.image_conversion_dir
+                while not os.path.ismount(conversion_dir):
+                    conversion_dir = os.path.dirname(conversion_dir)
+
+                message = _("Insufficient free space on %(location)s for image"
+                            " conversion.") % {'location': conversion_dir}
+                LOG.error(message)
+            raise
     duration = timeutils.delta_seconds(start_time, timeutils.utcnow())
 
     # NOTE(jdg): use a default of 1, mostly for unit test, but in

cinder/volume/driver.py

@@ -327,6 +327,13 @@
                      'This parameter needs to be configured for each backend '
                      'section or in [backend_defaults] section as a common '
                      'configuration for all backends.'),
+    cfg.BoolOpt('use_qemu_for_image_xfer',
+                default=False,
+                help='If this is set to True, it will try to use qemu\'s '
+                     'internal block driver.'
+                     'This parameter needs to be configured for each backend '
+                     'section or in [backend_defaults] section as a common '
+                     'configuration for all backends.'),
 ]
 fqdn_opts = [
     cfg.BoolOpt('unique_fqdn_network',
@@ -1132,11 +1139,13 @@ def _connect_device(self, conn):
         # Use Brick's code to do attach/detach
         use_multipath = self.configuration.use_multipath_for_image_xfer
         device_scan_attempts = self.configuration.num_volume_device_scan_tries
+        use_qemu = self.configuration.use_qemu_for_image_xfer
         protocol = conn['driver_volume_type']
         connector = volume_utils.brick_get_connector(
             protocol,
             use_multipath=use_multipath,
             device_scan_attempts=device_scan_attempts,
+            use_qemu=use_qemu,
             conn=conn)
         device = connector.connect_volume(conn['data'])
         host_device = device['path']

cinder/volume/manager.py

@@ -2154,11 +2154,13 @@ def accept_transfer(self, context, volume_id, new_user, new_project,
     def _connect_device(self, conn: dict) -> dict:
         use_multipath = self.configuration.use_multipath_for_image_xfer
         device_scan_attempts = self.configuration.num_volume_device_scan_tries
+        use_qemu = self.configuration.use_qemu_for_image_xfer
         protocol = conn['driver_volume_type']
         connector = volume_utils.brick_get_connector(
             protocol,
             use_multipath=use_multipath,
             device_scan_attempts=device_scan_attempts,
+            use_qemu=use_qemu,
             conn=conn)
         vol_handle = connector.connect_volume(conn['data'])