GlusterFS: Synchronize operations that manipulate qcow2 data

Operations that modify qcow2 chains or the GlusterFS driver's
snapshot info file should use locking so that more than one thread
cannot run these operations at the same time.

Without this it is possible for multiple threads to concurrently
modify snapshot information resulting in an incomplete snapshot
chain.

Closes-Bug: #1251425

Change-Id: I93c6ffecd9aec38560cb19085243390b9120b363

diff --git a/cinder/volume/drivers/glusterfs.py b/cinder/volume/drivers/glusterfs.py
index 0987be0373ebfaf7cc2c7647aa832c075d1bed72..7f7497c37ed03b96f8e9799f5a2fc2d72d31de4a 100644 (file)
--- a/cinder/volume/drivers/glusterfs.py
+++ b/cinder/volume/drivers/glusterfs.py
@@ -30,6 +30,7 @@ from cinder import exception
 from cinder.image import image_utils
 from cinder.openstack.common import log as logging
 from cinder import units
+from cinder import utils
 from cinder.volume.drivers import nfs
 
 LOG = logging.getLogger(__name__)
@@ -62,6 +63,10 @@ CONF.import_opt('volume_name_template', 'cinder.db')
 class GlusterfsDriver(nfs.RemoteFsDriver):
     """Gluster based cinder driver. Creates file on Gluster share for using it
     as block device on hypervisor.
+
+    Operations such as create/delete/extend volume/snapshot use locking on a
+    per-process basis to prevent multiple threads from modifying qcow2 chains
+    or the snapshot .info file simultaneously.
     """
 
     driver_volume_type = 'glusterfs'
@@ -187,6 +192,7 @@ class GlusterfsDriver(nfs.RemoteFsDriver):
 
         return {'provider_location': src_vref['provider_location']}
 
+    @utils.synchronized('glusterfs', external=False)
     def create_volume(self, volume):
         """Creates a volume."""
 
@@ -259,6 +265,7 @@ class GlusterfsDriver(nfs.RemoteFsDriver):
                                   path_to_new_vol,
                                   out_format)
 
+    @utils.synchronized('glusterfs', external=False)
     def delete_volume(self, volume):
         """Deletes a logical volume."""
 
@@ -273,6 +280,7 @@ class GlusterfsDriver(nfs.RemoteFsDriver):
 
         self._execute('rm', '-f', mounted_path, run_as_root=True)
 
+    @utils.synchronized('glusterfs', external=False)
     def create_snapshot(self, snapshot):
         """Create a snapshot.
 
@@ -525,6 +533,7 @@ class GlusterfsDriver(nfs.RemoteFsDriver):
         return next(f for f in backing_chain
                     if f.get('backing-filename', '') == snapshot_file)
 
+    @utils.synchronized('glusterfs', external=False)
     def delete_snapshot(self, snapshot):
         """Delete a snapshot.
 
@@ -833,6 +842,7 @@ class GlusterfsDriver(nfs.RemoteFsDriver):
     def validate_connector(self, connector):
         pass
 
+    @utils.synchronized('glusterfs', external=False)
     def initialize_connection(self, volume, connector):
         """Allow connection to connector and return connection info."""
 
@@ -905,6 +915,7 @@ class GlusterfsDriver(nfs.RemoteFsDriver):
             if temp_path is not None:
                 self._execute('rm', '-f', temp_path)
 
+    @utils.synchronized('glusterfs', external=False)
     def extend_volume(self, volume, size_gb):
         volume_path = self.local_path(volume)
         volume_filename = os.path.basename(volume_path)