Allow for specifying nfs mount options

Fixes bug 1113042

Adds a new config option:
    nfs_mount_options=None (Default)

When not None, anything set here will be passed as -o <options> to
the mount command. The default behavior is to do exactly as we are
doing today and relying on the OS/kernel defaults.

Change-Id: I6bd27f9d0e8848a9ba98318ba7288e43ee6b4cb9
Flags: DocImpact

cinder/volume/drivers/nfs.py

@@ -41,7 +41,12 @@ volume_opts = [
                 default=True,
                 help=('Create volumes as sparsed files which take no space.'
                       'If set to False volume is created as regular file.'
-                      'In such case volume creation takes a lot of time.'))]
+                      'In such case volume creation takes a lot of time.')),
+    cfg.StrOpt('nfs_mount_options',
+               default=None,
+               help='Mount options passed to the nfs client. See section '
+                    'of the nfs man page for details'),
+]
 
 FLAGS = flags.FLAGS
 FLAGS.register_opts(volume_opts)
@@ -270,9 +275,14 @@ class NfsDriver(driver.VolumeDriver):
         if not self._path_exists(mount_path):
             self._execute('mkdir', '-p', mount_path)
 
+        # Construct the NFS mount command.
+        nfs_cmd = ['mount', '-t', 'nfs']
+        if FLAGS.nfs_mount_options is not None:
+            nfs_cmd.extend(['-o', FLAGS.nfs_mount_options])
+        nfs_cmd.extend([nfs_share, mount_path])
+
         try:
-            self._execute('mount', '-t', 'nfs', nfs_share, mount_path,
-                          run_as_root=True)
+            self._execute(*nfs_cmd, run_as_root=True)
         except exception.ProcessExecutionError as exc:
             if ensure and 'already mounted' in exc.stderr:
                 LOG.warn(_("%s is already mounted"), nfs_share)

etc/cinder/cinder.conf.sample

@@ -882,6 +882,11 @@
 # volume creation takes a lot of time. (boolean value)
 #nfs_sparsed_volumes=true
 
+# Mount options passed to the nfs client (string value)
+# The value set here is passed directly to the -o flag
+# of the mount command. See the nfs man page for details.
+#nfs_mount_options=None
+
 
 #
 # Options defined in cinder.volume.drivers.rbd