CA-136654: Don't rely on a XAPI session existing

With static VDIs, the SR code is run without a XAPI session.  In this
case, set O_DIRECT to be on for safety since there is external knob to
adjust it.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reviewed-by: Thanos Makatos <thanos.makatos@citrix.com>

GitHub: closes #142 on xapi-project/sm

drivers/FileSR.py

@@ -76,9 +76,12 @@ def handles(srtype):
     handles = staticmethod(handles)
 
     def _check_o_direct(self):
-        other_config = self.session.xenapi.SR.get_other_config(self.sr_ref)
-        o_direct = other_config.get("o_direct")
-        self.o_direct = o_direct is not None and o_direct == "true"
+        if self.sr_ref and self.session is not None:
+            other_config = self.session.xenapi.SR.get_other_config(self.sr_ref)
+            o_direct = other_config.get("o_direct")
+            self.o_direct = o_direct is not None and o_direct == "true"
+        else:
+            self.o_direct = True
 
     def load(self, sr_uuid):
         self.ops_exclusive = OPS_EXCLUSIVE