[Xen-devel] [PATCH] tools: allow config file compatibility with new tap syntax

[Andre Przywara <andre.przywara@xxxxxxx>]

Hi,

recently the format of the tap syntax in the config file changed to 
using a 4 part specifier (tap:tapdisk:<format>:<filename>) instead of 
the old 3-part one (tap:<qcow>:<filename>).
This breaks compatibility with existing config files, a guest start will 
throw a Python exception and will be aborted.
AFAICS currently tap:tapdisk is redundant, so the attached patch simply 
catches the above mentioned exception and tries to parse the old format 
in this case.
This will help our test work flow, because we can use the same config 
file for different Xen tools versions.
What is the purpose of the new :tapdisk: specifier? Is it really 
redundant (at least currently)?
Please cry out if there is something that I have missed, otherwise 
please apply the patch.
If applying this patch is not an option, I would opt for a better error 
message.
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>

Regards,
Andre.

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448 3567 12
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Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
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diff -r aef9bba654f1 tools/python/xen/xend/server/BlktapController.py
--- a/tools/python/xen/xend/server/BlktapController.py  Wed Jun 03 00:29:31 
2009 +0200
+++ b/tools/python/xen/xend/server/BlktapController.py  Mon Jun 08 10:16:33 
2009 +0200
@@ -120,8 +120,12 @@
 
     def createDevice(self, config):
 
-        uname = config.get('uname', '')        
-        (typ, subtyp, params, file) = string.split(uname, ':', 3)
+        uname = config.get('uname', '')
+        try:
+            (typ, subtyp, params, file) = string.split(uname, ':', 3)
+        except:
+            (typ, params, file) = string.split(uname, ':', 2)
+            subtyp = 'tapdisk'
         if typ in ('tap'):
             if subtyp in ('tapdisk'):                                          
                 if params in ('ioemu', 'qcow2', 'vmdk', 'sync'):

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