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

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

[Andre Przywara]

[-- Attachment #1: Type: text/plain, Size: 1309 bytes --]

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@amd.com>

Regards,
Andre.

-- 
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany
Tel: +49 351 448 3567 12
----to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
Geschaeftsfuehrer: Thomas M. McCoy; Giuliano Meroni
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632

[-- Attachment #2: tapdisk_config_file.patch --]
[-- Type: text/x-patch, Size: 833 bytes --]

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'):

[-- Attachment #3: Type: text/plain, Size: 138 bytes --]

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Re: [PATCH] tools: allow config file compatibility with new tap syntax

[Dutch Meyer]

I've seen a couple references to the tap:tapdisk syntax in the last few 
days - For the record, the change responsible for this is 19346.  It's not 
related to the blktap2 code at all.

The point of making this change was to allow folks to specify a 
blktap-like driver using qemu (with the syntax tap:ioemu).

The patch makes sense to me.  I'd be very happy to be able to use the 
older tap:<driver> syntax.

--Dutch

On Tue, 9 Jun 2009, Andre Przywara wrote:

> 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@amd.com>
>
> Regards,
> Andre.
>
> -- 
> Andre Przywara
> AMD-Operating System Research Center (OSRC), Dresden, Germany
> Tel: +49 351 448 3567 12
> ----to satisfy European Law for business letters:
> Advanced Micro Devices GmbH
> Karl-Hammerschmidt-Str. 34, 85609 Dornach b. Muenchen
> Geschaeftsfuehrer: Thomas M. McCoy; Giuliano Meroni
> Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
> Registergericht Muenchen, HRB Nr. 43632
>