Xen devel - Feb 2011 - [PATCH] Remus: support both tap and tap2 style disk specs

# HG changeset patch
# User Shriram Rajagopalan <rshriram@cs.ubc.ca>
# Date 1297922415 28800
# Node ID 0ee537d24ca0fb0e5e74438f1375a7a7d9dc13b5
# Parent  137ad33475048abce15d82a7499cf211f0c28c85
Remus: support both tap and tap2 style disk specs

Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>

diff -r 137ad3347504 -r 0ee537d24ca0 tools/python/xen/remus/device.py
--- a/tools/python/xen/remus/device.py	Mon Feb 14 17:02:55 2011 +0000
+++ b/tools/python/xen/remus/device.py	Wed Feb 16 22:00:15 2011 -0800
@@ -36,10 +36,11 @@
         # to request commits.
         self.ctlfd = None
 
-        if not disk.uname.startswith(''tap:remus:'') and not
disk.uname.startswith(''tap:tapdisk:remus:''):
+        disktype = re.match("tap2?:.*(remus.*)\|", disk.uname)
+        if disktype == None:
             raise ReplicatedDiskException(''Disk is not replicated:
%s'' %
                                         str(disk))
-        fifo = re.match("tap:.*(remus.*)\|",
disk.uname).group(1).replace('':'', ''_'')
+        fifo = disktype.group(1).replace('':'',
''_'')
         absfifo = os.path.join(self.FIFODIR, fifo)
         absmsgfifo = absfifo + ''.msg''
 

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Shriram Rajagopalan writes ("[Xen-devel] [PATCH] Remus: support both tap
and tap2 style disk specs"):
> Remus: support both tap and tap2 style disk specs
Thanks for this, but: where can I find documented what this disk spec
string is supposed to look like ?  Ought this to be in
docs/misc/xl-disk-configuration.txt ?
> -        if not disk.uname.startswith(''tap:remus:'') and
not disk.uname.startswith(''tap:tapdisk:remus:''):
> +        disktype = re.match("tap2?:.*(remus.*)\|", disk.uname)
> +        if disktype == None:
This seems quite a striking change.  What is the tap2 remus syntax
like ?

Ian.

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On Thu, Feb 17, 2011 at 11:04 AM, Ian Jackson <Ian.Jackson@eu.citrix.com>
wrote:
> Shriram Rajagopalan writes ("[Xen-devel] [PATCH] Remus: support both
tap and tap2 style disk specs"):
>> Remus: support both tap and tap2 style disk specs
>
> Thanks for this, but: where can I find documented what this disk spec
> string is supposed to look like ?  Ought this to be in
> docs/misc/xl-disk-configuration.txt ?
>
>> -        if not disk.uname.startswith(''tap:remus:'')
and not disk.uname.startswith(''tap:tapdisk:remus:''):
>> +        disktype = re.match("tap2?:.*(remus.*)\|",
disk.uname)
>> +        if disktype == None:
>
> This seems quite a striking change.  What is the tap2 remus syntax
> like ?
>
There is no change in remus syntax.
remus part of the disk spec just requires "remus:BackupHost:Port|" to
immediately follow major driver name. so,

 disk= tap2:remus:BackupHost:Port|aio:volname ...

the problem is with the initial prefix "tap2:" string.
Which could be tap: or tap2: or tap:tapdisk or tap2:tapdisk based on
http://wiki.xensource.com/xenwiki/blktap2

Though as i noted in an earlier email, libxl doesnt accept tap2 while xend
accepts tap2.

shriram
> Ian.
>
>
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Shriram Rajagopalan writes ("Re: [Xen-devel] [PATCH] Remus: support both
tap and tap2 style disk specs"):
> On Thu, Feb 17, 2011 at 11:04 AM, Ian Jackson
<Ian.Jackson@eu.citrix.com> wrote:
> > Shriram Rajagopalan writes ("[Xen-devel] [PATCH] Remus: support
both tap and tap2 style disk specs"):
> >> -        if not
disk.uname.startswith(''tap:remus:'') and not
disk.uname.startswith(''tap:tapdisk:remus:''):
> >> +        disktype = re.match("tap2?:.*(remus.*)\|",
disk.uname)
> >> +        if disktype == None:
> >
> > This seems quite a striking change.  What is the tap2 remus syntax
> > like ?
> >
> There is no change in remus syntax.
> remus part of the disk spec just requires
"remus:BackupHost:Port|" to
> immediately follow major driver name. so,
> 
>  disk= tap2:remus:BackupHost:Port|aio:volname ...
Your regexp would match
  tap2:aio:file:/path/containing/remus/and/with/a/pipe/symbol|
> the problem is with the initial prefix "tap2:" string.
> Which could be tap: or tap2: or tap:tapdisk or tap2:tapdisk based on
> http://wiki.xensource.com/xenwiki/blktap2
Yes, this is very unpleasant.  But at the very least I think you
should be somewhat more careful and at least expect the thing you eat
at the front not to contain slashes.
> Though as i noted in an earlier email, libxl doesnt accept tap2 while xend
> accepts tap2.
We have fixed that very recently - in the last day or two.

Ian.

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On 2011-02-18, at 4:23 AM, Ian Jackson <Ian.Jackson@eu.citrix.com> wrote:
> Shriram Rajagopalan writes ("Re: [Xen-devel] [PATCH] Remus: support
both tap and tap2 style disk specs"):
>> On Thu, Feb 17, 2011 at 11:04 AM, Ian Jackson
<Ian.Jackson@eu.citrix.com> wrote:
>>> Shriram Rajagopalan writes ("[Xen-devel] [PATCH] Remus:
support both tap and tap2 style disk specs"):
>>>> -        if not
disk.uname.startswith(''tap:remus:'') and not
disk.uname.startswith(''tap:tapdisk:remus:''):
>>>> +        disktype = re.match("tap2?:.*(remus.*)\|",
disk.uname)
>>>> +        if disktype == None:
>>> 
>>> This seems quite a striking change.  What is the tap2 remus syntax
>>> like ?
>>> 
>> There is no change in remus syntax.
>> remus part of the disk spec just requires
"remus:BackupHost:Port|" to
>> immediately follow major driver name. so,
>> 
>> disk= tap2:remus:BackupHost:Port|aio:volname ...
> 
> Your regexp would match
>  tap2:aio:file:/path/containing/remus/and/with/a/pipe/symbol|
> 
>> the problem is with the initial prefix "tap2:" string.
>> Which could be tap: or tap2: or tap:tapdisk or tap2:tapdisk based on
>> http://wiki.xensource.com/xenwiki/blktap2
> 
> Yes, this is very unpleasant.  But at the very least I think you
> should be somewhat more careful and at least expect the thing you eat
> at the front not to contain slashes.
> 
>> Though as i noted in an earlier email, libxl doesnt accept tap2 while
xend
>> accepts tap2.
> 
> We have fixed that very recently - in the last day or two.
> 
If that''s the case, the patch could be really simple. Will send out
another patch soon.
Shriram
> Ian.
> 
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