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Re: [Xen-devel] blktap2: need more than 3 values to unpack

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Dutch Meyer <dmeyer@xxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] blktap2: need more than 3 values to unpack
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Tue, 02 Jun 2009 23:44:35 +0100
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Thread-topic: [Xen-devel] blktap2: need more than 3 values to unpack
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Probably you had an old .config hanging around in your build tree somewhere.
c/s 889 should fix this for a fresh build.

 -- Keir

On 02/06/2009 18:33, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> Thanks.  Looks like a partial configuration patch got checked
> in for blktap2 (cs 886)?  CONFIG_XEN_BLKDEV_TAP2 must be configured
> but afaict is not turned on by default (yet?).  So a fresh
> xen-unstable tip doesn't build the blktap2 driver.  See:
> 
> http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/3e01555dd227
> 
> (I'm guessing since this was submitted by Isaku that blktap2
> shouldn't be the default on ia64?)
> 
> Should CONFIG_XEN_BLKDEV_TAP2 be turned on by default, instead
> of CONFIG_XEN_BLKDEV_TAP, at least on x86?
> 
> I tried modifying
> 
> linux-2.6.18-xen.hg/buildconfigs/linux-defconfig_xen0_x86_32
> 
> (and also
> 
> linux-2.6.18-xen.hg/buildconfigs/linux-defconfig_xen_x86_32)
> 
> followed by:
> 
> KERNELS=linux-2.6-xen0 make linux-2.6-xen-config CONFIGMODE=oldconfig
> 
> (I don't need or want to go through a manual config process)
> 
> but BLKDEV_TAP is always selected, not BLKDEV_TAP2.
> 
> Finally, I resorted to manually changing
> 
> linux-2.6.18-xen.hg/drivers/xen/Kconfig
> 
> and this succeeds in turning it on, but it just reverses the
> above checked-in patch, so I suspect that's not the right
> answer either.
> 
>> -----Original Message-----
>> From: Dutch Meyer [mailto:dmeyer@xxxxxxxxx]
>> Sent: Tuesday, June 02, 2009 9:05 AM
>> To: Dan Magenheimer
>> Subject: RE: [Xen-devel] blktap2: need more than 3 values to unpack
>> 
>> 
>> I think that you don't have the blktap2 driver loaded in
>> dom0.  A clean 
>> build/install of the dom0 kernel image should sort you out.  If
>> drivers/xen/blktap2 is compiled in it should be setting up
>> these paths.
>> 
>> Let me know if that fixes things and I'll make python spit out more
>> meaningful errors, otherwise we can try to figure out the
>> blktap2 kernel 
>> code isn't working.
>> 
>> --Dutch
>> 
>> On Tue, 2 Jun 2009, Dan Magenheimer wrote:
>> 
>>> It replies with "didn't find blktap-control in /proc/misc"
>>> 
>>> If that fails, perhaps the path doesn't exist, but I looked
>>> and /sys/class/blktap2 doesn't exist.
>>> 
>>>> -----Original Message-----
>>>> From: Dutch Meyer [mailto:dmeyer@xxxxxxxxx]
>>>> Sent: Monday, June 01, 2009 10:37 PM
>>>> To: Dan Magenheimer
>>>> Subject: RE: [Xen-devel] blktap2: need more than 3 values to unpack
>>>> 
>>>> 
>>>> Can you try this from the command line:
>>>> 
>>>>      tapdisk2 -n aio:/pathto/file.img
>>>> 
>>>> If successful, this will create your aio device and print a
>>>> /dev device
>>>> associated with it.
>>>> 
>>>> In that case you'll then be able to remove it with:
>>>> 
>>>>      echo 1 > /sys/class/blktap2/<disk>/remove
>>>> 
>>>> Where <disk> will be obvious from the output of the
>> tapdisk2 command.
>>>> 
>>>> However, I expect that this will fail.
>>>> 
>>>> --Dutch
>>>> 
>>>> On Mon, 1 Jun 2009, Dan Magenheimer wrote:
>>>> 
>>>>>> Then I might be able to help, but I'm not sure how to
>>>>>> reproduce it.  If
>>>>>> you send a log file and config for this latter error I'll
>>>>>> take a look.
>>>>> 
>>>>> Here ya go.
>>>>> 
>>>>> Thanks,
>>>>> Dan
>>>>> 
>>>>>> -----Original Message-----
>>>>>> From: Dutch Meyer [mailto:dmeyer@xxxxxxxxx]
>>>>>> Sent: Monday, June 01, 2009 8:32 PM
>>>>>> To: Dan Magenheimer
>>>>>> Cc: Xen-Devel (E-mail)
>>>>>> Subject: Re: [Xen-devel] blktap2: need more than 3
>> values to unpack
>>>>>> 
>>>>>> 
>>>>>> The tap:aio:/pathto/file.img syntax that you're using in your
>>>>>> config was
>>>>>> changed before blktap2 was introduced.
>>>>>> tap:tapdisk:aio:/pathto/file.img is
>>>>>> apparently the correct syntax now, though the README didn't
>>>>>> get updated to
>>>>>> reflect this.  Our blktap2 documentation is no better -
>> I'll try to
>>>>>> remedy that this week.
>>>>>> 
>>>>>> 
>>>>>> If you're still seeing this error:
>>>>>>     "Error: 'file' object has no attribute 'find'"
>>>>>> 
>>>>>> Then I might be able to help, but I'm not sure how to
>>>>>> reproduce it.  If
>>>>>> you send a log file and config for this latter error I'll
>>>>>> take a look.
>>>>>> Yang seems to be reporting the same thing in another thread.
>>>>>> 
>>>>>> --Dutch
>>>>>> 
>>>>>> On Mon, 1 Jun 2009, Dan Magenheimer wrote:
>>>>>> 
>>>>>>> Hmmm... trying blktap2 for the first time, using 19682.
>>>>>>> I had thought that the syntax hadn't changed, but I am
>>>>>>> getting what appears to be a parsing error on my vbd line.
>>>>>>> 
>>>>>>> "ValueError: need more than 3 values to unpack"
>>>>>>> 
>>>>>>> Thinking maybe that "w!" was the culprit, I changed
>>>>>>> it to "w" with no change in result.
>>>>>>> 
>>>>>>> Looking at the python code that generated the error,
>>>>>>> I tried to figure out the syntax by experimentation
>>>>>>> but without luck.  I tried:
>>>>>>> 
>>>>>>> tap:tapdisk:aio:/pathto/file.img
>>>>>>> 
>>>>>>> but got "Error: 'file' object has no attribute 'find'"
>>>>>>> 
>>>>>>> To see if I could use the old blktap, I tried
>>>>>>> 
>>>>>>> tap:tapdisk:ioemu:/pathto/file.img
>>>>>>> 
>>>>>>> but got the dreaded "Error: Device 768 (tap) could not be
>>>>>>> connected. Hotplug scripts not working"
>>>>>>> 
>>>>>>> Am I missing something in the syntax for blktap2?
>>>>>>> Is there a how-to or readme I didn't find?  Or
>>>>>>> is there some required dependency I don't know about
>>>>>>> that is missing?
>>>>>>> 
>>>>>>> I thought maybe I had a bad install, so rebuilt and
>>>>>>> reinstalled with the same result.
>>>>>>> 
>>>>>>> xend.log and config file attached.
>>>>>>> 
>>>>>>> Thanks,
>>>>>>> Dan
>>>>>>> 
>>>>>>> P.S. I am trying blktap2 because both blktap and
>>>>>>> file-backed fail.  Blktap sometimes reads garbage
>>>>>>> from the file and
>>>>>> 
>>>>>> _______________________________________________
>>>>>> Xen-devel mailing list
>>>>>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>>>>>> http://lists.xensource.com/xen-devel
>>>>>> 
>>>> 
>>> 
>> 
> 
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