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Re: [Xen-users] tap:aio not working...

To: <xen-users@xxxxxxxxxxxxxxxxxxx>, "Kevin Wolf" <kwolf@xxxxxxx>
Subject: Re: [Xen-users] tap:aio not working...
From: "Nick Couchman" <Nick.Couchman@xxxxxxxxx>
Date: Wed, 30 Apr 2008 10:58:27 -0600
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Well, here's the output from lsmod and ps:

xen02:~ # lsmod | grep -i tap
blktap                121604  2 [permanent]
xenbus_be               8832  3 netbk,blkbk,blktap
xen02:~ # ps -ef | grep blk
root      7060     1  0 Apr28 ?        00:00:00 blktapctrl
root     31500 31466  0 06:59 pts/0    00:00:00 grep blk

Clearly the blktap module is loaded (is there another one I need??) and the 
control daemon is running.  The only messages that I get with BLKTAP or TAPDISK 
occur when I manually do an "xm block-attach" to dom0 to test out the tap:aio 
method.  If I try to start a domU with tap:aio, the only log file messages I 
get are these:

Apr 30 07:01:57 xen02 kernel: blkback: ring-ref 8, event-channel 38, protocol 1 
Apr 30 07:01:57 xen02 kernel: blkback: ring-ref 8, event-channel 38, protocol 1 
Apr 30 07:01:57 xen02 logger: /etc/xen/scripts/block: add 

Maybe the /etc/xen/scripts/block script is not handling the tap:aio stuff 
correctly, since that's the last message?  Or maybe something else is failing 
to occur.


>>> On Wed, Apr 30, 2008 at  5:58 AM, Kevin Wolf <kwolf@xxxxxxx> wrote:

Nick Couchman schrieb:
> I'm running SLES10 SP1 and have been using file:/ for my file-backed domUs.  
> The domUs sit on a shared OCFS2 SAN-backed filesystem and are run on my three 
> or four XEN servers.  I'm having issues with the loopback devices not being 
> released when the domUs shutdown or migrate, so I decided to switch over to 
> tap:aio for my file-backed domUs.  This isn't working, either.  Whereas the 
> domUs with file: at least boot and run, the domUs with tap:aio: fail with 
> this error:
> syslog messages are unhelpful - here's the output when I try with tap:aio:
> Apr 29 16:55:02 xen02 kernel: blkback: ring-ref 8, event-channel 38, protocol 
> 1 (x86_64-abi)
> Apr 29 16:55:02 xen02 kernel: blkback: ring-ref 8, event-channel 38, protocol 
> 1 (x86_64-abi)
> Apr 29 16:55:02 xen02 logger: /etc/xen/scripts/block: add 
> XENBUS_PATH=backend/vbd/0/51952
> Apr 29 16:56:42 xen02 logger: /etc/xen/scripts/block: remove 
> XENBUS_PATH=backend/vbd/0/51952
> Apr 29 16:56:43 xen02 logger: /etc/xen/scripts/xen-hotplug-cleanup: 
> XENBUS_PATH=backend/vbd/0/51952
> Anyone have any hints as to what might be going on here?  Any possible 
> solutions?

You should have some BLKTAPCTRL and TAPDISK lines in your
/var/log/messages which could give you some hints. If these lines are
missing you most probably don't have loaded the kernel modules (they
aren't loaded by default, IIRC) or blktapctrl isn't running.


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