WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] BLKTAPCTRL[2375]: blktapctrl_linux.c:86: blktap0 open fa

To: Dante Cinco <dantecinco@xxxxxxxxx>
Subject: Re: [Xen-devel] BLKTAPCTRL[2375]: blktapctrl_linux.c:86: blktap0 open failed
From: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
Date: Mon, 19 Jul 2010 19:30:28 -0700
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Mon, 19 Jul 2010 19:31:24 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <AANLkTikPUgXoS8XpXyLq47sMSrikf40wkK_r8IyNvIFm@xxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Organization: Citrix VMD
References: <AANLkTikPUgXoS8XpXyLq47sMSrikf40wkK_r8IyNvIFm@xxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
On Mon, 2010-07-19 at 17:27 -0400, Dante Cinco wrote:
> I'm getting this message (subject line) in daemon.log every time I
> start or restart xend. I'm not sure if this is related to the fact
> that I cannot boot up my Windows domU from a VHD file. The Windows
> domU was working fine with Xen 4.0.0 (with 2.6.32.14 dom0 kernel).
> When I upgraded to Xen 4.0.1-rc4 (with 2.6.32.16 dom0 kernel), I can
> no long boot the Windows domU from VHD. The VNC console for the
> Windows HVM has this message:
> 
> Booting from Hard Disk ...
> Boot from Hard Disk failed; could not read the boot disk
> 
> No bootable device.
> Powering off in 30 seconds.
> 
> Here's the disk setting in my Windows domU config file: disk =
> ['tap:tapdisk:vhd:/mnt/win2008sp2.vhd,xvda:sda1,w']
> 
> Here's the other BLKTAPCTRL messages in daemon.log:
> 
> BLKTAPCTRL[2444]: blktapctrl.c:790: blktapctrl: v1.0.0
> BLKTAPCTRL[2444]: blktapctrl.c:792: Found driver: [raw image (aio)]
> BLKTAPCTRL[2444]: blktapctrl.c:792: Found driver: [raw image (sync)]
> BLKTAPCTRL[2444]: blktapctrl.c:792: Found driver: [vmware image (vmdk)]
> BLKTAPCTRL[2444]: blktapctrl.c:792: Found driver: [ramdisk image (ram)]
> BLKTAPCTRL[2444]: blktapctrl.c:792: Found driver: [qcow disk (qcow)]
> BLKTAPCTRL[2444]: blktapctrl.c:792: Found driver: [qcow2 disk (qcow2)]
> BLKTAPCTRL[2444]: blktapctrl_linux.c:86: blktap0 open failed
> BLKTAPCTRL[2444]: blktapctrl.c:859: couldn't open blktap interface
> BLKTAPCTRL[2444]: blktapctrl.c:922: Unable to start blktapctrl

Let's kill the beast.

Blktapctrl is a residual from blktap1 nobody ever bothered to reliably
prevent from trying to start on pvops, unfortunately.

I had a bit of an aha-experience today trying to repro your issue,
before I figured out that you're just running 2.6.3x. It seems to be the
case that the chrdev majors assignment, both dynamically allocated by
blktap1 and -2, tend to be identical when moving from a xen kernel with
blktap1 enabled, to pvops, which only has blktap2.

Which means if somebody starts blktapctrl, it may happily try to open
the kernel link of the first blktap2 (/dev/xen/blktap-2/blktap0) device
as the control node for blktap1 (/dev/xen/blktap0).

In really unfortunate cases, that code around blktapctrl.c:859 above
will suceed, even managing to provoke a stacktrace. Normally wouldn't
happen, in this case I happened to have some somewhat wedged trainwreck
minor number 0 set up, which wasn't aquired by a real tapdisk already.

Should drop blktapctrl from xend start altogether, to avoid confusion in
in both software and users.

Or maybe at least do an environment check and fail with a more friendly
last word on blktap1 matters.

That, of course, nowhere explains your w2k8 problem, right?

Daniel


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel