Re: [Xen-devel] What is the state of blktap2?

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 01/21/2010 11:14 PM, Pasi Kärkkäinen wrote:
> On Thu, Jan 21, 2010 at 06:13:46PM -0500, David P. Quigley wrote:
>    
> > On Fri, 2010-01-22 at 00:59 +0200, Pasi Kärkkäinen wrote:
> >      
> > > On Fri, Jan 22, 2010 at 12:55:52AM +0200, Pasi Kärkkäinen wrote:
> > >        
> > > > On Thu, Jan 21, 2010 at 05:46:05PM -0500, David P. Quigley wrote:
> > > >          
> > > > > On Fri, 2010-01-22 at 00:38 +0200, Pasi Kärkkäinen wrote:
> > > > >            
> > > > > > On Thu, Jan 21, 2010 at 05:27:45PM -0500, David P. Quigley wrote:
> > > > > >              
> > > > > > > I'm currently working on moving storage services into their own domain
> > > > > > > and I've been looking at blktap2. I've been trying to get an image
> > > > > > > mounted with blktap2 and for some odd reason and tapdisk2 keeps hanging
> > > > > > > instead of quitting at the end. I haven't removed any of the storage
> > > > > > > startup code at this point so everything should be as it normally is in
> > > > > > > xen-unstable. Is this a known bug? Are there some requirements on
> > > > > > > blktap2 that I'm possibly not meeting? Is there anything in particular
> > > > > > > that I should be looking at to try to debug the problem?
> > > > > > >
> > > > > > >                
> > > > > > What kernel are you using? pv_ops dom0 kernel doesn't have working blktap2 yet..
> > > > > > linux-2.6.18-xen has working blktap2 support.
> > > > > >
> > > > > > -- Pasi
> > > > > >              
> > > > > I'm using the patches maintained by Andrew Lyon that are applied to
> > > > > 2.6.31.10. These are supposedly based on the OpenSUSE patches and can be
> > > > > found at http://code.google.com/p/gentoo-xen-kernel/downloads/list. I
> > > > > need a more recent kernel version so the 2.6.18 dom0 kernel isn't an
> > > > > option for me.
> > > > >
> > > > >            
> > > > Ok. I'm not sure if those OpenSUSE patches have blktap2 support included?
> > > > I know that at least Citrix XenServer, XCP and XCI 2.6.27 kernels do have 
> > > > blktap2.
> > > >
> > > > See:
> > > > http://wiki.xensource.com/xenwiki/XenDom0Kernels
> > > >
> > > >          
> > > More details about the pv_ops dom0 kernel (2.6.31.6 currently): It has initial 
> > > version
> > > of blktap2 patches, but they'd need some debugging, because they're not yet 
> > > working.
> > >
> > > -- Pasi
> > >        
> > Looking under drivers through a make menuconfig on the pvops kernel I
> > don't see an entry for blktap2. I just see the entry for blktap. I know
> > that blktap2 was supposed to replace blktap but in the Novell patches
> > they are two separate config options and I don't seem to be seeing the
> > second on in the pvops kernel. Do I just enable blktap under drivers and
> > use tap:tapdisk:<type>  in the domU config to use blktap2?
> >
> >      
> See:
> http://git.kernel.org/?p=linux/kernel/git/jeremy/xen.git;a=shortlog;h=xen/master
>
> Commits like:
>
> 2009-12-10      Jeremy Fitzhardinge     Merge branch 'xen/dom0/backend/blktap2' 
> into xen/master
> 2009-12-10      Jeremy Fitzhardinge     xen/blktap2: don't init on non-Xen 
> system
> 2009-12-04      Ian Campbell    blktap: cleanup usage of sysfs
> 2009-12-04      Ian Campbell    blktap: wean off of use of the BlkBack pageflag.
> 2009-12-04      Ian Campbell    Port blktap2 from 2.6.18 to tip.
> 2009-12-04      Ian Campbell    Add build infrastrucuture for blktap2.
> 2009-12-04      Ian Campbell    patch 03-blktap2-patch
> 2009-12-04      Ian Campbell    patch 02-blkback-pagemap-patch
> 2009-12-04      Ian Campbell    patch 01-blktap-patch
>
> I haven't tried it myself yet..
>    
It is pretty broken at present, and I'll probably commit a change to 
disable it for now.  Fortunately it looks like Daniel Stodden is going 
to have a crack at fixing it up.
    J

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