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

["David P. Quigley" <dpquigl@xxxxxxxxxxxxx>]

On Fri, 2010-01-22 at 10:43 -0800, Jeremy Fitzhardinge wrote:
> On 01/21/2010 11:14 PM, Pasi KÃrkkÃinen 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 KÃrkkÃinen wrote:
> >>      
> >>> On Fri, Jan 22, 2010 at 12:55:52AM +0200, Pasi KÃrkkÃinen 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 KÃrkkÃinen 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

Well if he needs any help feel free to ask. I definitely can justify
spending time on working on this.

Dave


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