Re: [Xen-devel] [PATCH v2] Only call stat() when adding a disk if we expect a device to exist.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2013-04-24 at 12:56 +0100, Ian Campbell wrote:
> On Tue, 2013-04-23 at 15:08 +0100, Roger Pau Monne wrote:
> > On 23/04/13 11:59, David Scott wrote:
> > > We consider calling stat() a helpful error check in the following
> > > circumstances only:
> > >  1. the disk backend type must be PHYsical
> > >  2. the disk backend domain must be the same as the running libxl
> > >     code (ie LIBXL_TOOLSTACK_DOMID)
> > >  3. there must not be a hotplug script because this would imply that
> > >     the device won't be created until after the hotplug script has
> > >     run.
> > > 
> > > With this fix, it is possible to use qemu's built-in block drivers
> > > such as ceph/rbd, with a xl config disk spec like this:
> > > 
> > > disk=[ 
> > > 'backendtype=qdisk,format=raw,vdev=hda,access=rw,target=rbd:rbd/ubuntu1204.img'
> > >  ]
> > > 
> > > Signed-off-by: David Scott <dave.scott@xxxxxxxxxxxxx>
> > > Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> > 
> > Acked-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> 
> Applied, thanks.

This patch had the slightly unfortunate impact of causing libxl to not
use blkback for actual block devices present in dom0, causing it to fall
back to tap/qemu.

I'm having a look now...

Ian.



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