Re: [Xen-devel] Xen guest disk online resize, xenstore/blkback/blkfront questions

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Jan 07, 2010 at 11:54:19PM -0800, Daniel Stodden wrote:
> On Wed, 2010-01-06 at 16:57 -0500, Pasi Kärkkäinen wrote:
> 
> > > >   Any problems getting the new size/sectors on-the-fly in the kernel? 
> > > 
> > > You might need to close and reopen the block device? 
> > > 
> > > Idle speculation: perhaps instead of an explicit "resize" field in
> > > xenstore you could just have the backend continue watching the
> > > 'physical-device' node even after everything is connected the first time
> > > and if it is rewritten (including to the same value) reopening the
> > > physical device and setting things up again (picking up a size change as
> > > a side effect).
> > > 
> > 
> > Good idea. I'll experiment with this.
> 
> The XCP kernel has support for transparent pause/unpause. Which takes of
> the queue flush in order to get the bdev closed.
> 
> Below is that patch which enables switching the physical node,
> safety-checking if the VBD is paused etc. Matters not so much for
> snapshotting, rather for cross-vg stuff.
> 
> It happens to work otherwise as IanC suggested.
> 
> It may be more than you're up to in order to get a resize done, e.g.
> depends on whether you want to piggyback close/open into pause/unpause
> or not (as a rule of thumb, it's safe to say that pause applications
> want a close anyway :]). 
> 
> Didn't check for bitrot, sorry in advance.
>

Interesting. I'll take a look at this aswell. Thanks!

> HTH. Let me know if you're missing something or how it's going.
> 

Yep. I'll get back to you. 

-- Pasi


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