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

[Daniel Stodden <daniel.stodden@xxxxxxxxxx>]

On Wed, 2010-01-06 at 16:57 -0500, Pasi KÃrkkÃinen 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.

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

Cheers,
Daniel

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