[sheepdog] [PATCH 2/2] sheep: release object cache when vdi is released

[MORITA Kazutaka]

At Tue, 29 Jan 2013 14:47:12 +0800,
Liu Yuan wrote:
> 
> On 01/29/2013 02:39 PM, MORITA Kazutaka wrote:
> > At Tue, 29 Jan 2013 13:22:06 +0800,
> > Liu Yuan wrote:
> >>  
> >> +static int local_release_vdi(struct request *req)
> >> +{
> >> +	uint32_t vid = req->rq.vdi.base_vdi_id;
> >> +
> >> +	if (!vid) {
> >> +		sd_iprintf("Some VDI failed to release the object cache. "
> >> +			   "Probably you are running old QEMU.\n");
> >> +		return SD_RES_SUCCESS;
> >> +	}
> >> +
> >> +	object_cache_flush_vdi(vid);
> >> +	object_cache_delete(vid);
> > 
> > I wonder if sheep should delete cache here.  With this patch, object
> > cache cannot survive a temporal reboot of the guest os.  Is it
> > expected behavior?
> > 
> 
> This is a trade off. If we don't release the object cache, then VM can't
> be safely restarted on another node without manually 'collie vdi cache
> flush vm' on the previously hosted node.
> 
> As reboot of VM is really seldom operation ( EC2 even doesn't support
> reboot & shutdown), I think we can trade this for intelligence that
> doesn't require users to manually flush&del cache before migrating the
> VM. I think live migration of VM need this cache behavior too.

Agreed, applied this patch, thanks!

Kazutaka