On Tue 13 Oct 2015 05:38:30 PM CEST, Stefan Hajnoczi wrote: >> query-blockstats always returns a BlockDeviceStats structure for each >> BDS, regardless of whether it implements accounting or not. Since the >> field is mandatory there's no way to tell that from the values alone. >> >> This field solves that problem by indicating which BDSs support I/O >> accounting. > > I'm not sure I understand the problem. > > If I/O accounting isn't being used then all fields will be 0?
Yes, but there's no way to tell if that happens because I/O accounting is not supported or because there hasn't been any I/O yet. There's one additional problem: this patch assumes that accounting is supported if this BDS is attached to a BlockBackend. But we don't know if the device model supports accounting or not, I still need to figure out what's the best way to do it. Berto
