Re: [libvirt] [PATCH]: Rework xenLinuxDomainDeviceID to support more devices
Daniel P. Berrange wrote:
On Tue, Aug 05, 2008 at 12:12:21PM +0200, Chris Lalancette wrote:
> Recently upstream Xen added support for having xvd devices > 16. For the most
> part, this doesn't really concern libvirt, since for things like attach and
> detach we just pass it through and let xend worry about whether it is supported
> or not. The one place this breaks down is in the stats collecting code, where
> we need to figure out the device number so we can go digging in /sys for the
> statistics.
>
> To remedy this, I've re-written xenLinuxDomainDeviceID() to use regular
> expressions to figure out the device number from the name. The major advantage
> is that now xenLinuxDomainDeviceID() looks fairly identical to
> tools/python/xen/util/blkif.py (in the Xen sources), so that adding additional
> devices in the future should be much easier. It also reduces the size of the
> code, and, in my opinion, the code complexity.
>
> With this patch in place, I was able to get block statistics both on older style
> devices (/dev/xvda) and on the new, expanded devices (/dev/xvdaa).
This patch breaks the test suite for disk name -> device ID conversion.
The test suite also needs to have more tests added to cover the new
interesting boundary conditions for xvdXXX naming.
OK. Well, there were 3 different problems with the test suite:
1) A number of tests were actually wrong. For instance, there is a
DO_TEST("/dev/hdt", 23359); but Xen actually uses the encoding "major*256
+
minor + part". So in this case, the major is 91, and the minor is 64 (according
to http://www.lanana.org/docs/device-list/devices.txt), so that would be 23360.
I've fixed the wrong tests now, and I'll re-submit it with the updated patch.
2) In the hda0 and hda64 case, the upstream Xen regex isn't tight enough. I've
tightened it up in the libvirt patch, so these now pass.
3) The upstream Xen regex's allows /dev/sdi{w,x,y,z}, although they aren't
legal devices. I've fixed up my regex to handle this.
Attached is an updated patch with the above fixes both to my code and to the
test suite. As far as the error reporting goes, I won't argue that my patch
gives slightly less information. However, that being said, I have to believe
that the most likely use of block statistics is something like:
virsh dumpxml <dom>
...see what devices are listed there
virsh domblkstats <dom> <device>
In which case the slightly less verbose error reporting won't matter a whole lot.
Chris Lalancette
Attachments:
- libvirt-stats-linux-expand-2.patch (text/x-patch — 12.2 KB)