[libvirt] virDomainAttachDevice error during disk hotplug

[Daniel P. Berrange]

On Fri, Aug 16, 2013 at 03:48:25PM -0500, Doug Goldstein wrote:
> On Fri, Aug 16, 2013 at 8:30 AM, Daniel P. Berrange <berrange at redhat.com>wrote:
> 
> > On Fri, Aug 16, 2013 at 06:51:21PM +0530, Deepak C Shetty wrote:
> > > On 08/10/2013 06:20 PM, Deepak C Shetty wrote:
> > > >2013-08-10 11:19:41.772+0000: 1091: debug :
> > > >qemuMonitorIOProcess:345 : QEMU_MONITOR_IO_PROCESS:
> > > >mon=0x7f92f0007830 buf={"return": "could not open disk image
> > > >/var/run/vdsm/3333017d-1278-4bfb-8129-62bded257399: Invalid
> > > >argument\r\n", "id": "libvirt-67"}^M
> > >
> > > Any suggestions from anyone on why "Invalid Argument" is being returned ?
> >
> > QEMU's error reporting for disk configs is known to be worse than
> > useless.  You can't infer anything useful from "Invalid Argument"
> > I'm afraid.
> >
> >
> I'm going to go out on a limb here and say its an O_DIRECT error. Reason
> I'm guessing this is that O_DIRECT is not supported on tmpfs and when you
> attempt to open() a file with O_DIRECT and its not supported you'll get
> back -EINVAL from the kernel. Newer systems have /run as tmpfs and /var/run
> symlinked to /run.

Oh, yes, good one.

I really wish QEMU would provide a better error message for this case,
since people hit it all the time

Daniel
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