[Libvir] [PATCH] Add the check of the device source

[Masayuki Sunou]

Hi Dan

Thank you for a reviewing.

I understand your suggestion. 
 - Libvirt should not check the device source path.
 - The device source path should be checked by the Xen hotplug scripts.

I consider a fixing of Xen.
Thefore, I decline applying this patch.

Thanks,
Masayuki Sunou.


In message <20070712025025.GA18778 at redhat.com>
   "Re: [Libvir] [PATCH] Add the check of the device source"
   ""Daniel P. Berrange" <berrange at redhat.com>" wrote:

> On Thu, Jul 12, 2007 at 09:34:18AM +0900, Masayuki Sunou wrote:
> > Hi
> > 
> > If specified device source does not exist,
> > Not appropriate error is displayed.
> > ----------------------------------------------------------------------
> > # virsh attach-disk PV_FC7_14 NOT_EXIST_PATH xvdd
> > libvir: Xen Daemon error : POST operation failed: (xend.err 'Device
> > 51760 (vbd) could not be connected. Hotplug scripts not working.')
> > ----------------------------------------------------------------------
> 
> This is a bug in the Xen hotplug scripts.
> 
> > This patch checks the existence of the device source path, 
> > and correct message is displayed in case of error.
> 
> Checking the device path in libvirt does not work because libvirt is not
> running under the same security context as XenD or the hotplug scripts.
> So while libvirt make check & successfully be able to access the device,
> XenD / hotplug script may still fail due to SELinux policy constraints.
> The only place you can correctly check for this is in the hotplug scripts
> themelves.
> 
> As an example to deal with the scenario you describe, it is possible to
> add the following to /etc/xen/scripts/block:
> 
> --- /etc/xen/scripts/block.orig       2006-11-28 16:04:50.000000000 -0500
> +++ /etc/xen/scripts/block      2007-07-11 23:10:31.000000000 -0400
> @@ -252,6 +252,12 @@
>          FRONTEND_UUID=$(xenstore_read_default \
>              "/local/domain/$FRONTEND_ID/vm" 'unknown')
>          claim_lock "block"
> +        if [ ! -e "$dev" ] ; then
> +           fatal "Path $dev does not exist"
> +        fi
> +        if [ ! -b "$dev" ]; then
> +           fatal "Path $dev is not a block device"
> +        fi
>          check_device_sharing "$dev" "$mode"
>          write_dev "$dev"
>          release_lock "block"
> 
> 
> This will mean that a real message gets sent back:
> 
> # virsh attach-disk f7pv bogus xvdd
> libvir: Xen Daemon error : POST operation failed: (xend.err 
>   'Device 51760 (vbd) could not be connected. Path /dev/bogus does not exist')
> 
> This also means that other Xen tools also benefit from the error checking.
> 
> 
> There's probably other checks that can be done in the hotplug scripts for
> various conditions - basically any time you see ever see the message 
> 'Hotplug scripts not working'  from Xen is a bug in the hotplug scripts
> themselves which needs fixing.
> 
> Regards,
> Dan.
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