Re: [PATCH 6/6] nodedev: Don't fail device enumeration if MDEVCTL is missing

On 4/13/21 4:58 PM, Erik Skultety wrote: > On Tue, Apr 13, 2021 at 12:01:57PM +0200, Michal Privoznik wrote: > > After all devices were enumerated, the enumeration thread call > > nodeDeviceUpdateMediatedDevices() to refresh the state of > > mediated devices. This means that 'mdevctl' will be executed. But > > it may be missing on some systems (e.g. mine) in which case we > > should just skip the update of mdevs instead of failing whole > > device enumeration. > > > > Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; > > ---

> I'll give you an example where this can get annoying. I just tested this on a > machine where I had mdevctl installed previously, so I removed it, but I had > some mdevs defined. Because mdevctl is now missing, udev reports some mdev > devices, but that's it. After I re-installed mdevctl back I expected libvirtd > to at least be able to define a device, but I got an error from mdevctl that > that device already is defined, but libvirtd doesn't know it's persistent > because /etc/mdevctl.d was never scanned, so I suddenly see devices as > transient and have to manually remove the mdevctl definitions. Fair enough, but is this even supposed to work? I mean, if you install/uninstall a tool without libvirtd restart then you shouldn't expect things to work. We use binaries, because some tools don't provide libraries. If mdevctl was a library then no such thing as install/uninstall without libvirtd would be possible. Either it would be still mapped into libvirtd (even after you've removed it from disk), or it won't be loaded after you've installed it.

I'll switch over to virFindFileInPath(), though.