[PATCH] node_device: Use "udev" monitor source

Michal Privoznik mprivozn at redhat.com
Tue Nov 17 13:29:27 UTC 2020


On 11/17/20 1:51 PM, Daniel P. Berrangé wrote:
> On Tue, Nov 17, 2020 at 01:29:47PM +0100, Michal Privoznik wrote:
>> In v6.3.0-rc1~67 I've made a switch: instead of listening on udev
>> events the nodedev driver started listening for kernel events.
>> This was because when a device changes its name (e.g. NICs) we
>> will get "move" event with DEVPATH_OLD property set, which we can
>> then use to remove the old device and thus keep our internal list
>> up to date. The switch to "kernel" source was made because if the
>> old NICs naming (eth0, eth1, ...) is enabled (e.g. via
>> net.ifnames=0 on the kernel cmd line) then udev overwrites the
>> property with the new name making our internal list go out of
>> sync. Interestingly, when the od NICs naming is not enabled then
>> the DEVPATH_OLD contains the correct value.
> 
> I don't see any difference in properties regardless of net.ifnames
> is 0 or 1. In both cases, there is DEVPATH + DEVPAT_OLD, and
> INTERFACE has the new NIC name.  Can you actually reproduce the
> original problem with net.ifnames=0 ?  If so, which distro ?

Have you tried renaming back and forth? for instance:

# ip link set tunl0 name tunl1
# ip link set tunl1 name tunl0


The "kernel" source yields:

KERNEL[778387.296879] move     /devices/virtual/net/tunl1 (net)
ACTION=move
DEVPATH=/devices/virtual/net/tunl1
DEVPATH_OLD=/devices/virtual/net/tunl0
IFINDEX=5
INTERFACE=tunl1
SEQNUM=20701
SUBSYSTEM=net

KERNEL[778400.944769] move     /devices/virtual/net/tunl0 (net)
ACTION=move
DEVPATH=/devices/virtual/net/tunl0
DEVPATH_OLD=/devices/virtual/net/tunl1
IFINDEX=5
INTERFACE=tunl0
SEQNUM=20702
SUBSYSTEM=net


But "udev" gets:

UDEV  [778387.297247] move     /devices/virtual/net/tunl1 (net)
ACTION=move
DEVPATH=/devices/virtual/net/tunl1
DEVPATH_OLD=/devices/virtual/net/tunl0
IFINDEX=5
INTERFACE=tunl1
SEQNUM=20701
SUBSYSTEM=net
USEC_INITIALIZED=5901449841
net.ifnames=0

UDEV  [778400.945195] move     /devices/virtual/net/tunl1 (net)
ACTION=move
DEVPATH=/devices/virtual/net/tunl1
DEVPATH_OLD=/devices/virtual/net/tunl1
IFINDEX=5
INTERFACE=tunl1
SEQNUM=20702
SUBSYSTEM=net
USEC_INITIALIZED=5901449841
net.ifnames=0


In both cases the first rename (tunl0 -> tunl1) gets correct 
DEVPATH_OLD, but the second rename is problematic (tunl1 -> tunl0) and 
only "kernel" gets it right.

This is on 5.9.1-gentoo-x86_64 and

# udevadm --version
243


> 
>>
>> But as it turns out, "kernel" source might be missing some other
>> important properties, e.g. USB vendor/product IDs. Therefore,
>> switch back to "udev" source and wish the best of luck to users
>> using the old NICs naming.
>>
>> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1897625
>> Fixes: 9a13704818e4a018723e0ec5b9e97b176f1c8584
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>   src/node_device/node_device_udev.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
>> index 65f312d8f4..dec19a3166 100644
>> --- a/src/node_device/node_device_udev.c
>> +++ b/src/node_device/node_device_udev.c
>> @@ -1983,7 +1983,7 @@ nodeStateInitialize(bool privileged,
>>   
>>       virObjectLock(priv);
>>   
>> -    priv->udev_monitor = udev_monitor_new_from_netlink(udev, "kernel");
>> +    priv->udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
>>       if (!priv->udev_monitor) {
>>           virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
>>                          _("udev_monitor_new_from_netlink returned NULL"));
> 
> Reviewed-by: Daniel P. Berrangé <berrange at redhat.com>
> 

Pushed. Thanks.

Michal




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