netdev - Re: [PATCH] net/bonding: Do not transition down slave after speed/duplex check

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Date:   Thu, 30 Apr 2020 11:14:44 -0500
From:   Thomas Falcon <tlfalcon@...ux.ibm.com>
To:     Jay Vosburgh <jay.vosburgh@...onical.com>
Cc:     netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [PATCH] net/bonding: Do not transition down slave after
 speed/duplex check


On 4/29/20 1:38 PM, Jay Vosburgh wrote:
> Thomas Falcon <tlfalcon@...ux.ibm.com> wrote:
>
>> The following behavior has been observed when testing logical partition
>> migration of LACP-bonded VNIC devices in a PowerVM pseries environment.
>>
>> 1. When performing the migration, the bond master detects that a slave has
>>    lost its link, deactivates the LACP port, and sets the port's
>>    is_enabled flag to false.
>> 2. The slave device then updates it's carrier state to off while it resets
>>    itself. This update triggers a NETDEV_CHANGE notification, which performs
>>    a speed and duplex update. The device does not return a valid speed
>>    and duplex, so the master sets the slave link state to BOND_LINK_FAIL.
>> 3. When the slave VNIC device(s) are active again, some operations, such
>>    as setting the port's is_enabled flag, are not performed when transitioning
>>    the link state back to BOND_LINK_UP from BOND_LINK_FAIL, though the state
>>    prior to the speed check was BOND_LINK_DOWN.
> 	Just to make sure I'm understanding correctly, in regards to
> "the state prior to the speed check was BOND_LINK_DOWN," do you mean
> that during step 1, the slave link is set to BOND_LINK_DOWN, and then in
> step 2 changed from _DOWN to _FAIL?
>
>> Affected devices are therefore not utilized in the aggregation though they
>> are operational. The simplest way to fix this seems to be to restrict the
>> link state change to devices that are currently up and running.
> 	This sounds similar to an issue from last fall; can you confirm
> that you're running with a kernel that includes:
>
> 1899bb325149 bonding: fix state transition issue in link monitoring

It did not have that fix.  I will patch the kernel and rerun the test.

Thanks,

Tom

>
> 	-J
> 	
>
>> CC: Jay Vosburgh <j.vosburgh@...il.com>
>> CC: Veaceslav Falico <vfalico@...il.com>
>> CC: Andy Gospodarek <andy@...yhouse.net>
>> Signed-off-by: Thomas Falcon <tlfalcon@...ux.ibm.com>
>> ---
>> drivers/net/bonding/bond_main.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 2e70e43c5df5..d840da7cd379 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -3175,7 +3175,8 @@ static int bond_slave_netdev_event(unsigned long event,
>> 		 * speeds/duplex are available.
>> 		 */
>> 		if (bond_update_speed_duplex(slave) &&
>> -		    BOND_MODE(bond) == BOND_MODE_8023AD) {
>> +		    BOND_MODE(bond) == BOND_MODE_8023AD &&
>> +		    slave->link == BOND_LINK_UP) {
>> 			if (slave->last_link_up)
>> 				slave->link = BOND_LINK_FAIL;
>> 			else
>> -- 
>> 2.18.2
>>
> ---
> 	-Jay Vosburgh, jay.vosburgh@...onical.com