netdev - Re: [PATCH net 1/2] ibmvnic: notify peers when failover and migration happen

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Date:   Wed, 04 Nov 2020 20:54:45 -0800
From:   drt <drt@...ux.vnet.ibm.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Lijun Pan <ljp@...ux.ibm.com>, netdev@...r.kernel.org,
        Brian King <brking@...ux.vnet.ibm.com>,
        Pradeep Satyanarayana <pradeeps@...ux.vnet.ibm.com>,
        Dany Madden <drt@...ux.ibm.com>
Subject: Re: [PATCH net 1/2] ibmvnic: notify peers when failover and migration
 happen

On 2020-10-30 13:27, Jakub Kicinski wrote:
> On Wed, 28 Oct 2020 00:57:41 -0500 Lijun Pan wrote:
>> We need to notify peers only when failover and migration happen.
>> It is unnecessary to call that in other events like
>> FATAL, NON_FATAL, CHANGE_PARAM, and TIMEOUT resets
>> since in those scenarios the MAC address and ip address mapping
>> does not change. Originally all the resets except CHANGE_PARAM
>> are processed by do_reset such that we need to find out
>> failover and migration cases in do_reset and call notifier functions.
>> We only need to notify peers in do_reset and do_hard_reset.
>> We don't need notify peers in do_change_param_reset since it is
>> a CHANGE_PARAM reset. In a nested reset case, it will finally
>> call into do_hard_reset with reasons other than failvoer and
>> migration. So, we don't need to check the reset reason in
>> do_hard_reset and just call notifier functions anyway.
> 
> You're completely undoing the commit you linked to:

Testing is underway. We will clarify the description in the next 
version.

Thank you for your review and feedback.
Dany
> 
> commit 61d3e1d9bc2a1910d773cbf4ed6f587a7a6166b5
> Author: Nathan Fontenot <nfont@...ux.vnet.ibm.com>
> Date:   Mon Jun 12 20:47:45 2017 -0400
> 
>     ibmvnic: Remove netdev notify for failover resets
> 
>     When handling a driver reset due to a failover of the backing
>     server on the vios, doing the netdev_notify_peers() can cause
>     network traffic to stall or halt. Remove the netdev notify call
>     for failover resets.
> 
>     Signed-off-by: Nathan Fontenot <nfont@...ux.vnet.ibm.com>
>     Signed-off-by: David S. Miller <davem@...emloft.net>
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
> b/drivers/net/ethernet/ibm/ibmvnic.c
> index fd3ef3005fb0..59ea7a5ae776 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -1364,7 +1364,9 @@ static int do_reset(struct ibmvnic_adapter 
> *adapter,
>         for (i = 0; i < adapter->req_rx_queues; i++)
>                 napi_schedule(&adapter->napi[i]);
> 
> -       netdev_notify_peers(netdev);
> +       if (adapter->reset_reason != VNIC_RESET_FAILOVER)
> +               netdev_notify_peers(netdev);
> +
>         return 0;
>  }
> 
> But you don't seem to address why this change was unnecessary.
> 
> AFAIK you're saying "we only need this event for FAILOVER and MOBILITY"
> but the previous commit _excluded_ FAILOVER for some vague reason.
> 
> If the previous commit was incorrect you need to explain that in the
> commit message.
> 
>> netdev_notify_peers calls below two functions with rtnl lock().
>> 	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, dev);
>> 	call_netdevice_notifiers(NETDEV_RESEND_IGMP, dev);
>> When netdev_notify_peers was substituted in
>> commit 986103e7920c ("net/ibmvnic: Fix RTNL deadlock during device 
>> reset"),
>> call_netdevice_notifiers(NETDEV_RESEND_IGMP, dev) was missed.
> 
> That should be a separate patch.
> 
>> Fixes: 61d3e1d9bc2a ("ibmvnic: Remove netdev notify for failover 
>> resets")
>> Fixes: 986103e7920c ("net/ibmvnic: Fix RTNL deadlock during device
>> reset")
> 
> Please don't line-wrap fixes tags.
> 
>> Suggested-by: Brian King <brking@...ux.vnet.ibm.com>
>> Suggested-by: Pradeep Satyanarayana <pradeeps@...ux.vnet.ibm.com>
>> Signed-off-by: Dany Madden <drt@...ux.ibm.com>
>> Signed-off-by: Lijun Pan <ljp@...ux.ibm.com>
>> ---
>>  drivers/net/ethernet/ibm/ibmvnic.c | 8 +++++++-
>>  1 file changed, 7 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c 
>> b/drivers/net/ethernet/ibm/ibmvnic.c
>> index 1b702a43a5d0..718da39f5ae4 100644
>> --- a/drivers/net/ethernet/ibm/ibmvnic.c
>> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
>> @@ -2067,8 +2067,11 @@ static int do_reset(struct ibmvnic_adapter 
>> *adapter,
>>  	for (i = 0; i < adapter->req_rx_queues; i++)
>>  		napi_schedule(&adapter->napi[i]);
>> 
>> -	if (adapter->reset_reason != VNIC_RESET_FAILOVER)
>> +	if (adapter->reset_reason == VNIC_RESET_FAILOVER ||
>> +	    adapter->reset_reason == VNIC_RESET_MOBILITY) {
>>  		call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, netdev);
>> +		call_netdevice_notifiers(NETDEV_RESEND_IGMP, netdev);
>> +	}
>> 
>>  	rc = 0;
>> 
>> @@ -2138,6 +2141,9 @@ static int do_hard_reset(struct ibmvnic_adapter 
>> *adapter,
>>  	if (rc)
>>  		return IBMVNIC_OPEN_FAILED;
>> 
>> +	call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, netdev);
>> +	call_netdevice_notifiers(NETDEV_RESEND_IGMP, netdev);
>> +
>>  	return 0;
>>  }
>>