netdev - Re: [PATCH net 1/4] ibmvnic: Allow extra failures before disabling

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Date:   Sat, 22 Jan 2022 16:22:10 -0800
From:   Dany Madden <drt@...ux.ibm.com>
To:     Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
Cc:     netdev@...r.kernel.org, Brian King <brking@...ux.ibm.com>,
        Rick Lindsley <ricklind@...ux.ibm.com>
Subject: Re: [PATCH net 1/4] ibmvnic: Allow extra failures before disabling

On 2022-01-21 18:59, Sukadev Bhattiprolu wrote:
> If auto-priority-failover (APF) is enabled and there are at least two
> backing devices of different priorities, some resets like fail-over,
> change-param etc can cause at least two back to back failovers. 
> (Failover
> from high priority backing device to lower priority one and then back
> to the higher priority one if that is still functional).
> 
> Depending on the timimg of the two failovers it is possible to trigger
> a "hard" reset and for the hard reset to fail due to failovers. When 
> this
> occurs, the driver assumes that the network is unstable and disables 
> the
> VNIC for a 60-second "settling time". This in turn can cause the 
> ethtool
> command to fail with "No such device" while the vnic automatically 
> recovers
> a little while later.
> 
> Given that it's possible to have two back to back failures, allow for 
> extra
> failures before disabling the vnic for the settling time.
> 
> Fixes: f15fde9d47b8 ("ibmvnic: delay next reset if hard reset fails")
> Signed-off-by: Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
Reviewed-by: Dany Madden <drt@...ux.ibm.com>

> ---
>  drivers/net/ethernet/ibm/ibmvnic.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ibm/ibmvnic.c
> b/drivers/net/ethernet/ibm/ibmvnic.c
> index 0bb3911dd014..9b2d16ad76f1 100644
> --- a/drivers/net/ethernet/ibm/ibmvnic.c
> +++ b/drivers/net/ethernet/ibm/ibmvnic.c
> @@ -2598,6 +2598,7 @@ static void __ibmvnic_reset(struct work_struct 
> *work)
>  	struct ibmvnic_rwi *rwi;
>  	unsigned long flags;
>  	u32 reset_state;
> +	int num_fails = 0;
>  	int rc = 0;
> 
>  	adapter = container_of(work, struct ibmvnic_adapter, ibmvnic_reset);
> @@ -2651,11 +2652,23 @@ static void __ibmvnic_reset(struct work_struct 
> *work)
>  				rc = do_hard_reset(adapter, rwi, reset_state);
>  				rtnl_unlock();
>  			}
> -			if (rc) {
> -				/* give backing device time to settle down */
> +			if (rc)
> +				num_fails++;
> +			else
> +				num_fails = 0;
> +
> +			/* If auto-priority-failover is enabled we can get
> +			 * back to back failovers during resets, resulting
> +			 * in at least two failed resets (from high-priority
> +			 * backing device to low-priority one and then back)
> +			 * If resets continue to fail beyond that, give the
> +			 * adapter some time to settle down before retrying.
> +			 */
> +			if (num_fails >= 3) {
>  				netdev_dbg(adapter->netdev,
> -					   "[S:%s] Hard reset failed, waiting 60 secs\n",
> -					   adapter_state_to_string(adapter->state));
> +					   "[S:%s] Hard reset failed %d times, waiting 60 secs\n",
> +					   adapter_state_to_string(adapter->state),
> +					   num_fails);
>  				set_current_state(TASK_UNINTERRUPTIBLE);
>  				schedule_timeout(60 * HZ);
>  			}