[net,v2] ice: Fix error with handling of bonding MTU

When a bonded interface is destroyed, .ndo_change_mtu can be called
during the tear-down process while the RTNL lock is held.  This is a
problem since the auxiliary driver linked to the LAN driver needs to be
notified of the MTU change, and this requires grabbing a device_lock on
the auxiliary_device's dev.  Currently this is being attempted in the
same execution context as the call to .ndo_change_mtu which is causing a
dead-lock.

Move the notification of the changed MTU to a separate execution context
(watchdog service task) and eliminate the "before" notification.

Fixes: 348048e724a0e ("ice: Implement iidc operations")
Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
---
v2: target change from net-next to net
---
 drivers/net/ethernet/intel/ice/ice.h      |  1 +
 drivers/net/ethernet/intel/ice/ice_main.c | 29 +++++++++++------------
 2 files changed, 15 insertions(+), 15 deletions(-)

On 2/18/22 15:39, Dave Ertman wrote:
> When a bonded interface is destroyed, .ndo_change_mtu can be called
> during the tear-down process while the RTNL lock is held.  This is a
> problem since the auxiliary driver linked to the LAN driver needs to be
> notified of the MTU change, and this requires grabbing a device_lock on
> the auxiliary_device's dev.  Currently this is being attempted in the
> same execution context as the call to .ndo_change_mtu which is causing a
> dead-lock.
> 
> Move the notification of the changed MTU to a separate execution context
> (watchdog service task) and eliminate the "before" notification.
> 
> Fixes: 348048e724a0e ("ice: Implement iidc operations")
> Signed-off-by: Dave Ertman <david.m.ertman@intel.com>

I no longer see the process hang with this patch applied.

Tested-by: Jonathan Toppins <jtoppins@redhat.com>

> ---
> v2: target change from net-next to net
> ---
>   drivers/net/ethernet/intel/ice/ice.h      |  1 +
>   drivers/net/ethernet/intel/ice/ice_main.c | 29 +++++++++++------------
>   2 files changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice.h b/drivers/net/ethernet/intel/ice/ice.h
> index a9fa701aaa95..058334db37a9 100644
> --- a/drivers/net/ethernet/intel/ice/ice.h
> +++ b/drivers/net/ethernet/intel/ice/ice.h
> @@ -484,6 +484,7 @@ enum ice_pf_flags {
>   	ICE_FLAG_MDD_AUTO_RESET_VF,
>   	ICE_FLAG_LINK_LENIENT_MODE_ENA,
>   	ICE_FLAG_PLUG_AUX_DEV,
> +	ICE_FLAG_MTU_CHANGED,
>   	ICE_PF_FLAGS_NBITS		/* must be last */
>   };
>   
> diff --git a/drivers/net/ethernet/intel/ice/ice_main.c b/drivers/net/ethernet/intel/ice/ice_main.c
> index 17a9bb461dc3..d47d00c5b456 100644
> --- a/drivers/net/ethernet/intel/ice/ice_main.c
> +++ b/drivers/net/ethernet/intel/ice/ice_main.c
> @@ -2256,6 +2256,17 @@ static void ice_service_task(struct work_struct *work)
>   	if (test_and_clear_bit(ICE_FLAG_PLUG_AUX_DEV, pf->flags))
>   		ice_plug_aux_dev(pf);
>   
> +	if (test_and_clear_bit(ICE_FLAG_MTU_CHANGED, pf->flags)) {
> +		struct iidc_event *event;
> +
> +		event = kzalloc(sizeof(*event), GFP_KERNEL);
> +		if (event) {
> +			set_bit(IIDC_EVENT_AFTER_MTU_CHANGE, event->type);
> +			ice_send_event_to_aux(pf, event);
> +			kfree(event);
> +		}
> +	}
> +
>   	ice_clean_adminq_subtask(pf);
>   	ice_check_media_subtask(pf);
>   	ice_check_for_hang_subtask(pf);
> @@ -6820,7 +6831,6 @@ static int ice_change_mtu(struct net_device *netdev, int new_mtu)
>   	struct ice_netdev_priv *np = netdev_priv(netdev);
>   	struct ice_vsi *vsi = np->vsi;
>   	struct ice_pf *pf = vsi->back;
> -	struct iidc_event *event;
>   	u8 count = 0;
>   	int err = 0;
>   
> @@ -6855,14 +6865,6 @@ static int ice_change_mtu(struct net_device *netdev, int new_mtu)
>   		return -EBUSY;
>   	}
>   
> -	event = kzalloc(sizeof(*event), GFP_KERNEL);
> -	if (!event)
> -		return -ENOMEM;
> -
> -	set_bit(IIDC_EVENT_BEFORE_MTU_CHANGE, event->type);
> -	ice_send_event_to_aux(pf, event);
> -	clear_bit(IIDC_EVENT_BEFORE_MTU_CHANGE, event->type);
> -
>   	netdev->mtu = (unsigned int)new_mtu;
>   
>   	/* if VSI is up, bring it down and then back up */
> @@ -6870,21 +6872,18 @@ static int ice_change_mtu(struct net_device *netdev, int new_mtu)
>   		err = ice_down(vsi);
>   		if (err) {
>   			netdev_err(netdev, "change MTU if_down err %d\n", err);
> -			goto event_after;
> +			return err;
>   		}
>   
>   		err = ice_up(vsi);
>   		if (err) {
>   			netdev_err(netdev, "change MTU if_up err %d\n", err);
> -			goto event_after;
> +			return err;
>   		}
>   	}
>   
>   	netdev_dbg(netdev, "changed MTU to %d\n", new_mtu);
> -event_after:
> -	set_bit(IIDC_EVENT_AFTER_MTU_CHANGE, event->type);
> -	ice_send_event_to_aux(pf, event);
> -	kfree(event);
> +	set_bit(ICE_FLAG_MTU_CHANGED, pf->flags);
>   
>   	return err;
>   }

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@osuosl.org> On Behalf Of
> Dave Ertman
> Sent: Saturday, February 19, 2022 2:09 AM
> To: intel-wired-lan@lists.osuosl.org
> Subject: [Intel-wired-lan] [PATCH net v2] ice: Fix error with handling of
> bonding MTU
> 
> When a bonded interface is destroyed, .ndo_change_mtu can be called
> during the tear-down process while the RTNL lock is held.  This is a problem
> since the auxiliary driver linked to the LAN driver needs to be notified of the
> MTU change, and this requires grabbing a device_lock on the
> auxiliary_device's dev.  Currently this is being attempted in the same
> execution context as the call to .ndo_change_mtu which is causing a dead-
> lock.
> 
> Move the notification of the changed MTU to a separate execution context
> (watchdog service task) and eliminate the "before" notification.
> 
> Fixes: 348048e724a0e ("ice: Implement iidc operations")
> Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
> ---
> v2: target change from net-next to net
> ---
>  drivers/net/ethernet/intel/ice/ice.h      |  1 +
>  drivers/net/ethernet/intel/ice/ice_main.c | 29 +++++++++++------------
>  2 files changed, 15 insertions(+), 15 deletions(-)
> 

Tested-by: Gurucharan G <gurucharanx.g@intel.com> (A Contingent worker at Intel)