Re: [PATCH net-next] mlx5: count all link events

On May 19, 2021, at 12:18 PM, Jakub Kicinski [off-list ref] wrote:

mlx5 devices were observed generating MLX5_PORT_CHANGE_SUBTYPE_ACTIVE
events without an intervening MLX5_PORT_CHANGE_SUBTYPE_DOWN. This
breaks link flap detection based on Linux carrier state transition
count as netif_carrier_on() does nothing if carrier is already on.
Make sure we count such events.

netif_carrier_event() increments the counters and fires the linkwatch
events. The latter is not necessary for the use case but seems like
the right thing to do.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
.../net/ethernet/mellanox/mlx5/core/en_main.c  |  6 +++++-
include/linux/netdevice.h                      |  2 +-
net/sched/sch_generic.c                        | 18 ++++++++++++++++++
3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index bca832cdc4cb..5a67ebc0c96c 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -91,12 +91,16 @@ void mlx5e_update_carrier(struct mlx5e_priv *priv)

{
	struct mlx5_core_dev *mdev = priv->mdev;
	u8 port_state;
+	bool up;

	port_state = mlx5_query_vport_state(mdev,
					    MLX5_VPORT_STATE_OP_MOD_VNIC_VPORT,
					    0);

-	if (port_state == VPORT_STATE_UP) {
+	up = port_state == VPORT_STATE_UP;
+	if (up == netif_carrier_ok(priv->netdev))
+		netif_carrier_event(priv->netdev);
+	if (up) {
		netdev_info(priv->netdev, "Link up\n");
		netif_carrier_on(priv->netdev);
	} else {

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5cbc950b34df..be1dcceda5e4 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h

@@ -4187,8 +4187,8 @@ unsigned long dev_trans_start(struct net_device *dev);

void __netdev_watchdog_up(struct net_device *dev);

void netif_carrier_on(struct net_device *dev);
-
void netif_carrier_off(struct net_device *dev);
+void netif_carrier_event(struct net_device *dev);

/**
 *	netif_dormant_on - mark device as dormant.

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 44991ea726fc..3090ae32307b 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c

@@ -515,6 +515,24 @@ void netif_carrier_off(struct net_device *dev)

}
EXPORT_SYMBOL(netif_carrier_off);

+/**
+ *	netif_carrier_event - report carrier state event
+ *	@dev: network device
+ *
+ * Device has detected a carrier event but the carrier state wasn't changed.
+ * Use in drivers when querying carrier state asynchronously, to avoid missing
+ * events (link flaps) if link recovers before it's queried.
+ */
+void netif_carrier_event(struct net_device *dev)
+{
+	if (dev->reg_state == NETREG_UNINITIALIZED)
+		return;
+	atomic_inc(&dev->carrier_up_count);
+	atomic_inc(&dev->carrier_down_count);
+	linkwatch_fire_event(dev);
+}
+EXPORT_SYMBOL_GPL(netif_carrier_event);