Subject: [EXTERNAL] Re: [Patch rdma-next] RDMA/mana_ib: handle net event
for pointing to the current netdev

On Fri, Feb 28, 2025 at 02:41:59PM -0800, longli@linuxonhyperv.com wrote:

quoted

+	struct mana_ib_dev *dev = container_of(this, struct mana_ib_dev,

nb);

quoted

+	struct net_device *event_dev = netdev_notifier_info_to_dev(ptr);
+	struct gdma_context *gc = dev->gdma_dev->gdma_context;
+	struct mana_context *mc = gc->mana.driver_data;
+	struct net_device *ndev;
+
+	if (event_dev != mc->ports[0])
+		return NOTIFY_DONE;
+
+	switch (event) {
+	case NETDEV_CHANGEUPPER:
+		rcu_read_lock();
+		ndev = mana_get_primary_netdev_rcu(mc, 0);
+		rcu_read_unlock();

That locking sure looks weird/wrong.

Jason

I think the locking is necessary as mana_get_primary_netdev_rcu() requires a RCU lock. It's safe to nest rcu_read_lock() if it's already held.

I have sent v2. v1 is from an earlier branch and is missing some error handling code.

Thanks,
Long