net/mlx5: Avoid false positive lockdep warning by adding lock_class_key

Downstream patch will add devcom component which will be locked in
many places. This can lead to a false positive "possible circular
locking dependency" warning by lockdep, on flows which lock more than
one mlx5 devcom component, such as probing ETH aux device.
Hence, add a lock_class_key per mlx5 device.
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Mark Bloch <mbloch@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c

@@ -31,6 +31,7 @@ struct mlx5_devcom_comp {
 	struct kref ref;
 	bool ready;
 	struct rw_semaphore sem;
+	struct lock_class_key lock_key;
 };
 
 struct mlx5_devcom_comp_dev {
@@ -119,6 +120,8 @@ mlx5_devcom_comp_alloc(u64 id, u64 key, mlx5_devcom_event_handler_t handler)
 	comp->key = key;
 	comp->handler = handler;
 	init_rwsem(&comp->sem);
+	lockdep_register_key(&comp->lock_key);
+	lockdep_set_class(&comp->sem, &comp->lock_key);
 	kref_init(&comp->ref);
 	INIT_LIST_HEAD(&comp->comp_dev_list_head);
 
@@ -133,6 +136,7 @@ mlx5_devcom_comp_release(struct kref *ref)
 	mutex_lock(&comp_list_lock);
 	list_del(&comp->comp_list);
 	mutex_unlock(&comp_list_lock);
+	lockdep_unregister_key(&comp->lock_key);
 	kfree(comp);
 }