RDMA/cma: Split apart the multiple uses of the same list heads

Two list heads in the rdma_id_private are being used for multiple
purposes, to save a few bytes of memory. Give the different purposes
different names and union the memory that is clearly exclusive.

list splits into device_item and listen_any_item. device_item is threaded
onto the cma_device's list and listen_any goes onto the
listen_any_list. IDs doing any listen cannot have devices.

listen_list splits into listen_item and listen_list. listen_list is on the
parent listen any rdma_id_private and listen_item is on child listen that
is bound to a specific cma_dev.

Which name should be used in which case depends on the state and other
factors of the rdma_id_private. Remap all the confusing references to make
sense with the new names, so at least there is some hope of matching the
necessary preconditions with each access.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/core/cma.c

···
 	id_priv->id.device = cma_dev->device;
 	id_priv->id.route.addr.dev_addr.transport =
 		rdma_node_get_transport(cma_dev->device->node_type);
-	list_add_tail(&id_priv->list, &cma_dev->id_list);
+	list_add_tail(&id_priv->device_item, &cma_dev->id_list);
 
 	trace_cm_id_attach(id_priv, cma_dev->device);
 }
···
 static void cma_release_dev(struct rdma_id_private *id_priv)
 {
 	mutex_lock(&lock);
-	list_del(&id_priv->list);
+	list_del_init(&id_priv->device_item);
 	cma_dev_put(id_priv->cma_dev);
 	id_priv->cma_dev = NULL;
 	id_priv->id.device = NULL;
···
 	init_completion(&id_priv->comp);
 	refcount_set(&id_priv->refcount, 1);
 	mutex_init(&id_priv->handler_mutex);
+	INIT_LIST_HEAD(&id_priv->device_item);
 	INIT_LIST_HEAD(&id_priv->listen_list);
 	INIT_LIST_HEAD(&id_priv->mc_list);
 	get_random_bytes(&id_priv->seq_num, sizeof id_priv->seq_num);
···
 				return id_priv;
 			list_for_each_entry(id_priv_dev,
 					    &id_priv->listen_list,
-					    listen_list) {
+					    listen_item) {
 				if (id_priv_dev->id.device == cm_id->device &&
 				    cma_match_net_dev(&id_priv_dev->id,
 						      net_dev, req))
···
 	 * Remove from listen_any_list to prevent added devices from spawning
 	 * additional listen requests.
 	 */
-	list_del(&id_priv->list);
+	list_del_init(&id_priv->listen_any_item);
 
 	while (!list_empty(&id_priv->listen_list)) {
-		dev_id_priv = list_entry(id_priv->listen_list.next,
-					 struct rdma_id_private, listen_list);
+		dev_id_priv =
+			list_first_entry(&id_priv->listen_list,
+					 struct rdma_id_private, listen_item);
 		/* sync with device removal to avoid duplicate destruction */
-		list_del_init(&dev_id_priv->list);
-		list_del(&dev_id_priv->listen_list);
+		list_del_init(&dev_id_priv->device_item);
+		list_del_init(&dev_id_priv->listen_item);
 		mutex_unlock(&lock);
 
 		rdma_destroy_id(&dev_id_priv->id);
···
 	ret = rdma_listen(&dev_id_priv->id, id_priv->backlog);
 	if (ret)
 		goto err_listen;
-	list_add_tail(&dev_id_priv->listen_list, &id_priv->listen_list);
+	list_add_tail(&dev_id_priv->listen_item, &id_priv->listen_list);
 	return 0;
 err_listen:
 	/* Caller must destroy this after releasing lock */
···
 	int ret;
 
 	mutex_lock(&lock);
-	list_add_tail(&id_priv->list, &listen_any_list);
+	list_add_tail(&id_priv->listen_any_item, &listen_any_list);
 	list_for_each_entry(cma_dev, &dev_list, list) {
 		ret = cma_listen_on_dev(id_priv, cma_dev, &to_destroy);
 		if (ret) {
 			/* Prevent racing with cma_process_remove() */
 			if (to_destroy)
-				list_del_init(&to_destroy->list);
+				list_del_init(&to_destroy->device_item);
 			goto err_listen;
 		}
 	}
···
 
 	mutex_lock(&lock);
 	list_for_each_entry(cma_dev, &dev_list, list)
-		list_for_each_entry(id_priv, &cma_dev->id_list, list) {
+		list_for_each_entry(id_priv, &cma_dev->id_list, device_item) {
 			ret = cma_netdev_change(ndev, id_priv);
 			if (ret)
 				goto out;
···
 	mutex_lock(&lock);
 	while (!list_empty(&cma_dev->id_list)) {
 		struct rdma_id_private *id_priv = list_first_entry(
-			&cma_dev->id_list, struct rdma_id_private, list);
+			&cma_dev->id_list, struct rdma_id_private, device_item);
 
-		list_del(&id_priv->listen_list);
-		list_del_init(&id_priv->list);
+		list_del_init(&id_priv->listen_item);
+		list_del_init(&id_priv->device_item);
 		cma_id_get(id_priv);
 		mutex_unlock(&lock);
 
···
 
 	mutex_lock(&lock);
 	list_add_tail(&cma_dev->list, &dev_list);
-	list_for_each_entry(id_priv, &listen_any_list, list) {
+	list_for_each_entry(id_priv, &listen_any_list, listen_any_item) {
 		ret = cma_listen_on_dev(id_priv, cma_dev, &to_destroy);
 		if (ret)
 			goto free_listen;

drivers/infiniband/core/cma_priv.h

···
 
 	struct rdma_bind_list	*bind_list;
 	struct hlist_node	node;
-	struct list_head	list; /* listen_any_list or cma_device.list */
-	struct list_head	listen_list; /* per device listens */
+	union {
+		struct list_head device_item; /* On cma_device->id_list */
+		struct list_head listen_any_item; /* On listen_any_list */
+	};
+	union {
+		/* On rdma_id_private->listen_list */
+		struct list_head listen_item;
+		struct list_head listen_list;
+	};
 	struct cma_device	*cma_dev;
 	struct list_head	mc_list;