nvme-rdma: fix a segmentation fault during module unload

In case there are controllers that are not associated with any RDMA
device (e.g. during unsuccessful reconnection) and the user will unload
the module, these controllers will not be freed and will access already
freed memory. The same logic appears in other fabric drivers as well.

Fixes: 87fd1253 ("nvme-rdma: remove redundant reference between ib_device and tagset")
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/rdma.c

@@ -2133,8 +2133,16 @@ static int __init nvme_rdma_init_module(void)
 
 static void __exit nvme_rdma_cleanup_module(void)
 {
+	struct nvme_rdma_ctrl *ctrl;
+
 	nvmf_unregister_transport(&nvme_rdma_transport);
 	ib_unregister_client(&nvme_rdma_ib_client);
+
+	mutex_lock(&nvme_rdma_ctrl_mutex);
+	list_for_each_entry(ctrl, &nvme_rdma_ctrl_list, list)
+		nvme_delete_ctrl(&ctrl->ctrl);
+	mutex_unlock(&nvme_rdma_ctrl_mutex);
+	flush_workqueue(nvme_delete_wq);
 }
 
 module_init(nvme_rdma_init_module);