Re: [PATCH] Delay the initialization of rnbd_server module to late_initcall level

[Leon Romanovsky <leon@kernel.org>]

On Wed, Jun 17, 2020 at 04:07:32PM +0530, haris.iqbal@cloud.ionos.com wrote:
> From: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
>
> Fixes: 2de6c8de192b ("block/rnbd: server: main functionality")
> Reported-by: kernel test robot <rong.a.chen@intel.com>
> Signed-off-by: Md Haris Iqbal <haris.iqbal@cloud.ionos.com>
>
> The rnbd_server module's communication manager initialization depends on the
> registration of the "network namespace subsystem" of the RDMA CM agent module.
> As such, when the kernel is configured to load the rnbd_server and the RDMA
> cma module during initialization; and if the rnbd_server module is initialized
> before RDMA cma module, a null ptr dereference occurs during the RDMA bind
> operation.
> This patch delays the initialization of the rnbd_server module to the
> late_initcall level, since RDMA cma module uses module_init which puts it into
> the device_initcall level.
> ---
>  drivers/block/rnbd/rnbd-srv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/rnbd/rnbd-srv.c b/drivers/block/rnbd/rnbd-srv.c
> index 86e61523907b..213df05e5994 100644
> --- a/drivers/block/rnbd/rnbd-srv.c
> +++ b/drivers/block/rnbd/rnbd-srv.c
> @@ -840,5 +840,5 @@ static void __exit rnbd_srv_cleanup_module(void)
>  	rnbd_srv_destroy_sysfs_files();
>  }
>
> -module_init(rnbd_srv_init_module);
> +late_initcall(rnbd_srv_init_module);

I don't think that this is correct change. Somehow nvme-rdma works:
module_init(nvme_rdma_init_module);
-> nvme_rdma_init_module
 -> nvmf_register_transport(&nvme_rdma_transport);
  -> nvme_rdma_create_ctrl
   -> nvme_rdma_setup_ctrl
    -> nvme_rdma_configure_admin_queue
     -> nvme_rdma_alloc_queue
      -> rdma_create_id

>  module_exit(rnbd_srv_cleanup_module);
> --
> 2.25.1
>