Re: [PATCH] nvme: Add module reference counting for multipath nvme device

[Keith Busch <kbusch@kernel.org>]

On Mon, Aug 10, 2026 at 07:50:34PM -0400, wenxiong@linux.ibm.com wrote:
>  static int nvme_ns_head_open(struct gendisk *disk, blk_mode_t mode)
>  {
> -	if (!nvme_tryget_ns_head(disk->private_data))
> +	struct nvme_ns_head *head = disk->private_data;
> +	struct nvme_ns *ns;
> +	int srcu_idx;
> +
> +	if (!nvme_tryget_ns_head(head))
>  		return -ENXIO;
> +
> +	/* Get module reference from any available path */
> +	srcu_idx = srcu_read_lock(&head->srcu);
> +	ns = nvme_find_path(head);
> +	if (ns && !try_module_get(ns->ctrl->ops->module)) {
> +		srcu_read_unlock(&head->srcu, srcu_idx);
> +		nvme_put_ns_head(head);
> +		return -ENXIO;
> +	}
> +	srcu_read_unlock(&head->srcu, srcu_idx);
> +
>  	return 0;
>  }
>  
>  static void nvme_ns_head_release(struct gendisk *disk)
>  {
> -	nvme_put_ns_head(disk->private_data);
> +	struct nvme_ns_head *head = disk->private_data;
> +	struct nvme_ns *ns;
> +	int srcu_idx;
> +
> +	srcu_idx = srcu_read_lock(&head->srcu);
> +	ns = nvme_find_path(head);
> +	if (ns)
> +		module_put(ns->ctrl->ops->module);
> +	srcu_read_unlock(&head->srcu, srcu_idx);
> +
> +	nvme_put_ns_head(head);
>  }

The result of nvme_find_path() is just the current path at the moment,
so I don't think this is right.

I think you need the head to hold a module reference on every path the
head has, so the module_get/put should be in nvme_mpath_add_disk and
nvme_mpath_remove_disk.