[PATCHv3] nvme: use srcu for iterating namespace list

[Christoph Hellwig]

> -static inline bool nvme_get_ns(struct nvme_ns *ns)
> +bool nvme_get_ns(struct nvme_ns *ns)
>  {
>  	return kref_get_unless_zero(&ns->kref);
>  }
> +EXPORT_SYMBOL_NS_GPL(nvme_get_ns, NVME_TARGET_PASSTHRU);

What actually needs the export in nvmet?  AFAICS the export only grows
a new user in ioctl.c.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch at lst.de>