Re: RDMA subsystem namespace related questions (was Re: Finding the namespace of a struct ib_device)

[Jason Gunthorpe <jgg@ziepe.ca>]

On Fri, Oct 09, 2020 at 11:27:44AM -0400, Chuck Lever wrote:

> Therefore I think the approach is going to be "one RDS listener per
> net namespace". The problem Ka-Cheong is trying to address is how to
> manage the destruction of a listener-namespace pair. The extra
> reference count on the cm_id is pinning the namespace so it cannot
> be destroyed.

I really don't think this idea of just loading a kernel module and it
immediately creates a network visibile listening socket in every
namespace is very good.

> Understood, but it doesn't seem like there is enough useful overlap
> between the NFS and RDS usage scenarios. With NFS, I would expect
> an explicit listener shutdown from userland prior to namespace
> destruction.

Yes, because namespaces are fundamentally supposed to be anchored in
the processes inside the namespace.

Having the kernel jump in and start opening holes as soon as a
namespace is created is just wrong.

At a bare minimum the listener should not exist until something in the
namespace is willing to work with RDS.

Jason