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

[Jason Gunthorpe <jgg@ziepe.ca>]

On Fri, Oct 16, 2020 at 04:49:41PM -0400, Chuck Lever wrote:
> 
> 
> > On Oct 16, 2020, at 2:54 PM, Jason Gunthorpe <jgg@ziepe.ca> wrote:
> > 
> > On Mon, Oct 12, 2020 at 04:20:40PM +0800, Ka-Cheong Poon wrote:
> >> On 10/9/20 11:34 PM, Jason Gunthorpe wrote:
> >> 
> >>> 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.
> >> 
> >> 
> >> As I mentioned in a previous email, starting is not the problem.  It
> >> is the problem of deleting a namespace.
> > 
> > Starting and ending are symmetric. When the last thing inside the
> > namespace stops needing RDS then RDS should close down the cm_id's.
> 
> Unfortunately, cluster heartbeat requires the RDS listener endpoint
> to continue after the last RDS user goes away, if the container
> continues to exist.

What purpose is the heartbeat if nobody is listening for RDS stuff
inside the net namespace anyhow?

> IMO having an explicit RDS start-up and shutdown apart from namespace
> creation and deletion is a cleaner approach. On a multi-tenant system
> with many containers, some of those containers will want RDS listeners
> and some will not. RDS should not assume that every net namespace
> needs or wants to have a listener.

Right

Jason