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

[Chuck Lever <chuck.lever@oracle.com>]

> On Oct 8, 2020, at 12:08 PM, Jason Gunthorpe <jgg@ziepe.ca> wrote:
> 
> On Thu, Oct 08, 2020 at 07:08:42PM +0800, Ka-Cheong Poon wrote:
>> Note that namespace does not really play a role in this "rogue" reasoning.
>> The init_net is also a namespace.  The "rogue" reasoning means that no
>> kernel module should start a listening RDMA endpoint by itself with or
>> without any extra namespaces.  In fact, to conform to this reasoning, the
>> "right" thing to do would be to change the code already in upstream to get
>> rid of the listening RDMA endpoint in init_net!
> 
> Actually I think they all already need user co-ordination?
> 
> - NFS, user has to setup and load exports
> - Storage Targets, user has to setup the target
> - IPoIB, user has to set the link up
> 
> etc.
> 
> Each of those could provide the anchor to learn the namespace.

My two cents, and worth every penny:

I think the NFSD listener is net namespace-aware. I vaguely recall
that a user administrative program (maybe rpc.nfsd?) requests an
NFS service listener in a particular namespace.

Should work the same for sockets and listener QPs. For RPC-over-RDMA,
a struct net argument is passed in from the generic code:

 66 static struct svcxprt_rdma *svc_rdma_create_xprt(struct svc_serv *serv,
 67                                                  struct net *net);
 68 static struct svc_xprt *svc_rdma_create(struct svc_serv *serv,
 69                                         struct net *net,
 70                                         struct sockaddr *sa, int salen,
 71                                         int flags);

And that struct net is then passed on to rdma_create_id().


--
Chuck Lever