On Fri, Oct 09, 2020 at 11:00:22AM -0400, Chuck Lever wrote: > > > > On Oct 9, 2020, at 10:57 AM, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > On Fri, Oct 09, 2020 at 10:48:55AM -0400, Chuck Lever wrote: > >> Hi Jason- > >> > >>> On Oct 9, 2020, at 10:39 AM, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > >>> > >>> On Fri, Oct 09, 2020 at 12:49:30PM +0800, Ka-Cheong Poon wrote: > >>>> As I mentioned before, this is a very serious restriction on how > >>>> the RDMA subsystem can be used in a namespace environment by kernel > >>>> module. The reason given for this restriction is that any kernel > >>>> socket without a corresponding user space file descriptor is "rogue". > >>>> All Internet protocol code create a kernel socket without user > >>>> interaction. Are they all "rogue"? > >>> > >>> You should work with Chuck to make NFS use namespaces properly and > >>> then you can propose what changes might be needed with a proper > >>> justification. > >> > >> The NFS server code already uses namespaces for creating listener > >> endpoints, already has a user space component that drives the > >> creation of listeners, and already passes an appropriate struct > >> net to rdma_create_id. As far as I am aware, it is namespace-aware > >> and -friendly all the way down to rdma_create_id(). > >> > >> What more needs to be done? > > > > I have no idea, if you are able to pass a namespace all the way down > > to the listening cm_id and everything works right (I'm skeptical) then > > there is nothing more to worry about - why are we having this thread? > > The thread is about RDS, not NFS. NFS has some useful examples to > crib, but it's not the main point. > > I don't think NFS/RDMA namespacing works today, but it's not because > NFS isn't ready. I agree that is another thread. Exactly, so instead of talking about RDS stuff without any patches, let's talk about NFS with patches - if you can make NFS work then I assume RDS will be happy. NFS has an established model for using namespaces that the other transports uses, so I'd rather focus on this. > >>> The rules for lifetime on IB clients are tricky, and the interaction > >>> with namespaces makes it all a lot more murky. > >> > >> I think what Ka-cheong is asking is for a detailed explanation of > >> these lifetime rules so we can understand why rdma_create_id bumps > >> the namespace reference count. > > > > It is because the CM has no code to revoke a CM ID before the > > namespace goes away and the pointer becomes invalid. > > Is it just a question of "no-one has yet written this code" or is > there a deeper technical reason why this has not been done? It is hard to know without spending a big deep look at this stuff. Jason
