> 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. >>> 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? -- Chuck Lever chucklever@xxxxxxxxx
