On Wed, Aug 14, 2019 at 09:23:08AM -0300, Jason Gunthorpe wrote: > On Tue, Aug 13, 2019 at 01:38:59PM -0700, Ira Weiny wrote: > > On Tue, Aug 13, 2019 at 03:00:22PM -0300, Jason Gunthorpe wrote: > > > On Tue, Aug 13, 2019 at 10:41:42AM -0700, Ira Weiny wrote: > > > > > > > And I was pretty sure uverbs_destroy_ufile_hw() would take care of (or ensure > > > > that some other thread is) destroying all the MR's we have associated with this > > > > FD. > > > > > > fd's can't be revoked, so destroy_ufile_hw() can't touch them. It > > > deletes any underlying HW resources, but the FD persists. > > > > I misspoke. I should have said associated with this "context". And of course > > uverbs_destroy_ufile_hw() does not touch the FD. What I mean is that the > > struct file which had file_pins hanging off of it would be getting its file > > pins destroyed by uverbs_destroy_ufile_hw(). Therefore we don't need the FD > > after uverbs_destroy_ufile_hw() is done. > > > > But since it does not block it may be that the struct file is gone before the > > MR is actually destroyed. Which means I think the GUP code would blow up in > > that case... :-( > > Oh, yes, that is true, you also can't rely on the struct file living > longer than the HW objects either, that isn't how the lifetime model > works. Reviewing all these old threads... And this made me think. While the HW objects may out live the struct file. They _are_ going away in a finite amount of time right? It is not like they could be held forever right? Ira > > If GUP consumes the struct file it must allow the struct file to be > deleted before the GUP pin is released. > > > The drivers could provide some generic object (in RDMA this could be the > > uverbs_attr_bundle) which represents their "context". > > For RDMA the obvious context is the struct ib_mr * > > > But for the procfs interface, that context then needs to be associated with any > > file which points to it... For RDMA, or any other "FD based pin mechanism", it > > would be up to the driver to "install" a procfs handler into any struct file > > which _may_ point to this context. (before _or_ after memory pins). > > Is this all just for debugging? Seems like a lot of complication just > to print a string > > Generally, I think you'd be better to associate things with the > mm_struct not some struct file... The whole design is simpler as GUP > already has the mm_struct. > > Jason
