On Fri, Oct 13, 2017 at 9:38 AM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote: > On Fri, Oct 13, 2017 at 08:14:55AM -0700, Dan Williams wrote: > >> scheme specific to RDMA which seems like a waste to me when we can >> generically signal an event on the fd for any event that effects any >> of the vma's on the file. The FL_LAYOUT lease impacts the entire file, >> so as far as I can see delaying the notification until MR-init is too >> late, too granular, and too RDMA specific. > > But for RDMA a FD is not what we care about - we want the MR handle so > the app knows which MR needs fixing. I'd rather put the onus on userspace to remember where it used a MAP_DIRECT mapping and be aware that all the mappings of that file are subject to a lease break. Sure, we could build up a pile of kernel infrastructure to notify on a per-MR basis, but I think that would only be worth it if leases were range based. As it is, the entire file is covered by a lease instance and all MRs that might reference that file get one notification. That said, we can always arrange for a per-driver callback at lease-break time so that it can do something above and beyond the default notification.
