On Wed, Feb 13, 2019 at 05:53:14PM -0800, Ira Weiny wrote: > On Mon, Feb 11, 2019 at 03:54:47PM -0700, Jason Gunthorpe wrote: > > On Mon, Feb 11, 2019 at 05:44:32PM -0500, Daniel Jordan wrote: > > > > > All five of these places, and probably some of Davidlohr's conversions, > > > probably want to be collapsed into a common helper in the core mm for > > > accounting pinned pages. I tried, and there are several details that > > > likely need discussion, so this can be done as a follow-on. > > > > I've wondered the same.. > > I'm really thinking this would be a nice way to ensure it gets cleaned up and > does not happen again. > > Also, by moving it to the core we could better manage any user visible changes. > > From a high level, pinned is a subset of locked so it seems like we need a 2 > sets of helpers. > > try_increment_locked_vm(...) > decrement_locked_vm(...) > > try_increment_pinned_vm(...) > decrement_pinned_vm(...) > > Where try_increment_pinned_vm() also increments locked_vm... Of course this > may end up reverting the improvement of Davidlohr Bueso's atomic work... :-( > > Furthermore it would seem better (although I don't know if at all possible) if > this were accounted for in core calls which tracked them based on how the pages > are being used so that drivers can't call try_increment_locked_vm() and then > pin the pages... Thus getting the account wrong vs what actually happened. > > And then in the end we can go back to locked_vm being the value checked against > RLIMIT_MEMLOCK. Someone would need to understand the bug that was fixed by splitting them. I think it had to do with double accounting pinned and mlocked pages and thus delivering a lower than expected limit to userspace. vfio has this bug, RDMA does not. RDMA has a bug where it can overallocate locked memory, vfio doesn't. Really unclear how to fix this. The pinned/locked split with two buckets may be the right way. Jason
