Re: [PATCH -next 0/6] mm: make pinned_vm atomic and simplify users

[Davidlohr Bueso]

Also Ccing lkml, sorry.

On Tue, 15 Jan 2019, Davidlohr Bueso wrote:

> Hi,
>
> The following patches aim to provide cleanups to users that pin pages
> (mostly infiniband) by converting the counter to atomic -- note that
> Daniel Jordan also has patches[1] for the locked_vm counterpart and vfio.
>
> Apart from removing a source of mmap_sem writer, we benefit in that
> we can get rid of a lot of code that defers work when the lock cannot
> be acquired, as well as drivers avoiding mmap_sem altogether by also
> converting gup to gup_fast() and letting the mm handle it. Users
> that do the gup_longterm() remain of course under at least reader mmap_sem.
>
> Everything has been compile-tested _only_ so I hope I didn't do anything
> too stupid. Please consider for v5.1.
>
> On a similar topic and potential follow up, it would be nice to resurrect
> Peter's VM_PINNED idea in that the broken semantics that occurred after
> bc3e53f682 ("mm: distinguish between mlocked and pinned pages") are still
> present. Also encapsulating internal mm logic via mm[un]pin() instead of
> drivers having to know about internals and playing nice with compaction are
> all wins.
>
> Thanks!
>
> [1] https://lkml.org/lkml/2018/11/5/854
>
> Davidlohr Bueso (6):
>  mm: make mm->pinned_vm an atomic counter
>  mic/scif: do not use mmap_sem
>  drivers/IB,qib: do not use mmap_sem
>  drivers/IB,hfi1: do not se mmap_sem
>  drivers/IB,usnic: reduce scope of mmap_sem
>  drivers/IB,core: reduce scope of mmap_sem
>
> drivers/infiniband/core/umem.c              | 47 +++-----------------
> drivers/infiniband/hw/hfi1/user_pages.c     | 12 ++---
> drivers/infiniband/hw/qib/qib_user_pages.c  | 69 ++++++++++-------------------
> drivers/infiniband/hw/usnic/usnic_ib_main.c |  2 -
> drivers/infiniband/hw/usnic/usnic_uiom.c    | 56 +++--------------------
> drivers/infiniband/hw/usnic/usnic_uiom.h    |  1 -
> drivers/misc/mic/scif/scif_rma.c            | 38 +++++-----------
> fs/proc/task_mmu.c                          |  2 +-
> include/linux/mm_types.h                    |  2 +-
> kernel/events/core.c                        |  8 ++--
> kernel/fork.c                               |  2 +-
> mm/debug.c                                  |  3 +-
> 12 files changed, 57 insertions(+), 185 deletions(-)
>
> --
> 2.16.4