[PATCH v2 -next 0/6] mm: make pinned_vm atomic and simplify users

Davidlohr Bueso
2019-01-21T17:42:50Z

Changes from v1 (https://patchwork.kernel.org/cover/10764923/):
- Converted pinned_vm to atomic64 instead of atomic_long such that
infiniband need not worry about overflows.

- Rebased patch 1 and added Ira's reviews as well as Parvi's review
for patch 5 (thanks!).

--------

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 atomic64 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