start sorting out the ZONE_DEVICE refcount mess v2

[Christoph Hellwig]

Hi all,

this series removes the offset by one refcount for ZONE_DEVICE pages
that are freed back to the driver owning them, which is just device
private ones for now, but also the planned device coherent pages
and the ehanced p2p ones pending.

It does not address the fsdax pages yet, which will be attacked in a
follow on series.

Note that if we want to get the p2p series rebased on top of this
we'll need a git branch for this series.  I could offer to host one.

A git tree is available here:

    git://git.infradead.org/users/hch/misc.git pgmap-refcount

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/pgmap-refcount

Changes since v1:
 - add a missing memremap.h include in memcontrol.c
 - include rebased versions of the device coherent support and
   device coherent migration support series as well as additional
   cleanup patches

Diffstt:
 arch/arm64/mm/mmu.c                      |    1 
 arch/powerpc/kvm/book3s_hv_uvmem.c       |    1 
 drivers/gpu/drm/amd/amdkfd/kfd_migrate.c |   35 -
 drivers/gpu/drm/amd/amdkfd/kfd_priv.h    |    1 
 drivers/gpu/drm/drm_cache.c              |    2 
 drivers/gpu/drm/nouveau/nouveau_dmem.c   |    3 
 drivers/gpu/drm/nouveau/nouveau_svm.c    |    1 
 drivers/infiniband/core/rw.c             |    1 
 drivers/nvdimm/pmem.h                    |    1 
 drivers/nvme/host/pci.c                  |    1 
 drivers/nvme/target/io-cmd-bdev.c        |    1 
 fs/Kconfig                               |    2 
 fs/fuse/virtio_fs.c                      |    1 
 include/linux/hmm.h                      |    9 
 include/linux/memremap.h                 |   36 +
 include/linux/migrate.h                  |    1 
 include/linux/mm.h                       |   59 --
 lib/test_hmm.c                           |  353 ++++++++++---
 lib/test_hmm_uapi.h                      |   22 
 mm/Kconfig                               |    7 
 mm/Makefile                              |    1 
 mm/gup.c                                 |  127 +++-
 mm/internal.h                            |    3 
 mm/memcontrol.c                          |   19 
 mm/memory-failure.c                      |    8 
 mm/memremap.c                            |   75 +-
 mm/migrate.c                             |  763 ----------------------------
 mm/migrate_device.c                      |  822 +++++++++++++++++++++++++++++++
 mm/rmap.c                                |    5 
 mm/swap.c                                |   49 -
 tools/testing/selftests/vm/Makefile      |    2 
 tools/testing/selftests/vm/hmm-tests.c   |  204 ++++++-
 tools/testing/selftests/vm/test_hmm.sh   |   24 
 33 files changed, 1552 insertions(+), 1088 deletions(-)