Re: [PATCH v5 02/24] mm: remove extra ZONE_DEVICE struct page refcount

[Ralph Campbell]

On 1/28/22 06:21, Jason Gunthorpe wrote:
> On Thu, Jan 27, 2022 at 05:25:52PM -0700, Logan Gunthorpe wrote:
> > From: Ralph Campbell <rcampbell@xxxxxxxxxx>
> >
> > ZONE_DEVICE struct pages have an extra reference count that complicates the
> > code for put_page() and several places in the kernel that need to check the
> > reference count to see that a page is not being used (gup, compaction,
> > migration, etc.). Clean up the code so the reference count doesn't need to
> > be treated specially for ZONE_DEVICE.
> >
> > [logang: dropped no longer used section from mm.h including
> >   page_is_devmap_managed, rebased on v5.17-rc1 (possibly poorly)]
> > Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
> > Signed-off-by: Alex Sierra <alex.sierra@xxxxxxx>
> > Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> > Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> > ---
> >   arch/powerpc/kvm/book3s_hv_uvmem.c     |  2 +-
> >   drivers/gpu/drm/nouveau/nouveau_dmem.c |  2 +-
> >   fs/dax.c                               |  4 +-
> >   include/linux/dax.h                    |  2 +-
> >   include/linux/memremap.h               |  7 +--
> >   include/linux/mm.h                     | 44 ----------------
> >   lib/test_hmm.c                         |  2 +-
> >   mm/internal.h                          |  8 +++
> >   mm/memcontrol.c                        |  6 +--
> >   mm/memremap.c                          | 70 +++++++-------------------
> >   mm/migrate.c                           |  5 --
> >   mm/page_alloc.c                        |  3 ++
> >   mm/swap.c                              | 45 ++---------------
> >   13 files changed, 46 insertions(+), 154 deletions(-)
> This patch still can't be applied until the FSDAX issues are solved,
> right? See my remarks the last time it was posted..
>
> Jason

That is my understanding too.