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

[Logan Gunthorpe]

On 2022-01-28 7:21 a.m., 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..

Yes. As I mentioned in the cover, this is just to show that this
patchset is compatible with the direction this patch goes.

Logan