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Message-ID: <90168b70-cd15-9eb8-b782-9200b174a046@nvidia.com>
Date:   Fri, 28 Jan 2022 09:16:25 -0800
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Subject: Re: [PATCH v5 02/24] mm: remove extra ZONE_DEVICE struct page
 refcount
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To:     Jason Gunthorpe <jgg@ziepe.ca>,
        Logan Gunthorpe <logang@deltatee.com>
Cc:     linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org,
        Stephen Bates <sbates@raithlin.com>,
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        Jakowski Andrzej <andrzej.jakowski@intel.com>,
        Minturn Dave B <dave.b.minturn@intel.com>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Xiong Jianxin <jianxin.xiong@intel.com>,
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        Martin Oliveira <martin.oliveira@eideticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@gmail.com>,
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References: <20220128002614.6136-1-logang@deltatee.com>
 <20220128002614.6136-3-logang@deltatee.com> <20220128142138.GU8034@ziepe.ca>
From:   Ralph Campbell <rcampbell@nvidia.com>
In-Reply-To: <20220128142138.GU8034@ziepe.ca>
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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@nvidia.com>
>>
>> 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@nvidia.com>
>> Signed-off-by: Alex Sierra <alex.sierra@amd.com>
>> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> ---
>>   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.