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Message-ID: <dbd0f54a-ad6c-97a2-17d7-826247424c97@suse.cz>
Date:   Wed, 25 Aug 2021 13:15:20 +0200
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Subject: Re: [PATCH v1 02/14] mm: remove extra ZONE_DEVICE struct page
 refcount
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To:     Alex Sierra <alex.sierra@amd.com>, akpm@linux-foundation.org,
        Felix.Kuehling@amd.com, linux-mm@kvack.org, rcampbell@nvidia.com,
        linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org
Cc:     amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        hch@lst.de, jgg@nvidia.com, jglisse@redhat.com
References: <20210825034828.12927-1-alex.sierra@amd.com>
 <20210825034828.12927-3-alex.sierra@amd.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <20210825034828.12927-3-alex.sierra@amd.com>
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On 8/25/21 05:48, Alex Sierra 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.

That's certainly welcome. I just wonder what was the reason to use 1 in the
first place and why it's no longer necessary?