linux-kernel - Re: [PATCH v3 3/6] mm: support THP migration to device private memory

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Date:   Fri, 6 Nov 2020 13:26:50 -0800
From:   Ralph Campbell <rcampbell@...dia.com>
To:     Christoph Hellwig <hch@....de>
CC:     <linux-mm@...ck.org>, <nouveau@...ts.freedesktop.org>,
        <linux-kselftest@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Jerome Glisse" <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        "Alistair Popple" <apopple@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        Zi Yan <ziy@...dia.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        Ben Skeggs <bskeggs@...hat.com>, Shuah Khan <shuah@...nel.org>,
        "Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 3/6] mm: support THP migration to device private memory

On 11/6/20 12:03 AM, Christoph Hellwig wrote:
> I hate the extra pin count magic here.  IMHO we really need to finish
> off the series to get rid of the extra references on the ZONE_DEVICE
> pages first.

First, thanks for the review comments.

I don't like the extra refcount either, that is why I tried to fix that up
before resending this series. However, you didn't like me just fixing the
refcount only for device private pages and I don't know the dax/pmem code
and peer-to-peer PCIe uses of ZONE_DEVICE pages well enough to say how
long it will take me to fix all the use cases.
So I wanted to make progress on the THP migration code in the mean time.