linux-kernel - Re: [PATCH] mm, zone_device: replace {get, put}_zone_device

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Date:   Thu, 27 Apr 2017 10:33:37 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Jérôme Glisse <jglisse@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH] mm, zone_device: replace {get, put}_zone_device_page()
 with a single reference



On 27/04/17 10:14 AM, Dan Williams wrote:
> You're overlooking that the page reference count 1 after
> arch_add_memory(). So at the end of time we're just dropping the
> arch_add_memory() reference to release the page and related
> dev_pagemap.

Thanks, that does actually make a lot more sense to me now. However,
there still appears to be an asymmetry in that the pgmap->ref is
incremented once and decremented once per page...

Logan