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 <YeBFxBwaHtfs8jmg@dhcp22.suse.cz>
In-Reply-To: <YeBFxBwaHtfs8jmg@dhcp22.suse.cz>
From:   Xiongwei Song <sxwjean@gmail.com>
Date:   Fri, 14 Jan 2022 18:03:04 +0800
Message-ID: <CAEVVKH-L-6Yra75XEWUNiq=ajJmtWauDTcmN=b1VCcJ0NVS7OA@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] proc: Add getting pages info of ZONE_DEVICE support
To:     Michal Hocko <mhocko@suse.com>
Cc:     Xiongwei Song <sxwjean@me.com>, akpm@linux-foundation.org,
        David Hildenbrand <david@redhat.com>, dan.j.williams@intel.com,
        osalvador@suse.de, naoya.horiguchi@nec.com,
        thunder.leizhen@huawei.com, linux-mm@kvack.org,
        linux-fsdevel@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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HI Michal,

On Thu, Jan 13, 2022 at 11:31 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Wed 12-01-22 22:35:17, sxwjean@me.com wrote:
> > From: Xiongwei Song <sxwjean@gmail.com>
> >
> > When requesting pages info by /proc/kpage*, the pages in ZONE_DEVICE were
> > ignored.
> >
> > The pfn_to_devmap_page() function can help to get page that belongs to
> > ZONE_DEVICE.
>
> Why is this needed? Who would consume that information and what for?

It's for debug purpose, which checks page flags in system wide. No any other
special thought. But it looks like it's not appropriate to expose now from my
understand, which is from David's comment.
https://lore.kernel.org/linux-mm/20220110141957.259022-1-sxwjean@me.com/T/#m4eccbb2698dbebc80ec00be47382b34b0f64b4fc

Regards,
Xingwei