linux-kernel - Re: [RFC PATCH v2] mm: initialize struct pages reserved by ZONE

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Date:   Tue, 10 Sep 2019 16:01:07 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Toshiki Fukasawa <t-fukasawa@...jp.nec.com>
Cc:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "adobriyan@...il.com" <adobriyan@...il.com>,
        "hch@....de" <hch@....de>,
        "longman@...hat.com" <longman@...hat.com>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "mst@...hat.com" <mst@...hat.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Junichi Nomura <j-nomura@...jp.nec.com>
Subject: Re: [RFC PATCH v2] mm: initialize struct pages reserved by
 ZONE_DEVICE driver.

On Fri 06-09-19 08:09:52, Toshiki Fukasawa wrote:
[...]
> @@ -5856,8 +5855,6 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>  		if (!altmap)
>  			return;
>  
> -		if (start_pfn == altmap->base_pfn)
> -			start_pfn += altmap->reserve;
>  		end_pfn = altmap->base_pfn + vmem_altmap_offset(altmap);

Who is actually setting reserve? This is is something really impossible
to grep for in the kernle and git grep on altmap->reserve doesn't show
anything AFAICS.

Btw. irrespective to this issue all three callers should be using
pfn_to_online_page rather than pfn_to_page AFAICS. It doesn't really
make sense to collect data for offline pfn ranges. They might be
uninitialized even without zone device.
-- 
Michal Hocko
SUSE Labs