linux-kernel - Re: [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added memory range

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Message-ID: <YFssRr7gZEPfHieA@dhcp22.suse.cz>
Date:   Wed, 24 Mar 2021 13:10:46 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Pavel Tatashin <pasha.tatashin@...een.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] mm,memory_hotplug: Allocate memmap from the added
 memory range

On Wed 24-03-21 13:03:29, Michal Hocko wrote:
> On Wed 24-03-21 11:12:59, Oscar Salvador wrote:
[...]

an additional remark

> > - online_pages()->move_pfn_range_to_zone(): Accounts for node/zone's spanned pages
> > - online_pages()->zone->present_pages += nr_pages;

I am pretty sure you shouldn't account vmmemmap pages to the target zone
in some cases - e.g. vmemmap cannot be part of the movable zone, can it?
So this would be yet another special casing. This patch has got it wrong
unless I have missed some special casing.
-- 
Michal Hocko
SUSE Labs