linux-kernel - Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing memory

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Date:   Fri, 30 Aug 2019 08:20:32 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Wei Yang <richardw.yang@...ux.intel.com>
Subject: Re: [PATCH v2 3/6] mm/memory_hotplug: Process all zones when removing
 memory

On 30.08.19 08:01, Michal Hocko wrote:
> On Thu 29-08-19 18:59:31, David Hildenbrand wrote:
>> On 29.08.19 18:27, Michal Hocko wrote:
> [...]
>>> No rush, really... It seems this is quite unlikely event as most hotplug
>>> usecases simply online memory before removing it later on.
>>>
>>
>> I can trigger it reliably right now while working/testing virtio-mem, so
>> I finally want to clean up this mess :) (has been on my list for a long
>> time). I'll try to hunt for the right commit id's that broke it.
> 
> f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to
> zones until online")
> 

Right, I can see that that commit still does a

set_page_node(page, nid);
SetPageReserved(page);

for every added page. But of course the zone_idx might contain garbage.
So for this garbage pointer, f1dd2cd13c4b seems to be the right one.

Regarding shrink_zone_span(), I suspect it was introduced by

d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug")

-- 

Thanks,

David / dhildenb