linux-kernel - Re: [PATCH] memory_hotplug: fix the panic when memory end is not on the section boundary

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Date:   Wed, 12 Sep 2018 14:21:32 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Zaslonko Mikhail <zaslonko@...ux.vnet.ibm.com>
Cc:     Mikhail Zaslonko <zaslonko@...ux.ibm.com>,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Pavel.Tatashin@...rosoft.com,
        osalvador@...e.de, gerald.schaefer@...ibm.com
Subject: Re: [PATCH] memory_hotplug: fix the panic when memory end is not on
 the section boundary

On Tue 11-09-18 16:06:23, Zaslonko Mikhail wrote:
[...]
> > Well, I am afraid this is not the proper solution. We are relying on the
> > full pageblock worth of initialized struct pages at many other place. We
> > used to do that in the past because we have initialized the full
> > section but this has been changed recently. Pavel, do you have any ideas
> > how to deal with this partial mem sections now?
> 
> I think this is not related to the recent changes of memory initialization.
> If
> you mean deferred init case, the problem exists even without
> CONFIG_DEFERRED_STRUCT_PAGE_INIT kernel option.

This is more about struct page initialization (which doesn't clear
whole) memmap area and as such it stays unitialized. So you are right
this is a much older issue we just happened to not notice without
explicit memmap poisoning.
-- 
Michal Hocko
SUSE Labs