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Date:   Mon, 28 Jan 2019 09:50:54 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Mikhail Zaslonko <zaslonko@linux.ibm.com>,
        Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>,
        Pavel Tatashin <pasha.tatashin@soleen.com>,
        schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
        gerald.schaefer@de.ibm.com, <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/2] mm, memory_hotplug: fix uninitialized pages
 fallouts.
Message-Id: <20190128095054.4103093dec81f1c904df7929@linux-foundation.org>
In-Reply-To: <20190128144506.15603-1-mhocko@kernel.org>
References: <20190128144506.15603-1-mhocko@kernel.org>
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On Mon, 28 Jan 2019 15:45:04 +0100 Michal Hocko <mhocko@kernel.org> wrote:

> Mikhail has posted fixes for the two bugs quite some time ago [1]. I
> have pushed back on those fixes because I believed that it is much
> better to plug the problem at the initialization time rather than play
> whack-a-mole all over the hotplug code and find all the places which
> expect the full memory section to be initialized. We have ended up with
> 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full
> memory section") merged and cause a regression [2][3]. The reason is
> that there might be memory layouts when two NUMA nodes share the same
> memory section so the merged fix is simply incorrect.
> 
> In order to plug this hole we really have to be zone range aware in
> those handlers. I have split up the original patch into two. One is
> unchanged (patch 2) and I took a different approach for `removable'
> crash. It would be great if Mikhail could test it still works for his
> memory layout.
> 
> [1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com
> [2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948
> [3] http://lkml.kernel.org/r/20190125163938.GA20411@dhcp22.suse.cz

Any thoughts on which kernel version(s) need these patches?