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Date: Wed, 31 Oct 2018 11:09:44 +0100
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes
References: <1539621759-5967-1-git-send-email-schwidefsky@de.ibm.com>
 <1539621759-5967-4-git-send-email-schwidefsky@de.ibm.com>
 <CAEemH2cHNFsiDqPF32K6TNn-XoXCRT0wP4ccAeah4bKHt=FKFA@mail.gmail.com>
 <20181031073149.55ddc085@mschwideX1>
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Li Wang <liwang@redhat.com>, Guenter Roeck <linux@roeck-us.net>, Janosch Frank <frankja@linux.vnet.ibm.com>, linux-kernel <linux-kernel@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>

On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote:
> Thanks for testing. Unfortunately Heiko reported another issue yesterday
> with the patch applied. This time the other way around:
> 
> BUG: non-zero pgtables_bytes on freeing mm: -16384
> 
> I am trying to understand how this can happen. For now I would like to
> keep the patch on hold in case they need another change.

FWIW, Kirill: is there a reason why this "BUG:" output is done with
pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants?

That would to get more information with DEBUG_VM and / or
panic_on_warn=1 set. At least for automated testing it would be nice
to have such triggers.