linux-kernel - Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable

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Message-Id: <20181031100944.GA3546@osiris>
Date:   Wed, 31 Oct 2018 11:09:44 +0100
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Li Wang <liwang@...hat.com>, Guenter Roeck <linux@...ck-us.net>,
        Janosch Frank <frankja@...ux.vnet.ibm.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes

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.