linux-kernel - Re: 4.19.5 and later has tons of false messages "BUG: non-zero pgtables

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Date:   Thu, 27 Dec 2018 10:28:56 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        stable@...r.kernel.org, linux-s390 <linux-s390@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Cc:     Sasha Levin <sashal@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: 4.19.5 and later has tons of false messages "BUG: non-zero
 pgtables_bytes on freeing mm: -16384"



On 27.12.2018 10:13, Christian Borntraeger wrote:
> Martin,
> 
> Right now you get a message 
> "BUG: non-zero pgtables_bytes on freeing mm: -16384"
> for EVERY process that exits in 4.19.5 and later.
> 
> bisect points to 
> commit 4136161d676a93fc8df6bdb80d720c15522d6c24
> Author: Martin Schwidefsky <schwidefsky@...ibm.com>
> Date:   Mon Oct 15 11:09:16 2018 +0200
> 
>     s390/mm: fix mis-accounting of pgtable_bytes
>     
>     [ Upstream commit e12e4044aede97974f2222eb7f0ed726a5179a32 ]
> 
> Turns out that this patch requires several dependencies so the autoselection of this
> patch was missing that. 
> 
> Can we either revert this patch or add the dependencies?
> 
> Christian
> 

It seems that adding 

commit 6d212db11947ae5464e4717536ed9faf61c01e86 ("mm: add mm_pxd_folded checks to pgtable_bytes accounting functions") 
fixes the issue. 

Martin, do we need more?

Christian