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

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Message-Id: <babf4052-c82c-3bca-0214-4ae3f23fee4e@de.ibm.com>
Date:   Thu, 27 Dec 2018 22:06:09 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Martin Schwidefsky <schwidefsky@...ibm.com>,
        stable@...r.kernel.org, linux-s390 <linux-s390@...r.kernel.org>,
        linux-kernel@...r.kernel.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 12/27/2018 10:01 PM, Sasha Levin wrote:
> On Thu, Dec 27, 2018 at 10:28:56AM +0100, Christian Borntraeger wrote:
>>
>>
>> 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.
> 
> I've queued 6d212db11947 for 4.19 for now, thank you.

Not sure, but you might need 
1071fc5779d98 mm: introduce mm_[p4d|pud|pmd]_folded
a8874e7e8a889 mm: make the __PAGETABLE_PxD_FOLDED defines non-empty

to avoid compile errors on !s390.