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Date:   Fri, 3 Nov 2017 12:20:49 +0300
From:   "Kirill A. Shutemov" <>
To:     Heiko Carstens <>
Cc:     Andrew Morton <>,,,,, Michal Hocko <>,
        Gerald Schaefer <>,
        Martin Schwidefsky <>
Subject: Re: [PATCH] s390/mm: fix pud table accounting

On Fri, Nov 03, 2017 at 09:05:51AM +0000, Heiko Carstens wrote:
> With "mm: account pud page tables" and "mm: consolidate page table
> accounting" pud page table accounting was introduced which now results
> in tons of warnings like this one on s390:
> BUG: non-zero pgtables_bytes on freeing mm: -16384
> Reason for this are our run-time folded page tables: by default new
> processes start with three page table levels where the allocated pgd
> is the same as the first pud. In this case there won't ever be a pud
> allocated and therefore mm_inc_nr_puds() will also never be called.
> However when freeing the address space free_pud_range() will call
> exactly once mm_dec_nr_puds() which leads to misaccounting.
> Therefore call mm_inc_nr_puds() within init_new_context() to fix
> this. This is the same like we have it already for processes that run
> with two page table levels (aka compat processes).
> While at it also adjust the comment, since there is no "mm->nr_pmds"
> anymore.

Thanks for tracking it down.

Acked-by: Kirill A. Shutemov <>

 Kirill A. Shutemov

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