linux-kernel - Re: [PATCH v3.1 4/6] mm/hugetlb: Allow architectures to override huge_pte

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Message-Id: <20170523072629.06163fa6@mschwideX1>
Date:   Tue, 23 May 2017 07:26:29 +0200
From:   Martin Schwidefsky <schwidefsky@...ibm.com>
To:     Punit Agrawal <punit.agrawal@....com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        catalin.marinas@....com, will.deacon@....com,
        n-horiguchi@...jp.nec.com, kirill.shutemov@...ux.intel.com,
        mike.kravetz@...cle.com, steve.capper@....com,
        mark.rutland@....com, linux-arch@...r.kernel.org,
        aneesh.kumar@...ux.vnet.ibm.com,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v3.1 4/6] mm/hugetlb: Allow architectures to override
 huge_pte_clear()

On Mon, 22 May 2017 17:25:55 +0100
Punit Agrawal <punit.agrawal@....com> wrote:

> When unmapping a hugepage range, huge_pte_clear() is used to clear the
> page table entries that are marked as not present. huge_pte_clear()
> internally just ends up calling pte_clear() which does not correctly
> deal with hugepages consisting of contiguous page table entries.
> 
> Add a size argument to address this issue and allow architectures to
> override huge_pte_clear() by wrapping it in a #ifndef block.
> 
> Update s390 implementation with the size parameter as well.
> 
> Note that the change only affects huge_pte_clear() - the other generic
> hugetlb functions don't need any change.
> 
> Signed-off-by: Punit Agrawal <punit.agrawal@....com>
> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> ---
> 
> Changes since v3
> 
> * Drop weak function and use #ifndef block to allow architecture override
> * Drop unnecessary move of s390 function definition
> 
>  arch/s390/include/asm/hugetlb.h | 2 +-
>  include/asm-generic/hugetlb.h   | 4 +++-
>  mm/hugetlb.c                    | 2 +-
>  3 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/include/asm/hugetlb.h b/arch/s390/include/asm/hugetlb.h
> index cd546a245c68..c0443500baec 100644
> --- a/arch/s390/include/asm/hugetlb.h
> +++ b/arch/s390/include/asm/hugetlb.h
> @@ -39,7 +39,7 @@ static inline int prepare_hugepage_range(struct file *file,
>  #define arch_clear_hugepage_flags(page)		do { } while (0)
> 
>  static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
> -				  pte_t *ptep)
> +				  pte_t *ptep, unsigned long sz)
>  {
>  	if ((pte_val(*ptep) & _REGION_ENTRY_TYPE_MASK) == _REGION_ENTRY_TYPE_R3)
>  		pte_val(*ptep) = _REGION3_ENTRY_EMPTY;

For the nop-change for s390:
Acked-by: Martin Schwidefsky <schwidefsky@...ibm.com>

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.