linux-kernel - Re: [PATCH] s390/mm: Use pmd_pgtable_page() helper in __gmap_segment

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Message-ID: <d3bcb8e1-cbf0-e820-47cf-f455128c597a@arm.com>
Date:   Mon, 28 Nov 2022 12:01:06 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Alexander Gordeev <agordeev@...ux.ibm.com>
Cc:     linux-mm@...ck.org,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/mm: Use pmd_pgtable_page() helper in
 __gmap_segment_gaddr()



On 11/28/22 11:37, Alexander Gordeev wrote:
> On Fri, Nov 25, 2022 at 09:15:02AM +0530, Anshuman Khandual wrote:
> 
> Hi Anshuman,
> 
>> In __gmap_segment_gaddr() pmd level page table page is being extracted from
>> the pmd pointer, similar to pmd_pgtable_page() implementation. This reduces
>> some redundancy by directly using pmd_pgtable_page() instead,  though first
>> making it available.
> 
> [...]
> 
>> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
>> index 02d15c8dc92e..8947451ae021 100644
>> --- a/arch/s390/mm/gmap.c
>> +++ b/arch/s390/mm/gmap.c
>> @@ -336,12 +336,11 @@ static int gmap_alloc_table(struct gmap *gmap, unsigned long *table,
>>  static unsigned long __gmap_segment_gaddr(unsigned long *entry)
>>  {
>>  	struct page *page;
>> -	unsigned long offset, mask;
>> +	unsigned long offset;
>>  
>>  	offset = (unsigned long) entry / sizeof(unsigned long);
>>  	offset = (offset & (PTRS_PER_PMD - 1)) * PMD_SIZE;
>> -	mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
>> -	page = virt_to_page((void *)((unsigned long) entry & mask));
>> +	page = pmd_pgtable_page((pmd_t *) entry);
>>  	return page->index + offset;
>>  }
> 
> Looks okay to me.
> 
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index e9e387caffac..5ead9e997510 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -2403,7 +2403,7 @@ static inline void pgtable_pte_page_dtor(struct page *page)
>>  
>>  #if USE_SPLIT_PMD_PTLOCKS
>>  
>> -static struct page *pmd_pgtable_page(pmd_t *pmd)
>> +static inline struct page *pmd_pgtable_page(pmd_t *pmd)
>>  {
>>  	unsigned long mask = ~(PTRS_PER_PMD * sizeof(pmd_t) - 1);
>>  	return virt_to_page((void *)((unsigned long) pmd & mask));
> 
> This chunk does not appear to belong to this patch.

Should not this helper be made a 'static inline' before using it else where ?