linux-kernel - Re: [PATCH] mm: move huge_pmd_set_accessed out of huge

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Date:	Thu, 21 Apr 2016 15:57:35 -0700
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	aarcange@...hat.com, mgorman@...e.de, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] mm: move huge_pmd_set_accessed out of huge_memory.c

On 4/21/2016 2:15 AM, Hugh Dickins wrote:
> On Wed, 20 Apr 2016, Shi, Yang wrote:
>
>> Hi folks,
>>
>> I didn't realize pmd_* functions are protected by CONFIG_TRANSPARENT_HUGEPAGE
>> on the most architectures before I made this change.
>>
>> Before I fix all the affected architectures code, I want to check if you guys
>> think this change is worth or not?
>
> Thanks for asking: no, it is not worthwhile.
>
> I would much prefer not to have to consider these trivial cleanups
> in the huge memory area at this time.  Kirill and I have urgent work
> to do in this area, and coping with patch conflicts between different
> versions of the source will not help any of us.

Thanks for your suggestion. I would consider to put such cleanup work on 
the back burner.

Yang

>
> Thanks,
> Hugh
>
>>
>> Thanks,
>> Yang
>>
>> On 4/20/2016 11:24 AM, Yang Shi wrote:
>>> huge_pmd_set_accessed is only called by __handle_mm_fault from memory.c,
>>> move the definition to memory.c and make it static like create_huge_pmd and
>>> wp_huge_pmd.
>>>
>>> Signed-off-by: Yang Shi <yang.shi@...aro.org>
>>> ---
>>>    include/linux/huge_mm.h |  4 ----
>>>    mm/huge_memory.c        | 23 -----------------------
>>>    mm/memory.c             | 23 +++++++++++++++++++++++
>>>    3 files changed, 23 insertions(+), 27 deletions(-)
>>>
>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>>> index 7008623..c218ab7b 100644
>>> --- a/include/linux/huge_mm.h
>>> +++ b/include/linux/huge_mm.h
>>> @@ -8,10 +8,6 @@ extern int do_huge_pmd_anonymous_page(struct mm_struct
>>> *mm,
>>>    extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct
>>> *src_mm,
>>>    			 pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
>>>    			 struct vm_area_struct *vma);
>>> -extern void huge_pmd_set_accessed(struct mm_struct *mm,
>>> -				  struct vm_area_struct *vma,
>>> -				  unsigned long address, pmd_t *pmd,
>>> -				  pmd_t orig_pmd, int dirty);
>>>    extern int do_huge_pmd_wp_page(struct mm_struct *mm, struct
>>> vm_area_struct *vma,
>>>    			       unsigned long address, pmd_t *pmd,
>>>    			       pmd_t orig_pmd);
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index fecbbc5..6c14cb6 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -1137,29 +1137,6 @@ out:
>>>    	return ret;
>>>    }
>>>
>>> -void huge_pmd_set_accessed(struct mm_struct *mm,
>>> -			   struct vm_area_struct *vma,
>>> -			   unsigned long address,
>>> -			   pmd_t *pmd, pmd_t orig_pmd,
>>> -			   int dirty)
>>> -{
>>> -	spinlock_t *ptl;
>>> -	pmd_t entry;
>>> -	unsigned long haddr;
>>> -
>>> -	ptl = pmd_lock(mm, pmd);
>>> -	if (unlikely(!pmd_same(*pmd, orig_pmd)))
>>> -		goto unlock;
>>> -
>>> -	entry = pmd_mkyoung(orig_pmd);
>>> -	haddr = address & HPAGE_PMD_MASK;
>>> -	if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
>>> -		update_mmu_cache_pmd(vma, address, pmd);
>>> -
>>> -unlock:
>>> -	spin_unlock(ptl);
>>> -}
>>> -
>>>    static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
>>>    					struct vm_area_struct *vma,
>>>    					unsigned long address,
>>> diff --git a/mm/memory.c b/mm/memory.c
>>> index 93897f2..6ced4eb 100644
>>> --- a/mm/memory.c
>>> +++ b/mm/memory.c
>>> @@ -3287,6 +3287,29 @@ static int wp_huge_pmd(struct mm_struct *mm, struct
>>> vm_area_struct *vma,
>>>    	return VM_FAULT_FALLBACK;
>>>    }
>>>
>>> +static void huge_pmd_set_accessed(struct mm_struct *mm,
>>> +				  struct vm_area_struct *vma,
>>> +				  unsigned long address,
>>> +				  pmd_t *pmd, pmd_t orig_pmd,
>>> +				  int dirty)
>>> +{
>>> +	spinlock_t *ptl;
>>> +	pmd_t entry;
>>> +	unsigned long haddr;
>>> +
>>> +	ptl = pmd_lock(mm, pmd);
>>> +	if (unlikely(!pmd_same(*pmd, orig_pmd)))
>>> +		goto unlock;
>>> +
>>> +	entry = pmd_mkyoung(orig_pmd);
>>> +	haddr = address & HPAGE_PMD_MASK;
>>> +	if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
>>> +		update_mmu_cache_pmd(vma, address, pmd);
>>> +
>>> +unlock:
>>> +	spin_unlock(ptl);
>>> +}
>>> +
>>>    /*
>>>     * These routines also need to handle stuff like marking pages dirty
>>>     * and/or accessed for architectures that don't do it in hardware (most