Re: [PATCH v2 1/3] userfaultfd: use vma_pagesize for all huge page size calculation

[Wei Yang <richardw.yang@linux.intel.com>]

On Fri, Sep 27, 2019 at 03:10:33PM -0700, Andrew Morton wrote:
>On Fri, 27 Sep 2019 15:00:30 +0800 Wei Yang <richardw.yang@linux.intel.com> wrote:
>
>> In function __mcopy_atomic_hugetlb, we use two variables to deal with
>> huge page size: vma_hpagesize and huge_page_size.
>> 
>> Since they are the same, it is not necessary to use two different
>> mechanism. This patch makes it consistent by all using vma_hpagesize.
>> 
>> --- a/mm/userfaultfd.c
>> +++ b/mm/userfaultfd.c
>> @@ -262,7 +262,7 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
>>  		pte_t dst_pteval;
>>  
>>  		BUG_ON(dst_addr >= dst_start + len);
>> -		VM_BUG_ON(dst_addr & ~huge_page_mask(h));
>> +		VM_BUG_ON(dst_addr & (vma_hpagesize - 1));
>>  
>>  		/*
>>  		 * Serialize via hugetlb_fault_mutex
>> @@ -273,7 +273,7 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
>>  		mutex_lock(&hugetlb_fault_mutex_table[hash]);
>>  
>>  		err = -ENOMEM;
>> -		dst_pte = huge_pte_alloc(dst_mm, dst_addr, huge_page_size(h));
>> +		dst_pte = huge_pte_alloc(dst_mm, dst_addr, vma_hpagesize);
>>  		if (!dst_pte) {
>>  			mutex_unlock(&hugetlb_fault_mutex_table[hash]);
>>  			goto out_unlock;
>> @@ -300,7 +300,8 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm,
>>  
>>  			err = copy_huge_page_from_user(page,
>>  						(const void __user *)src_addr,
>> -						pages_per_huge_page(h), true);
>> +						vma_hpagesize / PAGE_SIZE,
>> +						true);
>>  			if (unlikely(err)) {
>>  				err = -EFAULT;
>>  				goto out;
>
>Looks right.
>
>We could go ahead and remove local variable `h', given that
>hugetlb_fault_mutex_hash() doesn't actually use its first arg..

Oops, haven't imagine h is not used in the function.


Any historical reason to pass h in hugetlb_fault_mutex_hash()? Neither these
two definition use it.

-- 
Wei Yang
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