On 9/28/19 5:45 PM, Wei Yang wrote:
> 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@xxxxxxxxxxxxxxx> 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.
See 1b426bac66e6 ("hugetlb: use same fault hash key for shared and private
mappings"). Prior to that change, the hash key for private mappings was
created by:
key[0] = (unsigned long) mm;
key[1] = address >> huge_page_shift(h);
When removing that code, I should have removed 'h'.
--
Mike Kravetz
