Re: [PATCH] mm/hugetlb: fix race when migrate pages.

[zhong jiang <zhongjiang@huawei.com>]

On 2016/7/19 19:59, Michal Hocko wrote:
> On Tue 19-07-16 19:43:38, zhong jiang wrote:
> [...]
>>   diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 6384dfd..baba196 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -4213,7 +4213,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
>>         struct vm_area_struct *svma;
>>         unsigned long saddr;
>>         pte_t *spte = NULL;
>> -       pte_t *pte;
>> +       pte_t *pte, entry;
>>         spinlock_t *ptl;
>>
>>         if (!vma_shareable(vma, addr))
>> @@ -4240,6 +4240,11 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
>>
>>         ptl = huge_pte_lockptr(hstate_vma(vma), mm, spte);
>>         spin_lock(ptl);
>> +       entry = huge_ptep_get(spte);
>> +       if (is_hugetlb_entry_migration(entry) ||
>> +                       is_hugetlb_entry_hwpoisoned(entry)) {
>> +               goto end;
>> +       }
>>         if (pud_none(*pud)) {
>>                 pud_populate(mm, pud,
>>                                 (pmd_t *)((unsigned long)spte & PAGE_MASK));
>> @@ -4247,6 +4252,7 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
>>                 put_page(virt_to_page(spte));
>>                 mm_dec_nr_pmds(mm);
>>         }
>> +end:
> out_unlock:
>
> would be more readable. Could you retest the patch, respin the changelog
> to explain what, why and how to fix it and repost again, please?
>
>>         spin_unlock(ptl);
>>  out:
>>         pte = (pte_t *)pmd_alloc(mm, pud, addr);
 ok ,  I will modify it later in v2.  thanks

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