On 2016/6/16 23:42, Michal Hocko wrote:
> On Thu 16-06-16 19:36:11, zhongjiang wrote:
>> From: zhong jiang <zhongjiang@xxxxxxxxxx>
>>
>> when a process acquire a pmd table shared by other process, we
>> increase the account to current process. otherwise, a race result
>> in other tasks have set the pud entry. so it no need to increase it.
>>
>> Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
>> ---
>> mm/hugetlb.c | 5 ++---
>> 1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 19d0d08..3b025c5 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -4189,10 +4189,9 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
>> if (pud_none(*pud)) {
>> pud_populate(mm, pud,
>> (pmd_t *)((unsigned long)spte & PAGE_MASK));
>> - } else {
>> + } else
>> put_page(virt_to_page(spte));
>> - mm_inc_nr_pmds(mm);
>> - }
> The code is quite puzzling but is this correct? Shouldn't we rather do
> mm_dec_nr_pmds(mm) in that path to undo the previous inc?
Yes, you are right. I will modify it in V2.
Thanks
zhongjiang
>
>> +
>> spin_unlock(ptl);
>> out:
>> pte = (pte_t *)pmd_alloc(mm, pud, addr);
>> --
>> 1.8.3.1
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