> On Aug 18, 2022, at 10:57, Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>
>
>
> 在 8/18/2022 10:41 AM, Muchun Song 写道:
>>> On Aug 17, 2022, at 14:21, Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> wrote:
>>>
>>> The pmd_huge() is used to validate if the pmd entry is mapped by a huge
>>> page, also including the case of non-present (migration or hwpoisoned)
>>> pmd entry on arm64 or x86 architectures. Thus we should validate if it
>>> is present before making the pmd entry old or getting young state,
>>> otherwise we can not get the correct corresponding page.
>>>
>>> Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>>> ---
>>> mm/damon/vaddr.c | 10 ++++++++++
>>> 1 file changed, 10 insertions(+)
>>>
>>> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
>>> index 3c7b9d6..1d16c6c 100644
>>> --- a/mm/damon/vaddr.c
>>> +++ b/mm/damon/vaddr.c
>>> @@ -304,6 +304,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
>>>
>>> if (pmd_huge(*pmd)) {
>>> ptl = pmd_lock(walk->mm, pmd);
>>> + if (!pmd_present(*pmd)) {
>> Unluckily, we should use pte_present here. See commit c9d398fa23788. We can use
>> huge_ptep_get() to get a hugetlb pte, so it’s better to put the check after
>> pmd_huge.
>
> IMO this is not the case for hugetlb, and the hugetlb case will be handled by damon_mkold_hugetlb_entry(), which already used pte_present() for hugetlb case.
Well, I thought it is hugetlb related since I saw the usage of pmd_huge. If it is THP case, why
not use pmd_trans_huge?
Thanks.
>
>> Cc Mike to make sure I am not missing something.
>> Muchun,
>> Thanks.
>>> + spin_unlock(ptl);
>>> + return 0;
>>> + }
>>> +
>>> if (pmd_huge(*pmd)) {
>>> damon_pmdp_mkold(pmd, walk->mm, addr);
>>> spin_unlock(ptl);
>>> @@ -431,6 +436,11 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr,
>>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>>> if (pmd_huge(*pmd)) {
>>> ptl = pmd_lock(walk->mm, pmd);
>>> + if (!pmd_present(*pmd)) {
>>> + spin_unlock(ptl);
>>> + return 0;
>>> + }
>>> +
>>> if (!pmd_huge(*pmd)) {
>>> spin_unlock(ptl);
>>> goto regular_page;
>>> --
>>> 1.8.3.1
