Messages in this thread | | | Date | Thu, 18 Aug 2022 10:57:21 +0800 | Subject | Re: [PATCH] mm/damon: Validate if the pmd entry is present before accessing | From | Baolin Wang <> |
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在 8/18/2022 10:41 AM, Muchun Song 写道: > > >> On Aug 17, 2022, at 14:21, Baolin Wang <baolin.wang@linux.alibaba.com> 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@linux.alibaba.com> >> --- >> 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.
> > 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 >> >> >
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