On 08/12/2020 12:03 PM, Aneesh Kumar K.V wrote: > pmd_clear() should not be used to clear pmd level pte entries. Could you please elaborate on this. The proposed change set does not match the description here. > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> > --- > mm/debug_vm_pgtable.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 061c19bba7f0..529892b9be2f 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -191,6 +191,8 @@ static void __init pmd_advanced_tests(struct mm_struct *mm, > pmd = READ_ONCE(*pmdp); > WARN_ON(pmd_young(pmd)); > > + /* Clear the pte entries */ > + pmdp_huge_get_and_clear(mm, vaddr, pmdp); > pgtable = pgtable_trans_huge_withdraw(mm, pmdp); > } > > @@ -313,6 +315,8 @@ static void __init pud_advanced_tests(struct mm_struct *mm, > pudp_test_and_clear_young(vma, vaddr, pudp); > pud = READ_ONCE(*pudp); > WARN_ON(pud_young(pud)); > + > + pudp_huge_get_and_clear(mm, vaddr, pudp); > } > > static void __init pud_leaf_tests(unsigned long pfn, pgprot_t prot) > @@ -431,8 +435,6 @@ static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp, > * This entry points to next level page table page. > * Hence this must not qualify as pud_bad(). > */ > - pmd_clear(pmdp); > - pud_clear(pudp); Both entires are cleared before creating a fresh page table entry. Why that is a problem. > pud_populate(mm, pudp, pmdp); > pud = READ_ONCE(*pudp); > WARN_ON(pud_bad(pud)); > @@ -564,7 +566,6 @@ static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp, > * This entry points to next level page table page. > * Hence this must not qualify as pmd_bad(). > */ > - pmd_clear(pmdp); Ditto. > pmd_populate(mm, pmdp, pgtable); > pmd = READ_ONCE(*pmdp); > WARN_ON(pmd_bad(pmd)); >
