From: "Aneesh Kumar K.V" <aneesh.ku...@linux.vnet.ibm.com>
With THP we set pmd to none, before we do pte_clear. Hence we can't
walk page table to get the pte lock ptr and verify whether it is locked.
THP do take pte lock before calling pte_clear. So we don't change the locking
rules here. It is that we can't use page table walking to check whether
pte locks are held with THP.
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
---
arch/powerpc/mm/pgtable.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 214130a..edda589 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -235,6 +235,14 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long
addr)
pud = pud_offset(pgd, addr);
BUG_ON(pud_none(*pud));
pmd = pmd_offset(pud, addr);
+ /*
+ * khugepaged to collapse normal pages to hugepage, first set
+ * pmd to none to force page fault/gup to take mmap_sem. After
+ * pmd is set to none, we do a pte_clear which does this assertion
+ * so if we find pmd none, return.
+ */
+ if (pmd_none(*pmd))
+ return;
BUG_ON(!pmd_present(*pmd));
assert_spin_locked(pte_lockptr(mm, pmd));
}
--
1.8.1.2
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