From a00e7bea0dde6a44b9bbe84f30b731d9ec73858b Mon Sep 17 00:00:00 2001 From: "Aneesh Kumar K.V" Date: Thu, 20 Jun 2013 14:30:24 +0530 Subject: [PATCH] powerpc: disable assert_pte_locked for collapse_huge_page 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 Signed-off-by: Benjamin Herrenschmidt --- 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 214130a4edc6..edda589795c3 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)); } -- 2.20.1