[PATCH -V8 18/18] powerpc: disable assert_pte_locked for collapse_huge_page
From: Aneesh Kumar K.V <hidden>
Date: 2013-05-12 16:14:44
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
From: "Aneesh Kumar K.V" <redacted> 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 <redacted> --- 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