Aneesh points out that assert_pte_locked() still needs the pmd_none()
check, to stop crashing in khugepaged: restore that comment and check.
Andrew, when merging with original commit, please edit its 1st para to:
Instead of pte_lockptr(), use the recently added pte_offset_map_nolock()
in assert_pte_locked(). BUG if pte_offset_map_nolock() fails.
Signed-off-by: Hugh Dickins <hu...@google.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 16b061af86d7..a3dcdb2d5b4b 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -323,6 +323,14 @@ void assert_pte_locked(struct mm_struct *mm, unsigned long
addr)
pud = pud_offset(p4d, 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_lock. 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;
pte = pte_offset_map_nolock(mm, pmd, addr, &ptl);
BUG_ON(!pte);
assert_spin_locked(ptl);
--
2.35.3
