[PATCH v3 04/13 fix] powerpc: assert_pte_locked() use pte_offset_map_nolock(): fix
From: Hugh Dickins <hughd@google.com>
Date: 2023-07-23 22:26:21
Also in:
linux-mm, linux-s390, lkml, sparclinux
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
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 <hughd@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