Subject: [PATCH 09/16] debug_vm_pgtable/set_pud: Don't use set_pud_at to update an existing pud entry

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 12 Aug 2020 12:03:51 +0530

set_pud_at() should not be used to set a pte entry at locations that
already holds a valid pte entry. Architectures like ppc64 don't do TLB
invalidate in set_pud_at() and hence expect it to be used to set locations
that are not a valid PTE.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 mm/debug_vm_pgtable.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 60bf876081b8..644d28861ce9 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -278,9 +278,6 @@ static void __init pud_advanced_tests(struct mm_struct *mm,
 	WARN_ON(pud_write(pud));
 
 #ifndef __PAGETABLE_PMD_FOLDED
-
-	pud = pud_mkhuge(pfn_pud(pfn, prot));
-	set_pud_at(mm, vaddr, pudp, pud);
 	pudp_huge_get_and_clear(mm, vaddr, pudp);
 	pud = READ_ONCE(*pudp);
 	WARN_ON(!pud_none(pud));
@@ -302,6 +299,11 @@ static void __init pud_advanced_tests(struct mm_struct *mm,
 	pud = READ_ONCE(*pudp);
 	WARN_ON(!(pud_write(pud) && pud_dirty(pud)));
 
+	pudp_huge_get_and_clear_full(vma, vaddr, pudp, 1);
+	pud = READ_ONCE(*pudp);
+	WARN_ON(!pud_none(pud));
+
+	pud = pud_mkhuge(pfn_pud(pfn, prot));
 	pud = pud_mkyoung(pud);
 	set_pud_at(mm, vaddr, pudp, pud);
 	pudp_test_and_clear_young(vma, vaddr, pudp);
-- 
2.26.2