Subject: [PATCH v2 13/13] mm/debug_vm_pgtable: populate a pte entry before fetching it

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 19 Aug 2020 18:31:07 +0530

pte_clear_tests operate on an existing pte entry. Make sure that is not a none
pte entry.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 mm/debug_vm_pgtable.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index 09ce9974c187..7d9f8e1d790f 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -531,7 +531,7 @@ static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp,
 static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep,
 				   unsigned long vaddr)
 {
-	pte_t pte = ptep_get(ptep);
+	pte_t pte =  ptep_get_and_clear(mm, vaddr, ptep);
 
 	pr_debug("Validating PTE clear\n");
 	pte = __pte(pte_val(pte) | RANDOM_ORVALUE);
@@ -929,7 +929,7 @@ static int __init debug_vm_pgtable(void)
 	p4d_t *p4dp, *saved_p4dp;
 	pud_t *pudp, *saved_pudp;
 	pmd_t *pmdp, *saved_pmdp, pmd;
-	pte_t *ptep;
+	pte_t *ptep, pte;
 	pgtable_t saved_ptep;
 	pgprot_t prot, protnone;
 	phys_addr_t paddr;
@@ -1034,6 +1034,8 @@ static int __init debug_vm_pgtable(void)
 	 */
 
 	ptep = pte_alloc_map_lock(mm, pmdp, vaddr, &ptl);
+	pte = pfn_pte(pte_aligned, prot);
+	set_pte_at(mm, vaddr, ptep, pte);
 	pte_clear_tests(mm, ptep, vaddr);
 	pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
 	pte_unmap_unlock(ptep, ptl);
-- 
2.26.2