[PATCH v3] mm/page_vma_mapped_walk: Use ptep_get_lockless() for lockless access

[Alexander Gordeev]

Switch from ptep_get() to ptep_get_lockless() accessor for
PTE reads when no lock is taken.

Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
---
 mm/page_vma_mapped.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
index a4d52fdb3056..2ccbabfb2cc1 100644
--- a/mm/page_vma_mapped.c
+++ b/mm/page_vma_mapped.c
@@ -41,7 +41,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
 	if (!pvmw->pte)
 		return false;
 
-	ptent = ptep_get(pvmw->pte);
+	ptent = ptep_get_lockless(pvmw->pte);
 
 	if (pte_none(ptent)) {
 		return false;
@@ -183,6 +183,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 	struct mm_struct *mm = vma->vm_mm;
 	unsigned long end;
 	spinlock_t *ptl;
+	pte_t pteval;
 	pgd_t *pgd;
 	p4d_t *p4d;
 	pud_t *pud;
@@ -310,7 +311,11 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
 				goto restart;
 			}
 			pvmw->pte++;
-		} while (pte_none(ptep_get(pvmw->pte)));
+			if (!pvmw->ptl)
+				pteval = ptep_get_lockless(pvmw->pte);
+			else
+				pteval = ptep_get(pvmw->pte);
+		} while (pte_none(pteval));
 
 		if (!pvmw->ptl) {
 			spin_lock(ptl);
-- 
2.51.0