[PATCH v2] mm/gup: cleanup pgtable entry accessors

[PATCH v2] mm/gup: cleanup pgtable entry accessors

[Alexander Gordeev]

PMD and PUD entries revalidation has the same semantics as PTE entry
revalidation. Convert the remaining direct entry dereferences to the
corresponding accessors.

The PTE validation in gup_fast_pte_range() is inconsistent with the
prior value acquisition in the sense that it drops the lockless
access semantics.

Use the lockless accessor not only for the PTE, but also for the PMD
validation, which is likewise inconsistent with the prior value
acquisition in gup_fast_pmd_range().

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
 mm/gup.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 8e7dc2c6ee73..236450feea9a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2865,8 +2865,8 @@ static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr,
 		if (!folio)
 			goto pte_unmap;
 
-		if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) ||
-		    unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) {
+		if (unlikely(pmd_val(pmd) != pmd_val(pmdp_get_lockless(pmdp))) ||
+		    unlikely(pte_val(pte) != pte_val(ptep_get_lockless(ptep)))) {
 			gup_put_folio(folio, 1, flags);
 			goto pte_unmap;
 		}
@@ -2942,7 +2942,7 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	if (!folio)
 		return 0;
 
-	if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) {
+	if (unlikely(pmd_val(orig) != pmd_val(pmdp_get_lockless(pmdp)))) {
 		gup_put_folio(folio, refs, flags);
 		return 0;
 	}
@@ -2985,7 +2985,7 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
 	if (!folio)
 		return 0;
 
-	if (unlikely(pud_val(orig) != pud_val(*pudp))) {
+	if (unlikely(pud_val(orig) != pud_val(pudp_get(pudp)))) {
 		gup_put_folio(folio, refs, flags);
 		return 0;
 	}
-- 
2.51.0