[patch -mm 2/2] smaps: use ptep_test_and_clear_young

[David Rientjes <rientjes@google.com>]

Use arch-specified ptep_test_and_clear_young() to clear the pte accessed
bits for /proc/pid/clear_refs.  This avoids a race condition if a pte is
modified between pte_mkold() and set_pte_at().

Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: David Rientjes <rientjes@google.com>
---
 fs/proc/task_mmu.c |    5 +----
 1 files changed, 1 insertions(+), 4 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -277,10 +277,7 @@ static void clear_refs_one_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 			continue;
 
 		/* Clear accessed and referenced bits. */
-		if (pte_young(ptent)) {
-			ptent = pte_mkold(ptent);
-			set_pte_at(vma->vm_mm, addr, pte, ptent);
-		}
+		ptep_test_and_clear_young(vma, addr, pte);
 		ClearPageReferenced(page);
 	}
 	pte_unmap_unlock(pte - 1, ptl);