mm/hugetlb: use hugetlb_pte_stable in migration race check

After hugetlb_pte_stable() introduced, we can also rewrite the migration
race condition against page allocation to use the new helper too.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Peter Xu <[email protected]>
Reviewed-by: Mike Kravetz <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Nadav Amit <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: xzpeter

mm/hugetlb.c

@@ -5634,11 +5634,10 @@ static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
 			 * here.  Before returning error, get ptl and make
 			 * sure there really is no pte entry.
 			 */
-			ptl = huge_pte_lock(h, mm, ptep);
-			ret = 0;
-			if (huge_pte_none(huge_ptep_get(ptep)))
+			if (hugetlb_pte_stable(h, mm, ptep, old_pte))
 				ret = vmf_error(PTR_ERR(page));
-			spin_unlock(ptl);
+			else
+				ret = 0;
 			goto out;
 		}
 		clear_huge_page(page, address, pages_per_huge_page(h));