mm: hugetlb_vmemmap: add missing smp_wmb() before set_pte_at()

The memory barrier smp_wmb() is needed to make sure that preceding stores
to the page contents become visible before the below set_pte_at() write.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Yin Fengwei <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: MiaoheLin

mm/hugetlb_vmemmap.c

@@ -287,6 +287,11 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr,
 	copy_page(to, (void *)walk->reuse_addr);
 	reset_struct_pages(to);
 
+	/*
+	 * Makes sure that preceding stores to the page contents become visible
+	 * before the set_pte_at() write.
+	 */
+	smp_wmb();
 	set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot));
 }