Revert "mm: fix double page fault on arm64 if PTE_AF is cleared"

This reverts commit 26da22a.

mm/memory.c

@@ -2169,44 +2169,19 @@ static inline bool cow_user_page(struct page *dst, struct page *src,
 			goto pte_unlock;
 		}
 
-	/*
-	 * On architectures with software "accessed" bits, we would
-	 * take a double page fault, so mark it accessed here.
-	 */
-	force_mkyoung = arch_faults_on_old_pte() && !pte_young(vmf->orig_pte);
-	if (force_mkyoung) {
-		pte_t entry;
-
-		vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);
-		if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) {
+		/*
+		 * The same page can be mapped back since last copy attampt.
+		 * Try to copy again under PTL.
+		 */
+		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
 			/*
-			 * Other thread has already handled the fault
-			 * and we don't need to do anything. If it's
-			 * not the case, the fault will be triggered
-			 * again on the same address.
+			 * Give a warn in case there can be some obscure
+			 * use-case
 			 */
-			ret = false;
-			goto pte_unlock;
+warn:
+			WARN_ON_ONCE(1);
+			clear_page(kaddr);
 		}
-
-		entry = pte_mkyoung(vmf->orig_pte);
-		if (ptep_set_access_flags(vma, addr, vmf->pte, entry, 0))
-			update_mmu_cache(vma, addr, vmf->pte);
-	}
-
-	/*
-	 * This really shouldn't fail, because the page is there
-	 * in the page tables. But it might just be unreadable,
-	 * in which case we just give up and fill the result with
-	 * zeroes.
-	 */
-	if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
-		/*
-		 * Give a warn in case there can be some obscure
-		 * use-case
-		 */
-		WARN_ON_ONCE(1);
-		clear_page(kaddr);
 	}
 
 	ret = true;