From 50e9f82b1c1dc125c919d2f0d6a2cb77efe75fbb Mon Sep 17 00:00:00 2001
From: Qiang Zhang <qiang4.zhang@intel.com>
Date: Tue, 12 Mar 2024 16:04:23 +0800
Subject: [PATCH] memtest: use {READ,WRITE}_ONCE in memory scanning

[ Upstream commit 82634d7e24271698e50a3ec811e5f50de790a65f ]

memtest failed to find bad memory when compiled with clang.  So use
{WRITE,READ}_ONCE to access memory to avoid compiler over optimization.

Link: https://lkml.kernel.org/r/20240312080422.691222-1-qiang4.zhang@intel.com
Signed-off-by: Qiang Zhang <qiang4.zhang@intel.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/memtest.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memtest.c b/mm/memtest.c
index f53ace709ccd..d407373f225b 100644
--- a/mm/memtest.c
+++ b/mm/memtest.c
@@ -46,10 +46,10 @@ static void __init memtest(u64 pattern, phys_addr_t start_phys, phys_addr_t size
 	last_bad = 0;
 
 	for (p = start; p < end; p++)
-		*p = pattern;
+		WRITE_ONCE(*p, pattern);
 
 	for (p = start; p < end; p++, start_phys_aligned += incr) {
-		if (*p == pattern)
+		if (READ_ONCE(*p) == pattern)
 			continue;
 		if (start_phys_aligned == last_bad + incr) {
 			last_bad += incr;