[PATCH] memtest: use {READ,WRITE}_ONCE in memory scanning

[Qiang Zhang]

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

Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Qiang Zhang <qiang4.zhang@xxxxxxxxx>
---
 mm/memtest.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memtest.c b/mm/memtest.c
index 32f3e9dda837..c2c609c39119 100644
--- a/mm/memtest.c
+++ b/mm/memtest.c
@@ -51,10 +51,10 @@ 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;
-- 
2.39.2