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

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>

diff --git a/mm/memtest.c b/mm/memtest.c
index 32f3e9dda8370f9967988886162434b40fb2d18c..c2c609c3911994a8a877b16a6194860e573f8331 100644 (file)
--- 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;