mm/swapfile: mark racy access on si->highest_bit
In scan_swap_map_slots(), si->highest_bit can by changed by
swap_range_alloc() concurrently. All reads on si->highest_bit except one
is either protected by lock or read using READ_ONCE. So mark the one racy
read on si->highest_bit as benign using READ_ONCE.
This patch is aimed at reducing the number of benign races reported by
KCSAN in order to focus future debugging effort on harmful races.
Link: https://lkml.kernel.org/r/tencent_912BC3E8B0291DA4A0028AB424076375DA07@qq.com
Signed-off-by: linke li <lilinke99@qq.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 9660658..f6ca215 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -902,7 +902,7 @@ static int scan_swap_map_slots(struct swap_info_struct *si,
last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
/* Locate the first empty (unaligned) cluster */
- for (; last_in_cluster <= si->highest_bit; offset++) {
+ for (; last_in_cluster <= READ_ONCE(si->highest_bit); offset++) {
if (si->swap_map[offset])
last_in_cluster = offset + SWAPFILE_CLUSTER;
else if (offset == last_in_cluster) {
