Commit 2cb51a05 authored by linke li's avatar linke li Committed by Liu Shixin
Browse files

mm/swapfile: mark racy access on si->highest_bit 

mainline inclusion
from mainline-v6.10-rc1
commit 5ee9562c586cd4ca9402b3636157abdd58ab7978
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAHY3K

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5ee9562c586cd4ca9402b3636157abdd58ab7978

--------------------------------

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: default avatarlinke li <lilinke99@qq.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
parent 4e5e68c0

mm/swapfile.c

+1 −1
Original line number Diff line number Diff line
@@ -896,7 +896,7 @@ 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) {