From 3be7ad35f10e8e19f618f67ddca0bc0e247f6505 Mon Sep 17 00:00:00 2001 From: Tao Cui Date: Mon, 3 Aug 2026 21:34:00 +0800 Subject: [PATCH] block/blk-cgroup-rwstat: use data_race() for online test blkg_rwstat_recursive_sum() reads pos_blkg->online without the queue lock that its doc comment requires, since blkcg_print_blkgs() stopped holding it in 56cc24f59c14. Concurrent blkg_create/destroy flips ->online, tripping KCSAN. The race is harmless (RCU-protected, stale online only causes minor stat noise). Use data_race() to annotate the intentional lockless read. Also update the stale doc comment that still requires the queue lock. Reviewed-by: Yu Kuai Signed-off-by: Tao Cui Acked-by: Tejun Heo Link: https://patch.msgid.link/20260803133400.137906-1-cui.tao@linux.dev Signed-off-by: Jens Axboe --- block/blk-cgroup-rwstat.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/block/blk-cgroup-rwstat.c b/block/blk-cgroup-rwstat.c index aae910713814..2e9bf081cce2 100644 --- a/block/blk-cgroup-rwstat.c +++ b/block/blk-cgroup-rwstat.c @@ -88,8 +88,7 @@ EXPORT_SYMBOL_GPL(blkg_prfill_rwstat); * @sum: blkg_rwstat_sample structure containing the results * * Collect the blkg_rwstat specified by @blkg, @pol and @off and all its - * online descendants and their aux counts. The caller must be holding the - * queue lock for online tests. + * online descendants and their aux counts. * * If @pol is NULL, blkg_rwstat is at @off bytes into @blkg; otherwise, it * is at @off bytes into @blkg's blkg_policy_data of the policy. @@ -107,7 +106,7 @@ void blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, struct blkcg_policy *pol, blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) { struct blkg_rwstat *rwstat; - if (!pos_blkg->online) + if (!data_race(pos_blkg->online)) continue; if (pol) {