From: Guopeng Zhang <guopeng.zhang@linux.dev>
To: Tejun Heo <tj@kernel.org>, Josef Bacik <josef@toxicpanda.com>,
Jens Axboe <axboe@kernel.dk>
Cc: Yu Kuai <yukuai@fygo.io>,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org,
Guopeng Zhang <guopeng.zhang@linux.dev>,
Guopeng Zhang <zhangguopeng@kylinos.cn>
Subject: [PATCH] blk-cgroup: clear blkg->pd[] with WRITE_ONCE() in blkcg_deactivate_policy()
Date: Tue, 7 Jul 2026 20:58:14 +0800 [thread overview]
Message-ID: <20260707125814.1978139-1-guopeng.zhang@linux.dev> (raw)
From: Guopeng Zhang <zhangguopeng@kylinos.cn>
blkcg_activate_policy() installs blkg->pd[] entries with WRITE_ONCE()
and also uses WRITE_ONCE() when clearing them on its error path.
blkg_to_pd() is used by RCU readers and reads the same array with
READ_ONCE().
blkcg_deactivate_policy() clears the entry with a plain store. Use
WRITE_ONCE() there as well.
Fixes: 56cc24f59c14 ("blk-cgroup: don't nest queue_lock under rcu in blkcg_print_blkgs()")
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
---
block/blk-cgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index d2a1f5903f24..a1dd69f99f5c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1691,7 +1691,7 @@ void blkcg_deactivate_policy(struct gendisk *disk,
if (blkg->pd[pol->plid]->online && pol->pd_offline_fn)
pol->pd_offline_fn(blkg->pd[pol->plid]);
pol->pd_free_fn(blkg->pd[pol->plid]);
- blkg->pd[pol->plid] = NULL;
+ WRITE_ONCE(blkg->pd[pol->plid], NULL);
}
spin_unlock(&blkcg->lock);
}
--
2.43.0
next reply other threads:[~2026-07-07 12:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-07 12:58 Guopeng Zhang [this message]
2026-07-08 5:10 ` [PATCH] blk-cgroup: clear blkg->pd[] with WRITE_ONCE() in blkcg_deactivate_policy() Tao Cui
2026-07-08 5:29 ` Tao Cui
2026-07-08 5:59 ` Guopeng Zhang
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