6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ming Lei <ming.lei@xxxxxxxxxx>
[ Upstream commit 393cd8ffd832f23eec3a105553eff622e8198918 ]
blkg_lookup() is called with either queue_lock or rcu read lock, so
use rcu_dereference_check(lockdep_is_held(&q->queue_lock)) for
retrieving 'blkg', which way models the check exactly for covering
queue lock or rcu read lock.
Fix lockdep warning of "block/blk-cgroup.h:254 suspicious rcu_dereference_check() usage!"
from blkg_lookup().
Tested-by: Changhui Zhong <czhong@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
Fixes: 83462a6c971c ("blkcg: Drop unnecessary RCU read [un]locks from blkg_conf_prep/finish()")
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231219012833.2129540-1-ming.lei@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
block/blk-cgroup.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index fd482439afbc..b927a4a0ad03 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -252,7 +252,8 @@ static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
if (blkcg == &blkcg_root)
return q->root_blkg;
- blkg = rcu_dereference(blkcg->blkg_hint);
+ blkg = rcu_dereference_check(blkcg->blkg_hint,
+ lockdep_is_held(&q->queue_lock));
if (blkg && blkg->q == q)
return blkg;
--
2.43.0
