This is a note to let you know that I've just added the patch titled
blk-cgroup: fix rcu lockdep warning in blkg_lookup()
to the 6.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
blk-cgroup-fix-rcu-lockdep-warning-in-blkg_lookup.patch
and it can be found in the queue-6.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit aef0e9012dca110bdbfacbac5c73858c837f7758
Author: Ming Lei <ming.lei@xxxxxxxxxx>
Date: Tue Dec 19 09:28:33 2023 +0800
blk-cgroup: fix rcu lockdep warning in blkg_lookup()
[ 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>
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;
