6.6-stable review patch. If anyone has any objections, please let me know.
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From: Ming Lei ming.lei@redhat.com
[ 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@redhat.com Signed-off-by: Ming Lei ming.lei@redhat.com Reviewed-by: Yu Kuai yukuai3@huawei.com Fixes: 83462a6c971c ("blkcg: Drop unnecessary RCU read [un]locks from blkg_conf_prep/finish()") Acked-by: Tejun Heo tj@kernel.org Link: https://lore.kernel.org/r/20231219012833.2129540-1-ming.lei@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- 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;