This is a note to let you know that I've just added the patch titled
blk-throttle: fix lockdep warning of "cgroup_mutex or RCU read lock required!"
to the 4.14-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-throttle-fix-lockdep-warning-of-cgroup_mutex-or-.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4cb24c054ca7d7c1c58c0f8cfe54efc4991e8dc2
Author: Ming Lei <ming.lei@xxxxxxxxxx>
Date: Fri Nov 17 10:35:22 2023 +0800
blk-throttle: fix lockdep warning of "cgroup_mutex or RCU read lock required!"
[ Upstream commit 27b13e209ddca5979847a1b57890e0372c1edcee ]
Inside blkg_for_each_descendant_pre(), both
css_for_each_descendant_pre() and blkg_lookup() requires RCU read lock,
and either cgroup_assert_mutex_or_rcu_locked() or rcu_read_lock_held()
is called.
Fix the warning by adding rcu read lock.
Reported-by: Changhui Zhong <czhong@xxxxxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231117023527.3188627-2-ming.lei@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index fcbbe2e45a2bb..e52a9632993a7 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1391,6 +1391,7 @@ static void tg_conf_updated(struct throtl_grp *tg, bool global)
tg_bps_limit(tg, READ), tg_bps_limit(tg, WRITE),
tg_iops_limit(tg, READ), tg_iops_limit(tg, WRITE));
+ rcu_read_lock();
/*
* Update has_rules[] flags for the updated tg's subtree. A tg is
* considered to have rules if either the tg itself or any of its
@@ -1418,6 +1419,7 @@ static void tg_conf_updated(struct throtl_grp *tg, bool global)
this_tg->latency_target = max(this_tg->latency_target,
parent_tg->latency_target);
}
+ rcu_read_unlock();
/*
* We're already holding queue_lock and know @tg is valid. Let's
