Re: [PATCH v4 2/3] writeback: drop now-unnecessary rcu_barrier() in cgroup_writeback_umount()

[Tejun Heo]

On Thu, May 21, 2026 at 05:50:15PM +0800, Baokun Li wrote:
> Commit e1b849cfa6b6 ("writeback: Avoid contention on wb->list_lock when
> switching inodes") replaced the queue_rcu_work() based scheduling of
> inode wb switches with a plain queue_work().  Since then no switcher
> goes through call_rcu(), so rcu_barrier() in cgroup_writeback_umount()
> has no callbacks of its own to wait for.  It still drains unrelated
> call_rcu() callbacks from other subsystems on busy systems, which
> incidentally slows umount down; drop it.
> 
> Fixes: e1b849cfa6b6 ("writeback: Avoid contention on wb->list_lock when switching inodes")
> Reviewed-by: Jan Kara <jack@xxxxxxx>
> Signed-off-by: Baokun Li <libaokun@xxxxxxxxxxxxxxxxx>

Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Thanks.

-- 
tejun