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writeback: drop now-unnecessary rcu_barrier() in cgroup_writeback_umount()

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Commit e1b849cfa6 ("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: e1b849cfa6 ("writeback: Avoid contention on wb->list_lock when switching inodes")
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
Link: https://patch.msgid.link/20260521095016.2791354-3-libaokun@linux.alibaba.com
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Baokun Li
2026-05-21 17:50:15 +08:00
committed by Christian Brauner
parent cba38ec4cb
commit e90a6d668e
1 changed files with 0 additions and 5 deletions
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5
fs/fs-writeback.c
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@@ -1248,11 +1248,6 @@ void cgroup_writeback_umount(struct super_block *sb)
* will then drain it.
*/
synchronize_rcu();
/*
* Use rcu_barrier() to wait for all pending callbacks to
* ensure that all in-flight wb switches are in the workqueue.
*/
rcu_barrier();
flush_workqueue(isw_wq);
}
}