On Mon, Mar 06, 2017 at 05:33:59PM +0100, Jan Kara wrote:

Currently we waited for all cgwbs to get freed in cgwb_bdi_destroy()
which also means that writeback has been shutdown on them. Since this
wait is going away, directly shutdown writeback on cgwbs from
cgwb_bdi_destroy() to avoid live writeback structures after
bdi_unregister() has finished. To make that safe with concurrent
shutdown from cgwb_release_workfn(), we also have to make sure
wb_shutdown() returns only after the bdi_writeback structure is really
shutdown.

Signed-off-by: Jan Kara <jack@suse.cz>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun