Hello, It generally looks good to me. The only worry I have is around wb_shutdown() synchronization and if that is actually an issue it shouldn't be too difficult to fix. The other thing which came to mind is that the congested->__bdi sever semantics. IIRC, that one was also to support the "bdi must go away now" behavior. As bdi is refcnted now, I think we can probably just let cong hold onto the bdi rather than try to sever the ref there.
Thanks a lot for working on this! -- tejun
