Jan Kara wrote: > Make wb_workfn() use wakeup_wb() for requeueing the work which takes all > the necessary precautions against racing with bdi unregistration. Yes, this patch will solve NULL pointer dereference bug. But is it OK to leave list_empty(&wb->work_list) == false situation? Who takes over the role of making list_empty(&wb->work_list) == true? Just a confirmation, for Fabiano Rosas is facing a problem that "write call hangs in kernel space after virtio hot-remove" and is thinking that we might need to go the opposite direction ( http://lkml.kernel.org/r/f0787b79-1e50-5f55-a400-44f715451777@xxxxxxxxxxxxx ).