[PATCHSET v2] io_uring and task_work interactions

[Jens Axboe <axboe@kernel.dk>]

There's a case for io_uring where we want to run the task_work on ring
exit, but we can't easily do that as we don't know if the task_works has
work, or if exit work has already been queued.

First two are just cleanups, third one makes task_work_exited externally
visible, and fourth one let's io_uring call task_work_run() off the
fops->release() path to fix an issue where we need to potentially flush
work here.

Since v1:
- Don't add task_work_exited check to the fast path
- Ensure exit_task_work() always runs

-- 
Jens Axboe