io_uring: don't do full *prep_worker() from io-wq

io_prep_async_worker() called io_wq_assign_next() do many useless checks:
io_req_work_grab_env() was already called during prep, and @do_hashed
is not ever used. Add io_prep_next_work() -- simplified version, that
can be called io-wq.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -950,6 +950,17 @@ static inline void io_req_work_drop_env(struct io_kiocb *req)
 	}
 }
 
+static inline void io_prep_next_work(struct io_kiocb *req,
+				     struct io_kiocb **link)
+{
+	const struct io_op_def *def = &io_op_defs[req->opcode];
+
+	if (!(req->flags & REQ_F_ISREG) && def->unbound_nonreg_file)
+		req->work.flags |= IO_WQ_WORK_UNBOUND;
+
+	*link = io_prep_linked_timeout(req);
+}
+
 static inline bool io_prep_async_work(struct io_kiocb *req,
 				      struct io_kiocb **link)
 {
@@ -2453,7 +2464,7 @@ static void io_wq_assign_next(struct io_wq_work **workptr, struct io_kiocb *nxt)
 {
 	struct io_kiocb *link;
 
-	io_prep_async_work(nxt, &link);
+	io_prep_next_work(nxt, &link);
 	*workptr = &nxt->work;
 	if (link) {
 		nxt->work.flags |= IO_WQ_WORK_CB;