io_uring: use correct "is IO worker" helper

Since we switched to io-wq, the dependent link optimization for when to
pass back work inline has been broken. Fix this by providing a suitable
io-wq helper for io_uring to use to detect when to do this.

Fixes: 561fb04a ("io_uring: replace workqueue usage with io-wq")
Signed-off-by: NJens Axboe <axboe@kernel.dk>

fs/io-wq.h

@@ -62,4 +62,8 @@ static inline void io_wq_worker_running(struct task_struct *tsk)
 }
 #endif
 
+static inline bool io_wq_current_is_worker(void)
+{
+	return in_task() && (current->flags & PF_IO_WORKER);
+}
 #endif

fs/io_uring.c

@@ -872,7 +872,7 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
 			/* we dropped this link, get next */
 			nxt = list_first_entry_or_null(&req->link_list,
 							struct io_kiocb, list);
-		} else if (nxtptr && current_work()) {
+		} else if (nxtptr && io_wq_current_is_worker()) {
 			*nxtptr = nxt;
 			break;
 		} else {