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: 561fb04a6a ("io_uring: replace workqueue usage with io-wq")
Signed-off-by: Jens 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