io_uring: optimise io_req_find_next() fast check

gcc 9.2.0 compiles io_req_find_next() as a separate function leaving
the first REQ_F_LINK_HEAD fast check not inlined. Help it by splitting
out the check from the function.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1664,12 +1664,9 @@ static void io_fail_links(struct io_kiocb *req)
 	io_cqring_ev_posted(ctx);
 }
 
-static struct io_kiocb *io_req_find_next(struct io_kiocb *req)
+static struct io_kiocb *__io_req_find_next(struct io_kiocb *req)
 {
-	if (likely(!(req->flags & REQ_F_LINK_HEAD)))
-		return NULL;
 	req->flags &= ~REQ_F_LINK_HEAD;
-
 	if (req->flags & REQ_F_LINK_TIMEOUT)
 		io_kill_linked_timeout(req);
 
@@ -1685,6 +1682,13 @@ static struct io_kiocb *io_req_find_next(struct io_kiocb *req)
 	return NULL;
 }
 
+static struct io_kiocb *io_req_find_next(struct io_kiocb *req)
+{
+	if (likely(!(req->flags & REQ_F_LINK_HEAD)))
+		return NULL;
+	return __io_req_find_next(req);
+}
+
 static void __io_req_task_cancel(struct io_kiocb *req, int error)
 {
 	struct io_ring_ctx *ctx = req->ctx;