io_uring: optimise io_rw_reissue()

The hot path is IO completing on the first try. Reshuffle io_rw_reissue() so
it's checked first.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2738,12 +2738,13 @@ static bool io_resubmit_prep(struct io_kiocb *req, int error)
 static bool io_rw_reissue(struct io_kiocb *req, long res)
 {
 #ifdef CONFIG_BLOCK
-	umode_t mode = file_inode(req->file)->i_mode;
+	umode_t mode;
 	int ret;
 
-	if (!S_ISBLK(mode) && !S_ISREG(mode))
+	if (res != -EAGAIN && res != -EOPNOTSUPP)
 		return false;
-	if ((res != -EAGAIN && res != -EOPNOTSUPP) || io_wq_current_is_worker())
+	mode = file_inode(req->file)->i_mode;
+	if ((!S_ISBLK(mode) && !S_ISREG(mode)) || io_wq_current_is_worker())
 		return false;
 
 	lockdep_assert_held(&req->ctx->uring_lock);