io_uring: refactor io_assign_file error path

All io_assign_file() callers do error handling themselves,
req_set_fail() in the io_assign_file()'s fail path needlessly bloats the
kernel and is not the best abstraction to have. Simplify the error path.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/eff77fb1eac2b6a90cca5223813e6a396ffedec0.1650311386.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -7134,12 +7134,8 @@ static bool io_assign_file(struct io_kiocb *req, unsigned int issue_flags)
 		req->file = io_file_get_fixed(req, req->cqe.fd, issue_flags);
 	else
 		req->file = io_file_get_normal(req, req->cqe.fd);
-	if (req->file)
-		return true;
 
-	req_set_fail(req);
-	req->cqe.res = -EBADF;
-	return false;
+	return !!req->file;
 }
 
 static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)