io_uring_ctx_get_file
file = io_uring_ctx_get_file(ops->ring_fd, false);
file = io_uring_ctx_get_file(fd, flags & IORING_ENTER_REGISTERED_RING);
struct file *io_uring_ctx_get_file(unsigned int fd, bool registered);
file = io_uring_ctx_get_file(fd, use_registered_ring);
file = io_uring_ctx_get_file(buf.src_fd, registered_src);