Function io_uring_buf_ring_can_be_registered

tests/io_uring/register.rs:126–174

()

#[cfg(feature = "mm")]
#[test]
fn io_uring_buf_ring_can_be_registered() {
    const ENTRIES: usize = 8;
    const BGID: u16 = 42;

    let mut params = io_uring_params::default();
    let ring_fd = unsafe { io_uring_setup(4, &mut params).unwrap() };

    // Test that the kernel version supports IORING_REGISTER_PBUF_RING. If it
    // doesn't, the kernel will return EINVAL. Not setting a `ring_addr` on
    // `io_uring_buf_reg` will return `EFAULT`.
    if let Err(e) = register_buf_ring(ring_fd.as_fd(), &io_uring_buf_reg::default()) {
        if e == Errno::INVAL {
            // Skip the test, as the current kernel version doesn't support what we need to
            // test.
            return;
        }
    }

    let buf_ring_size = ENTRIES * std::mem::size_of::<io_uring_buf>();

    let br_ptr = unsafe {
        rustix::mm::mmap_anonymous(
            ptr::null_mut(),
            buf_ring_size,
            ProtFlags::READ | ProtFlags::WRITE,
            MapFlags::PRIVATE,
        )
    }
    .unwrap()
    .cast::<io_uring_buf_ring>();

    let br = unsafe { br_ptr.as_mut() }.expect("A valid io_uring_buf_ring struct");

    let mut reg = io_uring_buf_reg::default();
    reg.ring_addr = br_ptr.cast::<c_void>().into();
    reg.ring_entries = ENTRIES as u32;
    reg.bgid = BGID;
    reg.flags = 0;

    assert_eq!(register_buf_ring(ring_fd, &reg), Ok(()));

    let tail = unsafe { br.tail_or_bufs.tail.as_mut() };
    tail.tail = 0;
    let bufs = unsafe { br.tail_or_bufs.bufs.as_mut().bufs.as_mut_slice(ENTRIES) };

    assert_eq!(bufs[0].bid, 0);
    bufs[7].bid = 7;
    assert_eq!(bufs[7].bid, 7);
}