Function open_disk

block/src/factory.rs:85–109

Open a disk image and construct the appropriate async backend. - Opens the file with the requested access mode and flags. - Detects the image format from the file header. - Probes io_uring and Linux AIO support on the running kernel. - Constructs the most capable backend available for the detected format, preferring io_uring over AIO over synchronous fallback. The returned [`OpenedDisk`] exposes

(options: &DiskOpenOptions<'_>)

/// callers can perform post construction validation (e.g. type mismatch
/// checks, configuration warnings).
pub fn open_disk(options: &DiskOpenOptions<'_>) -> BlockResult<OpenedDisk> {
    let mut fs_options = fs::OpenOptions::new();
    fs_options.read(true);
    fs_options.write(!options.readonly);
    if options.direct {
        fs_options.custom_flags(libc::O_DIRECT);
    }

    let mut file = open_disk_image(options.path, &fs_options)?;
    let image_type = detect_image_type(&mut file)?;

    let disk: Box<dyn AsyncFullDiskFile> = match image_type {
        ImageType::FixedVhd => open_fixed_vhd(file, options)?,
        ImageType::Raw => open_raw(file, options)?,
        ImageType::Qcow2 => open_qcow2(file, options)?,
        ImageType::Vhdx => open_vhdx(file, options)?,
        ImageType::Unknown => {
            return Err(
                BlockError::from_kind(BlockErrorKind::UnsupportedFeature).with_path(options.path)
            );
        }
    };

    Ok(OpenedDisk { image_type, disk })
}

fn open_vhdx(
    file: fs::File,