Function libe2fs_sys::ext2fs_set_alloc_block_callback

pub unsafe extern "C" fn ext2fs_set_alloc_block_callback(
    fs: ext2_filsys,
    func: Option<unsafe extern "C" fn(fs: ext2_filsys, goal: blk64_t, ret: *mut blk64_t) -> errcode_t>,
    old: *mut Option<unsafe extern "C" fn(fs: ext2_filsys, goal: blk64_t, ret: *mut blk64_t) -> errcode_t>
)