设置 falloc 模式时会有提示 file-allocation=falloc will use SetFileValidData() API, and aria2 uses uninitialized disk space which may contain confidential data as the download file space. If it is undesirable, --file-allocation=prealloc is slower, but safer option.
The SetFileValidData function allows you to avoid filling data with zeros when writing nonsequentially to a file. The function makes the data in the file valid without writing to the file. As a result, although some performance gain may be realized, existing data on disk from previously existing files can inadvertently become available to unintended readers. The following paragraphs provide a more detailed description of this potential security and privacy issue. A caller must have the SE_MANAGE_VOLUME_NAME privilege enabled when opening a file initially. Applications should call SetFileValidData only on files that restrict access to those entities that have SE_MANAGE_VOLUME_NAME access.