Uma estrutura FILE em C é geralmente chamada de file handle
e é um pouco de abstração em torno de < em> descritor de arquivo :
The data type FILE is a structure that contains information about a file or specified data stream. It includes such information as a file descriptor, current position, status flags, and more. It is most often used as a pointer to a file type, as file I/O functions predominantly take pointers as parameters, not the structures themselves.
Eu não tenho um ambiente de criação de kernel à mão, mas deve haver um texto de ajuda que explique a opção e, de acordo com a pesquisa rápida, ele deve dizer algo como:
CONFIG_FHANDLE - open by fhandle syscalls -
If you say Y here, a user level program will be able to map file names to handle and then later use the handle for different file system operations. This is useful in implementing userspace file servers, which now track files using handles instead of names. The handle would remain the same even if file names get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) syscalls.
Basicamente, ele adiciona suporte para chamadas de sistema novas / adicionais.