Currently we only support registrering a fixed file set. If changes need to be made to that set, the application must unregister the existing set first, then register a new one. This patchset adds support for sparse file sets (patch 1), which means the application can register a fileset with room for expansion. This is done through having unregistered slots use fd == -1. On top of that, we can add IORING_REGISTER_FILES_UPDATE. This allows modifying the existing file set through: - Replacing empty slots with valid file descriptors - Replacing valid descriptors with an empty slot - Modifying an existing slot, replacing a file descriptor with a new one -- Jens Axboe
