To make use of the registered files, the IOSQE_FIXED_FILE flag must be set in the flags
member of the SubmissionEntry, and the fd member is set to the index of the file in the
file descriptor array.
Files are automatically unregistered when the io_uring instance is torn down. An application
need only unregister if it wishes to register a new set of fds.
Use -1 as a file descriptor to mark it as reserved in the array.*
Register files for I/O.
To make use of the registered files, the IOSQE_FIXED_FILE flag must be set in the flags member of the SubmissionEntry, and the fd member is set to the index of the file in the file descriptor array.
Files are automatically unregistered when the io_uring instance is torn down. An application need only unregister if it wishes to register a new set of fds.
Use -1 as a file descriptor to mark it as reserved in the array.*