open64 is a short-hand for open with the flag O_LARGEFILE.
Here's the summary of the new interfaces:
aio(aio_read64,...): The aio structure contains an offset field
locking(flock64,fcntl): support for locking ranges of a file
pointer(ftell,fseek...): offset is 64 bits
dir access(readdir,ftw): d_ion is 64 bits
info(stat,statfs,...): file size, number of blocks, number of files, ...
mmap: mapping ranges
resource limits(getrlimit): maximum file size per process
A new mount option 'nolargefiles' denies mounting file systems if
the fs driver cannot guarantee that all files are small.
Regards,
Martin