In libc.info-23.gz from glibc-devel:

     When the sources are compiled with `_FILE_OFFSET_BITS == 64' this
     function is in fact `aio_return64' since the LFS interface
     transparently replaces the normal implementation.

 - Function: int aio_fsync64 (int OP, struct aiocb64 *AIOCBP)
     This function is similar to `aio_fsync' with the only difference
     that the argument is a reference to a variable of type `struct
     aiocb64'.

The first paragraph should say:

function is in fact `aio_fsync64' instead of `aio_return64'