aio_fsync() shall asynchronously force I/O operations associated with aio_fildes. if op is O_DSYNC, all queued I/O operations shall be completed as if by a call to fdatasync(). if op is O_SYNC, all queued I/O operations shall be completed as if by a call to fsync(). aio_error() and aio_return() may be used in order to determine the error status and return status of aio_fsync opertation. When the request is queued, error status is [EINPROGRESS]. If the operation does not complete successfully, the error status shall be set to indicate the error. The aio_sigevent member determines the asynchronous notificiation to occur. Except aio_fildes and aio_sigevent, all other members of the structure are ignored. aio_fsync() shall return the value 0 if the operation is successfully queued. aio_fsync() shall return the value -1 and set errno to indicate error if the operation is not successfully queued. aio_fsync() shall fail if: [EAGAIN] Operation was not queued due to temporary resource limitations. aio_fsync() shall fail if: [EBADF] aio_fildes is not a valid file descriptor for writing. aio_fsync() shall fail if: [EINVAL] This implementation does not support synchronized I/O for this file. aio_fsync() shall fail if: [EINVAL] op is not set to O_DSYNC or O_SYNC.