* AIO read and write on files opened without O_DIRECT (i.e. normal buffered filesystem AIO). On ext2, ext3, jfs, xfs and nfs, these do not return an explicit error, but quietly default to synchronous or rather non-AIO behaviour (i.e io_submit waits for I/O to complete in these cases). For most other filesystems, -EINVAL is reported.
* AIO fsync (not supported for any filesystem)
* AIO read and write on sockets (doesn't return an explicit error, but quietly defaults to synchronous or rather non-AIO behavior)
* AIO read and write on pipes (reports -EINVAL)
* Not all devices (including TTY) support AIO (typically return -EINVAL)