This looks better, but there are still some issues:

The patch arrived here with tabs expanded into spaces, so it doesn't apply.

The EAGAIN fix by Mingming Cao is obviously incomplete, as I've 
mentioned in a separate message to linux-aio.  I think it would be 
better if you would leave this out of this patch and let it be handled 
separately.

async_poll_complete() is dead code and should be removed (this was an 
issue in the original 2.4.19 code).

You should not reintroduce the ki_data member of struct iocb.  Insead 
you should use the existing private member of struct iocb.

In aio_abi.h, you should adjust the preceeding comment to remove mention 
of IOCB_CMD_POLL.

Incidentally, this patch depends on the sys_io_cancel() portion of the 
patch I posted yesterday in order for cancellation to return the correct 
result to user space.