Don't reference the kiocb structure from the common aio code, and move
any use of it into helper specific to the read/write path.  This is in
preparation for aio_poll support that wants to use the space for different
fields.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NJeff Moyer <jmoyer@redhat.com>
Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>