y BUG_ON
(we'll never get there with a NULL carrier_buf, and will crash if we do).
The bulk of this patch is rearranging structures so everything's declared
in the right order.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
]%