[PATCH] aio: reorder kiocb structure elements to make sync iocb setup faster

Reorder members of the kiocb structure to make sync kiocb setup faster.  By
setting the elements sequentially, the write combining buffers on the CPU
are able to combine the writes into a single burst, which results in fewer
cache cycles being consumed, freeing them up for other code.  This results
in a 10-20KB/s[*] increase on the bw_unix part of LMbench on my test
system.

* The improvement varies based on what other patches are in the system,
  as there are a number of bottlenecks, so this number is not absolutely
  accurate.

Signed-off-by: Benjamin LaHaise <benjamin.c.lahaise@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>