0/15 IO scheduler improvements

Hi,

This is a continuation of the patches posted yesterday, I continued
to build on them. The patch series does:

- Move the hash backmerging into the elevator core.
- Move the rbtree handling into the elevator core.
- Abstract the FIFO handling into the elevator core.
- Kill the io scheduler private requests, that require allocation/free
  for each request passed through the system.

The result is a faster elevator core (and faster IO schedulers), with a
nice net reduction of kernel text and code as well.

If you have time, please give this patch series a test spin just to
verify that everything still works for you. Thanks!

 block/as-iosched.c       |  650 ++++++++++-------------------------------------
 block/cfq-iosched.c      |  498 +++++++++---------------------------
 block/deadline-iosched.c |  462 +++++----------------------------
 block/elevator.c         |  266 +++++++++++++++++--
 block/ll_rw_blk.c        |    9 
 include/linux/blkdev.h   |   29 +-
 include/linux/elevator.h |   32 ++
 include/linux/rbtree.h   |    2 
 lib/rbtree.c             |    6 
 9 files changed, 649 insertions(+), 1305 deletions(-)


--
Jens Axboe