readahead cleanups and interleaved readahead

Andrew,

The following readahead updates have been tested and should be OK for 2.6.23 :-)

smaller file_ra_state:
[PATCH 1/6] compacting file_ra_state
[PATCH 2/6] mmap read-around simplification

code cleanups:
[PATCH 3/6] remove several readahead macros
[PATCH 4/6] remove the limit max_sectors_kb imposed on max_readahead_kb

support of interleaved reads:
[PATCH 5/6] introduce radix_tree_scan_hole()
[PATCH 6/6] basic support of interleaved reads

The diffstat is

 block/ll_rw_blk.c          |    9 ------
 include/linux/fs.h         |   13 ++++-----
 include/linux/mm.h         |    2 -
 include/linux/radix-tree.h |    2 +
 lib/radix-tree.c           |   34 ++++++++++++++++++++++++
 mm/filemap.c               |    6 ++--
 mm/readahead.c             |   48 +++++++++++++++++++----------------
 7 files changed, 72 insertions(+), 42 deletions(-)

Regards,
Fengguang Wu