readahead cleanups and interleaved readahead take 3

Andrew,

The following patches are based on yesterday's discussions, compiled and tested OK:

smaller file_ra_state:
[PATCH 1/7] readahead: compacting file_ra_state
[PATCH 2/7] readahead: mmap read-around simplification
[PATCH 3/7] readahead: combine file_ra_state.prev_index/prev_offset into prev_

code cleanups:
[PATCH 4/7] readahead: remove several readahead macros
[PATCH 5/7] readahead: remove the limit max_sectors_kb imposed on max_readahead_kb

support of interleaved reads:
[PATCH 6/7] radixtree: introduce radix_tree_scan_hole() [PATCH 7/7] readahead: basic support of interleaved reads

The diffstat is

 block/ll_rw_blk.c          |    9 -----
 fs/ext3/dir.c              |    2 -
 fs/ext4/dir.c              |    2 -
 fs/splice.c                |    2 -
 include/linux/fs.h         |   14 +++-----
 include/linux/mm.h         |    2 -
 include/linux/radix-tree.h |    2 +
 lib/radix-tree.c           |   34 ++++++++++++++++++++
 mm/filemap.c               |   17 +++++-----
 mm/readahead.c             |   58 +++++++++++++++++++----------------
 10 files changed, 86 insertions(+), 56 deletions(-)

Regards,
Fengguang Wu
--