mmap read-around and readahead take 2

Andrew,

Here are the mmap read-around related patches initiated by Linus. They are for linux-2.6.24-rc5-mm1. They're mainly about code cleanups. The only major new feature - auto detection and early readahead for mmap sequential reads - shows about 2% speedup on single stream case, and should perform much better in multiple streams case.

This take: simplified patch 2, from

         mm/filemap.c |  192 +++++++++++++++++++++++++++++++++++++++-------------------
         1 files changed, 130 insertions(+), 62 deletions(-)
to
	 mm/filemap.c |  156 +++++++++++++++++++++++++++----------------------
	 1 file changed, 89 insertions(+), 67 deletions(-)

[PATCH 1/9] readahead: simplify readahead call scheme
[PATCH 2/9] readahead: clean up and simplify the code for filemap page fault readahead [PATCH 3/9] readahead: auto detection of sequential mmap reads
[PATCH 4/9] readahead: quick startup on sequential mmap readahead
[PATCH 5/9] readahead: make ra_submit() non-static
[PATCH 6/9] readahead: save mmap read-around states in file_ra_state [PATCH 7/9] readahead: remove unused do_page_cache_readahead()
[PATCH 8/9] readahead: move max_sane_readahead() calls into force_page_cache_readahead() [PATCH 9/9] readahead: call max_sane_readahead() in ondemand_readahead()

Thank you,
Fengguang