This series of patches finished "bugs fixing" mentioned
here http://lkml.org/lkml/2006/1/31/275 .

The main bugs:
* for i in `seq 1 1000`; do touch $i; done - crash system
* mkdir create directory without "." and ".." entries

The suggested solution is work with page cache instead of straight work
with blocks.  Such solution has following advantages

* reduce code size and its complexity
* some global locks go away
* fix bugs

The most part of code is stolen from ext2, because of it has similar
directory structure.

Patches testes with UFS1 and UFS2 file systems.

This patch installs i_mapping->a_ops for directory inodes and removes some
duplicated code.
Signed-off-by: NEvgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>