Ocfs2 devel - Feb 2010 - du_enhancement: add the shared extents and footprint statitics support v2

Hello,

Changes from v1:

1. Add more comments for split_extent() and fix a few bugs in this function
based on Tao's comments.
2. Call openat(2) instead of open(2) first to get the file handler in
process_extent(), call open(2)
against the full path name will fail when its length is longer than PATH_MAX.
for unreadable file we
have to call open(2) instead.

I have done some simple tests, it works well. Any comments or tests help are
appreciated!


Regards,
-Jeff