On Wed, 09 Jan 2008 07:40:12 +0300, Al Boldi said:

quoted text
> But why wouldn't it be possible to do this on the current fs infrastructure, 
> using just a smart fsck, working incrementally on some sub-dir?

If you have /home/usera, /home/userb, and /home/userc, the vast majority of
fs screw-ups can't be detected by only looking at one sub-dir.  For example,
you can't tell definitively that all blocks referenced by an inode under
/home/usera are properly only allocated to one file until you *also* look at
the inodes under user[bc].  Heck, you can't even tell if the link count for
a file is correct unless you walk the entire filesystem - you can find a file
with a link count of 3 in the inode, and you find one reference under usera,
and a second under userb - you can't tell if the count is one too high or
not until you walk through userc and actually see (or fail to see) a third
directory entry referencing it.