Re: fsck updating but not fixing filesystem

[David Holland <dholland-tech%netbsd.org@localhost>]

On Mon, Aug 24, 2020 at 12:01:27PM +0100, David Brownlee wrote:
 > > > I think the general consensus is that ffs can be inconsistent it ways
 > > > fsck is unable to detect.
 > >
 > > ...much less fix.  Yes.  When I was doing the program that eventually
 > > got massaged into resize_ffs, during development I had some filesystems
 > > that were definitely corrupted but that fsck was happy with.  (I rather
 > > wish I'd saved some of them as test cases, but I didn't.)

I also once after abusing rename got a filesystem where fsck -y didn't
converge; I had to newfs it.

 > Sounds like there is an in interesting fuzzing project in there for
 > someone - make a filesystem mage and the repeatedly damage it, then
 > see if fsck can fix it, then if you get a rump panic when moving
 > everything around, and then re-run fsck to see if it indicates any new
 > issues :)

One can do that, but given that there are lots of edge cases and many
of them will be hard to reach, formal verification might be more
effective.

-- 
David A. Holland
dholland%netbsd.org@localhost