VERY frustrated with FreeBSD/UFS stability - please help or comment...

[Rick C. Petty]

On Mon, May 21, 2007 at 03:56:34PM -0400, Kris Kennaway wrote:
> > 
> > The one thing I *have* experienced is filesystems going nuts after
> > filling them. Specifically I end up with a negative amount of space
> > free, and as soon as you release more space df -h quickly reports the
> > amount of free space dropping (you can see it interactively churning for
> > a few secs) until it settles at some negative amount again and you're
> > back to square one. This has happened once or twice in the past, but not
> > recently. Not sure which release it did happen on; might have been 5.x.
> 
> Yeah, this was an old bug in the 5.x timeframe.  As far as I recall it
> was fixed at some point in the past.

Hmm, this recently happened to me in 6.2-STABLE.  I was unable to replicate
it so filing a PR was pointless.  What I saw happen was that /usr filled up
completely (I caught it before it hit 100% full, but watched helplessly as
it switched from time to space optimization).  I even did a "du -hd0 /usr"
and saw it only using about 20% of the file system.  lsof and fstat weren't
terribly helpful.  After shutting down to single-user mode, I saw it full
even though I deleted a lot of superfluous files, and du/df differences
were still present.  I restarted and fsck cleaned up the 80% "used" space,
stating the superblock free maps were incorrect, which explains the
discrepency.  Why it happened, I'm still baffled.

-- Rick C. Petty