Re: UFS2 Snapshots in 6.1-Beta4 - Confirmed Problems

On Thu, 23 Mar 2006, Kris Kennaway wrote:

> On Tue, Mar 21, 2006 at 01:36:44AM -0800, John Kozubik wrote:
>
> > First, I have confirmed that a filesystem with multiple snapshots that
> > undergoes multiple, rapid deletions of files, will cause the system to
> > hang.  I have witnessed this before, but had not confirmed it or
> > documented it in a PR.  Now that I have confirmed this behavior, I have
> > documented it in: kern/94769
>
> I ran a (completion of) your script in a loop for about 24 hours and
> it didn't deadlock.  This may be because there was a second set of
> fixes that was merged in to 6.x a day or two ago.  Are you able to
> confirm whether they indeed fixed this problem?

What ratio of snapshots / rms did you run ?  I reproduced this easily on
6.0-RELEASE and 6.1-BETA4.  I am traveling right now and cannot test on
anything newer.  Can you try it on one of the two above, confirm for
yourself that it manifests itself, and then compare that to what you see
on whatever newer code you have ?  If it is fixed, that's great.

> > Second, kern/92292 is still a problem.  I have reproduced this error in
> > 6.1-BETA4 (and have seen it happening since 5.1).  The (small) difference
> > is that the cp process seems to stick in the flswai state instead of
> > biowr.
>
> I'll test this one next.


Great - thanks.  It's less urgent, as running a md-backed FS on a
snapshotted FS is less common, and easily avoided.  The big fish are the
rm problems (you can't avoid deleting things) and the "full filesystem"
problems, since there is always a danger of that.

-----
John Kozubik - john_at_kozubik.com - http://www.kozubik.com