panic: ffs_blkfree: freeing free block

[Kostik Belousov]

On Tue, Oct 16, 2007 at 12:20:59PM +0200, Arjan van Leeuwen wrote:
> 2007/10/16, Eric Anderson <anderson at freebsd.org>:
> >
> > Pieter de Goeje wrote:
> > > On Sunday 14 October 2007, Eric Anderson wrote:
> > >> Pieter de Goeje wrote:
> > >>> On Saturday 13 October 2007, Rolf Witt wrote:
> > >>>> Backtrace from crash tonight (after portsnap cron):
> > >>> <snip>
> > >>>
> > >>>> # uname -a
> > >>>> FreeBSD peanuts.homenet.local 7.0-PRERELEASE FreeBSD 7.0-PRERELEASE
> > >>>> #121: Thu Oct 11 16:29:05 CEST 2007
> > >>>> rowi at peanuts.homenet.local:/usr/obj/usr/src/sys/PEANUTS  i386
> > >>>>
> > >>>> Sources from Builddate.
> > >>>>
> > >>>> Rowi
> > >>> Eric sent me this patch:
> > >>> http://www.googlebit.com/freebsd/patches/ffs_softdep.c-patch
> > >>> which seems to be working great so far. I am still testing it, but I
> > >>> think it fixed the problem.
> > >>> To apply, cd /usr/src; patch < /path/to/patch and then rebuild the
> > >>> kernel.
> > >>>
> > >>> Cheers,
> > >>> Pieter de Goeje
> > >> It doesn't actually 'fix' the problem, but I think it helps identify
> > it.
> > >> I'm not 100% certain if this is the right fix our not, but so far
> > >> feedback has been good when running with this patch.
> > >>
> > >> Can somebody confirm that this patch is ok?
> > >>
> > >> Eric
> > > Can you elaborate on what this patch exactly does / what the problem is?
> > >
> > > Pieter
> >
> >
> > I think the problem is that blocks are being put in the worklist twice,
> > but I'm not certain why yet.  The patch reduces the chance of this
> > happening by more often removing the block from the worklist instead of
> > leaving it on.  I think actually the patch is hiding the real issue more
> > than anything, which is why I said it isn't fixing the problem, but
> > because of the reports I've seen, I think we're sniffing in the right
> > area.  I'll be looking more into this soon, when I get another few
> > minutes of free time and my debugger..
> 
> I actually seem to be getting the panic more often with the patch (i.e.
> twice in just 30 minutes with the patch, about twice per day without the
> patch), while doing the same things as usual. The panic usually happens when
> I'm compiling or linking. Is that strange?

Patch is wrong. Actually, it does put the dirrem to the proccessing twice
when xp != NULL.
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