Re: panic: ffs_blkfree: freeing free block

Kostik Belousov wrote:
> 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.

Yes, exactly why I said 'it doesn't fix the problem'.  In fact, I 
actually did not post it to the list, and didn't intend for it to be 
posted.  I was hoping for feedback for further examination.

Kostik - do you have any ideas on what is going on here?  Did you see 
the message in another thread that looked similar (it was regarding 
gjournal)?

Eric