Re: panic: ffs_blkfree: freeing free block

Backtrace from crash tonight (after portsnap cron):

# kgdb kernel.debug /var/crash/vmcore.1
kgdb: kvm_nlist(_stopped_cpus):
kgdb: kvm_nlist(_stoppcbs):
[GDB will not be able to debug user-mode threads:
/usr/lib/libthread_db.so: Unde                       fined symbol
"ps_pglobal_lookup"]
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This GDB was configured as "i386-marcel-freebsd".

Unread portion of the kernel message buffer:
dev = ad4s1f, block = 26098960, fs = /usr
panic: ffs_blkfree: freeing free block
Uptime: 1d10h32m17s
Physical memory: 631 MB
Dumping 150 MB: 135 119 103 87 71 55 39 23 7

#0  doadump () at pcpu.h:195
195             __asm __volatile("movl %%fs:0,%0" : "=r" (td));
(kgdb) backtrace
#0  doadump () at pcpu.h:195
#1  0xc06328a3 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:409
#2  0xc0632aa4 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:563
#3  0xc07d4d10 in ffs_blkfree (ump=0xc323ab00, fs=0xc321c800,
    devvp=0xc328add0, bno=26098960, size=16384, inum=6500370)
    at /usr/src/sys/ufs/ffs/ffs_alloc.c:1893
#4  0xc07e8588 in indir_trunc (freeblks=0xc3e12500, dbn=103954304, level=0,
    lbn=12, countp=0xd9177c4c) at /usr/src/sys/ufs/ffs/ffs_softdep.c:2896
#5  0xc07e8850 in handle_workitem_freeblocks (freeblks=0xc3e12500, flags=0)
    at /usr/src/sys/ufs/ffs/ffs_softdep.c:2746
#6  0xc07ea0d8 in process_worklist_item (mp=0xc324b7d4, flags=Variable
"flags" is not available.
)
    at /usr/src/sys/ufs/ffs/ffs_softdep.c:963
#7  0xc07eb191 in softdep_process_worklist (mp=0xc324b7d4, full=0)
    at /usr/src/sys/ufs/ffs/ffs_softdep.c:847
#8  0xc07ed70a in softdep_flush () at /usr/src/sys/ufs/ffs/ffs_softdep.c:758
#9  0xc06121d1 in fork_exit (callout=0xc07ed290 <softdep_flush>, arg=0x0,
    frame=0xd9177d38) at /usr/src/sys/kern/kern_fork.c:796
#10 0xc0850170 in fork_trampoline () at
/usr/src/sys/i386/i386/exception.s:205
(kgdb)

# 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