8.0-BETA4 panic: ffs_sync: rofs mod

Hi,

My 8.0-BETA4/amd64 installation panicked when I attempted to create a
file on zvol-backed UFS.  This installation is otherwise UFS-free, ZFS
v13 w/gptzfsboot method linked from wiki, single zpool mirror
(ad{4,6}p3).

# zfs create -V 18G z0/ufs0
# newfs -U -L oldbender /dev/zvol/z0/ufs0
# mount /dev/ufs/oldbender /old
# touch /old/foo

The system usually panics immediately, but once it waited a few
seconds to do so, and I saw the file had been created.  The file was
not there upon reboot in all cases, and the filesystem was considered
clean by fsck.

Should I expect this to work?  And/or is it a known issue?  (Didn't
find any similar-looking problems by googling or browsing list
archives.)

Please let me know if I need to provide more details.

Jeff


console output:

fs = /old
panic: ffs_sync: rofs mod
cpuid = 1
KDB: enter: panic
[thread pid 19 tid 100049 ]
Stopped at      kdb_enter+0x3d: movq    $0,0x68d1e0(%rip)
db> bt
Tracing pid 19 tid 100049 td 0xffffff0002ad7000
kdb_enter() at kdb_enter+0x3d
panic() at panic+0x17b
ffs_sync() at ffs_sync+0x544
sync_fsync() at sync_fsync+0x13a
sync_vnode() at sync_vnode+0x157
sched_sync() at sched_sync+0x1d1
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffff8074cd7d30, rbp = 0 ---
db> 


kgdb upon reboot:

# kgdb /boot/kernel/kernel /var/crash/vmcore.1
GNU gdb 6.1.1 [FreeBSD]
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "amd64-marcel-freebsd"...

Unread portion of the kernel message buffer:
fs = /old
panic: ffs_sync: rofs mod
cpuid = 1
KDB: enter: panic
Physical memory: 4076 MB
Dumping 1396 MB: 1381 1365 1349 1333 1317 1301 1285 1269 1253 1237 1221 1205 1189 1173 1157 1141 1125 1109 1093 1077 1061 1045 1029 1013 997 981 965 949 933 917 901 885 869 853 837 821 805 789 773 757 741 725 709 693 677 661 645 629 613 597 581 565 549 533 517 501 485 469 453 437 421 405 389 373 357 341 325 309 293 277 261 245 229 213 197 181 165 149 133 117 101 85 69 53 37 21 5

Reading symbols from /boot/kernel/zfs.ko...Reading symbols from /boot/kernel/zfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/zfs.ko
Reading symbols from /boot/kernel/opensolaris.ko...Reading symbols from /boot/kernel/opensolaris.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/opensolaris.ko
Reading symbols from /boot/kernel/geom_mirror.ko...Reading symbols from /boot/kernel/geom_mirror.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/geom_mirror.ko
Reading symbols from /boot/kernel/linux.ko...Reading symbols from /boot/kernel/linux.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/linux.ko
Reading symbols from /boot/kernel/snd_hda.ko...Reading symbols from /boot/kernel/snd_hda.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/snd_hda.ko
Reading symbols from /boot/kernel/sound.ko...Reading symbols from /boot/kernel/sound.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/sound.ko
Reading symbols from /boot/kernel/atapicam.ko...Reading symbols from /boot/kernel/atapicam.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/atapicam.ko
Reading symbols from /boot/kernel/linprocfs.ko...Reading symbols from /boot/kernel/linprocfs.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/linprocfs.ko
Reading symbols from /boot/kernel/radeon.ko...Reading symbols from /boot/kernel/radeon.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/radeon.ko
Reading symbols from /boot/kernel/drm.ko...Reading symbols from /boot/kernel/drm.ko.symbols...done.
done.
Loaded symbols for /boot/kernel/drm.ko
#0  doadump () at pcpu.h:223
223     pcpu.h: No such file or directory.
        in pcpu.h
(kgdb) bt
#0  doadump () at pcpu.h:223
#1  0xffffffff801d90fc in db_fncall (dummy1=Variable "dummy1" is not available.
)
    at /usr/src/sys/ddb/db_command.c:548
#2  0xffffffff801d9431 in db_command (last_cmdp=0xffffffff80be9720, cmd_table=Variable "cmd_table" is not available.
)
    at /usr/src/sys/ddb/db_command.c:445
#3  0xffffffff801d9680 in db_command_loop ()
    at /usr/src/sys/ddb/db_command.c:498
#4  0xffffffff801db659 in db_trap (type=Variable "type" is not available.
) at /usr/src/sys/ddb/db_main.c:229
#5  0xffffffff805b2025 in kdb_trap (type=3, code=0, tf=0xffffff8074cd7880)
    at /usr/src/sys/kern/subr_kdb.c:535
#6  0xffffffff80864af1 in trap (frame=0xffffff8074cd7880)
    at /usr/src/sys/amd64/amd64/trap.c:613
#7  0xffffffff8084a7d3 in calltrap ()
    at /usr/src/sys/amd64/amd64/exception.S:224
#8  0xffffffff805b21fd in kdb_enter (why=0xffffffff8095cf97 "panic", 
    msg=0xa <Address 0xa out of bounds>) at cpufunc.h:63
#9  0xffffffff8058298b in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:562
#10 0xffffffff807a8cc4 in ffs_sync (mp=Variable "mp" is not available.
)
    at /usr/src/sys/ufs/ffs/ffs_vfsops.c:1261
#11 0xffffffff80615cda in sync_fsync (ap=Variable "ap" is not available.
) at /usr/src/sys/kern/vfs_subr.c:3433
#12 0xffffffff80614197 in sync_vnode (slp=0xffffff00029f14a8, 
    bo=0xffffff8074cd7bf0, td=0xffffff0002ad7000) at vnode_if.h:549
#13 0xffffffff80614401 in sched_sync () at /usr/src/sys/kern/vfs_subr.c:1799
#14 0xffffffff8055a73a in fork_exit (callout=0xffffffff80614230 <sched_sync>, 
    arg=0x0, frame=0xffffff8074cd7c80) at /usr/src/sys/kern/kern_fork.c:838
#15 0xffffffff8084acae in fork_trampoline ()
    at /usr/src/sys/amd64/amd64/exception.S:561
#16 0x0000000000000000 in ?? ()
#17 0x0000000000000000 in ?? ()
#18 0x0000000000000001 in ?? ()
#19 0x0000000000000000 in ?? ()
#20 0x0000000000000000 in ?? ()
#21 0x0000000000000000 in ?? ()
#22 0x0000000000000000 in ?? ()
#23 0x0000000000000000 in ?? ()
#24 0x0000000000000000 in ?? ()
#25 0x0000000000000000 in ?? ()
#26 0x0000000000000000 in ?? ()
#27 0x0000000000000000 in ?? ()
#28 0x0000000000000000 in ?? ()
#29 0x0000000000000000 in ?? ()
#30 0x0000000000000000 in ?? ()
#31 0x0000000000000000 in ?? ()
#32 0x0000000000000000 in ?? ()
#33 0x0000000000000000 in ?? ()
#34 0x0000000000000000 in ?? ()
#35 0x0000000000000000 in ?? ()
#36 0x0000000000000000 in ?? ()
#37 0x0000000000000000 in ?? ()
#38 0x0000000000000000 in ?? ()
#39 0x0000000000000000 in ?? ()
#40 0x00000000012d7000 in ?? ()
#41 0x0000000000000000 in ?? ()
#42 0xffffffff80c25840 in affinity ()
#43 0xffffffff80c25840 in affinity ()
#44 0xffffff0002802390 in ?? ()
#45 0xffffff8074cd74e0 in ?? ()
#46 0xffffff8074cd7498 in ?? ()
#47 0xffffff0002ad7000 in ?? ()
#48 0xffffffff805a57e0 in sched_switch (td=0x0, newtd=0xffffffff80614230, 
    flags=Variable "flags" is not available.
) at /usr/src/sys/kern/sched_ule.c:1858
Previous frame inner to this frame (corrupt stack?)
(kgdb)