Snapshot corruption on 6.1/amd64

[Lapo Luchini]

Kris Kennaway wrote:
>> Anyway, after having de-activated all snapshots for weeks (and deleted
>> all the old ones) I got this panic again.
> I've lost context, how are you reproducing the panic?

I didn't "reproduce" it, it kinda did just happen...

Context: I used snapshots for a couple of months without problems, then
got a panic a couple of weeks ago, I deleted all the snaps, I
deactivated the periodic snapshot script, and yesterday, 7 in the
morning, it just panicked again.

The original panic was a few seconds after a snapshot creation, the
latest one in the middle of nothing: 7 in the morning the are no users
and no tasks scheduled.

Parts of /var/log/message:

[...]
Nov 22 05:56:49 motoko ntpd[668]: kernel time sync enabled 2001
Nov 22 06:30:58 motoko ntpd[668]: kernel time sync enabled 6001
Nov 22 06:48:03 motoko ntpd[668]: kernel time sync enabled 2001
Nov 22 07:22:22 motoko syslogd: kernel boot file is /boot/kernel/kernel
Nov 22 07:22:22 motoko kernel: Copyright (c) 1992-2006 The FreeBSD Project.
[...]
Nov 22 07:22:22 motoko savecore: reboot after panic: page fault
Nov 22 07:22:22 motoko savecore: no dump, not enough free space on
device (87803
6 available, need 1031746)
Nov 22 07:22:22 motoko savecore: unsaved dumps found but not saved
[...]
Nov 22 07:25:33 motoko kernel: panic: snapacct_ufs2: bad block
Nov 22 07:25:33 motoko kernel: Uptime: 3m27s
Nov 22 07:25:33 motoko kernel: Dumping 1007 MB (2 chunks)
Nov 22 07:25:33 motoko kernel: chunk 0: 1MB (159 pages) ... ok
Nov 22 07:25:33 motoko kernel: chunk 1: 1007MB (257776 pages) 991 975
959 943 [...] 31 15 ... ok
Nov 22 07:25:33 motoko kernel:
Nov 22 07:25:33 motoko kernel: Dump complete
Nov 22 07:25:33 motoko kernel: Automatic reboot in 15 seconds - press a
key on the console to abort
Nov 22 07:25:33 motoko kernel: Copyright (c) 1992-2006 The FreeBSD Project.
[...manual fsck in single user...]
Nov 22 15:44:51 motoko kernel: Trying to mount root from ufs:/dev/ad0s1a
Nov 22 15:44:51 motoko kernel: ffs_snapshot_mount: non-snapshot inode 9
Nov 22 15:44:51 motoko savecore: reboot after panic: snapacct_ufs2: bad
block
Nov 22 15:44:51 motoko savecore: writing compressed core to vmcore.2.gz

...and this is the dump info (/var/crash/info.2):
Dump header from device /dev/ad0s1b
  Architecture: amd64
  Architecture Version: 2
  Dump Length: 1056505856B (1007 MB)
  Blocksize: 512
  Dumptime: Wed Nov 22 07:23:54 2006
  Hostname: motoko.lapo.it
  Magic: FreeBSD Kernel Dump
  Version String: FreeBSD 6.1-STABLE #4: Fri Sep  1 17:02:50 CEST 2006
    root at motoko.lapo.it:/usr/obj/usr/src/sys/MOTOKO
  Panic String: snapacct_ufs2: bad block
  Dump Parity: 3615879487
  Bounds: 2
  Dump Status: good

This night I updated to 6.2-PRERELEASE, which contains the latest
amd64-snapshot commit... hoping for the good.
'Good' as in:
- in the short term: no more panics
- in the long term: to use the snapshot functionality again

Hope this is context enough, or else simply ask and I'll reply. =)