[9fans] fossil file system corrupts after a power cut

[kin loo <kinloo88@gmail.com>]

Hello everyone. I have two PCs, one of which installs Plan 9 system
functioning as a backup server by Venti; the other one installs Debian
6, using qemu to run a virtual Plan 9 fossil+cpu/auth server (because
Plan 9 can't recognize hard disk for this machine). Both the backup
and virtual servers run well lasting for a week. Today a power cut
occurs, I turn on the back server first in turn the virtual server.
The back server runs as usual, but the virtual server corrupts (the
Debian host and qemu are normal). So  I boot the virtual server from a
Plan 9 CD, typing some commands in order to restore the last archive
of the system. The commands are:

    term% fossil/last /dev/sdC0/fossil
    vac:da39a3ee5e6b4b0d3255bfef95601890afd80709
    term% ip/ipconfig -g 192.168.1.1 ether /net/ether0 192.168.1.233
255.255.255.0
    term% ndb/dns -r
    term% venti=192.168.1.160
    term% fossil/flfmt -v da39a3ee5e6b4b0d3255bfef95601890afd80709 /
dev/sdC0/fossil
    fs header block already exists; are you sure? [y/n]: y
    fatal error: corrupted root: vtRootUnpack

I don't know what's going wrong. So I boot the virtual server from
qemu disk in Debian as normal:

    kin@debian: ~$ sudo qemu -hda plan9.qcow2.img -net
nic,model=rtl8139 -net \
    > tap,ifname=tap0,script=qemu-ifup

but the virtual server still prompts errors at boot time. The error
messages are:

    root is from (tcp, local)[local!#S/sdC0/fossil]:
    time...
    fossil/(#S/sdC0/fossil)...fsys: dialing venti at tcp!192.168.1.160!
17034
    /boot/fossil: cacheLocalData: addr=1 type got 0 exp 8: tag got 0
exp 1
    /boot/fossil: fsOpen error
    fsOpen: block label mismatch
    fsys main open -AWP: fsOpen: block label mismatch
    fsys: 'main' not open
    fsys main: fsys: 'main' not open
    version...bot: mount /: fsys: 'main' not open
    panic: boot process died: unknown
    panic: boot process died: unknown
   dumpstack disabled
   cpu0: exiting