Possible Filesystem Corruption

[Matthew Dillon]

:> 
:>    
:> :        /bin/pwd : 1 syntax error: ``( '' unexpected
:...
:> :   panic. I didn't know what to do at db> but typing panic ? got me a
:> :   reboot and the subsequent fsck seems to have fixed everything I can
:> :   check. There was something about a SUPERBLOCK but it was too fast for
:> :   me to record. Not all filesystems were checked probably because the
:> :   system was already in single user mode when it paniced ?.
:> :
:> : Here is the panic FYI, it is hand transcribed.
:> :
:> :syncing disks... 2
:> :done
:> :panic: umount: dangling vnode
:> :Trace beginning at frame 0xc5423ae0
:> :panic(c04f58af,c05b14a0,c04f7fc7,c5423b10,0) at panic+0x99
:> :dounmount(c0df6588,80000,c5420f00,1,c0df6588) at dounmount+0x23a
:> :...
:> :                               Hope this helps,
:> :                                  John Duncan
:> 
:>     It kinda sounds like something got smashed in your filesystem, but
:>     the problem needs to be characterized more as I do not have any
:...
:
:16 partitions:
:#        size   offset    fstype   [fsize bsize bps/cpg]
:  a:   524288        0    4.2BSD     1024  8192    22 	# (Cyl.    0 - 32*)
:  b:   524288   524288      swap                    	# (Cyl.   32*- 65*)
:  c: 30713634        0    unused        0     0       	# (Cyl.    0 - 1911*)
:  d:   524288  1048576    4.2BSD     1024  8192    22 	# (Cyl.   65*- 97*)
:  e:   524288  1572864    4.2BSD     1024  8192    22 	# (Cyl.   97*- 130*)
:  f: 16777216  2097152    4.2BSD     2048 16384    89 	# (Cyl.  130*- 1174*)
:  g: 11839266 18874368    4.2BSD     1024  8192    22 	# (Cyl. 1174*- 1911*)
:
:      f which is /usr looks a little strange ?

    All looks ok.

:>     Are you getting any disk error messages in the dmesg output or
:>     on the console during shutdown/reboot ?
:
:      No, though when booting I get CRC errors but FreeBSD gives me
:      them as well and also drops DMA, but NetBSD and OpenBSD operate in
:      DMA mode without a problem. At the moment I also have Debian
:      Stable on this disk as well, no problems.

    Well, this isn't good.  Do you have crash dumps turned on?  The dangling
    vnode shouldn't happen unless there is some previous unrecoverable error
    that led to it.  The CRC errors could easily be blamed for the corruption
    (you shouldn't be getting CRC errors, period), but not for the dangling
    vnode panic.

    I would try degrading the DMA mode at boot, or even trying PIO mode (but
    degrade the DMA mode first).

    If you do a 'man ad' (I'm assuming the device in question is the IDE 
    controller) you should be able to set a tunable in /boot/loader.conf
    to turn off DMA mode for testing purposes.  You can use the 'atacontrol'
    program to change the mode on the fly after the system has booted (though
    it's fairly dangerous to do so).

:>     Also note that HEAD is going a lot of changes right now, though
:>     nothing we are doing should have the effect you've described.
:
:            Yes I know, I am running HEAD to try to learn something,
:            nothing ever goes wrong with Preview or Release for me but I
:            might be over my head.
:
:                                       All the best,
:                                         John Duncan

    The disk drivers haven't changed much since release so I double that
    RELEASE/Preview/Development will change the issues.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>