Hi all,
I know nullfs is not to be relied upon, but I did hit an interesting bug
the other day, and I was wondering if I should bother with a PR or not.
In short, doing the following seems to dirty the partition and leave the
machine in a state where a hard reset is required to recover. This is
-stable from 1/4/06.
-start a jail within a partition dedicated to jails, in my case it looks
like:
/jails
/jails/jail1
/jails/jail2
etc...
-use nullfs to link the host's ports tree into the jail:
mount_nullfs /usr/ports /jails/jail1/usr/ports
-enable quotas for the /jails partition
-stop the jails and run quotacheck to make sure everything is consistent
quotacheck -v /jails
At that point, the quotacheck command seems to deadlock on something. The
process is not interruptible (ie: CTRL-C, CTRL-Z do not do anything but
echo) even with a "kill -9" from the host.
Any subsequent command that attempts to read anything from that partition
will also hang as above.
If a shutdown is issued, that does not kill off any of the deadlocked
processes and the machine must be manually reset (something of a pain if
it's remote).
In order to get a clean boot I had to remove all jail startup commands
from rc.conf and make sure nothing else (like syslog) was trying to do
anything in /jails. Even then, the background fsck eventually deadlocked
as well. I had reboot once more with /jails commented out of fstab and
then run the fsck manually to recover.
Should I write this up and send it in case one day someone decides to fix
nullfs?
I'm also wondering about the seperate issue of having some deadlocked
process not allowing the machine to reboot - I've seen similar reports of
this behaviour with various other less-than-stable filesystems like vfs.
It would be nice to have some way of telling the kernel "please stop
waiting on this disk, it's not coming back, it's futile, please just
reboot".
Thanks,
Charles
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