any way to recover from I/O hang?

Recently I'm again facing a situation where some UFS (?) error on one partition forced me to reboot whole server and interrupt people's work.
As I understand the brief is:

Reason: A process in state 'D' (uninterruptible wait/sleep) is blocked on an I/O operation (e.g., waiting for a network file share, a disk operation, or a device that is no longer responding) at the kernel level. The process is not awaken to handle signals until the condition it is waiting for is resolved.
Solution: You cannot kill a 'D' state process with any signal, including SIGKILL (kill -9). The condition must be resolved (e.g., fixing the network connection, waiting for the I/O to time out, or potentially unmounting the filesystem with umount -f if it's a mounted network share). In some rare cases involving buggy kernel code or hardware failure, a reboot may be the only option.

In my case there was a jailed samba which share one ufs-formatted partition. The samba processes hangs one by one and sharing has stopped it work.
There was no message in log. Geom reported no errors. Disk's has no error. It seems that there was some introduced inconsistency in UFS.
My thoughts was to stop/kill samba, remove samba's jail, unmount partition and do fsck.

But 'jail -r' exit with something 'rc.shutdown exited ... 9' and left jail running. pskill -KILL for samba processes say nothing and do nothing.
'umount -f' say 'Device is busy'. Various utilities such as 'df' hangs. So I forced to shutdown the server which has other important and workable service to resolve the situation.

I wander is there any way to treat such a cases? May be 'umount -f' can have more power...


P.S. Previous situation was when I do simple (as I think) experiments with ggated and have forced to reboot server when 'mount' hung.

-- 
Best regards,
 Anthony Pankov                         mailto:anthony.pankov@yahoo.com