DragonFlyBSD

Somehow my 120 GB HAMMER filesystem got into a situation where I couldn't
recover (mount r/w) anymore. Mounting it always failed with an "insufficient
undo FIFO space" panic. (See screenshots df-hammer{1-4}.png).

The only way to recover was to mount read-only and then copy to a new HAMMER
filesystem (see hammer-recovery-ro.png).

I tried with the most recent version of DragonFly (daily snapshot; i386), but
also with a 2.6 version.

Any thoughts why this could happen and what to do in this situation? It somehow
must have paniced the system while running for the first time, then paniced upon
reboot during HAMMER recovery.

Screenshots: http://leaf.dragonflybsd.org/~mneumann/hammer_insuff_fifo/