dfly-2.0.0-REL: panic: hammer: insufficient undo FIFO space!
Ok I've tracked it down. There are two issues, both related to the
fact that the filesystem is really small.
The main bug is actually with newfs_hammer. When a small filesystem
is created newfs_hammer reserves way too small a space for the UNDO
FIFO. A 6G filesystem only reserves 8M of undo space! That isn't
enough. 100M is really the minimum. I am going to change newfs_hammer
to enforce that.
The second issue is that the filesystem is really too small. I don't
want to disallow the creation of small filesystem but I think I will
also change newfs_hammer to spit out a bunch of warnings when people
create such small filesystems.
Finally, keep in mind that you may hit up against serious free space
issues and may have to run 'hammer prune-everything ...' as well
as 'hammer reblock ...' quite often on such a small filesystem,
depending on use.