This bug appears as "incorrect Mod Counters" in 'raidctl -s'. The
reason it was seen only in 'raidctl -s' is because of the conditions
needed to trigger the bug:
a) a raid set is configured
b) no partitions on that set are mounted or are otherwise in-use
c) a component is failed, and subsequently rebuilt to a hot spare
d) the machine is rebooted while something (e.g. 'raidctl -s') has
the device open (and, therefore, rf_markalldirty() has been called)
but before the final rf_update_component_labels() is done.
Needless to say, the window for this happening is *very* small, and it
was only because I was testing some obscure stuff that I even noticed it.
56f6918fef