Looks like it's trying to print a zero. I made a diff to print out the
raw numbers, and did indeed get zero.
Now, *why* it is printing a zero is another matter (as is why using
ffz() instead of ilog2() there...). Some quick investigation showed
that sdkp->capacity is a 32-bit quantity in this configuration, and
shifting it left by 9 of course ends up with zero; being a virtual disk,
it's an exact power of two.
Still, it is bad that string_get_size() hangs on passing zero.
The spinlock lockup is still happening, so I'm assuming it is an
unrelated bug that was masked by the string_get_size issue.
Patch series will follow shortly.