free space map and visibility map

With some intensive crash-recovery testing, I've run into a situation where
I get some bad table bloat. There will be large swaths of the table which
are empty (all results from heap_page_items other than lp are either zero
or NULL), but have zero available space in the fsm, and are marked as
all-visible and all-frozen in the vm.

I guess it is a result of a crash causing updates to the fsm to be lost.
Then due to the (crash-recovered) visibility map showing them as all
visible and all frozen, vacuum never touches the pages again, so the fsm
never gets corrected.

'VACUUM (DISABLE_PAGE_SKIPPING) foo;' does fix it, but that seems to be
the only thing that will.

Is there a way to improve this, short of making updates to the fsm be a
wal-logged operation?

It is probably not a very pressing issue, as crashes are normally pretty
rare, I would hope. But it seems worth improving if there is a good way to
do so.

Cheers,

Jeff