swap/page problem

During a large build (llvm13), my system ground to a near halt with almost
everything suspended. After several minutes, the system slowly recovered.
When I looked at the messages log, I found 57 kernel messages spread over
3.75 hours, in the form of:
wap_pager: indefinite wait buffer: bufobj: 0, blkno: 862845, size: 20480

The block numbers and sizes varied. bufobj was always '0'. I had
significant swap available swap space,as far as I could tell. I have 20GB
of RAM and 24GB of swap. I am running stable 48937-3c6b6246f2f from January
13.

I know that the LLVM build is huge, but I've not seen this before. What,
exactly, is this message telling me? Am I out of RAM and swap? I couldd add
another 24GB of swap, though it would be on spinning rust, not SSD.

Thanks!
-- 
Kevin Oberman, Part time kid herder and retired Network Engineer
E-mail: rkoberman@gmail.com
PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683