"ERROR 1030 (HY000): Got error 100" when adding index to very large (2B rows) table

[Steve Drangus]

I'm attempting to add an index to a very large table (2B rows) and the command fails after a few hours with:

ERROR 1030 (HY000): Got error 100 - 'InnoDB error' from storage engine

I'm finding the InnoDB 100 error code to be ungoogleable. It seems to be running out of some kind of resource, but the server has 128 GB of RAM and tons of disk space. Mysql isn't crashing.

I think maybe I need some config tweaks to give it more juice, but I don't know where to start.

Server version: Server version: 8.0.28 Db engine: InnoDB