I ran into this on OpenWRT back in the day. It had a similar filesystem behavior where you could not delete from a full FS. The solution was to truncate a file

I ran into this on OpenWRT back in the day. It had a similar filesystem behavior where you could not delete from a full FS. The solution was to truncate a file that was at least 1 block big, thus freeing up a few kilobytes. Then you can rm a large file, and then you can resume normal cleanup.