I did not write the information down, but I'm fairly certain I
experienced this multiple times within the last 2-3 days using a large
LFS root partition.  I have not gotten it using FFSv[12].

I had intended on switching over to an LFS root, but gave up because
of this plus [what seemed to be] deadlocks.

If it would help I will partition off some space and get a backtrace
(this is amd64 and I wasn't running a kernel built with
-fno-omit-frame-pointer) and line information.