I don't understand what ENOSPC has to do with the file descriptor
limits, but this person reported:
# touch test
touch: cannot touch ‘test’: No space left on device
https://serverfault.com/questions/746032/rsync-and-scp-failing-with-no-space-left-on-xfs-device
... with plenty of free space, and it went away with ulimit -Hn and
-Sn changes. Huh? Could this have failed in FileAcces() when trying
to re-open a vfd?