`IN_Q_OVERFLOW` arrives with watch descriptor -1, so the path lookup
failed and the event was silently discarded. It is now delivered
with an empty path so consumers can rescan after the kernel dropped
events.
inotify exposes a /proc interface to limit kernel memory usage. If those
limits are set too low, inotify cannot add all watches. The integration
test verifies, that Inotify yields an error in that case.
T. R. Bernstein