A FUSE interrupt is not a process kill. Go's async preemption (SIGURG)
makes a close() under load emit an interrupt on nearly every flush, so
deriving the metadata-flush context from the FUSE cancel channel turned
healthy concurrent close()s into EIO: the interrupt cancelled the
in-flight CreateEntry, which surfaced as "input/output error".
Bound the flush with a deadline instead. A healthy CreateEntry finishes
in well under a second, so the deadline only fires against a genuinely
stuck filer -- still keeping close() from hanging forever -- while
benign preemption no longer aborts a good flush.
Chris Lu
0f1ec8983d