tmpfs: ZERO_RANGE and COLLAPSE_RANGE not currently supported
I was well aware of FALLOC_FL_ZERO_RANGE and FALLOC_FL_COLLAPSE_RANGE
support being added to fallocate(); but didn't realize until now that I
had been too stupid to future-proof shmem_fallocate() against new
additions. -EOPNOTSUPP instead of going on to ordinary fallocation.