We used to have "first Translate() wins". This is not deterministic,
as the LOOKUP for the root directory does not seem to reach us, so
the first user LOOKUP would win, which may be on a mountpoint.
Adding flags allows to use inomap in reverse mode,
replacing the clunky inoBaseDirIV/inoBaseNameFile
logic that causes problems with high underlying
inode numbers ( https://github.com/rfjakob/gocryptfs/issues/457 )
Microbenchmarks (values below) show that the "SingleDev"
case is now much slower due to an extra map lookup,
but this has no visible effects in ./test.bash results,
so there was no time spent optimizing the case further.
$ go test -bench=.
goos: linux
goarch: amd64
pkg: github.com/rfjakob/gocryptfs/internal/inomap
BenchmarkTranslateSingleDev-4 18757510 61.5 ns/op
BenchmarkTranslateManyDevs-4 18061515 64.5 ns/op
PASS
ok github.com/rfjakob/gocryptfs/internal/inomap 2.467s
