Node exporter complains about unknown metric lines from NFSd on Linux 6.6-rc1

Host operating system: output of uname -a

Linux 6.6.0-rc1 vanilla self compiled and running Debian otherwise

node_exporter version: output of node_exporter --version

$ ./node_exporter --version
node_exporter, version 1.6.1 (branch: master, revision: f34aaa61092fe7e3c6618fdb0b0d16a68a291ff7)
  build user:       klausman@felka
  build date:       20230911-15:50:34
  go version:       go1.21.1
  platform:         linux/amd64
  tags:             netgo osusergo static_build

node_exporter command line flags

./node_exporter --web.listen-address=:9101

node_exporter log output

ts=2023-09-11T15:53:30.969Z caller=collector.go:169 level=error msg="collector failed" name=nfsd duration_seconds=0.00018264 err="failed to retrieve nfsd stats: unknown NFSd metric line \"wdeleg_getattr\""

Are you running node_exporter in Docker?

Nope, running in host OS directly.

What did you do that produced an error?

Ran node-exporter as describe above

What did you expect to see?

No errors about unknown metric lines. Not sure if that metric line should actually become a useful exported metric.

What did you see instead?

The log message above

Start at the nfsd collector named in the error and reproduce the parser failure with Linux 6.6-rc1. Trace how the unknown "wdeleg_getattr" line is handled, then verify the collector no longer reports an unknown-metric error and that the resulting metric behavior matches the intended handling.