fn node_reachable(minor: u32) -> boolExpand description
The reachability test the whole filter turns on: a GPU id is kept only if its
/dev/nvidia{minor} node opens. Some runtimes create a node for every host GPU and enforce the
allocation in the device cgroup, so an unallocated node exists but open() fails with EPERM;
a presence test would count it as visible and leave the filter uninstalled.