cpuset: Fix v2 effective_cpus/mems file names

The cpuset controller was using cgroup v1 file names for effective CPUs
and memory nodes on cgroup v2 systems. The file names changed between
versions:

v1: cpuset.effective_cpus, cpuset.effective_mems
v2: cpuset.cpus.effective, cpuset.mems.effective

This caused cpuset().effective_cpus to return empty on v2 systems since
the files don't exist. The controller already tracks the cgroup version
via the v2 flag, so use it to select the correct file names.

Fixes: #156

Signed-off-by: Jose Fernandez <[email protected]>

Author: jfernandez

src/fs/cpuset.rs

@@ -279,13 +279,23 @@ impl CpuSetController {
                     .unwrap_or_default()
             },
             effective_cpus: {
-                self.open_path("cpuset.effective_cpus", false)
+                let file = if self.v2 {
+                    "cpuset.cpus.effective"
+                } else {
+                    "cpuset.effective_cpus"
+                };
+                self.open_path(file, false)
                     .and_then(read_string_from)
                     .and_then(parse_range)
                     .unwrap_or_default()
             },
             effective_mems: {
-                self.open_path("cpuset.effective_mems", false)
+                let file = if self.v2 {
+                    "cpuset.mems.effective"
+                } else {
+                    "cpuset.effective_mems"
+                };
+                self.open_path(file, false)
                     .and_then(read_string_from)
                     .and_then(parse_range)
                     .unwrap_or_default()

tests/cpuset.rs

@@ -90,3 +90,33 @@ fn test_cpuset_set_cpus_add_task() {
 
     cg.delete().unwrap();
 }
+
+#[test]
+fn test_cpuset_effective_cpus() {
+    let h = cgroups_rs::fs::hierarchies::auto();
+    let cg = Cgroup::new(h, String::from("test_cpuset_effective_cpus")).unwrap();
+    {
+        let cpuset: &CpuSetController = cg.controller_of().unwrap();
+
+        // Set cpus to 0
+        let r = cpuset.set_cpus("0");
+        assert!(r.is_ok());
+
+        // Read back and verify effective_cpus is populated
+        let set = cpuset.cpuset();
+
+        if cg.v2() {
+            // On v2, effective_cpus should be populated after setting cpus
+            // This tests that we're reading the correct file: cpuset.cpus.effective
+            assert!(!set.effective_cpus.is_empty(),
+                "effective_cpus should not be empty on cgroup v2 after setting cpus");
+            assert_eq!((0, 0), set.effective_cpus[0]);
+        } else {
+            // On v1, effective_cpus should also work
+            // This tests that we're reading the correct file: cpuset.effective_cpus
+            assert!(!set.effective_cpus.is_empty(),
+                "effective_cpus should not be empty on cgroup v1");
+        }
+    }
+    cg.delete().unwrap();
+}