add cgroup v2 pids controller

src/cgroups/v2/pids.rs

@@ -1,12 +1,71 @@
+use std::path::Path;
+
 use anyhow::Result;
 
+use crate::cgroups::common;
+
 use super::controller::Controller;
-use oci_spec::LinuxResources;
+use oci_spec::{LinuxPids, LinuxResources};
 
 pub struct Pids {}
 
 impl Controller for Pids {
-    fn apply(_: &LinuxResources, _: &std::path::Path) -> Result<()> {
+    fn apply(linux_resource: &LinuxResources, cgroup_root: &std::path::Path) -> Result<()> {
+        log::debug!("Apply pids cgroup v2 config");
+        if let Some(pids) = &linux_resource.pids {
+            Self::apply(cgroup_root, pids)?;
+        }
         Ok(())
     }
 }
+
+impl Pids {
+    fn apply(root_path: &Path, pids: &LinuxPids) -> Result<()> {
+        let limit = if pids.limit > 0 {
+            pids.limit.to_string()
+        } else {
+            "max".to_string()
+        };
+        Ok(common::write_cgroup_file(
+            &root_path.join("pids.max"),
+            &limit,
+        )?)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::cgroups::test::set_fixture;
+    use crate::utils::create_temp_dir;
+    use oci_spec::LinuxPids;
+
+    #[test]
+    fn test_set_pids() {
+        let pids_file_name = "pids.max";
+        let tmp = create_temp_dir("v2_test_set_pids").expect("create temp directory for test");
+        set_fixture(&tmp, pids_file_name, "1000").expect("Set fixture for 1000 pids");
+
+        let pids = LinuxPids { limit: 1000 };
+
+        Pids::apply(&tmp, &pids).expect("apply pids");
+        let content =
+            std::fs::read_to_string(tmp.join(pids_file_name)).expect("Read pids contents");
+        assert_eq!(pids.limit.to_string(), content);
+    }
+
+    #[test]
+    fn test_set_pids_max() {
+        let pids_file_name = "pids.max";
+        let tmp = create_temp_dir("v2_test_set_pids_max").expect("create temp directory for test");
+        set_fixture(&tmp, pids_file_name, "0").expect("set fixture for 0 pids");
+
+        let pids = LinuxPids { limit: 0 };
+
+        Pids::apply(&tmp, &pids).expect("apply pids");
+
+        let content =
+            std::fs::read_to_string(tmp.join(pids_file_name)).expect("Read pids contents");
+        assert_eq!("max".to_string(), content);
+    }
+}