Merge pull request #146 from fidencio/topic/release-v0.3.5

release: v0.3.5

Cargo.toml

@@ -5,7 +5,7 @@ repository = "https://github.com/kata-containers/cgroups-rs"
 keywords = ["linux", "cgroup", "containers", "isolation"]
 categories = ["os", "api-bindings", "os::unix-apis"]
 license = "MIT OR Apache-2.0"
-version = "0.3.4"
+version = "0.3.5"
 authors = ["The Kata Containers community <kata-dev@lists.katacontainers.io>", "Levente Kurusa <lkurusa@acm.org>", "Sam Wilson <tecywiz121@hotmail.com>"]
 edition = "2018"
 homepage = "https://github.com/kata-containers/cgroups-rs"

src/blkio.rs

@@ -430,10 +430,10 @@ impl<'a> From<&'a Subsystem> for &'a BlkIoController {
 
 impl BlkIoController {
     /// Constructs a new `BlkIoController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             v2,
         }
     }

src/cgroup.rs

@@ -9,6 +9,7 @@
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
+use crate::hierarchies::V1;
 use crate::{CgroupPid, ControllIdentifier, Controller, Hierarchy, Resources, Subsystem};
 
 use std::collections::HashMap;
@@ -521,7 +522,7 @@ fn supported_controllers() -> Vec<String> {
     let ret = fs::read_to_string(p.as_str());
     ret.unwrap_or_default()
         .split(' ')
-        .map(|x| x.to_string())
+        .map(|x| x.trim().to_string())
         .collect::<Vec<String>>()
 }
 
@@ -588,19 +589,47 @@ pub fn get_cgroups_relative_paths_by_pid(pid: u32) -> Result<HashMap<String, Str
     get_cgroups_relative_paths_by_path(path)
 }
 
+fn get_cgroup_destination(mut mount_root: String, pidpath: String) -> String {
+    if mount_root == "/" {
+        mount_root = String::from("");
+    }
+    pidpath.trim_start_matches(&mount_root).to_string()
+}
+
+pub fn existing_path(paths: HashMap<String, String>) -> Result<HashMap<String, String>> {
+    let mount_roots_v1 = V1::new();
+    let mut mount_roots_subsystems_map = HashMap::new();
+
+    for s in mount_roots_v1.subsystems().iter() {
+        let controller_name = s.controller_name();
+        let path_from_cgroup = paths
+            .get(&controller_name)
+            .ok_or(Error::new(Common(format!(
+                "controller {} found in mountinfo, but not found in cgroup.",
+                controller_name
+            ))))?;
+        let path_from_mountinfo = s.to_controller().base().to_string_lossy().to_string();
+
+        let des_path = get_cgroup_destination(path_from_mountinfo, path_from_cgroup.to_owned());
+        mount_roots_subsystems_map.insert(controller_name, des_path);
+    }
+    Ok(mount_roots_subsystems_map)
+}
+
 fn get_cgroups_relative_paths_by_path(path: String) -> Result<HashMap<String, String>> {
     let mut m = HashMap::new();
     let content =
         fs::read_to_string(path.clone()).map_err(|e| Error::with_cause(ReadFailed(path), e))?;
-    for l in content.lines() {
-        let fl: Vec<&str> = l.split(':').collect();
-        if fl.len() != 3 {
-            continue;
-        }
-
-        let keys: Vec<&str> = fl[1].split(',').collect();
-        for key in &keys {
-            m.insert(key.to_string(), fl[2].to_string());
+    // cgroup path may have ":" , likes
+    // "2:cpu,cpuacct:/system.slice/containerd.service/test.slice:cri-containerd:96b37a2edf84351487f42039e137427f1812f678850675fac214caf597ee5e4a"
+    for line in content.lines() {
+        if let Some((first_value_part, remaining_path)) =
+            line.split_once(':').unwrap_or_default().1.split_once(':')
+        {
+            let keys: Vec<&str> = first_value_part.split(',').collect();
+            keys.iter().for_each(|key| {
+                m.insert(key.to_string(), remaining_path.to_string());
+            });
         }
     }
     Ok(m)

src/cpu.rs

@@ -59,7 +59,6 @@ impl ControllerInternal for CpuController {
     fn get_path(&self) -> &PathBuf {
         &self.path
     }
-
     fn get_path_mut(&mut self) -> &mut PathBuf {
         &mut self.path
     }
@@ -113,10 +112,10 @@ impl<'a> From<&'a Subsystem> for &'a CpuController {
 
 impl CpuController {
     /// Contructs a new `CpuController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             v2,
         }
     }

src/cpuacct.rs

@@ -100,10 +100,10 @@ impl<'a> From<&'a Subsystem> for &'a CpuAcctController {
 
 impl CpuAcctController {
     /// Contructs a new `CpuAcctController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
         }
     }
 

src/cpuset.rs

@@ -254,10 +254,10 @@ fn parse_range(s: String) -> Result<Vec<(u64, u64)>> {
 
 impl CpuSetController {
     /// Contructs a new `CpuSetController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             v2,
         }
     }

src/devices.rs

@@ -204,10 +204,10 @@ impl<'a> From<&'a Subsystem> for &'a DevicesController {
 
 impl DevicesController {
     /// Constructs a new `DevicesController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
         }
     }
 
@@ -297,7 +297,7 @@ impl DevicesController {
             match res {
                 Ok(_) => {
                     s.lines().fold(Ok(Vec::new()), |acc, line| {
-                        let ls = line.to_string().split(|c| c == ' ' || c == ':').map(|x| x.to_string()).collect::<Vec<String>>();
+                        let ls = line.split(|c| c == ' ' || c == ':').map(|x| x.to_string()).collect::<Vec<String>>();
                         if acc.is_err() || ls.len() != 4 {
                             error!("allowed_devices: acc: {:?}, ls: {:?}", acc, ls);
                             Err(Error::new(ParseError))

src/freezer.rs

@@ -84,14 +84,13 @@ impl<'a> From<&'a Subsystem> for &'a FreezerController {
 
 impl FreezerController {
     /// Contructs a new `FreezerController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             v2,
         }
     }
-
     /// Freezes the processes in the control group.
     pub fn freeze(&self) -> Result<()> {
         let mut file_name = "freezer.state";

src/hierarchies.rs

@@ -5,9 +5,6 @@
 //
 
 //! This module represents the various control group hierarchies the Linux kernel supports.
-//!
-//! Currently, we only support the cgroupv1 hierarchy, but in the future we will add support for
-//! the Unified Hierarchy.
 
 use std::fs;
 use std::fs::File;
@@ -37,6 +34,8 @@ use crate::cgroup::Cgroup;
 /// See `proc(5)` for format details.
 #[derive(Debug, PartialEq, Eq, Hash, Clone)]
 pub struct Mountinfo {
+    /// Mount root directory of the file system.
+    pub mount_root: PathBuf,
     /// Mount pathname relative to the process's root.
     pub mount_point: PathBuf,
     /// Filesystem type (main type with optional sub-type).
@@ -57,6 +56,7 @@ pub(crate) fn parse_mountinfo_for_line(line: &str) -> Option<Mountinfo> {
         return None;
     }
     let mount_point = PathBuf::from(s0_values[4]);
+    let mount_root = PathBuf::from(s0_values[3]);
     let fs_type_values: Vec<_> = s1_values[0].trim().split('.').collect();
     let fs_type = match fs_type_values.len() {
         1 => (fs_type_values[0].to_string(), None),
@@ -69,6 +69,7 @@ pub(crate) fn parse_mountinfo_for_line(line: &str) -> Option<Mountinfo> {
 
     let super_opts: Vec<String> = s1_values[2].trim().split(',').map(String::from).collect();
     Some(Mountinfo {
+        mount_root,
         mount_point,
         fs_type,
         super_opts,
@@ -123,47 +124,53 @@ impl Hierarchy for V1 {
         // The cgroup writeback feature requires cooperation between memcgs and blkcgs
         // To avoid exceptions, we should add_task for blkcg before memcg(push BlkIo before Mem)
         // For more Information: https://www.alibabacloud.com/help/doc-detail/155509.htm
-        if let Some(root) = self.get_mount_point(Controllers::BlkIo) {
-            subs.push(Subsystem::BlkIo(BlkIoController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::BlkIo) {
+            subs.push(Subsystem::BlkIo(BlkIoController::new(point, root, false)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Mem) {
-            subs.push(Subsystem::Mem(MemController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Mem) {
+            subs.push(Subsystem::Mem(MemController::new(point, root, false)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Pids) {
-            subs.push(Subsystem::Pid(PidController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Pids) {
+            subs.push(Subsystem::Pid(PidController::new(point, root, false)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::CpuSet) {
-            subs.push(Subsystem::CpuSet(CpuSetController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::CpuSet) {
+            subs.push(Subsystem::CpuSet(CpuSetController::new(point, root, false)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::CpuAcct) {
-            subs.push(Subsystem::CpuAcct(CpuAcctController::new(root)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::CpuAcct) {
+            subs.push(Subsystem::CpuAcct(CpuAcctController::new(point, root)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Cpu) {
-            subs.push(Subsystem::Cpu(CpuController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Cpu) {
+            subs.push(Subsystem::Cpu(CpuController::new(point, root, false)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Devices) {
-            subs.push(Subsystem::Devices(DevicesController::new(root)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Devices) {
+            subs.push(Subsystem::Devices(DevicesController::new(point, root)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Freezer) {
-            subs.push(Subsystem::Freezer(FreezerController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Freezer) {
+            subs.push(Subsystem::Freezer(FreezerController::new(
+                point, root, false,
+            )));
         }
-        if let Some(root) = self.get_mount_point(Controllers::NetCls) {
-            subs.push(Subsystem::NetCls(NetClsController::new(root)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::NetCls) {
+            subs.push(Subsystem::NetCls(NetClsController::new(point, root)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::PerfEvent) {
-            subs.push(Subsystem::PerfEvent(PerfEventController::new(root)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::PerfEvent) {
+            subs.push(Subsystem::PerfEvent(PerfEventController::new(point, root)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::NetPrio) {
-            subs.push(Subsystem::NetPrio(NetPrioController::new(root)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::NetPrio) {
+            subs.push(Subsystem::NetPrio(NetPrioController::new(point, root)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::HugeTlb) {
-            subs.push(Subsystem::HugeTlb(HugeTlbController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::HugeTlb) {
+            subs.push(Subsystem::HugeTlb(HugeTlbController::new(
+                point, root, false,
+            )));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Rdma) {
-            subs.push(Subsystem::Rdma(RdmaController::new(root)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Rdma) {
+            subs.push(Subsystem::Rdma(RdmaController::new(point, root)));
         }
-        if let Some(root) = self.get_mount_point(Controllers::Systemd) {
-            subs.push(Subsystem::Systemd(SystemdController::new(root, false)));
+        if let Some((point, root)) = self.get_mount_point(Controllers::Systemd) {
+            subs.push(Subsystem::Systemd(SystemdController::new(
+                point, root, false,
+            )));
         }
 
         subs
@@ -218,29 +225,51 @@ impl Hierarchy for V2 {
         for s in controller_list {
             match s {
                 "cpu" => {
-                    subs.push(Subsystem::Cpu(CpuController::new(self.root(), true)));
+                    subs.push(Subsystem::Cpu(CpuController::new(
+                        self.root(),
+                        PathBuf::from(""),
+                        true,
+                    )));
                 }
                 "io" => {
-                    subs.push(Subsystem::BlkIo(BlkIoController::new(self.root(), true)));
+                    subs.push(Subsystem::BlkIo(BlkIoController::new(
+                        self.root(),
+                        PathBuf::from(""),
+                        true,
+                    )));
                 }
                 "cpuset" => {
-                    subs.push(Subsystem::CpuSet(CpuSetController::new(self.root(), true)));
+                    subs.push(Subsystem::CpuSet(CpuSetController::new(
+                        self.root(),
+                        PathBuf::from(""),
+                        true,
+                    )));
                 }
                 "memory" => {
-                    subs.push(Subsystem::Mem(MemController::new(self.root(), true)));
+                    subs.push(Subsystem::Mem(MemController::new(
+                        self.root(),
+                        PathBuf::from(""),
+                        true,
+                    )));
                 }
                 "pids" => {
-                    subs.push(Subsystem::Pid(PidController::new(self.root(), true)));
+                    subs.push(Subsystem::Pid(PidController::new(
+                        self.root(),
+                        PathBuf::from(""),
+                        true,
+                    )));
                 }
                 "freezer" => {
                     subs.push(Subsystem::Freezer(FreezerController::new(
                         self.root(),
+                        PathBuf::from(""),
                         true,
                     )));
                 }
                 "hugetlb" => {
                     subs.push(Subsystem::HugeTlb(HugeTlbController::new(
                         self.root(),
+                        PathBuf::from(""),
                         true,
                     )));
                 }
@@ -275,10 +304,10 @@ impl V1 {
         }
     }
 
-    pub fn get_mount_point(&self, controller: Controllers) -> Option<PathBuf> {
+    pub fn get_mount_point(&self, controller: Controllers) -> Option<(PathBuf, PathBuf)> {
         self.mountinfo.iter().find_map(|m| {
             if m.fs_type.0 == "cgroup" && m.super_opts.contains(&controller.to_string()) {
-                return Some(m.mount_point.clone());
+                return Some((m.mount_point.to_owned(), m.mount_root.to_owned()));
             }
             None
         })
@@ -337,19 +366,19 @@ mod tests {
     fn test_parse_mount() {
         let mountinfo = vec![
             ("29 26 0:26 / /sys/fs/cgroup/cpuset,cpu,cpuacct rw,nosuid,nodev,noexec,relatime shared:10 - cgroup cgroup rw,cpuset,cpu,cpuacct",
-             Mountinfo{mount_point: PathBuf::from("/sys/fs/cgroup/cpuset,cpu,cpuacct"), fs_type: ("cgroup".to_string(), None), super_opts: vec![
+             Mountinfo{mount_root: PathBuf::from("/"), mount_point: PathBuf::from("/sys/fs/cgroup/cpuset,cpu,cpuacct"), fs_type: ("cgroup".to_string(), None), super_opts: vec![
                 "rw".to_string(),
                 "cpuset".to_string(),
                 "cpu".to_string(),
                 "cpuacct".to_string(),
              ]}),
             ("121 1731 0:42 / /shm rw,nosuid,nodev,noexec,relatime shared:68 master:66 - tmpfs shm rw,size=65536k",
-             Mountinfo{mount_point: PathBuf::from("/shm"), fs_type: ("tmpfs".to_string(), None), super_opts: vec![
+             Mountinfo{mount_root: PathBuf::from("/"), mount_point: PathBuf::from("/shm"), fs_type: ("tmpfs".to_string(), None), super_opts: vec![
                 "rw".to_string(),
                 "size=65536k".to_string(),
              ]}),
             ("121 1731 0:42 / /shm rw,nosuid,nodev,noexec,relatime shared:68 master:66 - tmpfs.123 shm rw,size=65536k",
-             Mountinfo{mount_point: PathBuf::from("/shm"), fs_type: ("tmpfs".to_string(), Some("123".to_string())), super_opts: vec![
+             Mountinfo{mount_root: PathBuf::from("/"), mount_point: PathBuf::from("/shm"), fs_type: ("tmpfs".to_string(), Some("123".to_string())), super_opts: vec![
                 "rw".to_string(),
                 "size=65536k".to_string(),
              ]}),

src/hugetlb.rs

@@ -88,11 +88,11 @@ impl<'a> From<&'a Subsystem> for &'a HugeTlbController {
 
 impl HugeTlbController {
     /// Constructs a new `HugeTlbController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         let sizes = get_hugepage_sizes();
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             sizes,
             v2,
         }

src/lib.rs

@@ -231,6 +231,7 @@ mod sealed {
             })
         }
 
+        #[allow(dead_code)]
         fn get(&self, key: &str) -> Result<String> {
             self.open_path(key, false).and_then(|mut file: File| {
                 let mut string = String::new();
@@ -255,6 +256,9 @@ pub trait Controller {
     /// The file system path to the controller.
     fn path(&self) -> &Path;
 
+    /// Root path of the file system to the controller.
+    fn base(&self) -> &Path;
+
     /// Apply a set of resources to the Controller, invoking its internal functions to pass the
     /// kernel the information.
     fn apply(&self, res: &Resources) -> Result<()>;
@@ -307,6 +311,10 @@ where
         self.get_path()
     }
 
+    fn base(&self) -> &Path {
+        self.get_base()
+    }
+
     /// Apply a set of resources to the Controller, invoking its internal functions to pass the
     /// kernel the information.
     fn apply(&self, res: &Resources) -> Result<()> {

src/memory.rs

@@ -540,10 +540,10 @@ impl ControllerInternal for MemController {
 
 impl MemController {
     /// Contructs a new `MemController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             v2,
         }
     }
@@ -573,18 +573,33 @@ impl MemController {
 
     // for v2
     pub fn get_mem(&self) -> Result<SetMemory> {
-        let mut m: SetMemory = Default::default();
-        self.get_max_value("memory.high")
-            .map(|x| m.high = Some(x))?;
-        self.get_max_value("memory.low").map(|x| m.low = Some(x))?;
-        self.get_max_value("memory.max").map(|x| m.max = Some(x))?;
-        self.get_max_value("memory.min").map(|x| m.min = Some(x))?;
+        let m = SetMemory {
+            high: self
+                .get_max_value("memory.high")
+                .map_or(Some(MaxValue::default()), Some),
+            low: self
+                .get_max_value("memory.low")
+                .map_or(Some(MaxValue::Value(0)), Some),
+            max: self
+                .get_max_value("memory.max")
+                .map_or(Some(MaxValue::default()), Some),
+            min: self
+                .get_max_value("memory.min")
+                .map_or(Some(MaxValue::Value(0)), Some),
+        };
 
         Ok(m)
     }
 
     fn memory_stat_v2(&self) -> Memory {
-        let set = self.get_mem().unwrap();
+        // NOTE: get_mem() always returns T, but let's
+        // still do `unwrap_or` for safety.
+        let set = self.get_mem().unwrap_or(SetMemory {
+            low: Some(MaxValue::Value(0)),
+            high: Some(MaxValue::default()),
+            max: Some(MaxValue::default()),
+            min: Some(MaxValue::Value(0)),
+        });
 
         Memory {
             fail_cnt: 0,
@@ -730,7 +745,7 @@ impl MemController {
                 .open_path("memory.swap.events", false)
                 .and_then(flat_keyed_to_hashmap)
                 .map(|x| *x.get("fail").unwrap_or(&0) as u64)
-                .unwrap(),
+                .unwrap_or(0),
             limit_in_bytes: self
                 .open_path("memory.swap.max", false)
                 .and_then(read_i64_from)

src/net_cls.rs

@@ -76,10 +76,10 @@ impl<'a> From<&'a Subsystem> for &'a NetClsController {
 
 impl NetClsController {
     /// Constructs a new `NetClsController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
         }
     }
 

src/net_prio.rs

@@ -79,10 +79,10 @@ impl<'a> From<&'a Subsystem> for &'a NetPrioController {
 
 impl NetPrioController {
     /// Constructs a new `NetPrioController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
         }
     }
 

src/perf_event.rs

@@ -65,10 +65,10 @@ impl<'a> From<&'a Subsystem> for &'a PerfEventController {
 
 impl PerfEventController {
     /// Constructs a new `PerfEventController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
         }
     }
 }

src/pid.rs

@@ -92,10 +92,10 @@ impl<'a> From<&'a Subsystem> for &'a PidController {
 impl PidController {
     /// Constructors a new `PidController` instance, with `root` serving as the controller's root
     /// directory.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             v2,
         }
     }

src/rdma.rs

@@ -68,10 +68,10 @@ impl<'a> From<&'a Subsystem> for &'a RdmaController {
 
 impl RdmaController {
     /// Constructs a new `RdmaController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
         }
     }
 
@@ -81,6 +81,11 @@ impl RdmaController {
             .and_then(read_string_from)
     }
 
+    /// Returns the max usage of RDMA/IB specific resources.
+    pub fn max(&self) -> Result<String> {
+        self.open_path("rdma.max", false).and_then(read_string_from)
+    }
+
     /// Set a maximum usage for each RDMA/IB resource.
     pub fn set_max(&self, max: &str) -> Result<()> {
         self.open_path("rdma.max", true).and_then(|mut file| {

src/systemd.rs

@@ -62,10 +62,10 @@ impl<'a> From<&'a Subsystem> for &'a SystemdController {
 
 impl SystemdController {
     /// Constructs a new `SystemdController` with `root` serving as the root of the control group.
-    pub fn new(root: PathBuf, v2: bool) -> Self {
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
         Self {
-            base: root.clone(),
-            path: root,
+            base: root,
+            path: point,
             _v2: v2,
         }
     }