cgroup: support to set threaded mode in cgroup v2

Support to set threaded mode in cgroup v2. The premise of switching to threaded mode is that only the cgroup of cpuset, cpu and pids is supported.

Fixes: #90

Signed-off-by: yaoyinnan <yaoyinnan@foxmail.com>

src/lib.rs

@@ -280,9 +280,18 @@ pub trait Controller {
     /// Attach a task to this controller.
     fn add_task_by_tgid(&self, pid: &CgroupPid) -> Result<()>;
 
+    /// set cgroup type.
+    fn set_cgroup_type(&self, cgroup_type: &str) -> Result<()>;
+
+    /// get cgroup type.
+    fn get_cgroup_type(&self) -> Result<String>;
+
     /// Get the list of tasks that this controller has.
     fn tasks(&self) -> Vec<CgroupPid>;
 
+    /// Get the list of procs that this controller has.
+    fn procs(&self) -> Vec<CgroupPid>;
+
     fn v2(&self) -> bool;
 }
 
@@ -317,6 +326,9 @@ where
 
     /// Set notify_on_release
     fn set_notify_on_release(&self, enable: bool) -> Result<()> {
+        if self.is_v2() {
+            return Err(Error::new(ErrorKind::CgroupVersion));
+        }
         self.open_path("notify_on_release", true)
             .and_then(|mut file| {
                 write!(file, "{}", enable as i32).map_err(|e| {
@@ -330,6 +342,9 @@ where
 
     /// Set release_agent
     fn set_release_agent(&self, path: &str) -> Result<()> {
+        if self.is_v2() {
+            return Err(Error::new(ErrorKind::CgroupVersion));
+        }
         self.open_path("release_agent", true).and_then(|mut file| {
             file.write_all(path.as_bytes()).map_err(|e| {
                 Error::with_cause(
@@ -373,7 +388,7 @@ where
     fn add_task(&self, pid: &CgroupPid) -> Result<()> {
         let mut file_name = "tasks";
         if self.is_v2() {
-            file_name = "cgroup.procs";
+            file_name = "cgroup.threads";
         }
         self.open_path(file_name, true).and_then(|mut file| {
             file.write_all(pid.pid.to_string().as_ref()).map_err(|e| {
@@ -387,23 +402,21 @@ where
 
     /// Attach a task to this controller by thread group id.
     fn add_task_by_tgid(&self, pid: &CgroupPid) -> Result<()> {
-        self.open_path("cgroup.procs", true).and_then(|mut file| {
+        let file_name = "cgroup.procs";
+        self.open_path(file_name, true).and_then(|mut file| {
             file.write_all(pid.pid.to_string().as_ref()).map_err(|e| {
                 Error::with_cause(
-                    ErrorKind::WriteFailed("cgroup.procs".to_string(), pid.pid.to_string()),
+                    ErrorKind::WriteFailed(file_name.to_string(), pid.pid.to_string()),
                     e,
                 )
             })
         })
     }
 
-    /// Get the list of tasks that this controller has.
-    fn tasks(&self) -> Vec<CgroupPid> {
-        let mut file = "tasks";
-        if self.is_v2() {
-            file = "cgroup.procs";
-        }
-        self.open_path(file, false)
+    /// Get the list of procs that this controller has.
+    fn procs(&self) -> Vec<CgroupPid> {
+        let file_name = "cgroup.procs";
+        self.open_path(file_name, false)
             .map(|file| {
                 let bf = BufReader::new(file);
                 let mut v = Vec::new();
@@ -421,6 +434,64 @@ where
             .unwrap_or_default()
     }
 
+    /// Get the list of tasks that this controller has.
+    fn tasks(&self) -> Vec<CgroupPid> {
+        let mut file_name = "tasks";
+        if self.is_v2() {
+            file_name = "cgroup.threads";
+        }
+        self.open_path(file_name, false)
+            .map(|file| {
+                let bf = BufReader::new(file);
+                let mut v = Vec::new();
+                for line in bf.lines() {
+                    match line {
+                        Ok(line) => {
+                            let n = line.trim().parse().unwrap_or(0u64);
+                            v.push(n);
+                        }
+                        Err(_) => break,
+                    }
+                }
+                v.into_iter().map(CgroupPid::from).collect()
+            })
+            .unwrap_or_default()
+    }
+
+    /// set cgroup.type
+    fn set_cgroup_type(&self, cgroup_type: &str) -> Result<()> {
+        if !self.is_v2() {
+            return Err(Error::new(ErrorKind::CgroupVersion));
+        }
+        let file_name = "cgroup.type";
+        self.open_path(file_name, true).and_then(|mut file| {
+            file.write_all(cgroup_type.as_bytes()).map_err(|e| {
+                Error::with_cause(
+                    ErrorKind::WriteFailed(file_name.to_string(), cgroup_type.to_string()),
+                    e,
+                )
+            })
+        })
+    }
+
+    /// get cgroup.type
+    fn get_cgroup_type(&self) -> Result<String> {
+        if !self.is_v2() {
+            return Err(Error::new(ErrorKind::CgroupVersion));
+        }
+        let file_name = "cgroup.type";
+        self.open_path(file_name, false).and_then(|mut file: File| {
+            let mut string = String::new();
+            match file.read_to_string(&mut string) {
+                Ok(_) => Ok(string.trim().to_owned()),
+                Err(e) => Err(Error::with_cause(
+                    ErrorKind::ReadFailed(file_name.to_string()),
+                    e,
+                )),
+            }
+        })
+    }
+
     fn v2(&self) -> bool {
         self.is_v2()
     }
@@ -468,6 +539,9 @@ pub trait Hierarchy: std::fmt::Debug + Send + Sync {
     /// Return a handle to the root control group in the hierarchy.
     fn root_control_group(&self) -> Cgroup;
 
+    /// Return a handle to the parent control group in the hierarchy.
+    fn parent_control_group(&self, path: &str) -> Cgroup;
+
     fn v2(&self) -> bool;
 }