Expose deletion error

So that users can retry or do some aftercare.

Fixes: #18

Signed-off-by: Tim Zhang <tim@hyper.sh>

src/cgroup.rs

@@ -9,8 +9,6 @@
 use crate::error::ErrorKind::*;
 use crate::error::*;
 
-use crate::libc_rmdir;
-
 use crate::{CgroupPid, ControllIdentifier, Controller, Hierarchy, Resources, Subsystem};
 
 use std::collections::HashMap;
@@ -148,17 +146,17 @@ impl<'b> Cgroup<'b> {
     /// system call will fail if there are any descendants. Thus, one should check whether it was
     /// actually removed, and remove the descendants first if not. In the future, this behavior
     /// will change.
-    pub fn delete(self) {
+    pub fn delete(&self) -> Result<()> {
         if self.v2() {
             if self.path != "" {
                 let mut p = self.hier.root().clone();
-                p.push(self.path);
-                libc_rmdir(p.to_str().unwrap());
+                p.push(self.path.clone());
+                return fs::remove_dir(p).map_err(|e| Error::with_cause(RemoveFailed, e));
             }
-            return;
+            return Ok(());
         }
 
-        self.subsystems.into_iter().for_each(|sub| match sub {
+        self.subsystems.iter().try_for_each(|sub| match sub {
             Subsystem::Pid(pidc) => pidc.delete(),
             Subsystem::Mem(c) => c.delete(),
             Subsystem::CpuSet(c) => c.delete(),
@@ -173,7 +171,7 @@ impl<'b> Cgroup<'b> {
             Subsystem::HugeTlb(c) => c.delete(),
             Subsystem::Rdma(c) => c.delete(),
             Subsystem::Systemd(c) => c.delete(),
-        });
+        })
     }
 
     /// Apply a set of resource limits to the control group.

src/error.rs

@@ -19,6 +19,9 @@ pub enum ErrorKind {
     /// An error occured while trying to read from a control group file.
     ReadFailed,
 
+    /// An error occured while trying to remove a control group.
+    RemoveFailed,
+
     /// An error occured while trying to parse a value from a control group file.
     ///
     /// In the future, there will be some information attached to this field.
@@ -55,6 +58,7 @@ impl fmt::Display for Error {
             ErrorKind::Common(s) => s.clone(),
             ErrorKind::WriteFailed => "unable to write to a control group file".to_string(),
             ErrorKind::ReadFailed => "unable to read a control group file".to_string(),
+            ErrorKind::RemoveFailed => "unable to remove a control group".to_string(),
             ErrorKind::ParseError => "unable to parse control group file".to_string(),
             ErrorKind::InvalidOperation => "the requested operation is invalid".to_string(),
             ErrorKind::InvalidPath => "the given path is invalid".to_string(),

src/lib.rs

@@ -7,7 +7,7 @@
 use log::*;
 
 use std::collections::HashMap;
-use std::fs::File;
+use std::fs::{self, File};
 use std::io::{BufRead, BufReader, Read, Write};
 use std::path::{Path, PathBuf};
 
@@ -246,7 +246,7 @@ pub trait Controller {
     fn exists(&self) -> bool;
 
     /// Delete the controller.
-    fn delete(&self);
+    fn delete(&self) -> Result<()>;
 
     /// Attach a task to this controller.
     fn add_task(&self, pid: &CgroupPid) -> Result<()>;
@@ -295,10 +295,12 @@ where
     }
 
     /// Delete the controller.
-    fn delete(&self) {
-        if self.get_path().exists() {
-            libc_rmdir(self.get_path().to_str().unwrap());
+    fn delete(&self) -> Result<()> {
+        if !self.get_path().exists() {
+            return Ok(());
         }
+
+        fs::remove_dir(self.get_path()).map_err(|e| Error::with_cause(ErrorKind::RemoveFailed, e))
     }
 
     /// Attach a task to this controller.
@@ -807,13 +809,6 @@ pub fn nested_keyed_to_hashmap(mut file: File) -> Result<HashMap<String, HashMap
     Ok(h)
 }
 
-/// fs::remove_dir_all or fs::remove_dir can't work with cgroup directory sometimes.
-/// with error: `Os { code: 1, kind: PermissionDenied, message: "Operation not permitted" }`
-pub fn libc_rmdir(p: &str) {
-    // with int return value
-    let _ = unsafe { libc::rmdir(p.as_ptr() as *const libc::c_char) };
-}
-
 /// read and parse an i64 data
 pub fn read_i64_from(mut file: File) -> Result<i64> {
     let mut string = String::new();