Fix clippy for rust 1.52

There are new lints are added in clippy for rust 1.52

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

src/cgroup.rs

@@ -311,9 +311,8 @@ impl Cgroup {
 
 pub const UNIFIED_MOUNTPOINT: &str = "/sys/fs/cgroup";
 
-fn enable_controllers(controllers: &[String], path: &PathBuf) {
-    let mut f = path.clone();
-    f.push("cgroup.subtree_control");
+fn enable_controllers(controllers: &[String], path: &Path) {
+    let f = path.join("cgroup.subtree_control");
     for c in controllers {
         let body = format!("+{}", c);
         let _rest = fs::write(f.as_path(), body.as_bytes());

src/cgroup_builder.rs

@@ -240,10 +240,10 @@ impl DeviceResourceBuilder {
         access: Vec<crate::devices::DevicePermissions>,
     ) -> DeviceResourceBuilder {
         self.cgroup.resources.devices.devices.push(DeviceResource {
+            allow,
+            devtype,
             major,
             minor,
-            devtype,
-            allow,
             access,
         });
         self

src/error.rs

@@ -76,6 +76,7 @@ impl fmt::Display for Error {
 
 impl StdError for Error {
     fn cause(&self) -> Option<&dyn StdError> {
+        #[allow(clippy::manual_map)]
         match self.cause {
             Some(ref x) => Some(&**x),
             None => None,

src/events.rs

@@ -8,7 +8,7 @@ use nix::sys::eventfd;
 use std::fs::{self, File};
 use std::io::Read;
 use std::os::unix::io::{AsRawFd, FromRawFd};
-use std::path::{Path, PathBuf};
+use std::path::Path;
 use std::sync::mpsc::{self, Receiver};
 use std::thread;
 
@@ -17,18 +17,18 @@ use crate::error::*;
 
 // notify_on_oom returns channel on which you can expect event about OOM,
 // if process died without OOM this channel will be closed.
-pub fn notify_on_oom_v2(key: &str, dir: &PathBuf) -> Result<Receiver<String>> {
+pub fn notify_on_oom_v2(key: &str, dir: &Path) -> Result<Receiver<String>> {
     register_memory_event(key, dir, "memory.oom_control", "")
 }
 
 // notify_on_oom returns channel on which you can expect event about OOM,
 // if process died without OOM this channel will be closed.
-pub fn notify_on_oom_v1(key: &str, dir: &PathBuf) -> Result<Receiver<String>> {
+pub fn notify_on_oom_v1(key: &str, dir: &Path) -> Result<Receiver<String>> {
     register_memory_event(key, dir, "memory.oom_control", "")
 }
 
 // level is one of "low", "medium", or "critical"
-pub fn notify_memory_pressure(key: &str, dir: &PathBuf, level: &str) -> Result<Receiver<String>> {
+pub fn notify_memory_pressure(key: &str, dir: &Path, level: &str) -> Result<Receiver<String>> {
     if level != "low" && level != "medium" && level != "critical" {
         return Err(Error::from_string(format!(
             "invalid pressure level {}",
@@ -41,7 +41,7 @@ pub fn notify_memory_pressure(key: &str, dir: &PathBuf, level: &str) -> Result<R
 
 fn register_memory_event(
     key: &str,
-    cg_dir: &PathBuf,
+    cg_dir: &Path,
     event_name: &str,
     arg: &str,
 ) -> Result<Receiver<String>> {

src/lib.rs

@@ -365,12 +365,10 @@ where
             .map(|file| {
                 let bf = BufReader::new(file);
                 let mut v = Vec::new();
-                for line in bf.lines() {
-                    if let Ok(line) = line {
+                for line in bf.lines().flatten() {
                     let n = line.trim().parse().unwrap_or(0u64);
                     v.push(n);
                 }
-                }
                 v.into_iter().map(CgroupPid::from).collect()
             })
             .unwrap_or_default()
@@ -383,7 +381,7 @@ where
 
 // remove_dir aims to remove cgroup path. It does so recursively,
 // by removing any subdirectories (sub-cgroups) first.
-fn remove_dir(dir: &PathBuf) -> Result<()> {
+fn remove_dir(dir: &Path) -> Result<()> {
     // try the fast path first.
     if fs::remove_dir(dir).is_ok() {
         return Ok(());