Support customized attributes for CpuController and MemController

Customized attributes are useful for customized kernels.

Usage:
	let resource = &mut cgroups::Resources::default();
	resource.cpu.attrs.insert("cpu.cfs_init_buffer_us", "10".to_string());
	// apply here

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

src/cpu.rs

@@ -18,8 +18,8 @@ use crate::error::*;
 use crate::{parse_max_value, read_i64_from};
 
 use crate::{
-    ControllIdentifier, ControllerInternal, Controllers, CpuResources, MaxValue, Resources,
-    Subsystem,
+    ControllIdentifier, ControllerInternal, Controllers, CpuResources, CustomizedAttribute,
+    MaxValue, Resources, Subsystem,
 };
 
 /// A controller that allows controlling the `cpu` subsystem of a Cgroup.
@@ -91,6 +91,10 @@ impl ControllerInternal for CpuController {
                 return Err(Error::new(ErrorKind::Other));
             }
 
+            res.attrs.iter().for_each(|(k, v)| {
+                let _ = self.set(k, v);
+            })
+
             // TODO: rt properties (CONFIG_RT_GROUP_SCHED) are not yet supported
         }
 
@@ -306,6 +310,8 @@ impl CpuController {
     }
 }
 
+impl CustomizedAttribute for CpuController {}
+
 fn parse_cfs_quota_and_period(mut file: File) -> Result<CFSQuotaAndPeriod> {
     let mut content = String::new();
     file.read_to_string(&mut content)

src/lib.rs

@@ -189,9 +189,22 @@ mod sealed {
             std::path::Path::new(p).exists()
         }
     }
+
+    pub trait CustomizedAttribute: ControllerInternal {
+        fn set(&self, key: &str, value: &str) -> Result<()> {
+            self.open_path(key, true).and_then(|mut file| {
+                file.write_all(value.as_ref())
+                    .map_err(|e| Error::with_cause(WriteFailed, e))
+            })
+        }
+
+        fn get(&self, key: &str) -> Result<String> {
+            self.open_path(key, false).and_then(read_str_from)
+        }
+    }
 }
 
-pub(crate) use crate::sealed::ControllerInternal;
+pub(crate) use crate::sealed::{ControllerInternal, CustomizedAttribute};
 
 /// A Controller is a subsystem attached to the control group.
 ///
@@ -363,6 +376,14 @@ pub struct MemoryResources {
     /// Note, however, that a value of zero does not mean the process is never swapped out. Use the
     /// traditional `mlock(2)` system call for that purpose.
     pub swappiness: u64,
+    /// Customized key-value attributes
+    ///
+    /// # Usage:
+    /// ```
+    /// let resource = &mut cgroups::Resources::default();
+    /// resource.memory.attrs.insert("memory.numa_balancing", "true".to_string());
+    /// // apply here
+    pub attrs: std::collections::HashMap<&'static str, String>,
 }
 
 /// Resources limits on the number of processes.
@@ -402,6 +423,14 @@ pub struct CpuResources {
     pub realtime_runtime: i64,
     /// This is currently a no-operation.
     pub realtime_period: u64,
+    /// Customized key-value attributes
+    /// # Usage:
+    /// ```
+    /// let resource = &mut cgroups::Resources::default();
+    /// resource.cpu.attrs.insert("cpu.cfs_init_buffer_us", "10".to_string());
+    /// // apply here
+    /// ```
+    pub attrs: std::collections::HashMap<&'static str, String>,
 }
 
 /// A device resource that can be allowed or denied access to.
@@ -791,3 +820,11 @@ pub fn read_i64_from(mut file: File) -> Result<i64> {
         Err(e) => Err(Error::with_cause(ReadFailed, e)),
     }
 }
+
+pub fn read_str_from(mut file: File) -> Result<String> {
+    let mut string = String::new();
+    match file.read_to_string(&mut string) {
+        Ok(_) => Ok(string.trim().to_owned()),
+        Err(e) => Err(Error::with_cause(ReadFailed, e)),
+    }
+}

src/memory.rs

@@ -21,8 +21,8 @@ use crate::events;
 use crate::flat_keyed_to_hashmap;
 
 use crate::{
-    ControllIdentifier, ControllerInternal, Controllers, MaxValue, MemoryResources, Resources,
-    Subsystem,
+    ControllIdentifier, ControllerInternal, Controllers, CustomizedAttribute, MaxValue,
+    MemoryResources, Resources, Subsystem,
 };
 
 /// A controller that allows controlling the `memory` subsystem of a Cgroup.
@@ -834,6 +834,8 @@ impl ControllIdentifier for MemController {
     }
 }
 
+impl CustomizedAttribute for MemController {}
+
 impl<'a> From<&'a Subsystem> for &'a MemController {
     fn from(sub: &'a Subsystem) -> &'a MemController {
         unsafe {