manager: Introduce FsManager

`Manager` is a trait to unify the interface of cgroups. It is designed for
OCI containers. Its `set()` takes Linux resources of the OCI spec to set
cgroups.

The `FsManager`, the concrete implementation of `Manager`, manipulates
cgroups through cgroupfs, and supports both cgroups v1 and v2.

Signed-off-by: Xuewei Niu <niuxuewei.nxw@antgroup.com>

src/fs/freezer.rs

@@ -13,8 +13,8 @@ use std::path::PathBuf;
 
 use crate::fs::error::ErrorKind::*;
 use crate::fs::error::*;
-
 use crate::fs::{ControllIdentifier, ControllerInternal, Controllers, Resources, Subsystem};
+use crate::FreezerState;
 
 /// A controller that allows controlling the `freezer` subsystem of a Cgroup.
 ///
@@ -31,17 +31,6 @@ pub struct FreezerController {
     v2: bool,
 }
 
-/// The current state of the control group
-#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
-pub enum FreezerState {
-    /// The processes in the control group are _not_ frozen.
-    Thawed,
-    /// The processes in the control group are in the processes of being frozen.
-    Freezing,
-    /// The processes in the control group are frozen.
-    Frozen,
-}
-
 impl ControllerInternal for FreezerController {
     fn control_type(&self) -> Controllers {
         Controllers::Freezer

src/fs/mod.rs

@@ -245,6 +245,7 @@ mod sealed {
 }
 
 pub(crate) use crate::fs::sealed::{ControllerInternal, CustomizedAttribute};
+use crate::CgroupPid;
 
 /// A Controller is a subsystem attached to the control group.
 ///
@@ -771,26 +772,6 @@ pub struct Resources {
     pub blkio: BlkIoResources,
 }
 
-/// A structure representing a `pid`. Currently implementations exist for `u64` and
-/// `std::process::Child`.
-#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
-pub struct CgroupPid {
-    /// The process identifier
-    pub pid: u64,
-}
-
-impl From<u64> for CgroupPid {
-    fn from(u: u64) -> CgroupPid {
-        CgroupPid { pid: u }
-    }
-}
-
-impl From<&std::process::Child> for CgroupPid {
-    fn from(u: &std::process::Child) -> CgroupPid {
-        CgroupPid { pid: u.id() as u64 }
-    }
-}
-
 impl Subsystem {
     fn enter(self, path: &Path) -> Self {
         match self {