fs: Move all files to fs subdirectory

Prepare to implement FsManager, which should be done in the following-up
commits. Apart from that, no code is not modified.

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

src/fs/cpu.rs

@@ -0,0 +1,320 @@
+// Copyright (c) 2018 Levente Kurusa
+// Copyright (c) 2020 Ant Group
+//
+// SPDX-License-Identifier: Apache-2.0 or MIT
+//
+
+//! This module contains the implementation of the `cpu` cgroup subsystem.
+//!
+//! See the Kernel's documentation for more information about this subsystem, found at:
+//!  [Documentation/scheduler/sched-design-CFS.txt](https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt)
+//!  paragraph 7 ("GROUP SCHEDULER EXTENSIONS TO CFS").
+use std::fs::File;
+use std::io::{Read, Write};
+use std::path::PathBuf;
+
+use crate::fs::error::ErrorKind::*;
+use crate::fs::error::*;
+use crate::fs::{parse_max_value, read_i64_from, read_u64_from};
+
+use crate::fs::{
+    ControllIdentifier, ControllerInternal, Controllers, CpuResources, CustomizedAttribute,
+    MaxValue, Resources, Subsystem,
+};
+
+/// A controller that allows controlling the `cpu` subsystem of a Cgroup.
+///
+/// In essence, it allows gathering information about how much the tasks inside the control group
+/// are using the CPU and creating rules that limit their usage. Note that this crate does not yet
+/// support managing realtime tasks.
+#[derive(Debug, Clone)]
+pub struct CpuController {
+    base: PathBuf,
+    path: PathBuf,
+    v2: bool,
+}
+
+/// The current state of the control group and its processes.
+#[derive(Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub struct Cpu {
+    /// Reports CPU time statistics.
+    ///
+    /// Corresponds the `cpu.stat` file in `cpu` control group.
+    pub stat: String,
+}
+
+/// The current state of the control group and its processes.
+#[derive(Debug)]
+struct CfsQuotaAndPeriod {
+    quota: MaxValue,
+    period: u64,
+}
+
+impl ControllerInternal for CpuController {
+    fn control_type(&self) -> Controllers {
+        Controllers::Cpu
+    }
+
+    fn get_path(&self) -> &PathBuf {
+        &self.path
+    }
+    fn get_path_mut(&mut self) -> &mut PathBuf {
+        &mut self.path
+    }
+
+    fn get_base(&self) -> &PathBuf {
+        &self.base
+    }
+
+    fn is_v2(&self) -> bool {
+        self.v2
+    }
+
+    fn apply(&self, res: &Resources) -> Result<()> {
+        // get the resources that apply to this controller
+        let res: &CpuResources = &res.cpu;
+
+        update_and_test!(self, set_shares, res.shares, shares);
+        update_and_test!(self, set_cfs_period, res.period, cfs_period);
+        update_and_test!(self, set_cfs_quota, res.quota, cfs_quota);
+
+        res.attrs.iter().for_each(|(k, v)| {
+            let _ = self.set(k, v);
+        });
+
+        // TODO: rt properties (CONFIG_RT_GROUP_SCHED) are not yet supported
+
+        Ok(())
+    }
+}
+
+impl ControllIdentifier for CpuController {
+    fn controller_type() -> Controllers {
+        Controllers::Cpu
+    }
+}
+
+impl<'a> From<&'a Subsystem> for &'a CpuController {
+    fn from(sub: &'a Subsystem) -> &'a CpuController {
+        unsafe {
+            match sub {
+                Subsystem::Cpu(c) => c,
+                _ => {
+                    assert_eq!(1, 0);
+                    let v = std::mem::MaybeUninit::uninit();
+                    v.assume_init()
+                }
+            }
+        }
+    }
+}
+
+impl CpuController {
+    /// Contructs a new `CpuController` with `root` serving as the root of the control group.
+    pub fn new(point: PathBuf, root: PathBuf, v2: bool) -> Self {
+        Self {
+            base: root,
+            path: point,
+            v2,
+        }
+    }
+
+    /// Returns CPU time statistics based on the processes in the control group.
+    pub fn cpu(&self) -> Cpu {
+        Cpu {
+            stat: self
+                .open_path("cpu.stat", false)
+                .and_then(|mut file| {
+                    let mut s = String::new();
+                    let res = file.read_to_string(&mut s);
+                    match res {
+                        Ok(_) => Ok(s),
+                        Err(e) => Err(Error::with_cause(ReadFailed("cpu.stat".to_string()), e)),
+                    }
+                })
+                .unwrap_or_default(),
+        }
+    }
+
+    /// Configures the CPU bandwidth (in relative relation to other control groups and this control
+    /// group's parent).
+    ///
+    /// For example, setting control group `A`'s `shares` to `100`, and control group `B`'s
+    /// `shares` to `200` ensures that control group `B` receives twice as much as CPU bandwidth.
+    /// (Assuming both `A` and `B` are of the same parent)
+    pub fn set_shares(&self, shares: u64) -> Result<()> {
+        let mut file_name = "cpu.shares";
+        if self.v2 {
+            file_name = "cpu.weight";
+        }
+        // NOTE: .CpuShares is not used here. Conversion is the caller's responsibility.
+        self.open_path(file_name, true).and_then(|mut file| {
+            file.write_all(shares.to_string().as_ref()).map_err(|e| {
+                Error::with_cause(WriteFailed(file_name.to_string(), shares.to_string()), e)
+            })
+        })
+    }
+
+    /// Retrieve the CPU bandwidth that this control group (relative to other control groups and
+    /// this control group's parent) can use.
+    pub fn shares(&self) -> Result<u64> {
+        let mut file = "cpu.shares";
+        if self.v2 {
+            file = "cpu.weight";
+        }
+        self.open_path(file, false).and_then(read_u64_from)
+    }
+
+    /// Specify a period (when using the CFS scheduler) of time in microseconds for how often this
+    /// control group's access to the CPU should be reallocated.
+    pub fn set_cfs_period(&self, us: u64) -> Result<()> {
+        if self.v2 {
+            return self.set_cfs_quota_and_period(None, Some(us));
+        }
+        self.open_path("cpu.cfs_period_us", true)
+            .and_then(|mut file| {
+                file.write_all(us.to_string().as_ref()).map_err(|e| {
+                    Error::with_cause(
+                        WriteFailed("cpu.cfs_period_us".to_string(), us.to_string()),
+                        e,
+                    )
+                })
+            })
+    }
+
+    /// Retrieve the period of time of how often this cgroup's access to the CPU should be
+    /// reallocated in microseconds.
+    pub fn cfs_period(&self) -> Result<u64> {
+        if self.v2 {
+            let current_value = self
+                .open_path("cpu.max", false)
+                .and_then(parse_cfs_quota_and_period)?;
+            return Ok(current_value.period);
+        }
+        self.open_path("cpu.cfs_period_us", false)
+            .and_then(read_u64_from)
+    }
+
+    /// Specify a quota (when using the CFS scheduler) of time in microseconds for which all tasks
+    /// in this control group can run during one period (see: `set_cfs_period()`).
+    pub fn set_cfs_quota(&self, us: i64) -> Result<()> {
+        if self.v2 {
+            return self.set_cfs_quota_and_period(Some(us), None);
+        }
+        self.open_path("cpu.cfs_quota_us", true)
+            .and_then(|mut file| {
+                file.write_all(us.to_string().as_ref()).map_err(|e| {
+                    Error::with_cause(
+                        WriteFailed("cpu.cfs_quota_us".to_string(), us.to_string()),
+                        e,
+                    )
+                })
+            })
+    }
+
+    /// Retrieve the quota of time for which all tasks in this cgroup can run during one period, in
+    /// microseconds.
+    pub fn cfs_quota(&self) -> Result<i64> {
+        if self.v2 {
+            let current_value = self
+                .open_path("cpu.max", false)
+                .and_then(parse_cfs_quota_and_period)?;
+            return Ok(current_value.quota.to_i64());
+        }
+
+        self.open_path("cpu.cfs_quota_us", false)
+            .and_then(read_i64_from)
+    }
+
+    pub fn set_cfs_quota_and_period(&self, quota: Option<i64>, period: Option<u64>) -> Result<()> {
+        if !self.v2 {
+            if let Some(q) = quota {
+                self.set_cfs_quota(q)?;
+            }
+            if let Some(p) = period {
+                self.set_cfs_period(p)?;
+            }
+            return Ok(());
+        }
+
+        // https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html
+
+        // cpu.max
+        // A read-write two value file which exists on non-root cgroups. The default is “max 100000”.
+        // The maximum bandwidth limit. It’s in the following format:
+        // $MAX $PERIOD
+        // which indicates that the group may consume upto $MAX in each $PERIOD duration.
+        // “max” for $MAX indicates no limit. If only one number is written, $MAX is updated.
+
+        let current_value = self
+            .open_path("cpu.max", false)
+            .and_then(parse_cfs_quota_and_period)?;
+
+        let new_quota = if let Some(q) = quota {
+            if q > 0 {
+                q.to_string()
+            } else {
+                "max".to_string()
+            }
+        } else {
+            current_value.quota.to_string()
+        };
+
+        let new_period = if let Some(p) = period {
+            p.to_string()
+        } else {
+            current_value.period.to_string()
+        };
+
+        let line = format!("{} {}", new_quota, new_period);
+        self.open_path("cpu.max", true).and_then(|mut file| {
+            file.write_all(line.as_ref())
+                .map_err(|e| Error::with_cause(WriteFailed("cpu.max".to_string(), line), e))
+        })
+    }
+
+    pub fn set_rt_runtime(&self, us: i64) -> Result<()> {
+        self.open_path("cpu.rt_runtime_us", true)
+            .and_then(|mut file| {
+                file.write_all(us.to_string().as_ref()).map_err(|e| {
+                    Error::with_cause(
+                        WriteFailed("cpu.rt_runtime_us".to_string(), us.to_string()),
+                        e,
+                    )
+                })
+            })
+    }
+
+    pub fn set_rt_period_us(&self, us: u64) -> Result<()> {
+        self.open_path("cpu.rt_period_us", true)
+            .and_then(|mut file| {
+                file.write_all(us.to_string().as_ref()).map_err(|e| {
+                    Error::with_cause(
+                        WriteFailed("cpu.rt_period_us".to_string(), us.to_string()),
+                        e,
+                    )
+                })
+            })
+    }
+}
+
+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)
+        .map_err(|e| Error::with_cause(ReadFailed("cpu.max".to_string()), e))?;
+
+    let fields = content.trim().split(' ').collect::<Vec<&str>>();
+    if fields.len() != 2 {
+        return Err(Error::from_string(format!("invaild format: {}", content)));
+    }
+
+    let quota = parse_max_value(fields[0])?;
+    let period = fields[1]
+        .parse::<u64>()
+        .map_err(|e| Error::with_cause(ParseError, e))?;
+
+    Ok(CfsQuotaAndPeriod { quota, period })
+}