Throw an error if cgroup tries to set cpu-shares more/less than the m…

…aximum/minimum permissible value.

Signed-off-by: Shishir Mahajan <shishir.mahajan@redhat.com>

cgroups/fs/apply_raw.go

@@ -1,8 +1,11 @@
 package fs
 
 import (
+	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"sync"
@@ -75,10 +78,13 @@ type data struct {
 }
 
 func (m *Manager) Apply(pid int) error {
+
 	if m.Cgroups == nil {
 		return nil
 	}
 
+	var c = m.Cgroups
+
 	d, err := getCgroupData(m.Cgroups, pid)
 	if err != nil {
 		return err
@@ -108,6 +114,28 @@ func (m *Manager) Apply(pid int) error {
 	}
 	m.Paths = paths
 
+	var cpuShares int64
+
+	fd, err := os.Open(path.Join(m.Paths["cpu"], "cpu.shares"))
+	if err != nil {
+		return err
+	}
+
+	_, err = fmt.Fscanf(fd, "%d", &cpuShares)
+	if err != nil && err != io.EOF {
+		return err
+	}
+
+	fd.Close()
+
+	if c.CpuShares != 0 {
+		if c.CpuShares > cpuShares {
+			return fmt.Errorf("The maximum allowed cpu-shares is %d", cpuShares)
+		} else if c.CpuShares < cpuShares {
+			return fmt.Errorf("The minimum allowed cpu-shares is %d", cpuShares)
+		}
+	}
+
 	return nil
 }
 

cgroups/systemd/apply_systemd.go

@@ -5,8 +5,10 @@ package systemd
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -241,6 +243,28 @@ func (m *Manager) Apply(pid int) error {
 
 	m.Paths = paths
 
+	var cpuShares int64
+
+	fd, err := os.Open(path.Join(m.Paths["cpu"], "cpu.shares"))
+	if err != nil {
+		return err
+	}
+
+	_, err = fmt.Fscanf(fd, "%d", &cpuShares)
+	if err != nil && err != io.EOF {
+		return err
+	}
+
+	fd.Close()
+
+	if c.CpuShares != 0 {
+		if c.CpuShares > cpuShares {
+			return fmt.Errorf("The maximum allowed cpu-shares is %d", cpuShares)
+		} else if c.CpuShares < cpuShares {
+			return fmt.Errorf("The minimum allowed cpu-shares is %d", cpuShares)
+		}
+	}
+
 	return nil
 }