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package cgroups
import (
"bufio"
"fmt"
"os"
"path/filepath"
"strings"
)
// V1 returns all the groups in the default cgroups mountpoint in a single hierarchy
func V1() ([]Subsystem, error) {
root, err := v1MountPoint()
if err != nil {
return nil, err
}
subsystems, err := defaults(root)
if err != nil {
return nil, err
}
var enabled []Subsystem
for _, s := range pathers(subsystems) {
// check and remove the default groups that do not exist
if _, err := os.Lstat(s.Path("/")); err == nil {
enabled = append(enabled, s)
}
}
return enabled, nil
}
// v1MountPoint returns the mount point where the cgroup
// mountpoints are mounted in a single hiearchy
func v1MountPoint() (string, error) {
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return "", err
}
defer f.Close()
scanner := bufio.NewScanner(f)
for scanner.Scan() {
if err := scanner.Err(); err != nil {
return "", err
}
var (
text = scanner.Text()
fields = strings.Split(text, " ")
// safe as mountinfo encodes mountpoints with spaces as \040.
index = strings.Index(text, " - ")
postSeparatorFields = strings.Fields(text[index+3:])
numPostFields = len(postSeparatorFields)
)
// this is an error as we can't detect if the mount is for "cgroup"
if numPostFields == 0 {
return "", fmt.Errorf("Found no fields post '-' in %q", text)
}
if postSeparatorFields[0] == "cgroup" {
// check that the mount is properly formated.
if numPostFields < 3 {
return "", fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
}
return filepath.Dir(fields[4]), nil
}
}
return "", ErrMountPointNotExist
}
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