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|
package cgroups
import (
"bufio"
"errors"
"fmt"
"io"
"os"
"path/filepath"
"strings"
)
// Code in this source file are specific to cgroup v1,
// and must not be used from any cgroup v2 code.
const (
CgroupNamePrefix = "name="
)
var (
errUnified = errors.New("not implemented for cgroup v2 unified hierarchy")
)
type NotFoundError struct {
Subsystem string
}
func (e *NotFoundError) Error() string {
return fmt.Sprintf("mountpoint for %s not found", e.Subsystem)
}
func NewNotFoundError(sub string) error {
return &NotFoundError{
Subsystem: sub,
}
}
func IsNotFound(err error) bool {
if err == nil {
return false
}
_, ok := err.(*NotFoundError)
return ok
}
// https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
func FindCgroupMountpoint(cgroupPath, subsystem string) (string, error) {
if IsCgroup2UnifiedMode() {
return "", errUnified
}
mnt, _, err := FindCgroupMountpointAndRoot(cgroupPath, subsystem)
return mnt, err
}
func FindCgroupMountpointAndRoot(cgroupPath, subsystem string) (string, string, error) {
if IsCgroup2UnifiedMode() {
return "", "", errUnified
}
// We are not using mount.GetMounts() because it's super-inefficient,
// parsing it directly sped up x10 times because of not using Sscanf.
// It was one of two major performance drawbacks in container start.
if !isSubsystemAvailable(subsystem) {
return "", "", NewNotFoundError(subsystem)
}
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return "", "", err
}
defer f.Close()
return findCgroupMountpointAndRootFromReader(f, cgroupPath, subsystem)
}
func findCgroupMountpointAndRootFromReader(reader io.Reader, cgroupPath, subsystem string) (string, string, error) {
scanner := bufio.NewScanner(reader)
for scanner.Scan() {
txt := scanner.Text()
fields := strings.Fields(txt)
if len(fields) < 9 {
continue
}
if strings.HasPrefix(fields[4], cgroupPath) {
for _, opt := range strings.Split(fields[len(fields)-1], ",") {
if opt == subsystem {
return fields[4], fields[3], nil
}
}
}
}
if err := scanner.Err(); err != nil {
return "", "", err
}
return "", "", NewNotFoundError(subsystem)
}
func isSubsystemAvailable(subsystem string) bool {
if IsCgroup2UnifiedMode() {
panic("don't call isSubsystemAvailable from cgroupv2 code")
}
cgroups, err := ParseCgroupFile("/proc/self/cgroup")
if err != nil {
return false
}
_, avail := cgroups[subsystem]
return avail
}
func (m Mount) GetOwnCgroup(cgroups map[string]string) (string, error) {
if len(m.Subsystems) == 0 {
return "", fmt.Errorf("no subsystem for mount")
}
return getControllerPath(m.Subsystems[0], cgroups)
}
func getCgroupMountsHelper(ss map[string]bool, mi io.Reader, all bool) ([]Mount, error) {
res := make([]Mount, 0, len(ss))
scanner := bufio.NewScanner(mi)
numFound := 0
for scanner.Scan() && numFound < len(ss) {
txt := scanner.Text()
sepIdx := strings.Index(txt, " - ")
if sepIdx == -1 {
return nil, fmt.Errorf("invalid mountinfo format")
}
if txt[sepIdx+3:sepIdx+10] == "cgroup2" || txt[sepIdx+3:sepIdx+9] != "cgroup" {
continue
}
fields := strings.Split(txt, " ")
m := Mount{
Mountpoint: fields[4],
Root: fields[3],
}
for _, opt := range strings.Split(fields[len(fields)-1], ",") {
seen, known := ss[opt]
if !known || (!all && seen) {
continue
}
ss[opt] = true
opt = strings.TrimPrefix(opt, CgroupNamePrefix)
m.Subsystems = append(m.Subsystems, opt)
numFound++
}
if len(m.Subsystems) > 0 || all {
res = append(res, m)
}
}
if err := scanner.Err(); err != nil {
return nil, err
}
return res, nil
}
func getCgroupMountsV1(all bool) ([]Mount, error) {
f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return nil, err
}
defer f.Close()
allSubsystems, err := ParseCgroupFile("/proc/self/cgroup")
if err != nil {
return nil, err
}
allMap := make(map[string]bool)
for s := range allSubsystems {
allMap[s] = false
}
return getCgroupMountsHelper(allMap, f, all)
}
// GetOwnCgroup returns the relative path to the cgroup docker is running in.
func GetOwnCgroup(subsystem string) (string, error) {
if IsCgroup2UnifiedMode() {
return "", errUnified
}
cgroups, err := ParseCgroupFile("/proc/self/cgroup")
if err != nil {
return "", err
}
return getControllerPath(subsystem, cgroups)
}
func GetOwnCgroupPath(subsystem string) (string, error) {
cgroup, err := GetOwnCgroup(subsystem)
if err != nil {
return "", err
}
return getCgroupPathHelper(subsystem, cgroup)
}
func GetInitCgroup(subsystem string) (string, error) {
if IsCgroup2UnifiedMode() {
return "", errUnified
}
cgroups, err := ParseCgroupFile("/proc/1/cgroup")
if err != nil {
return "", err
}
return getControllerPath(subsystem, cgroups)
}
func GetInitCgroupPath(subsystem string) (string, error) {
cgroup, err := GetInitCgroup(subsystem)
if err != nil {
return "", err
}
return getCgroupPathHelper(subsystem, cgroup)
}
func getCgroupPathHelper(subsystem, cgroup string) (string, error) {
mnt, root, err := FindCgroupMountpointAndRoot("", subsystem)
if err != nil {
return "", err
}
// This is needed for nested containers, because in /proc/self/cgroup we
// see paths from host, which don't exist in container.
relCgroup, err := filepath.Rel(root, cgroup)
if err != nil {
return "", err
}
return filepath.Join(mnt, relCgroup), nil
}
func getControllerPath(subsystem string, cgroups map[string]string) (string, error) {
if IsCgroup2UnifiedMode() {
return "", errUnified
}
if p, ok := cgroups[subsystem]; ok {
return p, nil
}
if p, ok := cgroups[CgroupNamePrefix+subsystem]; ok {
return p, nil
}
return "", NewNotFoundError(subsystem)
}
|
