package cgroups
import (
"bufio"
"errors"
"fmt"
"io"
"os"
"path/filepath"
"strconv"
"strings"
"sync"
"time"
"github.com/opencontainers/runc/libcontainer/userns"
"github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
)
const (
CgroupProcesses = "cgroup.procs"
unifiedMountpoint = "/sys/fs/cgroup"
hybridMountpoint = "/sys/fs/cgroup/unified"
)
var (
isUnifiedOnce sync.Once
isUnified bool
isHybridOnce sync.Once
isHybrid bool
)
// IsCgroup2UnifiedMode returns whether we are running in cgroup v2 unified mode.
func IsCgroup2UnifiedMode() bool {
isUnifiedOnce.Do(func() {
var st unix.Statfs_t
err := unix.Statfs(unifiedMountpoint, &st)
if err != nil {
if os.IsNotExist(err) && userns.RunningInUserNS() {
// ignore the "not found" error if running in userns
logrus.WithError(err).Debugf("%s missing, assuming cgroup v1", unifiedMountpoint)
isUnified = false
return
}
panic(fmt.Sprintf("cannot statfs cgroup root: %s", err))
}
isUnified = st.Type == unix.CGROUP2_SUPER_MAGIC
})
return isUnified
}
// IsCgroup2HybridMode returns whether we are running in cgroup v2 hybrid mode.
func IsCgroup2HybridMode() bool {
isHybridOnce.Do(func() {
var st unix.Statfs_t
err := unix.Statfs(hybridMountpoint, &st)
if err != nil {
isHybrid = false
if !os.IsNotExist(err) {
// Report unexpected errors.
logrus.WithError(err).Debugf("statfs(%q) failed", hybridMountpoint)
}
return
}
isHybrid = st.Type == unix.CGROUP2_SUPER_MAGIC
})
return isHybrid
}
type Mount struct {
Mountpoint string
Root string
Subsystems []string
}
// GetCgroupMounts returns the mounts for the cgroup subsystems.
// all indicates whether to return just the first instance or all the mounts.
// This function should not be used from cgroupv2 code, as in this case
// all the controllers are available under the constant unifiedMountpoint.
func GetCgroupMounts(all bool) ([]Mount, error) {
if IsCgroup2UnifiedMode() {
// TODO: remove cgroupv2 case once all external users are converted
availableControllers, err := GetAllSubsystems()
if err != nil {
return nil, err
}
m := Mount{
Mountpoint: unifiedMountpoint,
Root: unifiedMountpoint,
Subsystems: availableControllers,
}
return []Mount{m}, nil
}
return getCgroupMountsV1(all)
}
// GetAllSubsystems returns all the cgroup subsystems supported by the kernel
func GetAllSubsystems() ([]string, error) {
// /proc/cgroups is meaningless for v2
// https://github.com/torvalds/linux/blob/v5.3/Documentation/admin-guide/cgroup-v2.rst#deprecated-v1-core-features
if IsCgroup2UnifiedMode() {
// "pseudo" controllers do not appear in /sys/fs/cgroup/cgroup.controllers.
// - devices: implemented in kernel 4.15
// - freezer: implemented in kernel 5.2
// We assume these are always available, as it is hard to detect availability.
pseudo := []string{"devices", "freezer"}
data, err := ReadFile("/sys/fs/cgroup", "cgroup.controllers")
if err != nil {
return nil, err
}
subsystems := append(pseudo, strings.Fields(data)...)
return subsystems, nil
}
f, err := os.Open("/proc/cgroups")
if err != nil {
return nil, err
}
defer f.Close()
subsystems := []string{}
s := bufio.NewScanner(f)
for s.Scan() {
text := s.Text()
if text[0] != '#' {
parts := strings.Fields(text)
if len(parts) >= 4 && parts[3] != "0" {
subsystems = append(subsystems, parts[0])
}
}
}
if err := s.Err(); err != nil {
return nil, err
}
return subsystems, nil
}
func readProcsFile(dir string) ([]int, error) {
f, err := OpenFile(dir, CgroupProcesses, os.O_RDONLY)
if err != nil {
return nil, err
}
defer f.Close()
var (
s = bufio.NewScanner(f)
out = []int{}
)
for s.Scan() {
if t := s.Text(); t != "" {
pid, err := strconv.Atoi(t)
if err != nil {
return nil, err
}
out = append(out, pid)
}
}
return out, s.Err()
}
// ParseCgroupFile parses the given cgroup file, typically /proc/self/cgroup
// or /proc/<pid>/cgroup, into a map of subsystems to cgroup paths, e.g.
//
// "cpu": "/user.slice/user-1000.slice"
// "pids": "/user.slice/user-1000.slice"
//
// etc.
//
// Note that for cgroup v2 unified hierarchy, there are no per-controller
// cgroup paths, so the resulting map will have a single element where the key
// is empty string ("") and the value is the cgroup path the <pid> is in.
func ParseCgroupFile(path string) (map[string]string, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
return parseCgroupFromReader(f)
}
// helper function for ParseCgroupFile to make testing easier
func parseCgroupFromReader(r io.Reader) (map[string]string, error) {
s := bufio.NewScanner(r)
cgroups := make(map[string]string)
for s.Scan() {
text := s.Text()
// from cgroups(7):
// /proc/[pid]/cgroup
// ...
// For each cgroup hierarchy ... there is one entry
// containing three colon-separated fields of the form:
// hierarchy-ID:subsystem-list:cgroup-path
parts := strings.SplitN(text, ":", 3)
if len(parts) < 3 {
return nil, fmt.Errorf("invalid cgroup entry: must contain at least two colons: %v", text)
}
for _, subs := range strings.Split(parts[1], ",") {
cgroups[subs] = parts[2]
}
}
if err := s.Err(); err != nil {
return nil, err
}
return cgroups, nil
}
func PathExists(path string) bool {
if _, err := os.Stat(path); err != nil {
return false
}
return true
}
func EnterPid(cgroupPaths map[string]string, pid int) error {
for _, path := range cgroupPaths {
if PathExists(path) {
if err := WriteCgroupProc(path, pid); err != nil {
return err
}
}
}
return nil
}
func rmdir(path string) error {
err := unix.Rmdir(path)
if err == nil || err == unix.ENOENT { //nolint:errorlint // unix errors are bare
return nil
}
return &os.PathError{Op: "rmdir", Path: path, Err: err}
}
// RemovePath aims to remove cgroup path. It does so recursively,
// by removing any subdirectories (sub-cgroups) first.
func RemovePath(path string) error {
// try the fast path first
if err := rmdir(path); err == nil {
return nil
}
infos, err := os.ReadDir(path)
if err != nil {
if os.IsNotExist(err) {
err = nil
}
return err
}
for _, info := range infos {
if info.IsDir() {
// We should remove subcgroups dir first
if err = RemovePath(filepath.Join(path, info.Name())); err != nil {
break
}
}
}
if err == nil {
err = rmdir(path)
}
return err
}
// RemovePaths iterates over the provided paths removing them.
// We trying to remove all paths five times with increasing delay between tries.
// If after all there are not removed cgroups - appropriate error will be
// returned.
func RemovePaths(paths map[string]string) (err error) {
const retries = 5
delay := 10 * time.Millisecond
for i := 0; i < retries; i++ {
if i != 0 {
time.Sleep(delay)
delay *= 2
}
for s, p := range paths {
if err := RemovePath(p); err != nil {
// do not log intermediate iterations
switch i {
case 0:
logrus.WithError(err).Warnf("Failed to remove cgroup (will retry)")
case retries - 1:
logrus.WithError(err).Error("Failed to remove cgroup")
}
}
_, err := os.Stat(p)
// We need this strange way of checking cgroups existence because
// RemoveAll almost always returns error, even on already removed
// cgroups
if os.IsNotExist(err) {
delete(paths, s)
}
}
if len(paths) == 0 {
//nolint:ineffassign,staticcheck // done to help garbage collecting: opencontainers/runc#2506
paths = make(map[string]string)
return nil
}
}
return fmt.Errorf("Failed to remove paths: %v", paths)
}
var (
hugePageSizes []string
initHPSOnce sync.Once
)
func HugePageSizes() []string {
initHPSOnce.Do(func() {
dir, err := os.OpenFile("/sys/kernel/mm/hugepages", unix.O_DIRECTORY|unix.O_RDONLY, 0)
if err != nil {
return
}
files, err := dir.Readdirnames(0)
dir.Close()
if err != nil {
return
}
hugePageSizes, err = getHugePageSizeFromFilenames(files)
if err != nil {
logrus.Warn("HugePageSizes: ", err)
}
})
return hugePageSizes
}
func getHugePageSizeFromFilenames(fileNames []string) ([]string, error) {
pageSizes := make([]string, 0, len(fileNames))
var warn error
for _, file := range fileNames {
// example: hugepages-1048576kB
val := strings.TrimPrefix(file, "hugepages-")
if len(val) == len(file) {
// Unexpected file name: no prefix found, ignore it.
continue
}
// The suffix is always "kB" (as of Linux 5.13). If we find
// something else, produce an error but keep going.
eLen := len(val) - 2
val = strings.TrimSuffix(val, "kB")
if len(val) != eLen {
// Highly unlikely.
if warn == nil {
warn = errors.New(file + `: invalid suffix (expected "kB")`)
}
continue
}
size, err := strconv.Atoi(val)
if err != nil {
// Highly unlikely.
if warn == nil {
warn = fmt.Errorf("%s: %w", file, err)
}
continue
}
// Model after https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/hugetlb_cgroup.c?id=eff48ddeab782e35e58ccc8853f7386bbae9dec4#n574
// but in our case the size is in KB already.
if size >= (1 << 20) {
val = strconv.Itoa(size>>20) + "GB"
} else if size >= (1 << 10) {
val = strconv.Itoa(size>>10) + "MB"
} else {
val += "KB"
}
pageSizes = append(pageSizes, val)
}
return pageSizes, warn
}
// GetPids returns all pids, that were added to cgroup at path.
func GetPids(dir string) ([]int, error) {
return readProcsFile(dir)
}
// WriteCgroupProc writes the specified pid into the cgroup's cgroup.procs file
func WriteCgroupProc(dir string, pid int) error {
// Normally dir should not be empty, one case is that cgroup subsystem
// is not mounted, we will get empty dir, and we want it fail here.
if dir == "" {
return fmt.Errorf("no such directory for %s", CgroupProcesses)
}
// Dont attach any pid to the cgroup if -1 is specified as a pid
if pid == -1 {
return nil
}
file, err := OpenFile(dir, CgroupProcesses, os.O_WRONLY)
if err != nil {
return fmt.Errorf("failed to write %v: %w", pid, err)
}
defer file.Close()
for i := 0; i < 5; i++ {
_, err = file.WriteString(strconv.Itoa(pid))
if err == nil {
return nil
}
// EINVAL might mean that the task being added to cgroup.procs is in state
// TASK_NEW. We should attempt to do so again.
if errors.Is(err, unix.EINVAL) {
time.Sleep(30 * time.Millisecond)
continue
}
return fmt.Errorf("failed to write %v: %w", pid, err)
}
return err
}
// Since the OCI spec is designed for cgroup v1, in some cases
// there is need to convert from the cgroup v1 configuration to cgroup v2
// the formula for cpuShares is y = (1 + ((x - 2) * 9999) / 262142)
// convert from [2-262144] to [1-10000]
// 262144 comes from Linux kernel definition "#define MAX_SHARES (1UL << 18)"
func ConvertCPUSharesToCgroupV2Value(cpuShares uint64) uint64 {
if cpuShares == 0 {
return 0
}
return (1 + ((cpuShares-2)*9999)/262142)
}
// ConvertMemorySwapToCgroupV2Value converts MemorySwap value from OCI spec
// for use by cgroup v2 drivers. A conversion is needed since Resources.MemorySwap
// is defined as memory+swap combined, while in cgroup v2 swap is a separate value.
func ConvertMemorySwapToCgroupV2Value(memorySwap, memory int64) (int64, error) {
// for compatibility with cgroup1 controller, set swap to unlimited in
// case the memory is set to unlimited, and swap is not explicitly set,
// treating the request as "set both memory and swap to unlimited".
if memory == -1 && memorySwap == 0 {
return -1, nil
}
if memorySwap == -1 || memorySwap == 0 {
// -1 is "max", 0 is "unset", so treat as is
return memorySwap, nil
}
// sanity checks
if memory == 0 || memory == -1 {
return 0, errors.New("unable to set swap limit without memory limit")
}
if memory < 0 {
return 0, fmt.Errorf("invalid memory value: %d", memory)
}
if memorySwap < memory {
return 0, errors.New("memory+swap limit should be >= memory limit")
}
return memorySwap - memory, nil
}
// Since the OCI spec is designed for cgroup v1, in some cases
// there is need to convert from the cgroup v1 configuration to cgroup v2
// the formula for BlkIOWeight to IOWeight is y = (1 + (x - 10) * 9999 / 990)
// convert linearly from [10-1000] to [1-10000]
func ConvertBlkIOToIOWeightValue(blkIoWeight uint16) uint64 {
if blkIoWeight == 0 {
return 0
}
return 1 + (uint64(blkIoWeight)-10)*9999/990
}
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