mirror of https://github.com/k3s-io/k3s
115 lines
3.4 KiB
Go
115 lines
3.4 KiB
Go
package cgrouputil
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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"strings"
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"github.com/moby/sys/mountinfo"
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"github.com/pkg/errors"
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"github.com/sirupsen/logrus"
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)
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// EvacuateCgroup2 evacuates cgroup2. Must be called in the parent PID namespace.
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//
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// When the current process belongs to "/foo" group (visible under "/sys/fs/cgroup/foo") and evac is like "bar",
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// - All processes in the "/foo" group are moved to "/foo/bar" group, by writing PIDs into "/sys/fs/cgroup/foo/bar/cgroup.procs"
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// - As many controllers as possible are enabled for "/foo/*" groups, by writing "/sys/fs/cgroup/foo/cgroup.subtree_control"
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//
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// Returns nil when cgroup2 is not enabled.
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// Ported from https://github.com/rootless-containers/usernetes/commit/46ad812db7489914897ff8b1774f2fab0efda62b
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func EvacuateCgroup2(evac string) error {
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if evac == "" {
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return errors.New("got empty evacuation group name")
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}
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if strings.Contains(evac, "/") {
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return errors.Errorf("unexpected evacuation group name %q: must not contain \"/\"", evac)
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}
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mountpoint := findCgroup2Mountpoint()
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if mountpoint == "" {
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logrus.Warn("cgroup2 is not mounted. cgroup2 evacuation is discarded.")
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return nil
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}
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oldGroup := getCgroup2(os.Getpid())
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if mountpoint == "" {
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logrus.Warn("process is not running with cgroup2. cgroup2 evacuation is discarded.")
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return nil
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}
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newGroup := filepath.Join(oldGroup, evac)
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oldPath := filepath.Join(mountpoint, oldGroup)
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newPath := filepath.Join(mountpoint, newGroup)
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if err := os.MkdirAll(newPath, 0755); err != nil {
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return err
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}
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// evacuate existing procs from oldGroup to newGroup, so that we can enable all controllers including threaded ones
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cgroupProcsBytes, err := ioutil.ReadFile(filepath.Join(oldPath, "cgroup.procs"))
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if err != nil {
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return err
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}
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for _, pidStr := range strings.Split(string(cgroupProcsBytes), "\n") {
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if pidStr == "" || pidStr == "0" {
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continue
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}
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if err := ioutil.WriteFile(filepath.Join(newPath, "cgroup.procs"), []byte(pidStr), 0644); err != nil {
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logrus.WithError(err).Warnf("failed to move process %s to cgroup %q", pidStr, newGroup)
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}
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}
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// enable controllers for all subgroups under the oldGroup
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controllerBytes, err := ioutil.ReadFile(filepath.Join(oldPath, "cgroup.controllers"))
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if err != nil {
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return err
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}
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for _, controller := range strings.Fields(string(controllerBytes)) {
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logrus.Debugf("enabling controller %q", controller)
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if err := ioutil.WriteFile(filepath.Join(oldPath, "cgroup.subtree_control"), []byte("+"+controller), 0644); err != nil {
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logrus.WithError(err).Warnf("failed to enable controller %q", controller)
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}
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}
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return nil
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}
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func findCgroup2Mountpoint() string {
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f := mountinfoFSTypeFilter("cgroup2")
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mounts, err := mountinfo.GetMounts(f)
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if err != nil {
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logrus.WithError(err).Warn("failed to find mountpoint for cgroup2")
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return ""
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}
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if len(mounts) == 0 {
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return ""
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}
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if len(mounts) != 1 {
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logrus.Warnf("expected single mountpoint for cgroup2, got %d", len(mounts))
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}
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return mounts[0].Mountpoint
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}
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func getCgroup2(pid int) string {
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p := fmt.Sprintf("/proc/%d/cgroup", pid)
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b, err := ioutil.ReadFile(p)
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if err != nil {
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logrus.WithError(err).Warnf("failed to read %q", p)
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return ""
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}
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return getCgroup2FromProcPidCgroup(b)
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}
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func getCgroup2FromProcPidCgroup(b []byte) string {
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for _, l := range strings.Split(string(b), "\n") {
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if strings.HasPrefix(l, "0::") {
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return strings.TrimPrefix(l, "0::")
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}
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}
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return ""
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}
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