common/pkg: error check IsCgroup2UnifiedMode and assume true

Signed-off-by: Lokesh Mandvekar <[email protected]>

Author: lsm5

common/pkg/cgroups/cgroups_linux.go

@@ -541,15 +541,10 @@ func cpusetCopyFileFromParent(dir, file string, cgroupv2 bool) ([]byte, error) {
 
 // SystemCPUUsage returns the system usage for all the cgroups.
 func SystemCPUUsage() (uint64, error) {
-	cgroupv2, err := IsCgroup2UnifiedMode()
+	_, err := IsCgroup2UnifiedMode()
 	if err != nil {
 		return 0, err
 	}
-	if !cgroupv2 {
-		p := filepath.Join(cgroupRoot, CPUAcct, "cpuacct.usage")
-		return readFileAsUint64(p)
-	}
-
 	files, err := os.ReadDir(cgroupRoot)
 	if err != nil {
 		return 0, err
@@ -602,7 +597,7 @@ func UserConnection(uid int) (*systemdDbus.Conn, error) {
 func UserOwnsCurrentSystemdCgroup() (bool, error) {
 	uid := os.Geteuid()
 
-	cgroup2, err := IsCgroup2UnifiedMode()
+	_, err := IsCgroup2UnifiedMode()
 	if err != nil {
 		return false, err
 	}
@@ -624,20 +619,11 @@ func UserOwnsCurrentSystemdCgroup() (bool, error) {
 
 		// If we are on a cgroup v2 system and there are cgroup v1 controllers
 		// mounted, ignore them when the current process is at the root cgroup.
-		if cgroup2 && parts[1] != "" && parts[2] == "/" {
+		if parts[1] != "" && parts[2] == "/" {
 			continue
 		}
 
-		var cgroupPath string
-
-		if cgroup2 {
-			cgroupPath = filepath.Join(cgroupRoot, parts[2])
-		} else {
-			if parts[1] != "name=systemd" {
-				continue
-			}
-			cgroupPath = filepath.Join(cgroupRoot, "systemd", parts[2])
-		}
+		cgroupPath := filepath.Join(cgroupRoot, parts[2])
 
 		st, err := os.Stat(cgroupPath)
 		if err != nil {

common/pkg/cgroups/utils_linux.go

@@ -15,7 +15,6 @@ import (
 
 	"github.com/opencontainers/cgroups"
 	"github.com/sirupsen/logrus"
-	"go.podman.io/storage/pkg/fileutils"
 	"golang.org/x/sys/unix"
 )
 
@@ -207,7 +206,7 @@ func MoveUnderCgroup(cgroup, subtree string, processes []uint32) error {
 	}
 	defer f.Close()
 
-	unifiedMode, err := IsCgroup2UnifiedMode()
+	_, err = IsCgroup2UnifiedMode()
 	if err != nil {
 		return err
 	}
@@ -221,24 +220,12 @@ func MoveUnderCgroup(cgroup, subtree string, processes []uint32) error {
 		}
 
 		// root cgroup, skip it
-		if parts[2] == "/" && (!unifiedMode || parts[1] != "") {
+		if parts[2] == "/" && parts[1] != "" {
 			continue
 		}
 
 		cgroupRoot := "/sys/fs/cgroup"
-		// Special case the unified mount on hybrid cgroup and named hierarchies.
-		// This works on Fedora 31, but we should really parse the mounts to see
-		// where the cgroup hierarchy is mounted.
-		if parts[1] == "" && !unifiedMode {
-			// If it is not using unified mode, the cgroup v2 hierarchy is
-			// usually mounted under /sys/fs/cgroup/unified
-			cgroupRoot = filepath.Join(cgroupRoot, "unified")
-
-			// Ignore the unified mount if it doesn't exist
-			if err := fileutils.Exists(cgroupRoot); err != nil && os.IsNotExist(err) {
-				continue
-			}
-		} else if parts[1] != "" {
+		if parts[1] != "" {
 			// Assume the controller is mounted at /sys/fs/cgroup/$CONTROLLER.
 			controller := strings.TrimPrefix(parts[1], "name=")
 			cgroupRoot = filepath.Join(cgroupRoot, controller)
@@ -292,15 +279,11 @@ var (
 // it is running in the root cgroup on a system that uses cgroupv2.
 func MaybeMoveToSubCgroup() error {
 	maybeMoveToSubCgroupSync.Do(func() {
-		unifiedMode, err := IsCgroup2UnifiedMode()
+		_, err := IsCgroup2UnifiedMode()
 		if err != nil {
 			maybeMoveToSubCgroupSyncErr = err
 			return
 		}
-		if !unifiedMode {
-			maybeMoveToSubCgroupSyncErr = nil
-			return
-		}
 		cgroup, err := GetOwnCgroup()
 		if err != nil {
 			maybeMoveToSubCgroupSyncErr = err

common/pkg/sysinfo/sysinfo_linux.go

@@ -229,21 +229,11 @@ func checkCgroupCpusetInfo(cgMounts map[string]string, quiet bool) cgroupCpusetI
 
 // checkCgroupPids reads the pids information from the pids cgroup mount point.
 func checkCgroupPids(cgMounts map[string]string, quiet bool) cgroupPids {
-	cgroup2, err := cgroupv2.IsCgroup2UnifiedMode()
+	_, err := cgroupv2.IsCgroup2UnifiedMode()
 	if err != nil {
 		logrus.Errorf("Failed to check cgroups version: %v", err)
 		return cgroupPids{}
 	}
-	if !cgroup2 {
-		_, ok := cgMounts["pids"]
-		if !ok {
-			if !quiet {
-				logrus.Warn("Unable to find pids cgroup in mounts")
-			}
-			return cgroupPids{}
-		}
-	}
-
 	return cgroupPids{
 		PidsLimit: true,
 	}

common/pkg/systemd/systemd_linux.go

@@ -88,14 +88,12 @@ func MovePauseProcessToScope(pausePidPath string) {
 	}
 
 	if err != nil {
-		unified, err2 := cgroups.IsCgroup2UnifiedMode()
+		_, err2 := cgroups.IsCgroup2UnifiedMode()
 		if err2 != nil {
 			logrus.Warnf("Failed to detect if running with cgroup unified: %v", err)
 		}
-		if RunsOnSystemd() && unified {
+		if RunsOnSystemd() {
 			logrus.Warnf("Failed to add pause process to systemd sandbox cgroup: %v", err)
-		} else {
-			logrus.Debugf("Failed to add pause process to systemd sandbox cgroup: %v", err)
 		}
 	}
 }