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/*
Copyright The containerd Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package cgroups
import (
"bufio"
"fmt"
"io"
"os"
"path/filepath"
"strings"
"sync"
"github.com/moby/sys/userns"
"golang.org/x/sys/unix"
)
var (
checkMode sync.Once
cgMode CGMode
)
const unifiedMountpoint = "/sys/fs/cgroup"
// CGMode is the cgroups mode of the host system
type CGMode int
const (
// Unavailable cgroup mountpoint
Unavailable CGMode = iota
// Legacy cgroups v1
Legacy
// Hybrid with cgroups v1 and v2 controllers mounted
Hybrid
// Unified with only cgroups v2 mounted
Unified
)
// Mode returns the cgroups mode running on the host
func Mode() CGMode {
checkMode.Do(func() {
var st unix.Statfs_t
if err := unix.Statfs(unifiedMountpoint, &st); err != nil {
cgMode = Unavailable
return
}
switch st.Type {
case unix.CGROUP2_SUPER_MAGIC:
cgMode = Unified
default:
cgMode = Legacy
if err := unix.Statfs(filepath.Join(unifiedMountpoint, "unified"), &st); err != nil {
return
}
if st.Type == unix.CGROUP2_SUPER_MAGIC {
cgMode = Hybrid
}
}
})
return cgMode
}
// RunningInUserNS detects whether we are currently running in a user namespace.
// Copied from github.com/lxc/lxd/shared/util.go
//
// Deprecated: use [userns.RunningInUserNS].
func RunningInUserNS() bool {
return userns.RunningInUserNS()
}
// ParseCgroupFileUnified returns legacy subsystem paths as the first value,
// and returns the unified path as the second value.
func ParseCgroupFileUnified(path string) (map[string]string, string, error) {
f, err := os.Open(path)
if err != nil {
return nil, "", err
}
defer f.Close()
return ParseCgroupFromReaderUnified(f)
}
// ParseCgroupFromReaderUnified returns legacy subsystem paths as the first value,
// and returns the unified path as the second value.
func ParseCgroupFromReaderUnified(r io.Reader) (map[string]string, string, error) {
var (
cgroups = make(map[string]string)
unified = ""
s = bufio.NewScanner(r)
)
for s.Scan() {
var (
text = s.Text()
parts = strings.SplitN(text, ":", 3)
)
if len(parts) < 3 {
return nil, unified, fmt.Errorf("invalid cgroup entry: %q", text)
}
for _, subs := range strings.Split(parts[1], ",") {
if subs == "" {
unified = parts[2]
} else {
cgroups[subs] = parts[2]
}
}
}
if err := s.Err(); err != nil {
return nil, unified, err
}
return cgroups, unified, nil
}
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