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kolyshkin wants to merge 2 commits into from
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libct/cgroups/fs: rm getCgroupRoot #2497

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9cfe0d1
cgroups/fs tests: unify TestInvalid*Cgroup*
kolyshkin Jun 9, 2020
1cb24ac
cgroup/fs: remove getCgroupRoot
kolyshkin Jun 3, 2020
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71 changes: 3 additions & 68 deletions libcontainer/cgroups/fs/fs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,11 +3,9 @@
package fs

import (
"bufio"
"fmt"
"os"
"path/filepath"
"strings"
"sync"

"github.com/opencontainers/runc/libcontainer/cgroups"
Expand Down Expand Up @@ -78,66 +76,9 @@ func NewManager(cg *configs.Cgroup, paths map[string]string, rootless bool) cgro
}

// The absolute path to the root of the cgroup hierarchies.
var cgroupRootLock sync.Mutex
var cgroupRoot string

// Gets the cgroupRoot.
func getCgroupRoot() (string, error) {
cgroupRootLock.Lock()
defer cgroupRootLock.Unlock()

if cgroupRoot != "" {
return cgroupRoot, nil
}

f, err := os.Open("/proc/self/mountinfo")
if err != nil {
return "", err
}
defer f.Close()

var root string
scanner := bufio.NewScanner(f)
for scanner.Scan() {
text := scanner.Text()
fields := strings.Split(text, " ")
// Safe as mountinfo encodes mountpoints with spaces as \040.
index := strings.Index(text, " - ")
postSeparatorFields := strings.Fields(text[index+3:])
numPostFields := len(postSeparatorFields)

// This is an error as we can't detect if the mount is for "cgroup"
if numPostFields == 0 {
return "", fmt.Errorf("mountinfo: found no fields post '-' in %q", text)
}

if postSeparatorFields[0] == "cgroup" {
// Check that the mount is properly formatted.
if numPostFields < 3 {
return "", fmt.Errorf("Error found less than 3 fields post '-' in %q", text)
}

root = filepath.Dir(fields[4])
break
}
}
if err := scanner.Err(); err != nil {
return "", err
}
if root == "" {
return "", errors.New("no cgroup mount found in mountinfo")
}

if _, err := os.Stat(root); err != nil {
return "", err
}

cgroupRoot = root
return cgroupRoot, nil
}
const cgroupRoot = "/sys/fs/cgroup"

type cgroupData struct {
root string
innerPath string
config *configs.Cgroup
pid int
Expand Down Expand Up @@ -323,11 +264,6 @@ func (m *manager) GetAllPids() ([]int, error) {
}

func getCgroupData(c *configs.Cgroup, pid int) (*cgroupData, error) {
root, err := getCgroupRoot()
if err != nil {
return nil, err
}

if (c.Name != "" || c.Parent != "") && c.Path != "" {
return nil, errors.New("cgroup: either Path or Name and Parent should be used")
}
Expand All @@ -343,7 +279,6 @@ func getCgroupData(c *configs.Cgroup, pid int) (*cgroupData, error) {
}

return &cgroupData{
root: root,
innerPath: innerPath,
config: c,
pid: pid,
Expand All @@ -353,14 +288,14 @@ func getCgroupData(c *configs.Cgroup, pid int) (*cgroupData, error) {
func (raw *cgroupData) path(subsystem string) (string, error) {
// If the cgroup name/path is absolute do not look relative to the cgroup of the init process.
if filepath.IsAbs(raw.innerPath) {
mnt, err := cgroups.FindCgroupMountpoint(raw.root, subsystem)
mnt, err := cgroups.FindCgroupMountpoint(cgroupRoot, subsystem)
// If we didn't mount the subsystem, there is no point we make the path.
if err != nil {
return "", err
}

// Sometimes subsystems can be mounted together as 'cpu,cpuacct'.
return filepath.Join(raw.root, filepath.Base(mnt), raw.innerPath), nil
return filepath.Join(cgroupRoot, filepath.Base(mnt), raw.innerPath), nil
}

// Use GetOwnCgroupPath instead of GetInitCgroupPath, because the creating
Expand Down
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