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cgroup: support mount of cgroup2

convert a "cgroup" mount to "cgroup2" when the system uses cgroups v2
unified hierarchy.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
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giuseppe committed Sep 6, 2019
1 parent a6606a7 commit 718a566e02044b17f9894f7536640f2cfde8bff9
Showing with 81 additions and 55 deletions.
  1. +81 −55 libcontainer/rootfs_linux.go
@@ -209,6 +209,80 @@ func prepareBindMount(m *configs.Mount, rootfs string) error {
return nil
}

func mountCgroupV1(m *configs.Mount, rootfs, mountLabel string, enableCgroupns bool) error {
binds, err := getCgroupMounts(m)
if err != nil {
return err
}
var merged []string
for _, b := range binds {
ss := filepath.Base(b.Destination)
if strings.Contains(ss, ",") {
merged = append(merged, ss)
}
}
tmpfs := &configs.Mount{
Source: "tmpfs",
Device: "tmpfs",
Destination: m.Destination,
Flags: defaultMountFlags,
Data: "mode=755",
PropagationFlags: m.PropagationFlags,
}
if err := mountToRootfs(tmpfs, rootfs, mountLabel, enableCgroupns); err != nil {
return err
}
for _, b := range binds {
if enableCgroupns {
subsystemPath := filepath.Join(rootfs, b.Destination)
if err := os.MkdirAll(subsystemPath, 0755); err != nil {
return err
}
flags := defaultMountFlags
if m.Flags&unix.MS_RDONLY != 0 {
flags = flags | unix.MS_RDONLY
}
cgroupmount := &configs.Mount{
Source: "cgroup",
Device: "cgroup",
Destination: subsystemPath,
Flags: flags,
Data: filepath.Base(subsystemPath),
}
if err := mountNewCgroup(cgroupmount); err != nil {
return err
}
} else {
if err := mountToRootfs(b, rootfs, mountLabel, enableCgroupns); err != nil {
return err
}
}
}
for _, mc := range merged {
for _, ss := range strings.Split(mc, ",") {
// symlink(2) is very dumb, it will just shove the path into
// the link and doesn't do any checks or relative path
// conversion. Also, don't error out if the cgroup already exists.
if err := os.Symlink(mc, filepath.Join(rootfs, m.Destination, ss)); err != nil && !os.IsExist(err) {
return err
}
}
}
return nil
}

func mountCgroupV2(m *configs.Mount, rootfs, mountLabel string, enableCgroupns bool) error {
cgroupPath, err := securejoin.SecureJoin(rootfs, m.Destination)
if err != nil {
return err
}
if err := os.MkdirAll(cgroupPath, 0755); err != nil {
return err
}

return unix.Mount(m.Source, cgroupPath, "cgroup2", uintptr(m.Flags), m.Data)
}

func mountToRootfs(m *configs.Mount, rootfs, mountLabel string, enableCgroupns bool) error {
var (
dest = m.Destination
@@ -309,62 +383,14 @@ func mountToRootfs(m *configs.Mount, rootfs, mountLabel string, enableCgroupns b
}
}
case "cgroup":
binds, err := getCgroupMounts(m)
if err != nil {
return err
}
var merged []string
for _, b := range binds {
ss := filepath.Base(b.Destination)
if strings.Contains(ss, ",") {
merged = append(merged, ss)
}
}
tmpfs := &configs.Mount{
Source: "tmpfs",
Device: "tmpfs",
Destination: m.Destination,
Flags: defaultMountFlags,
Data: "mode=755",
PropagationFlags: m.PropagationFlags,
}
if err := mountToRootfs(tmpfs, rootfs, mountLabel, enableCgroupns); err != nil {
return err
}
for _, b := range binds {
if enableCgroupns {
subsystemPath := filepath.Join(rootfs, b.Destination)
if err := os.MkdirAll(subsystemPath, 0755); err != nil {
return err
}
flags := defaultMountFlags
if m.Flags&unix.MS_RDONLY != 0 {
flags = flags | unix.MS_RDONLY
}
cgroupmount := &configs.Mount{
Source: "cgroup",
Device: "cgroup",
Destination: subsystemPath,
Flags: flags,
Data: filepath.Base(subsystemPath),
}
if err := mountNewCgroup(cgroupmount); err != nil {
return err
}
} else {
if err := mountToRootfs(b, rootfs, mountLabel, enableCgroupns); err != nil {
return err
}
if cgroups.IsCgroup2UnifiedMode() {
if err := mountCgroupV2(m, rootfs, mountLabel, enableCgroupns); err != nil {
return err
}
}
for _, mc := range merged {
for _, ss := range strings.Split(mc, ",") {
// symlink(2) is very dumb, it will just shove the path into
// the link and doesn't do any checks or relative path
// conversion. Also, don't error out if the cgroup already exists.
if err := os.Symlink(mc, filepath.Join(rootfs, m.Destination, ss)); err != nil && !os.IsExist(err) {
return err
}
} else {

if err := mountCgroupV1(m, rootfs, mountLabel, enableCgroupns); err != nil {
return err
}
}
if m.Flags&unix.MS_RDONLY != 0 {

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