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fs: initialize subsystems lazily #90

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Merged
thaJeztah merged 1 commit into from
Oct 14, 2026
Merged

fs: initialize subsystems lazily #90

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54 changes: 29 additions & 25 deletions fs/fs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -14,33 +14,37 @@ import (
"github.com/opencontainers/cgroups/fscommon"
)

var subsystems = []subsystem{
&CpusetGroup{},
&DevicesGroup{},
&MemoryGroup{},
&CpuGroup{},
&CpuacctGroup{},
&PidsGroup{},
&BlkioGroup{},
&HugetlbGroup{},
&NetClsGroup{},
&NetPrioGroup{},
&PerfEventGroup{},
&FreezerGroup{},
&RdmaGroup{},
&NameGroup{GroupName: "name=systemd", Join: true},
&NameGroup{GroupName: "misc", Join: true, GroupID: cgroups.Misc},
}

var errSubsystemDoesNotExist = errors.New("cgroup: subsystem does not exist")
// subsystems returns the list of supported subsystems. It is initialized
// lazily to avoid doing any filesystem access during package initialization.
var subsystems = sync.OnceValue(func() []subsystem {
ss := []subsystem{
&CpusetGroup{},
&DevicesGroup{},
&MemoryGroup{},
&CpuGroup{},
&CpuacctGroup{},
&PidsGroup{},
&BlkioGroup{},
&HugetlbGroup{},
&NetClsGroup{},
&NetPrioGroup{},
&PerfEventGroup{},
&FreezerGroup{},
&RdmaGroup{},
&NameGroup{GroupName: "name=systemd", Join: true},
&NameGroup{GroupName: "misc", Join: true, GroupID: cgroups.Misc},
}

func init() {
// If using cgroups-hybrid mode then add a "" controller indicating
// it should join the cgroups v2.
if cgroups.IsCgroup2HybridMode() {
subsystems = append(subsystems, &NameGroup{GroupName: "", Join: true})
ss = append(ss, &NameGroup{GroupName: "", Join: true})
}
}

return ss
})

var errSubsystemDoesNotExist = errors.New("cgroup: subsystem does not exist")

type subsystem interface {
// Name returns the name of the subsystem.
Expand Down Expand Up @@ -114,7 +118,7 @@ func (m *Manager) Apply(pid int) (retErr error) {

c := m.cgroups

for _, sys := range subsystems {
for _, sys := range subsystems() {
name := sys.Name()
p, ok := m.paths[name]
if !ok {
Expand Down Expand Up @@ -199,7 +203,7 @@ func (m *Manager) Stats(opts *cgroups.StatsOptions) (*cgroups.Stats, error) {
}

stats := cgroups.NewStats()
for _, sys := range subsystems {
for _, sys := range subsystems() {
path := m.paths[sys.Name()]
if path == "" {
continue
Expand Down Expand Up @@ -228,7 +232,7 @@ func (m *Manager) Set(r *cgroups.Resources) error {

m.mu.Lock()
defer m.mu.Unlock()
for _, sys := range subsystems {
for _, sys := range subsystems() {
path := m.paths[sys.Name()]
if err := sys.Set(path, r); err != nil {
// When rootless is true, errors from the device subsystem
Expand Down
2 changes: 1 addition & 1 deletion fs/paths.go
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,7 @@ func initPaths(cg *cgroups.Cgroup) (map[string]string, error) {
}

paths := make(map[string]string)
for _, sys := range subsystems {
for _, sys := range subsystems() {
name := sys.Name()
path, err := subsysPath(root, inner, name)
if err != nil {
Expand Down
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