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Fix: cgroup2: Check cgroup existence on Load #384

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Fix: cgroup2: Check cgroup existence on Load #384

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c4c9976
Add: cgroup2: Test Load
Berbe Nov 29, 2025
dbf9ebd
Fix: cgroup2: Check cgroup existence on Load
Berbe Nov 29, 2025
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4 changes: 4 additions & 0 deletions cgroup2/manager.go
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Original file line number Diff line number Diff line change
Expand Up @@ -224,6 +224,10 @@ func Load(group string, opts ...InitOpts) (*Manager, error) {
return nil, err
}
path := filepath.Join(c.mountpoint, group)
_, err := os.Stat(path)
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@fuweid fuweid Jan 15, 2026

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I am not sure we should check this. It's just loading into object.
All the operations doesn't hold fd for this path. It could be valid case that Load it first and create it later.

ping @AkihiroSuda @mikebrow @dmcgowan to review this.

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@dcantah dcantah Jan 15, 2026 •
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I would, maybe naively, expect a function named Load to verify what we were trying to load is valid, and that's how I'd envision the API would be used (try to load an existing cgroup, and if it's not there I'd want to get some classic stdlib error to handle the not existing case). We could discuss whether Stat is a good enough metric for proving it's valid as well (e.g. maybe we want to actually see whether the path is a path in a cg2 mountpoint), but that's another topic. The API for creating and getting a handle to a cg2 in this library is NewManager(), and the only other way to create a new cg through the API is manager.NewChild(), but the expectation is you'd be creating a child cg from the one you already have a handle to.

if err != nil {
return nil, err
}
return &Manager{
unifiedMountpoint: c.mountpoint,
path: path,
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20 changes: 20 additions & 0 deletions cgroup2/manager_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ package cgroup2
import (
"context"
"fmt"
"io/fs"
"os"
"os/exec"
"syscall"
Expand Down Expand Up @@ -466,3 +467,22 @@ func BenchmarkStat(b *testing.B) {
func toPtr[T any](v T) *T {
return &v
}

func TestLoadOKWhenExistent(t *testing.T) {
checkCgroupMode(t)
group := "/existent"

_, err := NewManager(defaultCgroup2Path, group, &Resources{})
require.NoError(t, err)

_, err = Load(group)
require.NoError(t, err)
}

func TestLoadErrorsWhenNonExistent(t *testing.T) {
checkCgroupMode(t)
group := "/nonexistent"

_, err := Load(group)
require.ErrorIs(t, err, fs.ErrNotExist)
}
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