Rename cgroupNamespaceSupported, add details

This responds to review feedback from
moby#4308 (review)

Signed-off-by: Mark Yen <[email protected]>
(cherry picked from commit f9ccb09)
Signed-off-by: Justin Chadwell <[email protected]>

Author: mook-as

executor/oci/spec.go

@@ -137,7 +137,7 @@ func GenerateSpec(ctx context.Context, meta executor.Meta, mounts []executor.Mou
 		return nil, nil, err
 	}
 
-	if cgroupNamespaceSupported() {
+	if cgroupV2NamespaceSupported() {
 		s.Linux.Namespaces = append(s.Linux.Namespaces, specs.LinuxNamespace{
 			Type: specs.CgroupNamespace,
 		})

executor/oci/spec_unix.go

@@ -147,7 +147,11 @@ func getTracingSocket() string {
 	return fmt.Sprintf("unix://%s", tracingSocketPath)
 }
 
-func cgroupNamespaceSupported() bool {
+func cgroupV2NamespaceSupported() bool {
+	// Check if cgroups v2 namespaces are supported.  Trying to do cgroup
+	// namespaces with cgroups v1 results in EINVAL when we encounter a
+	// non-standard hierarchy.
+	// See https://github.com/moby/buildkit/issues/4108
 	cgroupNSOnce.Do(func() {
 		if _, err := os.Stat("/proc/self/ns/cgroup"); os.IsNotExist(err) {
 			return

executor/oci/spec_windows.go

@@ -64,6 +64,6 @@ func getTracingSocket() string {
 	return fmt.Sprintf("npipe://%s", filepath.ToSlash(tracingSocketPath))
 }
 
-func cgroupNamespaceSupported() bool {
+func cgroupV2NamespaceSupported() bool {
 	return false
 }