Return NotFound error for cgroups abs paths

Signed-off-by: Michael Crosby <michael@docker.com>

cgroups/fs/apply_raw.go

@@ -168,12 +168,24 @@ func (raw *data) Paths() (map[string]string, error) {
 func (raw *data) 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.cgroup) {
-		return filepath.Join(raw.root, subsystem, raw.cgroup), nil
+		path := filepath.Join(raw.root, subsystem, raw.cgroup)
+
+		if _, err := os.Stat(path); err != nil {
+			if os.IsNotExist(err) {
+				return "", cgroups.ErrNotFound
 			}
+
+			return "", err
+		}
+
+		return path, nil
+	}
+
 	parent, err := raw.parent(subsystem)
 	if err != nil {
 		return "", err
 	}
+
 	return filepath.Join(parent, raw.cgroup), nil
 }
 

cgroups/fs/utils_test.go

@@ -5,8 +5,6 @@ import (
 	"os"
 	"path/filepath"
 	"testing"
-
-	"github.com/docker/libcontainer/cgroups"
 )
 
 const (
@@ -68,20 +66,3 @@ func TestGetCgroupParamsInt(t *testing.T) {
 		t.Fatal("Expecting error, got none")
 	}
 }
-
-func TestAbsolutePathHandling(t *testing.T) {
-	testCgroup := cgroups.Cgroup{
-		Name:   "bar",
-		Parent: "/foo",
-	}
-	cgroupData := data{
-		root:   "/sys/fs/cgroup",
-		cgroup: "/foo/bar",
-		c:      &testCgroup,
-		pid:    1,
-	}
-	expectedPath := filepath.Join(cgroupData.root, "cpu", testCgroup.Parent, testCgroup.Name)
-	if path, err := cgroupData.path("cpu"); path != expectedPath || err != nil {
-		t.Fatalf("expected path %s but got %s %s", expectedPath, path, err)
-	}
-}