feat(orchestrator/nbd): inspect and disconnect connected devices

packages/orchestrator/pkg/sandbox/cgroup/manager.go

@@ -428,8 +428,7 @@ func (m *managerImpl) Destroy(ctx context.Context, cgroupName string) error {
 		return err
 	}
 
-	// Remove kills any remaining processes internally and returns nil once the
-	// cgroup is gone, so it is the authoritative teardown signal.
+	// Remove kills any remaining processes and deletes the cgroup.
 	return handle.Remove(ctx)
 }
 

packages/orchestrator/pkg/sandbox/nbd/path_direct.go

@@ -331,6 +331,10 @@ func disconnectNBDWithTimeout(ctx context.Context, deviceIndex uint32, timeout t
 	return nil
 }
 
+func DisconnectDevice(ctx context.Context, deviceIndex DeviceSlot) error {
+	return disconnectNBDWithTimeout(ctx, deviceIndex, disconnectTimeout)
+}
+
 func closeSocketPairs(socksClient []*os.File, socksServer []io.Closer) error {
 	var errs []error
 	for _, sock := range socksClient {

packages/orchestrator/pkg/sandbox/nbd/pool.go

@@ -25,6 +25,7 @@
 const (
 	waitOnNBDError                = 50 * time.Millisecond
 	devicePoolCloseReleaseTimeout = 10 * time.Minute
+	sysBlockDir                   = "/sys/block"
 )
 
 var (
@@ -126,6 +127,43 @@
 	return uint(maxDevices), nil
 }
 
+func ConnectedDevices() ([]DeviceSlot, error) {
+	maxDevices, err := getMaxDevices()
+	if err != nil {
+		return nil, err
+	}
+
+	devices := make([]DeviceSlot, 0)
+	for slot := DeviceSlot(0); slot < DeviceSlot(maxDevices); slot++ {
+		connected, err := isDeviceConnectedIn(sysBlockDir, slot)
+		if err != nil {
+			return nil, err
+		}
+		if connected {
+			devices = append(devices, slot)
+		}
+	}
+
+	return devices, nil
+}
+
+func IsDeviceConnected(slot DeviceSlot) (bool, error) {
+	return isDeviceConnectedIn(sysBlockDir, slot)
+}
+
+func isDeviceConnectedIn(blockDir string, slot DeviceSlot) (bool, error) {
+	pidFile := fmt.Sprintf("%s/nbd%d/pid", blockDir, slot)
+	_, err := os.Stat(pidFile)
+	if err == nil {
+		return true, nil
+	}
+	if !os.IsNotExist(err) {
+		return false, fmt.Errorf("failed to stat pid file: %w", err)
+	}
+
+	return false, nil
+}
+
 func (d *DevicePool) Populate(ctx context.Context) {
 	defer close(d.slots)
 
@@ -178,20 +216,15 @@
 // https://superuser.com/questions/919895/how-to-get-a-list-of-connected-nbd-devices-on-ubuntu
 // https://github.com/NetworkBlockDevice/nbd/blob/17043b068f4323078637314258158aebbfff0a6c/nbd-client.c#L254
 func (d *DevicePool) isDeviceFree(slot DeviceSlot) (bool, error) {
-	// Continue only if the file doesn't exist.
-	pidFile := fmt.Sprintf("/sys/block/nbd%d/pid", slot)
-
-	_, err := os.Stat(pidFile)
-	if err == nil {
+	connected, err := isDeviceConnectedIn(sysBlockDir, slot)
+	if err != nil {
+		return false, err
+	}
+	if connected {
 		// File is present, therefore the device is in use.
 		return false, nil
 	}
 
-	if !os.IsNotExist(err) {
-		// Some other error occurred.
-		return false, fmt.Errorf("failed to stat pid file: %w", err)
-	}
-
 	sizeFile := fmt.Sprintf("/sys/block/nbd%d/size", slot)
 
 	data, err := os.ReadFile(sizeFile)

packages/orchestrator/pkg/sandbox/nbd/reclaim_test.go

@@ -0,0 +1,28 @@
+//go:build linux
+
+package nbd
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestIsDeviceConnectedIn(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	require.NoError(t, os.Mkdir(filepath.Join(dir, "nbd0"), 0o700))
+	require.NoError(t, os.Mkdir(filepath.Join(dir, "nbd1"), 0o700))
+	require.NoError(t, os.WriteFile(filepath.Join(dir, "nbd0", "pid"), []byte("123"), 0o600))
+
+	connected, err := isDeviceConnectedIn(dir, 0)
+	require.NoError(t, err)
+	require.True(t, connected)
+
+	connected, err = isDeviceConnectedIn(dir, 1)
+	require.NoError(t, err)
+	require.False(t, connected)
+}