fix: minor improvements to fs

- Do not create target dir for detached mounts;
- Use 'ro' flag on ReadOnly mount requests;

Signed-off-by: Mateusz Urbanek <mateusz.urbanek@siderolabs.com>

Author: shanduur

internal/app/machined/pkg/controllers/block/mount.go

@@ -495,6 +495,7 @@ func (ctrl *MountController) handleDiskMountOperation(
 
 		if mountRequest.TypedSpec().ReadOnly {
 			opts = append(opts, mount.WithReadOnly())
+			fsOpts = append(fsOpts, fsopen.WithBoolParameter("ro"))
 		}
 
 		if mountRequest.TypedSpec().Detached {

internal/app/machined/pkg/runtime/v1alpha1/platform/metal/metal.go

@@ -181,6 +181,7 @@ func readConfigFromISO(ctx context.Context, r state.State) ([]byte, error) {
 		mount.WithPrinter(log.Printf),
 		mount.WithFsopen(
 			volumeStatus.TypedSpec().Filesystem.String(),
+			fsopen.WithBoolParameter("ro"),
 			fsopen.WithSource(volumeStatus.TypedSpec().MountLocation),
 		),
 	)

internal/pkg/mount/v3/manager.go

@@ -85,11 +85,13 @@ func (m *Manager) Mount() (*Point, error) {
 		MountAttributes: m.mountattr,
 	}
 
-	if err := os.MkdirAll(m.target, 0o755); err != nil {
-		return nil, fmt.Errorf("failed to create mount target %s: %w", m.target, err)
-	}
+	if !m.detached {
+		if err := os.MkdirAll(m.target, 0o755); err != nil {
+			return nil, fmt.Errorf("failed to create mount target %s: %w", m.target, err)
+		}
 
-	printer("mounting %q to %q", m.point.Source(), m.target)
+		printer("mounting %q to %q", m.point.Source(), m.target)
+	}
 
 	if err := m.point.Mount(opts); err != nil {
 		return nil, fmt.Errorf("failed to mount: %w", err)

internal/pkg/mount/v3/point.go

@@ -51,6 +51,12 @@ type Options struct {
 
 // Mount the mount point.
 func (p *Point) Mount(opts Options) error {
+	defer p.Release(false) //nolint:errcheck
+
+	if p.detached {
+		return nil
+	}
+
 	if opts.SkipIfMounted {
 		isMounted, err := p.IsMounted()
 		if err != nil {
@@ -62,12 +68,6 @@ func (p *Point) Mount(opts Options) error {
 		}
 	}
 
-	defer p.Release(false) //nolint:errcheck
-
-	if p.detached {
-		return nil
-	}
-
 	return p.retry(func() error {
 		if err := p.moveMount(p.target); err != nil {
 			return fmt.Errorf("error mounting %q to %q: %w", p.Source(), p.target, err)