Merge pull request #3148 from masters-of-cats/wip-rootless-containerd

Skip rootfs unmount when no mounts are provided

mount/mount_linux.go

@@ -111,7 +111,18 @@ func unmount(target string, flags int) error {
 // UnmountAll repeatedly unmounts the given mount point until there
 // are no mounts remaining (EINVAL is returned by mount), which is
 // useful for undoing a stack of mounts on the same mount point.
+// UnmountAll all is noop when the first argument is an empty string.
+// This is done when the containerd client did not specify any rootfs
+// mounts (e.g. because the rootfs is managed outside containerd)
+// UnmountAll is noop when the mount path does not exist.
 func UnmountAll(mount string, flags int) error {
+	if mount == "" {
+		return nil
+	}
+	if _, err := os.Stat(mount); os.IsNotExist(err) {
+		return nil
+	}
+
 	for {
 		if err := unmount(mount, flags); err != nil {
 			// EINVAL is returned if the target is not a

runtime/v1/linux/bundle.go

@@ -65,9 +65,6 @@ func newBundle(id, path, workDir string, spec []byte) (b *bundle, err error) {
 			os.RemoveAll(workDir)
 		}
 	}()
-	if err := os.Mkdir(filepath.Join(path, "rootfs"), 0711); err != nil {
-		return nil, err
-	}
 	err = ioutil.WriteFile(filepath.Join(path, configFilename), spec, 0666)
 	return &bundle{
 		id:      id,

runtime/v1/shim/service.go

@@ -124,6 +124,14 @@ func (s *Service) Create(ctx context.Context, r *shimapi.CreateTaskRequest) (_ *
 		})
 	}
 
+	rootfs := ""
+	if len(mounts) > 0 {
+		rootfs = filepath.Join(r.Bundle, "rootfs")
+		if err := os.Mkdir(rootfs, 0711); err != nil {
+			return nil, err
+		}
+	}
+
 	config := &proc.CreateConfig{
 		ID:               r.ID,
 		Bundle:           r.Bundle,
@@ -137,7 +145,6 @@ func (s *Service) Create(ctx context.Context, r *shimapi.CreateTaskRequest) (_ *
 		ParentCheckpoint: r.ParentCheckpoint,
 		Options:          r.Options,
 	}
-	rootfs := filepath.Join(r.Bundle, "rootfs")
 	defer func() {
 		if err != nil {
 			if err2 := mount.UnmountAll(rootfs, 0); err2 != nil {
@@ -169,6 +176,7 @@ func (s *Service) Create(ctx context.Context, r *shimapi.CreateTaskRequest) (_ *
 		s.config.SystemdCgroup,
 		s.platform,
 		config,
+		rootfs,
 	)
 	if err != nil {
 		return nil, errdefs.ToGRPC(err)
@@ -632,7 +640,7 @@ func getTopic(ctx context.Context, e interface{}) string {
 	return runtime.TaskUnknownTopic
 }
 
-func newInit(ctx context.Context, path, workDir, runtimeRoot, namespace, criu string, systemdCgroup bool, platform rproc.Platform, r *proc.CreateConfig) (*proc.Init, error) {
+func newInit(ctx context.Context, path, workDir, runtimeRoot, namespace, criu string, systemdCgroup bool, platform rproc.Platform, r *proc.CreateConfig, rootfs string) (*proc.Init, error) {
 	var options runctypes.CreateOptions
 	if r.Options != nil {
 		v, err := typeurl.UnmarshalAny(r.Options)
@@ -642,7 +650,6 @@ func newInit(ctx context.Context, path, workDir, runtimeRoot, namespace, criu st
 		options = *v.(*runctypes.CreateOptions)
 	}
 
-	rootfs := filepath.Join(path, "rootfs")
 	runtime := proc.NewRunc(runtimeRoot, path, namespace, r.Runtime, criu, systemdCgroup)
 	p := proc.New(r.ID, runtime, rproc.Stdio{
 		Stdin:    r.Stdin,

runtime/v2/bundle.go

@@ -89,10 +89,6 @@ func NewBundle(ctx context.Context, root, state, id string, spec []byte) (b *Bun
 		}
 	}
 	paths = append(paths, work)
-	// create rootfs dir
-	if err := os.Mkdir(filepath.Join(b.Path, "rootfs"), 0711); err != nil {
-		return nil, err
-	}
 	// symlink workdir
 	if err := os.Symlink(work, filepath.Join(b.Path, "work")); err != nil {
 		return nil, err

runtime/v2/runc/container.go

@@ -21,6 +21,7 @@ package runc
 import (
 	"context"
 	"io/ioutil"
+	"os"
 	"path/filepath"
 	"sync"
 
@@ -63,6 +64,15 @@ func NewContainer(ctx context.Context, platform rproc.Platform, r *task.CreateTa
 			Options: m.Options,
 		})
 	}
+
+	rootfs := ""
+	if len(mounts) > 0 {
+		rootfs = filepath.Join(r.Bundle, "rootfs")
+		if err := os.Mkdir(rootfs, 0711); err != nil {
+			return nil, err
+		}
+	}
+
 	config := &proc.CreateConfig{
 		ID:               r.ID,
 		Bundle:           r.Bundle,
@@ -80,7 +90,6 @@ func NewContainer(ctx context.Context, platform rproc.Platform, r *task.CreateTa
 	if err := WriteRuntime(r.Bundle, opts.BinaryName); err != nil {
 		return nil, err
 	}
-	rootfs := filepath.Join(r.Bundle, "rootfs")
 	defer func() {
 		if err != nil {
 			if err2 := mount.UnmountAll(rootfs, 0); err2 != nil {
@@ -107,6 +116,7 @@ func NewContainer(ctx context.Context, platform rproc.Platform, r *task.CreateTa
 		platform,
 		config,
 		&opts,
+		rootfs,
 	)
 	if err != nil {
 		return nil, errdefs.ToGRPC(err)
@@ -146,8 +156,7 @@ func WriteRuntime(path, runtime string) error {
 }
 
 func newInit(ctx context.Context, path, workDir, namespace string, platform rproc.Platform,
-	r *proc.CreateConfig, options *options.Options) (*proc.Init, error) {
+	r *proc.CreateConfig, options *options.Options, rootfs string) (*proc.Init, error) {
-	rootfs := filepath.Join(path, "rootfs")
 	runtime := proc.NewRunc(options.Root, path, namespace, options.BinaryName, options.CriuPath, options.SystemdCgroup)
 	p := proc.New(r.ID, runtime, rproc.Stdio{
 		Stdin:    r.Stdin,