diff --git a/client/llb/fileop.go b/client/llb/fileop.go
index 18d1d68e1..731aa6199 100644
--- a/client/llb/fileop.go
+++ b/client/llb/fileop.go
@@ -4,6 +4,8 @@ import (
 	_ "crypto/sha256"
 	"os"
 	"path"
+	"strconv"
+	"strings"
 	"time"
 
 	"github.com/moby/buildkit/solver/pb"
@@ -29,11 +31,12 @@ import (
 // filestate = state.File(c)
 // filestate.GetOutput(id).Exec()
 
-func NewFileOp(s State, action *FileAction) *FileOp {
+func NewFileOp(s State, action *FileAction, c Constraints) *FileOp {
 	action = action.bind(s)
 
 	f := &FileOp{
-		action: action,
+		action:      action,
+		constraints: c,
 	}
 
 	f.output = &output{vertex: f, getIndex: func() (pb.OutputIndex, error) {
@@ -190,9 +193,40 @@ func (mi *MkdirInfo) SetMkdirOption(mi2 *MkdirInfo) {
 }
 
 func WithUser(name string) ChownOption {
-	return ChownOpt{
-		User: &UserOpt{Name: name},
+	opt := ChownOpt{}
+
+	parts := strings.SplitN(name, ":", 2)
+	for i, v := range parts {
+		switch i {
+		case 0:
+			uid, err := parseUID(v)
+			if err != nil {
+				opt.User = &UserOpt{Name: v}
+			} else {
+				opt.User = &UserOpt{UID: uid}
+			}
+		case 1:
+			gid, err := parseUID(v)
+			if err != nil {
+				opt.Group = &UserOpt{Name: v}
+			} else {
+				opt.Group = &UserOpt{UID: gid}
+			}
+		}
 	}
+
+	return opt
+}
+
+func parseUID(str string) (int, error) {
+	if str == "root" {
+		return 0, nil
+	}
+	uid, err := strconv.ParseInt(str, 10, 32)
+	if err != nil {
+		return 0, err
+	}
+	return int(uid), nil
 }
 
 func WithUIDGID(uid, gid int) ChownOption {
@@ -479,7 +513,7 @@ type FileOp struct {
 	action *FileAction
 	output Output
 
-	// constraints Constraints
+	constraints Constraints
 	isValidated bool
 }
 
@@ -610,7 +644,7 @@ func (f *FileOp) Marshal(c *Constraints) (digest.Digest, []byte, *pb.OpMetadata,
 
 	pfo := &pb.FileOp{}
 
-	pop, md := MarshalConstraints(c, &Constraints{})
+	pop, md := MarshalConstraints(c, &f.constraints)
 	pop.Op = &pb.Op_File{
 		File: pfo,
 	}
diff --git a/client/llb/state.go b/client/llb/state.go
index 5929e19a5..0336b7fd1 100644
--- a/client/llb/state.go
+++ b/client/llb/state.go
@@ -229,8 +229,13 @@ func (s State) Run(ro ...RunOption) ExecState {
 	}
 }
 
-func (s State) File(a *FileAction) State {
-	return s.WithOutput(NewFileOp(s, a).Output())
+func (s State) File(a *FileAction, opts ...ConstraintsOpt) State {
+	var c Constraints
+	for _, o := range opts {
+		o.SetConstraintsOption(&c)
+	}
+
+	return s.WithOutput(NewFileOp(s, a, c).Output())
 }
 
 func (s State) AddEnv(key, value string) State {
diff --git a/examples/dockerfile2llb/main.go b/examples/dockerfile2llb/main.go
index 9b31ea5d3..41d2d4d2b 100644
--- a/examples/dockerfile2llb/main.go
+++ b/examples/dockerfile2llb/main.go
@@ -9,6 +9,7 @@ import (
 	"github.com/moby/buildkit/client/llb"
 	"github.com/moby/buildkit/client/llb/imagemetaresolver"
 	"github.com/moby/buildkit/frontend/dockerfile/dockerfile2llb"
+	"github.com/moby/buildkit/solver/pb"
 	"github.com/moby/buildkit/util/appcontext"
 )
 
@@ -26,9 +27,12 @@ func main() {
 		panic(err)
 	}
 
+	caps := pb.Caps.CapSet(pb.Caps.All())
+
 	state, img, err := dockerfile2llb.Dockerfile2LLB(appcontext.Context(), df, dockerfile2llb.ConvertOpt{
 		MetaResolver: imagemetaresolver.Default(),
 		Target:       opt.target,
+		LLBCaps:      &caps,
 	})
 	if err != nil {
 		log.Printf("err: %+v", err)
diff --git a/frontend/dockerfile/dockerfile2llb/convert.go b/frontend/dockerfile/dockerfile2llb/convert.go
index 42ea06146..cb9b1e7af 100644
--- a/frontend/dockerfile/dockerfile2llb/convert.go
+++ b/frontend/dockerfile/dockerfile2llb/convert.go
@@ -151,6 +151,10 @@ func Dockerfile2LLB(ctx context.Context, dt []byte, opt ConvertOpt) (*llb.State,
 			switch cmd.(type) {
 			case *instructions.AddCommand, *instructions.CopyCommand, *instructions.RunCommand:
 				total++
+			case *instructions.WorkdirCommand:
+				if useFileOp(opt.BuildArgs, opt.LLBCaps) {
+					total++
+				}
 			}
 		}
 		ds.cmdTotal = total
@@ -307,7 +311,7 @@ func Dockerfile2LLB(ctx context.Context, dt []byte, opt ConvertOpt) (*llb.State,
 			d.state = d.state.AddEnv(k, v)
 		}
 		if d.image.Config.WorkingDir != "" {
-			if err = dispatchWorkdir(d, &instructions.WorkdirCommand{Path: d.image.Config.WorkingDir}, false); err != nil {
+			if err = dispatchWorkdir(d, &instructions.WorkdirCommand{Path: d.image.Config.WorkingDir}, false, nil); err != nil {
 				return nil, nil, err
 			}
 		}
@@ -468,7 +472,7 @@ func dispatch(d *dispatchState, cmd command, opt dispatchOpt) error {
 	case *instructions.RunCommand:
 		err = dispatchRun(d, c, opt.proxyEnv, cmd.sources, opt)
 	case *instructions.WorkdirCommand:
-		err = dispatchWorkdir(d, c, true)
+		err = dispatchWorkdir(d, c, true, &opt)
 	case *instructions.AddCommand:
 		err = dispatchCopy(d, c.SourcesAndDest, opt.buildContext, true, c, "", opt)
 		if err == nil {
@@ -648,7 +652,7 @@ func dispatchRun(d *dispatchState, c *instructions.RunCommand, proxy *llb.ProxyE
 	return commitToHistory(&d.image, "RUN "+runCommandString(args, d.buildArgs), true, &d.state)
 }
 
-func dispatchWorkdir(d *dispatchState, c *instructions.WorkdirCommand, commit bool) error {
+func dispatchWorkdir(d *dispatchState, c *instructions.WorkdirCommand, commit bool, opt *dispatchOpt) error {
 	d.state = d.state.Dir(c.Path)
 	wd := c.Path
 	if !path.IsAbs(c.Path) {
@@ -656,13 +660,114 @@ func dispatchWorkdir(d *dispatchState, c *instructions.WorkdirCommand, commit bo
 	}
 	d.image.Config.WorkingDir = wd
 	if commit {
+		if opt != nil && useFileOp(opt.buildArgValues, opt.llbCaps) {
+			mkdirOpt := []llb.MkdirOption{llb.WithParents(true)}
+			if user := d.image.Config.User; user != "" {
+				mkdirOpt = append(mkdirOpt, llb.WithUser(user))
+			}
+			platform := opt.targetPlatform
+			if d.platform != nil {
+				platform = *d.platform
+			}
+			d.state = d.state.File(llb.Mkdir(wd, 0755, mkdirOpt...), llb.WithCustomName(prefixCommand(d, uppercaseCmd(processCmdEnv(opt.shlex, c.String(), d.state.Env())), d.prefixPlatform, &platform)))
+		}
+
 		return commitToHistory(&d.image, "WORKDIR "+wd, false, nil)
 	}
 	return nil
 }
 
+func dispatchCopyFileOp(d *dispatchState, c instructions.SourcesAndDest, sourceState llb.State, isAddCommand bool, cmdToPrint fmt.Stringer, chown string, opt dispatchOpt) error {
+	dest := path.Join("/", pathRelativeToWorkingDir(d.state, c.Dest()))
+	if c.Dest() == "." || c.Dest() == "" || c.Dest()[len(c.Dest())-1] == filepath.Separator {
+		dest += string(filepath.Separator)
+	}
+
+	var copyOpt []llb.CopyOption
+
+	if chown != "" {
+		copyOpt = append(copyOpt, llb.WithUser(chown))
+	}
+
+	commitMessage := bytes.NewBufferString("")
+	if isAddCommand {
+		commitMessage.WriteString("ADD")
+	} else {
+		commitMessage.WriteString("COPY")
+	}
+
+	var a *llb.FileAction
+
+	for _, src := range c.Sources() {
+		commitMessage.WriteString(" " + src)
+		if strings.HasPrefix(src, "http://") || strings.HasPrefix(src, "https://") {
+			if !isAddCommand {
+				return errors.New("source can't be a URL for COPY")
+			}
+
+			// Resources from remote URLs are not decompressed.
+			// https://docs.docker.com/engine/reference/builder/#add
+			//
+			// Note: mixing up remote archives and local archives in a single ADD instruction
+			// would result in undefined behavior: https://github.com/moby/buildkit/pull/387#discussion_r189494717
+			u, err := url.Parse(src)
+			f := "__unnamed__"
+			if err == nil {
+				if base := path.Base(u.Path); base != "." && base != "/" {
+					f = base
+				}
+			}
+
+			st := llb.HTTP(src, llb.Filename(f), dfCmd(c))
+
+			opts := append([]llb.CopyOption{&llb.CopyInfo{
+				CreateDestPath: true,
+			}}, copyOpt...)
+
+			if a == nil {
+				a = llb.Copy(st, f, dest, opts...)
+			} else {
+				a = a.Copy(st, f, dest, opts...)
+			}
+		} else {
+			opts := append([]llb.CopyOption{&llb.CopyInfo{
+				FollowSymlinks:      true,
+				CopyDirContentsOnly: true,
+				AttemptUnpack:       isAddCommand,
+				CreateDestPath:      true,
+				AllowWildcard:       true,
+				AllowEmptyWildcard:  true,
+			}}, copyOpt...)
+
+			if a == nil {
+				a = llb.Copy(sourceState, src, dest, opts...)
+			} else {
+				a = a.Copy(sourceState, src, dest, opts...)
+			}
+		}
+	}
+
+	commitMessage.WriteString(" " + c.Dest())
+
+	platform := opt.targetPlatform
+	if d.platform != nil {
+		platform = *d.platform
+	}
+
+	fileOpt := []llb.ConstraintsOpt{llb.WithCustomName(prefixCommand(d, uppercaseCmd(processCmdEnv(opt.shlex, cmdToPrint.String(), d.state.Env())), d.prefixPlatform, &platform))}
+	if d.ignoreCache {
+		fileOpt = append(fileOpt, llb.IgnoreCache)
+	}
+
+	d.state = d.state.File(a, fileOpt...)
+	return commitToHistory(&d.image, commitMessage.String(), true, &d.state)
+}
+
 func dispatchCopy(d *dispatchState, c instructions.SourcesAndDest, sourceState llb.State, isAddCommand bool, cmdToPrint fmt.Stringer, chown string, opt dispatchOpt) error {
-	// TODO: this should use CopyOp instead. Current implementation is inefficient
+	if useFileOp(opt.buildArgValues, opt.llbCaps) {
+		return dispatchCopyFileOp(d, c, sourceState, isAddCommand, cmdToPrint, chown, opt)
+	}
+
 	img := llb.Image(opt.copyImage, llb.MarkImageInternal, llb.Platform(opt.buildPlatforms[0]), WithInternalName("helper image for file operations"))
 
 	dest := path.Join(".", pathRelativeToWorkingDir(d.state, c.Dest()))
@@ -1176,3 +1281,13 @@ func prefixCommand(ds *dispatchState, str string, prefixPlatform bool, platform
 	out += fmt.Sprintf("%d/%d] ", ds.cmdIndex, ds.cmdTotal)
 	return out + str
 }
+
+func useFileOp(args map[string]string, caps *apicaps.CapSet) bool {
+	enabled := fileOpEnabled
+	if v, ok := args["BUILDKIT_USE_FILEOP"]; ok {
+		if b, err := strconv.ParseBool(v); err != nil {
+			enabled = b
+		}
+	}
+	return enabled && caps != nil && caps.Supports(pb.CapFileBase) == nil
+}
diff --git a/frontend/dockerfile/dockerfile2llb/convert_fileop.go b/frontend/dockerfile/dockerfile2llb/convert_fileop.go
new file mode 100644
index 000000000..9c8abc7c3
--- /dev/null
+++ b/frontend/dockerfile/dockerfile2llb/convert_fileop.go
@@ -0,0 +1,5 @@
+// +build fileop
+
+package dockerfile2llb
+
+const fileOpEnabled = true
diff --git a/frontend/dockerfile/dockerfile2llb/convert_nofileop.go b/frontend/dockerfile/dockerfile2llb/convert_nofileop.go
new file mode 100644
index 000000000..f8f7582b0
--- /dev/null
+++ b/frontend/dockerfile/dockerfile2llb/convert_nofileop.go
@@ -0,0 +1,5 @@
+// +build !fileop
+
+package dockerfile2llb
+
+const fileOpEnabled = false
diff --git a/solver/llbsolver/ops/file.go b/solver/llbsolver/ops/file.go
index 013778fe0..379d1df9a 100644
--- a/solver/llbsolver/ops/file.go
+++ b/solver/llbsolver/ops/file.go
@@ -46,15 +46,23 @@ func NewFileOp(v solver.Vertex, op *pb.Op_File, cm cache.Manager, md *metadata.S
 
 func (f *fileOp) CacheMap(ctx context.Context, index int) (*solver.CacheMap, bool, error) {
 	selectors := map[int]map[llbsolver.Selector]struct{}{}
+	invalidSelectors := map[int]struct{}{}
 
 	actions := make([][]byte, 0, len(f.op.Actions))
 
+	markInvalid := func(idx pb.InputIndex) {
+		if idx != -1 {
+			invalidSelectors[int(idx)] = struct{}{}
+		}
+	}
+
 	for _, action := range f.op.Actions {
 		var dt []byte
 		var err error
 		switch a := action.Action.(type) {
 		case *pb.FileAction_Mkdir:
 			p := *a.Mkdir
+			markInvalid(action.Input)
 			processOwner(p.Owner, selectors)
 			dt, err = json.Marshal(p)
 			if err != nil {
@@ -62,7 +70,7 @@ func (f *fileOp) CacheMap(ctx context.Context, index int) (*solver.CacheMap, boo
 			}
 		case *pb.FileAction_Mkfile:
 			p := *a.Mkfile
-			p.Owner = nil
+			markInvalid(action.Input)
 			processOwner(p.Owner, selectors)
 			dt, err = json.Marshal(p)
 			if err != nil {
@@ -70,14 +78,15 @@ func (f *fileOp) CacheMap(ctx context.Context, index int) (*solver.CacheMap, boo
 			}
 		case *pb.FileAction_Rm:
 			p := *a.Rm
+			markInvalid(action.Input)
 			dt, err = json.Marshal(p)
 			if err != nil {
 				return nil, false, err
 			}
 		case *pb.FileAction_Copy:
 			p := *a.Copy
+			markInvalid(action.Input)
 			processOwner(p.Owner, selectors)
-			p.Owner = nil
 			if action.SecondaryInput != -1 && int(action.SecondaryInput) < f.numInputs {
 				p.Src = path.Base(p.Src)
 				addSelector(selectors, int(action.SecondaryInput), p.Src, p.AllowWildcard, p.FollowSymlink)
@@ -111,6 +120,9 @@ func (f *fileOp) CacheMap(ctx context.Context, index int) (*solver.CacheMap, boo
 	}
 
 	for idx, m := range selectors {
+		if _, ok := invalidSelectors[idx]; ok {
+			continue
+		}
 		dgsts := make([][]byte, 0, len(m))
 		for k := range m {
 			dgsts = append(dgsts, []byte(k.Path))
diff --git a/solver/pb/caps.go b/solver/pb/caps.go
index b81ec62c4..add5c17ed 100644
--- a/solver/pb/caps.go
+++ b/solver/pb/caps.go
@@ -43,6 +43,8 @@ const (
 	CapExecMountSSH            apicaps.CapID = "exec.mount.ssh"
 	CapExecCgroupsMounted      apicaps.CapID = "exec.cgroup"
 
+	CapFileBase apicaps.CapID = "file.base"
+
 	CapConstraints apicaps.CapID = "constraints"
 	CapPlatform    apicaps.CapID = "platform"
 
@@ -226,6 +228,12 @@ func init() {
 		Status:  apicaps.CapStatusExperimental,
 	})
 
+	Caps.Init(apicaps.Cap{
+		ID:      CapFileBase,
+		Enabled: true,
+		Status:  apicaps.CapStatusPrerelease,
+	})
+
 	Caps.Init(apicaps.Cap{
 		ID:      CapConstraints,
 		Enabled: true,