Merge pull request #3970 from MichaelEischer/split-retry-backend

Split backend package into smaller parts

cmd/restic/global.go

@@ -22,6 +22,7 @@ import (
 	"github.com/restic/restic/internal/backend/location"
 	"github.com/restic/restic/internal/backend/rclone"
 	"github.com/restic/restic/internal/backend/rest"
+	"github.com/restic/restic/internal/backend/retry"
 	"github.com/restic/restic/internal/backend/s3"
 	"github.com/restic/restic/internal/backend/sftp"
 	"github.com/restic/restic/internal/backend/swift"
@@ -445,7 +446,7 @@ func OpenRepository(ctx context.Context, opts GlobalOptions) (*repository.Reposi
 	success := func(msg string, retries int) {
 		Warnf("%v operation successful after %d retries\n", msg, retries)
 	}
-	be = backend.NewRetryBackend(be, 10, report, success)
+	be = retry.New(be, 10, report, success)
 
 	// wrap backend if a test specified a hook
 	if opts.backendTestHook != nil {

cmd/restic/integration_helpers_test.go

@@ -9,7 +9,7 @@ import (
 	"runtime"
 	"testing"
 
-	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/retry"
 	"github.com/restic/restic/internal/options"
 	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
@@ -172,7 +172,7 @@ func withTestEnvironment(t testing.TB) (env *testEnvironment, cleanup func()) {
 
 	repository.TestUseLowSecurityKDFParameters(t)
 	restic.TestDisableCheckPolynomial(t)
-	backend.TestFastRetries(t)
+	retry.TestFastRetries(t)
 
 	tempdir, err := ioutil.TempDir(rtest.TestTempDir, "restic-test-")
 	rtest.OK(t, err)

internal/backend/azure/azure.go

@@ -13,6 +13,7 @@ import (
 	"strings"
 
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -30,7 +31,7 @@ type Backend struct {
 	sem          sema.Semaphore
 	prefix       string
 	listMaxItems int
-	backend.Layout
+	layout.Layout
 }
 
 const defaultListMaxItems = 5000
@@ -85,7 +86,7 @@ func open(cfg Config, rt http.RoundTripper) (*Backend, error) {
 		connections: cfg.Connections,
 		sem:         sem,
 		prefix:      cfg.Prefix,
-		Layout: &backend.DefaultLayout{
+		Layout: &layout.DefaultLayout{
 			Path: cfg.Prefix,
 			Join: path.Join,
 		},

internal/backend/b2/b2.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -25,7 +26,7 @@ type b2Backend struct {
 	bucket       *b2.Bucket
 	cfg          Config
 	listMaxItems int
-	backend.Layout
+	layout.Layout
 	sem sema.Semaphore
 }
 
@@ -97,7 +98,7 @@ func Open(ctx context.Context, cfg Config, rt http.RoundTripper) (restic.Backend
 		client: client,
 		bucket: bucket,
 		cfg:    cfg,
-		Layout: &backend.DefaultLayout{
+		Layout: &layout.DefaultLayout{
 			Join: path.Join,
 			Path: cfg.Prefix,
 		},
@@ -138,7 +139,7 @@ func Create(ctx context.Context, cfg Config, rt http.RoundTripper) (restic.Backe
 		client: client,
 		bucket: bucket,
 		cfg:    cfg,
-		Layout: &backend.DefaultLayout{
+		Layout: &layout.DefaultLayout{
 			Join: path.Join,
 			Path: cfg.Prefix,
 		},

internal/backend/backend_error.go

@@ -1,84 +0,0 @@
-package backend
-
-import (
-	"context"
-	"io"
-	"io/ioutil"
-	"math/rand"
-	"sync"
-
-	"github.com/restic/restic/internal/errors"
-	"github.com/restic/restic/internal/restic"
-)
-
-// ErrorBackend is used to induce errors into various function calls and test
-// the retry functions.
-type ErrorBackend struct {
-	FailSave     float32
-	FailSaveRead float32
-	FailLoad     float32
-	FailStat     float32
-	restic.Backend
-
-	r *rand.Rand
-	m sync.Mutex
-}
-
-// statically ensure that ErrorBackend implements restic.Backend.
-var _ restic.Backend = &ErrorBackend{}
-
-// NewErrorBackend wraps be with a backend that returns errors according to
-// given probabilities.
-func NewErrorBackend(be restic.Backend, seed int64) *ErrorBackend {
-	return &ErrorBackend{
-		Backend: be,
-		r:       rand.New(rand.NewSource(seed)),
-	}
-}
-
-func (be *ErrorBackend) fail(p float32) bool {
-	be.m.Lock()
-	v := be.r.Float32()
-	be.m.Unlock()
-
-	return v < p
-}
-
-// Save stores the data in the backend under the given handle.
-func (be *ErrorBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
-	if be.fail(be.FailSave) {
-		return errors.Errorf("Save(%v) random error induced", h)
-	}
-
-	if be.fail(be.FailSaveRead) {
-		_, err := io.CopyN(ioutil.Discard, rd, be.r.Int63n(1000))
-		if err != nil {
-			return err
-		}
-
-		return errors.Errorf("Save(%v) random error with partial read induced", h)
-	}
-
-	return be.Backend.Save(ctx, h, rd)
-}
-
-// Load returns a reader that yields the contents of the file at h at the
-// given offset. If length is larger than zero, only a portion of the file
-// is returned. rd must be closed after use. If an error is returned, the
-// ReadCloser must be nil.
-func (be *ErrorBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64, consumer func(rd io.Reader) error) error {
-	if be.fail(be.FailLoad) {
-		return errors.Errorf("Load(%v, %v, %v) random error induced", h, length, offset)
-	}
-
-	return be.Backend.Load(ctx, h, length, offset, consumer)
-}
-
-// Stat returns information about the File identified by h.
-func (be *ErrorBackend) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {
-	if be.fail(be.FailLoad) {
-		return restic.FileInfo{}, errors.Errorf("Stat(%v) random error induced", h)
-	}
-
-	return be.Stat(ctx, h)
-}

internal/backend/gs/gs.go

@@ -14,6 +14,7 @@ import (
 	"cloud.google.com/go/storage"
 	"github.com/pkg/errors"
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/restic"
@@ -41,7 +42,7 @@ type Backend struct {
 	bucket       *storage.BucketHandle
 	prefix       string
 	listMaxItems int
-	backend.Layout
+	layout.Layout
 }
 
 // Ensure that *Backend implements restic.Backend.
@@ -111,7 +112,7 @@ func open(cfg Config, rt http.RoundTripper) (*Backend, error) {
 		bucketName:  cfg.Bucket,
 		bucket:      gcsClient.Bucket(cfg.Bucket),
 		prefix:      cfg.Prefix,
-		Layout: &backend.DefaultLayout{
+		Layout: &layout.DefaultLayout{
 			Path: cfg.Prefix,
 			Join: path.Join,
 		},

internal/backend/layout/layout.go

@@ -1,4 +1,4 @@
-package backend
+package layout
 
 import (
 	"context"

internal/backend/layout/layout_default.go

@@ -1,4 +1,4 @@
-package backend
+package layout
 
 import (
 	"encoding/hex"

internal/backend/layout/layout_rest.go

@@ -1,4 +1,4 @@
-package backend
+package layout
 
 import "github.com/restic/restic/internal/restic"
 

internal/backend/layout/layout_s3legacy.go

@@ -1,4 +1,4 @@
-package backend
+package layout
 
 import "github.com/restic/restic/internal/restic"
 

internal/backend/layout/layout_test.go

@@ -1,4 +1,4 @@
-package backend
+package layout
 
 import (
 	"context"
@@ -362,15 +362,15 @@ func TestDetectLayout(t *testing.T) {
 		filename string
 		want     string
 	}{
-		{"repo-layout-default.tar.gz", "*backend.DefaultLayout"},
+		{"repo-layout-default.tar.gz", "*layout.DefaultLayout"},
-		{"repo-layout-s3legacy.tar.gz", "*backend.S3LegacyLayout"},
+		{"repo-layout-s3legacy.tar.gz", "*layout.S3LegacyLayout"},
 	}
 
 	var fs = &LocalFilesystem{}
 	for _, test := range tests {
 		for _, fs := range []Filesystem{fs, nil} {
 			t.Run(fmt.Sprintf("%v/fs-%T", test.filename, fs), func(t *testing.T) {
-				rtest.SetupTarTestFixture(t, path, filepath.Join("testdata", test.filename))
+				rtest.SetupTarTestFixture(t, path, filepath.Join("../testdata", test.filename))
 
 				layout, err := DetectLayout(context.TODO(), fs, filepath.Join(path, "repo"))
 				if err != nil {
@@ -401,12 +401,12 @@ func TestParseLayout(t *testing.T) {
 		defaultLayoutName string
 		want              string
 	}{
-		{"default", "", "*backend.DefaultLayout"},
+		{"default", "", "*layout.DefaultLayout"},
-		{"s3legacy", "", "*backend.S3LegacyLayout"},
+		{"s3legacy", "", "*layout.S3LegacyLayout"},
-		{"", "", "*backend.DefaultLayout"},
+		{"", "", "*layout.DefaultLayout"},
 	}
 
-	rtest.SetupTarTestFixture(t, path, filepath.Join("testdata", "repo-layout-default.tar.gz"))
+	rtest.SetupTarTestFixture(t, path, filepath.Join("..", "testdata", "repo-layout-default.tar.gz"))
 
 	for _, test := range tests {
 		t.Run(test.layoutName, func(t *testing.T) {

internal/backend/local/local.go

@@ -10,6 +10,7 @@ import (
 	"syscall"
 
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -23,7 +24,7 @@ import (
 type Local struct {
 	Config
 	sem sema.Semaphore
-	backend.Layout
+	layout.Layout
 	backend.Modes
 }
 
@@ -33,7 +34,7 @@ var _ restic.Backend = &Local{}
 const defaultLayout = "default"
 
 func open(ctx context.Context, cfg Config) (*Local, error) {
-	l, err := backend.ParseLayout(ctx, &backend.LocalFilesystem{}, cfg.Layout, defaultLayout, cfg.Path)
+	l, err := layout.ParseLayout(ctx, &layout.LocalFilesystem{}, cfg.Layout, defaultLayout, cfg.Path)
 	if err != nil {
 		return nil, err
 	}

internal/backend/paths.go

@@ -2,25 +2,6 @@ package backend
 
 import "os"
 
-// Paths contains the default paths for file-based backends (e.g. local).
-var Paths = struct {
-	Data      string
-	Snapshots string
-	Index     string
-	Locks     string
-	Keys      string
-	Temp      string
-	Config    string
-}{
-	"data",
-	"snapshots",
-	"index",
-	"locks",
-	"keys",
-	"tmp",
-	"config",
-}
-
 type Modes struct {
 	Dir  os.FileMode
 	File os.FileMode

internal/backend/rest/rest.go

@@ -14,7 +14,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -32,7 +32,7 @@ type Backend struct {
 	connections uint
 	sem         sema.Semaphore
 	client      http.Client
-	backend.Layout
+	layout.Layout
 }
 
 // the REST API protocol version is decided by HTTP request headers, these are the constants.
@@ -57,7 +57,7 @@ func Open(cfg Config, rt http.RoundTripper) (*Backend, error) {
 	be := &Backend{
 		url:         cfg.URL,
 		client:      http.Client{Transport: rt},
-		Layout:      &backend.RESTLayout{URL: url, Join: path.Join},
+		Layout:      &layout.RESTLayout{URL: url, Join: path.Join},
 		connections: cfg.Connections,
 		sem:         sem,
 	}

internal/backend/retry/backend_retry.go

@@ -1,4 +1,4 @@
-package backend
+package retry
 
 import (
 	"context"
@@ -11,9 +11,9 @@ import (
 	"github.com/restic/restic/internal/restic"
 )
 
-// RetryBackend retries operations on the backend in case of an error with a
+// Backend retries operations on the backend in case of an error with a
 // backoff.
-type RetryBackend struct {
+type Backend struct {
 	restic.Backend
 	MaxTries int
 	Report   func(string, error, time.Duration)
@@ -21,14 +21,14 @@ type RetryBackend struct {
 }
 
 // statically ensure that RetryBackend implements restic.Backend.
-var _ restic.Backend = &RetryBackend{}
+var _ restic.Backend = &Backend{}
 
-// NewRetryBackend wraps be with a backend that retries operations after a
+// New wraps be with a backend that retries operations after a
 // backoff. report is called with a description and the error, if one occurred.
 // success is called with the number of retries before a successful operation
 // (it is not called if it succeeded on the first try)
-func NewRetryBackend(be restic.Backend, maxTries int, report func(string, error, time.Duration), success func(string, int)) *RetryBackend {
+func New(be restic.Backend, maxTries int, report func(string, error, time.Duration), success func(string, int)) *Backend {
-	return &RetryBackend{
+	return &Backend{
 		Backend:  be,
 		MaxTries: maxTries,
 		Report:   report,
@@ -57,7 +57,7 @@ func retryNotifyErrorWithSuccess(operation backoff.Operation, b backoff.BackOff,
 
 var fastRetries = false
 
-func (be *RetryBackend) retry(ctx context.Context, msg string, f func() error) error {
+func (be *Backend) retry(ctx context.Context, msg string, f func() error) error {
 	// Don't do anything when called with an already cancelled context. There would be
 	// no retries in that case either, so be consistent and abort always.
 	// This enforces a strict contract for backend methods: Using a cancelled context
@@ -92,7 +92,7 @@ func (be *RetryBackend) retry(ctx context.Context, msg string, f func() error) e
 }
 
 // Save stores the data in the backend under the given handle.
-func (be *RetryBackend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
+func (be *Backend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error {
 	return be.retry(ctx, fmt.Sprintf("Save(%v)", h), func() error {
 		err := rd.Rewind()
 		if err != nil {
@@ -125,7 +125,7 @@ func (be *RetryBackend) Save(ctx context.Context, h restic.Handle, rd restic.Rew
 // given offset. If length is larger than zero, only a portion of the file
 // is returned. rd must be closed after use. If an error is returned, the
 // ReadCloser must be nil.
-func (be *RetryBackend) Load(ctx context.Context, h restic.Handle, length int, offset int64, consumer func(rd io.Reader) error) (err error) {
+func (be *Backend) Load(ctx context.Context, h restic.Handle, length int, offset int64, consumer func(rd io.Reader) error) (err error) {
 	return be.retry(ctx, fmt.Sprintf("Load(%v, %v, %v)", h, length, offset),
 		func() error {
 			return be.Backend.Load(ctx, h, length, offset, consumer)
@@ -133,7 +133,7 @@ func (be *RetryBackend) Load(ctx context.Context, h restic.Handle, length int, o
 }
 
 // Stat returns information about the File identified by h.
-func (be *RetryBackend) Stat(ctx context.Context, h restic.Handle) (fi restic.FileInfo, err error) {
+func (be *Backend) Stat(ctx context.Context, h restic.Handle) (fi restic.FileInfo, err error) {
 	err = be.retry(ctx, fmt.Sprintf("Stat(%v)", h),
 		func() error {
 			var innerError error
@@ -145,14 +145,14 @@ func (be *RetryBackend) Stat(ctx context.Context, h restic.Handle) (fi restic.Fi
 }
 
 // Remove removes a File with type t and name.
-func (be *RetryBackend) Remove(ctx context.Context, h restic.Handle) (err error) {
+func (be *Backend) Remove(ctx context.Context, h restic.Handle) (err error) {
 	return be.retry(ctx, fmt.Sprintf("Remove(%v)", h), func() error {
 		return be.Backend.Remove(ctx, h)
 	})
 }
 
 // Test a boolean value whether a File with the name and type exists.
-func (be *RetryBackend) Test(ctx context.Context, h restic.Handle) (exists bool, err error) {
+func (be *Backend) Test(ctx context.Context, h restic.Handle) (exists bool, err error) {
 	err = be.retry(ctx, fmt.Sprintf("Test(%v)", h), func() error {
 		var innerError error
 		exists, innerError = be.Backend.Test(ctx, h)
@@ -166,7 +166,7 @@ func (be *RetryBackend) Test(ctx context.Context, h restic.Handle) (exists bool,
 // error is returned by the underlying backend, the request is retried. When fn
 // returns an error, the operation is aborted and the error is returned to the
 // caller.
-func (be *RetryBackend) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
+func (be *Backend) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
 	// create a new context that we can cancel when fn returns an error, so
 	// that listing is aborted
 	listCtx, cancel := context.WithCancel(ctx)

internal/backend/retry/backend_retry_test.go

@@ -1,4 +1,4 @@
-package backend
+package retry
 
 import (
 	"bytes"
@@ -36,7 +36,7 @@ func TestBackendSaveRetry(t *testing.T) {
 	}
 
 	TestFastRetries(t)
-	retryBackend := NewRetryBackend(be, 10, nil, nil)
+	retryBackend := New(be, 10, nil, nil)
 
 	data := test.Random(23, 5*1024*1024+11241)
 	err := retryBackend.Save(context.TODO(), restic.Handle{}, restic.NewByteReader(data, be.Hasher()))
@@ -72,7 +72,7 @@ func TestBackendSaveRetryAtomic(t *testing.T) {
 	}
 
 	TestFastRetries(t)
-	retryBackend := NewRetryBackend(be, 10, nil, nil)
+	retryBackend := New(be, 10, nil, nil)
 
 	data := test.Random(23, 5*1024*1024+11241)
 	err := retryBackend.Save(context.TODO(), restic.Handle{}, restic.NewByteReader(data, be.Hasher()))
@@ -106,7 +106,7 @@ func TestBackendListRetry(t *testing.T) {
 	}
 
 	TestFastRetries(t)
-	retryBackend := NewRetryBackend(be, 10, nil, nil)
+	retryBackend := New(be, 10, nil, nil)
 
 	var listed []string
 	err := retryBackend.List(context.TODO(), restic.PackFile, func(fi restic.FileInfo) error {
@@ -136,7 +136,7 @@ func TestBackendListRetryErrorFn(t *testing.T) {
 	}
 
 	TestFastRetries(t)
-	retryBackend := NewRetryBackend(be, 10, nil, nil)
+	retryBackend := New(be, 10, nil, nil)
 
 	var ErrTest = errors.New("test error")
 
@@ -193,7 +193,7 @@ func TestBackendListRetryErrorBackend(t *testing.T) {
 
 	TestFastRetries(t)
 	const maxRetries = 2
-	retryBackend := NewRetryBackend(be, maxRetries, nil, nil)
+	retryBackend := New(be, maxRetries, nil, nil)
 
 	var listed []string
 	err := retryBackend.List(context.TODO(), restic.PackFile, func(fi restic.FileInfo) error {
@@ -263,7 +263,7 @@ func TestBackendLoadRetry(t *testing.T) {
 	}
 
 	TestFastRetries(t)
-	retryBackend := NewRetryBackend(be, 10, nil, nil)
+	retryBackend := New(be, 10, nil, nil)
 
 	var buf []byte
 	err := retryBackend.Load(context.TODO(), restic.Handle{}, 0, 0, func(rd io.Reader) (err error) {
@@ -283,7 +283,7 @@ func TestBackendCanceledContext(t *testing.T) {
 	// unimplemented mock backend functions return an error by default
 	// check that we received the expected context canceled error instead
 	TestFastRetries(t)
-	retryBackend := NewRetryBackend(mock.NewBackend(), 2, nil, nil)
+	retryBackend := New(mock.NewBackend(), 2, nil, nil)
 	h := restic.Handle{Type: restic.PackFile, Name: restic.NewRandomID().String()}
 
 	// create an already canceled context

internal/backend/retry/testing.go

@@ -1,4 +1,4 @@
-package backend
+package retry
 
 import "testing"
 

internal/backend/s3/s3.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -28,7 +29,7 @@ type Backend struct {
 	client *minio.Client
 	sem    sema.Semaphore
 	cfg    Config
-	backend.Layout
+	layout.Layout
 }
 
 // make sure that *Backend implements backend.Backend
@@ -113,7 +114,7 @@ func open(ctx context.Context, cfg Config, rt http.RoundTripper) (*Backend, erro
 		cfg:    cfg,
 	}
 
-	l, err := backend.ParseLayout(ctx, be, cfg.Layout, defaultLayout, cfg.Prefix)
+	l, err := layout.ParseLayout(ctx, be, cfg.Layout, defaultLayout, cfg.Prefix)
 	if err != nil {
 		return nil, err
 	}
@@ -514,7 +515,7 @@ func (be *Backend) Delete(ctx context.Context) error {
 func (be *Backend) Close() error { return nil }
 
 // Rename moves a file based on the new layout l.
-func (be *Backend) Rename(ctx context.Context, h restic.Handle, l backend.Layout) error {
+func (be *Backend) Rename(ctx context.Context, h restic.Handle, l layout.Layout) error {
 	debug.Log("Rename %v to %v", h, l)
 	oldname := be.Filename(h)
 	newname := l.Filename(h)

internal/backend/sftp/sftp.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -35,7 +36,7 @@ type SFTP struct {
 	posixRename bool
 
 	sem sema.Semaphore
-	backend.Layout
+	layout.Layout
 	Config
 	backend.Modes
 }
@@ -144,14 +145,14 @@ func open(ctx context.Context, sftp *SFTP, cfg Config) (*SFTP, error) {
 		return nil, err
 	}
 
-	sftp.Layout, err = backend.ParseLayout(ctx, sftp, cfg.Layout, defaultLayout, cfg.Path)
+	sftp.Layout, err = layout.ParseLayout(ctx, sftp, cfg.Layout, defaultLayout, cfg.Path)
 	if err != nil {
 		return nil, err
 	}
 
 	debug.Log("layout: %v\n", sftp.Layout)
 
-	fi, err := sftp.c.Stat(Join(cfg.Path, backend.Paths.Config))
+	fi, err := sftp.c.Stat(sftp.Layout.Filename(restic.Handle{Type: restic.ConfigFile}))
 	m := backend.DeriveModesFromFileInfo(fi, err)
 	debug.Log("using (%03O file, %03O dir) permissions", m.File, m.Dir)
 
@@ -243,7 +244,7 @@ func Create(ctx context.Context, cfg Config) (*SFTP, error) {
 		return nil, err
 	}
 
-	sftp.Layout, err = backend.ParseLayout(ctx, sftp, cfg.Layout, defaultLayout, cfg.Path)
+	sftp.Layout, err = layout.ParseLayout(ctx, sftp, cfg.Layout, defaultLayout, cfg.Path)
 	if err != nil {
 		return nil, err
 	}
@@ -251,7 +252,7 @@ func Create(ctx context.Context, cfg Config) (*SFTP, error) {
 	sftp.Modes = backend.DefaultModes
 
 	// test if config file already exists
-	_, err = sftp.c.Lstat(Join(cfg.Path, backend.Paths.Config))
+	_, err = sftp.c.Lstat(sftp.Layout.Filename(restic.Handle{Type: restic.ConfigFile}))
 	if err == nil {
 		return nil, errors.New("config file already exists")
 	}

internal/backend/swift/swift.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/sema"
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/errors"
@@ -30,7 +31,7 @@ type beSwift struct {
 	sem         sema.Semaphore
 	container   string // Container name
 	prefix      string // Prefix of object names in the container
-	backend.Layout
+	layout.Layout
 }
 
 // ensure statically that *beSwift implements restic.Backend.
@@ -74,7 +75,7 @@ func Open(ctx context.Context, cfg Config, rt http.RoundTripper) (restic.Backend
 		sem:         sem,
 		container:   cfg.Container,
 		prefix:      cfg.Prefix,
-		Layout: &backend.DefaultLayout{
+		Layout: &layout.DefaultLayout{
 			Path: cfg.Prefix,
 			Join: path.Join,
 		},

internal/migrations/s3_layout.go

@@ -6,7 +6,7 @@ import (
 	"os"
 	"path"
 
-	"github.com/restic/restic/internal/backend"
+	"github.com/restic/restic/internal/backend/layout"
 	"github.com/restic/restic/internal/backend/s3"
 	"github.com/restic/restic/internal/cache"
 	"github.com/restic/restic/internal/debug"
@@ -74,7 +74,7 @@ func retry(max int, fail func(err error), f func() error) error {
 // maxErrors for retrying renames on s3.
 const maxErrors = 20
 
-func (m *S3Layout) moveFiles(ctx context.Context, be *s3.Backend, l backend.Layout, t restic.FileType) error {
+func (m *S3Layout) moveFiles(ctx context.Context, be *s3.Backend, l layout.Layout, t restic.FileType) error {
 	printErr := func(err error) {
 		fmt.Fprintf(os.Stderr, "renaming file returned error: %v\n", err)
 	}
@@ -97,12 +97,12 @@ func (m *S3Layout) Apply(ctx context.Context, repo restic.Repository) error {
 		return errors.New("backend is not s3")
 	}
 
-	oldLayout := &backend.S3LegacyLayout{
+	oldLayout := &layout.S3LegacyLayout{
 		Path: be.Path(),
 		Join: path.Join,
 	}
 
-	newLayout := &backend.DefaultLayout{
+	newLayout := &layout.DefaultLayout{
 		Path: be.Path(),
 		Join: path.Join,
 	}