Fix calls to repo/backend.List() everywhere

cmd/restic/cmd_debug.go

@@ -15,8 +15,6 @@ import (
 	"github.com/restic/restic/internal/pack"
 	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
-
-	"github.com/restic/restic/internal/worker"
 )
 
 var cmdDebug = &cobra.Command{
@@ -52,25 +50,17 @@ func prettyPrintJSON(wr io.Writer, item interface{}) error {
 }
 
 func debugPrintSnapshots(repo *repository.Repository, wr io.Writer) error {
-	for id := range repo.List(context.TODO(), restic.SnapshotFile) {
+	return repo.List(context.TODO(), restic.SnapshotFile, func(id restic.ID, size int64) error {
 		snapshot, err := restic.LoadSnapshot(context.TODO(), repo, id)
 		if err != nil {
-			fmt.Fprintf(os.Stderr, "LoadSnapshot(%v): %v", id.Str(), err)
+			return err
-			continue
 		}
 
 		fmt.Fprintf(wr, "snapshot_id: %v\n", id)
 
-		err = prettyPrintJSON(wr, snapshot)
+		return prettyPrintJSON(wr, snapshot)
-		if err != nil {
+	})
-			return err
 }
-	}
-
-	return nil
-}
-
-const dumpPackWorkers = 10
 
 // Pack is the struct used in printPacks.
 type Pack struct {
@@ -88,49 +78,21 @@ type Blob struct {
 }
 
 func printPacks(repo *repository.Repository, wr io.Writer) error {
-	f := func(ctx context.Context, job worker.Job) (interface{}, error) {
-		name := job.Data.(string)
 
-		h := restic.Handle{Type: restic.DataFile, Name: name}
+	return repo.List(context.TODO(), restic.DataFile, func(id restic.ID, size int64) error {
+		h := restic.Handle{Type: restic.DataFile, Name: id.String()}
 
-		blobInfo, err := repo.Backend().Stat(ctx, h)
+		blobs, err := pack.List(repo.Key(), restic.ReaderAt(repo.Backend(), h), size)
 		if err != nil {
-			return nil, err
+			fmt.Fprintf(os.Stderr, "error for pack %v: %v\n", id.Str(), err)
+			return nil
 		}
 
-		blobs, err := pack.List(repo.Key(), restic.ReaderAt(repo.Backend(), h), blobInfo.Size)
-		if err != nil {
-			return nil, err
-		}
-
-		return blobs, nil
-	}
-
-	jobCh := make(chan worker.Job)
-	resCh := make(chan worker.Job)
-	wp := worker.New(context.TODO(), dumpPackWorkers, f, jobCh, resCh)
-
-	go func() {
-		for name := range repo.Backend().List(context.TODO(), restic.DataFile) {
-			jobCh <- worker.Job{Data: name}
-		}
-		close(jobCh)
-	}()
-
-	for job := range resCh {
-		name := job.Data.(string)
-
-		if job.Error != nil {
-			fmt.Fprintf(os.Stderr, "error for pack %v: %v\n", name, job.Error)
-			continue
-		}
-
-		entries := job.Result.([]restic.Blob)
 		p := Pack{
-			Name:  name,
+			Name:  id.String(),
-			Blobs: make([]Blob, len(entries)),
+			Blobs: make([]Blob, len(blobs)),
 		}
-		for i, blob := range entries {
+		for i, blob := range blobs {
 			p.Blobs[i] = Blob{
 				Type:   blob.Type,
 				Length: blob.Length,
@@ -139,16 +101,14 @@ func printPacks(repo *repository.Repository, wr io.Writer) error {
 			}
 		}
 
-		prettyPrintJSON(os.Stdout, p)
+		return prettyPrintJSON(os.Stdout, p)
-	}
+	})
-
-	wp.Wait()
 
 	return nil
 }
 
 func dumpIndexes(repo restic.Repository) error {
-	for id := range repo.List(context.TODO(), restic.IndexFile) {
+	return repo.List(context.TODO(), restic.IndexFile, func(id restic.ID, size int64) error {
 		fmt.Printf("index_id: %v\n", id)
 
 		idx, err := repository.LoadIndex(context.TODO(), repo, id)
@@ -156,13 +116,8 @@ func dumpIndexes(repo restic.Repository) error {
 			return err
 		}
 
-		err = idx.Dump(os.Stdout)
+		return idx.Dump(os.Stdout)
-		if err != nil {
+	})
-			return err
-		}
-	}
-
-	return nil
 }
 
 func runDebugDump(gopts GlobalOptions, args []string) error {

cmd/restic/cmd_key.go

@@ -32,11 +32,11 @@ func listKeys(ctx context.Context, s *repository.Repository) error {
 	tab.Header = fmt.Sprintf(" %-10s  %-10s  %-10s  %s", "ID", "User", "Host", "Created")
 	tab.RowFormat = "%s%-10s  %-10s  %-10s  %s"
 
-	for id := range s.List(ctx, restic.KeyFile) {
+	err := s.List(ctx, restic.KeyFile, func(id restic.ID, size int64) error {
 		k, err := repository.LoadKey(ctx, s, id.String())
 		if err != nil {
 			Warnf("LoadKey() failed: %v\n", err)
-			continue
+			return nil
 		}
 
 		var current string
@@ -47,6 +47,10 @@ func listKeys(ctx context.Context, s *repository.Repository) error {
 		}
 		tab.Rows = append(tab.Rows, []interface{}{current, id.Str(),
 			k.Username, k.Hostname, k.Created.Format(TimeFormat)})
+		return nil
+	})
+	if err != nil {
+		return err
 	}
 
 	return tab.Write(globalOptions.stdout)

cmd/restic/cmd_list.go

@@ -73,9 +73,8 @@ func runList(opts GlobalOptions, args []string) error {
 		return errors.Fatal("invalid type")
 	}
 
-	for id := range repo.List(opts.ctx, t) {
+	return repo.List(opts.ctx, t, func(id restic.ID, size int64) error {
 		Printf("%s\n", id)
-	}
-
 		return nil
+	})
 }

cmd/restic/cmd_prune.go

@@ -120,8 +120,12 @@ func pruneRepository(gopts GlobalOptions, repo restic.Repository) error {
 	}
 
 	Verbosef("counting files in repo\n")
-	for range repo.List(ctx, restic.DataFile) {
+	err = repo.List(ctx, restic.DataFile, func(restic.ID, int64) error {
 		stats.packs++
+		return nil
+	})
+	if err != nil {
+		return err
 	}
 
 	Verbosef("building new index for repo\n")

cmd/restic/cmd_rebuild_index.go

@@ -48,8 +48,12 @@ func rebuildIndex(ctx context.Context, repo restic.Repository, ignorePacks resti
 	Verbosef("counting files in repo\n")
 
 	var packs uint64
-	for range repo.List(ctx, restic.DataFile) {
+	err := repo.List(ctx, restic.DataFile, func(restic.ID, int64) error {
 		packs++
+		return nil
+	})
+	if err != nil {
+		return err
 	}
 
 	bar := newProgressMax(!globalOptions.Quiet, packs-uint64(len(ignorePacks)), "packs")
@@ -61,8 +65,12 @@ func rebuildIndex(ctx context.Context, repo restic.Repository, ignorePacks resti
 	Verbosef("finding old index files\n")
 
 	var supersedes restic.IDs
-	for id := range repo.List(ctx, restic.IndexFile) {
+	err = repo.List(ctx, restic.IndexFile, func(id restic.ID, size int64) error {
 		supersedes = append(supersedes, id)
+		return nil
+	})
+	if err != nil {
+		return err
 	}
 
 	id, err := idx.Save(ctx, repo, supersedes)

cmd/restic/find.go

@@ -58,7 +58,13 @@ func FindFilteredSnapshots(ctx context.Context, repo *repository.Repository, hos
 			return
 		}
 
-		for _, sn := range restic.FindFilteredSnapshots(ctx, repo, host, tags, paths) {
+		snapshots, err := restic.FindFilteredSnapshots(ctx, repo, host, tags, paths)
+		if err != nil {
+			Warnf("could not load snapshots: %v\n", err)
+			return
+		}
+
+		for _, sn := range snapshots {
 			select {
 			case <-ctx.Done():
 				return

internal/archiver/archive_reader_test.go

@@ -135,8 +135,12 @@ func (e errReader) Read([]byte) (int, error) {
 
 func countSnapshots(t testing.TB, repo restic.Repository) int {
 	snapshots := 0
-	for range repo.List(context.TODO(), restic.SnapshotFile) {
+	err := repo.List(context.TODO(), restic.SnapshotFile, func(id restic.ID, size int64) error {
 		snapshots++
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
 	}
 	return snapshots
 }

internal/archiver/archiver_duplication_test.go

@@ -60,10 +60,8 @@ func forgetfulBackend() restic.Backend {
 		return nil
 	}
 
-	be.ListFn = func(ctx context.Context, t restic.FileType) <-chan string {
+	be.ListFn = func(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
-		ch := make(chan string)
+		return nil
-		close(ch)
-		return ch
 	}
 
 	be.DeleteFn = func(ctx context.Context) error {

internal/archiver/archiver_test.go

@@ -131,9 +131,13 @@ func BenchmarkArchiveDirectory(b *testing.B) {
 	}
 }
 
-func countPacks(repo restic.Repository, t restic.FileType) (n uint) {
+func countPacks(t testing.TB, repo restic.Repository, tpe restic.FileType) (n uint) {
-	for range repo.Backend().List(context.TODO(), t) {
+	err := repo.Backend().List(context.TODO(), tpe, func(restic.FileInfo) error {
 		n++
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
 	}
 
 	return n
@@ -158,7 +162,7 @@ func archiveWithDedup(t testing.TB) {
 	t.Logf("archived snapshot %v", sn.ID().Str())
 
 	// get archive stats
-	cnt.before.packs = countPacks(repo, restic.DataFile)
+	cnt.before.packs = countPacks(t, repo, restic.DataFile)
 	cnt.before.dataBlobs = repo.Index().Count(restic.DataBlob)
 	cnt.before.treeBlobs = repo.Index().Count(restic.TreeBlob)
 	t.Logf("packs %v, data blobs %v, tree blobs %v",
@@ -169,7 +173,7 @@ func archiveWithDedup(t testing.TB) {
 	t.Logf("archived snapshot %v", sn2.ID().Str())
 
 	// get archive stats again
-	cnt.after.packs = countPacks(repo, restic.DataFile)
+	cnt.after.packs = countPacks(t, repo, restic.DataFile)
 	cnt.after.dataBlobs = repo.Index().Count(restic.DataBlob)
 	cnt.after.treeBlobs = repo.Index().Count(restic.TreeBlob)
 	t.Logf("packs %v, data blobs %v, tree blobs %v",
@@ -186,7 +190,7 @@ func archiveWithDedup(t testing.TB) {
 	t.Logf("archived snapshot %v, parent %v", sn3.ID().Str(), sn2.ID().Str())
 
 	// get archive stats again
-	cnt.after2.packs = countPacks(repo, restic.DataFile)
+	cnt.after2.packs = countPacks(t, repo, restic.DataFile)
 	cnt.after2.dataBlobs = repo.Index().Count(restic.DataBlob)
 	cnt.after2.treeBlobs = repo.Index().Count(restic.TreeBlob)
 	t.Logf("packs %v, data blobs %v, tree blobs %v",

internal/backend/mem/mem_backend.go

@@ -164,17 +164,22 @@ func (be *MemoryBackend) Remove(ctx context.Context, h restic.Handle) error {
 
 // List returns a channel which yields entries from the backend.
 func (be *MemoryBackend) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
-	be.m.Lock()
+	entries := make(map[string]int64)
-	defer be.m.Unlock()
 
+	be.m.Lock()
 	for entry, buf := range be.data {
 		if entry.Type != t {
 			continue
 		}
 
+		entries[entry.Name] = int64(len(buf))
+	}
+	be.m.Unlock()
+
+	for name, size := range entries {
 		fi := restic.FileInfo{
-			Name: entry.Name,
+			Name: name,
-			Size: int64(len(buf)),
+			Size: size,
 		}
 
 		if ctx.Err() != nil {

internal/checker/checker.go

@@ -12,6 +12,7 @@ import (
 	"github.com/restic/restic/internal/fs"
 	"github.com/restic/restic/internal/hashing"
 	"github.com/restic/restic/internal/restic"
+	"golang.org/x/sync/errgroup"
 
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/pack"
@@ -192,13 +193,14 @@ func (c *Checker) Packs(ctx context.Context, errChan chan<- error) {
 
 	debug.Log("listing repository packs")
 	repoPacks := restic.NewIDSet()
-	for id := range c.repo.List(ctx, restic.DataFile) {
+
-		select {
+	err := c.repo.List(ctx, restic.DataFile, func(id restic.ID, size int64) error {
-		case <-ctx.Done():
-			return
-		default:
-		}
 		repoPacks.Insert(id)
+		return nil
+	})
+
+	if err != nil {
+		errChan <- err
 	}
 
 	// orphaned: present in the repo but not in c.packs
@@ -719,18 +721,34 @@ func (c *Checker) ReadData(ctx context.Context, p *restic.Progress, errChan chan
 	p.Start()
 	defer p.Done()
 
-	worker := func(wg *sync.WaitGroup, in <-chan restic.ID) {
+	g, ctx := errgroup.WithContext(ctx)
-		defer wg.Done()
+	ch := make(chan restic.ID)
+
+	// start producer for channel ch
+	g.Go(func() error {
+		defer close(ch)
+		return c.repo.List(ctx, restic.DataFile, func(id restic.ID, size int64) error {
+			select {
+			case <-ctx.Done():
+			case ch <- id:
+			}
+			return nil
+		})
+	})
+
+	// run workers
+	for i := 0; i < defaultParallelism; i++ {
+		g.Go(func() error {
 			for {
 				var id restic.ID
 				var ok bool
 
 				select {
 				case <-ctx.Done():
-				return
+					return nil
-			case id, ok = <-in:
+				case id, ok = <-ch:
 					if !ok {
-					return
+						return nil
 					}
 				}
 
@@ -740,6 +758,17 @@ func (c *Checker) ReadData(ctx context.Context, p *restic.Progress, errChan chan
 					continue
 				}
 
+				select {
+				case <-ctx.Done():
+					return nil
+				case errChan <- err:
+				}
+			}
+		})
+	}
+
+	err := g.Wait()
+	if err != nil {
 		select {
 		case <-ctx.Done():
 			return
@@ -747,14 +776,3 @@ func (c *Checker) ReadData(ctx context.Context, p *restic.Progress, errChan chan
 		}
 	}
 }
-
-	ch := c.repo.List(ctx, restic.DataFile)
-
-	var wg sync.WaitGroup
-	for i := 0; i < defaultParallelism; i++ {
-		wg.Add(1)
-		go worker(&wg, ch)
-	}
-
-	wg.Wait()
-}

internal/fuse/file_test.go

@@ -35,11 +35,17 @@ func testRead(t testing.TB, f *file, offset, length int, data []byte) {
 }
 
 func firstSnapshotID(t testing.TB, repo restic.Repository) (first restic.ID) {
-	for id := range repo.List(context.TODO(), restic.SnapshotFile) {
+	err := repo.List(context.TODO(), restic.SnapshotFile, func(id restic.ID, size int64) error {
 		if first.IsNull() {
 			first = id
 		}
+		return nil
+	})
+
+	if err != nil {
+		t.Fatal(err)
 	}
+
 	return first
 }
 

internal/fuse/snapshots_dir.go

@@ -227,18 +227,24 @@ func isElem(e string, list []string) bool {
 const minSnapshotsReloadTime = 60 * time.Second
 
 // update snapshots if repository has changed
-func updateSnapshots(ctx context.Context, root *Root) {
+func updateSnapshots(ctx context.Context, root *Root) error {
 	if time.Since(root.lastCheck) < minSnapshotsReloadTime {
-		return
+		return nil
+	}
+
+	snapshots, err := restic.FindFilteredSnapshots(ctx, root.repo, root.cfg.Host, root.cfg.Tags, root.cfg.Paths)
+	if err != nil {
+		return err
 	}
 
-	snapshots := restic.FindFilteredSnapshots(ctx, root.repo, root.cfg.Host, root.cfg.Tags, root.cfg.Paths)
 	if root.snCount != len(snapshots) {
 		root.snCount = len(snapshots)
 		root.repo.LoadIndex(ctx)
 		root.snapshots = snapshots
 	}
 	root.lastCheck = time.Now()
+
+	return nil
 }
 
 // read snapshot timestamps from the current repository-state.

internal/index/index.go

@@ -115,13 +115,13 @@ func Load(ctx context.Context, repo restic.Repository, p *restic.Progress) (*Ind
 
 	index := newIndex()
 
-	for id := range repo.List(ctx, restic.IndexFile) {
+	err := repo.List(ctx, restic.IndexFile, func(id restic.ID, size int64) error {
 		p.Report(restic.Stat{Blobs: 1})
 
 		debug.Log("Load index %v", id.Str())
 		idx, err := loadIndexJSON(ctx, repo, id)
 		if err != nil {
-			return nil, err
+			return err
 		}
 
 		res := make(map[restic.ID]Pack)
@@ -144,12 +144,18 @@ func Load(ctx context.Context, repo restic.Repository, p *restic.Progress) (*Ind
 			}
 
 			if err = index.AddPack(jpack.ID, 0, entries); err != nil {
-				return nil, err
+				return err
 			}
 		}
 
 		results[id] = res
 		index.IndexIDs.Insert(id)
+
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
 	}
 
 	for superID, list := range supersedes {

internal/index/index_test.go

@@ -28,7 +28,7 @@ func createFilledRepo(t testing.TB, snapshots int, dup float32) (restic.Reposito
 }
 
 func validateIndex(t testing.TB, repo restic.Repository, idx *Index) {
-	for id := range repo.List(context.TODO(), restic.DataFile) {
+	err := repo.List(context.TODO(), restic.DataFile, func(id restic.ID, size int64) error {
 		p, ok := idx.Packs[id]
 		if !ok {
 			t.Errorf("pack %v missing from index", id.Str())
@@ -37,6 +37,11 @@ func validateIndex(t testing.TB, repo restic.Repository, idx *Index) {
 		if !p.ID.Equal(id) {
 			t.Errorf("pack %v has invalid ID: want %v, got %v", id.Str(), id, p.ID)
 		}
+		return nil
+	})
+
+	if err != nil {
+		t.Fatal(err)
 	}
 }
 
@@ -308,7 +313,14 @@ func TestIndexAddRemovePack(t *testing.T) {
 		t.Fatalf("Load() returned error %v", err)
 	}
 
-	packID := <-repo.List(context.TODO(), restic.DataFile)
+	var packID restic.ID
+	err = repo.List(context.TODO(), restic.DataFile, func(id restic.ID, size int64) error {
+		packID = id
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	t.Logf("selected pack %v", packID.Str())
 

internal/list/list.go

@@ -11,7 +11,7 @@ const listPackWorkers = 10
 
 // Lister combines lists packs in a repo and blobs in a pack.
 type Lister interface {
-	List(context.Context, restic.FileType) <-chan restic.ID
+	List(context.Context, restic.FileType, func(restic.ID, int64) error) error
 	ListPack(context.Context, restic.ID) ([]restic.Blob, int64, error)
 }
 
@@ -55,17 +55,19 @@ func AllPacks(ctx context.Context, repo Lister, ignorePacks restic.IDSet, ch cha
 
 	go func() {
 		defer close(jobCh)
-		for id := range repo.List(ctx, restic.DataFile) {
+
+		_ = repo.List(ctx, restic.DataFile, func(id restic.ID, size int64) error {
 			if ignorePacks.Has(id) {
-				continue
+				return nil
 			}
 
 			select {
 			case jobCh <- worker.Job{Data: id}:
 			case <-ctx.Done():
-				return
+				return ctx.Err()
-			}
 			}
+			return nil
+		})
 	}()
 
 	wp.Wait()

internal/migrations/s3_layout.go

@@ -59,14 +59,14 @@ func (m *S3Layout) moveFiles(ctx context.Context, be *s3.Backend, l backend.Layo
 		fmt.Fprintf(os.Stderr, "renaming file returned error: %v\n", err)
 	}
 
-	for name := range be.List(ctx, t) {
+	return be.List(ctx, t, func(fi restic.FileInfo) error {
-		h := restic.Handle{Type: t, Name: name}
+		h := restic.Handle{Type: t, Name: fi.Name}
 		debug.Log("move %v", h)
 
-		retry(maxErrors, printErr, func() error {
+		return retry(maxErrors, printErr, func() error {
 			return be.Rename(h, l)
 		})
-	}
+	})
 
 	return nil
 }

internal/repository/key.go

@@ -113,44 +113,50 @@ func OpenKey(ctx context.Context, s *Repository, name string, password string) (
 // given password. If none could be found, ErrNoKeyFound is returned. When
 // maxKeys is reached, ErrMaxKeysReached is returned. When setting maxKeys to
 // zero, all keys in the repo are checked.
-func SearchKey(ctx context.Context, s *Repository, password string, maxKeys int) (*Key, error) {
+func SearchKey(ctx context.Context, s *Repository, password string, maxKeys int) (k *Key, err error) {
 	checked := 0
 
 	// try at most maxKeysForSearch keys in repo
-	for name := range s.Backend().List(ctx, restic.KeyFile) {
+	err = s.Backend().List(ctx, restic.KeyFile, func(fi restic.FileInfo) error {
 		if maxKeys > 0 && checked > maxKeys {
-			return nil, ErrMaxKeysReached
+			return ErrMaxKeysReached
 		}
 
-		_, err := restic.ParseID(name)
+		_, err := restic.ParseID(fi.Name)
 		if err != nil {
-			debug.Log("rejecting key with invalid name: %v", name)
+			debug.Log("rejecting key with invalid name: %v", fi.Name)
-			continue
+			return nil
 		}
 
-		debug.Log("trying key %q", name)
+		debug.Log("trying key %q", fi.Name)
-		key, err := OpenKey(ctx, s, name, password)
+		key, err := OpenKey(ctx, s, fi.Name, password)
 		if err != nil {
-			debug.Log("key %v returned error %v", name, err)
+			debug.Log("key %v returned error %v", fi.Name, err)
 
 			// ErrUnauthenticated means the password is wrong, try the next key
 			if errors.Cause(err) == crypto.ErrUnauthenticated {
-				continue
+				return nil
 			}
 
+			return err
+		}
+
+		debug.Log("successfully opened key %v", fi.Name)
+		k = key
+		return nil
+	})
+
 	if err != nil {
-				debug.Log("unable to open key %v: %v\n", err)
+		return nil, err
-				continue
-			}
-		}
-
-		debug.Log("successfully opened key %v", name)
-		return key, nil
 	}
 
+	if k == nil {
 		return nil, ErrNoKeyFound
 	}
 
+	return k, nil
+}
+
 // LoadKey loads a key from the backend.
 func LoadKey(ctx context.Context, s *Repository, name string) (k *Key, err error) {
 	h := restic.Handle{Type: restic.KeyFile, Name: name}

internal/repository/parallel.go

@@ -2,10 +2,10 @@ package repository
 
 import (
 	"context"
-	"sync"
 
 	"github.com/restic/restic/internal/debug"
 	"github.com/restic/restic/internal/restic"
+	"golang.org/x/sync/errgroup"
 )
 
 // ParallelWorkFunc gets one file ID to work on. If an error is returned,
@@ -17,47 +17,36 @@ type ParallelWorkFunc func(ctx context.Context, id string) error
 type ParallelIDWorkFunc func(ctx context.Context, id restic.ID) error
 
 // FilesInParallel runs n workers of f in parallel, on the IDs that
-// repo.List(t) yield. If f returns an error, the process is aborted and the
+// repo.List(t) yields. If f returns an error, the process is aborted and the
 // first error is returned.
-func FilesInParallel(ctx context.Context, repo restic.Lister, t restic.FileType, n uint, f ParallelWorkFunc) error {
+func FilesInParallel(ctx context.Context, repo restic.Lister, t restic.FileType, n int, f ParallelWorkFunc) error {
-	wg := &sync.WaitGroup{}
+	g, ctx := errgroup.WithContext(ctx)
-	ch := repo.List(ctx, t)
-	errors := make(chan error, n)
 
-	for i := 0; uint(i) < n; i++ {
+	ch := make(chan string, n)
-		wg.Add(1)
+	g.Go(func() error {
-		go func() {
+		defer close(ch)
-			defer wg.Done()
+		return repo.List(ctx, t, func(fi restic.FileInfo) error {
-
-			for {
 			select {
-				case id, ok := <-ch:
-					if !ok {
-						return
-					}
-
-					err := f(ctx, id)
-					if err != nil {
-						errors <- err
-						return
-					}
 			case <-ctx.Done():
-					return
+			case ch <- fi.Name:
 			}
-			}
-		}()
-	}
-
-	wg.Wait()
-
-	select {
-	case err := <-errors:
-		return err
-	default:
-		break
-	}
-
 			return nil
+		})
+	})
+
+	for i := 0; i < n; i++ {
+		g.Go(func() error {
+			for name := range ch {
+				err := f(ctx, name)
+				if err != nil {
+					return err
+				}
+			}
+			return nil
+		})
+	}
+
+	return g.Wait()
 }
 
 // ParallelWorkFuncParseID converts a function that takes a restic.ID to a

internal/repository/parallel_test.go

@@ -74,24 +74,25 @@ var lister = testIDs{
 	"34dd044c228727f2226a0c9c06a3e5ceb5e30e31cb7854f8fa1cde846b395a58",
 }
 
-func (tests testIDs) List(ctx context.Context, t restic.FileType) <-chan string {
+func (tests testIDs) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error {
-	ch := make(chan string)
-
-	go func() {
-		defer close(ch)
-
 	for i := 0; i < 500; i++ {
 		for _, id := range tests {
-				select {
+			if ctx.Err() != nil {
-				case ch <- id:
+				return ctx.Err()
-				case <-ctx.Done():
-					return
 			}
-			}
-		}
-	}()
 
-	return ch
+			fi := restic.FileInfo{
+				Name: id,
+			}
+
+			err := fn(fi)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
 }
 
 func TestFilesInParallel(t *testing.T) {
@@ -100,7 +101,7 @@ func TestFilesInParallel(t *testing.T) {
 		return nil
 	}
 
-	for n := uint(1); n < 5; n++ {
+	for n := 1; n < 5; n++ {
 		err := repository.FilesInParallel(context.TODO(), lister, restic.DataFile, n*100, f)
 		rtest.OK(t, err)
 	}
@@ -109,7 +110,6 @@ func TestFilesInParallel(t *testing.T) {
 var errTest = errors.New("test error")
 
 func TestFilesInParallelWithError(t *testing.T) {
-
 	f := func(ctx context.Context, id string) error {
 		time.Sleep(1 * time.Millisecond)
 
@@ -120,8 +120,10 @@ func TestFilesInParallelWithError(t *testing.T) {
 		return nil
 	}
 
-	for n := uint(1); n < 5; n++ {
+	for n := 1; n < 5; n++ {
 		err := repository.FilesInParallel(context.TODO(), lister, restic.DataFile, n*100, f)
-		rtest.Equals(t, errTest, err)
+		if err != errTest {
+			t.Fatalf("wrong error returned, want %q, got %v", errTest, err)
+		}
 	}
 }

internal/repository/repack_test.go

@@ -74,7 +74,7 @@ func selectBlobs(t *testing.T, repo restic.Repository, p float32) (list1, list2
 
 	blobs := restic.NewBlobSet()
 
-	for id := range repo.List(context.TODO(), restic.DataFile) {
+	err := repo.List(context.TODO(), restic.DataFile, func(id restic.ID, size int64) error {
 		entries, _, err := repo.ListPack(context.TODO(), id)
 		if err != nil {
 			t.Fatalf("error listing pack %v: %v", id, err)
@@ -84,7 +84,7 @@ func selectBlobs(t *testing.T, repo restic.Repository, p float32) (list1, list2
 			h := restic.BlobHandle{ID: entry.ID, Type: entry.Type}
 			if blobs.Has(h) {
 				t.Errorf("ignoring duplicate blob %v", h)
-				continue
+				return nil
 			}
 			blobs.Insert(h)
 
@@ -93,8 +93,11 @@ func selectBlobs(t *testing.T, repo restic.Repository, p float32) (list1, list2
 			} else {
 				list2.Insert(restic.BlobHandle{ID: entry.ID, Type: entry.Type})
 			}
-
 		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
 	}
 
 	return list1, list2
@@ -102,8 +105,13 @@ func selectBlobs(t *testing.T, repo restic.Repository, p float32) (list1, list2
 
 func listPacks(t *testing.T, repo restic.Repository) restic.IDSet {
 	list := restic.NewIDSet()
-	for id := range repo.List(context.TODO(), restic.DataFile) {
+	err := repo.List(context.TODO(), restic.DataFile, func(id restic.ID, size int64) error {
 		list.Insert(id)
+		return nil
+	})
+
+	if err != nil {
+		t.Fatal(err)
 	}
 
 	return list
@@ -153,16 +161,16 @@ func rebuildIndex(t *testing.T, repo restic.Repository) {
 		t.Fatal(err)
 	}
 
-	for id := range repo.List(context.TODO(), restic.IndexFile) {
+	err = repo.List(context.TODO(), restic.IndexFile, func(id restic.ID, size int64) error {
 		h := restic.Handle{
 			Type: restic.IndexFile,
 			Name: id.String(),
 		}
-		err = repo.Backend().Remove(context.TODO(), h)
+		return repo.Backend().Remove(context.TODO(), h)
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
-	}
 
 	_, err = idx.Save(context.TODO(), repo, nil)
 	if err != nil {

internal/repository/repository.go

@@ -536,22 +536,15 @@ func (r *Repository) KeyName() string {
 	return r.keyName
 }
 
-// List returns a channel that yields all IDs of type t in the backend.
+// List runs fn for all files of type t in the repo.
-func (r *Repository) List(ctx context.Context, t restic.FileType) <-chan restic.ID {
+func (r *Repository) List(ctx context.Context, t restic.FileType, fn func(restic.ID, int64) error) error {
-	out := make(chan restic.ID)
+	return r.be.List(ctx, t, func(fi restic.FileInfo) error {
-	go func() {
+		id, err := restic.ParseID(fi.Name)
-		defer close(out)
+		if err != nil {
-		for strID := range r.be.List(ctx, t) {
+			debug.Log("unable to parse %v as an ID", fi.Name)
-			if id, err := restic.ParseID(strID); err == nil {
-				select {
-				case out <- id:
-				case <-ctx.Done():
-					return
 		}
-			}
+		return fn(id, fi.Size)
-		}
+	})
-	}()
-	return out
 }
 
 // ListPack returns the list of blobs saved in the pack id and the length of

internal/repository/repository_test.go

@@ -369,7 +369,7 @@ func TestRepositoryIncrementalIndex(t *testing.T) {
 
 	packEntries := make(map[restic.ID]map[restic.ID]struct{})
 
-	for id := range repo.List(context.TODO(), restic.IndexFile) {
+	err := repo.List(context.TODO(), restic.IndexFile, func(id restic.ID, size int64) error {
 		idx, err := repository.LoadIndex(context.TODO(), repo, id)
 		rtest.OK(t, err)
 
@@ -380,6 +380,10 @@ func TestRepositoryIncrementalIndex(t *testing.T) {
 
 			packEntries[pb.PackID][id] = struct{}{}
 		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
 	}
 
 	for packID, ids := range packEntries {

internal/restic/lock.go

@@ -157,15 +157,14 @@ func (l *Lock) checkForOtherLocks(ctx context.Context) error {
 }
 
 func eachLock(ctx context.Context, repo Repository, f func(ID, *Lock, error) error) error {
-	for id := range repo.List(ctx, LockFile) {
+	return repo.List(ctx, LockFile, func(id ID, size int64) error {
 		lock, err := LoadLock(ctx, repo, id)
-		err = f(id, lock, err)
 		if err != nil {
 			return err
 		}
-	}
 
-	return nil
+		return f(id, lock, err)
+	})
 }
 
 // createLock acquires the lock by creating a file in the repository.

internal/restic/lock_test.go

@@ -227,21 +227,29 @@ func TestLockRefresh(t *testing.T) {
 	rtest.OK(t, err)
 
 	var lockID *restic.ID
-	for id := range repo.List(context.TODO(), restic.LockFile) {
+	err = repo.List(context.TODO(), restic.LockFile, func(id restic.ID, size int64) error {
 		if lockID != nil {
 			t.Error("more than one lock found")
 		}
 		lockID = &id
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
 	}
 
 	rtest.OK(t, lock.Refresh(context.TODO()))
 
 	var lockID2 *restic.ID
-	for id := range repo.List(context.TODO(), restic.LockFile) {
+	err = repo.List(context.TODO(), restic.LockFile, func(id restic.ID, size int64) error {
 		if lockID2 != nil {
 			t.Error("more than one lock found")
 		}
 		lockID2 = &id
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
 	}
 
 	rtest.Assert(t, !lockID.Equal(*lockID2),

internal/restic/repository.go

@@ -26,7 +26,7 @@ type Repository interface {
 
 	LookupBlobSize(ID, BlobType) (uint, error)
 
-	List(context.Context, FileType) <-chan ID
+	List(context.Context, FileType, func(ID, int64) error) error
 	ListPack(context.Context, ID) ([]Blob, int64, error)
 
 	Flush(context.Context) error

internal/restic/snapshot.go

@@ -64,15 +64,21 @@ func LoadSnapshot(ctx context.Context, repo Repository, id ID) (*Snapshot, error
 
 // LoadAllSnapshots returns a list of all snapshots in the repo.
 func LoadAllSnapshots(ctx context.Context, repo Repository) (snapshots []*Snapshot, err error) {
-	for id := range repo.List(ctx, SnapshotFile) {
+	err = repo.List(ctx, SnapshotFile, func(id ID, size int64) error {
 		sn, err := LoadSnapshot(ctx, repo, id)
+		if err != nil {
+			return err
+		}
+
+		snapshots = append(snapshots, sn)
+		return nil
+	})
+
 	if err != nil {
 		return nil, err
 	}
 
-		snapshots = append(snapshots, sn)
+	return snapshots, nil
-	}
-	return
 }
 
 func (sn Snapshot) String() string {

internal/restic/snapshot_find.go

@@ -20,26 +20,31 @@ func FindLatestSnapshot(ctx context.Context, repo Repository, targets []string,
 		found    bool
 	)
 
-	for snapshotID := range repo.List(ctx, SnapshotFile) {
+	err := repo.List(ctx, SnapshotFile, func(snapshotID ID, size int64) error {
 		snapshot, err := LoadSnapshot(ctx, repo, snapshotID)
 		if err != nil {
-			return ID{}, errors.Errorf("Error listing snapshot: %v", err)
+			return errors.Errorf("Error loading snapshot %v: %v", snapshotID.Str(), err)
 		}
 		if snapshot.Time.Before(latest) || (hostname != "" && hostname != snapshot.Hostname) {
-			continue
+			return nil
 		}
 
 		if !snapshot.HasTagList(tagLists) {
-			continue
+			return nil
 		}
 
 		if !snapshot.HasPaths(targets) {
-			continue
+			return nil
 		}
 
 		latest = snapshot.Time
 		latestID = snapshotID
 		found = true
+		return nil
+	})
+
+	if err != nil {
+		return ID{}, err
 	}
 
 	if !found {
@@ -64,20 +69,27 @@ func FindSnapshot(repo Repository, s string) (ID, error) {
 
 // FindFilteredSnapshots yields Snapshots filtered from the list of all
 // snapshots.
-func FindFilteredSnapshots(ctx context.Context, repo Repository, host string, tags []TagList, paths []string) Snapshots {
+func FindFilteredSnapshots(ctx context.Context, repo Repository, host string, tags []TagList, paths []string) (Snapshots, error) {
 	results := make(Snapshots, 0, 20)
 
-	for id := range repo.List(ctx, SnapshotFile) {
+	err := repo.List(ctx, SnapshotFile, func(id ID, size int64) error {
 		sn, err := LoadSnapshot(ctx, repo, id)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "could not load snapshot %v: %v\n", id.Str(), err)
-			continue
+			return nil
 		}
+
 		if (host != "" && host != sn.Hostname) || !sn.HasTagList(tags) || !sn.HasPaths(paths) {
-			continue
+			return nil
 		}
 
 		results = append(results, sn)
+		return nil
+	})
+
+	if err != nil {
+		return nil, err
 	}
-	return results
+
+	return results, nil
 }