fuse: Improve semantics of the blob size cache

Wrap it in a struct and add a Lookup() function to make clear that it
is only queried, not changed, so we don't have any race conditions.

src/restic/fuse/dir.go

@@ -25,10 +25,10 @@ type dir struct {
 	node        *restic.Node
 	ownerIsRoot bool
 
-	sizes map[restic.ID]uint
+	blobsize *BlobSizeCache
 }
 
-func newDir(ctx context.Context, repo restic.Repository, node *restic.Node, ownerIsRoot bool, sizes map[restic.ID]uint) (*dir, error) {
+func newDir(ctx context.Context, repo restic.Repository, node *restic.Node, ownerIsRoot bool, blobsize *BlobSizeCache) (*dir, error) {
 	debug.Log("new dir for %v (%v)", node.Name, node.Subtree.Str())
 	tree, err := repo.LoadTree(ctx, *node.Subtree)
 	if err != nil {
@@ -46,7 +46,7 @@ func newDir(ctx context.Context, repo restic.Repository, node *restic.Node, owne
 		items:       items,
 		inode:       node.Inode,
 		ownerIsRoot: ownerIsRoot,
-		sizes:       sizes,
+		blobsize:    blobsize,
 	}, nil
 }
 
@@ -69,7 +69,7 @@ func replaceSpecialNodes(ctx context.Context, repo restic.Repository, node *rest
 	return tree.Nodes, nil
 }
 
-func newDirFromSnapshot(ctx context.Context, repo restic.Repository, snapshot SnapshotWithId, ownerIsRoot bool, sizes map[restic.ID]uint) (*dir, error) {
+func newDirFromSnapshot(ctx context.Context, repo restic.Repository, snapshot SnapshotWithId, ownerIsRoot bool, blobsize *BlobSizeCache) (*dir, error) {
 	debug.Log("new dir for snapshot %v (%v)", snapshot.ID.Str(), snapshot.Tree.Str())
 	tree, err := repo.LoadTree(ctx, *snapshot.Tree)
 	if err != nil {
@@ -102,7 +102,7 @@ func newDirFromSnapshot(ctx context.Context, repo restic.Repository, snapshot Sn
 		items:       items,
 		inode:       inodeFromBackendID(snapshot.ID),
 		ownerIsRoot: ownerIsRoot,
-		sizes:       sizes,
+		blobsize:    blobsize,
 	}, nil
 }
 
@@ -171,9 +171,9 @@ func (d *dir) Lookup(ctx context.Context, name string) (fs.Node, error) {
 	}
 	switch node.Type {
 	case "dir":
-		return newDir(ctx, d.repo, node, d.ownerIsRoot, d.sizes)
+		return newDir(ctx, d.repo, node, d.ownerIsRoot, d.blobsize)
 	case "file":
-		return newFile(d.repo, node, d.ownerIsRoot, d.sizes)
+		return newFile(d.repo, node, d.ownerIsRoot, d.blobsize)
 	case "symlink":
 		return newLink(d.repo, node, d.ownerIsRoot)
 	default:

src/restic/fuse/file.go

@@ -41,12 +41,12 @@ type file struct {
 
 const defaultBlobSize = 128 * 1024
 
-func newFile(repo BlobLoader, node *restic.Node, ownerIsRoot bool, sizecache map[restic.ID]uint) (fusefile *file, err error) {
+func newFile(repo BlobLoader, node *restic.Node, ownerIsRoot bool, blobsize *BlobSizeCache) (fusefile *file, err error) {
 	debug.Log("create new file for %v with %d blobs", node.Name, len(node.Content))
 	var bytes uint64
 	sizes := make([]int, len(node.Content))
 	for i, id := range node.Content {
-		size, ok := sizecache[id]
+		size, ok := blobsize.Lookup(id)
 		if !ok {
 			size, err = repo.LookupBlobSize(id, restic.DataBlob)
 			if err != nil {

src/restic/fuse/file_test.go

@@ -108,7 +108,7 @@ func TestFuseFile(t *testing.T) {
 		Size:    filesize,
 		Content: content,
 	}
-	f, err := newFile(repo, node, false, make(map[restic.ID]uint))
+	f, err := newFile(repo, node, false, nil)
 	OK(t, err)
 
 	attr := fuse.Attr{}

src/restic/fuse/snapshot.go

@@ -19,6 +19,34 @@ import (
 	"golang.org/x/net/context"
 )
 
+// BlobSizeCache caches the size of blobs in the repo.
+type BlobSizeCache struct {
+	m map[restic.ID]uint
+}
+
+// NewBlobSizeCache returns a new blob size cache containing all entries from midx.
+func NewBlobSizeCache(midx *repository.MasterIndex) *BlobSizeCache {
+	m := make(map[restic.ID]uint, 1000)
+	for _, idx := range midx.All() {
+		for pb := range idx.Each(nil) {
+			m[pb.ID] = pb.Length
+		}
+	}
+	return &BlobSizeCache{
+		m: m,
+	}
+}
+
+// Lookup returns the size of the blob id.
+func (c *BlobSizeCache) Lookup(id restic.ID) (size uint, found bool) {
+	if c == nil {
+		return 0, false
+	}
+
+	size, found = c.m[id]
+	return size, found
+}
+
 type SnapshotWithId struct {
 	*restic.Snapshot
 	restic.ID
@@ -37,8 +65,7 @@ type SnapshotsDir struct {
 	tags        []string
 	host        string
 
-	// sizes caches the sizes of all blobs.
-	sizes map[restic.ID]uint
+	blobsize *BlobSizeCache
 
 	// knownSnapshots maps snapshot timestamp to the snapshot
 	sync.RWMutex
@@ -46,16 +73,6 @@ type SnapshotsDir struct {
 	processed      restic.IDSet
 }
 
-func sizeCache(midx *repository.MasterIndex) map[restic.ID]uint {
-	c := make(map[restic.ID]uint, 1000)
-	for _, idx := range midx.All() {
-		for pb := range idx.Each(nil) {
-			c[pb.ID] = pb.Length
-		}
-	}
-	return c
-}
-
 // NewSnapshotsDir returns a new dir object for the snapshots.
 func NewSnapshotsDir(repo restic.Repository, ownerIsRoot bool, paths []string, tags []string, host string) *SnapshotsDir {
 	debug.Log("fuse mount initiated")
@@ -67,7 +84,7 @@ func NewSnapshotsDir(repo restic.Repository, ownerIsRoot bool, paths []string, t
 		host:           host,
 		knownSnapshots: make(map[string]SnapshotWithId),
 		processed:      restic.NewIDSet(),
-		sizes:          sizeCache(repo.Index().(*repository.MasterIndex)),
+		blobsize:       NewBlobSizeCache(repo.Index().(*repository.MasterIndex)),
 	}
 }
 
@@ -173,5 +190,5 @@ func (sn *SnapshotsDir) Lookup(ctx context.Context, name string) (fs.Node, error
 		}
 	}
 
-	return newDirFromSnapshot(ctx, sn.repo, snapshot, sn.ownerIsRoot, sn.sizes)
+	return newDirFromSnapshot(ctx, sn.repo, snapshot, sn.ownerIsRoot, sn.blobsize)
 }