Merge pull request #3875 from MichaelEischer/fix-fuse-context-cancel

mount: Fix input/output errors for canceled syscalls

changelog/unreleased/issue-3567

@@ -0,0 +1,11 @@
+Bugfix: Improve handling of interrupted syscalls in `mount` command
+
+Accessing restic's fuse mount could result in "input / output" errors when
+using programs in which syscalls can be interrupted. This is for example the
+case for go programs.
+
+We have corrected the error handling for interrupted syscalls.
+
+https://github.com/restic/restic/issues/3567
+https://github.com/restic/restic/issues/3694
+https://github.com/restic/restic/pull/3875

internal/fuse/dir.go

@@ -5,6 +5,7 @@ package fuse
 
 import (
 	"context"
+	"errors"
 	"os"
 	"path/filepath"
 	"sync"
@@ -33,7 +34,7 @@ func cleanupNodeName(name string) string {
 	return filepath.Base(name)
 }
 
-func newDir(ctx context.Context, root *Root, inode, parentInode uint64, node *restic.Node) (*dir, error) {
+func newDir(root *Root, inode, parentInode uint64, node *restic.Node) (*dir, error) {
 	debug.Log("new dir for %v (%v)", node.Name, node.Subtree)
 
 	return &dir{
@@ -44,6 +45,16 @@ func newDir(ctx context.Context, root *Root, inode, parentInode uint64, node *re
 	}, nil
 }
 
+// returing a wrapped context.Canceled error will instead result in returing
+// an input / output error to the user. Thus unwrap the error to match the
+// expectations of bazil/fuse
+func unwrapCtxCanceled(err error) error {
+	if errors.Is(err, context.Canceled) {
+		return context.Canceled
+	}
+	return err
+}
+
 // replaceSpecialNodes replaces nodes with name "." and "/" by their contents.
 // Otherwise, the node is returned.
 func replaceSpecialNodes(ctx context.Context, repo restic.Repository, node *restic.Node) ([]*restic.Node, error) {
@@ -57,13 +68,13 @@ func replaceSpecialNodes(ctx context.Context, repo restic.Repository, node *rest
 
 	tree, err := restic.LoadTree(ctx, repo, *node.Subtree)
 	if err != nil {
-		return nil, err
+		return nil, unwrapCtxCanceled(err)
 	}
 
 	return tree.Nodes, nil
 }
 
-func newDirFromSnapshot(ctx context.Context, root *Root, inode uint64, snapshot *restic.Snapshot) (*dir, error) {
+func newDirFromSnapshot(root *Root, inode uint64, snapshot *restic.Snapshot) (*dir, error) {
 	debug.Log("new dir for snapshot %v (%v)", snapshot.ID(), snapshot.Tree)
 	return &dir{
 		root: root,
@@ -91,7 +102,7 @@ func (d *dir) open(ctx context.Context) error {
 	tree, err := restic.LoadTree(ctx, d.root.repo, *d.node.Subtree)
 	if err != nil {
 		debug.Log("  error loading tree %v: %v", d.node.Subtree, err)
-		return err
+		return unwrapCtxCanceled(err)
 	}
 	items := make(map[string]*restic.Node)
 	for _, n := range tree.Nodes {
@@ -195,13 +206,13 @@ func (d *dir) Lookup(ctx context.Context, name string) (fs.Node, error) {
 	}
 	switch node.Type {
 	case "dir":
-		return newDir(ctx, d.root, fs.GenerateDynamicInode(d.inode, name), d.inode, node)
+		return newDir(d.root, fs.GenerateDynamicInode(d.inode, name), d.inode, node)
 	case "file":
-		return newFile(ctx, d.root, fs.GenerateDynamicInode(d.inode, name), node)
+		return newFile(d.root, fs.GenerateDynamicInode(d.inode, name), node)
 	case "symlink":
-		return newLink(ctx, d.root, fs.GenerateDynamicInode(d.inode, name), node)
+		return newLink(d.root, fs.GenerateDynamicInode(d.inode, name), node)
 	case "dev", "chardev", "fifo", "socket":
-		return newOther(ctx, d.root, fs.GenerateDynamicInode(d.inode, name), node)
+		return newOther(d.root, fs.GenerateDynamicInode(d.inode, name), node)
 	default:
 		debug.Log("  node %v has unknown type %v", name, node.Type)
 		return nil, fuse.ENOENT

internal/fuse/file.go

@@ -36,7 +36,7 @@ type openFile struct {
 	cumsize []uint64
 }
 
-func newFile(ctx context.Context, root *Root, inode uint64, node *restic.Node) (fusefile *file, err error) {
+func newFile(root *Root, inode uint64, node *restic.Node) (fusefile *file, err error) {
 	debug.Log("create new file for %v with %d blobs", node.Name, len(node.Content))
 	return &file{
 		inode: inode,
@@ -105,7 +105,7 @@ func (f *openFile) getBlobAt(ctx context.Context, i int) (blob []byte, err error
 	blob, err = f.root.repo.LoadBlob(ctx, restic.DataBlob, f.node.Content[i], nil)
 	if err != nil {
 		debug.Log("LoadBlob(%v, %v) failed: %v", f.node.Name, f.node.Content[i], err)
-		return nil, err
+		return nil, unwrapCtxCanceled(err)
 	}
 
 	f.root.blobCache.Add(f.node.Content[i], blob)

internal/fuse/fuse_test.go

@@ -119,7 +119,7 @@ func TestFuseFile(t *testing.T) {
 	root := &Root{repo: repo, blobCache: bloblru.New(blobCacheSize)}
 
 	inode := fs.GenerateDynamicInode(1, "foo")
-	f, err := newFile(context.TODO(), root, inode, node)
+	f, err := newFile(root, inode, node)
 	rtest.OK(t, err)
 	of, err := f.Open(context.TODO(), nil, nil)
 	rtest.OK(t, err)
@@ -163,7 +163,7 @@ func TestFuseDir(t *testing.T) {
 	}
 	parentInode := fs.GenerateDynamicInode(0, "parent")
 	inode := fs.GenerateDynamicInode(1, "foo")
-	d, err := newDir(context.TODO(), root, inode, parentInode, node)
+	d, err := newDir(root, inode, parentInode, node)
 	rtest.OK(t, err)
 
 	// don't open the directory as that would require setting up a proper tree blob

internal/fuse/link.go

@@ -20,7 +20,7 @@ type link struct {
 	inode uint64
 }
 
-func newLink(ctx context.Context, root *Root, inode uint64, node *restic.Node) (*link, error) {
+func newLink(root *Root, inode uint64, node *restic.Node) (*link, error) {
 	return &link{root: root, inode: inode, node: node}, nil
 }
 

internal/fuse/other.go

@@ -16,7 +16,7 @@ type other struct {
 	inode uint64
 }
 
-func newOther(ctx context.Context, root *Root, inode uint64, node *restic.Node) (*other, error) {
+func newOther(root *Root, inode uint64, node *restic.Node) (*other, error) {
 	return &other{root: root, inode: inode, node: node}, nil
 }
 

internal/fuse/snapshots_dir.go

@@ -58,7 +58,7 @@ func (d *SnapshotsDir) ReadDirAll(ctx context.Context) ([]fuse.Dirent, error) {
 	// update snapshots
 	meta, err := d.dirStruct.UpdatePrefix(ctx, d.prefix)
 	if err != nil {
-		return nil, err
+		return nil, unwrapCtxCanceled(err)
 	} else if meta == nil {
 		return nil, fuse.ENOENT
 	}
@@ -97,17 +97,17 @@ func (d *SnapshotsDir) Lookup(ctx context.Context, name string) (fs.Node, error)
 
 	meta, err := d.dirStruct.UpdatePrefix(ctx, d.prefix)
 	if err != nil {
-		return nil, err
+		return nil, unwrapCtxCanceled(err)
 	} else if meta == nil {
 		return nil, fuse.ENOENT
 	}
 
 	entry := meta.names[name]
 	if entry != nil {
 		if entry.linkTarget != "" {
-			return newSnapshotLink(ctx, d.root, fs.GenerateDynamicInode(d.inode, name), entry.linkTarget, entry.snapshot)
+			return newSnapshotLink(d.root, fs.GenerateDynamicInode(d.inode, name), entry.linkTarget, entry.snapshot)
 		} else if entry.snapshot != nil {
-			return newDirFromSnapshot(ctx, d.root, fs.GenerateDynamicInode(d.inode, name), entry.snapshot)
+			return newDirFromSnapshot(d.root, fs.GenerateDynamicInode(d.inode, name), entry.snapshot)
 		} else {
 			return NewSnapshotsDir(d.root, fs.GenerateDynamicInode(d.inode, name), d.inode, d.dirStruct, d.prefix+"/"+name), nil
 		}
@@ -127,7 +127,7 @@ type snapshotLink struct {
 var _ = fs.NodeReadlinker(&snapshotLink{})
 
 // newSnapshotLink
-func newSnapshotLink(ctx context.Context, root *Root, inode uint64, target string, snapshot *restic.Snapshot) (*snapshotLink, error) {
+func newSnapshotLink(root *Root, inode uint64, target string, snapshot *restic.Snapshot) (*snapshotLink, error) {
 	return &snapshotLink{root: root, inode: inode, target: target, snapshot: snapshot}, nil
 }