Merge pull request #21784 from jtru/fuse-mount-hardlink-count

mount: Ensure a hard link count > 0 for all files

changelog/unreleased/pull-21784

@@ -0,0 +1,9 @@
+Bugfix: Support exporting a `restic mount` of a Windows system via Samba
+
+A repository mounted using `restic mount` on a POSIX system, could not use
+Samba to export files from restic backups of Windows systems. Backups of
+other systems were not affected. This has been fixed.
+
+https://github.com/restic/restic/pull/21784
+https://github.com/restic/restic/issues/2034
+https://github.com/restic/restic/issues/4382

internal/fuse/file.go

@@ -55,7 +55,10 @@ func (f *file) Attr(_ context.Context, a *fuse.Attr) error {
 	a.Size = f.node.Size
 	a.Blocks = (f.node.Size + blockSize - 1) / blockSize
 	a.BlockSize = blockSize
-	a.Nlink = uint32(f.node.Links)
+	// Windows (and other non-POSIX) backups may store a link count of 0.
+	// FUSE must still report a positive nlink so tools that validate stat()
+	// (e.g. Samba) accept the file.
+	a.Nlink = max(uint32(1), uint32(f.node.Links))
 
 	if !f.root.cfg.OwnerIsRoot {
 		a.Uid = f.node.UID

internal/fuse/fuse_test.go

@@ -5,6 +5,7 @@ package fuse
 import (
 	"bytes"
 	"context"
+	"fmt"
 	"math/rand"
 	"os"
 	"strings"
@@ -277,6 +278,28 @@ func TestBlocks(t *testing.T) {
 	}
 }
 
+// Windows (and other non-POSIX) backups may store a link count of 0; FUSE
+// must still report a positive nlink so tools that validate stat() (e.g.
+// Samba) accept the file.
+func TestFileAttrNlink(t *testing.T) {
+	root := &Root{}
+	for _, tc := range []struct {
+		links uint64
+		want  uint32
+	}{
+		{0, 1},
+		{1, 1},
+		{42, 42},
+	} {
+		t.Run(fmt.Sprintf("links_%d", tc.links), func(t *testing.T) {
+			f := &file{root: root, node: &data.Node{Links: tc.links}}
+			var a fuse.Attr
+			rtest.OK(t, f.Attr(context.TODO(), &a))
+			rtest.Equals(t, tc.want, a.Nlink)
+		})
+	}
+}
+
 func TestInodeFromNode(t *testing.T) {
 	node := &data.Node{Name: "foo.txt", Type: data.NodeTypeCharDev, Links: 2}
 	ino1 := inodeFromNode(1, node)