Set Nlink = 1 if not set by lookup method. This fixes hardlink on

newer kernels.

fuse/fsconnector.go

@@ -83,6 +83,11 @@ func (me *FileSystemConnector) childLookup(fi *os.FileInfo, fsi FsNode) (out *En
 	out = n.mount.fileInfoToEntry(fi)
 	out.Ino = me.lookupUpdate(n)
 	out.NodeId = out.Ino
+	if out.Nlink == 0 {
+		// With Nlink == 0, newer kernels will refuse link
+		// operations.
+		out.Nlink = 1
+	}
 	return out
 }
 

unionfs/memunionfs_test.go

@@ -338,6 +338,19 @@ func TestMemUnionFsLink(t *testing.T) {
 	}
 }
 
+func TestMemUnionFsCreateLink(t *testing.T) {
+	wd, _, clean := setupMemUfs(t)
+	defer clean()
+
+	content := "blabla"
+	fn := wd + "/mnt/file"
+	err := ioutil.WriteFile(fn, []byte(content), 0666)
+	CheckSuccess(err)
+
+	err = os.Link(wd+"/mount/file", wd+"/mount/linked")
+	CheckSuccess(err)
+}
+
 func TestMemUnionFsTruncate(t *testing.T) {
 	wd, _, clean := setupMemUfs(t)
 	defer clean()