Make sure that tombstone markers are always readable.

Add test.

unionfs/unionfs.go

@@ -208,16 +208,26 @@ func (me *UnionFs) removeDeletion(name string) {
 	}
 }
 
-func (me *UnionFs) putDeletion(name string) fuse.Status {
+func (me *UnionFs) putDeletion(name string) (code fuse.Status) {
 	marker := me.deletionPath(name)
 	me.deletionCache.AddEntry(path.Base(marker))
 
 	// Is there a WriteStringToFileOrDie ?
 	writable := me.fileSystems[0]
-	f, code := writable.Open(marker, uint32(os.O_TRUNC|os.O_WRONLY|os.O_CREATE))
+	fi, code := writable.GetAttr(marker)
+	if code.Ok() && fi.Size == int64(len(name)) {
+		return fuse.OK
+	}
+	
+	var f fuse.File
+	if code == fuse.ENOENT {
+		f, code = writable.Create(marker, uint32(os.O_TRUNC|os.O_WRONLY), 0644)
+	} else {
+		writable.Chmod(marker, 0644)
+		f, code = writable.Open(marker, uint32(os.O_TRUNC|os.O_WRONLY))
+	}
 	if !code.Ok() {
-		log.Printf("could not create deletion file %v: %v",
-			marker, code)
+		log.Printf("could not create deletion file %v: %v", marker, code)
 		return fuse.EPERM
 	}
 	defer f.Release()

unionfs/unionfs_test.go

@@ -178,6 +178,36 @@ func TestChmod(t *testing.T) {
 	}
 }
 
+func TestDelete(t *testing.T) {
+	wd, clean := setupUfs(t)
+	defer clean()
+
+	writeToFile(wd+"/ro/file", "a")
+	_, err := os.Lstat(wd + "/mount/file")
+	CheckSuccess(err)
+
+	err = os.Remove(wd + "/mount/file")
+	CheckSuccess(err)
+
+	_, err = os.Lstat(wd + "/mount/file")
+	if err == nil {
+		t.Fatal("should have disappeared.")
+	}
+	delPath := wd + "/rw/" + testOpts.DeletionDirName
+	names := dirNames(delPath)
+	if len(names) != 1 {
+		t.Fatal("Should have 1 deletion", names)
+	}
+
+	for k, _ := range names {
+		c, err := ioutil.ReadFile(delPath + "/" + k)
+		CheckSuccess(err)
+		if string(c) != "file" {
+			t.Fatal("content mismatch", string(c)) 
+		}
+	}
+}
+
 func TestBasic(t *testing.T) {
 	wd, clean := setupUfs(t)
 	defer clean()