tests: add diriv cache race test

Passes.

tests/defaults/diriv_test.go

@@ -0,0 +1,73 @@
+package defaults
+
+import (
+	"io/ioutil"
+	"os"
+	"sync"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/rfjakob/gocryptfs/tests/test_helpers"
+)
+
+func TestDirIVRace(t *testing.T) {
+	// Create "dir1" with one file in it
+	dir1 := test_helpers.DefaultPlainDir + "/TestDirIVRace_Dir1"
+	err := os.Mkdir(dir1, 0700)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = ioutil.WriteFile(dir1+"/file", nil, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Create directory "dir2"
+	dir2 := test_helpers.DefaultPlainDir + "/TestDirIVRace_Dir2"
+	err = os.Mkdir(dir2, 0700)
+	if err != nil {
+		t.Fatal(err)
+	}
+	file2 := dir2 + "/file"
+	err = ioutil.WriteFile(file2, nil, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stop := false
+	defer func() { stop = true }()
+
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		wg.Done()
+		for {
+			// Keep dir2 in the diriv cache
+			fd, err2 := os.Open(file2)
+			if err2 != nil {
+				fd.Close()
+			}
+			if stop {
+				return
+			}
+		}
+	}()
+	wg.Wait()
+	time.Sleep(time.Millisecond)
+
+	// Overwrite dir2 with dir1
+	err = syscall.Unlink(file2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = syscall.Rename(dir1, dir2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// We should be able to stat file2
+	_, err = os.Stat(file2)
+	if err != nil {
+		t.Error(err)
+	}
+}