Add rmw race test

main_test.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"runtime"
+	"sync"
 	"bytes"
 	"crypto/md5"
 	"encoding/hex"
@@ -12,13 +14,14 @@ import (
 	"testing"
 )
 
-const tmpDir = "tmp/"
+const tmpDir = "/tmp/"
 const plainDir = tmpDir + "plain/"
 const cipherDir = tmpDir + "cipher/"
 
 func mount(extraArgs ...string) {
 	var args []string
 	args = append(args, extraArgs...)
+	//args = append(args, "--fusedebug")
 	args = append(args, cipherDir)
 	args = append(args, plainDir)
 	c := exec.Command("./gocryptfs", args...)
@@ -44,6 +47,10 @@ func md5fn(filename string) string {
 		fmt.Printf("ReadFile: %v\n", err)
 		return ""
 	}
+	return md5hex(buf)
+}
+
+func md5hex(buf []byte) string {
 	rawHash := md5.Sum(buf)
 	hash := hex.EncodeToString(rawHash[:])
 	return hash
@@ -209,6 +216,84 @@ func TestFileHoles(t *testing.T) {
 	}
 }
 
+func sContains(haystack []string, needle string) bool {
+    for _, element := range haystack {
+        if element == needle {
+            return true
+        }
+    }
+    return false
+}
+
+func TestRmwRace(t *testing.T) {
+
+	runtime.GOMAXPROCS(10)
+
+	fn := plainDir + "rmwrace"
+	f1, err := os.Create(fn)
+	if err != nil {
+		t.Errorf("file create failed")
+	}
+	f2, err := os.Create(fn)
+	if err != nil {
+		t.Errorf("file create failed")
+	}
+
+	oldBlock := bytes.Repeat([]byte("o"), 4096)
+
+	newBlock := bytes.Repeat([]byte("n"), 4096)
+
+	shortBlock := bytes.Repeat([]byte("s"), 16)
+
+	mergedBlock := make([]byte, 4096)
+	copy(mergedBlock, newBlock)
+	copy(mergedBlock[4080:], shortBlock)
+
+	goodMd5 := make(map[string]int)
+
+	for i := 0; i < 1000; i++ {
+		// Reset to [ooooooooo]
+		_, err = f1.WriteAt(oldBlock, 0)
+		if err != nil {
+			t.Errorf("Write failed")
+		}
+
+		var wg sync.WaitGroup
+		wg.Add(2)
+
+		// Write to the end of the file, [....ssss]
+		go func() {
+			f1.WriteAt(shortBlock, 4080)
+			wg.Done()
+		}()
+
+		// Overwrite to [nnnnnnn]
+		go func() {
+			f2.WriteAt(newBlock, 0)
+			wg.Done()
+		}()
+
+		wg.Wait()
+
+		// The file should be either:
+		// [nnnnnnnnnn] (md5: 6c1660fdabccd448d1359f27b3db3c99) or
+		// [nnnnnnssss] (md5: da885006a6a284530a427c73ce1e5c32)
+		// but it must not be
+		// [oooooossss]
+
+		buf, _ := ioutil.ReadFile(fn)
+		m := md5hex(buf)
+		goodMd5[m] = goodMd5[m] + 1
+
+		/*
+		if m == "6c1660fdabccd448d1359f27b3db3c99" {
+			fmt.Println(hex.Dump(buf))
+			t.FailNow()
+		}
+		*/
+	}
+	fmt.Println(goodMd5)
+}
 func BenchmarkStreamWrite(t *testing.B) {
 	buf := make([]byte, 1024*1024)
 	t.SetBytes(int64(len(buf)))