1 files changed, 74 insertions, 1 deletions
diff --git a/tests/cluster/cluster_test.go b/tests/cluster/cluster_test.go
index def03f1..23e7c50 100644
--- a/tests/cluster/cluster_test.go
+++ b/tests/cluster/cluster_test.go
@@ -7,6 +7,7 @@ package cluster_test
 
 import (
 	"bytes"
+	"errors"
 	"math/rand"
 	"os"
 	"sync"
@@ -15,6 +16,7 @@ import (
 
 	"golang.org/x/sys/unix"
 
+	"github.com/rfjakob/gocryptfs/v2/internal/contentenc"
 	"github.com/rfjakob/gocryptfs/v2/tests/test_helpers"
 )
 
@@ -39,7 +41,7 @@ func TestClusterConcurrentRW(t *testing.T) {
 			"Choose a backing directory by setting TMPDIR.")
 	}
 
-	const blocksize = 4096
+	const blocksize = contentenc.DefaultBS
 	const fileSize = 25 * blocksize // 100 kiB
 
 	cDir := test_helpers.InitFS(t)
@@ -113,6 +115,77 @@ func TestClusterConcurrentRW(t *testing.T) {
 	wg.Wait()
 }
 
+// Multiple hosts creating the same file at the same time could
+// overwrite each other's file header, leading to data
+// corruption. Passing "-sharedstorage" should prevent this.
+func TestConcurrentCreate(t *testing.T) {
+	cDir := test_helpers.InitFS(t)
+	mnt1 := cDir + ".mnt1"
+	mnt2 := cDir + ".mnt2"
+	test_helpers.MountOrFatal(t, cDir, mnt1, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
+	defer test_helpers.UnmountPanic(mnt1)
+	test_helpers.MountOrFatal(t, cDir, mnt2, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
+	defer test_helpers.UnmountPanic(mnt2)
+
+	var wg sync.WaitGroup
+	const loops = 10000
+
+	createOrOpen := func(path string) (f *os.File, err error) {
+		// Use the high-level os.Create/OpenFile instead of syscall.Open because we
+		// *want* Go's EINTR retry logic. glibc open(2) has similar logic.
+		f, err = os.OpenFile(path, os.O_CREATE|os.O_RDWR|os.O_EXCL, 0600)
+		if err == nil {
+			return
+		}
+		if !errors.Is(err, os.ErrExist) {
+			t.Logf("POSIX compliance issue: exclusive create failed with unexpected error: err=%v", errors.Unwrap(err))
+		}
+		f, err = os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
+		if err == nil {
+			return
+		}
+		t.Logf("POSIX compliance issue: non-exlusive create failed with err=%v", errors.Unwrap(err))
+		return
+	}
+
+	workerThread := func(path string) {
+		defer wg.Done()
+		buf := make([]byte, 10)
+		buf2 := make([]byte, 10)
+		for i := 0; i < loops; i++ {
+			if t.Failed() {
+				return
+			}
+			f, err := createOrOpen(path)
+			if err != nil {
+				// retry
+				continue
+			}
+			defer f.Close()
+			_, err = f.WriteAt(buf, 0)
+			if err != nil {
+				t.Errorf("iteration %d: Pwrite: %v", i, err)
+				return
+			}
+			_, err = f.ReadAt(buf2, 0)
+			if err != nil {
+				t.Errorf("iteration %d: ReadAt: %v", i, err)
+				return
+			}
+			if !bytes.Equal(buf, buf2) {
+				t.Errorf("iteration %d: corrupt data received: %x", i, buf2)
+				return
+			}
+			syscall.Unlink(path)
+		}
+	}
+
+	wg.Add(2)
+	go workerThread(mnt1 + "/foo")
+	go workerThread(mnt2 + "/foo")
+	wg.Wait()
+}
+
 // Check that byte-range locks work on an empty file
 func TestFcntlFlock(t *testing.T) {
 	path := test_helpers.TmpDir + "/" + t.Name()