1 files changed, 54 insertions, 9 deletions
diff --git a/tests/root_test/btrfs_test.go b/tests/root_test/btrfs_test.go
index 72b7751..898cd39 100644
--- a/tests/root_test/btrfs_test.go
+++ b/tests/root_test/btrfs_test.go
@@ -12,12 +12,20 @@ import (
 	"github.com/rfjakob/gocryptfs/v2/tests/test_helpers"
 )
 
-// TestBtrfsQuirks needs root permissions because it creates a loop disk
-func TestBtrfsQuirks(t *testing.T) {
+// createBtrfsImage creates a btrfs image file, formats it, and mounts it.
+// Returns the mount path and a cleanup function.
+func createBtrfsImage(t *testing.T) (mnt string, cleanup func()) {
+	t.Helper()
+
 	if os.Getuid() != 0 {
 		t.Skip("must run as root")
 	}
 
+	_, err := exec.LookPath("mkfs.btrfs")
+	if err != nil {
+		t.Skip("mkfs.btrfs not found, skipping test")
+	}
+
 	img := filepath.Join(test_helpers.TmpDir, t.Name()+".img")
 	f, err := os.Create(img)
 	if err != nil {
@@ -31,10 +39,6 @@ func TestBtrfsQuirks(t *testing.T) {
 	}
 
 	// Format as Btrfs
-	_, err = exec.LookPath("mkfs.btrfs")
-	if err != nil {
-		t.Skip("mkfs.btrfs not found, skipping test")
-	}
 	cmd := exec.Command("mkfs.btrfs", img)
 	out, err := cmd.CombinedOutput()
 	if err != nil {
@@ -44,7 +48,7 @@ func TestBtrfsQuirks(t *testing.T) {
 	}
 
 	// Mount
-	mnt := img + ".mnt"
+	mnt = img + ".mnt"
 	err = os.Mkdir(mnt, 0600)
 	if err != nil {
 		t.Fatal(err)
@@ -55,11 +59,52 @@ func TestBtrfsQuirks(t *testing.T) {
 		t.Log(string(out))
 		t.Fatal(err)
 	}
-	defer syscall.Unlink(img)
-	defer syscall.Unmount(mnt, 0)
+
+	cleanup = func() {
+		syscall.Unmount(mnt, 0)
+		syscall.Unlink(img)
+	}
+	return mnt, cleanup
+}
+
+// TestBtrfsQuirks needs root permissions because it creates a loop disk
+func TestBtrfsQuirks(t *testing.T) {
+	mnt, cleanup := createBtrfsImage(t)
+	defer cleanup()
 
 	quirk := syscallcompat.DetectQuirks(mnt)
 	if quirk != syscallcompat.QuirkBtrfsBrokenFalloc {
 		t.Errorf("wrong quirk: %v", quirk)
 	}
 }
+
+// TestBtrfsQuirksNoCow verifies that when the backing directory has
+// the NOCOW attribute (chattr +C), the QuirkBtrfsBrokenFalloc quirk
+// is NOT set, because fallocate works correctly with NOCOW.
+func TestBtrfsQuirksNoCow(t *testing.T) {
+	mnt, cleanup := createBtrfsImage(t)
+	defer cleanup()
+
+	_, err := exec.LookPath("chattr")
+	if err != nil {
+		t.Skip("chattr not found, skipping test")
+	}
+
+	// Create a subdirectory with NOCOW attribute
+	nocowDir := filepath.Join(mnt, "nocow")
+	err = os.Mkdir(nocowDir, 0700)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cmd := exec.Command("chattr", "+C", nocowDir)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Log(string(out))
+		t.Fatal(err)
+	}
+
+	quirk := syscallcompat.DetectQuirks(nocowDir)
+	if quirk&syscallcompat.QuirkBtrfsBrokenFalloc != 0 {
+		t.Errorf("QuirkBtrfsBrokenFalloc should not be set on NOCOW directory, got quirks: %v", quirk)
+	}
+}