nodefs: by default return input offset for Lseek

nodefs/constants.go

@@ -21,3 +21,9 @@ func ToErrno(err error) syscall.Errno {
 
 // RENAME_EXCHANGE is a flag argument for renameat2()
 const RENAME_EXCHANGE = 0x2
+
+// seek to the next data
+const _SEEK_DATA = 3
+
+// seek to the next hole
+const _SEEK_HOLE = 4

nodefs/default.go

@@ -195,10 +195,16 @@ func (n *OperationStubs) CopyFileRange(ctx context.Context, fhIn FileHandle,
 	return 0, syscall.EROFS
 }
 
+// Lseek is called for seeking to and beyond holes. By default, it
+// returns the input offset unchanged.
 func (n *OperationStubs) Lseek(ctx context.Context, f FileHandle, off uint64, whence uint32) (uint64, syscall.Errno) {
 	if f != nil {
 		return f.Lseek(ctx, off, whence)
 	}
+	if whence == _SEEK_DATA || whence == _SEEK_HOLE {
+		return off, OK
+	}
+
 	return 0, syscall.ENOTSUP
 }
 

nodefs/directio_test.go

@@ -81,9 +81,7 @@ func TestDirectIO(t *testing.T) {
 		t.Errorf("got %q want %q", got, want)
 	}
 
-	const SEEK_DATA = 3 /* seek to the next data */
-
-	if n, err := syscall.Seek(int(f.Fd()), 512, SEEK_DATA); err != nil {
+	if n, err := syscall.Seek(int(f.Fd()), 512, _SEEK_DATA); err != nil {
 		t.Errorf("Seek: %v", err)
 	} else if n != 1024 {
 		t.Errorf("seek: got %d, want %d", n, 1024)