Prevent operations on a file once it's closed

internal/fsproto/errors.go

@@ -11,6 +11,7 @@ var (
 	ErrFileWriteOnly = errors.New("file is write only")
 	ErrInvalidOffset = errors.New("offset out of range")
 	ErrNoRemoveRoot  = errors.New("refusing to remove root directory")
+	ErrFileClosed    = errors.New("cannot perform operation on a closed file")
 )
 
 // Error represents an error returned by BLE FS

internal/fusefs/syscallerr.go

@@ -61,6 +61,8 @@ func syscallErr(err error) syscall.Errno {
 			return syscall.EINVAL
 		case fsproto.ErrNoRemoveRoot: // refusing to remove root directory
 			return syscall.EPERM
+		case fsproto.ErrFileClosed: // cannot perform operation on closed file
+			return syscall.EBADF
 		default:
 			return syscall.EINVAL
 		}