CHECKSUM
uint8_t CHECKSUM:8;
JBD2_FEATURE_COMPAT_FUNCS(checksum, CHECKSUM)
if (!(inet_test_bit(CHECKSUM, sk))) {
inet_set_bit(CHECKSUM, sk);
if (inet_test_bit(CHECKSUM, sk)) {
inet_clear_bit(CHECKSUM, sk);
val = inet_test_bit(CHECKSUM, sk);