R10BIO_Previous
test_bit(R10BIO_Previous, &r10_bio->state))
if (!_enough(conf, test_bit(R10BIO_Previous, &r10_bio->state),
BUG_ON(!test_bit(R10BIO_Previous, &r10_bio->state));
set_bit(R10BIO_Previous, &r10bio->state);
clear_bit(R10BIO_Previous, &r10bio->state);