STRIPE_EXPAND_SOURCE
clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
s->expanding = test_bit(STRIPE_EXPAND_SOURCE, &sh->state) && !sh->batch_head;
if (sh_src && test_bit(STRIPE_EXPAND_SOURCE, &sh_src->state)) {
set_bit(STRIPE_EXPAND_SOURCE, &sh->state);
((1 << STRIPE_EXPAND_SOURCE) |\