__bch_keylist_realloc
int __bch_keylist_realloc(struct keylist *l, unsigned int u64s);
if (__bch_keylist_realloc(&keylist,
if (__bch_keylist_realloc(&keylist, bkey_u64s(&r[i].b->key)))
return __bch_keylist_realloc(l, u64s);