lat_to_blkg
struct blkcg_gq *blkg = lat_to_blkg(iolat);
unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat)))
parent = blkg_to_lat(lat_to_blkg(iolat)->parent);
blkcg_use_delay(lat_to_blkg(iolat));
blkcg_clear_delay(lat_to_blkg(iolat));
blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time);
struct blkcg_gq *blkg = lat_to_blkg(iolat);
struct blkcg_gq *blkg = lat_to_blkg(iolat);