UBLK_TAG_OFF
return ((pos - UBLKSRV_IO_BUF_OFFSET) >> UBLK_TAG_OFF) &
#define UBLK_QID_OFF (UBLK_TAG_OFF + UBLK_TAG_BITS)
((__u64)q_id << UBLK_QID_OFF | (__u64)tag << UBLK_TAG_OFF);