block: kill request ->cpu member

This was used for completion placement for the legacy path,
but for mq we have rq->mq_ctx->cpu for that. Add a helper
to get the request CPU assignment, as the mq_ctx type is
private to blk-mq.
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -145,7 +145,6 @@ void blk_rq_init(struct request_queue *q, struct request *rq)
 
 	INIT_LIST_HEAD(&rq->queuelist);
 	INIT_LIST_HEAD(&rq->timeout_list);
-	rq->cpu = -1;
 	rq->q = q;
 	rq->__sector = (sector_t) -1;
 	INIT_HLIST_NODE(&rq->hash);
@@ -1770,7 +1769,6 @@ EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
  */
 static void __blk_rq_prep_clone(struct request *dst, struct request *src)
 {
-	dst->cpu = src->cpu;
 	dst->__sector = blk_rq_pos(src);
 	dst->__data_len = blk_rq_bytes(src);
 	if (src->rq_flags & RQF_SPECIAL_PAYLOAD) {

block/blk-merge.c

@@ -806,8 +806,6 @@ static struct request *attempt_merge(struct request_queue *q,
 	blk_account_io_merge(next);
 
 	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
-	if (blk_rq_cpu_valid(next))
-		req->cpu = next->cpu;
 
 	/*
 	 * ownership of bio passed from next to req, return 'next' for

block/blk-mq.c

@@ -297,7 +297,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	rq->q = data->q;
 	rq->mq_ctx = data->ctx;
 	rq->rq_flags = rq_flags;
-	rq->cpu = -1;
 	rq->cmd_flags = op;
 	if (data->flags & BLK_MQ_REQ_PREEMPT)
 		rq->rq_flags |= RQF_PREEMPT;
@@ -3282,6 +3281,12 @@ static bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie)
 	return __blk_mq_poll(hctx, rq);
 }
 
+unsigned int blk_mq_rq_cpu(struct request *rq)
+{
+	return rq->mq_ctx->cpu;
+}
+EXPORT_SYMBOL(blk_mq_rq_cpu);
+
 static int __init blk_mq_init(void)
 {
 	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,

block/blk-softirq.c

@@ -98,7 +98,7 @@ static int blk_softirq_cpu_dead(unsigned int cpu)
 void __blk_complete_request(struct request *req)
 {
 	struct request_queue *q = req->q;
-	int cpu, ccpu = q->mq_ops ? req->mq_ctx->cpu : req->cpu;
+	int cpu, ccpu = req->mq_ctx->cpu;
 	unsigned long flags;
 	bool shared = false;
 

drivers/scsi/bnx2i/bnx2i_hwi.c

@@ -1906,7 +1906,6 @@ static int bnx2i_queue_scsi_cmd_resp(struct iscsi_session *session,
 	struct iscsi_task *task;
 	struct scsi_cmnd *sc;
 	int rc = 0;
-	int cpu;
 
 	spin_lock(&session->back_lock);
 	task = iscsi_itt_to_task(bnx2i_conn->cls_conn->dd_data,
@@ -1917,14 +1916,9 @@ static int bnx2i_queue_scsi_cmd_resp(struct iscsi_session *session,
 	}
 	sc = task->sc;
 
-	if (!blk_rq_cpu_valid(sc->request))
-		cpu = smp_processor_id();
-	else
-		cpu = sc->request->cpu;
-
 	spin_unlock(&session->back_lock);
 
-	p = &per_cpu(bnx2i_percpu, cpu);
+	p = &per_cpu(bnx2i_percpu, blk_mq_rq_cpu(sc->request));
 	spin_lock(&p->p_work_lock);
 	if (unlikely(!p->iothread)) {
 		rc = -EINVAL;

drivers/scsi/csiostor/csio_scsi.c

@@ -1780,16 +1780,10 @@ csio_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmnd)
 	int nsge = 0;
 	int rv = SCSI_MLQUEUE_HOST_BUSY, nr;
 	int retval;
-	int cpu;
 	struct csio_scsi_qset *sqset;
 	struct fc_rport *rport = starget_to_rport(scsi_target(cmnd->device));
 
-	if (!blk_rq_cpu_valid(cmnd->request))
-		cpu = smp_processor_id();
-	else
-		cpu = cmnd->request->cpu;
-
-	sqset = &hw->sqset[ln->portid][cpu];
+	sqset = &hw->sqset[ln->portid][blk_mq_rq_cpu(cmnd->request)];
 
 	nr = fc_remote_port_chkready(rport);
 	if (nr) {

drivers/scsi/qla2xxx/qla_os.c

@@ -1460,7 +1460,7 @@ __qla2xxx_eh_generic_reset(char *name, enum nexus_wait_type type,
 		goto eh_reset_failed;
 	}
 	err = 2;
-	if (do_reset(fcport, cmd->device->lun, cmd->request->cpu + 1)
+	if (do_reset(fcport, cmd->device->lun, blk_mq_rq_cpu(cmd->request) + 1)
 		!= QLA_SUCCESS) {
 		ql_log(ql_log_warn, vha, 0x800c,
 		    "do_reset failed for cmd=%p.\n", cmd);

include/linux/blk-mq.h

@@ -300,6 +300,8 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
 
 void blk_mq_quiesce_queue_nowait(struct request_queue *q);
 
+unsigned int blk_mq_rq_cpu(struct request *rq);
+
 /**
  * blk_mq_mark_complete() - Set request state to complete
  * @rq: request to set to complete state

include/linux/blkdev.h

@@ -130,7 +130,6 @@ struct request {
 	struct request_queue *q;
 	struct blk_mq_ctx *mq_ctx;
 
-	int cpu;
 	unsigned int cmd_flags;		/* op and common flags */
 	req_flags_t rq_flags;
 
@@ -669,7 +668,6 @@ static inline bool blk_account_rq(struct request *rq)
 	return (rq->rq_flags & RQF_STARTED) && !blk_rq_is_passthrough(rq);
 }
 
-#define blk_rq_cpu_valid(rq)	((rq)->cpu != -1)
 #define blk_bidi_rq(rq)		((rq)->next_rq != NULL)
 
 #define list_entry_rq(ptr)	list_entry((ptr), struct request, queuelist)