Re: [RFC PATCH 2/2] nvmet_tcp: enable polling nvme for completions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 55bcee5dc032..ceacf327f65e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c

@@ -3832,6 +3832,28 @@ static bool blk_mq_poll_hybrid(struct request_queue *q,
  	return blk_mq_poll_hybrid_sleep(q, rq);
  }
  
+int blk_poll_once(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	int ret;
+
+	if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
+		return 0;
+
+	hctx = blk_mq_map_queue_type(q, HCTX_TYPE_POLL, smp_processor_id());

+	if (!hctx) {
+		pr_err("%s: hctx not resolved\n", __func__);
+		return 0;
+	}
+
+	hctx->poll_invoked++;
+	ret = q->mq_ops->poll(hctx);
+	if (ret > 0)
+		hctx->poll_success++;
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blk_poll_once);
+
  /**
   * blk_poll - poll for IO completions
   * @q:  the queue

diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 125dde3f410e..1d9ee8546ae1 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c

@@ -269,6 +269,12 @@ static void nvmet_bdev_execute_rw(struct nvmet_req *req)
  	bio->bi_iter.bi_sector = sector;
  	bio->bi_private = req;
  	bio->bi_end_io = nvmet_bio_done;
+	/* Set hipri flag to trigger use of poll queues */
+	if ((req->op & REQ_HIPRI) &&
+	    test_bit(QUEUE_FLAG_POLL, &bio->bi_disk->queue->queue_flags)) {
+		op |= REQ_HIPRI;
+		req->queue = bio->bi_disk->queue;
+	}
  	bio->bi_opf = op;
  
  	blk_start_plug(&plug);

diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 559a15ccc322..65900df2b45d 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h

@@ -341,6 +341,10 @@ struct nvmet_req {
  	size_t			transfer_len;
  	size_t			metadata_len;
  
+	/* details to support polling */
+	struct request_queue	*queue;
+	int			op;
+
  	struct nvmet_port	*port;
  
  	void (*execute)(struct nvmet_req *req);

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 739d67985d93..43a0cc630bc7 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c

@@ -62,6 +62,12 @@ enum {
  	NVMET_TCP_F_INIT_FAILED = (1 << 0),
  };
  
+struct nvmet_tcp_devq {
+	u32				pend_cnt;
+	struct request_queue		*queue;
+	struct list_head		entry;
+};
+
  struct nvmet_tcp_cmd {
  	struct nvmet_tcp_queue		*queue;
  	struct nvmet_req		req;

@@ -82,6 +88,7 @@ struct nvmet_tcp_cmd {
  	struct kvec			*iov;
  	u32				flags;
  
+	struct nvmet_tcp_devq		*devq;
  	struct list_head		entry;
  	struct llist_node		lentry;
  

@@ -142,6 +149,9 @@ struct nvmet_tcp_queue {
  	int			idx;
  	struct list_head	queue_list;
  
+	/* ref to group subsys devq entry */
+	struct list_head	devq_list;
+
  	struct nvmet_tcp_cmd	connect;
  
  	struct page_frag_cache	pf_cache;

@@ -237,6 +247,42 @@ static inline int queue_cpu(struct nvmet_tcp_queue *queue)
  	return queue->sock->sk->sk_incoming_cpu;
  }
  
+static int nvmet_tcp_track_queue(struct nvmet_tcp_queue *queue)
+{
+	struct nvmet_tcp_devq *devq;
+	struct nvmet_req *req = &queue->cmd->req;
+
+	/* track only requests issued as poll requests */
+	if (req->queue == NULL)
+		return 0;
+
+	list_for_each_entry(devq, &queue->devq_list, entry) {
+		if (devq->queue == req->queue)
+			goto update;
+	}
+
+	devq = kzalloc(sizeof(*devq), GFP_KERNEL);
+	if (!devq)
+		return -ENOMEM;
+	list_add_tail(&devq->entry, &queue->devq_list);
+	devq->queue = req->queue;
+update:
+	devq->pend_cnt++;
+	queue->cmd->devq = devq;
+	return 0;
+}
+
+static void nvmet_tcp_free_dev_tracking(struct nvmet_tcp_queue *queue)
+{
+	struct nvmet_tcp_devq *devq;
+
+	while ((devq = list_first_entry_or_null(
+			&queue->devq_list, struct nvmet_tcp_devq, entry))) {
+		list_del_init(&devq->entry);
+		kfree(devq);
+	}
+}
+
  static inline u8 nvmet_tcp_hdgst_len(struct nvmet_tcp_queue *queue)
  {
  	return queue->hdr_digest ? NVME_TCP_DIGEST_LENGTH : 0;

@@ -479,6 +525,25 @@ static void nvmet_setup_response_pdu(struct nvmet_tcp_cmd *cmd)
  	}
  }
  
+static inline void nvmet_tcp_poll_init(struct nvmet_req *req)
+{
+	req->queue = NULL;
+	if (idle_poll_period)
+		req->op |= REQ_HIPRI;
+	else
+		req->op = 0;
+}