[PATCHv3 4/5] NVMe: IO queue deletion re-write

[Christoph Hellwig]

This is my counter-suggestion to the requeue abuse:

simply do two passes of your algorithm, one for the SQs, one for the
CQs.  Patch relative to the whole series below:

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 3f536c2..4f3d1e3 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -154,7 +154,6 @@ struct nvme_queue {
 	u16 qid;
 	u8 cq_phase;
 	u8 cqe_seen;
-	struct nvme_delete_queue dq;
 };
 
 /*
@@ -1587,57 +1586,52 @@ static void nvme_dev_scan(struct work_struct *work)
 
 static void nvme_del_queue_end(struct request *req, int error)
 {
-	unsigned long flags;
 	struct nvme_queue *nvmeq = req->end_io_data;
 
 	blk_mq_free_request(req);
-
-	spin_lock_irqsave(&nvmeq->q_lock, flags);
-	nvme_process_cq(nvmeq);
-	spin_unlock_irqrestore(&nvmeq->q_lock, flags);
-
 	complete(&nvmeq->dev->ioq_wait);
 }
 
-static void nvme_del_sq_end(struct request *req, int error)
+static void nvme_del_cq_end(struct request *req, int error)
 {
 	struct nvme_queue *nvmeq = req->end_io_data;
 
-	if (error) {
-		nvme_del_queue_end(req, error);
-		return;
-	}
+	if (!error) {
+		unsigned long flags;
 
-	nvmeq->dq.opcode = nvme_admin_delete_cq;
-	req->end_io = nvme_del_queue_end;
+		spin_lock_irqsave(&nvmeq->q_lock, flags);
+		nvme_process_cq(nvmeq);
+		spin_unlock_irqrestore(&nvmeq->q_lock, flags);
+	}
 
-	/* Must requeue. This callback occurs in irq w/ q_lock held */
-	nvme_requeue_req(req);
+	nvme_del_queue_end(req, error);
 }
 
-static int nvme_delete_queue(struct nvme_queue *nvmeq, struct request_queue *q)
+static int nvme_delete_queue(struct nvme_queue *nvmeq, u8 opcode)
 {
+	struct request_queue *q = nvmeq->dev->ctrl.admin_q;
 	struct request *req;
+	struct nvme_command cmd;
 
-	req = nvme_alloc_request(q, (struct nvme_command *)&nvmeq->dq,
-							BLK_MQ_REQ_NOWAIT);
+	memset(&cmd, 0, sizeof(cmd));
+	cmd.delete_queue.opcode = nvme_admin_delete_sq;
+	cmd.delete_queue.qid = cpu_to_le16(nvmeq->qid);
+
+	req = nvme_alloc_request(q, &cmd, BLK_MQ_REQ_NOWAIT);
 	if (IS_ERR(req))
 		return PTR_ERR(req);
 
-	memset(&nvmeq->dq, 0, sizeof(nvmeq->dq));
-	nvmeq->dq.opcode = nvme_admin_delete_sq;
-	nvmeq->dq.qid = cpu_to_le16(nvmeq->qid);
-
-	req->end_io_data = nvmeq;
 	req->timeout = ADMIN_TIMEOUT;
+	req->end_io_data = nvmeq;
 
-	blk_execute_rq_nowait(q, NULL, req, false, nvme_del_sq_end);
+	blk_execute_rq_nowait(q, NULL, req, false,
+			opcode == nvme_admin_delete_cq ?
+				nvme_del_cq_end : nvme_del_queue_end);
 	return 0;
 }
 
-static void nvme_disable_io_queues(struct nvme_dev *dev)
+static int nvme_disable_io_queues(struct nvme_dev *dev, u8 opcode)
 {
-	struct request_queue *q = dev->ctrl.admin_q;
 	int i = dev->queue_count - 1, sent = 0;
 	unsigned long timeout;
 
@@ -1648,17 +1642,19 @@ static void nvme_disable_io_queues(struct nvme_dev *dev)
 		struct nvme_queue *nvmeq = dev->queues[i];
 
 		nvme_suspend_queue(nvmeq);
-		if (nvme_delete_queue(nvmeq, q))
+		if (nvme_delete_queue(nvmeq, opcode))
 			break;
 		++sent;
 	}
 	while (sent--) {
 		timeout = wait_for_completion_io_timeout(&dev->ioq_wait, timeout);
 		if (timeout == 0)
-			return;
+			return -EIO;
 		if (i)
 			goto retry;
 	}
+
+	return 0;
 }
 
 /*
@@ -1834,7 +1830,8 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
 			nvme_suspend_queue(nvmeq);
 		}
 	} else {
-		nvme_disable_io_queues(dev);
+		if (!nvme_disable_io_queues(dev, nvme_admin_delete_sq))
+			nvme_disable_io_queues(dev, nvme_admin_delete_cq);
 		nvme_disable_admin_queue(dev, shutdown);
 	}
 	nvme_dev_unmap(dev);