nvme-pci: introduce RECONNECTING state to mark initializing procedure

After Sagi's commit (nvme-rdma: fix concurrent reset and reconnect),
both nvme-fc/rdma have following pattern:
RESETTING    - quiesce blk-mq queues, teardown and delete queues/
               connections, clear out outstanding IO requests...
RECONNECTING - establish new queues/connections and some other
               initializing things.
Introduce RECONNECTING to nvme-pci transport to do the same mark.
Then we get a coherent state definition among nvme pci/rdma/fc
transports.

Suggested-by: James Smart <james.smart@broadcom.com>
Reviewed-by: James Smart <james.smart@broadcom.com>
Reviewed-by: Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -260,7 +260,7 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
 	switch (new_state) {
 	case NVME_CTRL_ADMIN_ONLY:
 		switch (old_state) {
-		case NVME_CTRL_RESETTING:
+		case NVME_CTRL_RECONNECTING:
 			changed = true;
 			/* FALLTHRU */
 		default:

drivers/nvme/host/pci.c

@@ -1140,9 +1140,14 @@ static bool nvme_should_reset(struct nvme_dev *dev, u32 csts)
 	 */
 	bool nssro = dev->subsystem && (csts & NVME_CSTS_NSSRO);
 
-	/* If there is a reset ongoing, we shouldn't reset again. */
-	if (dev->ctrl.state == NVME_CTRL_RESETTING)
+	/* If there is a reset/reinit ongoing, we shouldn't reset again. */
+	switch (dev->ctrl.state) {
+	case NVME_CTRL_RESETTING:
+	case NVME_CTRL_RECONNECTING:
 		return false;
+	default:
+		break;
+	}
 
 	/* We shouldn't reset unless the controller is on fatal error state
 	 * _or_ if we lost the communication with it.
@@ -2284,6 +2289,16 @@ static void nvme_reset_work(struct work_struct *work)
 	if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
 		nvme_dev_disable(dev, false);
 
+	/*
+	 * Introduce RECONNECTING state from nvme-fc/rdma transports to mark the
+	 * initializing procedure here.
+	 */
+	if (!nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_RECONNECTING)) {
+		dev_warn(dev->ctrl.device,
+			"failed to mark controller RECONNECTING\n");
+		goto out;
+	}
+
 	result = nvme_pci_enable(dev);
 	if (result)
 		goto out;