[PATCH 5/5] nvme: Add two-pass shutdown support

[Jeremy Allison]

This works with the two-pass shutdown mechanism setup for the PCI
drivers and participates to provide the shutdown_wait
method at the pci_driver structure level.

This patch changes the nvme shutdown() method to pass
down the NVME_PCI_DISABLE_SHUTDOWN_TWOPASS enum value instead
of NVME_PCI_DISABLE_SHUTDOWN. nvme_dev_disable() is changed
to call nvme_ctrl_shutdown_start() instead of nvme_disable_ctrl()
in this case.

nvme_ctrl_shutdown_start() sets the shutdown bit,
but does not wait for completion.

The nvme_shutdown_wait() callback is added to synchronously
wait for the NVME_CSTS_SHST_CMPLT bit meaning the nvme
device has shutdown.

This change speeds up the shutdown in a system which hosts
many controllers.

Based on work by Tanjore Suresh <tansuresh at google.com>

Signed-off-by: Jeremy Allison <jallison at ciq.com>
---
 drivers/nvme/host/pci.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 4dfc6258de07..5cf452651091 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2607,7 +2607,14 @@ static void nvme_dev_disable(struct nvme_dev *dev,
 
 	if (!dead && dev->ctrl.queue_count > 0) {
 		nvme_delete_io_queues(dev);
-		nvme_disable_ctrl(&dev->ctrl, shutdown);
+		/*
+		 * NVME_PCI_DISABLE_SHUTDOWN_TWOPASS requests shutdown
+		 * but doesn't wait for completion.
+		 */
+		if (shutdown_type == NVME_PCI_DISABLE_SHUTDOWN_TWOPASS)
+			nvme_ctrl_shutdown_start(&dev->ctrl);
+		else
+			nvme_disable_ctrl(&dev->ctrl, shutdown);
 		nvme_poll_irqdisable(&dev->queues[0]);
 	}
 	nvme_suspend_io_queues(dev);
@@ -2625,7 +2632,7 @@ static void nvme_dev_disable(struct nvme_dev *dev,
 	 * must flush all entered requests to their failed completion to avoid
 	 * deadlocking blk-mq hot-cpu notifier.
 	 */
-	if (shutdown) {
+	if (shutdown_type == NVME_PCI_DISABLE_SHUTDOWN) {
 		nvme_unquiesce_io_queues(&dev->ctrl);
 		if (dev->ctrl.admin_q && !blk_queue_dying(dev->ctrl.admin_q))
 			nvme_unquiesce_admin_queue(&dev->ctrl);
@@ -3128,7 +3135,32 @@ static void nvme_shutdown(struct pci_dev *pdev)
 {
 	struct nvme_dev *dev = pci_get_drvdata(pdev);
 
-	nvme_disable_prepare_reset(dev, NVME_PCI_DISABLE_SHUTDOWN);
+	nvme_disable_prepare_reset(dev, NVME_PCI_DISABLE_SHUTDOWN_TWOPASS);
+}
+
+static void nvme_shutdown_wait(struct pci_dev *pdev)
+{
+	struct nvme_dev *dev = pci_get_drvdata(pdev);
+
+	mutex_lock(&dev->shutdown_lock);
+	/*
+	 * Finish waiting for the shutdown request
+	 * initiated in nvme_shutdown() above using
+	 * NVME_PCI_DISABLE_SHUTDOWN_TWOPASS.
+	 */
+	nvme_wait_ready(&dev->ctrl, NVME_CSTS_SHST_MASK,
+			NVME_CSTS_SHST_CMPLT,
+			dev->ctrl.shutdown_timeout, "shutdown");
+	/*
+	 * The driver will not be starting up queues again if shutting down so
+	 * must flush all entered requests to their failed completion to avoid
+	 * deadlocking blk-mq hot-cpu notifier.
+	 */
+	nvme_unquiesce_io_queues(&dev->ctrl);
+	if (dev->ctrl.admin_q && !blk_queue_dying(dev->ctrl.admin_q))
+		nvme_unquiesce_admin_queue(&dev->ctrl);
+
+	mutex_unlock(&dev->shutdown_lock);
 }
 
 /*
@@ -3522,6 +3554,7 @@ static struct pci_driver nvme_driver = {
 	.probe		= nvme_probe,
 	.remove		= nvme_remove,
 	.shutdown	= nvme_shutdown,
+	.shutdown_wait	= nvme_shutdown_wait,
 	.driver		= {
 		.probe_type	= PROBE_PREFER_ASYNCHRONOUS,
 #ifdef CONFIG_PM_SLEEP
-- 
2.39.3