[PATCH 2/2] NVMe: Kill request queues on dead controllers

[Keith Busch]

This fixes device removal from waiting forever on a h/w queue that isn't
available. There are two parts for this:

First, the controller is shutdown after the disks are removed. This
allows del_gendisk to sync dirty pages in an orderly removal scenario.

Second, if the nvme controller is incapable of performing IO, kill the
request queue prior to deleting gendisks. This prevents del_gendisk
from waiting indefinitely to sync dirty pages when there controller is
no longer accepting new requests.

Reported-by: Sunad Bhandary <sunad.s at samsung.com>
Signed-off-by: Keith Busch <keith.busch at intel.com>
---
 drivers/block/nvme-core.c |   20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
index 85b8036..77aa061 100644
--- a/drivers/block/nvme-core.c
+++ b/drivers/block/nvme-core.c
@@ -2633,17 +2633,31 @@ static void nvme_dev_shutdown(struct nvme_dev *dev)
 		nvme_clear_queue(dev->queues[i]);
 }
 
+static inline bool nvme_io_incapable(struct nvme_dev *dev)
+{
+	return (!dev->bar || readl(&dev->bar->csts) == -1 ||
+						dev->online_queues < 2);
+}
+
 static void nvme_dev_remove(struct nvme_dev *dev)
 {
 	struct nvme_ns *ns;
 
+	/*
+	 * If controller is not IO capable, kill request queues prior to
+	 * deleting gendisks to prevent filesystem sync from blocking.
+	 */
+	bool kill = nvme_io_incapable(dev);
+
 	list_for_each_entry(ns, &dev->namespaces, list) {
+		if (kill && !blk_queue_dying(ns->queue))
+			blk_set_queue_dying(ns->queue);
 		if (ns->disk->flags & GENHD_FL_UP) {
 			if (blk_get_integrity(ns->disk))
 				blk_integrity_unregister(ns->disk);
 			del_gendisk(ns->disk);
 		}
-		if (!blk_queue_dying(ns->queue)) {
+		if (kill || !blk_queue_dying(ns->queue)) {
 			blk_mq_abort_requeue_list(ns->queue);
 			blk_cleanup_queue(ns->queue);
 		}
@@ -2879,8 +2893,8 @@ static void nvme_remove_disks(struct work_struct *ws)
 {
 	struct nvme_dev *dev = container_of(ws, struct nvme_dev, reset_work);
 
-	nvme_free_queues(dev, 1);
 	nvme_dev_remove(dev);
+	nvme_free_queues(dev, 1);
 }
 
 static int nvme_dev_resume(struct nvme_dev *dev)
@@ -3042,8 +3056,8 @@ static void nvme_remove(struct pci_dev *pdev)
 	pci_set_drvdata(pdev, NULL);
 	flush_work(&dev->probe_work);
 	flush_work(&dev->reset_work);
-	nvme_dev_shutdown(dev);
 	nvme_dev_remove(dev);
+	nvme_dev_shutdown(dev);
 	nvme_dev_remove_admin(dev);
 	device_destroy(nvme_class, MKDEV(nvme_char_major, dev->instance));
 	nvme_free_queues(dev, 0);
-- 
1.7.10.4