NVMe: Fix reset/remove race

This fixes a scenario where device is present and being reset, but a request to unbind the driver occurs.

A previous patch series addressing a device failure removal scenario flushed reset_work after controller disable to unblock reset_work waiting on a completion that wouldn't occur. This isn't safe as-is. The broken scenario can potentially be induced with:

  modprobe nvme && modprobe -r nvme

To fix, the reset work is flushed immediately after setting the controller removing flag, and any subsequent reset will not proceed with controller initialization if the flag is set.

The controller status must be polled while active, so the watchdog timer is also left active until the controller is disabled to cleanup requests that may be stuck during namespace removal.

---
v1->v2:
Removed the untested change on IO timeout handling that skipped queueing reset work.

 drivers/nvme/host/pci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index 24ccda3..660ec84 100644
@@ -1859,6 +1859,9 @@ static void nvme_reset_work(struct work_struct *work)
 	if (dev->ctrl.ctrl_config & NVME_CC_ENABLE)
 		nvme_dev_disable(dev, false);
 
+	if (test_bit(NVME_CTRL_REMOVING, &dev->flags))
+		goto out;
+
 	set_bit(NVME_CTRL_RESETTING, &dev->flags);
 
 	result = nvme_pci_enable(dev);

@@ -2078,11 +2081,10 @@ static void nvme_remove(struct pci_dev *pdev)
 {
 	struct nvme_dev *dev = pci_get_drvdata(pdev);
 
-	del_timer_sync(&dev->watchdog_timer);
-
 	set_bit(NVME_CTRL_REMOVING, &dev->flags);
 	pci_set_drvdata(pdev, NULL);
 	flush_work(&dev->async_work);
+	flush_work(&dev->reset_work);
 	flush_work(&dev->scan_work);
 	nvme_remove_namespaces(&dev->ctrl);
 	nvme_uninit_ctrl(&dev->ctrl);

2.7.2

Looks fine,

Added, thanks Keith.

Jens Axboe