UBUNTU: SAUCE: nvme: Don't suspend admin queue that wasn't created

Pending 4.8-rc merge.
BugLink: http://bugs.launchpad.net/bugs/1602724

This fixes a regression in my previous commit c21377f8 ("nvme:
Suspend all queues before deletion"), which provoked an Oops in the
removal path when removing a device that became IO incapable very early
at probe (i.e. after a failed EEH recovery).

Turns out, if the error occurred very early at the probe path, before
even configuring the admin queue, we might try to suspend the
uninitialized admin queue, accessing bad memory.

Fixes: c21377f8 ("nvme: Suspend all queues before deletion")
Signed-off-by: Gabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Reviewed-by: Jay Freyensee <james_p_freyensee@linux.intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/nvme/host/pci.c

@@ -1817,7 +1817,12 @@ static void nvme_dev_disable(struct nvme_dev *dev, bool shutdown)
 		nvme_suspend_queue(dev->queues[i]);
 
 	if (csts & NVME_CSTS_CFS || !(csts & NVME_CSTS_RDY)) {
-		nvme_suspend_queue(dev->queues[0]);
+		/* A device might become IO incapable very soon during
+		 * probe, before the admin queue is configured. Thus,
+		 * queue_count can be 0 here.
+		 */
+		if (dev->queue_count)
+			nvme_suspend_queue(dev->queues[0]);
 	} else {
 		nvme_disable_io_queues(dev);
 		nvme_disable_admin_queue(dev, shutdown);