nvme: stop aer posting if controller state not live

If an nvme async_event command completes, in most cases, a new async event is posted. However, if the controller enters a resetting or reconnecting state, there is nothing to block the scheduled work element from posting the async event again. Nor are there calls from the transport to stop async events when an association dies.

In the case of FC, where the association is torn down, the aer must be aborted on the FC link and completes through the normal job completion path. Thus the terminated async event ends up being rescheduled even though the controller isn't in a valid state for the aer, and the reposting gets the transport into a partially torn down data structure.

It's possible to hit the scenario on rdma, although much less likely due to an aer completing right as the association is terminated and as the association teardown reclaims the blk requests via nvme_cancel_request() so its immediate, not a link-related action like on FC.

Fix by putting controller state checks in both the async event completion routine where it schedules the async event and in the async event work routine before it calls into the transport. It's effectively a "stop_async_events()" behavior. The transport, when it creates a new association with the subsystem will transition the state back to live and is already restarting the async event posting.

---
v2:
rework if test into while stmt

 drivers/nvme/host/core.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

index 90d09067a82a..fd1f489d4f9a 100644
@@ -2588,7 +2588,7 @@ static void nvme_async_event_work(struct work_struct *work)
 		container_of(work, struct nvme_ctrl, async_event_work);
 
 	spin_lock_irq(&ctrl->lock);
-	while (ctrl->event_limit > 0) {
+	while (ctrl->state == NVME_CTRL_LIVE && ctrl->event_limit > 0) {
 		int aer_idx = --ctrl->event_limit;
 
 		spin_unlock_irq(&ctrl->lock);

@@ -2667,7 +2667,12 @@ void nvme_complete_async_event(struct nvme_ctrl *ctrl, __le16 status,
 		union nvme_result *res)
 {
 	u32 result = le32_to_cpu(res->u32);
-	bool done = true;
+	bool done = true, live = true;
+
+	spin_lock_irq(&ctrl->lock);
+	if (unlikely(ctrl->state != NVME_CTRL_LIVE))
+		live = false;
+	spin_unlock_irq(&ctrl->lock);
 
 	switch (le16_to_cpu(status) >> 1) {
 	case NVME_SC_SUCCESS:

@@ -2675,7 +2680,8 @@ void nvme_complete_async_event(struct nvme_ctrl *ctrl, __le16 status,
 		/*FALLTHRU*/
 	case NVME_SC_ABORT_REQ:
 		++ctrl->event_limit;
-		queue_work(nvme_wq, &ctrl->async_event_work);
+		if (live)
+			schedule_work(&ctrl->async_event_work);
 		break;
 	default:
 		break;

2.13.1