nvme: fix use after free when disconnecting a reconnecting ctrl

A crash happens when trying to disconnect a reconnecting ctrl:

1) The network was cut off when the connection was just established,
scan work hang there waiting for some IOs complete. Those I/Os were
retried because we return BLK_STS_RESOURCE to blk in reconnecting.
2) After a while, I tried to disconnect this connection. This
procedure also hangs because it tried to obtain ctrl->scan_lock.
It should be noted that now we have switched the controller state
to NVME_CTRL_DELETING.
3) In nvme_check_ready(), we always return true when ctrl->state is
NVME_CTRL_DELETING, so those retrying I/Os were issued to the bottom
device which was already freed.

To fix this, when ctrl->state is NVME_CTRL_DELETING, issue cmd to bottom
device only when queue state is live. If not, return host path error to
the block layer

Signed-off-by: Ruozhu Li <[e-mail]>
Reviewed-by: Sagi Grimberg <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>

drivers/nvme/host/core.c

···
 		struct request *rq)
 {
 	if (ctrl->state != NVME_CTRL_DELETING_NOIO &&
+	    ctrl->state != NVME_CTRL_DELETING &&
 	    ctrl->state != NVME_CTRL_DEAD &&
 	    !test_bit(NVME_CTRL_FAILFAST_EXPIRED, &ctrl->flags) &&
 	    !blk_noretry_request(rq) && !(rq->cmd_flags & REQ_NVME_MPATH))

drivers/nvme/host/nvme.h

···
 		return true;
 	if (ctrl->ops->flags & NVME_F_FABRICS &&
 	    ctrl->state == NVME_CTRL_DELETING)
-		return true;
+		return queue_live;
 	return __nvme_check_ready(ctrl, rq, queue_live);
 }
 int nvme_submit_sync_cmd(struct request_queue *q, struct nvme_command *cmd,