[PATCH 2/7] nvme: switch AEN processing to use blk_execute_rq_nowait

[Keith Busch]

On Mon, 21 Sep 2015, Christoph Hellwig wrote:
> +static int nvme_submit_aen(struct nvme_dev *dev)
> +{
> +	struct nvme_command c;
>
> 	memset(&c, 0, sizeof(c));
> 	c.common.opcode = nvme_admin_async_event;
> -	c.common.command_id = req->tag;
>
> -	blk_mq_free_request(req);
> -	__nvme_submit_cmd(nvmeq, &c);
> -	return 0;
> +	return nvme_submit_async_cmd(dev->admin_q, &c, ULONG_MAX, GFP_ATOMIC,
> +			true, aen_endio, NULL);
> }

AEN needs to release the request immediately. That's why it uses
a "reserved" tag because it is tracked by the driver instead of
the block layer: there is no guarantee the controller will ever
return it, which deadlocks blk-mq's hot cpu notification. See
1efccc9ddb98fd533169669160201b027562af7e for details.

Other than that, love the rest of the series.