Re: [PATCH v13] blk-mq: Rework blk-mq timeout handling again

[Keith Busch <keith.busch@intel.com>]

On Tue, May 22, 2018 at 09:25:15AM -0700, Bart Van Assche wrote:
> @@ -848,13 +843,22 @@ static void blk_mq_rq_timed_out(struct request *req, bool reserved)
>  	case BLK_EH_RESET_TIMER:
> +		blk_mq_add_timer(req);
>  		/*
> +		 * The loop is for the unlikely case of a race with the
> +		 * completion code. There is no need to reset the deadline
> +		 * if the transition to the in-flight state fails because
> +		 * the deadline only matters in the in-flight state.
>  		 */
> -		blk_mq_rq_update_aborted_gstate(req, 0);
> -		blk_add_timer(req);
> +		while (true) {
> +			if (blk_mq_change_rq_state(req, MQ_RQ_TIMED_OUT,
> +						   MQ_RQ_IN_FLIGHT))
> +				break;
> +			if (blk_mq_rq_state(req) == MQ_RQ_COMPLETE) {
> +				__blk_mq_complete_request(req);
> +				break;
> +			}
> +		}

I'm having some trouble triggering this case where the state is already
MQ_RQ_COMPLETE, so I'm just trying to figure this out through inspection.

It looks like the new blk_mq_complete_request() already called
__blk_mq_complete_request() when it gets the state to MQ_RQ_COMPLETE,
so doing that again completes it a second time.