Re: blk-mq: don't clear RQF_MQ_INFLIGHT in blk_mq_rq_ctx_init()

[Jens Axboe <axboe@kernel.dk>]

On 1/14/18 10:43 AM, Mike Snitzer wrote:
> On Sun, Jan 14 2018 at 12:38pm -0500,
> Jens Axboe <axboe@kernel.dk> wrote:
> 
>> On 1/13/18 10:49 AM, Ming Lei wrote:
>>> In case of no IO scheduler, RQF_MQ_INFLIGHT is set in blk_mq_rq_ctx_init(),
>>> but 7c3fb70f0341 clears it mistakenly, so fix it.
>>
>> Oops yeah, that's my bad. However, I think the below fix is cleaner
>> and avoids a conditional.
>>
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index b3b2003b7429..c8f62e6be6b6 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -269,13 +269,14 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
>>  {
>>  	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
>>  	struct request *rq = tags->static_rqs[tag];
>> +	req_flags_t rq_flags = 0;
>>  
>>  	if (data->flags & BLK_MQ_REQ_INTERNAL) {
>>  		rq->tag = -1;
>>  		rq->internal_tag = tag;
>>  	} else {
>>  		if (blk_mq_tag_busy(data->hctx)) {
>> -			rq->rq_flags = RQF_MQ_INFLIGHT;
>> +			rq_flags = RQF_MQ_INFLIGHT;
>>  			atomic_inc(&data->hctx->nr_active);
>>  		}
>>  		rq->tag = tag;
>> @@ -286,7 +287,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
>>  	/* csd/requeue_work/fifo_time is initialized before use */
>>  	rq->q = data->q;
>>  	rq->mq_ctx = data->ctx;
>> -	rq->rq_flags = 0;
>> +	rq->rq_flags = rq_flags;
>>  	rq->cpu = -1;
>>  	rq->cmd_flags = op;
>>  	if (data->flags & BLK_MQ_REQ_PREEMPT)
> 
> Yeap, looks good.
> 
> Reviewed-by:  Mike Snitzer <snitzer@redhat.com>
> 
> Defintely need this fix, without it all my dm-mpath testing hangs

Yeah, pretty unfortunate... I've applied it and pushed it out.

-- 
Jens Axboe