Re: [PATCH v9 10/12] block: don't check blk_rq_is_passthrough() in blk_do_io_stat()

From: Christoph Hellwig
Date: Thu Oct 10 2019 - 06:05:43 EST


> @@ -319,7 +319,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
> rq->cmd_flags = op;
> if (data->flags & BLK_MQ_REQ_PREEMPT)
> rq->rq_flags |= RQF_PREEMPT;
> - if (blk_queue_io_stat(data->q))
> + if (blk_queue_io_stat(data->q) && !blk_rq_is_passthrough(rq))
> rq->rq_flags |= RQF_IO_STAT;

This needs a comment why we don't account passthrough requests by
default. And I'm really curious about the answer, because I don't
know it myself.

> * a) it's attached to a gendisk, and
> * b) the queue had IO stats enabled when this request was started, and
> - * c) it's a file system request
> + * c) it's a file system request (RQF_IO_STAT will not be set otherwise)

c) should just go away now based on your changes.

> static inline bool blk_do_io_stat(struct request *rq)
> {
> return rq->rq_disk &&
> - (rq->rq_flags & RQF_IO_STAT) &&
> - !blk_rq_is_passthrough(rq);
> + (rq->rq_flags & RQF_IO_STAT);

The check can be collapsed onto a single line now.