[PATCH 1/2] block: add request polling helper

[Christoph Hellwig]

> +int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, struct io_comp_batch *iob,

It would be nice to fix the overly long line while you're at it.

> +		unsigned int flags)
> +{
> +	return blk_hctx_poll(q, blk_qc_to_hctx(q, cookie), iob, flags);
> +}

But looking at the two callers of blk_mq_poll, shouldn't one use
rq->mq_hctx to get the hctx anyway instead of doing repeated
blk_qc_to_hctx in the polling loop?  We could then just open code
blk_qc_to_hctx in the remaining one.

The rest looks good to me.