Re: [PATCH V8 08/11] block: add blk_end_flush_machinery

[Christoph Hellwig <hch@xxxxxx>]

On Fri, Apr 24, 2020 at 06:23:48PM +0800, Ming Lei wrote:
> +/* complete requests which just requires one flush command */
> +static void blk_complete_flush_requests(struct blk_flush_queue *fq,
> +		struct list_head *flush_list)
> +{
> +	struct block_device *bdev;
> +	struct request *rq;
> +	int error = -ENXIO;
> +
> +	if (list_empty(flush_list))
> +		return;
> +
> +	rq = list_first_entry(flush_list, struct request, queuelist);
> +
> +	/* Send flush via one active hctx so we can move on */
> +	bdev = bdget_disk(rq->rq_disk, 0);
> +	if (bdev) {
> +		error = blkdev_issue_flush(bdev, GFP_KERNEL, NULL);
> +		bdput(bdev);
> +	}

FYI, we don't really need the bdev to send a bio anymore, this could just
do:

	bio = bio_alloc(GFP_KERNEL, 0); // XXX: shouldn't this be GFP_NOIO??
	bio->bi_disk = rq->rq_disk;
	bio->bi_partno = 0;
	bio_associate_blkg(bio); // XXX: actually, shouldn't this come from rq?
	bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
	error = submit_bio_wait(bio);
	bio_put(bio);