linux-kernel - Re: [PATCH v2] block: ublk: enable zoned storage support

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Date:   Tue, 28 Feb 2023 00:20:35 +0900
From:   Minwoo Im <minwoo.im.dev@...il.com>
To:     Andreas Hindborg <nmi@...aspace.dk>
Cc:     linux-block@...r.kernel.org,
        Andreas Hindborg <a.hindborg@...sung.com>,
        Hans Holmberg <Hans.Holmberg@....com>,
        Matias Bjorling <Matias.Bjorling@....com>,
        Niklas Cassel <Niklas.Cassel@....com>,
        kernel test robot <lkp@...el.com>,
        Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] block: ublk: enable zoned storage support

On 23-02-24 21:05:01, Andreas Hindborg wrote:
> +static int ublk_report_zones(struct gendisk *disk, sector_t sector,
> +			     unsigned int nr_zones, report_zones_cb cb,
> +			     void *data)
> +{
> +	struct ublk_device *ub;
> +	unsigned int zone_size;
> +	unsigned int first_zone;
> +	int ret = 0;
> +
> +	ub = disk->private_data;
> +
> +	if (!(ub->dev_info.flags & UBLK_F_ZONED))
> +		return -EINVAL;
> +
> +	zone_size = disk->queue->limits.chunk_sectors;
> +	first_zone = sector >> ilog2(zone_size);
> +	nr_zones = min(ub->ub_disk->nr_zones - first_zone, nr_zones);
> +
> +	for (unsigned int i = 0; i < nr_zones; i++) {
> +		struct request *req;
> +		blk_status_t status;
> +		struct blk_zone info = {0};
> +
> +		req = blk_mq_alloc_request(disk->queue, REQ_OP_DRV_IN, 0);
> +
> +		if (IS_ERR(req)) {
> +			ret = PTR_ERR(req);
> +			goto out;
> +		}

Can we just return directly just like above (-EINVAL)?

if (IS_ERR(req))
	return PTR_ERR(req);

> +
> +		req->__sector = sector;
> +
> +		ret = blk_rq_map_kern(disk->queue, req, &info, sizeof(info),
> +				      GFP_KERNEL);
> +
> +		if (ret)
> +			goto out;

If we really have to use goto here, then I think we have choices:
put blk_mq_free_request(req); here or put it to the out: area.

> +
> +		status = blk_execute_rq(req, 0);
> +		ret = blk_status_to_errno(status);
> +		if (ret)
> +			goto out;
> +
> +		blk_mq_free_request(req);
> +
> +		ret = cb(&info, i, data);
> +		if (ret)
> +			goto out;
> +
> +		/* A zero length zone means don't ask for more zones */
> +		if (!info.len) {
> +			nr_zones = i;
> +			break;
> +		}
> +
> +		sector += zone_size;
> +	}
> +	ret = nr_zones;
> +
> + out:
> +	return ret;
> +}