Re: [PATCH v8 04/11] block: Introduce REQ_OP_ZONE_APPEND

[Bart Van Assche <bvanassche@acm.org>]

On 2020-04-27 04:31, Johannes Thumshirn wrote:
> +/*
> + * Check write append to a zoned block device.
> + */
> +static inline blk_status_t blk_check_zone_append(struct request_queue *q,
> +						 struct bio *bio)
> +{
> +	sector_t pos = bio->bi_iter.bi_sector;
> +	int nr_sectors = bio_sectors(bio);
> +
> +	/* Only applicable to zoned block devices */
> +	if (!blk_queue_is_zoned(q))
> +		return BLK_STS_NOTSUPP;
> +
> +	/* The bio sector must point to the start of a sequential zone */
> +	if (pos & (blk_queue_zone_sectors(q) - 1) ||
> +	    !blk_queue_zone_is_seq(q, pos))
> +		return BLK_STS_IOERR;
> +
> +	/*
> +	 * Not allowed to cross zone boundaries. Otherwise, the BIO will be
> +	 * split and could result in non-contiguous sectors being written in
> +	 * different zones.
> +	 */
> +	if (blk_queue_zone_no(q, pos) != blk_queue_zone_no(q, pos + nr_sectors))
> +		return BLK_STS_IOERR;
> +
> +	/* Make sure the BIO is small enough and will not get split */
> +	if (nr_sectors > q->limits.max_zone_append_sectors)
> +		return BLK_STS_IOERR;
> +
> +	bio->bi_opf |= REQ_NOMERGE;
> +
> +	return BLK_STS_OK;
> +}

Since the above function has not changed compared to v7, I will repeat
my question about this function. Since 'pos' refers to the start of a
zone, is the "blk_queue_zone_no(q, pos) != blk_queue_zone_no(q, pos +
nr_sectors)" check identical to nr_sectors < q->limits.chunk_sectors?
Since q->limits.max_zone_append_sectors is guaranteed to be less than or
equal to the size of a zone, does that mean that the check
"blk_queue_zone_no(q, pos) != blk_queue_zone_no(q, pos + nr_sectors)" is
superfluous?

Thanks,

Bart.