Re: [PATCH 01/16] block: make blkdev_nr_zones and blk_queue_zone_no generic for npo2 zsze

Bart Van Assche
2022-05-03T16:38:06Z

On 4/27/22 09:02, Pankaj Raghav wrote:
> Adapt blkdev_nr_zones and blk_queue_zone_no function so that it can
> also work for non-power-of-2 zone sizes.
>
> As the existing deployments of zoned devices had power-of-2
> assumption, power-of-2 optimized calculation is kept for those devices.
>
> There are no direct hot paths modified and the changes just
> introduce one new branch per call.
>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
> block/blk-zoned.c | 8 +++++++-
> include/linux/blkdev.h | 8 +++++++-
> 2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 38cd840d8838..1dff4a8bd51d 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -117,10 +117,16 @@ EXPORT_SYMBOL_GPL(__blk_req_zone_write_unlock);
> unsigned int blkdev_nr_zones(struct gendisk *disk)
> {
> sector_t zone_sectors = blk_queue_zone_sectors(disk->queue);
> + sector_t capacity = get_capacity(disk);
>
> if (!blk_queue_is_zoned(disk->queue))
> return 0;
> - return (get_capacity(disk) + zone_sectors - 1) >> ilog2(zone_sectors);
> +
> + if (is_power_of_2(zone_sectors))
> + return (capacity + zone_sectors - 1) >>
> + ilog2(zone_sectors);
> +
> + return div64_u64(capacity + zone_sectors - 1, zone_sectors);
> }
> EXPORT_SYMBOL_GPL(blkdev_nr_zones);

Does anyone need support for more than 4 billion sectors per zone? If
not, do_div() should be sufficient.

> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 60d016138997..c4e4c7071b7b 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -665,9 +665,15 @@ static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
> static inline unsigned int blk_queue_zone_no(struct request_queue *q,
> sector_t sector)
> {
> + sector_t zone_sectors = blk_queue_zone_sectors(q);
> +
> if (!blk_queue_is_zoned(q))
> return 0;
> - return sector >> ilog2(q->limits.chunk_sectors);
> +
> + if (is_power_of_2(zone_sectors))
> + return sector >> ilog2(zone_sectors);
> +
> + return div64_u64(sector, zone_sectors);
> }

Same comment here.

Thanks,

Bart.