linux-kernel - Re: [PATCH v8 01/11] block: make bdev_nr_zones and disk_zone

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Date:   Thu, 28 Jul 2022 11:54:03 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Pankaj Raghav <p.raghav@...sung.com>, hch@....de, axboe@...nel.dk,
        snitzer@...nel.org, Johannes.Thumshirn@....com
Cc:     matias.bjorling@....com, gost.dev@...sung.com,
        linux-kernel@...r.kernel.org, hare@...e.de,
        linux-block@...r.kernel.org, pankydev8@...il.com,
        bvanassche@....org, jaegeuk@...nel.org, dm-devel@...hat.com,
        linux-nvme@...ts.infradead.org,
        Luis Chamberlain <mcgrof@...nel.org>,
        Adam Manzanares <a.manzanares@...sung.com>
Subject: Re: [PATCH v8 01/11] block: make bdev_nr_zones and disk_zone_no
 generic for npo2 zsze

On 7/28/22 01:22, Pankaj Raghav wrote:
> Adapt bdev_nr_zones and disk_zone_no function so that it can

s/function/functions
s/it/they

> also work for non-power-of-2 zone sizes.
> 
> As the existing deployments of zoned devices had power-of-2

had power-of-2 assumption -> assume that a device zone size is a power of
2 number of sectors

Existing deployments still exist, so do not use the past tense please.

> 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@...nel.org>
> Reviewed-by: Adam Manzanares <a.manzanares@...sung.com>
> Reviewed-by: Hannes Reinecke <hare@...e.de>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> Reviewed-by: Bart Van Assche <bvanassche@....org>
> ---
>  block/blk-zoned.c      | 13 +++++++++----
>  include/linux/blkdev.h |  8 +++++++-
>  2 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index a264621d4905..dce9c95b4bcd 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -111,17 +111,22 @@ EXPORT_SYMBOL_GPL(__blk_req_zone_write_unlock);
>   * bdev_nr_zones - Get number of zones
>   * @bdev:	Target device
>   *
> - * Return the total number of zones of a zoned block device.  For a block
> - * device without zone capabilities, the number of zones is always 0.
> + * Return the total number of zones of a zoned block device, including the
> + * eventual small last zone if present. For a block device without zone
> + * capabilities, the number of zones is always 0.
>   */
>  unsigned int bdev_nr_zones(struct block_device *bdev)
>  {
>  	sector_t zone_sectors = bdev_zone_sectors(bdev);
> +	sector_t capacity = bdev_nr_sectors(bdev);
>  
>  	if (!bdev_is_zoned(bdev))
>  		return 0;
> -	return (bdev_nr_sectors(bdev) + zone_sectors - 1) >>
> -		ilog2(zone_sectors);
> +
> +	if (is_power_of_2(zone_sectors))
> +		return (capacity + zone_sectors - 1) >> ilog2(zone_sectors);
> +
> +	return DIV_ROUND_UP_SECTOR_T(capacity, zone_sectors);
>  }
>  EXPORT_SYMBOL_GPL(bdev_nr_zones);
>  
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index dccdf1551c62..85b832908f28 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -673,9 +673,15 @@ static inline unsigned int disk_nr_zones(struct gendisk *disk)
>  
>  static inline unsigned int disk_zone_no(struct gendisk *disk, sector_t sector)
>  {
> +	sector_t zone_sectors = disk->queue->limits.chunk_sectors;
> +
>  	if (!blk_queue_is_zoned(disk->queue))
>  		return 0;
> -	return sector >> ilog2(disk->queue->limits.chunk_sectors);
> +
> +	if (is_power_of_2(zone_sectors))
> +		return sector >> ilog2(zone_sectors);
> +
> +	return div64_u64(sector, zone_sectors);
>  }
>  
>  static inline bool disk_zone_is_seq(struct gendisk *disk, sector_t sector)


-- 
Damien Le Moal
Western Digital Research