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Date:   Tue, 3 May 2022 09:37:57 -0700
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Subject: Re: [PATCH 01/16] block: make blkdev_nr_zones and blk_queue_zone_no
 generic for npo2 zsze
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To:     Pankaj Raghav <p.raghav@samsung.com>, jaegeuk@kernel.org,
        axboe@kernel.dk, snitzer@kernel.org, hch@lst.de, mcgrof@kernel.org,
        naohiro.aota@wdc.com, sagi@grimberg.me,
        damien.lemoal@opensource.wdc.com, dsterba@suse.com,
        johannes.thumshirn@wdc.com
Cc:     linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
        clm@fb.com, gost.dev@samsung.com, chao@kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, josef@toxicpanda.com,
        jonathan.derrick@linux.dev, agk@redhat.com, kbusch@kernel.org,
        kch@nvidia.com, linux-nvme@lists.infradead.org,
        dm-devel@redhat.com, jiangbo.365@bytedance.com,
        linux-fsdevel@vger.kernel.org, matias.bjorling@wdc.com,
        linux-block@vger.kernel.org
References: <20220427160255.300418-1-p.raghav@samsung.com>
 <CGME20220427160257eucas1p21fb58d0129376a135fdf0b9c2fe88895@eucas1p2.samsung.com>
 <20220427160255.300418-2-p.raghav@samsung.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <20220427160255.300418-2-p.raghav@samsung.com>
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Precedence: bulk

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.