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Date:   Tue, 24 May 2022 07:21:30 +0200
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Subject: Re: [PATCH v5 3/7] nvme: zns: Allow ZNS drives that have
 non-power_of_2 zone size
Content-Language: en-US
To:     Pankaj Raghav <p.raghav@samsung.com>, axboe@kernel.dk, hch@lst.de,
        snitzer@redhat.com, damien.lemoal@opensource.wdc.com,
        Johannes.Thumshirn@wdc.com
Cc:     linux-nvme@lists.infradead.org, dm-devel@redhat.com,
        dsterba@suse.com, jiangbo.365@bytedance.com,
        linux-kernel@vger.kernel.org, gost.dev@samsung.com,
        linux-block@vger.kernel.org, jaegeuk@kernel.org,
        Luis Chamberlain <mcgrof@kernel.org>
References: <20220523161601.58078-1-p.raghav@samsung.com>
 <CGME20220523161607eucas1p2b6245eafb81dee3e2efbec3ab86a854d@eucas1p2.samsung.com>
 <20220523161601.58078-4-p.raghav@samsung.com>
From:   Hannes Reinecke <hare@suse.de>
In-Reply-To: <20220523161601.58078-4-p.raghav@samsung.com>
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On 5/23/22 18:15, Pankaj Raghav wrote:
> Remove the condition which disallows non-power_of_2 zone size ZNS drive
> to be updated and use generic method to calculate number of zones
> instead of relying on log and shift based calculation on zone size.
> 
> The power_of_2 calculation has been replaced directly with generic
> calculation without special handling. Both modified functions are not
> used in hot paths, they are only used during initialization &
> revalidation of the ZNS device.
> 
> As rounddown macro from math.h does not work for 32 bit architectures,
> round down operation is open coded.
> 
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Reviewed by: Adam Manzanares <a.manzanares@samsung.com>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
>   drivers/nvme/host/zns.c | 21 ++++++++++++---------
>   1 file changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
> index 9f81beb4df4e..d92f937d5cb9 100644
> --- a/drivers/nvme/host/zns.c
> +++ b/drivers/nvme/host/zns.c
> @@ -101,13 +101,6 @@ int nvme_update_zone_info(struct nvme_ns *ns, unsigned lbaf)
>   	}
>   
>   	ns->zsze = nvme_lba_to_sect(ns, le64_to_cpu(id->lbafe[lbaf].zsze));
> -	if (!is_power_of_2(ns->zsze)) {
> -		dev_warn(ns->ctrl->device,
> -			"invalid zone size:%llu for namespace:%u\n",
> -			ns->zsze, ns->head->ns_id);
> -		status = -ENODEV;
> -		goto free_data;
> -	}
>   
>   	blk_queue_set_zoned(ns->disk, BLK_ZONED_HM);
>   	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
> @@ -128,8 +121,13 @@ static void *nvme_zns_alloc_report_buffer(struct nvme_ns *ns,
>   	const size_t min_bufsize = sizeof(struct nvme_zone_report) +
>   				   sizeof(struct nvme_zone_descriptor);
>   
> +	/*
> +	 * Division is used to calculate nr_zones with no special handling
> +	 * for power of 2 zone sizes as this function is not invoked in a
> +	 * hot path
> +	 */
>   	nr_zones = min_t(unsigned int, nr_zones,
> -			 get_capacity(ns->disk) >> ilog2(ns->zsze));
> +			 div64_u64(get_capacity(ns->disk), ns->zsze));
>   
>   	bufsize = sizeof(struct nvme_zone_report) +
>   		nr_zones * sizeof(struct nvme_zone_descriptor);
> @@ -182,6 +180,7 @@ int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector,
>   	int ret, zone_idx = 0;
>   	unsigned int nz, i;
>   	size_t buflen;
> +	u64 remainder = 0;
>   
>   	if (ns->head->ids.csi != NVME_CSI_ZNS)
>   		return -EINVAL;
> @@ -197,7 +196,11 @@ int nvme_ns_report_zones(struct nvme_ns *ns, sector_t sector,
>   	c.zmr.zrasf = NVME_ZRASF_ZONE_REPORT_ALL;
>   	c.zmr.pr = NVME_REPORT_ZONE_PARTIAL;
>   
> -	sector &= ~(ns->zsze - 1);
> +	/*
> +	 * Round down the sector value to the nearest zone start
> +	 */
> +	div64_u64_rem(sector, ns->zsze, &remainder);
> +	sector -= remainder;
>   	while (zone_idx < nr_zones && sector < get_capacity(ns->disk)) {
>   		memset(report, 0, buflen);
>   
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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