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Date:   Mon, 9 May 2022 13:06:18 +0200
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Subject: Re: [PATCH v3 10/11] null_blk: allow non power of 2 zoned devices
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To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        <jaegeuk@kernel.org>, <hare@suse.de>, <dsterba@suse.com>,
        <axboe@kernel.dk>, <hch@lst.de>, <snitzer@kernel.org>
CC:     Chris Mason <clm@fb.com>, Josef Bacik <josef@toxicpanda.com>,
        <bvanassche@acm.org>, <linux-fsdevel@vger.kernel.org>,
        <matias.bjorling@wdc.com>, Jens Axboe <axboe@fb.com>,
        <gost.dev@samsung.com>, <jonathan.derrick@linux.dev>,
        <jiangbo.365@bytedance.com>, <linux-nvme@lists.infradead.org>,
        <dm-devel@redhat.com>, Naohiro Aota <naohiro.aota@wdc.com>,
        <linux-kernel@vger.kernel.org>,
        Johannes Thumshirn <jth@kernel.org>,
        Sagi Grimberg <sagi@grimberg.me>,
        Alasdair Kergon <agk@redhat.com>,
        <linux-block@vger.kernel.org>, Chaitanya Kulkarni <kch@nvidia.com>,
        Keith Busch <kbusch@kernel.org>, <linux-btrfs@vger.kernel.org>,
        Luis Chamberlain <mcgrof@kernel.org>
From:   Pankaj Raghav <p.raghav@samsung.com>
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        <20220506081105.29134-11-p.raghav@samsung.com>
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Precedence: bulk


>> diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
>> index 5cb4c92cd..ed9a58201 100644
>> --- a/drivers/block/null_blk/main.c
>> +++ b/drivers/block/null_blk/main.c
>> @@ -1929,9 +1929,8 @@ static int null_validate_conf(struct nullb_device *dev)
>>  	if (dev->queue_mode == NULL_Q_BIO)
>>  		dev->mbps = 0;
>>  
>> -	if (dev->zoned &&
>> -	    (!dev->zone_size || !is_power_of_2(dev->zone_size))) {
>> -		pr_err("zone_size must be power-of-two\n");
>> +	if (dev->zoned && !dev->zone_size) {
>> +		pr_err("zone_size must not be zero\n");
> 
> May be a simpler phrasing would be better:
> 
> pr_err("Invalid zero zone size\n");
> 
Ack. I will change this in the next rev.
>>  		return -EINVAL;
>>  	}
>>  
>> diff --git a/drivers/block/null_blk/zoned.c b/drivers/block/null_blk/zoned.c
>> index dae54dd1a..00c34e65e 100644
>> --- a/drivers/block/null_blk/zoned.c
>> +++ b/drivers/block/null_blk/zoned.c
>> @@ -13,7 +13,10 @@ static inline sector_t mb_to_sects(unsigned long mb)
>>  
>>  static inline unsigned int null_zone_no(struct nullb_device *dev, sector_t sect)
>>  {
>> -	return sect >> ilog2(dev->zone_size_sects);
>> +	if (is_power_of_2(dev->zone_size_sects))
>> +		return sect >> ilog2(dev->zone_size_sects);
> 
> As a separate patch, I think we should really have ilog2(dev->zone_size_sects)
> as a dev field to avoid doing this ilog2 for every call..
> 
I don't think that is possible because `zone_size_sects` can also be non
po2.