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Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH v3 10/11] null_blk: allow non power of 2 zoned devices Content-Language: en-US To: Pankaj Raghav , jaegeuk@kernel.org, hare@suse.de, dsterba@suse.com, axboe@kernel.dk, hch@lst.de, snitzer@kernel.org Cc: Chris Mason , Josef Bacik , bvanassche@acm.org, linux-fsdevel@vger.kernel.org, matias.bjorling@wdc.com, Jens Axboe , gost.dev@samsung.com, jonathan.derrick@linux.dev, jiangbo.365@bytedance.com, linux-nvme@lists.infradead.org, dm-devel@redhat.com, Naohiro Aota , linux-kernel@vger.kernel.org, Johannes Thumshirn , Sagi Grimberg , Alasdair Kergon , linux-block@vger.kernel.org, Chaitanya Kulkarni , Keith Busch , linux-btrfs@vger.kernel.org, Luis Chamberlain References: <20220506081105.29134-1-p.raghav@samsung.com> <20220506081105.29134-11-p.raghav@samsung.com> <39a80347-af70-8af0-024a-52f92e27a14a@opensource.wdc.com> From: Damien Le Moal Organization: Western Digital Research In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2022/05/09 20:06, Pankaj Raghav wrote: > >>> 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. But when it is we can optimize that. All we need is add a "zone_size_sect_shift" field that is initialized when zone_size_sects is set when the device is created. Then, you can have code like: if (dev->zone_size_sect_shift)) return sect >> dev->zone_size_sect_shift; Which avoids both is_power_of_2() and ilog2() calls for every IO. -- Damien Le Moal Western Digital Research