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Message-ID: <d2fd2554-19c3-6ca3-6175-b8e8563986a5@opensource.wdc.com>
Date: Mon, 16 May 2022 16:00:36 +0200
From: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To: Pankaj Raghav <p.raghav@...sung.com>, axboe@...nel.dk,
naohiro.aota@....com, Johannes.Thumshirn@....com,
snitzer@...nel.org, dsterba@...e.com, jaegeuk@...nel.org,
hch@....de
Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
jonathan.derrick@...ux.dev, bvanassche@....org,
Keith Busch <kbusch@...nel.org>, gost.dev@...sung.com,
linux-nvme@...ts.infradead.org,
Johannes Thumshirn <jth@...nel.org>,
Josef Bacik <josef@...icpanda.com>,
linux-block@...r.kernel.org, Alasdair Kergon <agk@...hat.com>,
matias.bjorling@....com, Jens Axboe <axboe@...com>,
Sagi Grimberg <sagi@...mberg.me>, dm-devel@...hat.com,
jiangbo.365@...edance.com, Chaitanya Kulkarni <kch@...dia.com>,
linux-fsdevel@...r.kernel.org, Chris Mason <clm@...com>,
Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: [PATCH v4 02/13] block: allow blk-zoned devices to have
non-power-of-2 zone size
On 2022/05/16 15:39, Pankaj Raghav wrote:
> Checking if a given sector is aligned to a zone is a common
> operation that is performed for zoned devices. Add
> blk_queue_is_zone_start helper to check for this instead of opencoding it
> everywhere.
>
> Convert the calculations on zone size to be generic instead of relying on
> power_of_2 based logic in the block layer using the helpers wherever
> possible.
>
> The only hot path affected by this change for power_of_2 zoned devices
> is in blk_check_zone_append() but blk_queue_is_zone_start() helper is
> used to optimize the calculation for po2 zone sizes. Note that the append
> path cannot be accessed by direct raw access to the block device but only
> through a filesystem abstraction.
>
> Finally, allow non power of 2 zoned devices provided that their zone
> capacity and zone size are equal. The main motivation to allow non
> power_of_2 zoned device is to remove the unmapped LBA between zcap and
> zsze for devices that cannot have a power_of_2 zcap.
>
> Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> ---
> block/blk-core.c | 3 +--
> block/blk-zoned.c | 27 +++++++++++++++++++++------
> include/linux/blkdev.h | 22 ++++++++++++++++++++++
> 3 files changed, 44 insertions(+), 8 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index f305cb66c..b7051b7ea 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -634,8 +634,7 @@ static inline blk_status_t blk_check_zone_append(struct request_queue *q,
> return BLK_STS_NOTSUPP;
>
> /* The bio sector must point to the start of a sequential zone */
> - if (pos & (blk_queue_zone_sectors(q) - 1) ||
> - !blk_queue_zone_is_seq(q, pos))
> + if (!blk_queue_is_zone_start(q, pos) || !blk_queue_zone_is_seq(q, pos))
> return BLK_STS_IOERR;
>
> /*
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index 140230134..cfc2fb804 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -289,10 +289,10 @@ int blkdev_zone_mgmt(struct block_device *bdev, enum req_opf op,
> return -EINVAL;
>
> /* Check alignment (handle eventual smaller last zone) */
> - if (sector & (zone_sectors - 1))
> + if (!blk_queue_is_zone_start(q, sector))
> return -EINVAL;
>
> - if ((nr_sectors & (zone_sectors - 1)) && end_sector != capacity)
> + if (!blk_queue_is_zone_start(q, nr_sectors) && end_sector != capacity)
> return -EINVAL;
>
> /*
> @@ -490,14 +490,29 @@ static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
> * smaller last zone.
> */
> if (zone->start == 0) {
> - if (zone->len == 0 || !is_power_of_2(zone->len)) {
> - pr_warn("%s: Invalid zoned device with non power of two zone size (%llu)\n",
> - disk->disk_name, zone->len);
> + if (zone->len == 0) {
> + pr_warn("%s: Invalid zone size",
> + disk->disk_name);
This fits on one line, no ?
> + return -ENODEV;
> + }
> +
> + /*
> + * Don't allow zoned device with non power_of_2 zone size with
> + * zone capacity less than zone size.
> + */
> + if (!is_power_of_2(zone->len) &&
> + zone->capacity < zone->len) {
> + pr_warn("%s: Invalid zoned size with non power of 2 zone size and zone capacity < zone size",
> + disk->disk_name);
Very long... What about:
pr_warn("%s: Invalid zone capacity for non power of 2 zone size",
disk->disk_name);
> return -ENODEV;
> }
>
> args->zone_sectors = zone->len;
> - args->nr_zones = (capacity + zone->len - 1) >> ilog2(zone->len);
> + /*
> + * Division is used to calculate nr_zones for both power_of_2
> + * and non power_of_2 zone sizes as it is not in the hot path.
> + */
This comment is not very useful.
> + args->nr_zones = div64_u64(capacity + zone->len - 1, zone->len);
> } else if (zone->start + args->zone_sectors < capacity) {
> if (zone->len != args->zone_sectors) {
> pr_warn("%s: Invalid zoned device with non constant zone size\n",
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 22fe512ee..32d7bd7b1 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -686,6 +686,22 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
> return div64_u64(sector, zone_sectors);
> }
>
> +static inline bool blk_queue_is_zone_start(struct request_queue *q, sector_t sec)
> +{
> + sector_t zone_sectors = blk_queue_zone_sectors(q);
> + u64 remainder = 0;
> +
> + if (!blk_queue_is_zoned(q))
> + return false;
> +
> + if (is_power_of_2(zone_sectors))
> + return IS_ALIGNED(sec, zone_sectors);
> +
> + div64_u64_rem(sec, zone_sectors, &remainder);
> + /* if there is a remainder, then the sector is not aligned */
Hmmm... Fairly obvious. Not sure this comment is useful.
> + return remainder == 0;
> +}
> +
> static inline bool blk_queue_zone_is_seq(struct request_queue *q,
> sector_t sector)
> {
> @@ -732,6 +748,12 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
> {
> return 0;
> }
> +
> +static inline bool blk_queue_is_zone_start(struct request_queue *q, sector_t sec)
> +{
> + return false;
> +}
> +
> static inline unsigned int queue_max_open_zones(const struct request_queue *q)
> {
> return 0;
--
Damien Le Moal
Western Digital Research
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