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Message-ID: <e9663c20-65d5-48f5-3fe1-e3a8f5ab3214@opensource.wdc.com>
Date: Thu, 28 Jul 2022 12:07:15 +0900
From: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To: Pankaj Raghav <p.raghav@...sung.com>, hch@....de, axboe@...nel.dk,
snitzer@...nel.org, Johannes.Thumshirn@....com
Cc: matias.bjorling@....com, gost.dev@...sung.com,
linux-kernel@...r.kernel.org, hare@...e.de,
linux-block@...r.kernel.org, pankydev8@...il.com,
bvanassche@....org, jaegeuk@...nel.org, dm-devel@...hat.com,
linux-nvme@...ts.infradead.org,
Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: [PATCH v8 02/11] block: allow blk-zoned devices to have
non-power-of-2 zone size
On 7/28/22 01:22, Pankaj Raghav wrote:
> Checking if a given sector is aligned to a zone is a common
> operation that is performed for zoned devices. Add
> bdev_is_zone_start helper to check for this instead of opencoding it
The patch actually introduces bdev_is_zone_aligned(). I agree with Bart
that bdev_is_zone_start() is a better name.
> 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
s/based logic/arithmetics
> possible.
>
> The only hot path affected by this change for power_of_2 zoned devices
> is in blk_check_zone_append() but bdev_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.
And so what ? What is the point here ?
>
> Finally, allow non power of 2 zoned devices provided that their zone
Please spell things out clearly: ...allow zoned devices with a zone size
that is not a power of 2 number of sectors...
> 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.
zcap, zsze are nvme field names. Please phrase these in plain english to
clarify.
>
> To make this work bdev_get_queue(), bdev_zone_sectors() and
> bdev_is_zoned() are moved earlier without modifications.
"moved earlier" -> declared earlier in xxx.h ?
>
> Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
> Reviewed-by: Hannes Reinecke <hare@...e.de>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
> ---
> block/blk-core.c | 2 +-
> block/blk-zoned.c | 24 +++++++++---
> include/linux/blkdev.h | 84 ++++++++++++++++++++++++++++++------------
> 3 files changed, 79 insertions(+), 31 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 3d286a256d3d..1f7e9a90e198 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -570,7 +570,7 @@ 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 (bio->bi_iter.bi_sector & (bdev_zone_sectors(bio->bi_bdev) - 1) ||
> + if (!bdev_is_zone_aligned(bio->bi_bdev, bio->bi_iter.bi_sector) ||
> !bio_zone_is_seq(bio))
> return BLK_STS_IOERR;
>
> diff --git a/block/blk-zoned.c b/block/blk-zoned.c
> index dce9c95b4bcd..a01a231ad328 100644
> --- a/block/blk-zoned.c
> +++ b/block/blk-zoned.c
> @@ -285,10 +285,10 @@ int blkdev_zone_mgmt(struct block_device *bdev, enum req_op op,
> return -EINVAL;
>
> /* Check alignment (handle eventual smaller last zone) */
> - if (sector & (zone_sectors - 1))
> + if (!bdev_is_zone_aligned(bdev, sector))
> return -EINVAL;
>
> - if ((nr_sectors & (zone_sectors - 1)) && end_sector != capacity)
> + if (!bdev_is_zone_aligned(bdev, nr_sectors) && end_sector != capacity)
> return -EINVAL;
>
> /*
> @@ -486,14 +486,26 @@ 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);
You removed the zone size value print, so please update the message to
something like:
pr_warn("%s: Invalid zero zone size", disk->disk_name);
> + return -ENODEV;
> + }
> +
> + /*
> + * Non power-of-2 zone size support was added to remove the
> + * gap between zone capacity and zone size. Though it is technically
> + * possible to have gaps in a non power-of-2 device, Linux requires
> + * the zone size to be equal to zone capacity for non power-of-2
> + * zoned devices.
> + */
> + if (!is_power_of_2(zone->len) && zone->capacity < zone->len) {
> + pr_warn("%s: Invalid zone capacity for non power of 2 zone size",
> + disk->disk_name);
As Bart suggested, please print the zone capacity and zone size values.
> return -ENODEV;
> }
>
> args->zone_sectors = zone->len;
> - args->nr_zones = (capacity + zone->len - 1) >> ilog2(zone->len);
> + args->nr_zones = div64_u64(capacity + zone->len - 1, zone->len);
args->nr_zones = disk_zone_no(disk, capacity);
> } 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 85b832908f28..1be805223026 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -634,6 +634,11 @@ static inline bool queue_is_mq(struct request_queue *q)
> return q->mq_ops;
> }
>
> +static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
> +{
> + return bdev->bd_queue; /* this is never NULL */
> +}
> +
> #ifdef CONFIG_PM
> static inline enum rpm_status queue_rpm_status(struct request_queue *q)
> {
> @@ -665,6 +670,25 @@ static inline bool blk_queue_is_zoned(struct request_queue *q)
> }
> }
>
> +static inline bool bdev_is_zoned(struct block_device *bdev)
> +{
> + struct request_queue *q = bdev_get_queue(bdev);
> +
> + if (q)
> + return blk_queue_is_zoned(q);
> +
> + return false;
> +}
> +
> +static inline sector_t bdev_zone_sectors(struct block_device *bdev)
> +{
> + struct request_queue *q = bdev_get_queue(bdev);
> +
> + if (!blk_queue_is_zoned(q))
> + return 0;
> + return q->limits.chunk_sectors;
> +}
> +
> #ifdef CONFIG_BLK_DEV_ZONED
> static inline unsigned int disk_nr_zones(struct gendisk *disk)
> {
> @@ -684,6 +708,30 @@ static inline unsigned int disk_zone_no(struct gendisk *disk, sector_t sector)
> return div64_u64(sector, zone_sectors);
> }
>
> +static inline sector_t bdev_offset_from_zone_start(struct block_device *bdev,
> + sector_t sec)
> +{
> + sector_t zone_sectors = bdev_zone_sectors(bdev);
> + u64 remainder = 0;
> +
> + if (!bdev_is_zoned(bdev))
> + return 0;
> +
> + if (is_power_of_2(zone_sectors))
> + return sec & (zone_sectors - 1);
> +
> + div64_u64_rem(sec, zone_sectors, &remainder);
> + return remainder;
> +}
> +
> +static inline bool bdev_is_zone_aligned(struct block_device *bdev, sector_t sec)
> +{
> + if (!bdev_is_zoned(bdev))
> + return false;
This is checked in bdev_offset_from_zone_start(). No need to add it again
here.
> +
> + return bdev_offset_from_zone_start(bdev, sec) == 0;
> +}
> +
> static inline bool disk_zone_is_seq(struct gendisk *disk, sector_t sector)
> {
> if (!blk_queue_is_zoned(disk->queue))
> @@ -728,6 +776,18 @@ static inline unsigned int disk_zone_no(struct gendisk *disk, sector_t sector)
> {
> return 0;
> }
> +
> +static inline sector_t bdev_offset_from_zone_start(struct block_device *bdev,
> + sector_t sec)
> +{
> + return 0;
> +}
This one is not used when CONFIG_BLK_DEV_ZONED is not set. No need to
define it.
> +
> +static inline bool bdev_is_zone_aligned(struct block_device *bdev, sector_t sec)
> +{
> + return false;
> +}
> +
> static inline unsigned int bdev_max_open_zones(struct block_device *bdev)
> {
> return 0;
> @@ -891,11 +951,6 @@ int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags);
> int iocb_bio_iopoll(struct kiocb *kiocb, struct io_comp_batch *iob,
> unsigned int flags);
>
> -static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
> -{
> - return bdev->bd_queue; /* this is never NULL */
> -}
> -
> /* Helper to convert BLK_ZONE_ZONE_XXX to its string format XXX */
> const char *blk_zone_cond_str(enum blk_zone_cond zone_cond);
>
> @@ -1295,25 +1350,6 @@ static inline enum blk_zoned_model bdev_zoned_model(struct block_device *bdev)
> return BLK_ZONED_NONE;
> }
>
> -static inline bool bdev_is_zoned(struct block_device *bdev)
> -{
> - struct request_queue *q = bdev_get_queue(bdev);
> -
> - if (q)
> - return blk_queue_is_zoned(q);
> -
> - return false;
> -}
> -
> -static inline sector_t bdev_zone_sectors(struct block_device *bdev)
> -{
> - struct request_queue *q = bdev_get_queue(bdev);
> -
> - if (!blk_queue_is_zoned(q))
> - return 0;
> - return q->limits.chunk_sectors;
> -}
> -
> static inline int queue_dma_alignment(const struct request_queue *q)
> {
> return q ? q->dma_alignment : 511;
--
Damien Le Moal
Western Digital Research
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