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Message-ID: <09bb7615-cf72-7f1e-9158-2ce231c0dda8@linux.dev>
Date: Fri, 26 Aug 2022 14:09:22 -0600
From: Jonathan Derrick <jonathan.derrick@...ux.dev>
To: Pankaj Raghav <p.raghav@...sung.com>, agk@...hat.com,
snitzer@...nel.org, axboe@...nel.dk,
damien.lemoal@...nsource.wdc.com, hch@....de
Cc: pankydev8@...il.com, Johannes.Thumshirn@....com,
linux-block@...r.kernel.org, dm-devel@...hat.com, hare@...e.de,
jaegeuk@...nel.org, linux-kernel@...r.kernel.org,
matias.bjorling@....com, gost.dev@...sung.com, bvanassche@....org,
linux-nvme@...ts.infradead.org,
Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: [PATCH v12 03/13] block: allow blk-zoned devices to have
non-power-of-2 zone size
On 8/26/2022 2:06 PM, Jonathan Derrick wrote:
>
>
> On 8/23/2022 6:18 AM, 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
>> everywhere.
>>
>> Convert the calculations on zone size to be generic instead of relying on
>> power-of-2(po2) based arithmetic in the block layer using the helpers
>> wherever possible.
>>
>> The only hot path affected by this change for zoned devices with po2
>> zone size is in blk_check_zone_append() but bdev_is_zone_start()
>> helper is
>> used to optimize the calculation for po2 zone sizes.
>>
>> Finally, allow zoned devices with non po2 zone sizes provided that their
>> zone capacity and zone size are equal. The main motivation to allow zoned
>> devices with non po2 zone size is to remove the unmapped LBA between
>> zone capcity and zone size for devices that cannot have a po2 zone
>> capacity.
>>
>> Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
>> Reviewed-by: Hannes Reinecke <hare@...e.de>
>> Reviewed-by: Bart Van Assche <bvanassche@....org>
>> Signed-off-by: Pankaj Raghav <p.raghav@...sung.com>
>> ---
>> block/blk-core.c | 2 +-
>> block/blk-zoned.c | 24 ++++++++++++++++++------
>> include/linux/blkdev.h | 30 ++++++++++++++++++++++++++++++
>> 3 files changed, 49 insertions(+), 7 deletions(-)
>>
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index a0d1104c5590..1cb519220ffb 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -563,7 +563,7 @@ 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_start(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..6806c69c81dc 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_start(bdev, sector))
>> return -EINVAL;
>> - if ((nr_sectors & (zone_sectors - 1)) && end_sector != capacity)
>> + if (!bdev_is_zone_start(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 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_err("%s: Invalid zone capacity %lld with non
>> power-of-2 zone size %lld",
>> + disk->disk_name, zone->capacity, zone->len);
>> 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);
>> } 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 84e7881262e3..d0d66a0db224 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -704,6 +704,30 @@ 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;
> See below
>
>> +
>> + 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_start(struct block_device *bdev,
>> sector_t sec)
>> +{
>> + if (!bdev_is_zoned(bdev))
>> + return false;
> Duplicating the same check above, and the check above is less clear in
> the case of !zoned since it returns 0 and not some warning that makes
> sense in the case of zoned check on !zoned bdev.
> Can you simply exclude above check?
Nevermind, just noticed bdev_offset_from_zone_start is used in later
patches.
>
>
>> +
>> + 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))
>> @@ -748,6 +772,12 @@ static inline unsigned int disk_zone_no(struct
>> gendisk *disk, sector_t sector)
>> {
>> return 0;
>> }
>> +
>> +static inline bool bdev_is_zone_start(struct block_device *bdev,
>> sector_t sec)
>> +{
>> + return false;
>> +}
>> +
>> static inline unsigned int bdev_max_open_zones(struct block_device
>> *bdev)
>> {
>> return 0;
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