Re: [PATCH v4 07/13] btrfs: zoned: use generic btrfs zone helpers to support npo2 zoned devices

David Sterba
2022-05-17T12:34:34Z

On Mon, May 16, 2022 at 06:54:10PM +0200, Pankaj Raghav wrote:
> Add helpers to calculate alignment, round up and round down
> for zoned devices. These helpers encapsulates the necessary handling for
> power_of_2 and non-power_of_2 zone sizes. Optimized calculations are
> performed for zone sizes that are power_of_2 with log and shifts.
>
> btrfs_zoned_is_aligned() is added instead of reusing bdev_zone_aligned()
> helper due to some use cases in btrfs where zone alignment is checked
> before having access to the underlying block device such as in this
> function: btrfs_load_block_group_zone_info().
>
> Use the generic btrfs zone helpers to calculate zone index, check zone
> alignment, round up and round down operations.
>
> The zone_size_shift field is not needed anymore as generic helpers are
> used for calculation.

Overall this looks reasonable to me.

> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
> Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
> ---
> fs/btrfs/volumes.c | 24 +++++++++-------
> fs/btrfs/zoned.c | 72 ++++++++++++++++++++++------------------------
> fs/btrfs/zoned.h | 43 +++++++++++++++++++++++----
> 3 files changed, 85 insertions(+), 54 deletions(-)
>
> --- a/fs/btrfs/zoned.c
> +++ b/fs/btrfs/zoned.c
> @@ -1108,14 +1101,14 @@ int btrfs_reset_device_zone(struct btrfs_device *device, u64 physical,
> int btrfs_ensure_empty_zones(struct btrfs_device *device, u64 start, u64 size)
> {
> struct btrfs_zoned_device_info *zinfo = device->zone_info;
> - const u8 shift = zinfo->zone_size_shift;
> - unsigned long begin = start >> shift;
> - unsigned long end = (start + size) >> shift;
> + unsigned long begin = bdev_zone_no(device->bdev, start >> SECTOR_SHIFT);
> + unsigned long end =
> + bdev_zone_no(device->bdev, (start + size) >> SECTOR_SHIFT);

There are unsinged long types here though I'd rather see u64, better for
a separate patch. Fixed width types are cleaner here and in the zoned
code as there's always some conversion to/from sectors.

> u64 pos;
> int ret;
>
> - ASSERT(IS_ALIGNED(start, zinfo->zone_size));
> - ASSERT(IS_ALIGNED(size, zinfo->zone_size));
> + ASSERT(btrfs_zoned_is_aligned(start, zinfo->zone_size));
> + ASSERT(btrfs_zoned_is_aligned(size, zinfo->zone_size));
>
> if (end > zinfo->nr_zones)
> return -ERANGE;
> --- a/fs/btrfs/zoned.h
> +++ b/fs/btrfs/zoned.h
> @@ -30,6 +30,36 @@ struct btrfs_zoned_device_info {
> u32 sb_zone_location[BTRFS_SUPER_MIRROR_MAX];
> };
>
> +static inline bool btrfs_zoned_is_aligned(u64 pos, u64 zone_size)
> +{
> + u64 remainder = 0;
> +
> + if (is_power_of_two_u64(zone_size))
> + return IS_ALIGNED(pos, zone_size);
> +
> + div64_u64_rem(pos, zone_size, &remainder);
> + return remainder == 0;
> +}
> +
> +static inline u64 btrfs_zoned_roundup(u64 pos, u64 zone_size)
> +{
> + if (is_power_of_two_u64(zone_size))
> + return ALIGN(pos, zone_size);

Please use round_up as the rounddown helper uses round_down

> +
> + return div64_u64(pos + zone_size - 1, zone_size) * zone_size;
> +}
> +
> +static inline u64 btrfs_zoned_rounddown(u64 pos, u64 zone_size)
> +{
> + u64 remainder = 0;
> + if (is_power_of_two_u64(zone_size))
> + return round_down(pos, zone_size);
> +
> + div64_u64_rem(pos, zone_size, &remainder);
> + pos -= remainder;
> + return pos;
> +}
> +
> #ifdef CONFIG_BLK_DEV_ZONED
> int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
> struct blk_zone *zone);