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

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Date:   Tue, 17 May 2022 14:30:08 +0200
From:   David Sterba <dsterba@...e.cz>
To:     Pankaj Raghav <p.raghav@...sung.com>
Cc:     axboe@...nel.dk, damien.lemoal@...nsource.wdc.com,
        pankydev8@...il.com, dsterba@...e.com, hch@....de,
        linux-nvme@...ts.infradead.org, linux-fsdevel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, jiangbo.365@...edance.com,
        linux-block@...r.kernel.org, gost.dev@...sung.com,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: Re: [PATCH v4 07/13] btrfs: zoned: use generic btrfs zone helpers to
 support npo2 zoned devices

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@...nel.org>
> Signed-off-by: Pankaj Raghav <p.raghav@...sung.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);