Re: [PATCH 02/13] btrfs: zoned: don't count in-flight data as available in statfs

["Naohiro Aota" <Naohiro.Aota@wdc.com>]

On Wed Oct 14, 2026 at 9:03 PM JST, Johannes Thumshirn wrote:
> On a zoned filesystem GC makes freed space usable again only at zone
> granularity and after the in-flight writes landed.
>
> Don't promise space that is already reserved by delalloc or for extents
> being written to the user in statfs.
>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> ---
>  fs/btrfs/super.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 7fabb775d4e3..cbc1662abbff 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -1727,6 +1727,20 @@ static inline int btrfs_calc_avail_data_space(struct btrfs_fs_info *fs_info,
>  	return 0;
>  }
>  
> +static u64 btrfs_zoned_calc_inflight(struct btrfs_space_info *space_info)
> +{
> +	u64 profile = btrfs_data_alloc_profile(space_info->fs_info);
> +	u64 inflight;
> +
> +	spin_lock(&space_info->lock);
> +	inflight = space_info->bytes_may_use + space_info->bytes_reserved;
> +	spin_unlock(&space_info->lock);
> +
> +	inflight *= btrfs_bg_type_to_factor(profile);
> +
> +	return inflight;
> +}
> +

I'm not really sure of this. The bytes_may_use can take a lot bytes for
the worst case tree update scenario. And, that is not really an inflight
amount...


>  /*
>   * Calculate numbers for 'df', pessimistic in case of mixed raid profiles.
>   *
> @@ -1766,6 +1780,12 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>  			total_free_data -=
>  				btrfs_account_ro_block_groups_free_space(found);
>  
> +			if (btrfs_is_zoned(fs_info)) {
> +				u64 inflight = btrfs_zoned_calc_inflight(found);
> +
> +				total_free_data -= min(total_free_data, inflight);
> +			}
> +
>  			for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
>  				if (!list_empty(&found->block_groups[i]))
>  					factor = btrfs_bg_type_to_factor(