Re: [PATCH] btrfs: Don't hardcode the csum size in btrfs_ordered_sum_size

[Su Yue <suy.fnst@cn.fujitsu.com>]

On 02/07/2018 05:19 PM, Nikolay Borisov wrote:
> Currently the function uses a hardcoded value for the checksum size of
> a sector. This is fine, given that we currently support only a single
> algorithm, whose checksum is 4 bytes == sizeof(u32). Despite not
> having other algorithms, btrfs' design supports using a different
> algorithm whith different space requirements. To future-proof the code
> query the size of the currently used algorithm from the in-memory copy
> of the super block. No functional changes.
> 
> Signed-off-by: Nikolay Borisov <nborisov@suse.com>

Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>
> ---
>   fs/btrfs/ordered-data.h | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
> index 56c4c0ee6381..c53e2cfb72d9 100644
> --- a/fs/btrfs/ordered-data.h
> +++ b/fs/btrfs/ordered-data.h
> @@ -151,7 +151,9 @@ static inline int btrfs_ordered_sum_size(struct btrfs_fs_info *fs_info,
>   					 unsigned long bytes)
>   {
>   	int num_sectors = (int)DIV_ROUND_UP(bytes, fs_info->sectorsize);
> -	return sizeof(struct btrfs_ordered_sum) + num_sectors * sizeof(u32);
> +	int csum_size = btrfs_super_csum_size(fs_info->super_copy);
> +
> +	return sizeof(struct btrfs_ordered_sum) + num_sectors * csum_size;
>   }
>   
>   static inline void
>