Re: [PATCH 04/23] libnvdimm/labels: Add a checksum calculation helper

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Mon, 9 Aug 2021 15:28:08 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> In preparation for LIBNVDIMM to manage labels on CXL devices deploy
> helpers that abstract the label type from the implementation. The CXL
> label format is mostly similar to the EFI label format with concepts /
> fields added, like dynamic region creation and label type guids, and
> other concepts removed like BLK-mode and interleave-set-cookie ids.
> 
> CXL labels support checksums by default, but early versions of the EFI
> labels did not. Add a validate function that can return true in the case
> the label format does not implement a checksum.
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/nvdimm/label.c |   68 +++++++++++++++++++++++++-----------------------
>  1 file changed, 35 insertions(+), 33 deletions(-)
> 
> diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
> index b40a4eda1d89..3f73412dd438 100644
> --- a/drivers/nvdimm/label.c
> +++ b/drivers/nvdimm/label.c
> @@ -346,29 +346,45 @@ static bool preamble_next(struct nvdimm_drvdata *ndd,
>  			free, nslot);
>  }
>  
> +static bool nsl_validate_checksum(struct nvdimm_drvdata *ndd,
> +				  struct nd_namespace_label *nd_label)
> +{
> +	u64 sum, sum_save;
> +
> +	if (!namespace_label_has(ndd, checksum))
> +		return true;
> +
> +	sum_save = nsl_get_checksum(ndd, nd_label);
> +	nsl_set_checksum(ndd, nd_label, 0);
> +	sum = nd_fletcher64(nd_label, sizeof_namespace_label(ndd), 1);
> +	nsl_set_checksum(ndd, nd_label, sum_save);
> +	return sum == sum_save;
> +}
> +
> +static void nsl_calculate_checksum(struct nvdimm_drvdata *ndd,
> +				   struct nd_namespace_label *nd_label)
> +{
> +	u64 sum;
> +
> +	if (!namespace_label_has(ndd, checksum))
> +		return;
> +	nsl_set_checksum(ndd, nd_label, 0);
> +	sum = nd_fletcher64(nd_label, sizeof_namespace_label(ndd), 1);
> +	nsl_set_checksum(ndd, nd_label, sum);
> +}
> +
>  static bool slot_valid(struct nvdimm_drvdata *ndd,
>  		struct nd_namespace_label *nd_label, u32 slot)
>  {
> +	bool valid;
> +
>  	/* check that we are written where we expect to be written */
>  	if (slot != nsl_get_slot(ndd, nd_label))
>  		return false;
> -
> -	/* check checksum */
> -	if (namespace_label_has(ndd, checksum)) {
> -		u64 sum, sum_save;
> -
> -		sum_save = nsl_get_checksum(ndd, nd_label);
> -		nsl_set_checksum(ndd, nd_label, 0);
> -		sum = nd_fletcher64(nd_label, sizeof_namespace_label(ndd), 1);
> -		nsl_set_checksum(ndd, nd_label, sum_save);
> -		if (sum != sum_save) {
> -			dev_dbg(ndd->dev, "fail checksum. slot: %d expect: %#llx\n",
> -				slot, sum);
> -			return false;
> -		}
> -	}
> -
> -	return true;
> +	valid = nsl_validate_checksum(ndd, nd_label);
> +	if (!valid)
> +		dev_dbg(ndd->dev, "fail checksum. slot: %d\n", slot);
> +	return valid;
>  }
>  
>  int nd_label_reserve_dpa(struct nvdimm_drvdata *ndd)
> @@ -812,13 +828,7 @@ static int __pmem_label_update(struct nd_region *nd_region,
>  		guid_copy(&nd_label->abstraction_guid,
>  				to_abstraction_guid(ndns->claim_class,
>  					&nd_label->abstraction_guid));
> -	if (namespace_label_has(ndd, checksum)) {
> -		u64 sum;
> -
> -		nsl_set_checksum(ndd, nd_label, 0);
> -		sum = nd_fletcher64(nd_label, sizeof_namespace_label(ndd), 1);
> -		nsl_set_checksum(ndd, nd_label, sum);
> -	}
> +	nsl_calculate_checksum(ndd, nd_label);
>  	nd_dbg_dpa(nd_region, ndd, res, "\n");
>  
>  	/* update label */
> @@ -1049,15 +1059,7 @@ static int __blk_label_update(struct nd_region *nd_region,
>  			guid_copy(&nd_label->abstraction_guid,
>  					to_abstraction_guid(ndns->claim_class,
>  						&nd_label->abstraction_guid));
> -
> -		if (namespace_label_has(ndd, checksum)) {
> -			u64 sum;
> -
> -			nsl_set_checksum(ndd, nd_label, 0);
> -			sum = nd_fletcher64(nd_label,
> -					sizeof_namespace_label(ndd), 1);
> -			nsl_set_checksum(ndd, nd_label, sum);
> -		}
> +		nsl_calculate_checksum(ndd, nd_label);
>  
>  		/* update label */
>  		offset = nd_label_offset(ndd, nd_label);
>