libnvdimm/label: Add a helper for nlabel validation

In the CXL namespace label there is no need for nlabel since that is
inferred from the region. Add a helper that moves nsl_get_label() behind
a helper that validates the number of labels relative to the region.
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/163116430293.2460985.12693942353621355232.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/namespace_devs.c

@@ -1848,12 +1848,11 @@ static bool has_uuid_at_pos(struct nd_region *nd_region, const uuid_t *uuid,
 
 		list_for_each_entry(label_ent, &nd_mapping->labels, list) {
 			struct nd_namespace_label *nd_label = label_ent->label;
-			u16 position, nlabel;
+			u16 position;
 
 			if (!nd_label)
 				continue;
 			position = nsl_get_position(ndd, nd_label);
-			nlabel = nsl_get_nlabel(ndd, nd_label);
 
 			if (!nsl_validate_isetcookie(ndd, nd_label, cookie))
 				continue;
@@ -1870,7 +1869,7 @@ static bool has_uuid_at_pos(struct nd_region *nd_region, const uuid_t *uuid,
 				return false;
 			}
 			found_uuid = true;
-			if (nlabel != nd_region->ndr_mappings)
+			if (!nsl_validate_nlabel(nd_region, ndd, nd_label))
 				continue;
 			if (position != pos)
 				continue;

drivers/nvdimm/nd.h

@@ -342,6 +342,13 @@ struct nd_region {
 	struct nd_mapping mapping[];
 };
 
+static inline bool nsl_validate_nlabel(struct nd_region *nd_region,
+				       struct nvdimm_drvdata *ndd,
+				       struct nd_namespace_label *nd_label)
+{
+	return nsl_get_nlabel(ndd, nd_label) == nd_region->ndr_mappings;
+}
+
 struct nd_blk_region {
 	int (*enable)(struct nvdimm_bus *nvdimm_bus, struct device *dev);
 	int (*do_io)(struct nd_blk_region *ndbr, resource_size_t dpa,