libnvdimm/pfn_dev: Don't clear device memmap area during generic namespace probe

nvdimm core use nd_pfn_validate when looking for devdax or fsdax namespace. In this
case device resources are allocated against nd_namespace_io dev. In-order to
allow remap of range in nd_pfn_clear_memmap_error(), move the device memmap
area clearing while initializing pfn namespace. With this device
resource are allocated against nd_pfn and we can use nd_pfn->dev for remapping.

This also avoids calling nd_pfn_clear_mmap_errors twice. Once while probing the
namespace and second while initializing a pfn namespace.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Link: https://lore.kernel.org/r/20191101032728.113001-1-aneesh.kumar@linux.ibm.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/pfn_devs.c

@@ -591,7 +591,7 @@ int nd_pfn_validate(struct nd_pfn *nd_pfn, const char *sig)
 		return -ENXIO;
 	}
 
-	return nd_pfn_clear_memmap_errors(nd_pfn);
+	return 0;
 }
 EXPORT_SYMBOL(nd_pfn_validate);
 
@@ -729,6 +729,8 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 		sig = PFN_SIG;
 
 	rc = nd_pfn_validate(nd_pfn, sig);
+	if (rc == 0)
+		return nd_pfn_clear_memmap_errors(nd_pfn);
 	if (rc != -ENODEV)
 		return rc;
 
@@ -796,6 +798,10 @@ static int nd_pfn_init(struct nd_pfn *nd_pfn)
 	checksum = nd_sb_checksum((struct nd_gen_sb *) pfn_sb);
 	pfn_sb->checksum = cpu_to_le64(checksum);
 
+	rc = nd_pfn_clear_memmap_errors(nd_pfn);
+	if (rc)
+		return rc;
+
 	return nvdimm_write_bytes(ndns, SZ_4K, pfn_sb, sizeof(*pfn_sb), 0);
 }