powerpc/mm: remove linear mapping if __add_pages() fails in arch_add_memory()

Let's revert what we did in case something goes wrong and we return an
error - as already done on arm64 and s390x.

Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201111145322.15793-8-david@redhat.com

arch/powerpc/mm/mem.c

@@ -170,7 +170,10 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
 	rc = arch_create_linear_mapping(nid, start, size, params);
 	if (rc)
 		return rc;
-	return __add_pages(nid, start_pfn, nr_pages, params);
+	rc = __add_pages(nid, start_pfn, nr_pages, params);
+	if (rc)
+		arch_remove_linear_mapping(start, size);
+	return rc;
 }
 
 void __ref arch_remove_memory(int nid, u64 start, u64 size,