mm: access zone->node via zone_to_nid() and zone_set_nid()

zone->node is configured only when CONFIG_NUMA=y, so it is a good idea to
have inline functions to access this field in order to avoid ifdef's in c
files.

Link: http://lkml.kernel.org/r/20180730101757.28058-3-osalvador@techadventures.net
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mempolicy.c

@@ -1784,7 +1784,7 @@ unsigned int mempolicy_slab_node(void)
 		zonelist = &NODE_DATA(node)->node_zonelists[ZONELIST_FALLBACK];
 		z = first_zones_zonelist(zonelist, highest_zoneidx,
 							&policy->v.nodes);
-		return z->zone ? z->zone->node : node;
+		return z->zone ? zone_to_nid(z->zone) : node;
 	}
 
 	default:
@@ -2326,7 +2326,7 @@ int mpol_misplaced(struct page *page, struct vm_area_struct *vma, unsigned long
 				node_zonelist(numa_node_id(), GFP_HIGHUSER),
 				gfp_zone(GFP_HIGHUSER),
 				&pol->v.nodes);
-		polnid = z->zone->node;
+		polnid = zone_to_nid(z->zone);
 		break;
 
 	default:

mm/mm_init.c

@@ -53,13 +53,8 @@ void __init mminit_verify_zonelist(void)
 				zone->name);
 
 			/* Iterate the zonelist */
-			for_each_zone_zonelist(zone, z, zonelist, zoneid) {
-#ifdef CONFIG_NUMA
-				pr_cont("%d:%s ", zone->node, zone->name);
-#else
-				pr_cont("0:%s ", zone->name);
-#endif /* CONFIG_NUMA */
-			}
+			for_each_zone_zonelist(zone, z, zonelist, zoneid)
+				pr_cont("%d:%s ", zone_to_nid(zone), zone->name);
 			pr_cont("\n");
 		}
 	}

mm/page_alloc.c

@@ -2909,10 +2909,10 @@ static inline void zone_statistics(struct zone *preferred_zone, struct zone *z)
 	if (!static_branch_likely(&vm_numa_stat_key))
 		return;
 
-	if (z->node != numa_node_id())
+	if (zone_to_nid(z) != numa_node_id())
 		local_stat = NUMA_OTHER;
 
-	if (z->node == preferred_zone->node)
+	if (zone_to_nid(z) == zone_to_nid(preferred_zone))
 		__inc_numa_state(z, NUMA_HIT);
 	else {
 		__inc_numa_state(z, NUMA_MISS);
@@ -5278,7 +5278,7 @@ int local_memory_node(int node)
 	z = first_zones_zonelist(node_zonelist(node, GFP_KERNEL),
 				   gfp_zone(GFP_KERNEL),
 				   NULL);
-	return z->zone->node;
+	return zone_to_nid(z->zone);
 }
 #endif
 
@@ -6299,9 +6299,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat)
 		 * And all highmem pages will be managed by the buddy system.
 		 */
 		zone->managed_pages = freesize;
-#ifdef CONFIG_NUMA
-		zone->node = nid;
-#endif
+		zone_set_nid(zone, nid);
 		zone->name = zone_names[j];
 		zone->zone_pgdat = pgdat;
 		spin_lock_init(&zone->lock);