mm/page_alloc.c: move ifdefery out of free_area_init_core

Patch series "Refactor free_area_init_core and add
free_area_init_core_hotplug", v6.

This patchset does three things:

 1) Clean up/refactor free_area_init_core/free_area_init_node
    by moving the ifdefery out of the functions.
 2) Move the pgdat/zone initialization in free_area_init_core to its
    own function.
 3) Introduce free_area_init_core_hotplug, a small subset of
    free_area_init_core, which is only called from memhotlug code path. In this
    way, we have:

    free_area_init_core: called during early initialization
    free_area_init_core_hotplug: called whenever a new node is allocated/re-used (memhotplug path)

This patch (of 5):

Moving the #ifdefs out of the function makes it easier to follow.

Link: http://lkml.kernel.org/r/20180730101757.28058-2-osalvador@techadventures.netSigned-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

@@ -6194,6 +6194,37 @@ static unsigned long __paginginit calc_memmap_size(unsigned long spanned_pages,
 	return PAGE_ALIGN(pages * sizeof(struct page)) >> PAGE_SHIFT;
 }
 
+#ifdef CONFIG_NUMA_BALANCING
+static void pgdat_init_numabalancing(struct pglist_data *pgdat)
+{
+	spin_lock_init(&pgdat->numabalancing_migrate_lock);
+	pgdat->numabalancing_migrate_nr_pages = 0;
+	pgdat->numabalancing_migrate_next_window = jiffies;
+}
+#else
+static void pgdat_init_numabalancing(struct pglist_data *pgdat) {}
+#endif
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void pgdat_init_split_queue(struct pglist_data *pgdat)
+{
+	spin_lock_init(&pgdat->split_queue_lock);
+	INIT_LIST_HEAD(&pgdat->split_queue);
+	pgdat->split_queue_len = 0;
+}
+#else
+static void pgdat_init_split_queue(struct pglist_data *pgdat) {}
+#endif
+
+#ifdef CONFIG_COMPACTION
+static void pgdat_init_kcompactd(struct pglist_data *pgdat)
+{
+	init_waitqueue_head(&pgdat->kcompactd_wait);
+}
+#else
+static void pgdat_init_kcompactd(struct pglist_data *pgdat) {}
+#endif
+
 /*
  * Set up the zone data structures:
  *   - mark all pages reserved
@@ -6208,21 +6239,14 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat)
 	int nid = pgdat->node_id;
 
 	pgdat_resize_init(pgdat);
-#ifdef CONFIG_NUMA_BALANCING
-	spin_lock_init(&pgdat->numabalancing_migrate_lock);
-	pgdat->numabalancing_migrate_nr_pages = 0;
-	pgdat->numabalancing_migrate_next_window = jiffies;
-#endif
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	spin_lock_init(&pgdat->split_queue_lock);
-	INIT_LIST_HEAD(&pgdat->split_queue);
-	pgdat->split_queue_len = 0;
-#endif
+
+	pgdat_init_numabalancing(pgdat);
+	pgdat_init_split_queue(pgdat);
+	pgdat_init_kcompactd(pgdat);
+
 	init_waitqueue_head(&pgdat->kswapd_wait);
 	init_waitqueue_head(&pgdat->pfmemalloc_wait);
-#ifdef CONFIG_COMPACTION
-	init_waitqueue_head(&pgdat->kcompactd_wait);
-#endif
+
 	pgdat_page_ext_init(pgdat);
 	spin_lock_init(&pgdat->lru_lock);
 	lruvec_init(node_lruvec(pgdat));