[RFC PATCH 3/3] mm: Make free_area_init_node call certain functions only when booting

[osalvador@techadventures.net]

From: Oscar Salvador <osalvador@suse.de>

If free_area_init_node got called from memhotplug code, we do not need
to call calculate_node_totalpages(), as the node has no pages.

We do not need to set the range for the deferred initialization either,
as memmap_init_zone skips that when the context is MEMMAP_HOTPLUG.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/page_alloc.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3bf939393ca1..d2562751dbfd 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6299,8 +6299,6 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat)
 	spin_lock_init(&pgdat->lru_lock);
 	lruvec_init(node_lruvec(pgdat));
 
-	pgdat->per_cpu_nodestats = &boot_nodestats;
-
 	for (j = 0; j < MAX_NR_ZONES; j++) {
 		struct zone *zone = pgdat->node_zones + j;
 
@@ -6386,6 +6384,21 @@ static void __ref alloc_node_mem_map(struct pglist_data *pgdat)
 static void __ref alloc_node_mem_map(struct pglist_data *pgdat) { }
 #endif /* CONFIG_FLAT_NODE_MEM_MAP */
 
+#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
+static void pgdat_set_deferred_range(pg_data_t *pgdat)
+{
+	/*
+	 * We start only with one section of pages, more pages are added as
+	 * needed until the rest of deferred pages are initialized.
+	 */
+	pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
+						pgdat->node_spanned_pages);
+	pgdat->first_deferred_pfn = ULONG_MAX;
+}
+#else
+static void pgdat_set_deferred_range(pg_data_t *pgdat) {}
+#endif
+
 void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
 		unsigned long node_start_pfn, unsigned long *zholes_size)
 {
@@ -6407,20 +6420,14 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
 #else
 	start_pfn = node_start_pfn;
 #endif
-	calculate_node_totalpages(pgdat, start_pfn, end_pfn,
-				  zones_size, zholes_size);
-
-	alloc_node_mem_map(pgdat);
+	if (system_state == SYSTEM_BOOTING) {
+		calculate_node_totalpages(pgdat, start_pfn, end_pfn,
+					  zones_size, zholes_size);
+		alloc_node_mem_map(pgdat);
+		pgdat_set_deferred_range(pgdat);
+		pgdat->per_cpu_nodestats = &boot_nodestats;
+	}
 
-#ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
-	/*
-	 * We start only with one section of pages, more pages are added as
-	 * needed until the rest of deferred pages are initialized.
-	 */
-	pgdat->static_init_pgcnt = min_t(unsigned long, PAGES_PER_SECTION,
-					 pgdat->node_spanned_pages);
-	pgdat->first_deferred_pfn = ULONG_MAX;
-#endif
 	free_area_init_core(pgdat);
 }
 
-- 
2.13.6