mm, page_alloc: remove boot pageset initialization from memory hotplug

boot_pageset is a boot time hack which gets superseded by normal
pagesets later in the boot process.  It makes zero sense to reinitialize
it again and again during memory hotplug.

Link: http://lkml.kernel.org/r/20170721143915.14161-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6b23df1..94e6478 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5141,7 +5141,7 @@
 static int __build_all_zonelists(void *data)
 {
 	int nid;
-	int cpu;
+	int __maybe_unused cpu;
 	pg_data_t *self = data;
 
 #ifdef CONFIG_NUMA
@@ -5162,6 +5162,31 @@
 		}
 	}
 
+#ifdef CONFIG_HAVE_MEMORYLESS_NODES
+	for_each_possible_cpu(cpu) {
+		/*
+		 * We now know the "local memory node" for each node--
+		 * i.e., the node of the first zone in the generic zonelist.
+		 * Set up numa_mem percpu variable for on-line cpus.  During
+		 * boot, only the boot cpu should be on-line;  we'll init the
+		 * secondary cpus' numa_mem as they come on-line.  During
+		 * node/memory hotplug, we'll fixup all on-line cpus.
+		 */
+		if (cpu_online(cpu))
+			set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
+	}
+#endif
+
+	return 0;
+}
+
+static noinline void __init
+build_all_zonelists_init(void)
+{
+	int cpu;
+
+	__build_all_zonelists(NULL);
+
 	/*
 	 * Initialize the boot_pagesets that are going to be used
 	 * for bootstrapping processors. The real pagesets for
@@ -5175,30 +5200,9 @@
 	 * needs the percpu allocator in order to allocate its pagesets
 	 * (a chicken-egg dilemma).
 	 */
-	for_each_possible_cpu(cpu) {
+	for_each_possible_cpu(cpu)
 		setup_pageset(&per_cpu(boot_pageset, cpu), 0);
 
-#ifdef CONFIG_HAVE_MEMORYLESS_NODES
-		/*
-		 * We now know the "local memory node" for each node--
-		 * i.e., the node of the first zone in the generic zonelist.
-		 * Set up numa_mem percpu variable for on-line cpus.  During
-		 * boot, only the boot cpu should be on-line;  we'll init the
-		 * secondary cpus' numa_mem as they come on-line.  During
-		 * node/memory hotplug, we'll fixup all on-line cpus.
-		 */
-		if (cpu_online(cpu))
-			set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
-#endif
-	}
-
-	return 0;
-}
-
-static noinline void __init
-build_all_zonelists_init(void)
-{
-	__build_all_zonelists(NULL);
 	mminit_verify_zonelist();
 	cpuset_init_current_mems_allowed();
 }