mm, memory_hotplug: drop zone from build_all_zonelists

build_all_zonelists gets a zone parameter to initialize zone's pagesets.
There is only a single user which gives a non-NULL zone parameter and
that one doesn't really need the rest of the build_all_zonelists (see
commit 6dcd73d7 ("memory-hotplug: allocate zone's pcp before
onlining pages")).

Therefore remove setup_zone_pageset from build_all_zonelists and call it
from its only user directly.  This will also remove a pointless zonlists
rebuilding which is always good.

Link: http://lkml.kernel.org/r/20170721143915.14161-5-mhocko@kernel.orgSigned-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mmzone.h

@@ -771,7 +771,7 @@ static inline bool is_dev_zone(const struct zone *zone)
 #include <linux/memory_hotplug.h>
 
 extern struct mutex zonelists_mutex;
-void build_all_zonelists(pg_data_t *pgdat, struct zone *zone);
+void build_all_zonelists(pg_data_t *pgdat);
 void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx);
 bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark,
 			 int classzone_idx, unsigned int alloc_flags,

init/main.c

@@ -542,7 +542,7 @@ asmlinkage __visible void __init start_kernel(void)
 	boot_cpu_state_init();
 	smp_prepare_boot_cpu();	/* arch-specific boot-cpu hooks */
 
-	build_all_zonelists(NULL, NULL);
+	build_all_zonelists(NULL);
 	page_alloc_init();
 
 	pr_notice("Kernel command line: %s\n", boot_command_line);

mm/internal.h

@@ -525,4 +525,5 @@ static inline bool is_migrate_highatomic_page(struct page *page)
 	return get_pageblock_migratetype(page) == MIGRATE_HIGHATOMIC;
 }
 
+void setup_zone_pageset(struct zone *zone);
 #endif	/* __MM_INTERNAL_H */

mm/memory_hotplug.c

@@ -929,7 +929,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	mutex_lock(&zonelists_mutex);
 	if (!populated_zone(zone)) {
 		need_zonelists_rebuild = 1;
-		build_all_zonelists(NULL, zone);
+		setup_zone_pageset(zone);
 	}
 
 	ret = walk_system_ram_range(pfn, nr_pages, &onlined_pages,
@@ -950,7 +950,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, int online_typ
 	if (onlined_pages) {
 		node_states_set_node(nid, &arg);
 		if (need_zonelists_rebuild)
-			build_all_zonelists(NULL, NULL);
+			build_all_zonelists(NULL);
 		else
 			zone_pcp_update(zone);
 	}
@@ -1028,7 +1028,7 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start)
 	 * to access not-initialized zonelist, build here.
 	 */
 	mutex_lock(&zonelists_mutex);
-	build_all_zonelists(pgdat, NULL);
+	build_all_zonelists(pgdat);
 	mutex_unlock(&zonelists_mutex);
 
 	/*
@@ -1084,7 +1084,7 @@ int try_online_node(int nid)
 
 	if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
 		mutex_lock(&zonelists_mutex);
-		build_all_zonelists(NULL, NULL);
+		build_all_zonelists(NULL);
 		mutex_unlock(&zonelists_mutex);
 	}
 
@@ -1704,7 +1704,7 @@ static int __ref __offline_pages(unsigned long start_pfn,
 	if (!populated_zone(zone)) {
 		zone_pcp_reset(zone);
 		mutex_lock(&zonelists_mutex);
-		build_all_zonelists(NULL, NULL);
+		build_all_zonelists(NULL);
 		mutex_unlock(&zonelists_mutex);
 	} else
 		zone_pcp_update(zone);

mm/page_alloc.c

@@ -5129,7 +5129,6 @@ static void build_zonelists(pg_data_t *pgdat)
 static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
 static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
 static DEFINE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);
-static void setup_zone_pageset(struct zone *zone);
 
 /*
  * Global mutex to protect against size modification of zonelists
@@ -5209,20 +5208,14 @@ build_all_zonelists_init(void)
  * Called with zonelists_mutex held always
  * unless system_state == SYSTEM_BOOTING.
  *
- * __ref due to (1) call of __meminit annotated setup_zone_pageset
- * [we're only called with non-NULL zone through __meminit paths] and
- * (2) call of __init annotated helper build_all_zonelists_init
+ * __ref due to call of __init annotated helper build_all_zonelists_init
  * [protected by SYSTEM_BOOTING].
  */
-void __ref build_all_zonelists(pg_data_t *pgdat, struct zone *zone)
+void __ref build_all_zonelists(pg_data_t *pgdat)
 {
 	if (system_state == SYSTEM_BOOTING) {
 		build_all_zonelists_init();
 	} else {
-#ifdef CONFIG_MEMORY_HOTPLUG
-		if (zone)
-			setup_zone_pageset(zone);
-#endif
 		/* we have to stop all cpus to guarantee there is no user
 		   of zonelist */
 		stop_machine_cpuslocked(__build_all_zonelists, pgdat, NULL);
@@ -5496,7 +5489,7 @@ static void __meminit zone_pageset_init(struct zone *zone, int cpu)
 	pageset_set_high_and_batch(zone, pcp);
 }
 
-static void __meminit setup_zone_pageset(struct zone *zone)
+void __meminit setup_zone_pageset(struct zone *zone)
 {
 	int cpu;
 	zone->pageset = alloc_percpu(struct per_cpu_pageset);