During online_pages phase, pgdat->nr_zones will be updated in case this
zone is empty.
Currently the online_pages phase is protected by the global lock
mem_hotplug_begin(), which ensures there is no contention during the
update of nr_zones. But this global lock introduces scalability issues.
This patch is a preparation for removing the global lock during
online_pages phase. Also this patch changes the documentation of
node_size_lock to include the protectioin of nr_zones.
Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
---
v2:
* commit log changes
* modify the code in move_pfn_range_to_zone() instead of in
init_currently_empty_zone()
* documentation change
---
include/linux/mmzone.h | 7 ++++---
mm/memory_hotplug.c | 5 ++---
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 68d7b558924b..1bb749bee284 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -636,9 +636,10 @@ typedef struct pglist_data {
#endif
#if defined(CONFIG_MEMORY_HOTPLUG) || defined(CONFIG_DEFERRED_STRUCT_PAGE_INIT)
/*
- * Must be held any time you expect node_start_pfn, node_present_pages
- * or node_spanned_pages stay constant. Holding this will also
- * guarantee that any pfn_valid() stays that way.
+ * Must be held any time you expect node_start_pfn,
+ * node_present_pages, node_spanned_pages or nr_zones stay constant.
+ * Holding this will also guarantee that any pfn_valid() stays that
+ * way.
*
* pgdat_resize_lock() and pgdat_resize_unlock() are provided to
* manipulate node_size_lock without checking for CONFIG_MEMORY_HOTPLUG
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 61972da38d93..f626e7e5f57b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -742,14 +742,13 @@ void __ref move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
int nid = pgdat->node_id;
unsigned long flags;
- if (zone_is_empty(zone))
- init_currently_empty_zone(zone, start_pfn, nr_pages);
-
clear_zone_contiguous(zone);
/* TODO Huh pgdat is irqsave while zone is not. It used to be like that before */
pgdat_resize_lock(pgdat, &flags);
zone_span_writelock(zone);
+ if (zone_is_empty(zone))
+ init_currently_empty_zone(zone, start_pfn, nr_pages);
resize_zone_range(zone, start_pfn, nr_pages);
zone_span_writeunlock(zone);
resize_pgdat_range(pgdat, start_pfn, nr_pages);
--
2.15.1
