[PART1 Patch 2/3] memory_hotplug: handle empty zone when online_movable/online_kernel

[Wen Congyang <wency@xxxxxxxxxxxxxx>]

From: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>

make online_movable/online_kernel can empty a zone
or can move memory to a empty zone.

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
---
 mm/memory_hotplug.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 6 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 4900025..e6ec8c2 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -227,8 +227,17 @@ static void resize_zone(struct zone *zone, unsigned long start_pfn,
 
 	zone_span_writelock(zone);
 
-	zone->zone_start_pfn = start_pfn;
-	zone->spanned_pages = end_pfn - start_pfn;
+	if (end_pfn - start_pfn) {
+		zone->zone_start_pfn = start_pfn;
+		zone->spanned_pages = end_pfn - start_pfn;
+	} else {
+		/*
+		 * make it consist as free_area_init_core(),
+		 * if spanned_pages = 0, then keep start_pfn = 0
+		 */
+		zone->zone_start_pfn = 0;
+		zone->spanned_pages = 0;
+	}
 
 	zone_span_writeunlock(zone);
 }
@@ -244,10 +253,19 @@ static void fix_zone_id(struct zone *zone, unsigned long start_pfn,
 		set_page_links(pfn_to_page(pfn), zid, nid, pfn);
 }
 
-static int move_pfn_range_left(struct zone *z1, struct zone *z2,
+static int __meminit move_pfn_range_left(struct zone *z1, struct zone *z2,
 		unsigned long start_pfn, unsigned long end_pfn)
 {
+	int ret;
 	unsigned long flags;
+	unsigned long z1_start_pfn;
+
+	if (!z1->wait_table) {
+		ret = init_currently_empty_zone(z1, start_pfn,
+			end_pfn - start_pfn, MEMMAP_HOTPLUG);
+		if (ret)
+			return ret;
+	}
 
 	pgdat_resize_lock(z1->zone_pgdat, &flags);
 
@@ -261,7 +279,13 @@ static int move_pfn_range_left(struct zone *z1, struct zone *z2,
 	if (end_pfn <= z2->zone_start_pfn)
 		goto out_fail;
 
-	resize_zone(z1, z1->zone_start_pfn, end_pfn);
+	/* use start_pfn for z1's start_pfn if z1 is empty */
+	if (z1->spanned_pages)
+		z1_start_pfn = z1->zone_start_pfn;
+	else
+		z1_start_pfn = start_pfn;
+
+	resize_zone(z1, z1_start_pfn, end_pfn);
 	resize_zone(z2, end_pfn, z2->zone_start_pfn + z2->spanned_pages);
 
 	pgdat_resize_unlock(z1->zone_pgdat, &flags);
@@ -274,10 +298,19 @@ out_fail:
 	return -1;
 }
 
-static int move_pfn_range_right(struct zone *z1, struct zone *z2,
+static int __meminit move_pfn_range_right(struct zone *z1, struct zone *z2,
 		unsigned long start_pfn, unsigned long end_pfn)
 {
+	int ret;
 	unsigned long flags;
+	unsigned long z2_end_pfn;
+
+	if (!z2->wait_table) {
+		ret = init_currently_empty_zone(z2, start_pfn,
+			end_pfn - start_pfn, MEMMAP_HOTPLUG);
+		if (ret)
+			return ret;
+	}
 
 	pgdat_resize_lock(z1->zone_pgdat, &flags);
 
@@ -291,8 +324,14 @@ static int move_pfn_range_right(struct zone *z1, struct zone *z2,
 	if (start_pfn >= z1->zone_start_pfn + z1->spanned_pages)
 		goto out_fail;
 
+	/* use end_pfn for z2's end_pfn if z2 is empty */
+	if (z2->spanned_pages)
+		z2_end_pfn = z2->zone_start_pfn + z2->spanned_pages;
+	else
+		z2_end_pfn = end_pfn;
+
 	resize_zone(z1, z1->zone_start_pfn, start_pfn);
-	resize_zone(z2, start_pfn, z2->zone_start_pfn + z2->spanned_pages);
+	resize_zone(z2, start_pfn, z2_end_pfn);
 
 	pgdat_resize_unlock(z1->zone_pgdat, &flags);
 
-- 
1.8.0

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