linux-kernel - [PATCH 1/2] memory-hotplug: fix wrong edge when hot add a new node

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Date:	Tue, 11 Aug 2015 15:26:33 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	<izumi.taku@...fujitsu.com>, Tang Chen <tangchen@...fujitsu.com>,
	Gu Zheng <guz.fnst@...fujitsu.com>
CC:	Xishi Qiu <qiuxishi@...wei.com>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] memory-hotplug: fix wrong edge when hot add a new node

When we add a new node, the edge of memory may be wrong.

e.g. system has 4 nodes, and node3 is movable, node3 mem:[24G-32G],

1. hotremove the node3,
2. then hotadd node3 with a part of memory, mem:[26G-30G],
3. call hotadd_new_pgdat()
	free_area_init_node()
		get_pfn_range_for_nid() 
4. it will return wrong start_pfn and end_pfn, because we have not
update the memblock.


This patch also fix another bug, please see
http://marc.info/?l=linux-kernel&m=142961156129456&w=2

Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
---
 mm/memory_hotplug.c | 3 +++
 mm/page_alloc.c     | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 26fbba7..11f26cc 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1269,6 +1269,7 @@ int __ref add_memory(int nid, u64 start, u64 size)
 
 	/* create new memmap entry */
 	firmware_map_add_hotplug(start, start + size, "System RAM");
+	memblock_add_node(start, size, nid);
 
 	goto out;
 
@@ -2005,6 +2006,8 @@ void __ref remove_memory(int nid, u64 start, u64 size)
 
 	/* remove memmap entry */
 	firmware_map_remove(start, start + size, "System RAM");
+	memblock_free(start, size);
+	memblock_remove(start, size);
 
 	arch_remove_memory(start, size);
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1b91d37..7ca12b9 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5050,6 +5050,10 @@ static unsigned long __meminit zone_spanned_pages_in_node(int nid,
 {
 	unsigned long zone_start_pfn, zone_end_pfn;
 
+	/* When hotadd a new node, the node should be empty */
+	if (!node_start_pfn && !node_end_pfn)
+		return 0;
+
 	/* Get the start and end of the zone */
 	zone_start_pfn = arch_zone_lowest_possible_pfn[zone_type];
 	zone_end_pfn = arch_zone_highest_possible_pfn[zone_type];
@@ -5113,6 +5117,10 @@ static unsigned long __meminit zone_absent_pages_in_node(int nid,
 	unsigned long zone_high = arch_zone_highest_possible_pfn[zone_type];
 	unsigned long zone_start_pfn, zone_end_pfn;
 
+	/* When hotadd a new node, the node should be empty */
+	if (!node_start_pfn && !node_end_pfn)
+		return 0;
+
 	zone_start_pfn = clamp(node_start_pfn, zone_low, zone_high);
 	zone_end_pfn = clamp(node_end_pfn, zone_low, zone_high);
 
-- 
2.0.0


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