The commit below adds hot-added memory range to memblock, after
creating pgdat for new node.
commit f9126ab9241f66562debf69c2c9d8fee32ddcc53
Author: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Date: Fri Aug 14 15:35:16 2015 -0700
memory-hotplug: fix wrong edge when hot add a new node
But there is a problem:
add_memory()
|--> hotadd_new_pgdat()
|--> free_area_init_node()
|--> get_pfn_range_for_nid()
|--> find start_pfn and end_pfn in memblock
|--> ......
|--> memblock_add_node(start, size, nid) -------- Here, just too late.
get_pfn_range_for_nid() will find that start_pfn and end_pfn are both 0.
As a result, when adding memory, dmesg will give the following wrong message.
[ 2007.577000] Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]
[ 2007.584000] On node 5 totalpages: 0
[ 2007.585000] Built 5 zonelists in Node order, mobility grouping on. Total pages: 32588823
[ 2007.594000] Policy zone: Normal
[ 2007.598000] init_memory_mapping: [mem 0x60000000000-0x607ffffffff]
The solution is simple, just add the memory range to memblock a little earlier,
before hotadd_new_pgdat().
Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6da82bc..9b78aff 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1248,6 +1248,14 @@ int __ref add_memory(int nid, u64 start, u64 size)
mem_hotplug_begin();
+ /*
+ * Add new range to memblock so that when hotadd_new_pgdat() is called to
+ * allocate new pgdat, get_pfn_range_for_nid() will be able to find this
+ * new range and calculate total pages correctly. The range will be remove
+ * at hot-remove time.
+ */
+ memblock_add_node(start, size, nid);
+
new_node = !node_online(nid);
if (new_node) {
pgdat = hotadd_new_pgdat(nid, start);
@@ -1277,7 +1285,6 @@ 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;
@@ -1286,6 +1293,7 @@ error:
if (new_pgdat)
rollback_node_hotadd(nid, pgdat);
release_memory_resource(res);
+ memblock_remove(start, size);
out:
mem_hotplug_done();
--
1.8.3.1
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