[PATCH 4.2 119/120] memory-hotplug: add hot-added memory ranges to memblock before allocate node_data for a node.

Greg Kroah-Hartman
2015-09-19T17:53:04Z

From: Tang Chen <tangchen@cn.fujitsu.com>

commit 7f36e3e56db1ae75d1e157011b3cb2e0957f0a7e upstream.

Commit f9126ab9241f ("memory-hotplug: fix wrong edge when hot add a new
node") hot-added memory range to memblock, after creating pgdat for 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.

Initmem setup node 5 [mem 0x0000000000000000-0xffffffffffffffff]
On node 5 totalpages: 0
Built 5 zonelists in Node order, mobility grouping on. Total pages: 32588823
Policy zone: Normal
init_memory_mapping: [mem 0x60000000000-0x607ffffffff]

The solution is simple, just add the memory range to memblock a little
earlier, before hotadd_new_pgdat().

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/memory_hotplug.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1248,6 +1248,14 @@ int __ref add_memory(int nid, u64 start,

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 removed 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,

/* 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();