Since there is no way to guarentee the address of pgdat/zone is not
on stack of any kernel threads or used by other kernel objects
without reference counting or other symchronizing method, we cannot
reset node_data and free pgdat when offlining a node. Just reset pgdat
to 0 and reuse the memory when the node is online again.
The problem is suggested by Kamezawa Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
The idea is from Wen Congyang <we...@cn.fujitsu.com>
NOTE: If we don't reset pgdat to 0, the WARN_ON in free_area_init_node()
will be triggered.
Signed-off-by: Tang Chen <tangc...@cn.fujitsu.com>
Reviewed-by: Wen Congyang <we...@cn.fujitsu.com>
---
mm/memory_hotplug.c | 20 ++++++++++++--------
1 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 8b67752..8aa2b56 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1015,11 +1015,14 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64
start)
unsigned long zholes_size[MAX_NR_ZONES] = {0};
unsigned long start_pfn = start >> PAGE_SHIFT;
- pgdat = arch_alloc_nodedata(nid);
- if (!pgdat)
- return NULL;
+ pgdat = NODE_DATA(nid);
+ if (!pgdat) {
+ pgdat = arch_alloc_nodedata(nid);
+ if (!pgdat)
+ return NULL;
- arch_refresh_nodedata(nid, pgdat);
+ arch_refresh_nodedata(nid, pgdat);
+ }
/* we can use NODE_DATA(nid) from here */
@@ -1072,7 +1075,7 @@ out:
int __ref add_memory(int nid, u64 start, u64 size)
{
pg_data_t *pgdat = NULL;
- int new_pgdat = 0;
+ int new_pgdat = 0, new_node = 0;
struct resource *res;
int ret;
@@ -1083,12 +1086,13 @@ int __ref add_memory(int nid, u64 start, u64 size)
if (!res)
goto out;
- if (!node_online(nid)) {
+ new_pgdat = NODE_DATA(nid) ? 0 : 1;
+ new_node = node_online(nid) ? 0 : 1;
+ if (new_node) {
pgdat = hotadd_new_pgdat(nid, start);
ret = -ENOMEM;
if (!pgdat)
goto error;
- new_pgdat = 1;
}
/* call arch's memory hotadd */
@@ -1100,7 +1104,7 @@ int __ref add_memory(int nid, u64 start, u64 size)
/* we online node here. we can't roll back from here. */
node_set_online(nid);
- if (new_pgdat) {
+ if (new_node) {
ret = register_one_node(nid);
/*
* If sysfs file of new node can't create, cpu on the node
--
1.7.1
--
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