From a1e565aa3cfc7c6252cabc93de8391d12b9216aa Mon Sep 17 00:00:00 2001 From: Tang Chen Date: Fri, 22 Feb 2013 16:33:18 -0800 Subject: [PATCH] memory-hotplug: do not allocate pgdat if it was not freed when offline. 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. The idea is from Wen Congyang. NOTE: If we don't reset pgdat to 0, the WARN_ON in free_area_init_node() will be triggered. [akpm@linux-foundation.org: fix warning when CONFIG_NEED_MULTIPLE_NODES=n] [akpm@linux-foundation.org: fix the warning again again] Signed-off-by: Tang Chen Reviewed-by: Wen Congyang Cc: KOSAKI Motohiro Cc: Jiang Liu Cc: Jianguo Wu Cc: Kamezawa Hiroyuki Cc: Lai Jiangshan Cc: Wu Jianguo Cc: Yasuaki Ishimatsu Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 3409134..e189b1f 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1017,11 +1017,14 @@ 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 */ @@ -1074,7 +1077,8 @@ out: int __ref add_memory(int nid, u64 start, u64 size) { pg_data_t *pgdat = NULL; - int new_pgdat = 0; + bool new_pgdat; + bool new_node; struct resource *res; int ret; @@ -1085,12 +1089,16 @@ int __ref add_memory(int nid, u64 start, u64 size) if (!res) goto out; - if (!node_online(nid)) { + { /* Stupid hack to suppress address-never-null warning */ + void *p = NODE_DATA(nid); + new_pgdat = !p; + } + new_node = !node_online(nid); + if (new_node) { pgdat = hotadd_new_pgdat(nid, start); ret = -ENOMEM; if (!pgdat) goto error; - new_pgdat = 1; } /* call arch's memory hotadd */ @@ -1102,7 +1110,7 @@ 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 -- 2.7.4