Commit a1e565aa authored Feb 22, 2013 by Tang Chen Committed by Linus Torvalds Feb 23, 2013

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 <tangchen@cn.fujitsu.com>
Reviewed-by: Wen Congyang <wency@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: Jianguo Wu <wujianguo@huawei.com>
Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Wu Jianguo <wujianguo@huawei.com>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent d822b86a

mm/memory_hotplug.c

+16 −8

Original line number	Diff line number	Diff line
		@@ -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 = NODE_DATA(nid);
		if (!pgdat) {
		pgdat = arch_alloc_nodedata(nid);
		if (!pgdat)
		return NULL;

		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

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