From 959ecc48fc7506b9d7825ea70e40d92d9b308033 Mon Sep 17 00:00:00 2001 From: KAMEZAWA Hiroyuki Date: Wed, 15 Jun 2011 15:08:38 -0700 Subject: mm/memory_hotplug.c: fix building of node hotplug zonelist During memory hotplug we refresh zonelists when we online a page in a new zone. It means that the node's zonelist is not initialized until pages are onlined. So for example, "nid" passed by MEM_GOING_ONLINE notifier will point to NODE_DATA(nid) which has no zone fallback list. Moreover, if we hot-add cpu-only nodes, alloc_pages() will do no fallback. This patch makes a zonelist when a new pgdata is available. Note: in production, at fujitsu, memory should be onlined before cpu and our server didn't have any memory-less nodes and had no problems. But recent changes in MEM_GOING_ONLINE+page_cgroup will access not initialized zonelist of node. Anyway, there are memory-less node and we need some care. Signed-off-by: KAMEZAWA Hiroyuki Cc: Mel Gorman Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 9f646374e32f..02159c755136 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -494,6 +494,12 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start) /* init node's zones as empty zones, we don't have any present pages.*/ free_area_init_node(nid, zones_size, start_pfn, zholes_size); + /* + * The node we allocated has no zone fallback lists. For avoiding + * to access not-initialized zonelist, build here. + */ + build_all_zonelists(NULL); + return pgdat; } -- cgit v1.2.3 From 7553e8f2d5161a2b7a9b7a9f37be1b77e735552f Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Wed, 22 Jun 2011 18:13:01 -0700 Subject: mm, hotplug: fix error handling in mem_online_node() The error handling in mem_online_node() is incorrect: hotadd_new_pgdat() returns NULL if the new pgdat could not have been allocated and a pointer to it otherwise. mem_online_node() should fail if hotadd_new_pgdat() fails, not the inverse. This fixes an issue when memoryless nodes are not onlined and their sysfs interface is not registered when their first cpu is brought up. The bug was introduced by commit cf23422b9d76 ("cpu/mem hotplug: enable CPUs online before local memory online") iow v2.6.35. Signed-off-by: David Rientjes Reviewed-by: KOSAKI Motohiro Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 02159c755136..78dba9f04b5b 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -521,7 +521,7 @@ int mem_online_node(int nid) lock_memory_hotplug(); pgdat = hotadd_new_pgdat(nid, 0); - if (pgdat) { + if (!pgdat) { ret = -ENOMEM; goto out; } -- cgit v1.2.3 From f957db4fcdd8f03e186aa8f041f4049e76ab741c Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Wed, 22 Jun 2011 18:13:04 -0700 Subject: mm, hotplug: protect zonelist building with zonelists_mutex Commit 959ecc48fc75 ("mm/memory_hotplug.c: fix building of node hotplug zonelist") does not protect the build_all_zonelists() call with zonelists_mutex as needed. This can lead to races in constructing zonelist ordering if a concurrent build is underway. Protecting this with lock_memory_hotplug() is insufficient since zonelists can be rebuild though sysfs as well. Signed-off-by: David Rientjes Reviewed-by: KOSAKI Motohiro Signed-off-by: Linus Torvalds --- mm/memory_hotplug.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'mm/memory_hotplug.c') diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 78dba9f04b5b..c46887b5a11e 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -498,7 +498,9 @@ static pg_data_t __ref *hotadd_new_pgdat(int nid, u64 start) * The node we allocated has no zone fallback lists. For avoiding * to access not-initialized zonelist, build here. */ + mutex_lock(&zonelists_mutex); build_all_zonelists(NULL); + mutex_unlock(&zonelists_mutex); return pgdat; } -- cgit v1.2.3