mm, hotplug: fix error handling in mem_online_node()

commit 7553e8f2d5161a2b7a9b7a9f37be1b77e735552f upstream.

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 <rientjes@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9ca1d604f7cd74aab7a897de22e0784a8c0bcb45..fc5e0ba71c3b7a5c8380b23b839532007578399f 100644 (file)
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -518,7 +518,7 @@ int mem_online_node(int nid)
 
        lock_memory_hotplug();
        pgdat = hotadd_new_pgdat(nid, 0);
-       if (pgdat) {
+       if (!pgdat) {
                ret = -ENOMEM;
                goto out;
        }