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Date: Thu, 23 Jun 2011 10:31:06 +0900
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
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To: rientjes@google.com
CC: akpm@linux-foundation.org, torvalds@linux-foundation.org,
        kamezawa.hiroyu@jp.fujitsu.com, mgorman@suse.de,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch 1/2] mm, hotplug: fix error handling in mem_online_node()
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(2011/06/23 10:13), David Rientjes wrote:
> 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.
> 
> Signed-off-by: David Rientjes <rientjes@google.com>

Nice catch.

The fault was introduced by commit cf23422b9d76(cpu/mem hotplug: enable CPUs
online before local memory online) iow v2.6.35.

 Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>


> ---
>  mm/memory_hotplug.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> --- 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;
>  	}
> 
> --
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