linux-kernel - Re: [PATCH] slab: initialize unused alien cache entry as NULL at alloc_alien

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Date:	Tue, 22 Dec 2009 13:40:34 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Haicheng Li <haicheng.li@...ux.intel.com>
Cc:	linux-mm@...ck.org, Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org,
	stable@...nel.org
Subject: Re: [PATCH] slab: initialize unused alien cache entry as NULL at alloc_alien_cache().

Haicheng Li <haicheng.li@...ux.intel.com> writes:

> Memory hotplug would online new node in runtime, then reap timer will
> add this new node as a reap node. In such case, for each existing
> kmem_list, we need to ensure that the alien cache entry corresponding
> to this new added node is NULL. Otherwise, it might cause BUG when
> reap_alien() affecting the new added node.
>
> Signed-off-by: Haicheng Li <haicheng.li@...ux.intel.com>

Acked-by: Andi Kleen <ak@...ux.intel.com>
IMHO a 2.6.33 and even stable candidate

-Andi


> ---
>  mm/slab.c |    7 +++----
>  1 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 7dfa481..a9486a0 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -966,18 +966,17 @@ static void *alternate_node_alloc(struct kmem_cache *, gfp_t);
>  static struct array_cache **alloc_alien_cache(int node, int limit, gfp_t gfp)
>  {
>  	struct array_cache **ac_ptr;
> -	int memsize = sizeof(void *) * nr_node_ids;
> +	int memsize = sizeof(void *) * MAX_NUMNODES;
>  	int i;
>
>  	if (limit > 1)
>  		limit = 12;
>  	ac_ptr = kmalloc_node(memsize, gfp, node);
>  	if (ac_ptr) {
> +		memset(ac_ptr, 0, memsize);
>  		for_each_node(i) {
> -			if (i == node || !node_online(i)) {
> -				ac_ptr[i] = NULL;
> +			if (i == node || !node_online(i))
>  				continue;
> -			}
>  			ac_ptr[i] = alloc_arraycache(node, limit, 0xbaadf00d, gfp);
>  			if (!ac_ptr[i]) {
>  				for (i--; i >= 0; i--)
> -- 
> 1.6.0.rc1

-- 
ak@...ux.intel.com -- Speaking for myself only.
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