netdev - Re: [PATCH -mmotm 12/30] selinux: tag avc cache alloc as non-critical

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Date:	Thu, 15 Jul 2010 19:51:32 +0800
From:	Xiaotian Feng <dfeng@...hat.com>
To:	Mitchell Erblich <erblichs@...thlink.net>
CC:	linux-mm@...ck.org, linux-nfs@...r.kernel.org,
	netdev@...r.kernel.org, riel@...hat.com, cl@...ux-foundation.org,
	a.p.zijlstra@...llo.nl, linux-kernel@...r.kernel.org,
	lwang@...hat.com, penberg@...helsinki.fi,
	akpm@...ux-foundation.org, davem@...emloft.net
Subject: Re: [PATCH -mmotm 12/30] selinux: tag avc cache alloc as non-critical

On 07/13/2010 06:55 PM, Mitchell Erblich wrote:
>
> On Jul 13, 2010, at 3:19 AM, Xiaotian Feng wrote:
>
>>  From 6c3a91091b2910c23908a9f9953efcf3df14e522 Mon Sep 17 00:00:00 2001
>> From: Xiaotian Feng<dfeng@...hat.com>
>> Date: Tue, 13 Jul 2010 11:02:41 +0800
>> Subject: [PATCH 12/30] selinux: tag avc cache alloc as non-critical
>>
>> Failing to allocate a cache entry will only harm performance not correctness.
>> Do not consume valuable reserve pages for something like that.
>>
>> Signed-off-by: Peter Zijlstra<a.p.zijlstra@...llo.nl>
>> Signed-off-by: Suresh Jayaraman<sjayaraman@...e.de>
>> Signed-off-by: Xiaotian Feng<dfeng@...hat.com>
>> ---
>> security/selinux/avc.c |    2 +-
>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/security/selinux/avc.c b/security/selinux/avc.c
>> index 3662b0f..9029395 100644
>> --- a/security/selinux/avc.c
>> +++ b/security/selinux/avc.c
>> @@ -284,7 +284,7 @@ static struct avc_node *avc_alloc_node(void)
>> {
>> 	struct avc_node *node;
>>
>> -	node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC);
>> +	node = kmem_cache_zalloc(avc_node_cachep, GFP_ATOMIC|__GFP_NOMEMALLOC);
>> 	if (!node)
>> 		goto out;
>>
>> -- 
>> 1.7.1.1
>>
>
> Why not just replace GFP_ATOMIC with GFP_NOWAIT?
>
> This would NOT consume the valuable last pages.

But replace GFP_ATOMIC with GFP_NOWAIT can not prevent avc_alloc_node 
consume reserved pages.

>
> Mitchell Erblich
>> --
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>
>

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