Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <5BAB9ACF.6040102@huawei.com>
Date:   Wed, 26 Sep 2018 22:42:23 +0800
From:   zhong jiang <zhongjiang@huawei.com>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1
MIME-Version: 1.0
To:     =?ISO-8859-1?Q?Michal_Such=E1nek?= <msuchanek@suse.de>
CC:     <paulus@samba.org>, <benh@kernel.crashing.org>,
        <mpe@ellerman.id.au>, <linuxppc-dev@lists.ozlabs.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] powerpc: Move a dereference below a NULL test
References: <1537962368-14019-1-git-send-email-zhongjiang@huawei.com> <20180926162232.250c0090@naga>
In-Reply-To: <20180926162232.250c0090@naga>
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 2018/9/26 22:22, Michal Such?nek wrote:
> On Wed, 26 Sep 2018 19:46:08 +0800
> zhong jiang <zhongjiang@huawei.com> wrote:
>
>> It is safe to move dereference below a NULL test.
>>
>> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
>> ---
>>  arch/powerpc/kernel/cacheinfo.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/kernel/cacheinfo.c
>> b/arch/powerpc/kernel/cacheinfo.c index a8f20e5..7f19714 100644
>> --- a/arch/powerpc/kernel/cacheinfo.c
>> +++ b/arch/powerpc/kernel/cacheinfo.c
>> @@ -401,14 +401,13 @@ static struct cache
>> *cache_lookup_or_instantiate(struct device_node *node, struct cache
>> *cache; 
>>  	cache = cache_lookup_by_node(node);
>> +	if (!cache)
>> +		cache = cache_do_one_devnode(node, level);
>>  
>>  	WARN_ONCE(cache && cache->level != level,
> This has also null test so cache should be dereferenced only when
> non-null here.
:-[ ,  you're right.  I forget WARN_ONCE.  please ignore the patch.

Sincerely,
zhong jiang
> Thanks
>
> Michal
>
> .
>