linux-kernel - Re: [PATCH] powerpc: Move a dereference below a NULL test

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Date:   Wed, 26 Sep 2018 22:06:21 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Christophe LEROY <christophe.leroy@....fr>
CC:     <paulus@...ba.org>, <benh@...nel.crashing.org>,
        <mpe@...erman.id.au>, <linuxppc-dev@...ts.ozlabs.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc: Move a dereference below a NULL test

On 2018/9/26 21:58, Christophe LEROY wrote:
>
>
> Le 26/09/2018 à 13:46, zhong jiang a écrit :
>> It is safe to move dereference below a NULL test.
>>
>> Signed-off-by: zhong jiang <zhongjiang@...wei.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);
>
> But by doing this, you change the meaning of the following warning. Is that what you want ? In that case the text of the WARN_ONCE() should be changed, because the mismatch is not only on lookup now.
>
Yep, I forget the WARN_ONCE. I think we should just remove it. Thought?

Thanks,
zhong jiang
> Christophe
>
>>         WARN_ONCE(cache && cache->level != level,
>>             "cache level mismatch on lookup (got %d, expected %d)\n",
>>             cache->level, level);
>>   -    if (!cache)
>> -        cache = cache_do_one_devnode(node, level);
>> -
>>       return cache;
>>   }
>>  
>
> .
>