Re: [patch] cpu: remove some dead code in store_cache_disable()

["Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>]

On 04/19/2012 04:32 PM, Borislav Petkov wrote:

> On Thu, Apr 19, 2012 at 01:48:02PM +0530, Srivatsa S. Bhat wrote:
>> On 04/19/2012 12:30 PM, Dan Carpenter wrote:
>>
>>> amd_set_l3_disable_slot() never returns -EEXIST, it only returns -EINVAL
>>> or zero.
>>>
>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>>
>>> diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
>>> index 73d08ed..7b4e294 100644
>>> --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
>>> +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
>>> @@ -466,12 +466,9 @@ static ssize_t store_cache_disable(struct _cpuid4_info *this_leaf,
>>>  		return -EINVAL;
>>>
>>>  	err = amd_set_l3_disable_slot(this_leaf->base.nb, cpu, slot, val);
>>> -	if (err) {
>>> -		if (err = -EEXIST)
>>> -			printk(KERN_WARNING "L3 disable slot %d in use!\n",
>>> -					    slot);
>>> +	if (err)
>>>  		return err;
>>> -	}
>>> +
>>>  	return count;
>>>  }
>>>
>>
>>
>> Looking at the comments around the code and the print statement your patch
>> is trying to remove, I wonder if it would be more appropriate to return
>> -EEXIST in amd_set_l3_disable_slot(), like this:
>>
>> ---
>> From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>> Subject: [PATCH] cpu: Fix error return code in amd_set_l3_disable_slot()
>>
>> If the L3 disable slot is already in use, return -EEXIST instead of -EINVAL.
>> The caller, store_cache_disable(), checks this return value to print an
>> appropriate warning.
>>
>> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
>> ---
>>
>>  arch/x86/kernel/cpu/intel_cacheinfo.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
>> index 73d08ed..0b49e29 100644
>> --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
>> +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
>> @@ -433,7 +433,7 @@ int amd_set_l3_disable_slot(struct amd_northbridge *nb, int cpu, unsigned slot,
>>  	/*  check if @slot is already used or the index is already disabled */
>>  	ret = amd_get_l3_disable_slot(nb, slot);
>>  	if (ret >= 0)
>> -		return -EINVAL;
>> +		return -EEXIST;
>>  
>>  	if (index > nb->l3_cache.indices)
>>  		return -EINVAL;
> 
> Well, let's see, there's 8cc1176e5de534d55cb26ff0cef3fd0d6ad8c3c0 which
> was intending at looking at -EEXIST when it gets returned but forgot to
> return it at the end. Crap. Somebody should b*tchslap its author... oh,
> that's me.
> 
> Good catch guys, thanks. I'll take a bit enhanced version of Srivatsa's
> patch because it goes in the way of what was originally intended. The
> enhanced version returns -EEXIST for the other slot too when we're
> disabling the same index, see below:
> 

> --

> From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
> Date: Thu, 19 Apr 2012 12:35:08 +0200
> Subject: [PATCH] x86, intel_cacheinfo: Fix error return code in amd_set_l3_disable_slot()
> 
> If the L3 disable slot is already in use, return -EEXIST instead of
> -EINVAL. The caller, store_cache_disable(), checks this return value to
> print an appropriate warning.
> 
> Also, we want to signal with -EEXIST that the current index we're
> disabling has actually been already disabled on the node:
> 
> $ echo 12 > /sys/devices/system/cpu/cpu3/cache/index3/cache_disable_0
> $ echo 12 > /sys/devices/system/cpu/cpu3/cache/index3/cache_disable_0
> -bash: echo: write error: File exists
> $ echo 12 > /sys/devices/system/cpu/cpu3/cache/index3/cache_disable_1
> -bash: echo: write error: File exists
> $ echo 12 > /sys/devices/system/cpu/cpu5/cache/index3/cache_disable_1
> -bash: echo: write error: File exists
> 
> The old code would say
> 
> -bash: echo: write error: Invalid argument
> 
> for disable slot 1 when playing the example above with no output in
> dmesg, which is clearly misleading.
> 
> Cc: <stable@vger.kernel.org>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
> Link: http://lkml.kernel.org/r/20120419070053.GB16645@elgon.mountain
> [Boris: add testing for the other index too]
> Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
> ---
>  arch/x86/kernel/cpu/intel_cacheinfo.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
> index 73d08ed98a64..b8f3653dddbc 100644
> --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
> +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
> @@ -433,14 +433,14 @@ int amd_set_l3_disable_slot(struct amd_northbridge *nb, int cpu, unsigned slot,
>  	/*  check if @slot is already used or the index is already disabled */
>  	ret = amd_get_l3_disable_slot(nb, slot);
>  	if (ret >= 0)
> -		return -EINVAL;
> +		return -EEXIST;
> 
>  	if (index > nb->l3_cache.indices)
>  		return -EINVAL;
> 
>  	/* check whether the other slot has disabled the same index already */
>  	if (index = amd_get_l3_disable_slot(nb, !slot))
> -		return -EINVAL;
> +		return -EEXIST;
> 
>  	amd_l3_disable_index(nb, cpu, slot, index);
> 
> @@ -468,8 +468,8 @@ static ssize_t store_cache_disable(struct _cpuid4_info *this_leaf,
>  	err = amd_set_l3_disable_slot(this_leaf->base.nb, cpu, slot, val);
>  	if (err) {
>  		if (err = -EEXIST)
> -			printk(KERN_WARNING "L3 disable slot %d in use!\n",
> -					    slot);
> +			pr_warning("L3 slot %d in use/index already disabled!\n",
> +				   slot);
>  		return err;
>  	}
>  	return count;


Wow, that's even better! Thanks :-)

Regards,
Srivatsa S. Bhat