[PATCH 1/1] pseries/hotplug-memory.c: Change rc variable to bool

[PATCH 1/1] pseries/hotplug-memory.c: Change rc variable to bool

[Leonardo Bras]

Changes the return variable to bool (as the return value) and
avoids doing a ternary operation before returning.

Also, since rc will always be true, there is no need to do
rc &= bool, as (true && X) will result in X.

Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/hotplug-memory.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 8e700390f3d6..392deb4855e5 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -338,7 +338,7 @@ static int pseries_remove_mem_node(struct device_node *np)
 static bool lmb_is_removable(struct drmem_lmb *lmb)
 {
 	int i, scns_per_block;
-	int rc = 1;
+	bool rc = true;
 	unsigned long pfn, block_sz;
 	u64 phys_addr;
 
@@ -363,11 +363,11 @@ static bool lmb_is_removable(struct drmem_lmb *lmb)
 		if (!pfn_present(pfn))
 			continue;
 
-		rc &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
+		rc = is_mem_section_removable(pfn, PAGES_PER_SECTION);
 		phys_addr += MIN_MEMORY_BLOCK_SIZE;
 	}
 
-	return rc ? true : false;
+	return rc;
 }
 
 static int dlpar_add_lmb(struct drmem_lmb *);
-- 
2.20.1

Re: [PATCH 1/1] pseries/hotplug-memory.c: Change rc variable to bool

[David Hildenbrand]

On 02.08.19 01:10, Leonardo Bras wrote:
> Changes the return variable to bool (as the return value) and
> avoids doing a ternary operation before returning.
> 
> Also, since rc will always be true, there is no need to do
> rc &= bool, as (true && X) will result in X.
> 
> Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/hotplug-memory.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 8e700390f3d6..392deb4855e5 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -338,7 +338,7 @@ static int pseries_remove_mem_node(struct device_node *np)
>  static bool lmb_is_removable(struct drmem_lmb *lmb)
>  {
>  	int i, scns_per_block;
> -	int rc = 1;
> +	bool rc = true;
>  	unsigned long pfn, block_sz;
>  	u64 phys_addr;
>  
> @@ -363,11 +363,11 @@ static bool lmb_is_removable(struct drmem_lmb *lmb)
>  		if (!pfn_present(pfn))
>  			continue;
>  
> -		rc &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
> +		rc = is_mem_section_removable(pfn, PAGES_PER_SECTION);

No, that's wrong.

If is_mem_section_removable() is false in the first iteration but true
in the last iteration, you would return true instead of false, which
introduced a bug. We have to AND all sub-results, not simply use the
last one.

>  		phys_addr += MIN_MEMORY_BLOCK_SIZE;
>  	}
>  
> -	return rc ? true : false;
> +	return rc;
>  }
>  
>  static int dlpar_add_lmb(struct drmem_lmb *);
> 


-- 

Thanks,

David / dhildenb

Re: [PATCH 1/1] pseries/hotplug-memory.c: Change rc variable to bool

[David Hildenbrand]

On 02.08.19 09:18, David Hildenbrand wrote:
> On 02.08.19 01:10, Leonardo Bras wrote:
>> Changes the return variable to bool (as the return value) and
>> avoids doing a ternary operation before returning.
>>
>> Also, since rc will always be true, there is no need to do
>> rc &= bool, as (true && X) will result in X.
>>
>> Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
>> ---
>>  arch/powerpc/platforms/pseries/hotplug-memory.c | 6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> index 8e700390f3d6..392deb4855e5 100644
>> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
>> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
>> @@ -338,7 +338,7 @@ static int pseries_remove_mem_node(struct device_node *np)
>>  static bool lmb_is_removable(struct drmem_lmb *lmb)
>>  {
>>  	int i, scns_per_block;
>> -	int rc = 1;
>> +	bool rc = true;
>>  	unsigned long pfn, block_sz;
>>  	u64 phys_addr;
>>  
>> @@ -363,11 +363,11 @@ static bool lmb_is_removable(struct drmem_lmb *lmb)
>>  		if (!pfn_present(pfn))
>>  			continue;
>>  
>> -		rc &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
>> +		rc = is_mem_section_removable(pfn, PAGES_PER_SECTION);
> 
> No, that's wrong.
> 
> If is_mem_section_removable() is false in the first iteration but true
> in the last iteration, you would return true instead of false, which
> introduced a bug. We have to AND all sub-results, not simply use the
> last one.

BTW, including such subtle changes in a "Change rc variable to bool"
patch should be avoided.

-- 

Thanks,

David / dhildenb

Re: [PATCH 1/1] pseries/hotplug-memory.c: Change rc variable to bool

[Leonardo Bras]

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On Fri, 2019-08-02 at 09:23 +0200, David Hildenbrand wrote:
>  subtle changes in a "Change rc variable to bool"
> patch should be avoided.

You are right.
If it was a valid change, I should give it a patch for itself.
I will keep that in mind next time.

Thanks for helping!

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