[PATCH] Fix to return wrong pointer in slob

[PATCH] Fix to return wrong pointer in slob

[MinChan Kim]

Although slob_alloc return NULL, __kmalloc_node returns NULL + align.
Because align always can be changed, it is very hard for debugging
problem of no page if it don't return NULL.

We have to return NULL in case of no page.

Signed-off-by: MinChan Kim <minchan.kim@gmail.com>
---
 mm/slob.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/slob.c b/mm/slob.c
index 6038cba..258d76d 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -469,9 +469,12 @@ void *__kmalloc_node(size_t size, gfp_t gfp, int node)
 			return ZERO_SIZE_PTR;
 
 		m = slob_alloc(size + align, gfp, align, node);
-		if (m)
-			*m = size;
-		return (void *)m + align;
+		if (!m)
+			return NULL;
+		else {
+			*m = size; 
+			return (void *)m + align;
+		}
 	} else {
 		void *ret;
 
-- 
1.5.4.3

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Re: [PATCH] Fix to return wrong pointer in slob

[Matt Mackall]

On Mon, 2008-05-19 at 22:12 +0900, MinChan Kim wrote:
> Although slob_alloc return NULL, __kmalloc_node returns NULL + align.
> Because align always can be changed, it is very hard for debugging
> problem of no page if it don't return NULL.
> 
> We have to return NULL in case of no page.
> 
> Signed-off-by: MinChan Kim <minchan.kim@gmail.com>
> ---
>  mm/slob.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/slob.c b/mm/slob.c
> index 6038cba..258d76d 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -469,9 +469,12 @@ void *__kmalloc_node(size_t size, gfp_t gfp, int node)
>  			return ZERO_SIZE_PTR;
>  
>  		m = slob_alloc(size + align, gfp, align, node);
> -		if (m)
> -			*m = size;
> -		return (void *)m + align;
> +		if (!m)
> +			return NULL;
> +		else {
> +			*m = size; 
> +			return (void *)m + align;
> +		}

This looks good, but I would remove the 'else {' and '}' here. It's nice
to have the 'normal path' minimally indented.

Otherwise,

Acked-by: Matt Mackall <mpm@selenic.com>

[cc:ed to Pekka, who manages the allocator tree]

>  	} else {
>  		void *ret;
>  
-- 
Mathematics is the supreme nostalgia of our time.

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Re: [PATCH] Fix to return wrong pointer in slob

[Pekka Enberg]

Matt Mackall wrote:
> This looks good, but I would remove the 'else {' and '}' here. It's nice
> to have the 'normal path' minimally indented.
> 
> Otherwise,
> 
> Acked-by: Matt Mackall <mpm@selenic.com>
> 
> [cc:ed to Pekka, who manages the allocator tree]

Applied, thanks!

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Re: [PATCH] Fix to return wrong pointer in slob

[MinChan Kim]

On Tue, May 20, 2008 at 2:40 AM, Matt Mackall <mpm@selenic.com> wrote:
>
> On Mon, 2008-05-19 at 22:12 +0900, MinChan Kim wrote:
>> Although slob_alloc return NULL, __kmalloc_node returns NULL + align.
>> Because align always can be changed, it is very hard for debugging
>> problem of no page if it don't return NULL.
>>
>> We have to return NULL in case of no page.
>>
>> Signed-off-by: MinChan Kim <minchan.kim@gmail.com>
>> ---
>>  mm/slob.c |    9 ++++++---
>>  1 files changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/slob.c b/mm/slob.c
>> index 6038cba..258d76d 100644
>> --- a/mm/slob.c
>> +++ b/mm/slob.c
>> @@ -469,9 +469,12 @@ void *__kmalloc_node(size_t size, gfp_t gfp, int node)
>>                       return ZERO_SIZE_PTR;
>>
>>               m = slob_alloc(size + align, gfp, align, node);
>> -             if (m)
>> -                     *m = size;
>> -             return (void *)m + align;
>> +             if (!m)
>> +                     return NULL;
>> +             else {
>> +                     *m = size;
>> +                     return (void *)m + align;
>> +             }
>
> This looks good, but I would remove the 'else {' and '}' here. It's nice
> to have the 'normal path' minimally indented.

I agree
Thanks, Matt :)


-- 
Thanks,
MinChan Kim

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