linux-kernel - Re: [RFC 1/2] staging: ion: shrink page-pool by page unit

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Date:	Fri, 24 Oct 2014 08:16:56 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Devendra Naga <devendranaga4@...il.com>
CC:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	gunho.lee@....com
Subject: Re: [RFC 1/2] staging: ion: shrink page-pool by page unit



2014-10-24 오전 5:36, Devendra Naga 쓴 글:
> Hello,
>
> On Thu, Oct 23, 2014 at 6:22 PM, Gioh Kim <gioh.kim@....com> wrote:
>> This patch shrink page-pool by page unit.
>>
>> Signed-off-by: Gioh Kim <gioh.kim@....com>
>> ---
>>   drivers/staging/android/ion/ion_page_pool.c   |    5 +++--
>>   drivers/staging/android/ion/ion_system_heap.c |    7 +++++--
>>   2 files changed, 8 insertions(+), 4 deletions(-)
>
>>
>
> --- cut --
>
>> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
>> index da2a63c..36e73c3 100644
>> --- a/drivers/staging/android/ion/ion_system_heap.c
>> +++ b/drivers/staging/android/ion/ion_system_heap.c
>> @@ -211,7 +211,7 @@ static int ion_system_heap_shrink(struct ion_heap *heap, gfp_t gfp_mask,
>>                                          int nr_to_scan)
>>   {
>>          struct ion_system_heap *sys_heap;
>> -       int nr_total = 0;
>> +       int nr_total = 0, nr_freed;
>>          int i;
>>
>>          sys_heap = container_of(heap, struct ion_system_heap, heap);
>> @@ -219,7 +219,10 @@ static int ion_system_heap_shrink(struct ion_heap *heap, gfp_t gfp_mask,
>>          for (i = 0; i < num_orders; i++) {
>>                  struct ion_page_pool *pool = sys_heap->pools[i];
>>
>> -               nr_total += ion_page_pool_shrink(pool, gfp_mask, nr_to_scan);
>> +               nr_freed += ion_page_pool_shrink(pool, gfp_mask, nr_to_scan);
>
> nr_freed is not initialised to zero. This might result in updating of
> a garbage value stored initially after nr_freed is created.

Yes, your're right. It's my mistake.
I testes this on my platform with custom kernel and copied codes.
I missed a line for it.
I'm sorry.

>
>> +               nr_total += nr_freed;
>> +               /* nr_to_scan can be negative */
>> +               nr_to_scan -= nr_freed;
>>          }
>>
>>          return nr_total;
>> --
>> 1.7.9.5
>>
>> --
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