Re: [PATCH] mm: cma: add functions to get region pages counters

[Stefan Strogin]

Hello Andrew,

On 04/04/15 00:58, Andrew Morton wrote:
> On Fri, 03 Apr 2015 15:42:40 +0300 Stefan Strogin <stefan.strogin@xxxxxxxxx> wrote:
> 
>> From: Dmitry Safonov <d.safonov@xxxxxxxxxxxxxxxxxxx>
>>
>> Here are two functions that provide interface to compute/get used size
>> and size of biggest free chunk in cma region. Add that information to debugfs.
>>
>> ...
>>
>> --- a/mm/cma.c
>> +++ b/mm/cma.c
>> @@ -53,6 +53,36 @@ unsigned long cma_get_size(const struct cma *cma)
>>  	return cma->count << PAGE_SHIFT;
>>  }
>>  
>> +unsigned long cma_get_used(struct cma *cma)
>> +{
>> +	unsigned long ret = 0;
>> +
>> +	mutex_lock(&cma->lock);
>> +	/* pages counter is smaller than sizeof(int) */
>> +	ret = bitmap_weight(cma->bitmap, (int)cma->count);
>> +	mutex_unlock(&cma->lock);
>> +
>> +	return ret << cma->order_per_bit;
>> +}
>> +
>> +unsigned long cma_get_maxchunk(struct cma *cma)
>> +{
>> +	unsigned long maxchunk = 0;
>> +	unsigned long start, end = 0;
>> +
>> +	mutex_lock(&cma->lock);
>> +	for (;;) {
>> +		start = find_next_zero_bit(cma->bitmap, cma->count, end);
>> +		if (start >= cma->count)
>> +			break;
>> +		end = find_next_bit(cma->bitmap, cma->count, start);
>> +		maxchunk = max(end - start, maxchunk);
>> +	}
>> +	mutex_unlock(&cma->lock);
>> +
>> +	return maxchunk << cma->order_per_bit;
>> +}
> 
> This will cause unused code to be included in cma.o when
> CONFIG_CMA_DEBUGFS=n.  Please review the below patch which moves it all
> into cma_debug.c
> 

Thank you very much for the reply and for the patches.

>> --- a/mm/cma_debug.c
>> +++ b/mm/cma_debug.c
>> @@ -33,6 +33,28 @@ static int cma_debugfs_get(void *data, u64 *val)
>>  
>>  DEFINE_SIMPLE_ATTRIBUTE(cma_debugfs_fops, cma_debugfs_get, NULL, "%llu\n");
>>  
>> +static int cma_used_get(void *data, u64 *val)
>> +{
>> +	struct cma *cma = data;
>> +
>> +	*val = cma_get_used(cma);
>> +
>> +	return 0;
>> +}
> 
> We have cma_used_get() and cma_get_used().  Confusing!  Can we think of
> better names for one or both of them?
> 

Oh. Excuse me for the bad code.
Wouldn't it be better to merge cma_get_used() and cma_get_maxchunk()
into cma_*_get() as they aren't used anywhere else?
Please see the following patch.
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