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SubjectRe: [PATCH] lib/scatterlist: Make sg_page_count() accessible to other modules
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On 02/13/2018 10:14 PM, Andy Shevchenko wrote:
> On Sat, Feb 10, 2018 at 8:06 PM, Alexey Skidanov
> <alexey.skidanov@intel.com> wrote:
>> Currently, sg_page_count() may be used only inside the scatterlist.c file.
>>
>> However, the same calculation is done outside of scatterlist.c file
>> causing to code duplication.
>>
>> To fix this, we move the sg_page_count() to the scatterlist.h file, making it
>> accessible to other modules.
>
> Can you provide an example of potential (or existing?) use case?
>
This one, for example - drivers/staging/android/ion/ion_heap.c:
for_each_sg(table->sgl, sg, table->nents, i) {
int npages_this_entry = PAGE_ALIGN(sg->length) / PAGE_SIZE;
struct page *page = sg_page(sg);
BUG_ON(i >= npages);
for (j = 0; j < npages_this_entry; j++)
*(tmp++) = page++;
}

One more is in the patch I have submitted for review.
>>
>> Signed-off-by: Alexey Skidanov <alexey.skidanov@intel.com>
>> ---
>> include/linux/scatterlist.h | 5 +++++
>> lib/scatterlist.c | 5 -----
>> 2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
>> index b7c8325..fe28148 100644
>> --- a/include/linux/scatterlist.h
>> +++ b/include/linux/scatterlist.h
>> @@ -248,6 +248,11 @@ static inline void *sg_virt(struct scatterlist *sg)
>> return page_address(sg_page(sg)) + sg->offset;
>> }
>>
>> +static inline int sg_page_count(struct scatterlist *sg)
>> +{
>> + return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
>> +}
>> +
>> int sg_nents(struct scatterlist *sg);
>> int sg_nents_for_len(struct scatterlist *sg, u64 len);
>> struct scatterlist *sg_next(struct scatterlist *);
>> diff --git a/lib/scatterlist.c b/lib/scatterlist.c
>> index 7c1c55f..4a59131 100644
>> --- a/lib/scatterlist.c
>> +++ b/lib/scatterlist.c
>> @@ -486,11 +486,6 @@ void __sg_page_iter_start(struct sg_page_iter *piter,
>> }
>> EXPORT_SYMBOL(__sg_page_iter_start);
>>
>> -static int sg_page_count(struct scatterlist *sg)
>> -{
>> - return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
>> -}
>> -
>> bool __sg_page_iter_next(struct sg_page_iter *piter)
>> {
>> if (!piter->__nents || !piter->sg)
>> --
>> 2.7.4
>>
>
>
>

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