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SubjectRe: [PATCH v2] blkdev: Replace blksize_bits() with ilog2()
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On 2020-05-29 13:27, Matthew Wilcox wrote:
> On Fri, May 29, 2020 at 10:11:00PM +0800, Kaitao Cheng wrote:
>> There is a function named ilog2() exist which can replace blksize.
>> The generated code will be shorter and more efficient on some
>> architecture, such as arm64. And ilog2() can be optimized according
>> to different architecture.
>
> We'd get the same benefit from a smaller patch with just:
>
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1502,15 +1502,9 @@ static inline int blk_rq_aligned(struct request_queue *q, unsigned long addr,
> return !(addr & alignment) && !(len & alignment);
> }
>
> -/* assumes size > 256 */
> static inline unsigned int blksize_bits(unsigned int size)
> {
> - unsigned int bits = 8;
> - do {
> - bits++;
> - size >>= 1;
> - } while (size > 256);
> - return bits;
> + return ilog2(size);
> }
>
> static inline unsigned int block_size(struct block_device *bdev)

Hi Matthew,

I had suggested to change all blksize_bits() calls into ilog2() calls
because I think that a single function to calculate the logarithm base 2
is sufficient.

Thanks,

Bart.


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