Commit adff2158 authored by Dawei Li's avatar Dawei Li Committed by Jens Axboe
Browse files

block: simplify blksize_bits() implementation 



Convert current looping-based implementation into bit operation,
which can bring improvement for:

1) bitops is more efficient for its arch-level optimization.

2) Given that blksize_bits() is inline, _if_ @size is compile-time
constant, it's possible that order_base_2() _may_ make output
compile-time evaluated, depending on code context and compiler behavior.

Signed-off-by: default avatarDawei Li <set_pte_at@outlook.com>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarChaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/TYCP286MB23238842958D7C083D6B67CECA349@TYCP286MB2323.JPNP286.PROD.OUTLOOK.COM


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 82c22947

include/linux/blkdev.h

+1 −6
Original line number Diff line number Diff line
@@ -1349,12 +1349,7 @@ static inline int blk_rq_aligned(struct request_queue *q, unsigned long addr, 
/* 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 order_base_2(size >> SECTOR_SHIFT) + SECTOR_SHIFT;

}



static inline unsigned int block_size(struct block_device *bdev)