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Commit 6a501bf0 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
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blk-merge: compute bio->bi_seg_front_size efficiently 



It is enough to check and compute bio->bi_seg_front_size just
after the 1st segment is found, but current code checks that
for each bvec, which is inefficient.

This patch follows the way in  __blk_recalc_rq_segments()
for computing bio->bi_seg_front_size, and it is more efficient
and code becomes more readable too.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 92681eca

block/blk-merge.c

+5 −4
Original line number Diff line number Diff line
@@ -146,22 +146,21 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, 
			bvprvp = &bvprv;

			sectors += bv.bv_len >> 9;



			if (nsegs == 1 && seg_size > front_seg_size)

				front_seg_size = seg_size;

			continue;

		}

new_segment:

		if (nsegs == queue_max_segments(q))

			goto split;



		if (nsegs == 1 && seg_size > front_seg_size)

			front_seg_size = seg_size;



		nsegs++;

		bvprv = bv;

		bvprvp = &bvprv;

		seg_size = bv.bv_len;

		sectors += bv.bv_len >> 9;



		if (nsegs == 1 && seg_size > front_seg_size)

			front_seg_size = seg_size;

	}



	do_split = false;
@@ -174,6 +173,8 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, 
			bio = new;

	}



	if (nsegs == 1 && seg_size > front_seg_size)

		front_seg_size = seg_size;

	bio->bi_seg_front_size = front_seg_size;

	if (seg_size > bio->bi_seg_back_size)

		bio->bi_seg_back_size = seg_size;