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Message-Id: <1456836718-11509-1-git-send-email-ming.lei@canonical.com> Date: Tue, 1 Mar 2016 20:51:58 +0800 From: Ming Lei <ming.lei@...onical.com> To: Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org Cc: linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>, Ming Lei <ming.lei@...onical.com> Subject: [PATCH] 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: Ming Lei <ming.lei@...onical.com> --- block/blk-merge.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/blk-merge.c b/block/blk-merge.c index 2613531..e4c74a0 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -131,22 +131,21 @@ 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; @@ -159,6 +158,8 @@ split: 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; -- 1.9.1
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