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Commit 48d7727c authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

block: optimize __blk_segment_map_sg() for single-page bvec 



Introduce a fast path for single-page bvec IO, then blk_bvec_map_sg()
can be avoided.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 4d633062

block/blk-merge.c

+7 −2
Original line number Diff line number Diff line
@@ -447,7 +447,7 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 
	return biovec_phys_mergeable(q, &end_bv, &nxt_bv);

}



static struct scatterlist *blk_next_sg(struct scatterlist **sg,

static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,

		struct scatterlist *sglist)

{

	if (!*sg)
@@ -512,6 +512,11 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 
		(*sg)->length += nbytes;

	} else {

new_segment:

		if (bvec->bv_offset + bvec->bv_len <= PAGE_SIZE) {

			*sg = blk_next_sg(sg, sglist);

			sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);

			(*nsegs) += 1;

		} else

			(*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg);

	}

	*bvprv = *bvec;