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Commit b4b6cb61 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

Revert "block: blk-merge: try to make front segments in full size" 



This reverts commit a2d37968.

If max segment size isn't 512-aligned, this patch won't work well.

Also once multipage bvec is enabled, adjacent bvecs won't be physically
contiguous if page is added via bio_add_page(), so we don't need this
kind of complicated logic.

Reported-by: default avatarDmitry Osipenko <digetx@gmail.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 5448aca4

block/blk-merge.c

+5 −49
Original line number Diff line number Diff line
@@ -109,7 +109,6 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, 
	bool do_split = true;

	struct bio *new = NULL;

	const unsigned max_sectors = get_max_io_size(q, bio);

	unsigned advance = 0;



	bio_for_each_segment(bv, bio, iter) {

		/*
@@ -133,32 +132,12 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, 
		}



		if (bvprvp && blk_queue_cluster(q)) {

			if (seg_size + bv.bv_len > queue_max_segment_size(q))

				goto new_segment;

			if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))

				goto new_segment;

			if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))

				goto new_segment;

			if (seg_size + bv.bv_len > queue_max_segment_size(q)) {

				/*

				 * One assumption is that initial value of

				 * @seg_size(equals to bv.bv_len) won't be

				 * bigger than max segment size, but this

				 * becomes false after multipage bvecs.

				 */

				advance = queue_max_segment_size(q) - seg_size;



				if (advance > 0) {

					seg_size += advance;

					sectors += advance >> 9;

					bv.bv_len -= advance;

					bv.bv_offset += advance;

				}



				/*

				 * Still need to put remainder of current

				 * bvec into a new segment.

				 */

				goto new_segment;

			}



			seg_size += bv.bv_len;

			bvprv = bv;
@@ -180,12 +159,6 @@ static struct bio *blk_bio_segment_split(struct request_queue *q, 
		seg_size = bv.bv_len;

		sectors += bv.bv_len >> 9;



		/* restore the bvec for iterator */

		if (advance) {

			bv.bv_len += advance;

			bv.bv_offset -= advance;

			advance = 0;

		}

	}



	do_split = false;
@@ -386,29 +359,16 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 
{



	int nbytes = bvec->bv_len;

	unsigned advance = 0;



	if (*sg && *cluster) {

		if ((*sg)->length + nbytes > queue_max_segment_size(q))

			goto new_segment;



		if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))

			goto new_segment;

		if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))

			goto new_segment;



		/*

		 * try best to merge part of the bvec into previous

		 * segment and follow same policy with

		 * blk_bio_segment_split()

		 */

		if ((*sg)->length + nbytes > queue_max_segment_size(q)) {

			advance = queue_max_segment_size(q) - (*sg)->length;

			if (advance) {

				(*sg)->length += advance;

				bvec->bv_offset += advance;

				bvec->bv_len -= advance;

			}

			goto new_segment;

		}



		(*sg)->length += nbytes;

	} else {

new_segment:
@@ -431,10 +391,6 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, 


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

		(*nsegs)++;



		/* for making iterator happy */

		bvec->bv_offset -= advance;

		bvec->bv_len += advance;

	}

	*bvprv = *bvec;

}