Commit 963ab9e5 authored by Asias He's avatar Asias He Committed by Jens Axboe
Browse files

block: Introduce __blk_segment_map_sg() helper 



Split the mapping code in blk_rq_map_sg() to a helper
__blk_segment_map_sg(), so that other mapping function, e.g.
blk_bio_map_sg(), can share the code.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Suggested-by: default avatarJens Axboe <axboe@kernel.dk>
Suggested-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarAsias He <asias@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 53362a05

block/blk-merge.c

+45 −35
Original line number Diff line number Diff line
@@ -110,43 +110,28 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, 
	return 0;

}



/*

 * map a request to scatterlist, return number of sg entries setup. Caller

 * must make sure sg can hold rq->nr_phys_segments entries

 */

int blk_rq_map_sg(struct request_queue *q, struct request *rq,

		  struct scatterlist *sglist)

static void

__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,

		     struct scatterlist *sglist, struct bio_vec **bvprv,

		     struct scatterlist **sg, int *nsegs, int *cluster)

{

	struct bio_vec *bvec, *bvprv;

	struct req_iterator iter;

	struct scatterlist *sg;

	int nsegs, cluster;



	nsegs = 0;

	cluster = blk_queue_cluster(q);



	/*

	 * for each bio in rq

	 */

	bvprv = NULL;

	sg = NULL;

	rq_for_each_segment(bvec, rq, iter) {

	int nbytes = bvec->bv_len;



		if (bvprv && cluster) {

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

	if (*bvprv && *cluster) {

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

			goto new_segment;



			if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))

		if (!BIOVEC_PHYS_MERGEABLE(*bvprv, bvec))

			goto new_segment;

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

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

			goto new_segment;



			sg->length += nbytes;

		(*sg)->length += nbytes;

	} else {

new_segment:

			if (!sg)

				sg = sglist;

		if (!*sg)

			*sg = sglist;

		else {

			/*

			 * If the driver previously mapped a shorter
@@ -158,14 +143,39 @@ new_segment: 
			 * termination bit to avoid doing a full

			 * sg_init_table() in drivers for each command.

			 */

				sg->page_link &= ~0x02;

				sg = sg_next(sg);

			(*sg)->page_link &= ~0x02;

			*sg = sg_next(*sg);

		}



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

			nsegs++;

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

		(*nsegs)++;

	}

	*bvprv = bvec;

}

		bvprv = bvec;



/*

 * map a request to scatterlist, return number of sg entries setup. Caller

 * must make sure sg can hold rq->nr_phys_segments entries

 */

int blk_rq_map_sg(struct request_queue *q, struct request *rq,

		  struct scatterlist *sglist)

{

	struct bio_vec *bvec, *bvprv;

	struct req_iterator iter;

	struct scatterlist *sg;

	int nsegs, cluster;



	nsegs = 0;

	cluster = blk_queue_cluster(q);



	/*

	 * for each bio in rq

	 */

	bvprv = NULL;

	sg = NULL;

	rq_for_each_segment(bvec, rq, iter) {

		__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,

				     &nsegs, &cluster);

	} /* segments in rq */

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