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Commit 85b9f66a authored by Asias He's avatar Asias He Committed by Jens Axboe
Browse files

block: Add blk_bio_map_sg() helper 



Add a helper to map a bio to a scatterlist, modelled after
blk_rq_map_sg.

This helper is useful for any driver that wants to create
a scatterlist from its ->make_request_fn method.

Changes in v2:
 - Use __blk_segment_map_sg to avoid duplicated code
 - Add cocbook style function comment

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
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Signed-off-by: default avatarAsias He <asias@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 963ab9e5

block/blk-merge.c

+37 −0
Original line number Diff line number Diff line
@@ -209,6 +209,43 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, 
}

EXPORT_SYMBOL(blk_rq_map_sg);



/**

 * blk_bio_map_sg - map a bio to a scatterlist

 * @q: request_queue in question

 * @bio: bio being mapped

 * @sglist: scatterlist being mapped

 *

 * Note:

 *    Caller must make sure sg can hold bio->bi_phys_segments entries

 *

 * Will return the number of sg entries setup

 */

int blk_bio_map_sg(struct request_queue *q, struct bio *bio,

		   struct scatterlist *sglist)

{

	struct bio_vec *bvec, *bvprv;

	struct scatterlist *sg;

	int nsegs, cluster;

	unsigned long i;



	nsegs = 0;

	cluster = blk_queue_cluster(q);



	bvprv = NULL;

	sg = NULL;

	bio_for_each_segment(bvec, bio, i) {

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

				     &nsegs, &cluster);

	} /* segments in bio */



	if (sg)

		sg_mark_end(sg);



	BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);

	return nsegs;

}

EXPORT_SYMBOL(blk_bio_map_sg);



static inline int ll_new_hw_segment(struct request_queue *q,

				    struct request *req,

				    struct bio *bio)

include/linux/blkdev.h

+2 −0
Original line number Diff line number Diff line
@@ -894,6 +894,8 @@ extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable); 
extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);



extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);

extern int blk_bio_map_sg(struct request_queue *q, struct bio *bio,

			  struct scatterlist *sglist);

extern void blk_dump_rq_flags(struct request *, char *);

extern long nr_blockdev_pages(void);