Hi,
On Monday 16 July 2007, Jens Axboe wrote:
> Convert the main rq mapper (blk_rq_map_sg()) to the sg helper setup.
>
> Signed-off-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
> ---
> block/ll_rw_blk.c | 19 ++++++++++++-------
> 1 files changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
> index ef42bb2..ab71087 100644
> --- a/block/ll_rw_blk.c
> +++ b/block/ll_rw_blk.c
> @@ -30,6 +30,7 @@
> #include <linux/cpu.h>
> #include <linux/blktrace_api.h>
> #include <linux/fault-inject.h>
> +#include <linux/scatterlist.h>
>
> /*
> * for max sense size
> @@ -1307,9 +1308,11 @@ static int blk_hw_contig_segment(request_queue_t *q, struct bio *bio,
> * 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(request_queue_t *q, struct request *rq, struct scatterlist *sg)
> +int blk_rq_map_sg(request_queue_t *q, struct request *rq,
> + struct scatterlist *sglist)
> {
> struct bio_vec *bvec, *bvprv;
> + struct scatterlist *next_sg, *sg;
> struct bio *bio;
> int nsegs, i, cluster;
>
> @@ -1320,6 +1323,7 @@ int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg
> * for each bio in rq
> */
> bvprv = NULL;
> + sg = next_sg = &sglist[0];
> rq_for_each_bio(bio, rq) {
> /*
> * for each segment in bio
> @@ -1328,7 +1332,7 @@ int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg
> int nbytes = bvec->bv_len;
>
> if (bvprv && cluster) {
> - if (sg[nsegs - 1].length + nbytes > q->max_segment_size)
> + if (sg->length + nbytes > q->max_segment_size)
> goto new_segment;
>
> if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
> @@ -1336,14 +1340,15 @@ int blk_rq_map_sg(request_queue_t *q, struct request *rq, struct scatterlist *sg
> if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
> goto new_segment;
>
> - sg[nsegs - 1].length += nbytes;
> + sg->length += nbytes;
> } else {
> new_segment:
> - memset(&sg[nsegs],0,sizeof(struct scatterlist));
Is this intended? If so why this is no longer needed?
> - sg[nsegs].page = bvec->bv_page;
> - sg[nsegs].length = nbytes;
> - sg[nsegs].offset = bvec->bv_offset;
> + sg = next_sg;
> + next_sg = sg_next(sg);
>
> + sg->page = bvec->bv_page;
> + sg->length = nbytes;
> + sg->offset = bvec->bv_offset;
> nsegs++;
> }
> bvprv = bvec;
-
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