block: convert to using sg helpers

Convert the main rq mapper (blk_rq_map_sg()) to the sg helper setup.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 4df7d027eb06..36d205128f9a 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
@@ -1318,9 +1319,10 @@ static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio,
  * 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 *sg)
+                  struct scatterlist *sglist)
 {
         struct bio_vec *bvec, *bvprv;
+        struct scatterlist *next_sg, *sg;
         struct req_iterator iter;
         int nsegs, cluster;
 
@@ -1331,11 +1333,12 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
          * for each bio in rq
          */
         bvprv = NULL;
+        sg = next_sg = &sglist[0];
         rq_for_each_segment(bvec, rq, iter) {
                 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))
@@ -1343,14 +1346,15 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
                         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));
-                        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;