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>

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index 4df7d027eb06d934adc1493205d11d6c2f7ad203..36d205128f9a969a45d81b245f85842c117a4fb5 100644 (file)
--- 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;