block: reuse __blk_bvec_map_sg() for mapping page sized bvec

Inside __blk_segment_map_sg(), page sized bvec mapping is optimized
a bit with one standalone branch.

So reuse __blk_bvec_map_sg() to do that.

Cc: Omar Sandoval <osandov@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

block/blk-merge.c

@@ -493,6 +493,14 @@ static unsigned blk_bvec_map_sg(struct request_queue *q,
 	return nsegs;
 }
 
+static inline int __blk_bvec_map_sg(struct bio_vec bv,
+		struct scatterlist *sglist, struct scatterlist **sg)
+{
+	*sg = blk_next_sg(sg, sglist);
+	sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
+	return 1;
+}
+
 static inline void
 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 		     struct scatterlist *sglist, struct bio_vec *bvprv,
@@ -511,23 +519,13 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
 	} else {
 new_segment:
 		if (bvec->bv_offset + bvec->bv_len <= PAGE_SIZE) {
-			*sg = blk_next_sg(sg, sglist);
-			sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
-			(*nsegs) += 1;
+			(*nsegs) += __blk_bvec_map_sg(*bvec, sglist, sg);
 		} else
 			(*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg);
 	}
 	*bvprv = *bvec;
 }
 
-static inline int __blk_bvec_map_sg(struct bio_vec bv,
-		struct scatterlist *sglist, struct scatterlist **sg)
-{
-	*sg = sglist;
-	sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
-	return 1;
-}
-
 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
 			     struct scatterlist *sglist,
 			     struct scatterlist **sg)