constify blk_rq_map_user_iov() and friends

sg_iovec array passed to it can be const
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

block/blk-map.c

@@ -188,7 +188,7 @@ EXPORT_SYMBOL(blk_rq_map_user);
  *    unmapping.
  */
 int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
-			struct rq_map_data *map_data, struct sg_iovec *iov,
+			struct rq_map_data *map_data, const struct sg_iovec *iov,
 			int iov_count, unsigned int len, gfp_t gfp_mask)
 {
 	struct bio *bio;

fs/bio.c

@@ -1003,7 +1003,7 @@ struct bio_map_data {
 };
 
 static void bio_set_map_data(struct bio_map_data *bmd, struct bio *bio,
-			     struct sg_iovec *iov, int iov_count,
+			     const struct sg_iovec *iov, int iov_count,
 			     int is_our_pages)
 {
 	memcpy(bmd->sgvecs, iov, sizeof(struct sg_iovec) * iov_count);
@@ -1023,7 +1023,7 @@ static struct bio_map_data *bio_alloc_map_data(int nr_segs,
 		       sizeof(struct sg_iovec) * iov_count, gfp_mask);
 }
 
-static int __bio_copy_iov(struct bio *bio, struct sg_iovec *iov, int iov_count,
+static int __bio_copy_iov(struct bio *bio, const struct sg_iovec *iov, int iov_count,
 			  int to_user, int from_user, int do_free_page)
 {
 	int ret = 0, i;
@@ -1121,7 +1121,7 @@ EXPORT_SYMBOL(bio_uncopy_user);
  */
 struct bio *bio_copy_user_iov(struct request_queue *q,
 			      struct rq_map_data *map_data,
-			      struct sg_iovec *iov, int iov_count,
+			      const struct sg_iovec *iov, int iov_count,
 			      int write_to_vm, gfp_t gfp_mask)
 {
 	struct bio_map_data *bmd;
@@ -1260,7 +1260,7 @@ EXPORT_SYMBOL(bio_copy_user);
 
 static struct bio *__bio_map_user_iov(struct request_queue *q,
 				      struct block_device *bdev,
-				      struct sg_iovec *iov, int iov_count,
+				      const struct sg_iovec *iov, int iov_count,
 				      int write_to_vm, gfp_t gfp_mask)
 {
 	int i, j;
@@ -1408,7 +1408,7 @@ EXPORT_SYMBOL(bio_map_user);
  *	device. Returns an error pointer in case of error.
  */
 struct bio *bio_map_user_iov(struct request_queue *q, struct block_device *bdev,
-			     struct sg_iovec *iov, int iov_count,
+			     const struct sg_iovec *iov, int iov_count,
 			     int write_to_vm, gfp_t gfp_mask)
 {
 	struct bio *bio;

include/linux/bio.h

@@ -388,7 +388,7 @@ struct sg_iovec;
 struct rq_map_data;
 extern struct bio *bio_map_user_iov(struct request_queue *,
 				    struct block_device *,
-				    struct sg_iovec *, int, int, gfp_t);
+				    const struct sg_iovec *, int, int, gfp_t);
 extern void bio_unmap_user(struct bio *);
 extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
 				gfp_t);
@@ -414,7 +414,8 @@ extern int bio_alloc_pages(struct bio *bio, gfp_t gfp);
 extern struct bio *bio_copy_user(struct request_queue *, struct rq_map_data *,
 				 unsigned long, unsigned int, int, gfp_t);
 extern struct bio *bio_copy_user_iov(struct request_queue *,
-				     struct rq_map_data *, struct sg_iovec *,
+				     struct rq_map_data *,
+				     const struct sg_iovec *,
 				     int, int, gfp_t);
 extern int bio_uncopy_user(struct bio *);
 void zero_fill_bio(struct bio *bio);

include/linux/blkdev.h

@@ -823,8 +823,8 @@ extern int blk_rq_map_user(struct request_queue *, struct request *,
 extern int blk_rq_unmap_user(struct bio *);
 extern int blk_rq_map_kern(struct request_queue *, struct request *, void *, unsigned int, gfp_t);
 extern int blk_rq_map_user_iov(struct request_queue *, struct request *,
-			       struct rq_map_data *, struct sg_iovec *, int,
-			       unsigned int, gfp_t);
+			       struct rq_map_data *, const struct sg_iovec *,
+			       int, unsigned int, gfp_t);
 extern int blk_execute_rq(struct request_queue *, struct gendisk *,
 			  struct request *, int);
 extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,