block: misc updates

This patch makes the following misc updates in preparation for
disk->part dereference fix and extended block devt support.

* implment part_to_disk()

* fix comment about gendisk->part indexing

* rename get_part() to disk_map_sector()

* don't use n which is always zero while printing disk information in
  diskstats_show()

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index d81d91419ff5..9b17da698d7c 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -387,8 +387,8 @@ static int attempt_merge(struct request_queue *q, struct request *req,
         elv_merge_requests(q, req, next);
 
         if (req->rq_disk) {
-                struct hd_struct *part
-                        = get_part(req->rq_disk, req->sector);
+                struct hd_struct *part =
+                        disk_map_sector(req->rq_disk, req->sector);
                 disk_round_stats(req->rq_disk);
                 req->rq_disk->in_flight--;
                 if (part) {