Enhanced partition statistics: update partition statitics

Updates the enhanced partition statistics in generic block layer
besides the disk statistics.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 845ef81..d3b84bb 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -454,8 +454,14 @@
 	elv_merge_requests(q, req, next);
 
 	if (req->rq_disk) {
+		struct hd_struct *part
+			= get_part(req->rq_disk, req->sector);
 		disk_round_stats(req->rq_disk);
 		req->rq_disk->in_flight--;
+		if (part) {
+			part_round_stats(part);
+			part->in_flight--;
+		}
 	}
 
 	req->ioprio = ioprio_best(req->ioprio, next->ioprio);