dm: dont rewrite dm_disk(md)->part0.in_flight

generic_start_io_acct and generic_end_io_acct already update the variable
in_flight using atomic operations, so we don't have to overwrite them
again.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm.c

@@ -663,8 +663,7 @@ static void start_io_acct(struct dm_io *io)
 	generic_start_io_acct(md->queue, bio_op(bio), bio_sectors(bio),
 			      &dm_disk(md)->part0);
 
-	atomic_set(&dm_disk(md)->part0.in_flight[rw],
-		   atomic_inc_return(&md->pending[rw]));
+	atomic_inc(&md->pending[rw]);
 
 	if (unlikely(dm_stats_used(&md->stats)))
 		dm_stats_account_io(&md->stats, bio_data_dir(bio),
@@ -693,7 +692,6 @@ static void end_io_acct(struct dm_io *io)
 	 * a flush.
 	 */
 	pending = atomic_dec_return(&md->pending[rw]);
-	atomic_set(&dm_disk(md)->part0.in_flight[rw], pending);
 	pending += atomic_read(&md->pending[rw^0x1]);
 
 	/* nudge anyone waiting on suspend queue */