dm: reduce code duplication in __map_bio

Error path code (for handling DM_MAPIO_REQUEUE and DM_MAPIO_KILL) is
effectively identical.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm.c

@@ -1180,20 +1180,14 @@ static void __map_bio(struct bio *clone)
 		submit_bio_noacct(clone);
 		break;
 	case DM_MAPIO_KILL:
-		if (unlikely(swap_bios_limit(ti, clone))) {
-			struct mapped_device *md = io->md;
-			up(&md->swap_bios_semaphore);
-		}
-		free_tio(clone);
-		dm_io_dec_pending(io, BLK_STS_IOERR);
-		break;
 	case DM_MAPIO_REQUEUE:
-		if (unlikely(swap_bios_limit(ti, clone))) {
-			struct mapped_device *md = io->md;
-			up(&md->swap_bios_semaphore);
-		}
+		if (unlikely(swap_bios_limit(ti, clone)))
+			up(&io->md->swap_bios_semaphore);
 		free_tio(clone);
-		dm_io_dec_pending(io, BLK_STS_DM_REQUEUE);
+		if (r == DM_MAPIO_KILL)
+			dm_io_dec_pending(io, BLK_STS_IOERR);
+		else
+			dm_io_dec_pending(io, BLK_STS_DM_REQUEUE);
 		break;
 	default:
 		DMWARN("unimplemented target map return value: %d", r);