dm: introduce a new DM_MAPIO_KILL return value

This untangles the DM_MAPIO_* values returned from ->clone_and_map_rq
from the error codes used by the block layer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index 43d3445..6264ff0 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -135,7 +135,7 @@ static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,
 				   union map_info *map_context,
 				   struct request **clone)
 {
-	return -EIO;
+	return DM_MAPIO_KILL;
 }
 
 static void io_err_release_clone_rq(struct request *clone)