dm: don't return errnos from ->map

Instead use the special DM_MAPIO_KILL return value to return -EIO just
like we do for the request based path.  Note that dm-log-writes returned
-ENOMEM in a few places, which now becomes -EIO instead.  No consumer
treats -ENOMEM special so this shouldn't be an issue (and it should
use a mempool to start with to make guaranteed progress).

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/dm-target.c b/drivers/md/dm-target.c
index b242b75..c0d7e60 100644
--- a/drivers/md/dm-target.c
+++ b/drivers/md/dm-target.c
@@ -128,7 +128,7 @@ static void io_err_dtr(struct dm_target *tt)
 
 static int io_err_map(struct dm_target *tt, struct bio *bio)
 {
-	return -EIO;
+	return DM_MAPIO_KILL;
 }
 
 static int io_err_clone_and_map_rq(struct dm_target *ti, struct request *rq,