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-flakey.c b/drivers/md/dm-flakey.c
index 13305a1..e8f093b 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -321,7 +321,7 @@ static int flakey_map(struct dm_target *ti, struct bio *bio)
 		if (bio_data_dir(bio) == READ) {
 			if (!fc->corrupt_bio_byte && !test_bit(DROP_WRITES, &fc->flags) &&
 			    !test_bit(ERROR_WRITES, &fc->flags))
-				return -EIO;
+				return DM_MAPIO_KILL;
 			goto map_bio;
 		}
 
@@ -349,7 +349,7 @@ static int flakey_map(struct dm_target *ti, struct bio *bio)
 		/*
 		 * By default, error all I/O.
 		 */
-		return -EIO;
+		return DM_MAPIO_KILL;
 	}
 
 map_bio: