block: switch bios to blk_status_t

Replace bi_error with a new bi_status to allow for a clear conversion.
Note that device mapper overloaded bi_error with a private value, which
we'll have to keep arround at least for now and thus propagate to a
proper blk_status_t value.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 4c00bc2..3ed6a0d 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -572,7 +572,7 @@
 	struct r5l_log *log = io->log;
 	unsigned long flags;
 
-	if (bio->bi_error)
+	if (bio->bi_status)
 		md_error(log->rdev->mddev, log->rdev);
 
 	bio_put(bio);
@@ -1247,7 +1247,7 @@
 	unsigned long flags;
 	struct r5l_io_unit *io;
 
-	if (bio->bi_error)
+	if (bio->bi_status)
 		md_error(log->rdev->mddev, log->rdev);
 
 	spin_lock_irqsave(&log->io_list_lock, flags);