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/include/linux/bio.h b/include/linux/bio.h
index d1b04b0..9455aad 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -414,7 +414,7 @@ extern void bio_endio(struct bio *);
 
 static inline void bio_io_error(struct bio *bio)
 {
-	bio->bi_error = -EIO;
+	bio->bi_status = BLK_STS_IOERR;
 	bio_endio(bio);
 }