blk-mq: initialize resid_len

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5455ed1..658428a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -353,6 +353,8 @@
 
 	trace_block_rq_issue(q, rq);
 
+	rq->resid_len = blk_rq_bytes(rq);
+
 	/*
 	 * Just mark start time and set the started bit. Due to memory
 	 * ordering, we know we'll see the correct deadline as long as