[PATCH 1/3] block/blk-map.c: blk_rq_append_bio should ensure it's not appending a chain

[Jeff Garzik <jeff@garzik.org>]

Add a standard bit of list safety.  The other functions called in
blk_rq_append_bio() are written to assume only a single bio is passed to
them.  Therefore, it is an error to _ever_ pass a list to this function.

Enforce this error by ensuring the bio list is guaranteed to only append
a single list item with each blk_rq_append_bio() call.

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/block/blk-map.c b/block/blk-map.c
index f103729..a7eeac4 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -19,6 +19,7 @@ int blk_rq_append_bio(struct request_queue *q, struct request *rq,
 	else {
 		rq->biotail->bi_next = bio;
 		rq->biotail = bio;
+		bio->bi_next = NULL;
 
 		rq->data_len += bio->bi_size;
 	}