IB: Clarify the documentation of ib_post_send()

Clarify the behavior of ib_post_send() when a list of work requests is
passed in and an immediate error is returned.

Signed-off-by: Bart Van Assche <bart.vanassche@gmail.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

include/rdma/ib_verbs.h

@@ -1425,6 +1425,11 @@ int ib_destroy_qp(struct ib_qp *qp);
  * @send_wr: A list of work requests to post on the send queue.
  * @bad_send_wr: On an immediate failure, this parameter will reference
  *   the work request that failed to be posted on the QP.
+ *
+ * While IBA Vol. 1 section 11.4.1.1 specifies that if an immediate
+ * error is returned, the QP state shall not be affected,
+ * ib_post_send() will return an immediate error after queueing any
+ * earlier work requests in the list.
  */
 static inline int ib_post_send(struct ib_qp *qp,
 			       struct ib_send_wr *send_wr,