RDS: Perform unmapping ops in stages

Previously, RDS would wait until the final send WR had completed
and then handle cleanup. With silent ops, we do not know
if an atomic, rdma, or data op will be last. This patch
handles any of these cases by keeping a pointer to the last
op in the message in m_last_op.

When the TX completion event fires, rds dispatches to per-op-type
cleanup functions, and then does whole-message cleanup, if the
last op equalled m_last_op.

This patch also moves towards having op-specific functions take
the op struct, instead of the overall rm struct.

rds_ib_connection has a pointer to keep track of a a partially-
completed data send operation. This patch changes it from an
rds_message pointer to the narrower rm_data_op pointer, and
modifies places that use this pointer as needed.

Signed-off-by: Andy Grover <andy.grover@oracle.com>
diff --git a/net/rds/ib.h b/net/rds/ib.h
index d64b508..202140a 100644
--- a/net/rds/ib.h
+++ b/net/rds/ib.h
@@ -53,8 +53,7 @@
 };
 
 struct rds_ib_send_work {
-	struct rds_message	*s_rm;
-	struct rm_rdma_op	*s_op;
+	void			*s_op;
 	struct ib_send_wr	s_wr;
 	struct ib_sge		s_sge[RDS_IB_MAX_SGE];
 	unsigned long		s_queued;
@@ -92,7 +91,7 @@
 
 	/* tx */
 	struct rds_ib_work_ring	i_send_ring;
-	struct rds_message	*i_rm;
+	struct rm_data_op	*i_data_op;
 	struct rds_header	*i_send_hdrs;
 	u64			i_send_hdrs_dma;
 	struct rds_ib_send_work *i_sends;
@@ -336,7 +335,7 @@
 void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted);
 int rds_ib_send_grab_credits(struct rds_ib_connection *ic, u32 wanted,
 			     u32 *adv_credits, int need_posted, int max_posted);
-int rds_ib_xmit_atomic(struct rds_connection *conn, struct rds_message *rm);
+int rds_ib_xmit_atomic(struct rds_connection *conn, struct rm_atomic_op *op);
 
 /* ib_stats.c */
 DECLARE_PER_CPU(struct rds_ib_statistics, rds_ib_stats);