RDS: limit the number of times we loop in rds_send_xmit

This will kick the RDS worker thread if we have been looping
too long.

Original commit from 2012 updated to include a change by
Venkat Venkatsubra <[e-mail]>
that triggers "must_wake" if "rds_ib_recv_refill_one" fails.

Signed-off-by: Gerd Rausch <[e-mail]>
Acked-by: Santosh Shilimkar <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/rds/ib_recv.c

···
 	unsigned int posted = 0;
 	int ret = 0;
 	bool can_wait = !!(gfp & __GFP_DIRECT_RECLAIM);
+	bool must_wake = false;
 	u32 pos;
 
 	/* the goal here is to just make sure that someone, somewhere
···
 		recv = &ic->i_recvs[pos];
 		ret = rds_ib_recv_refill_one(conn, recv, gfp);
 		if (ret) {
+			must_wake = true;
 			break;
 		}
 
···
 		}
 
 		posted++;
+
+		if ((posted > 128 && need_resched()) || posted > 8192) {
+			must_wake = true;
+			break;
+		}
 	}
 
 	/* We're doing flow control - update the window. */
···
 	 * if we should requeue.
 	 */
 	if (rds_conn_up(conn) &&
-	    ((can_wait && rds_ib_ring_low(&ic->i_recv_ring)) ||
+	    (must_wake ||
+	    (can_wait && rds_ib_ring_low(&ic->i_recv_ring)) ||
 	    rds_ib_ring_empty(&ic->i_recv_ring))) {
 		queue_delayed_work(rds_wq, &conn->c_recv_w, 1);
 	}
+	if (can_wait)
+		cond_resched();
 }
 
 /*